Symposium Organizers
Moonsub Shim University of Illinois, Urbana-Champaign
Masaru Kuno University of Notre Dame
Xiao-Min Lin Argonne National Laboratory
Ruth Pachter Air Force Research Laboratory
Sanat Kumar Rensselaer Polytechnic Institute
DD1/EE1: Joint Session: Synthesis of Nanotubes and Nanowires
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
9:00 AM - DD1.1/EE1.1
Controlling Growth of Carbon Nanotubes for Devices
John Robertson 1 , Stephan Hofmann 1 , Mirco Cantoro 1 , Guofang Zhong 1
1 Engineering, Cambridge University, Cambridge United Kingdom
Show AbstractCarbon nanotubes have unique properties which may lead to their use in high performance electronic devices such as vias, interconnects and FETs. However, these applications require a much better control of the growth process than presently exists. For Vias formed by a bunch of multi-walled nanotubes, the effective resistance must be reduced to 10 ohms. Unless the contact resistance is very low, this requires growth of very closely spaced MWNTs. MWNTs grown by PECVD or CVD are typically grown from a Ni or Fe which has been restructured into a nano-particle from which the nanotube nucleates. But this tends to restrict the site density. On the other hand, FETs require use of only semiconducting single wall nanotubes, which in effect requires some chiral selection, or post-growth separation, which is uneconomic. Both applications place temperature limits on the growth process. We have shown by recent work an improved understanding of the growth process which helps in each of these aspects, such as the ability to grow SNWTs at only 350C by purely thermal CVD [2], and the highest nucleation density and catalyst efficiency of vertically aligned SWNT mats [3].1 S Hofmann, et al, App Phys Lett 83 135 (2003); J App Phys 98 034308 (2005)2 M Cantoro et al, Nanolett 6 1107 (2006)3 G Zhong et al, Carbon 44 2009 (2006)
Monday PM, April 09, 2007
Room 2003 (Moscone West)
9:00 AM - **DD2.1
Origin of Molecular Stability and Magnetism Revealed by the Complete Solution of Many-electron Schroedinger Equation.
Yoshiyuki Kawazoe 1 , Kenta Hongo 1 , Takayuki Oyamada 1 , Yohei Maruyama 1 , Hiroshi Yasuhara 1
1 Institute for Materials Research, Tohoku University, Sendai Japan
Show AbstractBased on the present supercomputer power, it is becoming possible to solve the many-body quantum mechanical equation exactly including exchange-correlation potentials. Recently we have revealed that the origin of the molecular stability and magnetism have completely been misunderstood in most of the standard textbooks. (1)Hund found his empirical rule on the maximum ground state spin state in 1925. After this interesting finding many researchers had tried to understand the reason and Slater explained this rule in 1929 by a perturbative approach based on the electron exchange. In most of the textbooks today still use this traditional explanation. However, Slater’s explanation has been doubted theoretically by Davidson, Boyd, and other researchers by using Hartree-Fock level and better approximations. We have solved the many-body Shroedinger equation exactly with diffusion quantum Monte Carlo method (DQMC) and finally confirmed that the traditional Slater’s explanation is invalid. The exact reason of the Hund’s multiplicity rule is that the energy gain for maximum spin state is realized mainly by the electron-nucleus attractive interaction. (2)Another impact of this study is that we clarify the fundamental reason of stability of materials. When atoms gather to form molecules or crystals, energy gain is only achieved by the nucleus-electron attractive force, and electrons come closer to nucleus, the potential energy decreases, and the kinetic energy increases to realize stability of materials. This result proves that the Heitler-London model is invalid, where kinetic energy decreases when molecule is formed from atoms. These recent results indicate that the traditional models are wrong and we should solve the many-body quantum electron problem exactly including exchange-correlation potentials to design new materials with reliability.
DD1/EE1: Joint Session: Synthesis of Nanotubes and Nanowires
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
9:15 AM - DD1.2/EE1.2
Combinatorial Control of Catalysts for Carbon Nanotube Growth: From Sparse Networks for Transparent Electrodes to Dense Forests for Mass Production
Suguru Noda 1 , Hisashi Sugime 1 , Kei Hasegawa 1 , Ryuhei Itoh 1 , Shingo Morokuma 1 , Kazunori Kakehi 1 , Toshio Osawa 1 , Shigeo Maruyama 2 , Yukio Yamaguchi 1
1 Department of Chemical System Engineering, The University of Tokyo, Tokyo Japan, 2 Department of Mechanical Engineering, The University of Tokyo, Tokyo Japan
Show AbstractFor single-walled carbon nanotubes (SWNTs), various applications have been proposed and intensively studied. To realize high-value-added devices such as integrated circuits, many development challenges still exist in the structural control from the chirality of individual SWNTs to the position and orientation of numerous short SWNTs. On the other hand, if the SWNTs can be grown at a low cost, other applications such as transparent conducting films may be realized with fewer innovations in processing technology. In this paper, we applied our combinatorial method [1,2] for catalyst screening and grew SWNTs on substrates at various areal densities and lengths. Co-Mo binary catalysts are known effective to grow SWNTs either from CO and C2H5OH. However, different values are reported as the optimum Co/Mo atomic ratio; 1/3 for the former [3] and 1/1 for the latter [4]. We grew SWNTs from C2H5OH at 1073 K and 0.4-4 kPa for 3-30 min on a catalyst library with orthogonal thickness profiles of 0.01-0.8 nm Co and 0.03-2 nm Mo. Both of those two regions proved catalytically active, and in addition, another region with a large Co/Mo ratio became active at 4 kPa after a few minute incubation time where nanotubes containing SWNTs grew rapidly. By controlling reaction and catalyst conditions, the areal density and length of nanotubes can be controlled. Films of bundled, networked nanotubes show optical and electrical properties depending on the structure. For example, a nanotube film on a quartz glass substrate showed a 85 % transmittance and a 8 kΩ/sq. sheet resistance, whereas a film with a larger nanotube length and a lower areal density showed a 92 % transmittance and a 2 kΩ/sq. sheet resistance. Properties of nanotube films can be tailored in this way.Fe/Al2O3 can rapidly grow SWNTs from C2H4 when a small amount of H2O is added [5]. We applied our combinatorial method to this reaction system. The Fe/Al2O3 catalyst library grew nanotubes of various diameters and the nanotube yield was largely dependent on the nominal Fe thickness. Millimeter-thick films of nanotubes containing SWNTs were formed in 10 min after a complicated optimization among partial pressures of C2H4, H2 and H2O and temperature. Some of these films can be easily separated from the substrate, and this growth mode may be applied for the mass production of SWNTs. [1] S. Noda, et al., Appl. Phys. Lett. 86, 173106 (2005).[2] S. Noda, et al., Carbon 44, 1414 (2006).[3] J.E. Herrera, et al., J. Catal. 204, 129 (2001).[4] Y. Murakami, et al., Chem. Phys. Lett. 385, 298 (2004).[5] K. Hata, et al., Science 306, 1362 (2004).
9:30 AM - DD1.3/EE1.3
Dependence of Carbon Nanotube (CNT) Length and Growth Rate upon Temperature in the Growth of CNT by Metal-catalyzed Chemical Vapor Deposition.
Michael Bronikowski 1
1 Jet Propulsion Laboratory
, California Institute of Technology, Pasadena, California, United States
Show AbstractMonday PM, April 09, 2007
Room 2003 (Moscone West)
9:30 AM - **DD2.2
First Principles Structures and Properties of Nanotubes.
William Goddard 1
1 Materials and Process Simulation Center, Caltech, Pasadena, California, United States
Show AbstractCombining Quantum mechanics with first principles derived reactive force fields (ReaxFF) it is now possible to make reliable predictions on complex structures incorporating one-dimensional nanotubes. We will report here results on two systems 1) metal-carbon nanotube contacts, 2) thermoelectric properties on nanowires and nanotubes, to illustrate the role of theory and computation in characterizing and optimizing such systems.
DD1/EE1: Joint Session: Synthesis of Nanotubes and Nanowires
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
9:45 AM - DD1.4/EE1.4
Control of Catalyst Nanoparticles for Selective CVD Growth of Carbon Nanotubes.
Yunyu Wang 1 , Bin Li 1 , Zhiquan Luo 1 , Li Shi 2 , Zhen Yao 3 , Eugene Bryan 4 , Robert Nemanich 5 , Paul Ho 1 2
1 Microelectronics Research Center, The University of Texas at Austin, Austin, Texas, United States, 2 The Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas, United States, 3 The Department of Physics, The University of Texas at Austin, Austin, Texas, United States, 4 The Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States, 5 The Department of Physics, North Carolina State University, Raleigh, North Carolina, United States
Show Abstract10:00 AM - DD1.5/EE1.5
Synthesis and Structural Characterization of Aligned Carbon Nanotubes on Sapphire and Quartz Substrates
Lewis Gomez 1 , Bo Lei 2 , Koungmin Ryu 2 , Alexander Badmaev 2 , Xiaolei Liu 2 , Steve Cronin 2 , Chongwu Zhou 2
1 Chemistry, USC, Los Angeles, California, United States, 2 Electrophysics, USC, Los Angeles, California, United States
Show AbstractSynthesis of massively aligned single-walled carbon nanotubes has stimulated significant interest due to their potential for integrated nanotube circuits and systems. Despite recent success on the synthesis, there is still a lack of study on the influence of the substrate on the structural and ultimately physical properties of the nanotubes. In this talk we will present our recent advance in aligned nanotube synthesis and also in-depth Raman characterization of the nanotubes obtained. The synthesis of aligned nanotubes was achieved using a chemical vapor deposition technique with Ferritin as the catalyst and a-plane sapphire and mistcut quartz as the substrates. Simultaneous control over the nanotube orientation and position has also been achieved by patterning catalyst at desired sites on the crystalline substrates. The nanotubes on a-plane sapphire were found to lie normal to the c-axis of the substrate, while the nanotubes on quartz followed the step edges of the miscut substrates. AFM and SEM microscopy combined with vibrational resonantly enhanced micro Raman characterization was proved to be a powerful tool to structurally characterize the samples at the single nanotube level. We use three different laser energies to determine diameter distribution and non-nanotube carbon impurities. The metallic to semiconducting ratio analysis of the carbon nanotubes revealed a metallic nanotube content of ~ 27%. Polarized Raman spectra of nanotubes showed a suppression of the C=C stretching mode when the laser electric field axis was perpendicular to the nanotubes principal axis. Furthermore, electrical properties on nanotubes produced on the different substrates were evaluated. Our results demonstrate that the surface molecular arrangement of the substrate as well as surface-carbon interactions play an important role in the properties of the synthesized nanotubes.
Monday PM, April 09, 2007
Room 2003 (Moscone West)
10:00 AM - **DD2.3
Atomic Scale Design of Nanostructures
Jerry Bernholc 1 2 , W. Lu 1 , M. Buongiorno Nardelli 1 2 , V. Meunier 2 , F. Ribeiro 1 , S. Wang 1 , Q. Zhao 1
1 Physics, NC State University, Raleigh, North Carolina, United States, 2 CSMD, ORNL, Oak Ridge, Tennessee, United States
Show AbstractNanoscale and molecular electronics promises to revolutionize computing, sensing, and electronic warfare. However, molecular-scale control and manufacturing are difficult tasks, which require major advances to become practical in large-scale applications. The development of molecular scale devices and circuits can be greatly enhanced by predictive simulation of their components and by formulating design principles that will make molecular circuitry smaller, more efficient and more reliable. We will discuss three recent applications: (i) Nanotube-cluster systems, which behave as effective chemical sensors whose electrical response changes dramatically upon adsorption of small molecules onto the metal clusters, enabling detection of minute quantities of adsorbants. (ii) We show that the celebrated Negative Differential Resistance (NDR) effects can be expected for a wide range of small organic molecules attached to semiconductor leads. For example, if benzene is suspended between Si leads, NDR occurs when its LUMO drops below the conduction band edge of the negative lead. For more complex molecules, such as porphyrins, which are candidates for multibit molecular memories, crossing of band edges by various molecular levels leads to multiple NDR effects. (iii) For organic self-assembled ferrocenyl monolayers on gold, NDR occurs due to crossing of the Fermi level by the molecular HOMO. In general, our results show that NDR must occur for surprisingly simple structures. This enables the design of molecule-based NDR devices based mainly on processing considerations, rather than the choice of specific molecules.
DD1/EE1: Joint Session: Synthesis of Nanotubes and Nanowires
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
10:15 AM - DD1.6/EE1.6
Influence of Hydrogen Level During the Growth Process on the Properties of Single-wall Carbon Nanotubes.
Alexandru Biris 1 2 , Alexandru Biris 3 , Dan Lupu 3 , Zhongrui Li 2 , Enkeleda Dervishi 1 2 , Viney Saini 1 2
1 Applied Science , University of Arkansas at Little Rock, Little Rock, Arkansas, United States, 2 Nanotechnology Center, University of Arkansas at Little Rock, Little Rock, Arkansas, United States, 3 , National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj Napoca Romania
Show Abstract10:30 AM - DD1.7/EE1.7
High Yield Multiwall Carbon Nanotube Synthesis in Supercritical Fluids
Danielle Smith 1 , Doh Lee 1 , Brian Korgel 1
1 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States
Show AbstractMultiwall carbon nanotubes (MWNTs) were synthesized in supercritical toluene at temperatures ranging from 600 to 645 °C at 8.3 MPa using ferrocene, cobaltocene, nickelocene, Fe, and Co nanocrystals as catalysts. A continuous flow reactor was used to produce nanotubes with outer diameters of 10 - 50 nm and wall thicknesses of 5 - 20 nm.In this supercritical fluid synthesis, toluene served as both the solvent and the primary carbon source for nanotube formation. We also discovered that supplemental carbon sources, either hexane or ethanol (30 vol %), increased the yield of the carbon nanotubes relative to pure toluene by almost an order of magnitude. Additionally, catalytic amounts of water (0.75 vol %) minimized the formation of carbon filaments and amorphous carbon deposition. Cobalt and nickel precursors in addition to the use of a continuous flow reactor led to much higher yields than previous batch reactions in supercritical toluene. Using cobaltocene as a catalyst, with ethanol as a supplemental carbon source, gave the highest percentage of nanotubes in the product (70%) and the highest conversion of toluene to MWNTs (4%). Cobaltocene was also the best catalyst in terms of purity of the product with the highest proportion of carbon nanotubes produced relative to carbon filaments and amorphous carbon. These observations might be explained by examining the phase diagrams, which report higher carbon solubility into Co compared to Ni and Fe at temperatures of 600 to 650 °C.The MWNTs generated in this supercritical fluid system tended to exhibit bamboo morphology and appear to grow by a folded-growth mechanism with graphitic sheets wrapped around the seed metal particles. Many MWNTs exhibited significant defects in their graphitic layers, resulting in curly and kinked nanowires. In some cases where cobaltocene was used as a catalyst, the nanowire bending was consistent along the length of the nanotube, resulting in coiled nanotube formation, with the appearance of springs, hairpins, lassos, and coiled ropes. In future work, conditions might be identified that will enable SWNT synthesis.
Monday PM, April 09, 2007
Room 2003 (Moscone West)
10:30 AM - DD2.4
Modeling the Conductance of a Nanotube Bundle Connected to a Copper Surface
Steven Compernolle 1 2 , Geoffrey Pourtois 2 , Bart Soree 2 , Wim Magnus 2 , Arnout Ceulemans 1
1 Laboratorium voor kwantumchemie, and INPAC - Institute for Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, Leuven Belgium, 2 , IMEC, Leuven Belgium
Show AbstractDD1/EE1: Joint Session: Synthesis of Nanotubes and Nanowires
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
10:45 AM - **DD1.8/EE1.8
Synthesis and Applications of Classes of Non-carbonaceous Nanostructures.
Stanislaus Wong 1 2
1 Department of Chemistry, SUNY Stony Brook, Stony Brook, New York, United States, 2 Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractMonday PM, April 09, 2007
Room 2003 (Moscone West)
11:00 AM - **DD2.5
Equilibrium and Dynamics in Polymer-Nanoparticle Mixtures.
Venkat Ganesan 1
1 Chemical Engineering, The University of Texas at Austin, Austin, Texas, United States
Show AbstractMixtures of polymers and particles occur in a wide variety of applications. Traditional applications of polymers in such systems include their role as colloidal stabilizers, and in rheological modifiers. Many of these applications are characterized by the feature that the polymer size is much smaller than the size of the particle. However, more recent developments in nano- and biotechnology applications have moved the polymer-particle mixtures from the ``colloid limit'' to the ``nanoparticle limit'' where the polymer size is comparable to or larger than the size of the particle. This transition to the nanoparticle limit has brought forth new physical aspects and challenges. At the equilibrium level, the curvature of the particle now plays an important role in determining the interactions and phase behavior. At a dynamical level, conventional ``continuum'' wisdom no longer applies, and counterintuitive phenomena have been observed. This talk will focus on some recent work in our group which addresses the issue, "how does the equilibrium, dynamical and rheological aspects of nanoparticle-polymer mixtures differ from their colloidal counterparts ?" It will be demonstrated that many aspects of colloidal physics is still applicable, albeit allowance must be made for polymer-particle, particle-particle and polymer-polymer interactions, particle curvature and the relative sizes of the polymer and particles. In essence, the theoretical predictions delineates the size scales at which the particles cross-over from behaving both in equilibrium and dynamics as a ``particle suspension in polymers'' to a ``solvent for the polymers.'' Some applications of our findings to the context and experiments of protein-polymer mixtures and polymer nanocomposites will also be presented.
DD1/EE1: Joint Session: Synthesis of Nanotubes and Nanowires
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
11:30 AM - **DD1.9/EE1.9
Nanowires and Nanotubes Synthesized in Solution: Their Chemistry, Twins and Branching.
Brian Korgel 1
1 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States
Show AbstractMonday PM, April 09, 2007
Room 2003 (Moscone West)
11:30 AM - **DD2.6
Theory of Effective Interactions, Structure and Phase Behavior of Polymer Nanocomposites
Kenneth Schweizer 1 , Justin Hooper 1 2 , Lisa Hall 1
1 Materials Science, University of Illinois, Urbana, Illinois, United States, 2 Materials Science, University of Utah, Salt Lake City, Utah, United States
Show AbstractMicroscopic polymer liquid state theory has been employed to study second virial coefficients, the potential of mean force (PMF), pair correlation functions, scattering patterns, and the miscibility of hard spherical nanoparticles in a dense polymer melt over a wide range of interfacial chemistry, chain length, and filler size and volume fraction conditions. A variable strength and range monomer-particle attractive potential is used to probe the material-specific competition between packing entropy and interfacial adsorption. As interfacial cohesion increases the nanoparticle organization evolves from contact depletion aggregation, to well dispersed sterically stabilized behavior associated with a thermodynamically stable polymer coating, to tightly-bridged particles. Near linear scaling of the PMF with the particle/monomer size asymmetry ratio is found, and the spatial range of the interfacial attraction is important in determining nanoparticle organization. Spinodal demixing calculations predict two types of phase separated states which bracket a miscibility window. For weak interfacial attractions an entropy-driven fluid-fluid phase separation occurs, while for strong cohesion an enthalpically driven network or complex formation type of demixing is predicted. The miscibility window at intermediate interfacial attraction strengths represents a compromise between energetic and entropic considerations. Its existence is delicate in the sense that the miscibility window systematically narrows, and is ultimately destroyed, as particle size and/or direct filler-filler attractions increase. The length-scale dependent real space statistical structure has been quantified via calculations of the intermolecular pair correlation functions and partial scattering structure factors. At high filler volume fractions interference between the polymer organization near nanoparticle surfaces results in significant modification of particle packing and degree of collective order. The presence of bound polymer layers in miscible nanocomposites results in microphase-separation-like features in the collective polymer structure factor at small wavevectors, and comparisons with the recent neutron scattering measurements of Kumar and coworkers will be presented. The implications of the theoretical results for the design of thermodynamically and/or kinetically well-dispersed polymer nanocomposites, and the formation of a nonequilibrium network-like material, will be discussed. The theory has also been generalized to treat the consequences of soft intermolecular repulsions, and nonspherical fillers of variable dimensionality including rod, disk and compact molecular-like shapes.
DD1/EE1: Joint Session: Synthesis of Nanotubes and Nanowires
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
12:00 PM - DD1.10/EE1.10
Alternative Catalysts For Si-Technology Compatible Growth Of Si Nanowires.
Francesca Iacopi 1 , Philippe Vereecken 1 , Nele Moelans 2 , Bart Blanpain 2 , Hefin Griffiths 3
1 , IMEC, Leuven Belgium, 2 MTM, Katholieke Universiteit Leuven, Leuven Belgium, 3 , Oxford Instruments, Bristol United Kingdom
Show AbstractAu has been widely demonstrated in literature as an efficient metal catalyst for the growth of semiconducting nanowires [1]. Also metals such as Ag, Cu, Pd have been shown to be efficient catalysts for growth of Si whiskers [2]. Nevertheless, from a Si semiconductor technology point of view, most of those are undesired metals, either because their diffusion into bulk silicon leads to the formation of mid gap states [3], or because they react with Si, leading to uncertainties on the final stechiometry of the precipitate. In order to allow a viable evolutionary path from the conventional planar CMOS technologies to 1D nanowire –based devices, alternative catalyst materials more compatible with Si and allowing nanowire growth at temperatures at least around or below 500○C need to be established.In this context, feasibility for growth of Si nanowires catalysed by Indium nanoparticles was investigated. Indium shows several advantages: does not react with Si, is compatible with Si technology (it is used as p-type dopant material), and is also a thermodynamically favourable catalyst for Si nanowhisker growth according to the Vapor-Liquid-Solid (VLS) theory. Indeed, the In-Si system has a low eutectic temperature (157○C) with low Si solubility (0.004%). On the other hand, Indium is not an efficient catalyst for the dehydrogenation reaction of SiH4, reason why early attempts for Si nanowires growth with In nanoparticles were not successful [2]. Growth experiments were conducted in a Plasma Enhanced Chemical Vapour Deposition system onto (100) Si, previously electroplated with In nanoparticles with diameter ranging roughly between 200nm and 30nm. Slightly tapered Si nanowires were grown at rather high rate (~300nm/min) at 500○C, using silane as precursor gas and low RF power (5W). Tip growth was recognized from the almost spherical In particles observed on the top of the whiskers, in agreement with the VLS model. In addition to In, the efficiency of other Si –compatible metal catalysts such as Al, Sb, Ga is currently under investigation. The selection of the catalyst system will be extended to favourable alloys/compounds by means of thermodynamics calculations of ternary systems with Si. Feasibility for SiGe nanowire growth using the same catalysts will also be investigated.[1] R.S.Wagner, W.C.Ellis, Appl.Phys.Lett. 4 (5), pp.89-90, 1964[2] G.A.Bootsma, H.J.Gassen, J.Crystal Growth 10, pp.223-234, 1971 [3] S.M.Sze, Physics of Semiconductor Devices, Wiley Interscience, New York, 1981
Monday PM, April 09, 2007
Room 2003 (Moscone West)
12:00 PM - **DD2.7
Nanoscale Phenomena in Polymer – Nanoparticle Blends.
Michael Mackay 1
1 , Michigan State University, East Lansing, Michigan, United States
Show AbstractDD1/EE1: Joint Session: Synthesis of Nanotubes and Nanowires
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
12:15 PM - DD1.11/EE1.11
Plasma-stimulated Control of Silicon Nanowire Nucleation, Orientation and Growth Kinetics.
Pavan Reddy Aella 1 4 , W. Petuskey 1 4 , S. Picraux 2 3 4
1 Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, United States, 4 Science and Engineering of Materials Graduate Program, Arizona State University, Tempe, Arizona, United States, 2 Department of Chemical and Materials Engineering, Arizona State University, Tempe, Arizona, United States, 3 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show Abstract12:30 PM - DD1.12/EE1.12
Quantitative Determination of the Nucleation Kinetics of Si Nanowires.grown on Si3N4 substrates by the VLS mechanism
Bong-Joong Kim 1 , Suneel Kodambaka 2 , Mark Reuter 2 , Kathy Reuter 2 , Eric Stach 1 , Frances Ross 2
1 Eric Stach, Purdue University, West Lafayette, Indiana, United States, 2 , IBM Watson Research Center, Yorktown Heights, New York, United States
Show AbstractMonday PM, April 09, 2007
Room 2003 (Moscone West)
12:30 PM - **DD2.8
Polymer-Inorganic Nanocomposites: Theoretical Studies of Thermodynamics and Phase Behavior
Valeriy Ginzburg 1
1 , The Dow Chemical Company, Midland, Michigan, United States
Show AbstractPolymer nanocomposites (PNC) represent a new class of materials that is being actively developed for a wide variety of commercial applications (automotive, packaging, cosmetics, electronics, etc.) Particular attention is paid to three main classes: (i) polymer/metal nanoparticle composites; (ii) polymer/carbon nanotube composites; (iii) polymer/clay nanocomposites. Significant successes have been achieved in making these systems yet our understanding of their behavior is still rather limited. In my talk, I will describe recent theoretical efforts aimed at the understanding of thermodynamics and phase behavior of PNC’s. In particular, we will examine theoretical models describing (i) self-assembly of block copolymer/metal nanoparticle mixtures, and (ii) morphology of clay platelets in homogeneous polymer melts. We will see that the size and geometry of the nanoscale fillers play a crucial role in determining the morphology and phase behavior of the nanocomposite. It is shown that for the case of small (5—10 nm) nanoparticles, self-assembly can indeed guide the system towards thermodynamically stable morphologies (e.g., lamellar morphologies with particles segregated into one block or at the interfaces between lamellar domains). In the case of clays, on the other hand, thermodynamically advantaged morphology is often the “macrophase separated” state where clay platelets are segregated from the matrix; it becomes necessary, therefore, to be able to preserve the system in a non-equilibrium state (which is often difficult to do). Overall, theoretical predictions – while imperfect – could serve as good guidelines for the composite formulation design.
DD1/EE1: Joint Session: Synthesis of Nanotubes and Nanowires
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
12:45 PM - DD1.13/EE1.13
Self-assembled Tm Silicide Nanowires on Si(001) Studied by STM and TEM.
Jiaming Zhang 1 , M. Crimp 1 , Yan Cui 2 , J. Nogami 2
1 Department of Chemical Engineering and Materials Science, Michigan State University, East lansing, Michigan, United States, 2 Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario, Canada
Show AbstractSelf-assembled rare earth (RE) metal silicide nanowires are promising for application in future nano interconnects and devices. Since the formation of epitaxial silicide nanowires by deposition of RE metals on Si(001) was first discovered, intense interest has been focused on the epitaxial growth mechanism of RE silicides on Si surfaces. Our recent work has shown that Tm silicides form epitaxial nanowires on Si(001). Unlike many of the other nanowire forming RE metals, which have several different polymorphic silicides at about the same stoichiometry, Tm forms three bulk silicides Tm5Si3,TmSi, and Tm3Si5 with very different compositions and crystal structures. The latter two phases the potential for nanowire formation. Scanning tunneling microscopy (STM) shows many 3D nanowires with some larger square islands. However, the structures of the nanowires seem to be more complex than in the case of other RE silicides. Surface reconstructions on these indicate strain relief mechanisms within these wires. Plan-view and cross-sectional high resolution transmission electron microscopy (HRTEM) results will be used to correlate silicide crystal structure to island and nanowire morphology.
DD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
2:30 PM - DD3.1/EE2.1
Growth of SiC Nanowires in Different Directions on Sapphire Substrates
Qingkai Yu 1 , Shin-Shem Pei 1 , Jian Shi 2 , Hao Li 2
1 , Univ of Houston , Houston, Texas, United States, 2 , University of Missouri, Columbia, Missouri, United States
Show AbstractFree-standing SiC nanowires and SiC nanowires on R-plane sapphire substrates were grown by chemical vapor deposition. SiO vapor and various carbon sources are the precursors for the formation of SiC nanowires. The morphology and composition were characterized by SEM, TEM, AFM, and XPS. TEM results demonstrate that the nanowires have a core-shell structure. It was also found that the diameter of SiC nanowires influence the morphology of both free-standing SiC nanowires and the ones on sapphire substrates. The directions of SiC nanowires grown on R-plane sapphire substrates are affected by precursors, experimental conditions, and the substrates. At the end, the electrical properties and potential applications are also discussed.
Monday PM, April 09, 2007
Room 2003 (Moscone West)
2:30 PM - DD4.1
Limit of Coherency in Core-shell and Axially Heterogeneous Metallic and Semiconductor Nanowires via Molecular Dynamics.
Arvind Arumbakkam 1 , Yumi Park 1 , Amritanshu Palaria 2 , Alejandro Strachan 1
1 School of Materials Engineering, Purdue University, West Lafayette, Indiana, United States, 2 Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana, United States
Show AbstractDD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
2:45 PM - DD3.2/EE2.2
Thermodynamics and Kinetics of Germanium Nanowire Nucleation and Growth
Hemant Adhikari 1 , Paul McIntyre 1 , Christopher Chidsey 2 , Ann Marshall 3
1 Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 Chemistry, Stanford University, Stanford, California, United States, 3 Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California, United States
Show AbstractIn 3-dimensional nanoelectronics, vertically aligned nanowires have been proposed to provide a solution to attain ultra high density nanoscale device arrays. We have demonstrated the growth of vertically aligned single-crystal germanium nanowires (GeNWs) at temperatures of 400°C or less by metal nanoparticle-catalyzed chemical vapor deposition. We found that temperatures close to bulk eutectic of Au-Ge are required for efficient nucleation of epitaxial nanowires on Ge substrates, but the subsequent growth of nanowires can be carried out at temperatures as low as 270°C. To understand the nucleation of nanowires from gold catalyst particles and to test whether the Vapor-Liquid-Solid mechanism is actually responsible for the growth of nanowires, it is important to understand the phase equilibrium between Au nanoparticles and germanium. Capillary effects, often represented by the Gibbs-Thomson pressure, increase the free energy of the nanoparticle catalyst and the nanowire relative to their bulk values and hence cause lower the eutectic temperature. NW nucleation, where the catalyst nanoparticle is initially in contact with a flat Ge surface, and NW growth, where it is in contact with a GeNW, are very different situations. We have calculated the equilibrium phase diagrams for both the Au-rich liquid nanoparticle in contact with flat Ge (nucleation) and Au-rich liquid nanoparticle in contact with nanowire (growth) cases. The Gibbs-Thomson pressure effect is estimated to be insufficient to stabilize a liquid at the temperatures at which we observe stable Ge NW growth. However, we have also derived limiting expressions for the metastable liquidus for the Au-Ge binary system when a nano-scale liquid droplet is supersaturated with Ge during GeNW growth. Results obtained from these calculations suggest that much larger undercoolings of a Au-Ge liquid are possible during Ge NW growth, consistent with our experimental observations. Ex-situ heating and cooling behavior of germanium nanowires of different diameters (without Ge deposition) was observed inside a transmission electron microscope column. We noted that temperatures close to bulk eutectic were required for the Au tip of nanowire to melt and form a eutectic alloy with the GeNW during the heating cycle. But, when cooling from a high temperature, the liquid alloy remained stable for an under-cooling of the order of 100°C. These ex-situ TEM heating/cooling results suggest that a substantial undercooling of the liquid below the bulk eutectic temperature may also arise because of the barrier associated with nucleating solid Au. A critical assessment of the importance of the Au nucleation barrier versus Ge supersaturation of the Au-Ge catalyst particle in maintaining a liquid catalyst at large undercoolings will be presented.
Monday PM, April 09, 2007
Room 2003 (Moscone West)
2:45 PM - DD4.2
One Dimensional Silicon Nanostructures: Atomic Level Structures and Properties from MD and DFT.
Amritanshu Palaria 1 2 , Alejandro Strachan 2
1 School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana, United States, 2 School of Materials Engineering, Purdue University, West Lafayette, Indiana, United States
Show AbstractDD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
3:00 PM - DD3.3/EE2.3
Vapor-liquid-solid Growth of Ge Nanowires at Temperatures Below the Eutectic Temperature.
Suneel Kodambaka 1 2 , Jerry Tersoff 1 , Kathleen Reuter 1 , Frances Ross 1
1 Physical Sciences, IBM T. J. Watson Research Center, Yorktown Heights, New York, United States, 2 Materials Science and Engineering, University of California, Los Angeles, California, United States
Show AbstractMonday PM, April 09, 2007
Room 2003 (Moscone West)
3:00 PM - DD4.3
Electronic Structure of Silicon-Based Nanostructures
Lok Lew Yan Voon 1 , Gian Guzman-Verri 2
1 Physics, Wright State University, Dayton, Ohio, United States, 2 Centro de Investigaciones en Ciencia e Ingeniería de los Materiales, Universidad de Costa Rica, San José Costa Rica
Show AbstractWe have developed a new unifying tight-binding theory that can model the electronic properties of recently proposed Si-based nanostructures [1,2], namely, Si graphene-like sheets and Si nanotubes. The electronic properties of silicene, Si (111), Si h-NT's and Si g-NT's were studied via a tight-binding approach. We derived sp3s* and sp3 models up to first- (1NN) and second-nearest (2NN) neighbors, respectively. We compared the band structures of Si (111) and of silicene to the one of graphene. We expect Si (111) and silicene to be either semiconductors of band gap zero or metals. Electrons in the neighborhood of the K point should behave as Dirac massless fermions. However, the Fermi velocity v0 in Si (111) (104 m/s) and in silicone (105 m/s) are smaller than the one in graphene (106 m/s). Silicon h-NT's and Si g-NT's were compared to carbon nanotubes (CNT's) as well. The band structure of Si h-NT's and of CNT's are similar two each other. In the case of zig zag semiconductor Si h-NT's, the gap is inversely proportional to the tube diameter, as in zig zag CNT's, nonetheless, for a given diameter, Si h-NT's will have a smaller gap. The magnitude of the effective masses is also inversely proportional to their diameter. However, for a given diameter, Si h-NT's have greater mass, which makes CNT's more suitable for transport properties. As far as Si g-NT's are concerned, we found that they follow Hamada's rule [3] as CNT's do, even though they show different hybridizations. Our calculations for all the Si-based materials considered here were compared to the ab initio calculations performed by Yang et al. [2]. When comparing silicene and Si (111), we found that the 2NN sp3 model is in better agreement with Yang's band structures than the 1NN sp3s* model. For Si h-NT's, our band structures agree with the ones obtained by Yang et al. [2]: they all follow Hamada's rule. In contrast, they disagree for all Si g-NT's. Whereas our calculations show that these nanotubes also follow this rule, Yang's calculations do not. Work supported by an NSF CAREER award (NSF Grant No. 0454849), and by a Research Challenge grant from Wright State University and the Ohio Board of Regents. [1] J. Sha, J. J. Niu, X. Y. Ma, J. Xu, X. B. Zhang, Q. Yang and D. Yang, Silicon nanotubes. Adv. Mat. 14, 1219 (2002).[2] X. B. Yang and J. Ni, Electronic properties of single-walled silicon nanotubes compared to carbon nanotubes, Phys. Rev. B 72, 195426 (2005).[3] N. Hamada, S.I. Sawada and A. Oshiyama, New one-dimensional conductors: Graphitic microtubules, Phys. Rev. Lett. 68, 1579 (1992).
DD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
3:15 PM - DD3.4/EE2.4
Growth of Boron Nanowires by Chemical Vapor Deposition
Li Guo 1 , Raj Singh 1
1 Chemical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio, United States
Show AbstractMotivated by the extensive research on carbon nanotubes (CNTs), boron and its related nano-structures have attracted increasing interests for potential applications in nanodevices and nanotechnologies due to their extraordinary properties. B-related nanostructures are successfully grown on various substrates in a CVD process. The boron nanowires have diameters around 20-200 nanometers and lengths up to microns. Icosahedra B12 is shown to be basic building unit forming the B nanowires by Raman. The gas chemistry is monitored by the in-situ mass-spectroscopy, which helps to identify reactive species in the process. A nucleation controlled growth mechanism and VLS growth are proposed for the growth of these nanostructures. The role of the catalysts in the synthesis is also discussed.
Monday PM, April 09, 2007
Room 2003 (Moscone West)
3:15 PM - DD4.4
Study of Charged Exciton in Silicon Quantum Dot.
Gian Franco Sacco 1 , Paul von Allmen 1 , Seungwon Lee 1
1 , Jet Propulsion Laboratory, Pasadena, California, United States
Show AbstractDD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
3:30 PM - DD3.5/EE2.5
Plasmon-assisted Local Growth of Individual Semiconductor Nanowires
Linyou Cao 1 2 , David Barsic 1 2 , Alex Guichard 1 2 , Mark Brongersma 1 2
1 Department of Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California, United States
Show AbstractControlled growth of individual semiconductor nanowires (NWs) at well-defined and pre-specified locations will greatly simplify the integration of such NWs into device architectures. It can also prevent possible processing-induced damage to the nanowires common in conventional nano-fabrication process. Conventional chemical vapor deposition (CVD) growth typically produces many nanowires simultaneously in a high-temperature environment and device fabrication requires the use of complex post-processing methods. Here, we demonstrate a new technology capable of locally depositing heat in a pre-specified metal particle. To this end, a low power (~10mW), focused laser beam is used to illuminate a Au nanoparticle layer generated by evaporation and annealing. The laser wavelength is chosen to match the surface plasmon resonance frequency of the Au particles, such that the electromagnetic energy is efficiently converted to heat. Growth occurs when 2% SiH4 in Ar gas is delivered to this heated area. The high temperature region is confined to the immediate viscinity of the heated particle with the environment remaining at room temperature. The observed results are in agreement with a thermal model that predicts the temperature distribution around an illuminated Au particle for a certain laser power density and spot size. This work could have a major impact on the field of nanoparticle catalysis and growth and enable new NW-based devices to be realized.
Monday PM, April 09, 2007
Room 2003 (Moscone West)
3:30 PM - DD4.5
Shape and Size Dependent Exciton Fine Structure of CdSe Nanocrystals.
Qingzhong Zhao 1 , Kwiseon Kim 1 , Peter A. Graf 1 , Alberto Franceschetti 1 , Wesley B. Jones 1 , Lin-Wang Wang 2
1 , National Renewable Energy Laboratory, Golden, Colorado, United States, 2 Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractWe investigate the exciton fine structure of CdSe nanocrystals using empirical pseudopotential calculations.We studied the shape and size effects by calculating the band-edge states of CdSe spherical quantum dots, elongated nanorods, and flattened nanodisks.Large scale electronic calculations consisting of 100--20,000 atoms with diameters ranging from 2 to 8 nm and lengths from 2 to 11 nm were performed. Band-edge states of semi-infinite 1D quantum wires and 2D quantum wells were also calculated.We used the empirical pseudopotential method and the configuration interaction method [1,2] to obtain the band-edge exciton fine structure.We find the experimentally observed dark-bright exciton state crossing [3]. We discuss its shape and size dependency. [1] L. W. Wang and A. Zunger, Phys. Rev. B 51, 17398 (1995); J. Li and L. W. Wang, Nano Lett., 3, 1357 (2003). [2] A. Franceschetti, H. Fu, L. W. Wang, and A. Zunger, Phys. Rev. B. 60 1819 (1999). [3] N. Le Thomas, E. Herz, O. Schops, and U. Woggon, Phys. Rev. Lett. 94, 016803 (2005).
DD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
3:45 PM - DD3.6/EE2.6
Growth Direction Control in Zinc Oxide Nanowires
Husnu Unalan 1 , Pritesh Hiralal 1 , Yang Yang 1 , Tim Butler 1 , Nalin Rupesinghe 1 , Ken Teo 1 , Gehan Amaratunga 1
1 Electrical Engineering Division, Engineering Dept., University of Cambridge, Cambridge United Kingdom
Show AbstractGrowth direction control of nanowires is essential in determining the integration density as well as positioning of the nano scale devices. In this work, we have utilized electric field during growth of zinc oxide (ZnO) nanowires by chemical vapor deposition for the control of growth direction. Both lateral and vertical growth results will be described. The alignment techniques used follow from those developed for deterministic growth of single walled [1] and multi walled [2] carbon nanotubes. Electric field inside the plasma sheath is exploited for vertical alignment, whereas an auxiliary DC is applied to generate the field for the lateral alignment. We have analyzed the as-grown ZnO nanowires with scanning electron microscopy, transmission electron microscopy, photoluminescence and electrical measurements. In brief, the work reported is a step towards integration of ZnO nanowires in nanoscale electronic and optoelectronic devices. [1] Y. Zhang, A. Chang, J. Cao, Q. Wang, W. Kim, Y. Li, N. Morris, E. Yenilmez, J. Kong, H. Dai, Appl. Phys. Lett 79 (2001) 3155.[2] M. Chhowalla, K. B. K. Teo, C. Ducati, N.L. Rupesinghe, G.A.J. Amaratunga, A.C. Ferrari, D. Joy, J. Robertson, W. I. Milne, J. Appl. Phys. 90 (2001) 5308.
Monday PM, April 09, 2007
Room 2003 (Moscone West)
DD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
4:15 PM - DD3.7/EE2.7
Synthesis and Photoluminescence Properties of Ultrathin Alumina-coated ZnO Nanotubes Grown on Si Wafer.
Chi-Sheng Hsiao 1 , San-Yuan Chen 1 , Wan-Lin Kuo 1
1 Department of materials science and engineering, National Chiao Tung University, Hsinchu Taiwan
Show AbstractMonday PM, April 09, 2007
Room 2003 (Moscone West)
4:15 PM - DD4.6
Fully Ordered Array Of Subnano II-VI Semiconductor Wires Coordinated By Organic Molecules: Electronic And Optical Properties.
Yong Zhang 1 , Brian Fluegel 1 , Angelo Mascarenhas 1 , Lin-Wang Wang 2 , Xiao-Ying Huang 3 , Jing Li 3
1 Materials Science Center, National Renewable Energy Lab., Golden, Colorado, United States, 2 Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey, United States
Show AbstractA new family of inorganic-organic hybrid crystals based on II-VI semiconductors has recently been synthesized. The success of synthesizing such materials represents two major advances in nanotechnology: (1) the ability to obtain fully ordered nanostructure arrays without any structural and chemical fluctuation typically found in other hybrid materials and nanostructures, and (2) the opportunity to explore the subnano region for both fundamental sciences and applications. These novel hybrid crystals are typically composed of subnano inorganic building blocks interconnected or coordinated by small organic molecules, and have been shown to exhibit numerous unusual electronic and optical properties.[1-3] They can be classified into three categories: 3-D, 2-D, and 1-D structures. In this presentation, we focus on the 1-D structure, that is, a fully ordered array of II-VI semiconductor (e.g., ZnTe) wires coordinated by organic molecules (e.g., pda = C3N2H10). The wire is in fact a single chain of II-VI binary semiconductor in a wurtzite structure, thus it forms the smallest possible nanowire practically achievable. Because of the extremely small physical scale and thus exceedingly strong quantum confinement effect, the wire array has shown a huge bandgap shift near 2 eV, compared to the II-VI binary. Both electronic structure, calculated through first-principles density function, and experimental studeis using various optical techniques will be presented. References:[1] X.-Y. Huang, J. Li, Y. Zhang, and A. Mascarenahs, JACS 125, 7049 (2003).[2] B. Fluegel, Y. Zhang, A. Mascarenahs, X.-Y. Huang, and J. Li, PRB 70, 205308 (2004).[3] Y. Zhang, G. M. Dalpian, B. Fluegel, Su-Huai Wei, A. Mascarenhas, X.-Y. Huang, J. Li, and W.-L. Wang , PRL 96, 26405(2006).Work supported by DOE, NREL LDRD, and NSF.
DD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
4:30 PM - DD3.8/EE2.8
Formation and Applications of Biphasic GaN Nanowires as a Function of Growth Parameters.
Kaylee McElroy 1 , Benjamin Jacobs 1 , Andrew Baczewski 1 , Virginia Ayres 1 , Joshua Halpern 2 , Mao He 2 , Mihail Petkov 3 , Martin Crimp 1 , Harry Shaw 4
1 College of Engineering, Michigan State University, East Lansing, Michigan, United States, 2 Department of Chemistry, Howard University, Washington D. C., District of Columbia, United States, 3 , NASA Jet Propulsion Laboratory, Pasadena, California, United States, 4 , NASA Goddard Space Flight Center, Greenbelt, Maryland, United States
Show AbstractMonday PM, April 09, 2007
Room 2003 (Moscone West)
4:30 PM - DD4.7
Switching Behavior in Silicon-Molecule-SWCNTs Devices: A Density Functional Theory Study
Brahim Akdim 1 , Ruth Pachter 1
1 , AFRL/ML, Wpafb, Ohio, United States
Show AbstractRecently, a testbed for exploring the electrical properties of single molecules was fabricated [He, J., et al., Nat. Mat. 2006], in order to eliminate the possibility of metal nanofilament formation and to ensure that molecular effects are measured. Silicon and single-wall carbon nanotubes (SWCNTs) were used as electrodes for the molecular monolayer. These devices were found to exhibit a hysteresis in the current-voltage characteristics for π-conjugated molecules. In this work, in order to gain an understanding of the switching behavior, we present a density functional theory study (DFT), combined with the non-equilibrium Green’s function formalism, for oligo(phenylene ethynylene) and its derivatives, as well as for the arylalkanes molecules bridged between a SWCNT and a Si slab. Conformational changes in the molecules, due to an applied field, and their interaction with SWCNT, will be reported. A detailed structural analysis, electronic structures, and the density of states near the Fermi level as a function of an applied field, will be outlined. In addition to the DFT results, the charge transport obtained by applying the non-equilibrium Green’s function formalism will be discussed.
DD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
4:45 PM - DD3.9/EE2.9
Single-Crystalline Nanotubes of II3-V2 Semiconductors.
Guozhen Shen 1 , Yoshio Bando 1 , Dmitri Golberg 1
1 Nanoscale Materials Center, National Institute for Materials Science, Tsukuba Japan
Show AbstractIn recent years, considerable attention has been paid to 1-D nanostructures owing to their unique physical and chemical properties, and potential applications in nanoscale devices with diverse functions [1]. Semiconducting II3-V2 compounds are of great scientific and technological importance. Due to the large excitonic radii of these materials, they are expected to exhibit pronounced size quantization effects. The electrons in such a semiconductor will become confined in crystals much larger than for the analogous II-VI or III-V semiconductors. However, compared with the significant progress in 1-D nanoscale II-VI and III-V semiconductors, research on nanoscale II3-V2 semiconductors has been lingering far behind because of the lack of appropriate and generalized synthetic methodologies [2]. Herein, we report the first synthesis of single-crystalline II3-V2 nanotubes, Cd3P2 and Zn3P2 nanotubes, by thermal evaporation a mixture of ZnS (or CdS), P, and Mn3P2 powders in a vertical induction furnace [3] by a self-sacrificing template process, in which the in-situ formed Cd or Zn nanorods act as the self-sacrificing templates for the growth of nanotubes. By carefully controlling the experimental parameters, II3-V2 nanotubes based 1D heterostructures are also fabricated using this simple method [4].After reaction, XRD results indicate the formation of pure Zn3P2 and Cd3P2 structures. The morphology and composition of the synthesized products were checked using SEM, TEM and EDS. The results reveal the formation of smooth Cd3P2 nanotubes with outer diameters of 80-250 nm and Zn3P2 nanotubes with outer diameters of 100-200 nm. All the nanotubes have circular cross-sections, open ends without any attached particles, uniform diameters along their entire lengths and very thin walls compared to hollow cavities. HRTEM images shows the clearly marked interplanar d-spacing of 0.35 nm for Cd3P2 and 0.33 nm for Zn3P2, corresponding to that of the {202} lattice planes of tetragonal Cd3P2 and Zn3P2, respectively. Besides the pure nanotubes, some partially filled nanotubes were also observed. Series of experimental results give a self-sacrificing template mechanism of these nanotubes.Cathodoluminescence (CL) properties of II3-V2 nanotubes were briefly studied here at 16 K. Zn3P2 nanotubes with wall thickness of ca. 10 nm, 20 nm and 45 nm, show emissions centered at about 491 nm, 711 nm, and 796 nm, respectively. Great blueshifts were observed for the nanotubes with very thin wall thickness, which are caused by the quantum confinement.[1] (a) Xia, Y.; et al. Adv. Mater. 2003, 15, 353-389. (b) Shen, G. Z.; Chen, D. J. Am. Chem. Soc. 2006, 128, 11762.[2] Shen, G. Z.; et al. Appl. Phys. Lett. 2006, 88, 143105.[3] (a) Shen, G. Z.; et al. Chem. Eur. J. 2006, 12, 2987. (b) Shen, G. Z.; et al. Appl. Phys. Lett. 2006, 88, 243106. (c) Shen, G. Z.; et al. Appl. Phys. Lett. 2006, 88, 123107.[4] Shen, G. Z.; et al. Angew. Chem. Int. Ed. 2006, in press.
Monday PM, April 09, 2007
Room 2003 (Moscone West)
4:45 PM - DD4.8
Multiscale Modeling of Low-Dimensional Quantum Nanostructures in Semiconductors.
Vinod Tewary 1 , David Read 1 , Bo Yang 2
1 Materials Reliability, National Institute of Standards & Technology, Boulder, Colorado, United States, 2 Mechanical and Aerospace Engineering, Florida Institute of Technology, Melbourne, Florida, United States
Show AbstractCurrently there is a strong interest in modeling the characteristics of low dimensional quantum structures such as nanowires, quantum dots, quantum wells, etc., because of their potential application in powerful new devices. Modeling is needed for calculation of lattice distortions in and around nanostructures, interpreting measurements for their mechanical characterization, and for strain engineering of the nanostructures and their self-assembled arrays. A precise knowledge of lattice distortion is necessary for quantum mechanical calculation of electronic wave functions in the core of the nanostructures to determine their electronic and optical characteristics. Conventional modeling techniques based upon continuum mechanics are not applicable to nanostructures because their properties are largely determined by their discrete atomistic structure and nonlinear and quantum effects in their core. A quantum nanostructure embedded in a host has to be modeled at the following scales: (i) the nonlinear core region (sub-nanometer), (ii) the region of the host around the core (nanometer), and (iii) free surfaces and interfaces in the host (macro). Modeling of these structures is thus a multiscale problem that requires linking of length scales. A nanostructure embedded in a host causes lattice distortion, which refers to atomic displacements in and around the nanostructure, and long-range strain and displacement fields in the host. Strain and displacement fields at a free surface of the host can be measured and used to characterize the nanostructure and verify the calculated atomic locations in the core. Strain field determines the elastic energy of the system and is partly responsible for the self-assembly and formation of arrays of the structures. Strain is a continuous variable whereas lattice distortion is a discrete variable that must be calculated by using a discrete lattice theory. Hence we need a multiscale model to calculate the lattice distortion at the atomistic scale and relate it to a measurable parameter such as strain at the macroscale.We have developed a computationally efficient multiscale model for calculation of strains and displacements in and around nanostructures, by integrating molecular dynamics with Green’s functions. We use molecular dynamics at the core of the nanostructure to account for the nonlinear discrete lattice effects, and lattice statics Green’s function for the host lattice. The lattice statics Green’s function reduces asymptotically to the continuum Green’s function, which links the atomistic scales to macroscales for interpretation of measurements. The model is applied to a Ge nanowire and a quantum dot embedded in a Si host containing a free surface. Numerical results will be reported for atomistic distortion in and around a nanostructure, its strain field at the free surface, and its elastic interaction with the surface.
DD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
5:00 PM - DD3.10/EE2.10
PLD Synthesis of Aligned Fe3O4 and ε-Fe2O3 Nanowires and Nanobelts.
Jenny Morber 1 , Yong Ding 1 , Michael Haluska 1 , Yang Li 2 , J. Liu 2 , Zhong Wang 1 , Robert Snyder 1
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Physics, University of Texas at Arlington, Arlington, Texas, United States
Show AbstractMonday PM, April 09, 2007
Room 2003 (Moscone West)
5:00 PM - DD4.9
Chemical Tension in VLS Nanostructure Growth Process: From Nanohillocks to Nanowires.
Na Li 1 , Ulrich Gösele 2 , Teh Tan 1
1 Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina, United States, 2 , Max-Planck Institute of Microstructure Physics, Halle Germany
Show AbstractWe formulate a global equilibrium model to describe the growth of 1-d nanostructures in the VLS process by including also the chemical tension in addition to the physical tensions, i.e., surface energies. The chemical tension derives from the Gibbs free energy change due to the growth of a crystal layer of an elementary thickness. The system global equilibrium is arrived at via the balance of the static physical tensions and the dynamic chemical tension. The model predicts, and provides conditions for the growth of nanowires of all sizes exceeding a lower thermodynamic limit. The model also predicts the conditions distinguishing the growth of nanaohillocks from nanowires. These predictions will allow verifying the model by future experiments specifically designed for this purpose.
DD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
5:15 PM - DD3.11/EE2.11
Pulsed-Potential Regimes for the Electrodeposition of Bismuth Telluride Nanowires in Porous Alumina.
Lynn Trahey 1 , Catherine Becker 1 , Jeff Sharp 2 , Angelica Stacy 1
1 Chemistry, University of CA, Berkeley, Berkeley, California, United States, 2 , Marlow Industries, Inc., a Subsidiary of II-VI Incorporated, Dallas, Texas, United States
Show AbstractMonday PM, April 09, 2007
Room 2003 (Moscone West)
5:15 PM - DD4.10
Growth Mechanism of Group III-Nitride Nanorods Using Hydride Vapor Phase Epitaxy
Yong Sun Won 2 1 , Young Seok Kim 2 , Olga Kryliouk 2 , Tim Anderson 2
2 Chemical Engineering, University of Florida, Gainesville, Florida, United States, 1 Guest Scientist, Metallurgy, MSEL, NIST, Gaithersburg, Maryland, United States
Show AbstractA convincing mechanism for catalyst- and template-free InN and GaN nanorod growth using HVPE was proposed, featured with the random nanoparticle nucleation from stable gas phase oligomers ([Cl2InNH2]n or [Cl2GaNH2]n) and the subsequent directional growth along the c-axis. The involvement of group III-trichloride (InCl3 or GaCl3) as a key intermediate required HCl/group III ratio to be above 3 by stoichiometry. A combined study of equilibrium thermodynamics and computational thermochemistry suggested that the best growth zone of group III-nitride nanorods lies in the vicinity of the growth-etch transition. As for the GaN nanorod growth, a two-temperature approach was recommended due to the high activation barrier for GaCl3 formation; high temperature for GaCl3 formation and low temperature for GaN nanorod growth via the proposed mechanism. Theoretically resolved operation conditions – temperature and HCl/group III ratio – for group III-nitride nanorod growth showed a good agreement with experimental results.
DD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
5:30 PM - DD3.12/EE2.12
Microwave-assisted Rapid Synthesis of Silver Nanowires.
Linfeng Gou 1 , Jeffery Zaleski 1
1 , Indiana University , Bloomington, Indiana, United States
Show AbstractWe report the rapid, microwave-assisted aerobic synthesis of silver nanowires based on the polyol method. Benchtop dissolution of NaCl and AgNO3 in ethylene glycol and subsequent heating using microwave irradiation (300W) in the presence of polyvinylpyrrolidone generates Ag nanowires in ~80% yield in 3.5 minutes. Upon purification, microscopy (TEM, SEM) and powder X-ray diffraction reveal a uniform array of crystalline Ag nanowires 45 nm x 4-12 mm. Wire formation is highly dependent upon the microwave heating power, time, and NaCl:AgNO3 ratio due to the rapid heating process and the presence of O2 as an etching coreagent. The nanowire formation mechanism, particularly the role of microwave irradiation as compared to the traditional heating techniques, will be presented. The microwave assisted preparation does not require any external seed crystals, precursors, or mechanical stirring, and is conducted under ambient O2 conditions, leading to significant potential for the large-scale fabrication of Ag nanowires using this approach. Additionally, the rapid heating feature of microwave can be adapted to many hydrothermal/solvothermal approaches for preparing other 1-D nanostructures. Specific examples of these nanowire materials will be discussed.
Monday PM, April 09, 2007
Room 2003 (Moscone West)
5:30 PM - DD4.11
Composition and Strain Dependence of the Piezoelectric Coefficients in Semiconductor Alloys.
Max Migliorato 1
1 Electronic and Electrical Engineering, University of Shefield, Sheffield United Kingdom
Show AbstractDD3/EE2: Joint Session: Synthesis of Nanotubes and Nanowires II
Session Chairs
Monday PM, April 09, 2007
Room 2001 (Moscone West)
5:45 PM - DD3.13/EE2.13
Multicolor Nanolasers from Individual Multi-quantum Well Nanowire Heterostructures.
Fang Qian 1 , Yat Li 1 , Silvija Gradecak 1 , Hong-Gyu Park 1 , Yong Ding 2 , Zhong Lin Wang 2 , Charles Lieber 1
1 Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States, 2 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractMonday PM, April 09, 2007
Room 2003 (Moscone West)
5:45 PM - DD4.12
Modeling and Experimental Investigation of Nanometer Scale Cold Field Emitters For Multi-length Scale Integration
Darrell Niemann 1 2 , Bryan Ribaya 1 2 , Norman Gunther 1 , Mahmud Rahman 1 , Cattien Nguyen 1 3 , Joseph Leung 2
1 Electrical Engineering, Santa Clara University, Santa Clara, California, United States, 2 , NASA Ames Research Center, Moffett Field, California, United States, 3 , ELORET/NASA Ames Research Center, Moffett Field, California, United States
Show AbstractWe develop a novel modeling technique based on Technology Computer Aided Design (TCAD) in parallel with experimental results to investigate the field emission properties of individual carbon nanotubes (CNTs). Particular emphasis is placed on the optimization of integrating CNT as an electron source in electron microscopy. CNT based field emitters are promising for field emission applications because of their inherently high brightness, low energy spread, and low operating voltages [1,2]. We demonstrate a robust computational methodology capable of investigating the large-scale integration of individual CNT field emitters, thus enabling multi-length scale structural optimization specifically for designing an efficient electron source. This paper presents experimental field emission data for two structurally well-defined cathode structures: one composed of a multi-walled carbon nanotube (MWNT), acting as a nano-scale emitter, attached to an etched Ni metal wire and the other composed of a MWNT attached to a flat Ni-coated Si microstructure. Although both incorporate CNTs with similar geometries, they exhibit quite different macroscopic turn-on fields of 1.6 and 2.5 V/μm, respectively. The effect of overall cathode structure on the electrostatic fields at the tip of the nano-scale emitter is directly investigated by TCAD simulation. TCAD results for cathode structures analogous to those in experiments exhibit a trend similar to that observed experimentally. In order to achieve the typical microscopic turn-on field of 1x109 V/m at the nano-scale emitter tip, the two different structures require macroscopic turn-on fields of 1.4 and 2.4 V/µm, respectively [3,4]. Furthermore, TCAD simulation results reveal that the magnitude of the microscopic field varies with the area of the supporting structure. This study demonstrates quantitatively that the supporting cathode structure effect must also be considered in the analysis of field emission properties of nanoscale emitters. Based on these results, TCAD is concluded to be an effective tool for investigating the multiple-length scale integration of nanoscale emitter. Such computer aided techniques enable the exploration of the challenges presented by large scale integration.1.B. Ribaya, D. Niemann, N. Gunther, M. Rahman, C. V. Nguyen, Proc. IVEC/ IVESC, pp. 25-3-4, (2006).2.N. de Jonge and J.-M. Bonard, Phil. Trans. R. Soc. Lond. A 362, 2239 (2004).3.N. de Jonge, M. Allioux, M. Doytcheva, M.K. Philips, K.B. K. Teo, R.G. Lacerda, and W.I. Milne, Appl. Phys. Lett. 85, 1607 (2004).4.J. Cumings, A. Zettl, M. R. McCartney, J. C. H. Spence, Phys. Rev. Lett. 88, 56804 (2002).
Symposium Organizers
Moonsub Shim University of Illinois, Urbana-Champaign
Masaru Kuno University of Notre Dame
Xiao-Min Lin Argonne National Laboratory
Ruth Pachter Air Force Research Laboratory
Sanat Kumar Rensselaer Polytechnic Institute
DD5: Properties of Nanocrystals
Session Chairs
Philippe Guyot-Sionnest
Moonsub Shim
Tuesday AM, April 10, 2007
Room 2001 (Moscone West)
9:00 AM - DD5.1
The Role of Particle Size Volume Fraction in Bimodal Metals for Optimized Mechanical Properties at Varying Temperatures.
Tammy Smith 1 , Alla Sergueeva 1 , Umberto Anselmi-Tamburini 1 , Amiya Mukherjee 1
1 Chemical Engineering and Materials Science, UC Davis, Davis, California, United States
Show Abstract9:15 AM - DD5.2
Structural and Magnetic Properties of Self-Assembled Gold Nanoparticles in Alumina Thin Films
Jeremiah Abiade 1 , Dhananjay Kumar 1 2
1 Mechanical & Chemical Engineering, North Carolina A&T State University, Greensboro, North Carolina, United States, 2 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show Abstract9:30 AM - **DD5.3
Surface Functionalization of Semiconductor Nanostructures.
Alf Mews 1 , Ma Xuedan 1 , Zhou Xiaoyin 1 , Maxime Tchaya 1 , Lars Birlenbach 1
1 Physical Chemistry, University of Siegen, Siegen Germany
Show Abstract10:00 AM - DD5.4
Hydroxyl-Quenching Effects on the Photoluminescence Properties of SnO2:Eu3+ Nanoparticles.
Taeho Moon 1 , Dae-Ryong Jung 1 , Sun-Tae Hwang 1 , Dongyeon Son 1 , Jongmin Kim 1 , Myunggoo Kang 1 , Byungwoo Park 1
1 Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractFor display devices, such as plasma display panel (PDP), field emission display (FED), etc., nanophosphors have potential advantages over traditional micron-sized phosphors. However, nanoparticles have generally showed poor luminescence efficiencies, and one possible reason for this is hydroxyl quenching due to the presence of some adsorbates during the synthesis of the nanoparticles. Hydroxyl-quenching effects were reported for rare-earth ions and nanoparticles suspended in water. However, reports on the characterizations of phosphor itself have been rare, and it is easily expected that hydroxyl quenching will largely depend on the thermal histories of the nanoparticles. The effects of hydroxyl quenching were examined on the photoluminescence properties of SnO
2:Eu
3+ nanoparticles. High-quality SnO
2:Eu
3+ nanoparticles were synthesized from SnCl
4, EuCl
3, and ethylene glycol (C
2H
6O
2) by a solvothermal method. The photoluminescence spectra showed a reddish orange emission, which gradually increased with the calcination temperature in the range from 700°C to 1000°C. As the calcination temperature varied, the change of the OH
-/O
2- integrated-intensity ratios from XPS corresponded qualitatively with that of the photoluminescence intensities. The samples obtained after the hydrothermal treatment and after reheating, respectively, exhibited a decline and recovery of their emission intensities, and this behavior with XPS confirmed the hydroxyl-quenching effect. Corresponding Author: Byungwoo Park:
[email protected]10:15 AM - DD5.5
Synthesis and Photoluminescence of Mn-Doped Zinc-Sulfide Nanoparticles.
Dongyeon Son 1 , Dae-Ryong Jung 1 , Jongmin Kim 1 , Taeho Moon 1 , Byungwoo Park 1
1 Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractZinc sulfide (ZnS) is an important luminescence material with a wide band gap, and widely used in flat-panel displays, infrared windows, sensors, etc. Since the first paper of Mn-doped ZnS (ZnS:Mn) nanoparticles in 1992, many researchers have investigated the synthetic techniques, luminescence properties, and applications. However, there are few reports on the Mn-concentration effects with considering the crystallinity and capping elements. In this work, ZnS:Mn nanoparticles were synthesized using a liquid-solid-solution (LSS) method, as a simple synthetic route for preparing ~7 nm-sized monodisperse nanocrystals. The influence of doping concentration for optimum luminescence properties was studied with the actual Mn concentration, the non-uniform distribution of local strain, and the capping effect. The improved photoluminescence intensity of the 450°C-annealed samples with 1.0 at. % Mn doping is attributed to both the removal of water/organics and the enhanced crystallinity (reduced local strain). Corresponding Author: Byungwoo Park:
[email protected]10:45 AM - DD5.6
Parity Forbidden Transitions in PbSe Nanocrystals
Jeffrey Peterson 1 , Todd Krauss 1
1 Dept of Chemistry, University of Rochester, Rochester, New York, United States
Show AbstractOver the last 20 years, semiconductor nanocrystals (NCs) have enabled exciting visualizations of quantum confinement effects in low dimensionality materials, motivating both fundamental and technological investigations of their size-tunable electronic and optical properties. Using a simple “particle in a sphere” model and traditional selection rules, one can essentially understand the major features and the size-dependence of NCs’ electronic structure. Due to their extremely large electron and hole Bohr radii, lead salt NCs (PbSe, PbS, and PbTe) can achieve levels of quantum confinement that are not possible in other materials and thus are ideal systems to study confinement effects. Indeed, their absorption spectra indicate a series of well defined and widely spaced energy levels that can be tuned throughout the near infrared spectral region. However, despite this spectral simplicity, theory continues to fail to explain the presence of a dipole-allowed transition at the second excitonic absorption feature in the spectrum. Interestingly, this second peak energy is accurately predicted if formally parity-forbidden transitions are allowed, although it remains unclear what causes such a strong symmetry breaking in the NC. Conversely, recent scanning tunneling spectroscopy investigations suggest that previous theoretical models are inaccurate and that the second absorption peak originates from an allowed transition. We will present investigations of PbSe NC electronic structure using two-photon photoluminescence excitation spectroscopy. The idler beam of an optical parametric amplifier pumped by a Ti:sapphire regenerative amplifier was used to excite, via a two-photon process, PbSe NC samples with (one-photon) absorption peaks between 1200–1450 nm. In all four sizes of PbSe NCs studied, the first two-photon allowed optical transition occurs at the energy of the second, one-photon absorption peak. Unlike one-photon excitation, two-photon processes formally allow mixed parity transitions. Thus, the two-photon excitation data provides direct evidence that the second absorption peak originates from a mixed parity transition. Accordingly, we assign this peak as a “1S–1P” transition. We propose that the molecular origin of this symmetry breaking is due to faceting of the NC faces, which can result in the creation of a permanent dipole in the NC and, thus, alters the wavefunction symmetry. We will present recent experimental and theoretical investigations relevant to this hypothesis. Similar parity-forbidden transitions have been observed in other materials. However, the parity-forbidden transition energies closely overlap with the allowed transition energies and are thus obscured due to “spectral congestion.” In contrast, the wide spacing of transitions in PbSe NCs provides a striking example of this phenomenon and highlights the critical role of the NC surface reconstruction in determining their fundamental properties.
11:00 AM - **DD5.7
New Paradigm for Nanocrystal Lasing Using Engineered Exciton-Exciton Interactions
Victor Klimov 1
1 Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractChemically synthesized semiconductor nanocrystals (NCs) are almost perfect emitters that combine size-controlled tunability of emission color with near-unity photoluminescence quantum yields. Paradoxically, despite these favorable light-emitting properties, NCs are difficult to use in optical amplification and lasing. Because of exact balance between absorption and stimulated emission in NCs excited with single electron-hole pairs (excitons), optical gain can only occur due to the NCs that contain at least two excitons. A complication associated with this multiexcitonic nature of light amplification is fast, picosecond optical-gain decay due to nonradiative, exciton-exciton Auger recombination. Here, we demonstrate a practical approach for obtaining NC optical gain in the single-exciton regime, which completely eliminates the problem of ultrafast Auger decay. Specifically, we develop core/shell hetero-NCs that produce efficient spatial separations between electrons and holes resulting in generation of a strong local electric field. This field induces a giant (~100 meV) transient Stark shift of the absorption spectrum with respect to the luminescence line in singly excited NCs, which breaks the exact balance between absorption and stimulated-emission. We use this effect to demonstrate for the first time optical amplification in NCs due to single-exciton states.
11:30 AM - DD5.8
Dopant-Carrier Exchange Interactions in Colloidal Doped Semiconductor Nanocrystals.
Daniel Gamelin 1
1 Chemistry, University of Washington, Seattle, Washington, United States
Show AbstractThe generation and manipulation of electron spins in magnetic semiconductor nanostructures is a central theme of the emerging field of spintronics. Carrier-dopant magnetic exchange interactions in diluted magnetic semiconductors provide the basis for many important magneto-electronic phenomena, including carrier-mediated ferromagnetism, magnetic polaron nucleation, and proposed spin-based quantum information processing schemes. This talk will describe our group's recent investigations into the use of photochemical carrier generation and magneto-optical spectroscopies to probe carrier-dopant interactions in colloidal diluted magnetic semiconductor quantum dots.Related references:(1) Norberg, N. S.; Parks, G. L.; Salley, G. M.; Gamelin, D. R. "Giant Excitonic Zeeman Splittings in Co2+-doped ZnSe Quantum Dots." J. Am. Chem. Soc., 2006, 128, 13195-13203.(2) Liu, W. K.; Whitaker, K. M.; Kittilstved, K. R.; Gamelin, D. R. "Stable Photogenerated Carriers in Magnetic Semiconductor Nanocrystals." J. Am. Chem. Soc., 2006, 128, 3910-3911.(3) Norberg, N. S.; Kittilstved, K. R.; Amonette, J. E.; Kukkadapu, R. K.; Schwartz, D. A.; Gamelin, D. R. "Synthesis of Colloidal Mn2+:ZnO Quantum Dots and High-TC Ferromagnetic Nanocrystalline Thin Films." J. Am. Chem. Soc., 2004, 126, 9387-9398.(4) Schwartz, D. A.; Norberg, N. S.; Nguyen, Q. P.; Parker, J. M.; Gamelin, D. R. "Magnetic Quantum Dots: Synthesis, Spectroscopy, and Magnetism of Co2+- and Ni2+-Doped ZnO Nanocrystals." J. Am. Chem. Soc., 2003, 125, 13205-13218.(5) Norberg, N. S.; Dalpian, G. M.; Chelikowsky, J. R.; Gamelin, D. R. "Energetic Pinning of Magnetic Impurity Levels in Quantum Confined Semiconductor Nanocrystals." Nano Letters, in press.
11:45 AM - DD5.9
Effect of Er Doping on the Electronic and Optical Properties of Group IV Nanoparticles.
Anthony van Buuren 1 2 , Rob Meulenberg 1 , Trevor Willey 1 , April Montoya Vaverka 1 3 , Lou Terminello 1
1 , LLNL, Livermore, California, United States, 2 Dept. of Natural Sciences, UC Merced, Merced, California, United States, 3 Department of Materials Science , UC Davis, Davis, California, United States
Show Abstract12:00 PM - **DD5.10
Photoluminescence of Charged Colloidal Quantum Dot.
Philippe Guyot-Sionnest 1 , Praket Jha 1
1 , University of Chicago, Chicago, Illinois, United States
Show Abstract12:30 PM - DD5.11
Solution-Phase Single Quantum Dot Fluorescence Resonant Energy Transfer: Probing Nanoparticle-Conjugate Heterogeneity
Thomas Pons 1 , Igor Medintz 2 , Xiang Wang 3 , Doug English 3 , Hedi Mattoussi 1
1 Optical Sciences Division, Code 5611, Naval Research Laboratory, Washington, District of Columbia, United States, 2 Dept. of Chemistry & Biochemistry, University of Maryland, College Park, Maryland, United States, 3 Center for Bio/Molecular Science and Engineering, Code 6900, Naval Research Laboratory, Washington, District of Columbia, United States
Show AbstractLuminescent semiconductor nanocrystals, or quantum dots (QDs), offer several advantages over traditional organic dyes for use in both in vitro assays and in vivo cellular and animal imaging. As methods are developed to conjugate biomolecules to QDs, and as these nano-assemblies find increasing applications in biological sensing and imaging, there is a growing need for characterization of QD-biomolecule conjugate heterogeneity. Compared to ensemble measurements, single molecule studies are able to resolve molecular scale heterogeneities in macroscopically homogeneous samples (e.g. a dispersion of nanoparticles). Here, we present a single particle QD-based fluorescence resonance energy transfer (spFRET) study that allows us to probe the heterogeneity in QD-dye labeled protein conjugates. We first show that QDs are compatible with spFRET detection by demonstrating the equivalence of single particle and ensemble measurement modalities in terms of derived average FRET efficiencies and separation distances between a central QD donor and dyes attached to specific sites on conjugated proteins. We then use spFRET data to demonstrate that the distribution of QD-protein conjugate valence follows Poisson statistics.1 We finally apply spFRET to characterize heterogeneity in the interactions between single QD-maltose binding protein (QD-MBP) sensing assemblies with their target maltose. In particular, we show that in a macroscopically homogeneous sample two distinct sensor populations coexist: one is composed of maltose-free QD-MBP conjugates and the other of QD-MBP-maltose complexes. The fraction of QD-MBP bound to its target varies with maltose concentration, and the binding constant derived from spFRET is consistent with the one derived from ensemble measurements.1 T. Pons, I.L. Medintz, X. Wang, D.S. English, and H. Mattoussi, J. Am. Chem. Soc., ASAP (2006).
12:45 PM - DD5.12
Indirect Excitation of Er in Si Rich SiO2 Films – Defects vs. Nanocrystals.
Oleksandr Savchyn 1 , Forrest Ruhge 1 , Pieter Kik 1 , Ravi Todi 2 , Kevin Coffey 2
1 College of Optics and Photonics: CREOL & FPCE , University of Central Florida, Orlando, Florida, United States, 2 School of Electrical Engineering and Computer Science, University of Central Florida, Orlando, Florida, United States
Show AbstractErbium doped silicon rich silica is currently investigated intensively as a gain medium for the fabrication of a silicon compatible laser. Erbium ions (Er3+) in SiO2 exhibit an optical transition at 1.54 μm that can provide optical amplification and gain. However due to the low absorption cross section, high pump powers and resonant excitation are generally required to achieve population inversion. One of the possible ways of increasing the erbium absorption cross section is by means of sensitization with silicon nanocrystals. It is well known that excitons confined in Si nanocrystals can efficiently excite erbium, enhancing the effective optical absorption cross section by orders of magnitude. Recently there has been substantial debate about the merits of including large nanocrystals, and several papers have suggested that many smaller clusters would provide better gain performance. This presentation discusses the results of an annealing study carried out to correlate the formation of Si nanocrystals with the efficiency of indirect excitation. Surprisingly, significant indirect erbium excitation is observed at annealing temperatures well below the temperature required to form Si nanocrystals. These results suggest that efficient Er sensitization could be obtained with reduced annealing temperatures and/or shorter annealing times. Samples with an Er concentration of 0.63 at.% and a Si excess concentration of 12 at.% were prepared using magnetron cosputtering from Si, SiO2 and Er2O3:SiO2 targets. The samples were subsequently annealed in N2 or H2:N2 atmospheres at temperatures in the range of 3000C-12000C. Indirect erbium excitation was observed at annealing temperatures as low as 3000C, and excitation spectroscopy in the range 350-700 nm revealed broadband Er sensitization. Reference samples that did not contain excess Si did not exhibit indirect excitation at any annealing temperature. When excited at 476 nm, maximum Er photoluminescence (PL) intensity was obtained for an annealing temperature of 5000C. At temperatures above 9000C a broad visible luminescence band with a peak in the range of 740 - 800 nm appears, indicating the formation of Si nanocrystals. Contrary to what might be expected, this is accompanied by a strong reduction of the indirectly excited Er photoluminescence intensity, suggesting that nanocrystal formation is accompanied by a significant reduction of the erbium active fraction. The implications of these results for Si based Er doped gain media are discussed.
DD6: Properties of Nanorods
Session Chairs
Tuesday PM, April 10, 2007
Room 2001 (Moscone West)
2:30 PM - **DD6.1
Surface Induced Localized Charge of Single Imperfect CdSe Quantum Rods
Todd Krauss 1 , Rishikesh Karishnan 4 , Philippe Fauchet 4 , Zhiheng Yu 3 , Sara Maccagnano 2 , Joaquin Calcines 1 , Julie Smyder 1 , John Silcox 2
1 Chemistry, University of Rochester, Rochester, New York, United States, 4 Electrical and Computer Engineering, University of Rochester, Rochester, New York, United States, 3 Physics, Cornell University , Ithaca, New York, United States, 2 Applied Physics, Cornell University , Ithaca, New York, United States
Show AbstractThe photophysical properties of semiconductor nanoparticles as a function of their size have been the subject of much interest over the past decade. However, significantly less attention has been paid to the influence of shape, and in particular surface morphology, on these same properties. Unlike macroscopic materials, where the surface to volume ratio is negligibly small, in nanoparticles the detailed surface structure can have a significant influence on particle behavior and in some cases can lead to completely unexpected phenomena. We will present measurements of the local electrostatic properties of colloidal semiconductor quantum dots (QDs) and quantum rods (QRs), and their influence on their photophysical properties, down to the single particle level. In particular, electrostatic force microscopy (EFM) was used to determine that single CdSe quantum rods (QRs) have a permanent polarization surface-charge density, an unexpected observation for supposedly well-shaped, neutral dielectric particles. To investigate the source of the surface charge, we performed high-resolution surface morphology as well as high-resolution electron nanodiffraction studies with a scanning transmission electron microscope (STEM). Annual darkfield STEM imaging demonstrated that individual QRs show variations in thickness and shape, including extensive faceting of the nanoparticle surface. In addition, electron nanodiffraction patterns suggest that rotations exist between various ``sections'' of individual QRs, and that the rotation axes may form substantial angles with the c-axis. Thus, we conclude that CdSe QRs are imperfect single crystals, and that the surface charge seen in EFM results from the slight angle between the QR sides and the direction of their internal electric polarization. Interestingly, despite the large dipole moment expected for CdSe QRs, none was observed to within our instrument resolution. The unavoidable presence of permanently charged surfaces on CdSe QRs has the potential to impede the development of novel devices incorporating these materials, as it has been suggested that electric charge on CdSe QDs and QRs causes a quenching of nanoparticle fluorescence. To explore this relationship further, we will also present measurements of the charge magnitude and photoluminescence intensity (obtained simultaneously) for CdSe QDs.
3:00 PM - DD6.2
Rayleigh Instability in Gold Nanorods.
Carolina Novo 1 , Paul Mulvaney 1
1 School of Chemistry, University of Melbourne, Melbourne, Victoria, Australia
Show AbstractThe energy and linewdith of the surface plasmon resonances in metal nanoparticles are strongly determined by the particle shape and size, as well as by the nature of the surrounding medium [1-3]. There is increasing evidence that such nanoscale structures are far more vulnerable to damage by heat and light than the respective bulk metals. Nevertheless, even if they are thermodynamically unstable, they may still be of practical utility if the materials are kinetically stable and unable to respond to external stresses.Rayleigh considered the importance of surface fluctuations on the mechanical stability of liquid droplets. He showed that as a small sphere fluctuates to form ellipsoids due to an external perturbation, there is a critical amplitude beyond which fission becomes possible [4-6]. Such charge induced fragmentation, sometimes called a Coulomb explosion, is well known for liquids and has been studied for over a century. To date, there have been no studies of Rayleigh instabilities in small solid particles. This is partly because of the experimental difficulty in applying significant charge to metal nanorods and the expected slow response time of a solid to the induced stress.In this work we report for the first time clear evidence that nanorods will undergo shape changes in response to double layer charging. The addition of electrons to gold nanorods in water with aspect ratios ranging from 2 to 6 leads to an initial blue shift in the absorption spectrum due to the increasing plasma frequency of the electron gas. However, at longer times, the SPL band red shifts due to changes in particle morphology induced by the surface charge. The particles increase their faceting and develop pointed endcaps. The deformation of the particles is plastic and irreversible.In the case of extreme electron densities, fragmentation is fast enough to compete with redox reactions that would discharge the double layer, so the rods fragment spontaneously leading to the formation of clouds of much smaller spherical gold particles. Though charge induced fragmentation is known from gas phase studies of liquid drops, it has not been previously demonstrated for solids. Our finding that sodium borohydride and to a lesser extent ascorbic acid are capable of causing shape changes in small gold rods is consistent with these gas phase studies. It demonstrates that crystal structure and morphology may be controlled by chemical reactions occurring locally as well as by external perturbations.References1. Nikoobakht, B. and El-Sayed, M.A. Chem. Mater. 2003. 15(10): p. 1957-1962.2. Murphy, C.J., et al. J. Phys. Chem. B 2005. 109(29): p. 13857-13870.3. Mulvaney, P. Langmuir 1996. 12(3): p. 788-800.4. Rayleigh, F.R.S. Phil. Mag. Ser. 1882. 14(5) , p. 184–1865. Chandezon, F., et al. Phys. Rev. Lett. 2001. 8715(15), Art. No. 153402.6. (a) Duft, D., et al. Nature 2003. 421(6919): p. 128-128. (b) Duft, D., et al. Phys. Rev. Lett. 2002. 89(8), Art. No. 084503.
3:30 PM - DD6.4
Synthesis and Characterization of Self-assembled (In,Ga)As Quantum Posts on GaAs.
Jun He 1 , Hubert Krenner 1 , Craig Pryor 2 , Jinping Zhang 1 , Yuan Wu 1 , Dan Allen 3 , Chris Morris 3 , Mark Sherwin 3 , Pierre Petroff 1 4
1 Department of Materials, University of California, Santa Barbara, Santa Barbara, California, United States, 2 Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, United States, 3 Department of Physics, University of California, Santa Barbara, Santa Barbara, California, United States, 4 Department of Electrical & Computer Engineering, University of California, Santa Barbara, Santa Barbara, California, United States
Show Abstract3:45 PM - DD6.5
Local Electronic Property of ZnO Tetrapods
Jong Lee 1 , Junghwan Huh 2 , Gyu Kim 2 , Shareghe Mehraeen 1 , Nigel Browning 1 , Sangtae Kim 1
1 Chemical Engineering and Materials Science, University of California, Davis, Davis, California, United States, 2 Electrical Engineering, Korea University, Seoul Korea (the Republic of)
Show AbstractIn recent years, a large number of one-dimensional nanostructures have been synthesized with precisely controlled chemical compositions, morphologies, and sizes using various synthesis methods for potential applications in a variety of nanoscale devices. These include transistors, memory devices, logics, chemical/bio-sensors and lasers. In view of various distinctive properties of ZnO (a direct bandgap of 3.37 eV at room temperature), nanodevices based on this material hold a lot of promises for, in particular, gas sensing, electronic, optoelectronic applications. ZnO-based nanodevices are also promising candidates for biological applications due to easy fabrication and friendly nature to living organisms.ZnO is also known to have a variety of nanostructures including three-dimensional (3-D) forms such as tetrapods. Unlike one-dimensional single crystalline nanostructures, a tetrapod has a junction at which four legs meet. The junction core can possibly have a different structure from those of the legs such that it may show different electrical behavior. By measuring a dc current flowing through two legs across the junction (leg-junction-leg), however, one cannot distinguish between electrical contribution of the junction and of the legs to the overall resistance.In this contribution, we report the local electrical behavior of a ZnO tetrapod measured at relatively high temperature (>300 C) using an ac impedance spectroscopy technique. The results of detailed structural analysis on the tetrapod using HR-TEM will be also presented.
DD7: Properties of Nanowires I
Session Chairs
Tuesday PM, April 10, 2007
Room 2001 (Moscone West)
4:30 PM - DD7.1
Absorption Anisotropy of Aligned CdSe and CdTe Nanowires
Aidong Lan 1 , Vladimir Protasenko 1 , Masaru Kuno 1
1 Chemistry and Biochemistry, Univ. of Notre Dame, Notre Dame, Indiana, United States
Show AbstractThin (5-15 nm diameter) semiconductor CdSe and CdTe nanowires (NWs) that reside in the intermediate to weak confinement regime exhibit unique optical properties due to their one dimensional (1D) nature. Among them, their linear absorption is of great interest from both scientific and practical perspectives. Although NW absorption cross-sections are large, direct measurements of the optical absorption of single NWs remain a great challenge. If the corresponding absorption spectra of well-isolated wires can be measured, then their 1D nature can be significantly enhanced. Solution-based CdSe and CdTe nanowires are synthesized using a recently developed solution-liquid-solid (SLS) procedure with Au/Bi core/shell catalyst nanoparticles. The NWs exhibit high degree of crystallinity and uniformity as seen through transmission electron microscopy (TEM) characterization of representative ensembles. These wires have radii between 3- 7 nm, comparable with the corresponding bulk exciton Bohr radius of CdSe and CdTe (aB ~ 5.6 nm of CdSe and 7.5 nm of CdTe). NW inter-wire diameter distributions range from 25-30% with intra-wire distributions on the order of 6%. As an intermediate step towards single NW absorption measurements, we chose aligned NWs as a convenient system for direct absorption anisotropy studies. Positive AC dielectrophoresis (DEP) is employed to align CdSe NW ensembles between micro-fabricated gold electrodes. The nanowires rapidly assemble in the AC electric field owning to their large induced dipole. A confocal microscope directly probes the absorption of the aligned NWs using a fiber-based supercontinuum white light source. Absorption spectra in the range from 470 to 900 nm were collected as a function of the incident light polarization angle. The measurements show substantial absorption anisotropies. Specifically, the absorbance when the light polarization is parallel to the NW axis is an order of magnitude greater than absorbance with an orthogonal light polarization/NW axis configuration. In addition, the spectral dispersion of the absorption polarization anisotropy was probed over the full spectral range.
4:45 PM - **DD7.2
Fluorescence Behavior of Colloidal Semiconductor Quantum Wires.
John Glennon 1 , Rui Tang 1 , Richard Loomis 1 , William Buhro 1
1 Dept. of Chemistry, Washington University, St. Louis, Missouri, United States
Show AbstractWe are studying the fluorescence and fluorescence intermittency (blinking) of CdSe quantum wires by single-wire imaging and spectroscopy. Band-edge fluorescence intensities from CdSe wires are enhanced significantly by a reversible photobrightening process, and by exposure to certain surface-capping molecules. We have found that most wires exhibit a "twinkling" phenomenon, in which the fluorescence intensity in small, localized wire domains fluctuates independently of similar fluctuations in nearby domains. However, a persistent fraction of the wires exhibits synchronous blinking over large wire segments (lengths > 500 nm), or even over whole wires (lengths > 2 μm). Significantly, the blinking dynamics follow inverse-power-law statistics comparable to previous findings for quantum dots, suggesting mechanistic similarities between dot and wire blinking. A new mechanism for the reversible photobrightening and blinking will be proposed that is based on the photochemical filling of surface trap sites. The new mechanism is supported by theoretical simulations, which will also be presented. The temperature dependence of the fluorescence behavior in CdSe and other quantum wires may also be presented.
5:15 PM - DD7.3
Far-Field Imaging of Optical Second-Harmonic Generation in Single GaN Nanowires.
Jim Long 1 , Blake Simpkins 1 , David Rowenhorst 2 , Pehr Perhsson 1
1 Surface Chemistry, Naval Research Lab, Washington, District of Columbia, United States, 2 Materials Science and Technology, Naval Research Lab, Washington, District of Columbia, United States
Show AbstractThe nonlinear optical (NLO) response of nanostructured materials is of current interest because of the need for active elements in nanophotonic applications, and because the nonlinear response itself can serve as a useful diagnostic for intense nanoscale plasmonic fields or for the nanostructure itself. A nanostructure of particular interest is the semiconducting nanowire (NW), which can serve as a “self-wired” nanoLED, laser, or photoconductive detector. Here we report an investigation of femtosecond-induced second-harmonic generation (SHG) in GaN NWs that correlates far-field microscopic imaging of the polarization-dependent SHG from individual NWs with electron backscattered diffraction (EBSD) from the same NWs. We find that far-field methods offer an approach for distinguishing the crystallographic orientations of these wurtzite NWs. Because the NLO response of materials depends on the excitation and emission polarizations relative to the crystallographic orientation, single-particle studies are especially valuable for not only avoiding the usual ensemble averaging over variances among individual nanostructures, but also the averaging over angle that can obscure underlying structure in the NLO response of individual particles.The use of far-field microscopic imaging to assess NLO properties of nanomaterials offers flexibility over more complex, albeit powerful, near-field scanning methods, and could serve as a fully optical in-situ diagnostic of crystallographic orientation in surveys of NW collections, in NWs under test, or even in NWs sealed in devices. While a full analysis of the SHG response would require a tedious electromagnetic treatment, we find that the main polarization features of the SHG from these 75-nm diameter NWs are adequately explained by neglecting surface contributions and treating the bulk crystal within the much simpler quasi-static approximation. In the quasi-static approximation, which should prove useful in describing many nanophotonic behaviors, one assumes that the NW transverse dimension is much less than the first and SH wavelengths (here, 860- and 430-nm respectively). Our data also emphasizes the importance of including the transverse depolarization effect, which reduces the component perpendicular to the NW of not only the pump electric-field, but also the 2nd-order polarization P(2ω).
5:30 PM - DD7.4
Orientation-dependent Raman Spectroscopy of Single Wurtzite CdS Nanowires.
Hai Ming Fan 1 , Zhenhua Ni 1 , Yuanping Feng 1 , Zexiang Shen 2
1 physics department, national university of singapore, Singapore Singapore, 2 Physics and Applied Physics, Nanyang Technological University, singapore Singapore
Show Abstract5:45 PM - DD7.5
Piezoelectric Nanowires
Scott Mao 1 , C. Jiang 2
1 Department of Mechanical Engineeringand Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Shenyang Interfacial Material Center, IMR, Shengyang, Liaoning, China
Show AbstractAn atomic force microscopy (AFM) is used to measure the effective piezoelectric coefficient (d33) of individual Li doped ZnO nanobelt lying on conductive surface. Based on references using bulk ZnO and quartz, piezoelectric constant d33 of Li doped ZnO nanobelt is found to be frequency dependent and varies from 14.3pm/V to 26.7pm/V, which is much larger than that for the bulk single crystalline ZnO of 12.4pm/V. The results support the application of Li doped ZnO nanobelts as nano-scale sensors and transducers.
DD8: Poster Session: Assembly, Modeling and Applications
Session Chairs
Sanat Kumar
Masaru Kuno
Xiao-Min Lin
Ruth Pachter
Moonsub Shim
Wednesday AM, April 11, 2007
Salon Level (Marriott)
9:00 PM - DD8.1
Freestanding Polymer Colloid Crystal Wires and Metal Reverse Colloid crystal Wires: Magnetic Field Directed Assembly Behavior
Feng Li 1 , John B. Wiley 1
1 Department of Chemistry and Advanced Materials Research Institute, University of New Orleans, New Orleans, Louisiana, United States
Show Abstract9:00 PM - DD8.10
2D Growth of Nanomeshes in 3D Colloidal Crystal Templates.
Ji Zhou 1 , Ming Fu 1
1 Material Science, Tsinghua University, Beijing, Beijing, China
Show Abstract9:00 PM - DD8.11
Exfoliation and Reassembling Route to Nanoparticle-Lamellar Oxide Hybrid: TiO2-Pillared Layered Manganate.
Joo-Hee Kang 1 , Seung-Min Paek 2 , Jin-Ho Choy 1
1 Division of Nanoscience and Department of Chemistry, Ewha Womans University, Seoul Korea (the Republic of), 2 School of Chemistry, Seoul National University, Seoul Korea (the Republic of)
Show AbstractPillared layered solids are of considerable interest due to their potential applications as secondary lithium battery, electrochromic device, electrochemical sensor, and so forth. Of particular interest, layered manganese oxides show reversible Li ion insertion-deinsertion property, which is appropriate as promising electrode materials for lithium rechargeable batteries. Especially, the high surface area of electrode material could provide facile and effective access of lithium ions to all available sites, resulting in high enhancement of discharge capacity. In this study, we report a novel pillared architecture of colloidal manganate nanosheets with titania nanoparticles via exfoliation and reassembling technique. At first, the layered protonic manganese oxide, H0.13MnO2, was exfoliated in an aqueous solution of tetrabutylammonium (TBA) hydroxide, and then, the obtained exfoliated nanosheets of manganate were reassembled with titania nanoparticles which resulted in highly porous nanohybrid materials. According to the X-ray diffraction (XRD) analysis, TiO2-pillared MnO2 (hereafter abbreviated as TMN-rt) with an interlayer distance of 10.2Å, determined by subtracting 5.2Å for the thickness of the manganate nanosheet from the basal spacing of 15.4Å, is in good agreement with the mean size (ca.10Å) of TiO2 nanoparticles, suggesting the monolayer arrangement of TiO2 nanoparticles in the intersheet region. Moreover, the cross-sectional transmission electron microscopy (TEM) analysis clearly showed that highly ordered pillared structure along the crystallographic a-axis was successfully achieved even after the reassembling reaction, and the lattice expansion of TMN-rt was determined to be 1.55 ± 0.1 nm, which is well consistent with the XRD results. Furthermore, based on the Mn K-edge X-ray adsorption near edge structure (XANES) analysis, the absorption edge energy that can be assigned to transitions from the core 1s level to unoccupied 3d states of the pillaring material is remained unchanged, indicating that the valence states of manganese ions are almost the same. It is evident that the electronic structure and local symmetry of Mn ion were maintained even after exfoliation-reassembling reaction. Finally, preliminary electrochemical charge-discharge measurements indicated that the present nanohybrids showed the enhanced discharge capacity compared to the theoretical value of the physical mixture between TiO2 and MnO2. Such results suggest that highly porous nanohybrid materials fabricated by pillaring method could be useful as a cathode material in lithium secondary batteries.
9:00 PM - DD8.12
Controlling Size, Shape, and Distribution of Platinum Nanoparticles Electrodeposited on Carbon Supports.
S.M.Shahinoor I. Dulal 1 , Chang-Koo Kim 1 , Wonjin Jeon 1 , Chee Burm Shin 1
1 Chemical Engineering, Division of Energy Systems Research, Ajou University, Suwon Korea (the Republic of)
Show AbstractThere is much research interest in carbon supported platinum nanoparticles, especially for their use as catalysts in fuel cells and sensors. A plenty of work has been done to prepare colloidal platinum nanoparticles by chemical reduction using borohydride or other reducing agents. Colloidal nanoparticles, however, need to be supported for their use as catalysts. On the other hand, direct electrochemical reduction of platinum ions on a support is a relatively convenient way to fabricate nanoparticle electrodes. There are some reports on the preparation of supported nanoparticle by electrochemical route. The catalytic activity of these nanoparticles has also been tested. However, the catalytic performance of nanoparticles is crucially dependent on their size and shapes. The dispersion of nanoparticles on the support as well as the support itself also has significant influence on the catalytic performance. Uniformly dispersed smaller particles with uniform size and shape are normally desired for enhanced catalytic activities. But it has been found that the sizes of electrodeposited particles vary significantly and particles tend to agglomerate, resulting in uneven distribution on the support surface. The current work aims to control the size and shape of particles and their distribution on catalyst support. In this work, platinum nanoparticles were grown on carbon support by an electrochemical deposition method from an electrolyte containing chloroplatinic acid. The characterization of the supported nanoparticles has been carried out by electrochemical technique and by XRD, SEM and AFM. The electrocatalytic property of the supported nanoparticles was also tested. We have deposited monodispersed and relatively uniform sized platinum nanoparticles on carbon support. The particles have been found very stable on the support surface. It has also been found that particles size and their distribution can simply be controlled by changing electrochemical parameters. The carbon supported platinum nanoparticle electrodes have shown electrocatalytic activities for electrooxidation of methanol (fuel cell fuel) and hydroquinone & phenol (pollutants in industrial waste).
9:00 PM - DD8.13
Highly Mesoporous TiO2 Nanohybrid as an Electrode for a Lithium Battery.
Seung-Min Paek 1 2 , Joo-Hee Kang 3 , Hyun Jung 3 , Young-Jun Lee 2 , Seong-Ju Hwang 3 , Jin-Ho Choy 3
1 Advanced Materials Applications, Battelle Memorial Institute, Columbus, Ohio, United States, 2 School of Chemistry, Seoul National University, Seoul Korea (the Republic of), 3 Center for Intelligent Nano-Bio Materials, Ewha Womans University, Seoul Korea (the Republic of)
Show AbstractTo fabricate mesoporous electrode materials with delaminated structure, the exfoliated layered titanate in aqueous solution was reassembled in the presence of anatase TiO2 nanoparticles to induce a great number of mesopores and eventually a large surface area of TiO2. No (0l0) peaks corresponding to the layered titanate appear in the X-ray diffraction patterns of reassembled nanohybrids, which suggests that the titanate nanosheets were randomly hybridized with TiO2 nanoparticles without any self-restacking into layered phase. According to the high-resolution transmission electron microscopy images of these nanohybrids, the randomly oriented titanate nanosheets can be seen clearly along with TiO2 nanosol particles with spherical images, indicating that the exfoliated nanosheets are indeed incorporated with anatase TiO2 nanoparticles to form porous materials. From N2 adsorption-desorption isotherms, these nanohybrids are fairly high in specific surface area and in mesoporosity for effective and facile lithium insertion-deinsertion reaction. The BET specific surface area of nanohybrid is greatly enhanced from 13 m2/g (layered protonic titanate) to 190 m2/g (nanohybrid) upon hybridization. Furthermore, the pore size can be tailored within mesopore range by adjusting the ratio between titanate nanosheet and TiO2 nanoparticle. In this regard, the applicability of the present nanohybrid as an electrode material for lithium rechargeable battery has been investigated by monitoring the electrochemical intercalation of lithium. This study clearly demonstrates that the hybridization between layered titanate and TiO2 nanoparticles gives rise to a remarkable enhancement of discharge capacity compared to the capacities of layered titanate, TiO2 nanoparticle, and their physical mixture.
9:00 PM - DD8.14
Electronic Properties of C-face and Si-face SiC 3C/4H Heterostrucutures and Devices.
Jie Lu 1 , Chris Thomas 1 , Mvs Chandrashekhar 1 , Michael Spencer 1
1 Electrical and Computer Engineering, Cornell University, Ithaca, New York, United States
Show Abstract9:00 PM - DD8.15
A New Route to the Production and Patterning of Highly Smooth, Nanometer Thin Zirconium Oxide Films.
Karl Coleman 1 , Scott Watson 1
1 Department of Chemistry, University of Durham, Durham United Kingdom
Show Abstract9:00 PM - DD8.16
Development of a Bath And Optimization of Electrochemical Parameters for the Deposition of Platinum Nanoparticles on Graphite.
S.M.Shahinoor I. Dulal 1 , Tae Ho Kim 1 , Hyeong Jin Yun 1 , Chang-Koo Kim 1 , Chee Burm Shin 1
1 Chemical Engineering, Division of Energy Systems Research, Ajou University, Suwon Korea (the Republic of)
Show AbstractPlatinum nanoparticle electrodes find applications in fuel cells, sensor development, and industrial waste treatment. There are many ways to prepare platinum nanoparticles such as chemical reduction, sol-gel, electrodeposition, etc. Nanoparticles prepared by chemical reduction or sol-gel methods need to be supported on suitable surfaces for their use as catalytic electrodes while electrochemical deposition of platinum nanoparticles directly on a support is a cheap, convenient, and efficient way to fabricate electrodes. The uniform distribution of nanoparticles plays an important role in determining their catalytic activity. It is, however, very difficult to obtain evenly dispersed and uniformly sized nanoparticles using electrodeposition. In the present study, we have developed an experimental system and a methodology to electrodeposit platinum nanoparticles with relatively uniform size and shape directly onto a graphitic carbon substrate. Carbon has been found most suitable support for platinum nanoparticles for their use as catalytic electrodes in fuel cells. Deposition conditions have been determined and optimized by electrochemical experiments such as cyclic voltammetry. We have been able to deposit nearly monodispersed and evenly distributed platinum nanoparticles onto the carbon support from a bath containing chloroplatinic acid. It has been found that the particle size and distribution can be controlled by changing bath compositions and electrochemical parameters. The catalytic property of the carbon supported platinum nanoparticle electrodes has also been tested for the oxidation of methanol and phenol.
9:00 PM - DD8.17
Broadband Asymmetric Mirrors using Metal-dielectric Nano-composite Coatings
Aiqing Chen 1 , Keisuke Hasegawa 1 , Miriam Deutsch 1
1 , University of Oregon, Eugene, Oregon, United States
Show AbstractAn asymmetric mirror is a planar layered optical device exhibiting difference in reflectance of light incident from either side, while its transmittance remains the same. This reflectance asymmetry is due to the different losses in the mirror (in form of absorption as well as scattering,) when the light impinged from opposite direction. Asymmetric mirrors have recently found use in specialized Fabry-Perot interferometer systems. One of the simplest structures for an asymmetric mirror is a thin metal film on a dielectric slab, embedded in a uniform dielectric. The design of asymmetric mirrors previously addressed typically employed a smooth thin metal film on a dielectric substrate or multi-layer thin film stacks. The optical characteristics of these mirrors, such as reflectance asymmetry and the associated bandwidth are typically constrained to a narrow range, due to a limited choice of materials. However, when one of these films is replaced by a semi-continuous and disordered nanocrystalline silver film, the optical response of the nano-composite system could change dramatically, i.e., increasing the reflectance asymmetry, while simultaneously its dispersion is minimized. We report on design and fabrication of broadband asymmetric mirrors using metal-dielectric nano-composite coatings. Basic dispersion engineering principles were applied to model a broadband and large reflectance asymmetry, which was the then inverted to yield the effective permittivity. An effective-medium approach was then implemented to approximate the required optical response function in metal-dielectric nano-composites. These nano-composites with engineered permittivities were realized from semi-continuous and disorder silver films deposited on glass substrates using a variation of Tollen’s reaction. The morphology and average thickness ranged from 20-50 nm were characterized under high resolution scanning electron microscope (SEM) and atomic force microscope (AFM). Optical reflectance and transmittance spectra from samples with filling fraction ranged from 10% up to 90% were obtained and properly normalized. Various degree of reflectance asymmetry and their strong dependence on the surface coverage were observed. Nevertheless, the transmittance always remained symmetric, even for rough films with high surface coverage. The most noticeable feature is the flat (non-dispersive) and strongly enhanced (five times larger than smooth thin film,) reflectance asymmetry in the visible and near infrared, which experimentally demonstrated our theoretical prediction of a broadband asymmetric mirror.Details of the physical mechanism of asymmetric mirrors, as well as their potential applications will be addressed.
9:00 PM - DD8.18
Enhanced Tunneling through sub 30 Angstroms thick Gallium Nitride Cap Layers on Silicon Carbide for Low Contact Resistance
Choudhury Praharaj 1 2
1 , Intel Corporation, Santa Clara, California, United States, 2 ( formerly with ) Department of Electrical and Computer Engineering, (formerly with ) Cornell University, Ithaca, New York, United States
Show AbstractWe present numerical calculations of tunneling through ultra thin Gallium Nitride cap layers on p-doped silicon carbide, from the two-dimensional hole gas accumulation regime to the pure depletion regime. We demonstrate the predominance of thermionic field-emission of the split-off holes to the total carrier flux, despite their low occupation factors in the Fermi-Dirac statistics. The contribution of the heavy and the light holes is damped by the large potential barrier. We calculate the contributions of spontaneous and piezoelectric polarizations to the tunneling profile seen by the holes. An enhancement of two orders of magnitude is seen in the transmission probabilities for a 10 angstroms thick Gallium Nitride cap layer for holes very close to the valence band edge, compared to a barrier without any gallium nitride cap. The contact resistances are also calculated for the Gallium Nitride tunneling caps and more than two orders of magnitude lowering is seen with the ultra-thin caps. Larger cap widths induce Two Dimensional Hole Gases, but the advantages of hole accumulation are offset by the higher effective tunneling width. Our calculations are relevant to nanostructures and nanodevices involving heterojunctions between gallium nitride and silicon carbide, and provide the basis for low contact resistances with as-deposited metals. While our calculations focus on the regime of very high bariers to the metal of the order of 1.5 ~ 2 electron volts, where the method of ultra-thin caps is most useful, similar conclusions also hold for lower barrier widths
9:00 PM - DD8.19
Nanogap Fabrication by Pd Hydrogen Embrittlement for Field-Emission Applications.
Fu-Ming Pan 1 , Chih-Hao Tsai 1 , Kuan-Jung Chen 1 , Cheng-Yang Kuo 1 , Mai Liu 2 , Chi-Neng Mo 2
1 Dept. Mat. Sci. Eng., National Chiao Tung University, Hsinchu Taiwan, 2 , Chunghwa Picture Tubes,Ltd, Taoyuan Taiwan
Show Abstract9:00 PM - DD8.2
Hierarchically Organized Nanocrystal Metamaterials Formed through Building Block Self-Assembly.
Hongyou Fan 1 2 , Adam Wright 2 , John Gabaldon 2 , Erik Leve 2 , Darren Dunphy 2 , Jeffrey Brinker 1 2 , Kevin Malloy 2 , Thomas Sigmon 2 , Kai Yang 2
1 , Sandia National Lab, Albuquerque, New Mexico, United States, 2 Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico, United States
Show Abstract9:00 PM - DD8.20
Electrical Properties of a Single TiO2 Nanotubes Depending on Annealing Ambient (vacuum and O2) and Temperature.
Sanghee Won 1 , Kyunghun Jeong 1 , Seunghee Ko 1 , Dongkyu Cha 2 , Moon J. Kim 2 , Jiyoung Kim 2 , Jaegab Lee 1
1 School of Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of), 2 Electrical Engineering, The Univ. of Texas at Dallas, Richardson, Texas, United States
Show Abstract9:00 PM - DD8.21
Dual-gate ZnO Nanowire FETs Aligned by Dielectrophoresis
Seung-Yong Lee 1 , Duk-Il Suh 1 , Tae-Hong Kim 1 , Jung-Hwan Hyung 1 , Ji-Eun Park 1 , Sang-Kwon Lee 1
1 Dept. of Semiconductor Science and Technology, Chonbuk National University, Jeonju Korea (the Republic of)
Show Abstract1D system, for instance nanowires, nanotubes, and nanobelts presenting a fascinating distinctive features and hence representing themselves as a potentially ideal building blocks for nano-electronics and nano-optoelectronics devices. Here, we report that the fabrication and electrical characterization of high performance dual-gate ZnO field-effect transistors such as MOSFET and MESFET. The ZnO nanowires were prepared by AC dielectrophoresis (DEP) method for device alignment. The AC DEP was optimized with a bias voltage of 15 Vp-p at a frequency of 1 kHz. The DEP results indicated that the number of aligned ZnO nanowires increased with increasing AC voltages and ZnO nanowires were well aligned on the metal electrodes (Ti/Au=20/70 nm). For better ohmic contacts to ZnO nanowires, an additional capping layer was formed on the top of the source and drain metals. From the transport measurements of our AC DEP prepared ZnO nanowire FETs, the estimated carrier mobility from the gate-modulation characteristics was on the order of ~ 16 cm2/Vs. The device performances of DEP prepared ZnO nanowire MESFET are also presented.
9:00 PM - DD8.22
Fabrication and Characterization of high-efficiency ZnO Nanowire Dye-Sensitized Solar Cells with a Branched Structure
Dul-Il Suh 1 , Seung-Yong Lee 1 , J. Chun 2 , Tae-Hong Kim 1 , Chan-O Jang 1 , O-Bong Yang 2 , Sang-Kwon Lee 1
1 Dept. of Semiconductor Science and Technology, Chonbuk National University, Jeonju Korea (the Republic of), 2 School of Environment and Chemical Engineering, Chonbuk National University, Jeonju Korea (the Republic of)
Show AbstractOne-dimensional (1D) semiconductor nanowires are especially attractive building blocks for assembling nanometer scale electronic and photonic devices since the individual nanostructures function as both device elements and interconnects. Among the wide range of 1D semiconducting nano-materials, the 1D nanostructures of II-VI semiconductor ZnO acquired a special place because of its diversity in properties, such as direct wide band gap, large saturation velocity, high breakdown voltage and large exciton binding energy at room temperature. Here, we demonstrated the high efficiency dye-sensitized solar cells (DSSC) with a branched structure single-crystalline ZnO nanowire which were grown by two-step vapor-liquid-solid (VLS) process using a hot wall chemical vapor deposition (CVD). To maximize the dye absorption and improve the energy conversion efficiency, we used a branched structure ZnO nanowire in DSSCs. The open-circuit voltage, short-circuit current density, and energy conversion efficiency for a branched structure ZnO nanowire DSSCs were determined to be ~ 0.693V and ~ 1.64 mA/cm2, and ~ 0.54%, respectively from current-voltage characteristics of ZnO nanowire DSSCs. Our results also indicated that current densities and efficiencies improved by increasing the high surface area for dye absorption in DSSCs.
9:00 PM - DD8.23
Magnetic-field Dependence of Valley Splitting for Si Quantum Wells Grown on Tilted SiGe Substrates.
Seungwon Lee 1 , Paul von Allmen 1
1 , Jet Propulsion Laboratory, Pasadena, California, United States
Show Abstract9:00 PM - DD8.25
Computer Simulation of Epitaxial Lateral Overgrowth.
Hee-Soo Kim 1 , Pil-Ryung Cha 2 , Hee Seok Park 1
1 Central R&D Institute, Samsung Electro-Mechanics, Suwon Korea (the Republic of), 2 School of Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - DD8.27
A Simple Phenomenological Model for Growth of Nanodots with ``magical sizes" Stabilized by Quantum Size Effect.
Heikki Ristolainen 1 , Ismo Koponen 1
1 Department of Physical Sciences, University of Helsinki, Helsinki Finland
Show Abstract9:00 PM - DD8.28
Calculation of Photosensitivity of Porous Silicon for Optoelectronic Devices.
Liubomyr Monastyrskii 1 , Bogdan Sokolovskii 1
1 Electronics, Ivan Franko Natl Univ, Lviv Ukraine
Show Abstract9:00 PM - DD8.29
Permittivity in Molecular Nanorods
Sinisa Vucenovic 1 , Dusan Ilic 2 , Jovan Setrajcic 3 , Vjekoslav Sajfert 4 , Dragoljub Mirjanic 1
1 , Medical faculty, University of Banja Luka, Banja Luka Bosnia and Herzegovina, 2 , Faculty of technical sciences, University of Novi Sad, Novi Sad , 3 Departmet of Physics, Faculty of natural sciences, University of Novi Sad, Novi Sad , 4 , Technical faculty "Mihajlo Pupin", University of Novi Sad, Zrenjanin
Show AbstractIn this paper we have theoretically investigated and calculated energy spectra of Frenkel excitons (quasi particles compound of electron-holes pairs linked with Coulomb interaction) and optical properties (dielectric permittivity) in molecular nanorods, i.e. structures limited with two planes (x, y) and practically unlimited in z - direction. We have compared those results with energy spectra and permittivity for bulk (x, y and z direction without limitations) and thin film structures (one limited direction). Method of Green's function was used. Space boundaries and the disturbance of energetic parameters on boundaries are considered as perturbations. In dielectric permittivity calculation, we have used Djalozinski and Pitaevski formula. Compared with bulk structures where excitons could take continual energies in wide zone, thin films demonstrate very sharp selection rules in energy spectra and optical properties. In molecular nanorods, those selections rules and energy shifting are more significant, especially in directions perpendicular on nanorods axis.
9:00 PM - DD8.3
Ordered Monolayer Array of Gold Nanoparticles by Self-Assembly Process on Functionalized Solid Substrates
Geun-Tae Cho 1 , Hye Jin Nam 1 , Ju Yeon Chang 1 , Jong-Hyeon Lee 1 , Duk-Young Jung 1
1 Chemistry, Sung Kyun Kwan Univ., Suwon, Gyeonggi-do, Korea (the Republic of)
Show AbstractTwo-dimensional arrays of gold nanoparticles were prepared in colloidal solutions by self-assembly of 3 nm diameter thiolate-capped colloidal gold particles onto glass, Si wafer and silica grid substrates having amine or thiol functional groups with high affinity for gold. The monolayer film formation involves an exchange, crosslinking, and precipitation among the gold nanoparticles and interparticle linker molecules with two different functionalities, 1,4-butanedithiol (BDT) and 11-murcaptoundacanoic acid (MUA). The amine or thiol functional groups were formed by a vapor deposition of 3-aminopropyltriethoxysilane (APTES) and 3-mercaptopropyltrimethoxisilane (MPTMS) on the substrates. TEM images reveal that the 3 nm diameter gold nanoparticles were assembled with an ordered monolayer on the amine functionalized silica grid, and excess particles were effectively removed form the substrate by ultrasonic treatment. AFM results show that the assembled nanoparticle films on glass surfaces have a uniform roughness of 0.7 nm when the MUA was used as an interparticle linker. The gold monolayers possess a set of features that make them very attractive for various applications, including chemical and biological sensors, devices and so on.
9:00 PM - DD8.30
Electron Energy Spectra of Single and Multiple AlGaN/GaN Quantum Dots with Spontaneous and Piezoelectric Polarization Effects
Choudhury Praharaj 1 2
1 , Intel Corporation, Santa Clara, California, United States, 2 , ( formerly with ) Cornell University, Ithaca, New York, United States
Show AbstractWe present numerical calculations of electron energy spectra of single and multiple coupled quantum dots based on Aluminium Gallium Nitride / Gallium Nitride heterostructures. The effect of spontaneous and piezoelectric polarization on the confinement potential seen by the electrons is taken into account through bound interface sheet charges. We also calculated the spectra without polarization effects for reference. For some quantum dot dimensions, the energy eigenvalues shift by several hundred meVs due to the polarization charges. We calculate the spectra for the two cases of box-shaped and cylindrical quantum dots. The latter case is an approximation to quantum dots with hexagonal-facet shapes recently reported in the literature. The quantum dots in our calculations are surrounded by vacuum in the lateral direction, but the same qualitative conclusions will hold if the dots are embedded in some material, as long as the barrier heights are large. For GaN vertical confinement of less than 30 angstroms, most of the bound states are associated with the lowest eigenvalue of the vertical confinement potential. This is also true for higher vertical confinement dimensions because the triangular potential seen by the electrons is the same for the lowest energy eigenstates. The electric field in the vertical direction is a strong function of the aluminium concentration in the AlGaN layer. As the AlGaN layer composition is varied from very high Al concentration to medium Al concentration, the spectra shift by several hundred meVs, referred to the onset of the continuous spectra. The transition frequencies between bound states and between bound and the lowest continuum states lie in the low to the high infra-red range, and can be varied over a wide range by both the dimensions and the barrier aluminium concentration. For the case of 4 coupled quantum dots formed by repeated AlGaN/GaN heterojunctions, we find that the polarization-induced electric fields lead to excessive band-bending and as a consequence there are fewer bound states compared to the spectrum calculated without polarization effects.
9:00 PM - DD8.32
Melting of Transition Metal Nanoclusters: Application to Carbon Nanotube Synthesis.
Nikhil Joshi 1 , Douglas Spearot 1 2 , Deepak Bhat 1 2
1 MicroEp Program, University of Arkansas, Fayetteville, Arkansas, United States, 2 Mechanical Engineering, University of Arkansas, Fayetteville, Arkansas, United States
Show Abstract9:00 PM - DD8.33
Tetrahedral Silver Nanoparticles Produced by Inert Gas Condensation: An Experimental/simulation Study.
Miguel Gracia Pinilla 1 , Joel Antunez-Garcia 1 , Alfredo Tlahuice-Flores 1 , Carlos Fernandez-Navarro 1 , Sergio Mejia-Rosales 1 , Eduardo Perez-Tijerina 1 , Miguel Jose-Yacaman 2
1 Laboratorio de Nanociencias y Nanotecnología - Facultad de Ciencias Físico Matemáticas, Universidad Autónoma de Nuevo León, San Nicolas de los Garza, Nuevo León, Mexico, 2 Chemical Engineering Department and Texas Advanced Materials Center, The University of Texas at Austin, Austin, Texas, United States
Show Abstract9:00 PM - DD8.36
Chains of Hydrocarbon Molecules Deposited onto Monolayer Steps on Si(100): A study of Adsorption and Conductance.
Anna Mazzone 1
1 , IMM Sezione di Bologna , Bologna Italy
Show Abstract9:00 PM - DD8.38
A Combined Experimental and Theoretical Study of CdSe Nanocrystal Formation
Haitao Liu 1 2 , Jonathan Owen 1 , Jeffrey Grossman 3 , A. Alivisatos 1 2
1 Department of Chemistry, University of California, Berkeley, California, United States, 2 Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Department of Physics, University of California, Berkeley, California, United States
Show AbstractThe synthesis of CdSe nanocrystals using tri-n-alkylphosphine selenide and cadmium carboxylate in n-octadecene has been investigated by experiments and by density functional theory (DFT) calculations to examine the formation of CdSe from the precursors. Binding of tri-n-alkylphosphine selenide to cadmium carboxylate leads to the formation of a metastable complex. A carboxylate molecule then attacks the tri-n-alkylphosphine selenide in the complex to give a pentavalent phosphorus intermediate, which undergoes further reaction to break the P=Se bond and form the initial Cd-Se bond. Our results show that surfactant molecule such as carboxylic acid is also a reagent for the synthesis of CdSe nanocrystals. The activation parameters of the CdSe synthesis were calculated and compared with experimental results.
9:00 PM - DD8.39
Simulating Light Emission in Silicon Nanocrystal Field Effect Light Emitting Devices.
Robert Walters 1 , Douglas Bell 2 , Harry Atwater 1
1 Applied Physics, California Institute of Technology, Pasadena, California, United States, 2 , Jet Propulsion Laboratory, Pasadena, California, United States
Show AbstractAs a low dimensional material, silicon nanocrystals exhibit several fascinating properties including a size tunable emission energy, very high radiative quantum efficiency, and an improved oscillator strength for radiation. These properties recommend silicon nanocrystals as a potential CMOS compatible material for optoelectronics. Unfortunately, the oxide matrix that surrounds a nanocrystal and provides the quantum confinement is also an electrical insulator. This complicates the efficient electrical excitation of silicon nanocrystals.We have previously demonstrated that electroluminescence (EL) can be achieved in silicon nanocrystals within a "field effect light emitting device" (FELED) [1]. These devices resemble nanocrystal FLASH memory devices in which a roughly planar array of nanocrystals is embedded in the gate oxide of a transistor. We observe light emission at bipolar transitions in gate bias. Time resolved EL experiments show EL rise times of order 1 microsecond and EL decay times of order 10 microseconds. These measurements support a model in which excitons are formed by the sequential tunneling of complementary carriers into the nanocrystals. This is a surprising and unexpected result that can be better understood through simulation.Key challenges that must be addressed for this effort include the accurate modeling of both hole and electron tunneling, solving the electrostatics through the self-consistent Poisson-Schrodinger equation, and accounting for the decay processes of excitons in the nanocrystals. We will discuss our simulation of electroluminescence in a model system in comparison to our experimental results.[1] Walters et al., "Silicon Nanocrystal Field Effect Light Emitting Devices", IEEE JSTQE Silicon Photonics Issue, December 2006
9:00 PM - DD8.40
Position Sensitive Growth of Mn Doped ZnO Nanowires on Si Substrate by CVD.
Xiaomei Zhang 1 , Yue Zhang 1 , Yousong Gu 1 , Xiaoyuan Zhan 1 , Ruiping Gao 2 , Kexin Chen 2
1 Department of Materials Physics, University of Science and Technology Beijing, Beijing China, 2 , National Natural Science Foundation of China, Beijing China
Show Abstract9:00 PM - DD8.41
Initial Stages of the Formation of InAs/InP(001) Quantum Wires Studied by High-resolution Z Contrast Imaging.
Sergio Molina 1 2 , Maria Varela 1 , Stephen Pennycook 1 , David Sales 2 , Teresa Ben 2 , Joaquin Pizarro 3 , Pedro Galindo 3 , David Fuster 4 , Yolanda Gonzalez 4 , Luisa Gonzalez 4
1 Materials Science and Technology Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee, United States, 2 Departamento de Ciencia de los Materiales e IM y QI, Universidad de Cadiz, Puerto Real, Cadiz, Spain, 3 Departamento de Lenguajes y Sistemas Informaticos, Universidad de Cadiz, Puerto Real, Cadiz, Spain, 4 , Instituto de Microelectronica de Madrid IMM-CNM, Madrid, Madrid, Spain
Show Abstract9:00 PM - DD8.42
Electrical Characterization and Modeling of Geometry-dependent Resistivity Scaling in Single-walled Carbon Nanotube Films.
Ashkan Behnam 1 , Ant Ural 1
1 Electrical & Computer Engineering , University of Florida, Gainesville, Florida, United States
Show Abstract9:00 PM - DD8.43
Ferroelectricity in Ultra-thin BaTiO3 Films by LEED I-V and STS.
Junsoo Shin 1 2 , V. Nascimento 1 2 , S. Kalinin 2 3 , E. Plummer 1 2 3 , A. Baddorf 2 3
1 Physics, Universtiy of Tennessee, Knoxville, Tennessee, United States, 2 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 Center for Nanophase Materials Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show Abstract9:00 PM - DD8.44
Scaling of nanoporous materials: processing and mechanical properties
Andrea Hodge 1 , Juergen Biener 1 , Monika Biener 1 , Octavio Cervantes 1 , Alex Hamza 1
1 Nanoscale Synthesis and Characterization Laboratory, LLNL, Livermore, California, United States
Show AbstractComplex nanoscale structures such as nanoporous foams have shown potential for applications such as actuators and catalyst. Therefore, in order to utilize these materials for the next- generation nano-technologies there is a need to enhance our current understanding of scaling dimensions and their effect on the overall material behavior. Here we present a comprehensive study on scaling effects on both processing and mechanical behavior of nanoporous Au foams. The processing scale focuses on the dimensions of individual foam ligaments which range from 5 nm to 1 micron. Properties such as elastic modulus and yield strength are related as a function of the ligament length scale and compare to traditional macro-porous foams. Additionally, the foam surface to volume ratio at different length scales will be evaluated as a parameter for new catalytic materials. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under contract of No.W-7405-Eng-48.
9:00 PM - DD8.45
In situ Observation of Dewetting and Pattern Formation of Au and Ag Nanocrystalline Thin Films on Reeconstructed c- and m-planes of Sapphire.
Joysurya Basu 1 , Divakar Ramachandran 1 , Ravishankar Narayanan 2 , C. Barry Carter 1
1 Department of Chemical Engineering & Materials Science, University of Minnesota, Minneapolis, Minnesota, United States, 2 Materials Research Centre, Indian Institute of Science, Bangalore, Karnataka, India
Show Abstract9:00 PM - DD8.46
In situ TEM Study of Dewetting and Solid-state Reactions of Nanocrystalline Thin-film Oxides on Sapphire.
Divakar Ramachandran 1 , Joysurya Basu 1 , C. Barry Carter 1
1 Department of Chemical Engineering & Materials Science, University of Minnesota, Minneapolis, Minnesota, United States
Show Abstract9:00 PM - DD8.47
Characterization of Ge Nanocrystal/SiO2 multilayers Fabricated by Ion Beam Sputtering and Annealing.
Seung Hui Hong 1 , Do Kyu Lee 1 , Sung Won Hwang 1 , Phil Sung Jung 1 , Suk-Ho Choi 1 , Kyung Joong Kim 2
1 College of Electronics and Information, Kyung Hee University, Yongin, Kyungkido, Korea (the Republic of), 2 Division of Advanced Technology, Korea Research Institute of Standards and Science, Daejeon Korea (the Republic of)
Show Abstract9:00 PM - DD8.48
Effect of Electron Irradiation on Nanogroove-networked Single-crystalline and Dendritic Polycrystalline Platinum Nanosheets.
Masafumi Uota 1 , Takumi Yoshimura 2 1 , Takeshi Kuwahara 2 , Daisuke Fujikawa 2 1 , Hideya Kawasaki 3 1 , Go Sakai 2 1 , Tsuyoshi Kijima 2 1
1 , Japan Science and Technology Agency, Miyazaki Japan, 2 Applied Chemistry, Miyazaki University, Miyazaki Japan, 3 Applied Chemistry, Kansai University, Suita Japan
Show AbstractIncreasing attention has been focused on nanoscale platinum particles for their potential applications as a catalyst in various fields such petroleum chemical processes and polymer electrolyte fuel cells. The catalytic reactivity of Pt nanoparticles depends on their sizes and shapes as well as the arrangement of surface atoms. It is therefore important to control the structural and morphological properties of Pt nanomaterials. Our recent studies demonstrated the fabrication of Pt nanotubes by the hydrazine reduction of H2PtCl6 within lyotropic mixed surfactant liquid crystals (LCs) of polyoxyethylene (20) sorbitan monostearate (Tween 60) and nonaethyleneglycol dodecylether (C12EO9).1 We also synthesized nanogroove-network structured single-crystalline nanosheets through the reduction of Na2PtCl6 with NaBH4 using compositionally the same mixed surfactant LC templates.2 Furthermore, we also found that the nanogrooved Pt loaded on carbon exhibit fairly high electrocatalytic activity for oxygen reduction reaction. It would be of importance to characterize in more detail the structurally and functionally unique Pt nanomaterials An attempt was thus made to study the effect of electron irradiation on the structural properties of the nanogroove-network structured single-crystalline nanosheets and 2D-dendritic polycrystalline nanosheets. The nanogroove-network structured single-crystalline and the 2D-dendritic polycrystalline nanosheet samples were prepared using the Tween 60 based mixed- and single-surfactant LC templates as described elsewhere.1 Electron irradiation experiments were carried out by using transmission electron microscopy (TEM). The as-grown samples of single-crystalline nanogrooved and 2D-dendritic polycrystalline nanosheets were characterized by nearly the same average groove-width or dendritic spacing of 1.3-1.4 nm. On exposure to electron beam for 20 min at the acceleration voltage of 200 keV, the nanogrooved nanosheets were morphologically little affected, but the dendritic ones were transformed into less branched polycrystalline structures with spacings distributed around ~ 1.7nm. The shape transformation of the latter was found to occur by the combined mechanism of segmental migration and atomic diffusion. These observations indicate that the nanogrooved Pt nanosheets are highly stabilized by the grooved but crystallographically continuous Pt framework, leading to their extremely high thermo-resistance, in marked contrast to the polycrystalline dendritic structures constructed of crystallographically discontinuous linkages of nanoblocks.1. T. Kijima et al., Angew. Chem., 2004, 43, 228. 2. To be presented in this symposium.
9:00 PM - DD8.49
Effects of Chirality and Diameter on Electron Transport Properties in Individual Semiconducting Carbon Nanotubes.
M. Kauser 1 , P. Ruden 1
1 Dept. of ECE, University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractCarbon nanotubes (CNTs) are recognized as structures with the potential to be key building blocks in future nano-scale electronic and opto-electronic devices [1]. The structure of a CNT is fully determined by a pair of integers, (n,m). It is well established from theoretical calculations and scanning tunneling microscopy (STM) studies of CNTs that (n,n) CNTs with chiral angle θ = 30 degree and the group defined by (n-m) mod 3 = 0 are metallic, while rest are semiconducting. It is to be expected that chirality should affect the properties of semiconducting CNTs. Previous theoretical efforts have focused on the understanding of transport in achiral, semiconducting, zigzag (n,0) CNTs, based on analytical models [2] and Ensemble Monte Carlo (EMC) simulations [3,4,5]. Chiral (n,m) CNTs are rarely modeled, mainly due to their complicated electron and phonon dispersions associated with low symmetry. Recently we reported a technique to study chiral CNTs using EMC simulation and we found interesting effects of chirality and of group (defined by (n-m) mod 3 = ±1) on the transport properties of chiral CNTs with similar diameter [6]. In this paper, we explore the effects of chirality, group, and diameter on the electronic structure and transport properties of semiconducting CNTs. The electronic band structure is calculated based on a Tight Binding model along with zone folding. The high-field transport properties are simulated using EMC. The principal electron scattering mechanisms are due to coupling to longitudinal acoustic (LA), longitudinal optical (LO), and radial breathing mode (RBM) phonons. Both Normal and Umklapp scattering processes are considered. The low-field mobility is calculated using the momentum relaxation time approximation. The effects of chirality, group, and diameter on low-field mobility, saturation velocity, saturation electric field, and negative differential mobility are studied for all semiconducting CNTs usually investigated in experiments. Results show consistent trends of change in these properties with group, chirality, and diameter, which are attributed to changes in the electronic structure, especially the lowest subband effective masses. This study thus gives upper and lower bounds for key transport parameters for CNTs of known diameter but unknown chirality, which is the case typically encountered in experiments. References:[1] M. P. Anantram and F. Leonard, Rep. Prog. Phys. 69, 507 (2006).[2] V. Perebeinos, J. Tersoff, and P. Avouris, Phys. Rev. Lett. 94, 086802 (2005).[3] A. Verma, M. Z. Kauser, and P. P. Ruden, J. Appl. Phys. 97, 114319 (2005).[4] A. Verma, M. Z. Kauser, and P. P. Ruden, Appl. Phys. Lett. 87, 123101 (2005).[5] M. Z. Kauser, A. Verma and P. P. Ruden, Physica E 34, 666 (2006).[6] M. Z. Kauser and P. P. Ruden, Appl. Phys. Lett. 89, 162104 (2006).
9:00 PM - DD8.5
Lattice Engineering Synthesis of Heterostructured Metal Oxide Nanoparticle-Layered Titanate Nanohybrids.
Tae Woo Kim 1 , Seong-Ju Hwang 1
1 , Division of Nano Sciences, Ewha Womans University, Seoul Korea (the Republic of)
Show AbstractWe have synthesized porous nanohybrids of MOx-Ti1.83O4 (M = Zn, Cr, etc) heterostructure through a reassembling of exfoliated titanate nanosheets and transition metal oxide nanoclusters. According to XRD, FE-SEM, and HR-TEM analyses, individual titanate nanolayers are interstratified with metal oxide nanoparticles in layer-by-layer way, leading to the formation of porous intercalation structure. N2 adsorption-desorption isotherm and diffuse reflectance UV-vis analyses demonstrate that the present nanohybrids show expanded surface areas and modified band structures, which is due to the micro-/meso-porosity of these materials and the coupling between metal oxide components, respectively. These nanohybrids display an enhanced catalytic activity as well as a stabilization of the guest metal oxide. The present results highlight that the exfoliation-reassembling route can provide a very powerful way of developing novel heterostructured materials with promising functionalities.
9:00 PM - DD8.50
Phonon Spectra and Thermodynamic Properties Of Crystalline Nanowires.
Dusan Ilic 1 , Sinisa Vucenovic 2 , Stevo Jacimovski 3 , Vojkan Zoric 3 , Jovan Setrajcic 3
1 , Faculty of Technical Sciences, University of Novi Sad, Novi Sad, Vojvodina, , 2 , Faculty of Medicine, University of Banja Luka, Banja Luka, Republic of Srpska, Bosnia and Herzegovina, 3 Department of Physics, Faculty of Sciences, University of Novi Sad, Novi Sad, Vojvodina,
Show Abstract9:00 PM - DD8.6
The Sodium Salt Effects on the Layer-by-Layer Self-Assembled Carbon Nanotubes Multilayers
Kye Ung Lee 1 , Byung Tae Ahn 1 , Mike Petty 2 , Do Jin Kim 3
1 Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of), 2 School of Engineering and Centre for Molecular and Nanoscale Electronics, University of Durham, Durham United Kingdom, 3 Department of Materials Science and Engineering, Chungnam National University, Daejeon Korea (the Republic of)
Show AbstractLayer-by-layer(LbL) self-assembly is a template-assisted process in which charge reversal techniques using polyelectrolytes enable the deposition of films layer-by-layer. Layer-by-layer self-assembly is a powerful method to build ultrathin films and nanoparticles also could be incorporated in the thin film in the aids of polyelectrolyte. In this work, we will describe the building of thin film architectures incorporating carbon nanotubes(CNTs) with polyelectrolytes and salt effect on the building CNTs films. The CNTs are positively and negatively charged by coating strong polyelectrolytes, poly(styrene sulfonate) (PSS) and poly(diallyldimethylammonium) (PDDA), respectively. The side groups of polyelectrolytes could non-covalently interact with CNT wall by pi-pi interaction, etc. So CNTs with polyelectrolyes could be dispersed stably in water. With this treatment, stability of dispersion and solubility in water is improved. The presence of charged functional groups on the surface of the CNTs then allows consecutive thin film deposition to proceed via the electrostatic LbL method.The persistence length is a basic property quantifying the stiffness of a macromolecule of a polyelectrolytes. The persistence length of the polyelectrolyte chain should be one of the key parameters since it determines the chain’s ability to wrap around the nanotubes, resulting in the deposition. The persistence length of polyelectrolyte can be controlled by changing the ionic strength of CNT suspension, due to screening of electrostatic repulsion between the polyelectrolyte backbone charges. The ionic strength of CNT suspension was changed by changing sodium salt concentration. The analysis of UV-Vis spsectroscopy and ellipsometery showed that the higher ionic strength enhanced the deposition of CNTs. The adsorption state of CNTs with polyelectrolyte was studied using TEM and TGA. The self-assembly process was monitored using UV-Vis spectrophotometer, quartz crystal microbalance and ellipsometer. And the surface morphology of films was studied using SEM.
9:00 PM - DD8.7
Directed Assembly of Colloidal Particles on a Complex Physicochemical Nano Template.
Yong Hoon Kim 1 , Juhyun Park 2 , Pil J. Yoo 1 , Paula Hammond 1
1 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - DD8.8
Hierarchial Co-Doped ZnO Hexagonal Rings and Plates Composed of Self-Assembled Hexagonal ZnO Nanorods
Yi Jing Li 1 , Chiu-Yen Wang 1 , Ming-Yen Lu 1 , Kun-Mu Li 1 , Lih-Juann Chen 1
1 , National Tsing Hua University, Hsinchu Taiwan
Show AbstractCo-doped ZnO hexagonal rings composed of single-crystal ZnO hexagonal nanorods were grown via a combined hydrothermal and electrochemical process. The unique hierarchial ZnO hexagonal rings are based on the integration of single-crystalline ZnO nanorods of hexagonal shape. The growth of the external and inner frames of hexagonal rings is concentric. The perfect hexagonal units are aligned along <0001> directions while the frame of the hexagonal rings are bounded with six {1-210} planes. The composing ZnO units were found to be tightly connected and matched, which provides direct evidence for an oriented attachment growth mechanism. The cathodoluminescence peaks show a redshift about 237 meV and 423 meV of the band gap edge from that of the pure ZnO nanorods for 0.25% and 1% Co-doped ZnO nanostructures, respectively. Tuning of band gap by doping shall be beneficial for optical applications.
9:00 PM - DD8.9
Formation of Highly Ordered Arrays of Dimples on Tantalum at the Nanoscale.
Peter Kruse 1 , Sherdeep Singh 1 , Warren Barden 1 , Subir Ghosh 1 , Mark Greiner 1 , Hany El-Sayed 1
1 Chemistry, McMaster University, Hamilton, Ontario, Canada
Show AbstractGiven the current interest in nanostructured materials and nanoparticles, templates with monodispersed and highly ordered regular features are in high demand. As a result, researchers are studying systems such as porous metal oxides with the goal of developing new self-assembly techniques. Due to its outstanding properties, tantalum is an important material for mechanical, electronic and medical applications, but the ability to control its surface properties at the nanoscale has been largely limited to the growth of dense anodic oxides and, recently, porous oxides of poor order. Here we show that electropolishing of tantalum in concentrated acid mixtures can reproducibly lead to dimples tens of nanometers in diameter, regular in shape, monodispersed in size and arranged in highly ordered arrays which even transverse grain boundaries. After a single polishing step of less than ten minutes, dimples of 30 nm to 50 nm in diameter (a function of polishing voltage) and around 10 nm deep form a 2-dimensional structure consisting of tantalum metal covered in native oxide. Dimpled tantalum is ductile, high-melting, chemically inert and easily prepared. It can be safely used as a template or mould for nanostructure synthesis under extreme conditions, as demonstrated with a simple sputter coating and flame annealing procedure for gold nanoparticles. Due to their exceptional properties, we anticipate that these nanostructured tantalum surfaces will be suitable for a wide variety of applications in catalysis, combinatorial materials science, nanoparticle synthesis, biomedical devices, cast or die for nanopatterning of other materials etc.
Symposium Organizers
Moonsub Shim University of Illinois, Urbana-Champaign
Masaru Kuno University of Notre Dame
Xiao-Min Lin Argonne National Laboratory
Ruth Pachter Air Force Research Laboratory
Sanat Kumar Rensselaer Polytechnic Institute
DD9: Properties of Nanowires II
Session Chairs
Marija Drndic
Masaru Kuno
Wednesday AM, April 11, 2007
Room 2001 (Moscone West)
9:00 AM - DD9.1
Determination of the Young's modulus of individual electrospun nanofibers by microcantilever vibration method.
Philip Yuya 1 , Yongkui Wen 1 , Zheng Li 2 , Joseph Turner 1 , Yuris Dzenis 1
1 Engineering Mechanics, University of Nebraska-Lincoln, Lincoln, Nebraska, United States, 2 Mechanics & Engineering Science, Peking University, Beijing China
Show AbstractWe report a technique for measuring the Young's modulus of a single electrospun nanofiber using the vibrations of two microcantilevers coupled with the nanofiber. The modulus is calculated from the resonant frequency shift resulting from the nanofiber. Polyacrylonitrile nanofibers (200 nm diameter) were collected during electrospinning and wrapped on two similar microcantilevers causing a shift in first resonance from 10.0 kHz to 19.4 kHz. Finite element analysis was used to analyze the frequency shift using images from a scanning electron microscope giving a modulus of the as-spun PAN nanofiber of 26.8 GPa. Prospects for exploiting this technique for high-throughput mechanical characterization of electrospun nanofibers are discussed. [Results supported by NSF].
9:15 AM - DD9.2
Suspended Mechanical Structures Based on Elastic Silicon Nanowire Arrays.
Alvaro San Paulo 1 2 , Noel Arellano 2 , Jose Plaza 1 , Rongrui He 2 , Carlo Carraro 2 , Roya Maboudian 2 , Roger Howe 3 , Jeff Bokor 2 , Peidong Yang 2
1 , Centro Nacional de Microelectrónica, Bellaterra Spain, 2 , University of California at Berkeley, Berkeley, California, United States, 3 , University of Stanford, Stanford, California, United States
Show Abstract9:30 AM - DD9.3
STM of Polydiacetylene Nanowires: Electrode Interactions and Stability .
Rajiv Giridharagopal 1 , Kevin Kelly 1
1 Electrical and Computer Engineering, Rice University, Houston, Texas, United States
Show AbstractAn alternative to the traditional silicon electronics paradigm is molecular electronics, wherein carefully-tailored single molecules operate as switching elements. Interconnecting such elements to form a circuit poses a unique challenge at this scale, particularly from an electronic structure viewpoint. Polydiacetylene nanowires have been proposed as a possible molecular wire because they can be easily formed on a monolayer surface, have a simple, linear structure, and exhibit enhanced conductivity when doped. These nanowires have been analyzed at the nanoscale using scanning tunneling microscopy (STM) and spectroscopy. Analysis shows that the nanowires exhibit a strong electronic interaction with the substrate. Polydiacetylene nanowires on different electrode materials such as graphite and molybdenum disulfide exhibit substantially different electronic properties. The substrate-dependent charge transfer behavior observed implies that the electrode material is critical for using polydiacetylene interconnects in molecular electronic devices. Additionally, the desorption of these nanowires due to the STM tip was investigated. Desorption can occur in segments or along the entire nanowire. In both cases, the surrounding monolayer order is fully restored almost instantaneously via a "molecular cascade" effect. Desorption underlies a critical stability issue in polydiacetylene nanowires, and the properties outlined here are also important for applications of polydiacetylene in other fields, such as bio-sensors.
9:45 AM - DD9.4
Investigation of the Heterojunction Sharpness of Nanowhiskers by Analytical TEM Measurements.
Daniela Sudfeld 1 , Jochen Kaestner 1 , Guenter Dumpich 1 , Ingo Regolin 2 , Werner Prost 2 , Franz-J. Tegude 2
1 Experimental Physics - AG Farle, University of Duisburg-Essen, Duisburg Germany, 2 Solid State Electronics Dept., University of Duisburg-Essen, Duisburg Germany
Show Abstract10:00 AM - DD9.5
Size Effect of TiO2 Nanotubular Structures on Their Electrical Properties
Sihyeong Kim 1 , Bokyung Ahn 1 , Changdeuck Bae 1 , Hyunjung Shin 1
1 School of Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of)
Show AbstractElectrical properties of TiO2 nanotubes with different wall thicknesses and diameters were investigated. TiO2 nanotubes with the range from 1 to 100 nm of the wall thickness were deposited using atomic layer deposition (ALD) onto porous templates of polycarbonate (PC) and anodic aluminum oxide (AAO)[1]. To investigate electrical properties of TiO2 nanotubes formed in the porous templates, we constructed devices of Pt (top electrode of 200 nm in diameter)/TiO2 nanotubes in the porous templates/Pt (bottom electrode). I-V characteristics of PC templates without any coating of TiO2 as control experiments exhibit typical insulating behavior of polymeric materials. I-V/C-V characteristics of the devices with TiO2 nanotubes were measured. While the Schottky behaviors were common to both TiO2 nanotubes of 50 and 200 nm in diameter, it was found that the barrier height of Schottky diode decreased with decreasing the diameters of nanotubes. Effects due to the size in nanometer scale in diameter as well as the wall thickness on their electrical properties are discussed.AcknowledgementThis work was supported by the Center for Nanostructured Materials Technology of the Korean Ministry of Science and Technology (M105KO010026-06K1501-02610).[1] H. Shin, D.-K. Jeong, J. Lee, M. M. Sung, J. Kim, Adv. Mater. 2004, 16, 1197.
10:15 AM - DD9.6
Measuring Thermal Conductivity and Electrical Breakdown of GaN Nanowires
Elaine Lai 1 , Reese Jones 1 , George Wang 1 , Richard Anderson 1 , Bhavin Rokad 1 , Alec Talin 1
1 , Sandia National Labs, Livermore, California, United States
Show AbstractSandia National Labs, Livermore, CA 94550We report on the measurement of temperature, thermal conductivity, and eventual breakdown associated with Joule heating of individual GaN nanowires. Individual GaN nanowires with Ni/Au ohmic contacts are electrically heated under steady state conditions, while their temperature is determined by the wavelength of the band edge peak using micro-photoluminescence. We find that the extracted temperature is linearly related to the electrical power supplied to the nanowire. Breakdown occurs at a power range of 4 mW – 105 mW, depending on nanowire dimensions, and at a temperature range of 550K – 900K. Based on the temperature measurements, thermal conductivity was extracted using finite element modeling and compared to published bulk values for GaN. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lokheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000.
DD10: Assembly, Patterning and Collective Properties I
Session Chairs
Heinrich Jaeger
Masaru Kuno
Wednesday PM, April 11, 2007
Room 2001 (Moscone West)
10:45 AM - **DD10.1
Nanoparticle Electronics: Controlled Nanocrystal Assembly and High-resolution Device Fabrication on Silicon Nitride Membranes using Transmission Selectron Beams.
Marija Drndic 1 , Michael Fischbein 1 , Claudia Querner 1 , Zonghai Hu 1
1 Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show Abstract11:15 AM - DD10.2
ENFilADIng: An Innovative Route to Nanowire Growth and Interfacing.
Bret Flanders 1 , Birol Ozturk 1
1 Physics, Oklahoma State University, Stillwater, Oklahoma, United States
Show AbstractWe present a recently developed approach to nanowire fabrication and interfacing with external circuitry, termed Electrochemical NanoFilament Assembly and Directed Interfacing (ENFilADIng). Depositing salt solution over a pair of on-chip electrodes and applying an alternating voltage across the electrode-gap induces the growth of individual metal nanowires between the electrode tips (1). High resolution transmission electron diffraction measurements on wires grown from indium acetate and hydrogen tetrachloroaurate indicate that these nanowires are composed of single-crystalline indium and gold, respectively. Furthermore, precise control over the nanowire-diameter is attained through the frequency ω of the alternating voltage that induces the ENFilADIng process. For indium wires, increasing ω from 0.5 to 3.5 MHz increases the growth velocity of the wires from 11 to 78 μm/s and reduces their diameter from 770 to 114 nm. Gold wires exhibit diameter-tunability that extends well below 100 nm. Thus, it is possible to tune the wire diameter from the microscale down to the nanoscale. We will report on mechanistic understanding that we have developed regarding the diameter-tunability aspect of this technique. Additionally, by the feedback-controlled application of the alternating voltage, where the feedback signal is the cross-gap current, it becomes possible to terminate the applied voltage once the wire has bridged the electrode gap, but before the alternating voltage drives damaging currents through the nanowires. This approach yields electrode-nanowire-electrode assemblies with resistances of 223 ± 26 Ω, reproducibility that would not be possible were the voltage terminated manually. This combination of capabilities—the growth of single crystalline nanowires with precisely controlled diameters and reproducible interfacing with external circuitry—enables interrogation of the intrinsic transport properties of metallic nanowires. An area of particular interest is the contribution of surface scattering mechanisms to the total resistivity, an effect that is expected to increase with decreasing diameter. Progress on this investigation will be reported. (1)Talukdar, I.; Ozturk, B.; Mishima, T. D.; Flanders, B. N. Appl. Phys. Lett. 2006, 88, 221907.
11:30 AM - DD10.3
Electron Transport Properties of Solution-Processed Semiconducting Quantum-Wire Solids.
Debdeep Jena 1 , Amol Singh 1 , Vladimir Protasenko 2 , Huili Xing 1 , Masaru Kuno 2
1 Electrical Engineering, University of Notre Dame, Notre Dame, Indiana, United States, 2 Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States
Show AbstractCharge transport properties of solution-syntesized PbSe, CdTe, and CdSe quantum wire solids are studied experimentally. The quantum-wire solids, analogous to previously reported quantum-dot solids, are formed by dense networks of connected nanowires. The semiconducting nanowires are synthesized by the solution-liquid-solid (SLS) technique. The general growth procedure leverages advances in the synthesis of semiconducting nanocrystals - ~2 nm diameter low melting metallic nanoparticle catalysts are used to promote 1-D crystallization in the presence of coordinating surfactants such as trioctyl phosphine oxide (TOPO). The nanoparticles are introduced with a group-VI precursor (for example TOP-Se for CdSe and PbSe wires), along with ligand-coordinated metal ions (CdO with octanoic acid for CdSe). The resulting nanowires are 5-10 nm in diameter, and several microns long.Prior to transport studies, optical absorption/emission and photoconductive studies are performed on the nanowires, verifying their semiconducting nature, and revealing their optical bandgaps, which are blue-shifted corresponding to their bulk gaps due to quantum confinement effects. High-resolution TEM images reveal that the nanowires are highly crystalline, and the diameter variation in a typical yield is 25-30%, and the intrawire diameter variations are of the order of 5%.The diameters of the nanowires (<10nm) are smaller than twice the respective bulk exciton Bohr radii.Ohmic contacts are fabricated by controlled annealing of metal-quantum wire solid-metal structures. Temperature-dependent conductivity measurements are performed on the structures. As opposed to the closely related quantum-dot solids where charge transport occurs by Mott's variable range hopping above a critical temperature and through Coulomb-blockade effects for low temperatures, the transport in the quantum-wire solids is clearly observed to be by band-transport (σ ~ exp[-Eg/2kT]) with the activation energy corresponding precisely to half the bandgap of the semiconductor. This form of transport is observed for all three types of nanowires : PbSe, CdTe, and CdSe. The activation energies are in close agreement with the complementary optical absorption/emission and photoconductivity measurements (Eg = 0.27 eV, 1.6 eV, & 1.9 eV respectively for PbSe, CdTe, and CdSe nanowires). This provides the first demonstration that the solution-synthesized nanowires are nearly intrinsic, with very few density of dopant atoms (less than the respective thermally generated intrinsic carrier concentrations). Band-transport in such quantum-wire solids makes them attractive for a number of applications - they provide an alternative approach to various device architectures (FETs, photodetectors) . Being solution-processed, they are cheap and scalable, and well suited for large-area devices on virtually any substrates without limitations imposed by lattice mismatch in epitaxial growth.
11:45 AM - DD10.4
Precise Nanoparticle Placement via Electrostatic Funneling*
Vishva Ray 1 , Hong-Wen Huang 1 , Ramkumar Subramanian 1 , Liang-Chieh Ma 1 , Choong-Un Kim 1 , Seong Jin Koh 1
1 , The University of Texas at Arlington, Arlington, Texas, United States
Show AbstractOne of the key requirements toward the realization of nanoscale devices and sensors is the capability to place nanoscale building blocks on exact locations on the substrate. We have developed a wafer-scale scheme called “electrostatic funneling”, which guides charged colloidal nanoparticles onto targeted locations with nanoscale precision. We have demonstrated a placement precision of 6 nm using one-dimensional guiding structure patterned on 200 mm silicon wafer. In this approach, the electrostatic guiding structures were fabricated by selectively charging the substrate using self-assembled monolayers (SAMs) of organic molecules in aqueous solution. The merit of this technique is that nanoscale precision can be realized with guiding structures that can be fabricated using conventional CMOS technology with dimensional control of only ~100 nm. The effectiveness of this technique has also been demonstrated for various other geometries such as 0-dimensional arrays and three-dimensional step structures with gold nanoparticles of diameter 20, 50, 80, and 200nm. We have also calculated the underlying electrostatic interaction energies between nanoparticles and charged substrates using DLVO theory and found very good agreement with experimental observations. Our calculations show that a 20nm gold nanoparticle is subjected to a lateral force of 1E-7-4E-7 dynes when the nanoparticle-surface distance is less than 100 nm and this strong lateral force is responsible for the guided placement of nanoparticles. We envision that this electrostatic guiding scheme can also be applied to the precise placement of other nanoscale building blocks such as nanowires, carbon nanotubes, DNAs, and proteins. An application to fabrication of single electron devices utilizing guided nanoparticle placement will also be discussed. *Supported by ONR (N00014-05-1-0030), NSF CAREER (ECS-0449958), and THECB (003656-0014-2006).
12:00 PM - DD10.5
Strain-induced Self-assembled Oxide Nanostructures from Chemical Solutions.
Marta Gibert Gutierrez 1 , P. Abellan 1 , C. Moreno 1 , F. Sandiumenge 1 , R. Huehne 2 , T. Puig 1 , X. Obradors 1
1 , Institut de Ciència de Materials de Barcelona ICMAB-CSIC, Bellaterra, Catalonia, Barcelona, Spain, 2 Institute for Metallic Materials, IFW-Dresden, Dresden Germany
Show Abstract12:15 PM - DD10.6
Direct Assembly of Quantum Confined Nano-particles.
Ingo Pluemel 1 2 , Klemens Hitzbleck 2 , Ivo Rangelow 4 , Jan Meijer 3 , Hartmut Wiggers 2
1 Experimental Physics, University of Duisburg-Essen, Duisburg Germany, 2 Institute of Combustion and Gasdynamics, University of Duisburg-Essen, Duisburg Germany, 4 Institute for Micro- and Nanoelectronics, Technische Universität Ilmenau, Ilmenau Germany, 3 RUBION, Ruhr-Universität Bochum, Bochum Germany
Show Abstract12:30 PM - DD10.7
Lipid Nanotubes as Scaffolds for Selective Deposition of CdS Nanodots
Yong Zhou 1 , Shimizu Toshimi 1 2
1 SORST, Tsukuba Central 5, Japan Science and Technology Agency (JST), Tsukuba, Ibaraki, Japan, 2 Nanoarhcitectonics Research Center (NARC), Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
Show AbstractIn recent years, there has been much interest in using lipid nanotubes (LNTs) to modulate the growth of a large variety of inorganic nanomaterials including metal, semiconductor, and magnetic particles [1]. In this presentation, we report LNTs as scaffolds to selective deposition of CdS nanodots (NDs) on the surfaces, in the hollow cylinder, and in the bilayer membrane walls of the nanotubes with different techniques. Firstly, the dense helical arrays of CdS NDs, which are aligned one-by-one and side-by-side, form on the surfaces of the self-assembled LNT template from the binary components, glycolipid, N-(11-cis-octadecenoyl)-β-D-glucopyranosylamine (1) and aminophenyl-β-D-glucopyranoside (2) as an additive [2]. The formation mechanism greatly differs from precedent examples that utilize residual helical marks on the surfaces of LNTs and nanoribbons or organic templates with a helical morphology. Here, we functionalized the glycolipid nanotube of 1 by incorporation of 2 through the self-assembly. This functionalization process enabled us to create active binding sites, which trace the chiral molecular packing of the nanotube. Consequently, the helical nucleation and growth of the CdS NDs took place on the template surfaces. Secondly, one-dimensional (1-D) confinement of CdS NDs was made in the hollow cylinder of the LNT from 1 as a scaffold. We have used two paths to realize the 1-D arrangement of the CdS NDs in the LNT. One is that the LNT was dispersed into aqueous solutions of water-soluble CdS NDs, and then the fluidic NDs diffuse into the hollow cylinder of the LNT via capillary force. The other is that the solution of a CdS precursor diffuses into the LNT, followed by in situ formation of CdS NDs in the nanochannels of the LNT. Furthermore, calcination of the CdS-NDs-encapsulated LNT enabled us to obtain single-crystalline CdS nanowires. Thirdly, we first report in situ direct growth of the CdS NDs in the bilayer membranes of a self-assembled peptide LNT.3 We used the synthetic lipid, the sodium salt of 2-(2-(2-tetradecanamidoacetamido) acetamido) acetic acid (3) that can self-assemble in aqueous solutions into a hollow cylindrical structure in the presence of Cd2+. Upon exposure to H2S vapor, the Cd2+ in the Cd2+-complexed LNT were released as a result of competitive binding of the proton to the COO- group, resulting in the formation of H+-induced LNT. The released Cd2+ subsequently reacted with S2- to initiate CdS nuclei, and finally grew into the CdS NDs in all over the lipid bilayer membranes of [3]. The present three processes typically represent effective steps to artificially control the crystal orientation and morphology on bio-inspired substrates.References[1] Shimizu, T.; Masuda, M.; Minamikawa, H. Chem. Rev. 2005, 105, 1401.[2] Zhou, Y.; Ji, Q.; Masuda, M.; Kamiya, S.; Shimizu, T. Chem. Mater. 2006, 18, 403[3] Zhou, Y.; Kogiso, M.; He, C.; Shimizu, Y.; Koshizaki, N.; Shimizu, T. Adv. Mater. (in revision).
12:45 PM - DD10.8
High Resolution DNA Arrays by Supramolecular Nanostamping
Ozge Akbulut 1 , Jin-Mi Jung 2 , Ryan Bennett 3 , Robert Cohen 3 , Anne Mayes 1 , Francesco Stellacci 1
1 DMSE, MIT, Cambridge, Massachusetts, United States, 2 Materials Science and Engineering, KAIST, Daejeon Korea (the Republic of), 3 Department of Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractThe emerging need for miniaturizing devices makes biomolecules great candidates not only for serving as a template but also as a structural component. In order to exploit DNA as well as other biomolecules, we need to find ways to produce high resolution bio-arrays. Although many methods to serially fabricate such arrays have been developed, no clear strategy on how to scale the production efficiency up has been presented.In the quest for fast soft material stamping processes able to produce chemically complex bio-devices, a recent method, Supramolecular Nanostamping (SuNS) has been demonstrated. It replicates DNA-made nanoscale features effectively from one surface to another keeping the DNA information. [1, 2] A layer of single stranded DNA molecules is immobilized on a surface. When this layer is treated with its complimentary DNA molecules, which contain specific end groups, due to the supramolecular forces double helices are formed on the surface. The specific end groups of complimentary DNA molecules target to bond covalently to a secondary surface. When the master and the secondary surface come into contact, complimentary DNA molecules attach to the secondary surface through their end groups and stays there after dehybridization upon heating. Namely, SuNS dublicates the DNA arrays via harnessing the reversible hybridization reaction of complimentary DNA molecules.Here we employ a convenient bottom-up approach to obtain ordered arrays of DNA with 10-20 nm features spaced by 70 nm. The master is formed by self-assembly of DNA on gold nanoparticles obtained from the gold-modified polystyrene-b-poly(2-vinylpridine) (PS-b-P2VP) micellar block copolymer. [3] References1)Yu, AA., Savas, TA., Taylor GS., Guiseppe-Elie A., Smith, HI., Nano Letters, 2005, 5, 1061.2)Lin, H., Sun, L., Crooks, RM., J. Am. Chem. Soc., 2005, 127, 11210.3)Lu, JQ & Yu, S., Langmuir, 2006, 22, 3951.
DD11: Assembly, Patterning and Collective Properties II
Session Chairs
Bret Flanders
Masaru Kuno
Wednesday PM, April 11, 2007
Room 2001 (Moscone West)
2:30 PM - DD11.1
Drying Mediated Self-Assembly of Nanoparticles from a Sphere-on-Flat Geometry.
Zhiqun Lin 1 , Jun Xu 1
1 Materials Science and Engineering, Iowa State University, Ames, Iowa, United States
Show AbstractSelf-assembly of nanoparticles via irreversible solvent evaporation has been recognized as an extremely simple route to intriguing structures. However, these dissipative structures are often randomly organized without controlled regularity. Herein, we show a simple, one-step technique to produce concentric rings and spokes consisting of quantum dots and gold nanoparticles with high fidelity and regularity by allowing a drop of nanoparticle solution to evaporate in a sphere-on-flat geometry. The rings and spokes are nanometers high, submicrons to a few microns wide, and millimeters long. This technique, which dispenses with the need for lithography and external fields, is fast, cost-effective and robust. As such, it represents a powerful strategy for creating highly structured, multifunctional materials and devices.
2:45 PM - DD11.2
One-Nanometer-Scale Size-Controlled Synthesis and 2D Self-Assembly of Monodisperse Gold Nanoparticles.
Sang-Kee Eah 1 , James Basham 1
1 Department of Physics, Applied Phyics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractWe deveolped a simple, fast, and highly reproducible chemical synthesis method for colloidal gold nanoparticles, which are monodisperse in size with diameters of 3, 4, 5, 6, 7, 8, and 9 nm. Gold nanoparticles smaller than 3 nm are made in water by reducing gold ions with sodium borohydride molecules, and then they are transferred to toluene after being coated with ligand molecules of 1-dodecanethiol. One-nanometer-scale size control is demonstrated simply by adjusting the heating time of the gold nanopartiles solution at the boiling temperature of 1-dodecanethiol. These monodisperse gold nanoparticles self-assemble into three-dimensional and two-dimensional (2D) superlattices of hexagonal close-packing order. We will present a 2D monolayer of gold nanoparticles as large as completly covering the whole surface of a 3 inch silicon wafer. The monolayer of gold nanoparticles is composed of nearly perfect 2D superlattice domains, whose size can be larger than 20 um. To our best knowledge this monolayer and its 2D superlattice domains of nanoparticles are the largest ones ever reported. The 2D self-assembly is done simply by evaporating toluene droplets of gold nanoparticles together with water droplets without need of any special equipment. Conditions for reproducibly forming such large monolayers and 2D superlattice domains of nanoparticles will be discussed in addition to the mechanism of this 2D self-assembly method for nanoparticles. Currently we are working on generalization of this synthesis and 2D self-assembly method to other kinds of nanoparticles and 2D self-assembly of binary nanoparticles superlattices varying the size combination and the mixing ratio.
3:00 PM - **DD11.3
Dried to Order: Metal Nanocrystal Superlattices Self-Assembled from Solution
Heinrich Jaeger 1
1 James Franck Institute, University of Chicago, Chicago, Illinois, United States
Show AbstractThis talk will give an overview of the properties of nanocrystal superlattice structures that can be self-assembled by drop drying. The first part discusses the main assembly mechanisms as well as extensions and techniques to produce (quasi-) one-dimensional, two-dimensional and three-dimensional structures. Close-packed monolayers can be produced that extend over millimeters and exhibit near-perfect long-range order over tens of square microns. The superlattices self-assemble directly onto solid substrates, can drape themselves over prefabricated electrode structures, and require no transfer or further processing. I will focus on results obtained with 6nm diameter, dodecanethiol-capped gold nanocrystals, but the self-assembly process has general applicability. By controlling the process conditions, ordered monolayer arrays with inter-particle spacing less than 1nm have been produced. The second part of the talk discusses the remarkably robust electronic transport properties of the self-assembled structures. Strong Coulomb blockade effects in the presence of quenched charge disorder give rise to highly nonlinear current-voltage characteristics. Inside the Coulomb blockade regime, the residual zero-bias conductance results from multiple co-tunneling events. The third part will look at the mechanical properties of metal nanoparticle monolayers freely suspended over micron-sized holes.
3:30 PM - DD11.4
Fabrication, Optimization and Modeling of Highly Ordered Assemblies of Monodisperse Metallic Nanostructure Arrays.
Aniketa Shinde 2 1 , Chulsu Jo 2 , Jiun Pyng You 1 , Ju Hyeon Choi 1 , Ruqian Wu 1 , Regina Ragan 2
2 Physics & Astronomy, UC Irvine, Irvine, California, United States, 1 CheMS, UC Irvine, Irvine, California, United States
Show Abstract Metal nanostructures have demonstrated extraordinary properties: the capacity for single molecule detection in plasmon resonance biosensors, chemical sensitivity and higher performance in catalytic processes than their bulk counterparts, and the transport of electromagnetic energy along particle chains in optical circuits. One of the most significant challenges to technical developments that capitalize on unique properties of metal nanostructures is the fabrication of nanostructure arrays with monodisperse size, shape and high density using low cost and high throughput technique. We will present a unique Si-compatible fabrication process for dense ordered arrays (~1011 cm-2) of metal nanostructures with monodisperse size and shape, over large area ( >1mm2), and having feature size and inter-particle spacing unattainable with state of the art electron beam lithography. Noble metal deposited via physical vapor deposition on a nanowire template combined with reactive ion etching produced noble metal core-shell nanowire and nanoparticle arrays with mean feature size of approximately 8 nm. Hexagonal rare earth disilicide nanowires, such as DySi2 and ErSi2, are used as self-assembled nanowire templates on Si(001). Dense arrays of parallel DySi2 and ErSi2 nanowires having lengths greater than 1 micron and widths less than 5 nm have been fabricated and characterized on vicinal Si(001) previously. Scanning tunneling microscopy has shown that platinum (gold) forms clusters on the ErSi2 (DySi2) nanowire surfaces, and scanning electron microscopy backscattered images have shown that noble metal preferentially aggregates on the nanowire surfaces as opposed to the Si substrate. Noble metal coverage is used to select nanoparticle versus nanowire arrays after RIE. In the case of nanoparticles, a narrow size distribution of less than than 1 nm and inter-particle spacing of approximately 10 nm is obtained by our process. Few studies have been done on the theory behind the formation of the nanowire templates as well as the phenomena of preferential aggregation of noble metal on nanowire surfaces. Thus, theoretical modeling is combined with scanning probe microscopy in order to gain a deeper understanding of thermodynamics and kinetics driving nanostructure formation. We will also present ongoing work that uses VASP, an ab initio software package, to simulate RESi2 crystal structures as well as metal atoms on nanowire surfaces. Our preliminary calculations for bulk YSi2 have been found to be in close agreement with experiment and other theoretical studies. Our goal is to understand assembly mechanisms in order to optimize structure and make our process applicable to other material systems.
3:45 PM - DD11.5
Templated Growth of Complex Hybrid Nanostructures
Erik Spoerke 1 , Thomas Sounart 1 , Julia Hsu 1 , James Voigt 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractWe have investigated the synthesis and characterization of multicomponent nanocrystalline hybrid materials and films. Nanoscale materials present unique optical, electrical, and structural properties with significant technological implications. Such unique properties are strongly dependent on the chemical and structural composition of these materials. We have explored synthetic strategies to create hybrid materials whose chemical and structural composition may be controlled on multiple organizational levels. Utilizing a multistage solution-phase growth process, we can create hierarchical zinc oxide (ZnO) nanostructures. Using these nanoconstructs as templates, we create unique hybrid structures whose final form and properties may be controlled through the introduction of bio-inspired crystal growth modifiers such as amino acids and engineered peptides. Combining this multistage, solution-phase growth approach with these organic tools facilitates controlled, directed nanostructure formation, interfacing functional materials such as cadmium sulfide or silica nanoparticles with zinc oxide nanorods. Extending the formation of these structures to form micropatterned films, we further demonstrate the hierarchical nature of the materials created using this multi-stage synthesis and assembly strategy. These methods for the growth of complex nanostructures represent powerful potential tools in the development of new materials systems. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000.
4:00 PM - DD11.6
Quantum Dot Microrods.
Arya Ghadimi 1 , Ludovico Cademartiri 1 , Reihaneh Malakooti 1 , Geoffrey Ozin 1
1 Chemistry, University of Toronto, Toronto, Ontario, Canada
Show AbstractThe recent developments in nanocrystal self-assembly have garnered a great deal of attention in part because such assemblies exhibit novel and useful combinations of properties. For instance, these assemblies may possess structurally significant size and mechanical stability in conjunction with photoluminescence characteristic of their quantum-confined constituents. However, synthesis of self-supporting nanocrystal assemblies is quite challenging: typically nanocrystals’ original properties cannot be retained in the final assembly due to the harsh treatments necessary to preserve mechanical stability after the removal of the supporting template. Here we demonstrate a general approach for the fabrication of flexible, self-supporting microrods composed of densely packed nanocrystals which retain their properties throughout the assembly process. Furthermore, the nanocrystal building blocks show a remarkable tendency to self-assemble into large, highly-ordered domains within the microrods. Nano-channel anodized alumina was used as a template to synthesize microrods from PbS quantum dots and Bi2S3 nanorods. The nanocrystal assemblies were subsequently consolidated by the recently discovered process of nanocrystal plasma polymerization. The selective removal of the alumina template yielded flexible, self-supporting microrods composed of individual nanoparticles. In the case of PbS, the microrods exhibited photoluminescence comparable to that of pristine colloidal nanoparticles. PbS self-supporting nanotubes have also been demonstrated. The method and the results discussed here are important to the study of nanocrystal self-assembly and plasma polymerization in confined spaces, and the development of hierarchical nanocrystal-based architectures in which the geometry and the length scale are coupled to the overall functionality. The generality and versatility of this method add to its potential for creating purpose made micron-scale structures exhibiting nano-scale properties.
4:30 PM - DD11.7
Hierarchically Organized Nanoparticle Mesostructure ArraysFormed through Hydrothermal Self-Assembly.
Hongyou Fan 1 2 , Adam Wright 2 , John Gabaldon 2 , Bruce Burckel 1 , Jeffrey Brinker 1 , Ryan Tian 1 , Jun Liu 1
1 , Sandia National Lab, Albuquerque, New Mexico, United States, 2 Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico, United States
Show Abstract4:45 PM - DD11.8
General Approach to Large Area Films of Aligned Nanowires and Carbon Nanotubes via Bubble Expansion
Guihua Yu 1 , Anyuan Cao 2 , Charles Lieber 1 3
1 Chemistry, Harvard University, Cambridge, Massachusetts, United States, 2 Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States, 3 Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show AbstractCentral to many electronic device-based applications of nanowires (NWs) and carbon nanotubes (NTs) is the development of methods that enable organization over large areas with controlled orientation and density. Herein, we report a general and flexible method involving bubble expansion of homogeneous suspensions of NWs and carbon NTs to produce large area films. Studies demonstrate that the NWs and carbon NTs are well aligned within the films, and that density can be readily controlled by starting suspension concentration. The nanomaterial-embedded bubble films can be conformably transferred to a variety of substrates, including crystalline wafers and flexible plastics, and also suspended across open frames. In addition, measurements show that percolation threshold is readily exceeded to yield electrically conducting carbon NT films and that large scale NW field-effect transistor (FET) arrays can be easily fabricated on over large plastic substrates. The simplicity, scalability and generality of this approach offers substantial promise for exploring new structures containing large arrays of NWs and NTs, and for enabling applications of these nanomaterials.
5:00 PM - DD11.9
Nano-Polymers.
Gretchen DeVries 1 , Frajovon Talley 2 , Francesco Stellacci 1
1 DMSE, MIT, Cambridge, Massachusetts, United States, 2 , Howard University, Washington D.C., District of Columbia, United States
Show AbstractNanoparticles will spontaneously aggregate into two- and three-dimensional structures, but to date they lack the ability to bond together in a directional manner to generate more complex structures. Anisotropic assemblies of nanoparticles possess unique properties that are not generally accessible by isotropic arrays of particles. The scope of potential scientific and technological applications for nanoparticles would be vastly enlarged by the introduction of a method to break the interaction symmetry of nanoparticles, thus inducing valency and directional interparticle interactions. Ligand-coated metal nanoparticles are particularly promising for this aim, because the ligands can be used as handles for directed assembly while simultaneously offering an easy way to manipulate the physical properties of the nanoparticles. We have demonstrated the ability to direct the assembly of metal nanoparticles into one-dimensional chains by taking advantage of molecularly defined defect points in the ligand shell located at diametrically opposed positions on the nanoparticle. Placing molecules with a reactive end group, such as a carboxylic acid, at these polar defect points generates “divalent” nanoparticles that can be reacted with diamine terminated molecules to generate linear chains of nanoparticles covalently held together through amide bonds.Here we discuss the assembly of these nanoparticle chains into structurally robust self-standing nanoparticle films that possess unique mechanical and electrical properties. Additionally, we present a detailed kinetic and thermodynamic characterization of the molecularly defined defect points that enable the generation of these chains and films. We demonstrate that the polar defect points are thermodynamically unique sites within the ligand shell and possess a significantly higher reactivity than other sites on the nanoparticle. A thorough understanding of the thermodynamic equilibrium governing place exchange at these defect points is essential for the controlled assembly of one-dimensional nanoparticle chains.
5:15 PM - DD11.10
Silica Nanoparticles Three Dimensional Assembly: an Integrative Chemistry Approach toward Designing Opal-Like Silica Foams
Renal Backov 1 , Florent Carn 1
1 , CNRS-Universite Bordeaux-I, Pessac France
Show AbstractDesigning new porous materials in a monolithic form with framework involving hierarchical pore system while tailoring the macroscopic void spaces is an emerging area of technological interest toward heterogeneous catalysis, separations, artificial bone structure, thermal and/or acoustic insulation, ion-exchange operation. In addition to the micro- and/or mesoscale organization, shaping porous solids in the form of monolith with tailored macropore morphologies associated with a tunable surface roughness are also important factor that influence the suitability for potential applications. In this context of reaching specific functions, the integrative chemistry concept has been proposed recently and his offering a widesuch materials with higher order architecture can be obtained by using soft matter macroscopic template such as biliquid[1] or air-liquid foam[2]. We describe here a low cost and effective way of preparing hierarchically organized porous silica monolith arising from an air-liquid foam structure transcription by colloidal cristallisation. The opal-like skeleton provide a tunable surface roughness by using different size of silica colloidal particles while the macropore morphology (i.e. pore wall thickness, pore wall length) can be tune by a continuous control over the foam’s liquid fraction and the gas bubble size during the mineralization process. Moreover open or closed pore structure can be reached upon the foam’s liquid fraction and the colloidal particle size involved during the foaming process. This work[3] extends the recently reported study[4] on the preparation of SiO2 foam using molecular precursor. Herein, mimicking natural microstructure of super-hydrophobic leaves, the use of colloidal particle allows shaping the surface roughness leading thus to amplified the surface hydrophobic character. Furthermore, predominantly closed cell materials are needed for thermal insulation and open interconnected materials are required for uses involving fluid or gas transport such as filters and catalysts.1- F. Carn, A. Colin, M.-F. Achard, H. Deleuze, E. Sellier, M. Birot, R. Backov, J. Mater. Chem., 2004, 14, 1370.2- F. Carn, A. Colin, M.-F. Achard, H. Deleuze, C. Sanchez, R. Backov, Adv. Mater., 2005, 17, 62.3- F. Carn, P. Massé, S. Ravaine, H. Deleuze and R. Backov, Langmuir (submitted).4- F. Carn, A. Colin, M.-F. Achard, H. Deleuze, R. Backov, Adv. Mater., 2004, 6, 140.
5:30 PM - DD11.11
Tailoring ``Internal" Microstructure of Functional Inorganic Nanopatterns.
Suresh Donthu 1 2 , Zixiao Pan 1 2 , Vinayak Dravid 1 2
1 Materials Science and Engineering, Northwestern University, evanston, Illinois, United States, 2 , International Institute for Nanotechnology, Evanston, Illinois, United States
Show Abstract5:45 PM - DD11.12
MOCVD Behaviors of Two-sized InGaAs Ordered Nano-bar Arrays Grown Selectively on a GaAs Substrate.
Benzhong Wang 1 , Soo-Jin Chua 1
1 Opto-and Electronic Systems Cluster, Institute of Materials Research and Engineering, Singapore Singapore
Show AbstractDD12: Poster Session: Synthesis and Characterization I
Session Chairs
Sanat Kumar
Masaru Kuno
Xiao-Min Lin
Ruth Pachter
Moonsub Shim
Thursday AM, April 12, 2007
Salon Level (Marriott)
9:00 PM - DD12.1
Imaging and Nanopatterning in Liquids: in situ Studies of Electron Beam Induced Catalytic Deposition of Ag on TiO2 Nanowires from Aqueous Solutions
Natalia Kolmakova 1 , John Bozzola 2 , Andrei Kolmakov 1
1 Physics, SIUC, Carbondale, Illinois, United States, 2 IMAGE Center, SIUC, Carbondale, Illinois, United States
Show AbstractThe combination of nm-scale resolution capacity of Scanning Electron Microscopy and innovative QuantomiX WETSEM technique is demonstrated to be a practical solution for immediate in situ real time high-resolution imaging of chemical processes taking place on the surfaces of nanostructures in liquids or high pressure conditions. In our report , electron beam induced catalytic reaction of metal deposition out of aqueous solution was studied on the surface of fully hydrated TiO2 nanowires. This approach has excellent perspectives for not only in situ imaging and in vivo prompt analysis of the nano-and meso- objects in chemistry, physics and bioscience but also for nanofabrication and rational functionalization of nanostructures in liquids and different gas environment.
9:00 PM - DD12.10
Characterization and Preparation of the ITO Target which Make use of Various Sizes of Tin Oxide.
Ji-Hoon Rhee 1 , Myung Geun Song 1 , Pil-Sang Yun 1 , Kyung Koo Jeong 1 , Yun Ju Cho 1 , Ju Ok Park 1
1 Nano Materials Lab, Samsung Corning, Suwon Korea (the Republic of)
Show Abstract9:00 PM - DD12.11
Photoreflectance Spectroscopy in InAs/GaAs Heterostructures
Jun Oh Kim 1 2 , Sang Jun Lee 2 , Sam Kyu Noh 2 , Kyu-Seok Lee 3 , Jung Woo Choe 1
1 Physics and Applied Physics, Kyung Hee University, Yongin Korea (the Republic of), 2 Quantum Dot Technology Laboratory, Korea Research Institute of Standards and Science, Daejeon Korea (the Republic of), 3 , Electronics and Telecommunication Research Institute, Daejeon Korea (the Republic of)
Show AbstractPhotoreflectance (PR) spectroscopy has been widely used for the characterization of semiconductors. Due to its derivative nature, the PR technique is a powerful tool to investigate the band structure of semiconductor hetrostructures. Here, we report on room-temperature PR spectra of InAs quantum dots (QD)/GaAs and InAs WL/GaAs hetrostructure grown on semi-insulating (SI)-GaAs substrates by using molecular beam epitaxy (MBE). Showing a major GaAs bandgap feature, the both structures reveal distinctive PR signatures associated with the confined subbands of WL with and without QDs at the energy region below the GaAs bandgap. For InAs quantum dots (QD)/GaAs samples, an oscillatory feature is also observed in the energy range below the bandgap of GaAs, which is due to the interference effect of reflected light beams, one reflected from the interface of GaAs/SI-GaAs substrate and the other reflected from the InAs-QD/GaAs hetrointerface. A non-zero offset value of the PR interference indicates that the refractive index of the GaAs epilayer containing InAs QDs is modulated by a modulation laser light. On the other hand, InAs WL/GaAs heterostructures grown on SI-GaAs substrates do not show such oscillations, whereas Franz-Keldysh oscillations (FKO) are observed in the energy region above the GaAs bandgap, indicating that the GaAs cap grown on the InAs WL is subjected to a built-in electric field.
9:00 PM - DD12.12
Fabrication and Optical Properties of Nanocrystalline ZnO Composite Films on Si Substrates.
Young-Hwan Kim 1 , Woon-Jo Cho 2 , Seong-Il Kim 1 , Yong Tae Kim 1
1 Semiconductor Materials and Devices Laboratory, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 2 Nano Device Research Center, Korea Institute of Science and Technology, Seoul Korea (the Republic of)
Show AbstractOptoelectronic materials compatible with silicon substrates are important from the viewpoint of practical applications for silicon photonics. In this work, we have fabricated nanocrystalline ZnO composite films on Si(100) substrates and these films showed a strong cathodoluminescent property. The nanocrystalline ZnO composite film was fabricated by rf sputtering of ZnO and Si targets simultaneously and rapid thermal annealing process. The composition of the film and post-annealing temperature were found to be crucial to fabricate the nanocrystalline ZnO composite films. The film composition was controlled by changing the area ratio of Si and ZnO targets and the as-deposited films were post-annealed at the temperatures of 400~1000 oC for 3 minutes in a nitrogen atmosphere. The high-resolution TEM analysis showed that the nanocrystalline ZnO composite film could be obtained by annealing the film with Zn/Si ratio=~1.6 at 700 oC. This film contains nanocrystals with a size of ~5 nm, which could be identified as ZnO from electron diffraction pattern. The nanocrystalline ZnO composite film exhibited a strong and broad cathodoluminescence (CL) peak around 395 nm with a FWHM of ~180 nm. However, the film with Zn/Si ratio greater than the optimized value was found to have a ZnO film structure with many structural defects and exhibited the similar optical properties to those of ZnO film. The formation of ZnO nanocrystals in our composite film was confirmed by using energy dispersive x-ray spectroscopy and electron energy loss spectroscopy. The origin of the strong and broad CL peak around ~395 nm from the nanocrystalline ZnO composite film, leading to a possible application to a UV lighting source, will be discussed analytically.This work is supported by the Korea Institute of Science and technology under Contract No. 2E19520.
9:00 PM - DD12.13
Electrical Characteristics of HgTe Nanocrystal-based Thin-film Transistors Fabricated on Flexible Plastic Substrates.
Jaewon Jang 1 , Dong-Won Kim 1 , Kyoungah Cho 1 , Sangsig Kim 1
1 , Korea University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - DD12.14
Boundaries Between MgO Smoke Particles.
Julia Nowak 1 , C. Barry Carter 1
1 Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractHighly oriented nanoparticles are particularly suitable for study in the transmission electron microscope (TEM) because the surface facets can provide a certain a priori knowledge about the particles. Magnesium oxide (MgO) nanocubes are also suited for such a study because of the ease with which they can be produced and there crystal structure is well understood. When Mg metal is burned in air the reaction 2Mg + O2 → 2MgO produces a ‘smoke’ which consists of small particles of MgO. The particles produced are typically perfect cubes with edge lengths on the order of a few tens of nanometers and exhibit almost exclusively (100) faces. The smoke can be collected directly on an amorphous support film for investigation in the TEM.MgO is an ionically bonded crystal with the rocksalt structure. It is has previously been found that special boundaries form when two cube particles come into contact. If the mis-orientation between two crystals takes a particular value, a special low-energy configuration can occur; special high-angle twist boundaries in MgO, first investigated in the early 1970s, are predicted by the coincidence site lattice (CSL) model. The CSL model, used to describe the unique angles of misorientation between the two crystals, predicts four low-energy twist boundaries in MgO: Σ5, Σ13, Σ17, and Σ25 though these are not all equally likely in practice. These pairs of bonded MgO cubes are particularly instructive for investigating CSL boundaries because the angle of misorientation between two particles can be measured directly in the TEM if the particles are oriented properly with respect to the electron beam. In addition to twist boundaries, MgO smoke particles also make contact along the cube edges and at the cube corners. The ionic nature of the MgO produces a local charge at the corners and edges of MgO smoke cubes where the coordination is different than that of the bulk. This study uses the TEM to examine the various types of boundaries between nanocubes of MgO and investigates the role of coordination in these unique contacts.
9:00 PM - DD12.15
Structural and Magnetic Characteristics of Self-Assembled Nickel Nanoparticles in CeO2 Thin Films
Adero Paige 1 , Jeremiah Abiade 1 , Dhananjay Kumar 1 , A. Majumdar 2
1 , North Carolina A&T State University, Greensboro, North Carolina, United States, 2 , S.N. Bose National Centre for Basic Sciences, Kolkata India
Show Abstract9:00 PM - DD12.16
In situ Synchrotron Absorption Experiments and Modelling of the Growth Rates of Electrochemically Deposited ZnO Nanostructures.
Bridget Ingham 1 2 , Benoit Illy 3 , Jade Mackay 4 , Stephen White 1 , Shaun Hendy 1 5 , Mary Ryan 3
1 , Industrial Research Limited, Lower Hutt New Zealand, 2 SSRL, Stanford Linear Accelerator Center, Palo Alto, California, United States, 3 Department of Materials, Imperial College, London United Kingdom, 4 School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington New Zealand, 5 , MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington New Zealand
Show Abstract9:00 PM - DD12.17
Fabrication and Applications of Se-coated CdSe Nanowires Prepared by Chemical Treatments and Molecular Surface Engineering.
Ngai Sze Lam 1 , Ka Wai Wong 1 , Quan Li 1
1 Physics, The Chinese University of Hong Kong, Hong Kong China
Show Abstract9:00 PM - DD12.18
CNT Growth by Direct-Writing
Wu Yu-Tsung 1 , Tri-Rung Yew 1
1 , National Tsing Hua University, Hsinchu Taiwan
Show AbstractThis paper presents the formation of carbon nanotubes (CNTs) using KrF excimer pulse-laser direct-writing. This laser energy approach irradiates deposited amorphous carbon with Ni catalyst underneath for carbon nanotube (CNT) transformation from carbon species catalyzed by Ni. The effect of process parameters including pulse energy, frequency, and pulse duration on CNT formation will be investigated. The CNT formation mechanism will be also discussed. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectrum will be utilized to characterize the physical properties of CNTs. The advantage of this direct-writing approach for CNT formation is its positioned growth for future potential interconnect and field effect transistor application.
9:00 PM - DD12.19
Rational Synthesis of P-type Zinc Oxide Nanowire Arrays
Bin Xiang 1 , Pengwei Wang 2 , Xingzheng Zhang 2 , Shadi Dayeh 1 , David Aplin 1 , Cesare Soci 1 , Dapeng Yu 2 , Deli Wang 1
1 Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, United States, 2 Electron Microscopy Laboratory, School of Physics, Peking University, Beijing China
Show AbstractWe report the synthesis of the high-quality p-type ZnO NWs using a simple chemical vapor deposition method, where phosphorus pentoxide has been used as the dopant source. Single crystal phosphorus doped ZnO NWs have growth axis along the <001> direction and form perfect vertical arrays on a-sapphire. P-type doping was confirmed by photoluminescence measurements at various temperatures and by studying the electrical transport in single NWs field-effect transistors. Comparisons of the low temperature PL of unintentionally doped ZnO (n-type), as-grown phosphorus doped ZnO, and annealed phosphorus doped ZnO NWs show clear differences related to the presence of intra-gap donor and acceptor states. The electrical transport measurements of phosphorus doped NW FETs indicate a transition from n-type to p-type conduction upon annealing at high temperature, in good agreement with the PL results. The cross NW ZnO homojunction nano-LED and core-shell heterostructure device will be also discussed. The synthesis of p-type ZnO NWs enables novel complementary ZnO NW devices and opens up enormous opportunities for nanoscale electronics, spintronics, optoelectronics, and medicines.
9:00 PM - DD12.2
Polarization Photo-sensitivity of Randomly Oriented CdSe and CdTe Nanowires.
Vladimir Protasenko 1 , Gabor Galantai 1 , Huili(Grace) Xing 2 , Debdeep Jena 2 , Masaru Kuno 1
1 Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States, 2 Electronic Engineering, University of Notre Dame, Notre Dame, Indiana, United States
Show Abstract9:00 PM - DD12.20
Fabrication Of Piezoelectric Lead Zirconate Titanate Nanotubes By Spin Coating Of Sol-Gel Solution Using Porous Alumina Membranes.
Sang Don Bu 1 , Jongok Kim 1 , Yong Chan Choi 1 , Jin Kyu Han 1
1 Physics, Chonbuk National University, Jeonju Korea (the Republic of)
Show AbstractPiezoelectric nanotubes hold promise for applications in a variety of nanotechnological devices because these polycrystalline nanotubes can be strained when an electrical voltage is applied, and vice versa. Each tube could be triggered individually to release a small quantity of ink for ink-jet printing, or to deliver drugs into a patient. Sensor, actuator and data-storage applications are also possible.We report the fabrication of high aspect ratio (up to 400:1) piezoelectric Pb(Zr0.52Ti0.48)O3 (PZT) nanotubes by a spin-coating process of putting a sol-gel solution into a porous alumina membrane (PAM). PAMs with a pore diameter of about 50 nm were prepared in-house using a well-known two-step anodization procedure [1]. Sol-gel precursor solutions were also prepared in-house using a traditional sol-gel method in order to control the pH, mole concentration, viscosity, and composition of the sol-gel precursor solutions. PZT nanotubes were synthesized in PAM nanopores by a spin coating deposition technique described previously [2]. Briefly, a PAM was placed on a lab-made Teflon support, which was placed on a spin coater chuck, where the Teflon support was designed for the sol-gel precursor solution to flow well through the membrane pore. The precursor solution was dropped on the PAM using a micro pipette. It was then spin-coated at 1000 to 5000 revolutions-per-minute for 120 sec.High aspect ratio piezoelectric PZT nanotubes have been successfully fabricated. Field emission scanning electron microscopy (FESEM) images show that PZT nanotubes are well packed inside the pore of a PAM. Scanning transmission electron microscopy (STEM) analysis along with energy dispersive X-ray spectroscopy (EDS) mapping investigation of the nanotubes confirms the presence of lead, zirconium, and titanium. A field emission transmission electron microscopy (FETEM) image of a freestanding PZT nanotube shows that its outer diameter and length are estimated to be 50 nm and several microns, respectively. Further investigation reveals that PZT nanotubes have a wall thickness of 3 nm to 10 nm and consist of crystallites with a size in the order of 2-3 nm. The d-spacings for the rings in the electron diffraction pattern are 2.89 Å, 2.52 Å, 2.12 Å, 1.78 Å, 1.52 Å, and 1.39 Å. It suggests that our PZT nanotubes are a mixture of perovskite and pyrochlore phases. The majority of the tube is comprised of the perovskite PZT phase with a tetragonal structure [JCPDS 33-0784]. Our current concerns are the phase transformation from pyrochlore to perovskite and the electrical and electromechanical properties of a single PZT nanotube.[1] J. Kim, Y. C. Choi, K.-S. Chang, and S. D. Bu, Nanotechnology 17, 355 (2006).[2] Y. C. Choi, J. Kim, and S. D. Bu, Mater. Sci. Eng. B 133, 245 (2006).
9:00 PM - DD12.21
Synthesis of Unit Oriented MWNTs on SiO2 Particle.
Junming Xu 1 , Huibin Qin 1
1 College of electronic information, Hangzhou Dianzi University, Hangzhou, Zhejiang, China
Show Abstract9:00 PM - DD12.22
Controlled Synthesis of Single-Crystal Organic Nanowires of Cu-Phthalocyanine by Organic Vapor-Phase Deposition (OVPD) Method
Kai Xiao 1 , Jing Tao 2 , Ilia Ivanov 1 , Alex Puretzky 1 , HoNyung Lee 2 , Stephen Pennycook 2 , David Geohegan 1 2
1 Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Materials Science and Techonology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractMetal phthalocyanine is one of the promising organic compounds for possible applications in electrooptical devices, photoconducting agents, photovoltaic cell elements, nonlinear optics, electrocatalysis, and other optoelectronic devices. Several metal-substituted phthalocyanines have been widely investigated. Among the metal substituted phthalocyanines, copper (II) phthalocyanine (Cu-Pc) has attracted great attention for many years because of its combination of high thermal and chemical stability and outstanding optical and electronic properties. Hence Cu-Pc has been widely applied in gas sensors, xerography, optical disk, catalysis, electro-chromic display, organic solar cells, OLEDs, OFETs, and data storage devices. Cu-Pc is also expected to be a candidate material for optical detectors and non-linear optics with more tunable absorption band and lower cost than its inorganic counterparts. However, to date Cu-Pc has not been available in the form of well-controlled nanowires for new nanoscale applications which could take advantage of one-dimensionality to greatly enhance the performance of many currently existing devices. In this paper, the controlled synthesis of single-crystal organic nanowires of Cu-Pc by organic vapor-phase deposition are reported. The size, morphology and crystal structure of the Cu-Pc nanowires were principally determined by the substrate temperature. The transformation of the crystal structure of Cu-Pc nanowires with increasing substrate temperature from the alpha-phase of the orthorhombic crystal to the thermally stable beta-phase of the monoclinic crystal was studied by SEM, HRTEM, SAD, XRD and optical absorption spectroscopy. This well-controlled synthesis of Cu-Pc nanowires is very important for their application in electrical and optoelectronic devices, such as organic photovoltaic cells, organic light-emitting diodes, field-effect transistors, memories and gas sensors.This research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. Department of Energy, managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
9:00 PM - DD12.23
Synthesis and Properties of Boron Nitride Nanotubes, Nanowires and Nanorods.
Ying Chen 1 , Hua Chen 1 , Jun Yu 1 , Yongjun Chen 1 , Hongzhou Zhang 1
1 Department of Electronic Materials Engineering, The Australian National University, Canberra, Australian Capital Territory, Australia
Show Abstract9:00 PM - DD12.25
Synthesis and Transport Properties of Vapor-liquid-solid Grown Si1-xGex Nanowire.
Sung Jin Whang 1 , Sung Joo Lee 1 , Wei Feng Yang 1 , Hai Chen Zhu 1 , Han Lu Gu 1 , Byung Jin Cho 1 , Yun Fook Liew 2 1
1 ECE, National University of Singapore, Singapore, Singapore, Singapore, 2 , Data Storage Institute, Singapore, Singapore, Singapore
Show Abstract9:00 PM - DD12.26
General Route to Template-Directed Gas-Phase Fabrication of Oxide Nanotubes
Changdeuck Bae 1 , Bokyung Ahn 1 , Moonchul Kang 1 , Jiyoung Kim 2 , Myung Sung 3 , Hyunjung Shin 1
1 School of Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of), 2 Department of Electrical Engineering, University of Texas, Dallas, Texas, United States, 3 Department of Chemistry, Hanyang University, Seoul Korea (the Republic of)
Show AbstractWe present a high-throughput, one-step procedure for fabricating oxide nanotubes. Our approach combines template-directed atomic layer deposition (ALD) [1] with a micro-contact printing technique, allowing precise control over the dimensions of the nanotubes as well as one-step fabrication of free-standing oxide nanotubes. Metal oxide nanotubes made from TiO2, ZrO2, and Al2O3 with high aspect ratios of up to ~300 have been fabricated. Notably, two different types of membranes are employed as templates, track-etched polycarbonate and anodic aluminum oxide (AAO). We discussed that the nanopore sizes in growing those ALD layers play central role between growth rate and surface stress. The surface chemistry of selective ALD onto the templates is also addressed. Furthermore, it is speculated that bundles of oxide nanotubes are formed by strong capillary forces generated and exerted during dissolution of the surrounding AAO template in the fabrication of the oxide nanotubes.AcknowledgementThis work was supported by the Center for Nanostructured Materials Technology of the Korean Ministry of Science and Technology (M105KO010026-06K1501-02610).[1] H. Shin, D.-K. Jeong, J. Lee, M. M. Sung, J. Kim, Adv. Mater. 2004, 16, 1197.
9:00 PM - DD12.27
Self-Assembled Fluorocarbon Template for Growth of Nano-Scale Platinum.
Sang Hwui Lee 1 , Zhengchun Liu 1 , J. McMahon 1 , Jian-Qiang Lu 1
1 CIE, RPI, Troy, New York, United States
Show AbstractA self-assembled fluorocarbon template for platinum (Pt) nanostructure growth is demonstrated. This novel approach to realize metal nanostructures uses a fluorocarbon thin film made by reactive ion etching (RIE) of SiO2 followed by platinum sputtering. Fluorocarbon residues are generally considered as undesirable materials during the RIE of silicon or SiO2. However, under the conditions studied here, fluorocarbon nano-scale rings are spontaneously formed with typical dimensions as ~50nm of diameter, ~10nm wall thickness, and ~50nm high during the RIE of SiO2 with trifluoromethane (CHF3) and oxygen. These ring structures are used as a template for metal nanostructure growth. Pillar-like Pt nanostructures up to 100nm in height and 50nm in diameter are grown on the template simply by a sputterer of low-cost thin film coater in 3 minutes; with increasing sputtering time, Pt nanorod bundles are formed. The morphology and growth mechanism of fluorocarbon nano-rings and platinum nano-pillars will be discussed in detail. This work provides a simple approach to metal nanostructure growth for applications, such as fuel-cell using Pt nanorods as catalyst.
9:00 PM - DD12.28
Single-Crystalline Bismuth Telluride Nanowires Grown by a Stress-induced Method
Jinhee Ham 1 , Wooyoung Shim 1 , Seunghyun Lee 1 , Wooyoung Lee 1
1 Department of Materials Science and Engineering, Yonsei University , Seoul Korea (the Republic of)
Show AbstractHigh-efficient thermoelectricity requires materials with a large figure of merit, ZT, defined by ZT = σS2T/κ, where σ is the electrical conductivity, S the thermoelectric power, and κ the thermal conductivity. However, due to the interdependence of σ, S, and κ, the optimization of thermoelectricity remains challenging. It is well known that there are two approaches to enhanced ZT value. One is to utilize quantum confinement effects of nanostructures, providing an opportunity to individually control σ and S, and thus to promote ZT [1] because of increase of the density of states (DOS). The other is to reduce κ without having an effect on σ and S by using semiconductors of high atomic weight such as bismuth telluride (Bi2Te3) with much lower atomic vibration frequencies [2]. In this work, we present a new method to grow high-quality, single-crystalline Bi2Te3 nanowires for use as a thermoelectric material with high ZT. BixTe1-x (x = 0.35 ~ 0.55) thin films were grown on an oxidized Si substrate using a co-sputtering system with a Bi (99.999%) and a Te target (99.99%). For the growth of BixTe1-x nanowires, the co-sputtered films were transferred to a furnace for heart treatment in the temperature range 300 - 450°C. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) were employed for the structural characterizations of the nanowires. Interestingly, uniform and straight Bi2Te3 nanowires with high aspect ratios were found to grow on the surface of the co-sputtered films after heat treatment. The growth of the Bi2Te3 nanowires is attributable to the relaxation of stress, originating from a thermal expansion mismatch between the film and the substrate. This mismatch is due to the large difference in the coefficient of thermal expansion of BixTe1-x(~19 × 10-6/°C), SiO2(0.5 × 10-6/°C) and Si(2.4 × 10-6/°C). Elemental mapping profiles show the uniform distribution of Bi and Te along the length of a nanowire with d = 100 nm without appreciable segregation. The composition of BixTe1-x nanowires were found to be adjusted by tailoring the composition of co-sputtered films from x = 0.35 to 0.55. A HRTEM study reveals that the Bi2Te3 nanowire with d = 100 nm grown along the <110> direction is high-quality single crystalline. The diffraction pattern recorded perpendicular to the long axis of the nanowire can be indexed to the hexagonal lattice of Bi2Te3 (a = 4.43Å, c = 29.91Å) with [001] zone axis. The Bi2Te3 nanowires were found to have diameters ranging from 50 nm to 500 nm depending on the thickness of the co-sputtered BixTe1-x films, indicating that the diameter of Bi2Te3 nanowires is controllable. Our results demonstrate that single-crystalline Bi2Te3 nanowires can be grown by the stress-induced method, providing a motivation for exploring the high-efficiency thermoelectric properties of single-crystalline Bi2Te3 nanowires.[1] Y. Lin et. al., Phys. Rev. B 62, 4610 (2000)[2] A. Majumdar, Science 303, 777 (2004)
9:00 PM - DD12.29
Nitrogen Mediated Synthesis of Au/Carbon Nanotubes
Weon Ho Shin 1 , Seong Ho Yang 1 , Jeung Ku Kang 1
1 MSE, KAIST, Daejeon Korea (the Republic of)
Show AbstractRecently, transition metal nanoparticles dispersed carbon nanotubes have been considered as promising materials for potential applications such as hydrogen storage media, sensing materials, catalysts, or electronic devices. These applications require deep understanding of the nature of metal particle-carbon nanotubes interaction to achieve hybrid materials for desirable properties. For bio-sensing materials and catalysts, gold metal have been widely used due to its excellent stability of chemical and physical attack. Here, we report the interaction between carbon nanotubes and gold particles through density functional calculations. Calculations reveal that there is no interaction between pristine carbon nanotube and a gold atom. In this context, we introduced nitrogen atoms as extrinsic defects, which can substitute carbon atoms with graphitic like or pyridine like structure, resulting high binding energy between Au atom and nanotube. To compare with these theoretical results, we dispersed gold nanoparticles on carbon nanotubes and nitrogen doped carbon nanotubes. Nitrogen atoms could increase reactivity of carbon nanotubes, resulting more uniform distribution than pure carbon nanotubes. These hybrid materials can enhance catalytic or bio-sensing properties.
9:00 PM - DD12.3
One-dimensional Necklace of Metal Nanoparticles that Exhibits Coulomb Blockade at Room Temperature.
Jennifer Kane 1 , Vivek Maheshwari 1 , Ravi Saraf 1
1 , University of Nebraska-Lincoln, Lincoln, Nebraska, United States
Show Abstract9:00 PM - DD12.30
Pinching of Alkoxide Jets – a Route for Preparing Nanometre Level Sharp Oxide Fibres.
Tanel Tatte 1 , Kristjan Saal 1 , Ilmar Kink 1 , Uno Maeorg 2 , Runno Lohmus 1 , Ants Lohmus 1
1 Lab. Of Low Temperatures, Institute of Physics, Tartu, Tatu, Estonia, 2 Department of Organic Chemistry, Institute of Organic and Bioorganic Chemistry, Tartu Estonia
Show Abstract9:00 PM - DD12.31
Electron-beam Induced Growth of Silica Nanowires and Silica/Carbon Heterostructures
Francisco Sola 1 , Oscar Resto 1 , Azlin Biaggi-Labiosa 1 , Luis Fonseca 1
1 Physics, University of Puerto Rico, San Juan, Puerto Rico, United States
Show AbstractA novel synthesis of silica nanowires and silica/carbon heterostructures by electron beam irradiation on porous silicon films was investigated. The method allows us to monitor the growth process in real time at atomic scales. Depending on the electron dose we obtain nanowires with diameters in the range of 15-49 nm and lengths up to 500 nm. We found that the adequate electron dose was between 103-105 nm-2 s-1. Additional electron dose causes plastic and failure deformations in the silica nanowires. A growth model consistent with our findings is presented that involves the flow of mass from the substrate to the nanowire driven by the local electric fields. Heterostructures showing a nanopalm-like shape are obtained after exposing the silica nanowire to poor vacuum conditions in which carbon aggregation from the surrounding gas is promoted by the local electric fields enhanced at the tip of the silica wires.
9:00 PM - DD12.32
Ex-situ Doping and Characterization of Silicon Nanowires.
Sarang Ingole 1 , Pavan Aella 1 , Teresa Clement 1 , E. Akhadov 2 , S. Picraux 2 1
1 School of Materials, Arizona State University, Tempe, Arizona, United States, 2 Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos , New Mexico, United States
Show AbstractWe demonstrate the application of a solid state diffusion-based approach for electrical doping of vapor-liquid-solid (VLS) grown silicon nanowires. Electrical doping of silicon nanowires is essential for their application in nanoscale devices. In-situ doping during VLS growth has been shown by several groups as one technique for doping nanowires, however it has been observed that it can have undesired effects on morphology of nanowires thereby limiting application in some cases. Therefore it is technologically important to develop/investigate alternative techniques for electrical doping of nanowires. We have thus explored ex-situ approaches based on solid-state diffusion, a well established technique in current device manufacturing technology. In the present study we report proximity doping with a spin-on boron dopant source for electrical doping of VLS grown silicon nanowires. This is a two stage process where the first stage (pre-deposition) involves annealing the nanowire sample placed in proximity of a dopant source in the range 850-950°C. Here the spin-on dopant spun onto a sacrificial substrate acts as a controlled dopant source. During this stage boron from the dopant source is introduced into the nanowires. In a second stage (drive-in) nanowire samples are heated at 975°C without the spin on dopant source present. This results in further diffusion of boron into the nanowires. Secondary ion mass spectroscopy (SIMS) carried out on these doped nanowires confirmed the presence of boron for various concentrations and Transmission Electron Microscopy (TEM) shows that the structural integrity is maintained after this high temperature doping process without introduction of extended defects. Electrical characterization measurements are carried out in order to extract the resistivity and determine the approximate dopant concentrations. Preliminary two point probe measurements indicate total resistance of these nanowires in the range of ~104 Ohms. In order to separate contact resistance from actual resistance of nanowire, Electron-beam lithography (EBL) is being utilized to write four-probe contact arrangements. Present results show the feasibility of this technique for electrically doping nanowires and semiconductor nanostructures in general.
9:00 PM - DD12.33
Fabrication of Thermal Reduced Ag Nano-wires with Titanium Dioxide.
Hsien-Tse Tung 1 , Cheng-Wei Yen 1 , Tzu-Hsuan Kao 1 , Jenn-Ming Song 2 , Chang-Shu Kuo 1 , In-Gann Chen 1
1 Materials Science and Engineering, National Cheng-Kung University, Tainan Taiwan, 2 Materials Science and Engineering, National Dong Hwa University, Hualien Taiwan
Show Abstract9:00 PM - DD12.34
Selective Area Growth of ZnO Nanowires on Group III Oxide Nanowires/nanoparticles using Implantation-assisted Technique and MOCVD.
Kwong Chun Lo 1 , Hui Wang 1 , Ho Pui Ho 1
1 Electronic Engineering, The Chinese University of Hong Kong, Hong Kong Hong Kong
Show Abstract9:00 PM - DD12.35
Mesoporous Nanowires and Nanotubes Prepared from a Confined-Passembly-template Assisted Electrodeposition.
Hongmei Luo 1 , Yunfeng Lu 2 , Quanxi Jia 1
1 Superconductivity Technology Center, Materials Physics and Applications Division , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, California, United States
Show Abstract9:00 PM - DD12.36
Synthesis of Pyramidal Lead Sulphide (PbS) Thin Films by Employing Liquid-liquid Interface.
Dongbo Fan 1 , Peter Thomas 1 , Paul O'Brien 1
1 Shool of chemistry, University of Manchester, Manchester United Kingdom
Show Abstract9:00 PM - DD12.37
Polyol Mediated Design of Core-Shell Pd-on-Au Bimetallic Nanoparticles.
Domingo Ferrer 1 , Alejandro Torres-Castro 1 , Xiaoxia Gao 1 , Selene Sepulveda-Guzman 1 , Miguel Jose-Yacaman 1 2
1 Chemical Engineering, The University of Texas at Austin, Austin, Texas, United States, 2 , Texas Advanced Materials Center, Austin, Texas, United States
Show Abstract9:00 PM - DD12.38
Highly Water-Soluble Monodisperse Magnetic Iron Oxide Nanocrystals.
Yadong Yin 1 , Jianping Ge 1 , Yongxing Hu 1
1 Chemistry, University of California, Riverside, Riverside, California, United States
Show Abstract9:00 PM - DD12.39
Mixed-Surfactant-Templated Synthesis of Nanogroove-Network Structured Platinum Nanosheets and Their Electrochemical Characterization.
Tsuyoshi Kijima 1 2 , Takumi Yoshimura 1 2 , Go Sakai 1 2 , Shusaku Isohata 1 , Masafumi Uota 2 , Hideya Kawasaki 3 2 , Daisuke Fujikawa 1 2
1 Applied Chemistry, Miyazaki University, Miyazki-city Japan, 2 , CREST, Japan Science and Technology Agency, Miyazaki Japan, 3 Applied Chemistry, Kansai University, Suita Japan
Show AbstractNanoscale platinum particles have attracted particular attention because of their potential use as catalysts in various fields such as fuel cells. The catalytic reactivity of Pt nanoparticles used for these applications depends on their structural properties such as size, shape, and the arrangement of surface atoms. Various methods have been therefore developed for controlling the structural properties of Pt nanoparticles and fabricating unconventional Pt nanostructures such as nanorods, nanotubes, and 2D mesoporous solids. Our recent study also demonstrated the synthesis of Pt nanotubes by the reduction of H2PtCl6 with hydrazine in lyotropic mixed surfactant LCs of polyoxyethylene (20) sorbitan monostearate (Tween 60) and nonaethyleneglycol dodecylether (C12EO9). 1 In this paper, we report that the borohydride reduction of Na2PtCl6 confined to compositionally the same mixed surfactant LCs yields single-crystalline Pt nanosheets with a nanogroove-network structure, together with their fairly high electrocatalytic activity for oxygen reduction reaction (ORR) upon loading on carbon. In the typical reaction, Na2PtCl6, C12EO9, Tween 60, and H2O at a prescribed molar ratio were mixed at 60oC and then cooled to 20oC. The cooled LC material was reduced with an aqueous solution of NaBH4 (SBH). AFM, TEM and HRTEM observations revealed that the resulting solids are identified as nanogroove-network structured single crystalline Pt nanosheets of ~3.5 nm thick and 50-60 nm diameter. The nanosheets have pseudo 2D irregular Pt networks in which Pt nanoleaves of ~2.6 nm wide and 2-4 nm long are loosely interconnected with their crystallographic alignment to form an irregular network of nanogrooves ~1 nm in width. In contrast, the C12EO9-based single surfactant system yielded an aggregate of featureless nanoparticles and the Tween 60-based single system led to a 2D-aggregate of Pt nanoleaves loosely linked but with their different orientations. FT-IR analysis suggested that the stearate species produced by the hydrolysis of Tween 60 serve as a capping agent responsible for the growth of sheet-like Pt nanoparticles. The mixtures of Pt-salt containing LC and carbon powder (VXC72R) were prepared and then treated with an aqueous solution of SBH at various SBH/Pt molar ratios. The carbon supported Pt products thus obtained were characterized for the electrocatalytic ORR by cyclic voltammetry in 0.5 M H2SO4 saturated with dissolved oxygen. It was found that the nanogroove-structured Pt/C obtained at high SBH amounts shows fairly high electrocatalytic activity for ORR, in contrast to non-grooved Pt nanoparticles/C obtained at low SBH amounts, although the loading amounts of Pt for both Pt/C are almost the same. 1. T. Kijima et al., Angew. Chem., 2004, 43, 228.
9:00 PM - DD12.4
Size-dependent Quantum Efficiency and Radiative Lifetime of Si Nanocrystals Embedded in SiNx Films.
Jae-Heon Shin 1 , Chul Huh 1 , Kyung-Hyun Kim 1 , Jongcheol Hong 1 , Gun Yong Sung 1 , Yong-Hwan Kim 2 , Yong-Hoon Cho 2 , Joong-Kon Son 3
1 IT-Convergence Technology Research Div., Electronics and Telecommunications Research Institute, Daejeon Korea (the Republic of), 2 Department of Physics, Chungbuk National University, Cheongju Korea (the Republic of), 3 Photonics Program Team, Samsung Advanced Institute of Technology, Suwon Korea (the Republic of)
Show Abstract9:00 PM - DD12.40
Understanding Shape Control in Nanoparticle Synthesis.
Jeremy Gray 1 , Danxu Du 2 , David Srolovitz 3 , Christine Orme 1
1 Chemistry, Materials and life sciences, Lawrence Livermore National Laboratory, Livemore, California, United States, 2 Department of mechanical and aerospace engineering, Princeton University, Princeton, New Jersey, United States, 3 Department of Physics, Yeshiva University, New York, New York, United States
Show Abstract9:00 PM - DD12.41
Microwave Assisted Synthesis of Iron Oxide and Mixed Iron Oxide Nanoparticles.
Jason Parsons 1 , C. Luna 1 , C. Botez 2 , J. Elizalde 2 , J. Peralta Videa 1 , J. Gardea-Torresdey 1
1 Chemistry , University of Texas at El Paso, El Paso , Texas, United States, 2 Physics , University of Texas at El Paso , El Paso, Texas, United States
Show Abstract9:00 PM - DD12.42
Synthesis and Characterization of Nanoscale ZnO and MgO.
Peter Yaron 1 , Zhengwei Pan 2 , Andi Barbour 1 , J. Larese 1 2
1 Chemistry, University of Tennessee, Knoxville, Tennessee, United States, 2 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show Abstract9:00 PM - DD12.43
Formation of Silver Nanostructures on MgZnO hexagonal and Cubic Alloys
Shiva Hullavarad 1 , Nilima Hullavarad 1
1 Office of Electronic Miniaturization, University of Alaska, Fairbanks, Alaska, United States
Show Abstract9:00 PM - DD12.44
Probing and Tuning the Chemistry and Structure of Nanocrystalline Cerium Oxide.
Satyanarayana Kuchibhatla 1 2 , Ajay Karakoti 1 , Sudipta Seal 1 3 , Mark Engelhard 2 , Donald Baer 2 , Thevuthasan Suntharampillai 2
1 Advanced Materials Processing and Analysis Center, University of Central Florida, Richland, Washington, United States, 2 , Environmental Molecular Sciences Laboratory,Pacific Northwest National Laboratory, Richland, Florida, United States, 3 Nanoscience and Technology Center, University of Central Florida, Orlando, Florida, United States
Show Abstract9:00 PM - DD12.45
Synthesis and Characterization of Variable Pore Size, Ordered Cylindrical Nanopores in Alumina.
Michael Felty 1 , Paige Landry 1 , Andi Barbour 1 , J. Larese 1 2
1 Chemistry, University of Tennessee, Knoxville, Tennessee, United States, 2 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractWe report on our synthesis and characterization of well-defined, close packed, cylindrical channels in an alumina matrix. These materials have been systematically produced using an anodization process that provides the ability to tune the pore size while retaining the long-range hexagonal pattern. Characterization of these materials includes electron and scanning microscopies, x-ray diffraction and volumetric adsorption. We expect to employ these materials in the study of gas storage and quantum confinement. Numerous theories predict a dramatic change in the physical properties of gases and liquids constrained to spatial dimensions that are on the order of several nanometers. Modeling studies of gas adsorption within these channels will be presented if time permits. This work is supported by the Division of Materials Science, Office of Science, Basic Energy Sciences under contract DE-AC05-00OR22725 and the NSF under DMR-0412231.
9:00 PM - DD12.46
Nanoscale Site-Selective Nucleation and Growth on Planar and Colloidal Surfaces
Changdeuck Bae 1 , Hyunjung Shin 1
1 School of Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of)
Show AbstractSelf-assembly of small objects offers a powerful route for constructing functional, multidimensional structures, but the individual components being used is monotony or large. At nanoscale, selectively decorating the surfaces of the self-assembling objects could open a great deal of opportunity for their applications. We studied the site-specific heterogeneous nucleation and growth of inorganic materials at sub-100 nm length scale from organic templates on planar surfaces. The results suggest that high difference of surface energy between growing and surrounding surfaces leads to the complete site-selectivity. We also showed that this bottom-up approach can be applied to high curved surfaces (i.e., microspheres) in order to produce dielectrically anisotropic colloidal building blocks. Furthermore, we investigated the optical properties of the selectively grown nanodots arrays on both planar and colloidal surfaces in terms of photonic band gap.
9:00 PM - DD12.47
Fabrication of Doped ZnO(Mn, Co) Nanostructures with Room Temperature Ferromagnetism by Chemical Vapo Deposition.
Jingjing Liu 1 , Amber West 1 , Minghui Yu 1 , Weilie Zhou 1
1 , Advanced Materials Research Institute, New Orleans, Louisiana, United States
Show AbstractMn and Co doped ZnO diluted magnetic semiconductor (DMS) nanostructures were prepared by direct reaction of zinc with manganese chloride powder and cobalt acetate, respectively, under oxygen environment using chemical vapor deposition (CVD) method. Several kinds of nanostructures, such as nanowire arrays, bowls/cages, and nanoneedles were obtained. The morphologies and crystal structures of the as-synthesized nanostructures were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and x-ray diffraction spectroscopy (XRD). Superconducting quantum interference device (SQUID) measurement shows that the doped nanowire arrays, nanocrystalline bowls/cages and cactus-like nanoneedles have ferromagnetic ordering above room temperature. The fabrication of spintronic nanotransistors will be also discussed.
9:00 PM - DD12.48
Position-controlled Heteroepitaxial Growth of InAs Nanowires on Lattice-mismatched Substrates by Selective Area Metalorganic Vapor Phase Epitaxy.
Katsuhiro Tomioka 1 , Junichiro Takeda 1 , Ling Yang 1 , Shinjiroh Hara 1 , Junichi Motohisa 1 , Takashi Fukui 1
1 , Graduate School of Information Science and Technology and Research Center for Integrated Quantum Electronics, Hokkaido University, Sapporo Japan
Show Abstract9:00 PM - DD12.6
Deformation of Top-Down and Bottom-Up Metallic Nanowires.
Austin Leach 1 , Matt McDowell 1 , Ken Gall 1 2
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 George Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractIn terms of fabrication, nanowires may be separated into two genres, top-down and bottom-up. Top-down implies the extraction of nanowires from a bulk material in a material removal approach, while bottom-up classifies nanowires that have been grown through chemical or molecular assembly. The fabrication methods differ in the crystallographic pathway traversed en route to a minimum energy, equilibrium structure. In general, the equilibrium structure of a metallic nanowire is characterized by two crystallographic features: the lattice orientation along the nanowire length and the orientation of the free surfaces. In both fabrication genres, for nanowires of face-centered-cubic structure, the most energetically favorable axial orientation lies along the <110> direction. The difference in top-down and bottom-up fabrication is realized in the internal structure and orientation of the nanowire free surfaces. For example, chemical growth of silver nanowires commonly results in five-fold twinned, pentagonal nanowires with {100} surfaces; where as electron-beam irradiation of thin films (a top-down approach) may result in nanowires with a rhombic cross-section formed by four {111} surfaces or a truncated-rhombic cross-section arising from a combination of {100} and {111} surfaces. As the dimensions of a material are reduced to the nanometer scale, the dependence of material properties on material structure is greatly enhanced. In this work, we relate the physical structure of experimentally observed, inherently stable top-down and bottom-up silver nanowires to mechanical properties. Using atomistic simulations, we probe the tensile deformation behavior of rhombic and truncated-rhombic nanowires, representative of top-down fabrication and five-fold twinned, pentagonal nanowires representing bottom-up fabrication. Our results demonstrate that the mechanical properties and operant deformation mechanisms in metallic nanowires are strongly dependent on the cross-sectional geometry and internal structure of the nanowires. We also investigate the size dependence of the mechanical properties of the nanowires ranging from 1-25 nanometers in diameter, a phenomenon that is readily explained by the differences in physical structure of the top-down and bottom-up nanowires. This work has application not only for the design of future nanometer scale devices, but also provides a fundamental understanding of the effects of physical structure on the mechanical behavior of nanometer scale materials.
9:00 PM - DD12.7
Optical Properties of III-metal Nanoparticles/semiconductor Systems.
Pae Wu 1 , Maria Losurdo 1 2 , Tong-Ho Kim 1 , Giovanni Bruno 2 , April Brown 1
1 Electrical and Computer Engineering, Duke University, Durham, North Carolina, United States, 2 , Institute of Inorganic Methodologies and of Plasmas - CNR and INSTM, Bari Italy
Show Abstract9:00 PM - DD12.8
Enhanced Optical Properties of Au/ZnO core/shell Nanocrystals.
Myung-Ki Lee 1 , Yun-Mo Sung 1
1 Materials Sci. & Eng., Korea University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - DD12.9
Multi-Phase Titania Nanoparticles for High-Performance Photocatalyst
Yun-Mo Sung 1 , Jun-Su Park 1
1 Materials Sci. & Eng., Korea University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - DD12
DD12.24 TRANSFERRED TO DD3.11/EE2.11
Show Abstract
Symposium Organizers
Moonsub Shim University of Illinois, Urbana-Champaign
Masaru Kuno University of Notre Dame
Xiao-Min Lin Argonne National Laboratory
Ruth Pachter Air Force Research Laboratory
Sanat Kumar Rensselaer Polytechnic Institute
DD13: Devices and Applications of Low Dimensional Materials I
Session Chairs
Robert Hamers
Margaret Hines
Xiao-Min Lin
Thursday AM, April 12, 2007
Room 2001 (Moscone West)
9:00 AM - DD13.1
Architectural Design, 1-D Walls, 3-D Plumbing, and Interior Design en route to Multifunctional Nanoarchitectures
Debra Rolison 1 , Jeffrey Long 1
1 Surface Chemistry Branch, Naval Research Laboratory, Washington, District of Columbia, United States
Show AbstractRate-critical applications require facile transport of reactant and charge carriers for high performance [1]. Aerogels and ambigels, which are sol–gel-derived ultraporous, aperiodic nanoarchitectures, unite high surface area for heterogeneous reactions with a continuous, porous network for rapid diffusional flux of molecules. Response times to gas-phase analytes are >10 times faster than those of the same chemistry expressed as a xerogel [2,3]. The surface area is expressed by "walls" that are defined by the nanoscopic, covalently bonded, one-dimensional solid network of the gel. The vast open, interconnected space characteristic of a building is represented by the interpenetrating nanoscopic pore network ("3-D plumbing"). Combining the 1-D interconnected nanoscopic solid with the 3-D interconnected nanoscopic pore network creates nanoarchitectures that yield high performance in rate-critical applications. In one example, the nanoarchitecture imposes electrical pathways along the low-dimensional network to yield macroscopic diffusion lengths for transport of ions from over a temperature range from ambient to 600°C. An architectural viewpoint provides a powerful metaphor to guide the chemist and materials scientist in the design of aerogel-like nanoarchitectures and in their physical and chemical transformation into multifunctional objects that yield high performance for rate-critical applications. [1] D.R. Rolison, Science 299 (2003) 1698.[2] N. Leventis, I. Elder, D.R. Rolison, M.L. Anderson, C.I. Merzbacher, Chem. Mater. 11 (1999) 2837.[3] J.M. Wallace, J.K. Rice, J.J. Pietron, R.M. Stroud, J.W. Long, D.R. Rolison, Nano Lett. 3 (2003) 1463.[4] M.S. Doescher, J.J. Pietron, B.M. Dening, J.W. Long, C.P. Rhodes, C.A. Edmondson, and D.R. Rolison, Anal. Chem. 77(2005) 7924.[5] C. Laberty-Robert, J.W. Long, E.M. Lucas, K.A. Pettigrew, R.M. Stroud, and D.R. Rolison, Chem. Mater. 18 (2006) 50.
9:15 AM - DD13.2
Fabrication and Transport Characterization of Embedded Vertical Ge Nanowires
Paul Leu 1 , Terry Hou 2 , Kyeongjae Cho 3 , Paul McIntyre 2
1 Mechanical Engineering, Stanford University, Stanford, California, United States, 2 Materials Science, Stanford University, Stanford, California, United States, 3 Physics, University of Texas at Dallas, Dallas, Texas, United States
Show AbstractGermanium nanowires (NWs) are a promising material for electronic and photonic devices due to the high carrier mobilities of Ge and the low temperatures required for Ge NW growth. We demonstrate an approach to integrate <111> Ge NWs into vertical arrays suitable for programmable interconnects and sensors. The transport properties of these Ge NWs as a function of length and diameter are characterized by experiments and theory. Ge NWs are grown vertically from Au catalysts dip coated onto a degenerately doped <111> Si substrate. SiO_2 is conformally deposited by plasma enhanced chemical vapor deposition around the vertical NWs to isolate and provide mechanical stability to the wires, followed by chemical mechanical polishing to planarize the structure. The tips of the NWs are exposed and can be contacted and electronically characterized through the deposition of top metal layer contact or with a conductive atomic force microscope. We compare trends in the experimental electrical transport properties of Ge NWs with simulation results from a Non-Equilibrium Green's function technique within an sp^3d^5s* tight-binding approximation.
9:30 AM - DD13.3
Magnetic Separation and Water Treatment with Monodisperse Fe3O4 Nanocrystals.
John Mayo 1 , Cafer Yavuz 1 , William Yu 1 , Arjun Prakash 2 , Joshua Falkner 1 , Sujin Yean 3 , Lili Cong 3 , Heather Shipley 3 , Amy Kan 3 , Mason Tomson 3 , Douglas Natelson 4 , Vicki Colvin 1
1 Chemistry, Rice University, Houston, Texas, United States, 2 Chemical and Biomolecular Engineering, Rice University, Houston, Texas, United States, 3 Civil and Environmental Engineering, Rice University, Houston, Texas, United States, 4 Physics and Astronomy, Rice University, Houston, Texas, United States
Show AbstractMagnetic separations can be applied to diverse problems, such as household water purification and the simultaneous separation of complex mixtures. High–surface area and monodisperse magnetite (Fe3O4) nanocrystals were shown to respond to low fields in a size-dependent fashion. The particles apparently do not act independently in the separation but rather reversibly aggregate through the resulting high-field gradients present at the surfaces. Using the high specific surface area of Fe3O4 nanocrystals that were 12 nanometers in diameter, we reduced the mass of waste associated with arsenic removal from water by orders of magnitude. Additionally, the size dependence of magnetic separation permitted mixtures of 4- and 12-nanometer–sized Fe3O4 nanocrystals to be separated by the application of different magnetic fields.
9:45 AM - DD13.4
Biological Applications of Phase Separated Gold Nanoparticles.
Oktay Uzun 1 , Darrell Irvine 1 , Francesco Stellacci 1
1 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show Abstract10:00 AM - **DD13.5
Directed Assembly and Real-time Detection of Nanowire Bridges for Direct Digital Sensing
Robert Hamers 1 , Bo Li 1 , Lu Shang 1 , Joe Beck 1 , Ed Perkins 2
1 , University of Wisconsin, Madison, Wisconsin, United States, 2 , Army Environmental Lab, Vicksburg, Mississippi, United States
Show AbstractWe are investigating the use of electrical fields combined with biomoleculare recognition events to create new types of hybrid nano-bio devices. By coupling AC dielectrophoresis with a flow, nanowires can be controllably guided along electrodes into a gap. AC impedance measurements show that nanowire bridging and un-briding events can be detected in real time. This combination provides a pathway toward automated assembly of nanoscale structures. By combining this manipulation with biomolecular recognition, it is possible to create devices that are essentially chemically- or biologically-actuated "fuses", in which a recognition event includes cleavage of a nanowire bridge. We demonstrate the real-time detection and such a nanowire "unbridging" event as a proof-of-principle.
10:30 AM - DD13.6
A Self-Assembled, Nanoparticle Based Tactile Sensor with Sensitivity & Resolution of Human Finger.
Vivek Maheshwari 1 , Ravi Saraf 1
1 Chemical Engineering, University of Nebraska Lincoln, Lincoln, Nebraska, United States
Show Abstract10:45 AM - DD13.7
Glycine-coated Single Walled Carbon Nanotube Field Effect Transistors (SWNT-FETs) for Alcohol Specific Sensor Applications.
Hyun Jae Song 1 , Hee Cheul Choi 1
1 chemistry, Pohang University of Science and Technology, Pohang, Kyungbuk, Korea (the Republic of)
Show Abstract11:30 AM - DD13.8
Schottky, p-n Junction and Light Emitting Diodes Employing (In,Ga)N Nanorod Heterostructures.
Parijat Deb 1 2 , Hogyoung Kim 4 2 , Yexian Qin 4 2 , Roya Lahiji 4 2 , Mark Oliver 1 2 , David Ewoldt 1 2 , Ron Reifenberger 4 2 , Timothy Sands 2 1 3
1 Materials Engineering, Purdue University, West Lafayette, Indiana, United States, 2 Birck Nanotechnology Center, Purdue University, Weat Lafayette, Indiana, United States, 4 Physics, Purdue University, Weat Lafayette, Indiana, United States, 3 Electrical Engineering, Purdue University, Weat Lafayette, Indiana, United States
Show Abstract11:45 AM - DD13.9
Lead Chalcogenide Nanowires and Hyperbranches for Multiexciton Generation Solar Cells
Yi Cui 1 , Jia Zhu 1 , Hailin Peng 1
1 , Stanford University, Stanford, California, United States
Show AbstractIncorporating multiexciton generation (MEG) into solar cells can potentially increase the power conversion efficiency dramatically. MEG been demonstrated in lead chalcogenide nanocrystals by Klimov and Nozik. Here we report the synthesis and measurements on lead chalcogenide nanowires towards MEG solar cells. We show that nanowire and hyperbranched network structures can be synthesized via a vapor-liquid-solid (VLS) growth. The epitaxial growth can be achieved using cheap NaCl substrates. The electron transport and MEG measurements in these nanowires will be discussed.
12:00 PM - **DD13.10
Quantum Dot Synthesis - The Journey from Milligram to Kilogram.
Margaret Hines 1
1 , Evident Technologies, Troy, New York, United States
Show AbstractMethods to produce high quality quantum dots have been rooted in the literature for well over a decade. Originally they required reagents that were expensive and dangerous to handle. The methods evolved and now utilize significantly cheaper and easier to handle reagents making large scale production and commercial manufacture of quantum dots readily feasible. In turn, applications harnessing QD technology are no longer academic demonstrations but rather on the frontline of product development throughout industry worldwide. Evident Technologies is a forerunner in the manufacture of quantum dots and in the research and development of products for the life sciences, security and markings, and LED/displays markets. In this talk I will present an industrial perspective of quantum dot synthesis. The challenge is not merely an issue of scaling but extends to consistently producing high quality materials that meet product specifications across an array of applications. Accordingly, we are utilizing the insight gained from the scale-up of current products in the development of new quantum dot materials.
12:30 PM - DD13.11
Growth and Characterization of InAs Quantum Dot Enhanced Photovoltaic Devices.
Seth Hubbard 1 , Ryne Raffaelle 1 , Ross Robinson 1 , David Wilt 2 , Sheila Bailey 2
1 Physics, Rochester Institute of Technology, Rochester, New York, United States, 2 Photovoltaic and Space Environment Branch, NASA Glenn Research Center, Cleveland, Ohio, United States
Show AbstractRecent proposals have pointed to alternate approaches to improving solar cell efficiency using low dimensionality nanostructured materials. Insertion of low dimensional heterostructures (i.e., quantum dot arrays) into the intrinsic region of a single junction p-i-n solar cell may lead to formation of an intermediate band. Theoretical studies have predicted such an approach could yield a photovoltaic efficiency near 63%. In this paper, Organometallic Vapor Phase Epitaxy (OMVPE) was used to: first, optimize InAs quantum dot (QD) growth on GaAs; and secondly, grow GaAs PIN solar cells with the optimized QDs. The effects of substrate offcut, QD growth temperature, and V/III ratio were studied using photoluminescence spectroscopy (PL), PL mapping, and atomic force microscopy (AFM). Higher growth temperatures resulted in improved QD density and PL intensity. The V/III ratio also had a strong effect on the uniformity of QD nucleation across the wafer, with a lower V/III ratio resulting in improved distributions in size and coherence. The optimal QDs had a size and density of 7×40nm and 5(±0.5)×1010 cm-2, respectively. PL spatial maps show the QD size (peak PL wavelength) and coherence (PL intensity) across the 2” wafer varied by 0.3% and 16 %, respectively. Quantum dot arrays with 5 layers were grown using the optimized growth conditions. A 10 nm GaAs spacer layer was grown between each dot layer. The PL peak for the stacked dots was centered near 1.08 eV, indicating a slight decrease in dot size. PL mapping showed a wavelength (dot size) and intensity (coherence) distribution across the wafer of 2.5% and 24%. In addition to the standard stack of 5 QD layers, a strain compensated version was also grown. In this case, a 1nm GaP strain compensated layer was inserted into the 10 nm GaAs spacer layer. PL peak wavelength was still centered near 1.08 eV and the mapping showed a wavelength uniformity of 2.5%. However, PL intensity was doubled in magnitude and the uniformity improved to 11%. Four GaAs PIN solar cells were then grown: (1) a standard PIN cell without QDs, (2, 3) cells with both 1 and 5 layers of QD in the i-region, and (4) and a cell with 5 layers of strain compensated QDs in the i-region. An array of 1 cm2 solar cells was fabricated on each type of wafer, IV curves were collected under AM0 conditions, and the spectral response was measured from 300-1100 nm. The spectral response for each QD cell clearly shows sub bandgap conversion, indicating adsorption due to the QDs. Unfortunately, the 1 and 5 layer uncompensated QD solar cells show degraded efficiency. However, the strain compensated QD cell shows clear efficiency and power improvements over either of the 1 and 5 layer uncompensated QD cells, as well as the subgap conversion. In addition to the efficiency, the other solar cell performance metrics will be discussed for both the baseline and QD cells.
12:45 PM - DD13.12
Silicon and Silicon-Germanium Nanorod and Nanorod Array Synthesis for Solar Cell Applications.
Brendan Kayes 1 , Michael Filler 1 , Morgan Putnam 1 , Michael Kelzenberg 1 , Julie Biteen 1 , Harry Atwater 1
1 Applied Physics, California Institute of Technology, Pasadena, California, United States
Show AbstractSilicon and silicon-germanium nanorod arrays have the potential to enable low-cost, high efficiency solar cells via efficient radial minority carrier collection in materials with low minority carrier diffusion lengths [1]. This can be achieved by creating an optically thick array of nanorods aligned normal to a substrate in which each nanorod has a radial pn junction, enabling light absorption along the entire rod length but minority carrier collection along the rod minimum dimension in the radial direction. Silicon and silicon-germanium nanorods for photovoltaic applications have been grown by a vapor-liquid-solid (VLS) chemical vapor deposition (CVD) process on silicon and germanium substrates from 5% silane or germane diluted in argon using both gold and indium as catalysts. Catalyst particles were formed either by lithography or by partial de-wetting of vapor-deposited films of the catalyst material to form droplets with diameters of tens to hundreds of nanometers. Via lithographic catalyst particle patterning, silicon nanorods were grown with diameters of 100 nm to microns and lengths of microns to tens of microns. Dense arrays of silicon nanorods highly-aligned normal to the substrate were achieved with substrate temperatures of 500-550°C and a total pressure of 1 Torr. Varying flow rate between 40 and 200 sccm was found to have relatively little effect on the results. Silicon-germanium nanorods were also prepared by initially growing silicon nanorods and switching to a germane source, as well as reducing the substrate temperature to 300°C, halfway through the deposition process.Photoluminescence (PL) decay lifetime measurements acquired at 1125 nm for silicon nanorod arrays prepared using gold catalysts indicate a minority carrier lifetime on the order of 1 μs. Four-point probe measurements performed on individual nanowires indicate that nominally undoped 1 μm diameter rods grown by CVD synthesis have a resistivities of 2.5 kΩ-cm, corresponding to an electrically-active doping concentration of approximately 1013 cm-3, while boron-doped rods grown using a silane/trimethylboron (141 ppm) mixture yielded resistivities on the order of 0.1 Ω-cm, corresponding to an electrically-active doping concentrations greater than 1017 cm-3. Photoconductivity was observed in individual nanowires illuminated at 514 nm.[1] Kayes, Atwater, and Lewis, J. Appl. Phys., 97, 114302 (2005).
DD14: Devices and Applications of Low Dimensional Materials II
Session Chairs
Thursday PM, April 12, 2007
Room 2001 (Moscone West)
2:30 PM - **DD14.1
Nanowire Building Blocks for Photonics & Electronics
Peidong Yang 1
1 , University of California, Berkeley, California, United States
Show AbstractNanowires are of both fundamental and technological interest. They represent the critical components in the potential nanoscale electronic and photonic device applications. Achieving high level of synthetic control over nanowire growth allows us to explore some of their very unique physical properties. For example, semiconductor nanowires can function as self-contained nanoscale lasers, sub-wavelength optical waveguides, frequency converters and photodetectors. It was also discovered that the thermoconductivity of the silicon nanowires can be significantly reduced when the nanowire size in the 20 nm region, pointing to a very promising approach to design better thermoelectrical materials for energy conversion. In this talk, I will outline our recent efforts in the direction of using nanowires for photonics, electronics and energy conversion applications.
3:00 PM - DD14.2
New Maskless Process for Directed Assembly of Nanowire Electrical Contacts.
Sarang Ingole 1 , Pavan Aella 1 , S. Hearne 2 , S. Picraux 3 1
1 School of Materials, Arizona State University, Tempe, Arizona, United States, 2 Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico, United States, 3 Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractA new approach to electrically contacting semiconducting nanowires is presented. Studies of silicon nanowires for novel field-effect transistor elements and chemical/biological sensors have shown promising results. However every study that exploits electrical control of nanowire properties first requires the establishment of good electrical contact to the nanowire. Previous approaches have shown that electron beam litholography is very useful in establishing metal-nanowire contacts for exploratory studies, but this technique is slow and hence not suitable for mass fabrication. While there have been other techniques reported that are promising for mass assembly of electrical contacts to nanowires onto a device platform, they require either a post nanowire assembly photolithography step which increases cost and processing complexity, or a specific substrate orientation which may not always be possible when nanowires are to be integrated onto a chip with other devices. Thus new techniques that are easy to integrate, low cost and involve minimum additional time are needed for integration of nanowires onto device platforms. In the present work we report a maskless process for establishing metal contacts to silicon nanowires. In the first step of our process nanowires are aligned using dielectrophoresis between pairs of planar metal electrodes that have been photolithographically defines on top of oxidized silicon substrate. After alignment the nanowires are held in place by the Van der Waals attraction with the electrodes. In order to get good electrical contacts to the two ends of such nanowires one needs to deposit metal on top of them. One way to achieve this is to perform a photolithography step followed by metal deposition. However present work renders such a photolithography step unnecessary and therefore we call it a maskless process. This is achieved through the use of electroplating, which is routinely used in the semiconductor industry. The prefabricated metal electrodes act as selective sites for metal deposition during electroplating with the ends of the nanowires becoming encapsulated by the plated metal. We demonstrated this process using electrodeposited nickel on electrically doped Si nanowires. Good coverage and control for nanowires aligned between Au/Cr pre-deposited electrodes was achieved and post-electroplating annealing resulted in low contact resistances (~10KOhm). The results are promising for development of a general mass-level integration technique for nanostructures on device platforms.
3:15 PM - DD14.3
High Performance Silicon Nanowire Transistors by the Self-assembling ``Grow-in-Place" Approach.
Yinghui Shan 1 , Stephen Fonash 1
1 Center for Nanotechnology Education and Utilization, The Pennsylvania State University, University Park, Pennsylvania, United States
Show Abstract3:30 PM - DD14.4
Ultra-large Scale Directed Assembly of Single-walled Carbon Nanotube Devices.
Aravind Vijayaraghavan 1 , Sabine Blatt 1 , Matti Oron-Carl 1 , Frank Hennrich 1 , Horst Hahn 1 , Ralph Krupke 1
1 Institut für Nanotechnologie, Forschungszentrum Karlsruhe, Karlsruhe Germany
Show AbstractDespite the rapid progress in understanding the electronic transport behavior of single-wall carbon nanotubes and their numerous potential applications in nano-electronics, the fabrication of nanotube devices still remains the biggest obstacle in the way of practical realization of their enormous potential. In this presentation, we demonstrate the use of A/C dielectrophoresis to fabricate individual nanotube devices on a large scale. We have achieved densities of 3 – 4 million devices/cm2, which is many orders of magnitude greater then anything that is possible with other methods. This density is comparable to the current level of microelectronics complexity, namely Ultra-Large Scale Integration (ULSI). We also show an added advantage of this technique, in that it is a self-limiting process, allowing only an individual nanotube to deposit between the electrodes for each device, which is highly desirable for controlled device fabrication. We include finite-element simulations of the dielectrophoretic force experienced by the nanotube, in order to illustrate this self-limiting behavior. In addition to these primary achievements, we also present a new, two-layer metallization technique, which surrounds the ends of the nanotubes in metal. This is unlike other fabrication techniques where the nanotube lies either on top or underneath the metal only. By this method, we provide a robust and reliable way significantly reduce the metal-nanotube contact resistance. Systematic electrical characterization of our devices is also presented. The techniques and discussions presented here are not merely limited to carbon nanotubes. In fact, dielectrophoresis is a universal phenomenon observed in a number of nano-scale objects like nano-wires, nano-particles, and even biological molecules and cells. The results in the presentation have universal appeal as they can be adapted and extended to form large-scale systematic electrical contacts to any number of such nano-scale objects. Dielectrophoresis can also be used to fabricate other nanotube structures, such as thin conducting films, and also to separate nanotubes according to their electronic properties (see contribution "Upscaling dielectrophoretic nanotube separation and probing dielectrophoretic force fields" by S. Blatt et.al.)
3:45 PM - DD14.5
Schottky-Barrier Si Nanowire MOSFET: Effects of Source/Drain Metals and Gate Dielectrics.
Weifeng Yang 1 , Sung Jin Whang 1 , Sung Joo Lee 1 , Haichen Zhu 1 , Hanlu Gu 1 , Byung Jin Cho 1
1 ECE department, SNDL, NUS, Singapore Singapore
Show Abstract4:00 PM - DD14.6
Modeling the Carrier Mobility in InAs Nanowire Channel FET.
Werner Prost 1 , Quoc-Thai Do 1 , Ingo Regolin 1 , Kai Blekker 1 , Franz-Josef Tegude 1
1 Solid-State Electronics Department, University Duisburg-Essen, Duisburg Germany
Show AbstractDD15: Synthesis and Characterization of Nanoscale Materials I
Session Chairs
Masaru Kuno
Moonsub Shim
Peidon Yang
Thursday PM, April 12, 2007
Room 2001 (Moscone West)
4:30 PM - **DD15.1
Synthesis and Characterization of Ultrathin Nanorods, Nanowires, and Nanoribbons of Oxides and Chalcogenides
Taeghwan Hyeon 1 2 , Taekyung Yu 1 2 , Kwangjin An 1 2 , Sang-Hyun Choi 1 2 , Jung Ho Yu 1 2 , Jin Joo 1 2
1 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of), 2 National Creative Research Center for Oxide Nanocrystalline Materials, Seoul National University, Seoul Korea (the Republic of)
Show AbstractUniform-sized ultra-thin nanorods and nanowires of lanthanide oxides were synthesized via non-hydrolytic sol-gel reactions. Ceria (CeO2) nanowires with a uniform diameter of 1.2 nm and a length of 115 nm were synthesized [Angew. Chem. Int. Ed. 2005, 44, 7411]. We synthesized novel tadpole-shaped nanowires consisted of spherical head with a diameter of 3.5 nm and wire-shaped ail with a diameter of 1.2 nm and length of 27 nm. We synthesized uniform rectangular shaped samaria nanowires with uniform cross-section dimensions of 1.1 nm × 2.2 nm [J. Am. Chem. Soc 2006, 128, 1786]. Uniform sized pencil-shaped CoO nanorods with an extraordinary wurtzite ZnO crystal structure by the thermal decomposition of a cobalt-oleate complex [J. Am. Chem. Soc 2006, 128, 9753]. The simultaneous phase- and size-controlled synthesis of TiO2 nanorods was achieved via the non-hydrolytic sol-gel reaction of continuously delivered two titanium precursors using two separate syringe pumps [J. Phys. Chem. B 2006, in press]. We reported low temperature solution-phase synthesis of one-dimension (1-D) quantum confined CdSe nanoribbons with uniform and ultrathin thickness of 1.4 nm [J. Am. Chem. Soc 2006, 128, 5632]. Very interestingly, the room temperature photoluminescence spectrum of the CdSe nanoribbons showed a sharp peak at 2.74 eV (451 nm) with an unprecedented narrow band of a full width at half-maximum (FWHM) of as small as 70 meV (11 nm). We successfully doped Mn(II) ions into the 1.4 nm thick CdSe nanoribbons. We synthesized the Cu-In sulfide heterostructured nanocrystals from the thermal decomposition of a mixture of Cu-oleate and In-oleate complex in dodecanethiol. By varying the reaction temperature and time, we were able to synthesize Cu-In sulfide nanocrystals with acorn, bottle, and larva shapes [J. Am. Chem. Soc 2006, 128, 2520].
5:00 PM - DD15.2
Growth and Properties of Superconducting Anisotropic Lead Nanoprisms
Xiao-Min Lin 1 , Helmut Claus 2 , Ulrich Welp 2 , Igor Beloborodov 2 , Laura Adams 3 , Wai-Kwong Kwok 2 , George Crabtree 2 , Heinrich Jaeger 3
1 Center for Nanoscale Materials, Argonne National Lab, Argonne, Illinois, United States, 2 Materials Science Division, Argonne National Laboratory, Argonne , Illinois, United States, 3 The James Franck Institute, University of Chicago, Chicago, Illinois, United States
Show AbstractAnisotropic shaped Pb nanoprisms were synthesized using high temperature polyol reduction of lead acetylacetonate through a kinetically controlled synthesis. Transmission electron microscopy studies showed the majority of the prisms grows along {111} planes while nanowires grow in various directions. SAED on single prism revealed the anisotropic growth is due to twinning in the growing nuclei. Magnetic measurements showed a large magnetic hysteresis that is due to the penetration and pinning of magnetic vortices. The flux trapping behavior could be due to type-I intermediate state caused by a large shape induced demagnetization factor or a possible transition from type-I to type-II superconductor due to finite thickness of the prisms.
5:15 PM - DD15.3
Cetyltrialkylammonium Bromide Mediated Growth of Gold Nanorods and Bipyramids
Chia-kuang (Frank) Tsung 1 2 , Xiaoshan Kou 2 , Jianfang Wang 2 , Galen Stucky 1
1 Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California, United States, 2 Department of Physics, Chinese University of Hong Kong, Shatin Hong Kong
Show AbstractGold nanorods have been prepared in high yields using a one-step seed-mediated process in aqueous cetyltrialkylammonium bromide solutions in the presence of silver nitrate. In order to explore the effect of the head group size on the growth of nanorods and to have better control of the synthesis, surfactants (cetyltrialkylammonium bromide) with different head groups have been used to synthesize gold nanorods. The diameters of the nanorods range from 3 to 11 nm, their lengths are in the range of 15 to 350 nm, and their aspect ratios are in the range of 2 to 70. These Au nanorods are single-crystalline and oriented in either the [100] or [110] direction under transmission electron microscopy imaging, irrespective of their sizes. The systematic study of the synthesis of gold nanorods indicates unambiguously that the average aspect ratios of the Au nanorods generally increase and the nanorod growth rates decrease as the cationic surfactant head group becomes larger. To the best of our knowledge, this is the first report on the preparation of single-crystalline Au nanorods that have aspect ratios larger than 15 using wet-chemistry methods. Furthermore, by using penta-twinned seeds instead of single crystal seeds during the synthesis, gold nano bipyramids can be synthesized. Transmission electron microscopy characterizations reveal that the gold bipyramids are penta-twinned. The diameters and lengths of the bipyramids are also tunable by varying the amount of the seeds and using surfactants with different head groups and the longitudinal plasmon wavelength of the bipyramids ranges from 700 nm to 1300 nm. It is interesting to note the sharp and intense of the extinction peak generated by longitudinal surface plasmon mode of the gold bipyramids. Compared with gold nanorods, the sharpness and intensity extinction peak has stronger potential for application in bio imaging and signal enhancement.
5:30 PM - DD15.4
Plasmonic and Structural Effects in the Growth of Ag Triangular Nanoplates
Tulio Rocha 2 1 , Herbert Winnischofer 3 , Eduard Westphal 4 , Socrates Dantas 2 , Douglas Galvao 2 , Daniela Zanchet 1
2 , Universidade Estadual de Campinas, Campinas, São Paulo, Brazil, 1 , Laboratório Nacional de Luz Síncrotron, Campinas, São paulo, Brazil, 3 , Universidade Federal do Paraná, Curitiba, Paraná, Brazil, 4 , Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brazil
Show Abstract5:45 PM - DD15.5
Kinetically Controlled Synthesis of Pd Nanoplates and Nanorods: Two Anisotropic Shapes with Tunable Plasmonic Properties
Yujie Xiong 1 , Younan Xia 1
1 Chemistry, University of Washington, Seattle, Washington, United States
Show AbstractThe surface plasmon resonance (SPR) peaks of Pd nanoparticles (usually below 10 nm in size) are typical located in the UV region, which makes them more difficult to probe due to strong absorption of glass and most solvent at these wavelengths. In this presentation, I will demonstrate that the SPR peaks of Pd nanostructures can be tuned into the visible region by growing them into anisotropic shapes such as nanoplates and nanorods. As shown by Wulff construction, the thermodynamically favored shape of Pd is cubooctahedron which can be produced via a fast reduction of Pd precursor. We have recently developed three different approaches to control the reduction/growth kinetics and thus obtain Pd nanoplates and nanorods: i) to slow down the reduction by coupling with oxidative etching, ii) by using a mild reducing agent for the synthesis of triangular and hexagonal nanoplates; and iii) by introducing some anionic species that selectively adsorb onto certain facets and change relative surface energies of different facets for the synthesis of nanorods. By controlling the ratio of edge length to thickness of nanoplates or the aspect ratio of nanorods, their SPR peaks could be tuned to the visible and near-IR region. The synthetic strategies have also been extended to Ag and Au. It is expected that the present work will enable us to manipulate the SPR peaks of metal nanostructures and open the door to new applications in the visible and near infrared regions.
DD16: Poster Session: Synthesis and Characterization II
Session Chairs
Sanat Kumar
Masaru Kuno
Xiao-Min Lin
Ruth Pachter
Moonsub Shim
Friday AM, April 13, 2007
Salon Level (Marriott)
9:00 PM - DD16.10
Size and Shape Control of Nickel Nanoparticles.
Yi Yang 1 , Yang Xiang 1 , Chandra Khadilkar 1 , Aziz Shaikh 1
1 , Ferro Corporation, Independence, Ohio, United States
Show AbstractNanocrystalline nickel powders, spherical or spiky shapes with the size of 10 to 100 nm, were prepared through chemical reduction of their corresponding metal salts under suitable conditions. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), BET method and thermal gravimetry (TG) were used to characterize the nickel nanoparticles prepared at various conditions. The carbon and oxygen contents and tab densities of the nano-nickel powders were also measured.
9:00 PM - DD16.11
Scalable Synthesis of Silver Nanocubes in Less than a Minute under Microwave irradiation
Subrata Kundu 1 , Ravi Saraf 1
1 University of Nebraska, Lincoln, Department of Chemical & Biomedical Engineering, Lincoln, Nebraska, United States
Show Abstract9:00 PM - DD16.12
Crystallografy of the Catalytic System of Small Metallic Gold Particles Supported on Coexisting Titania Phases.
Amado Garcia-Ruiz 1
1 Physics, UPIICSA-IPN, México, D. F. Mexico
Show AbstractA. Morales and X. Bokhimi. Institute of Physics. The National University of Mexico (UNAM), A. P. 20-364, 01000 México, D. F., Mexico.A. García-Ruiz. UPIICSA-COFAA. The National Polytechnic Institute(IPN). Té 950, Iztacalco, 08400 México, D. F. Mexico.R. Zanella. Center of Applied Sciences and Technological Development (CCADET). The National University of Mexico (UNAM), A. P. 70-186, 04510 México, D. F., Mexico.Synthesis of titania to get a high concentration of brookite coexisting with rutile and anatase were tried out by two ways. In the first way, an aqueous solution of titanium butoxide with hydrochloric acid was treated hydrothermally at the synthesis temperature, between 90 C and 200 C, with several molar ratios H2O/HCl and a fix ratio HCl/TiBu. In the second way, coexisting titania polymorphs were prepared by sol gel, starting from an acidic solution, nitric acid for obtaining anatase or rutile as dominat phase or hydrochloric for obtaining brookite as predominant, and aggregating titanium butoxide for get, annealing at 90 C, a precipitate of titania. The specimens obtained in this second way were utilized as support to preparate catalysts Au/TiO2 and Au/Ce-TiO2 with 5 wt% Au and 12 % cerium concentration, also by sol gel. Samples were characterized by X-ray diffraction, which allowed to refine the crystalline phases of titania using the Rietveld method for obtaining the concentration and the lattice parametersof the the three polymorphs , as well as the size and the morphology of the crystallites. For the samples obtained in the first method, these parameters were obtained as function of the ratio H2O/HCl and also of the synthesis temperature. The results showed that the synthesis with the ratio H2O/HCl equal to 20 and the temperature of 120 C is the ideal one in order to get the maximum of the brookite concentration. The morphology and the average size of the crystals obtained by means of the refinements are in good accord with the corresponding observed values in the micrographs generated by HRTEM.For the catalysts, with titania support obtained by the second way, the Rietveld refinements provided also crystallograpics features of the metallic gold phase. The gold crystallite size and morphology depended on the titania polymorph used as support: when it was anatase the gold crystallite had their smallest dimension perpendicular to their (111) planes, while for brookite and rutile it was perpendicular to the (200) planes. The large amount of structural defects in the support worked as particle pinning centers of the gold crystallites, hindering production of larger crystallites. The refinement allowed to extract the contribution of the metallic gold to the X-ray diffraction pattern of the catalyst. When anatase and brookite were doped with cerium their crystallite size decreased and their structural defects increased . For anatase, all the cerium was incorporated favoring the formation of smaller gold crystallite.
9:00 PM - DD16.13
One-Step Microwave Preparation of Well-defined Polymeric Nanoparticles
Zesheng An 1 3 , Wei Tang 1 , Craig Hawker 1 2 3 , Galen Stucky 1 2 3
1 Chemistry, UCSB, Santa Barbara, California, United States, 3 Mitsubishi Center for Advanced Materials, UCSB, Santa Barbara, California, United States, 2 Materials Research Laboratory, UCSB, Santa Barbara, California, United States
Show Abstract9:00 PM - DD16.15
Enhanced Near UV Emission from Sunflower-like Nanostructures Composed of SiOx Nanorods with Spotty SnO2 Nanoparticles
Kum M. Li 1 , Yi-Jing Li 1 , Ming-Yen Lu 1 , Jr-Hau He 1 , Lih-J. Chen 1
1 Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan, Republic of China, Hsinchu Taiwan
Show AbstractSunflower-like nanostructures composed of SiOX nanorods with spotty SnO2 nanoparticles have been synthesized in large quantities via a thermal evaporation and condensation method. The size of absorbed SnO2 nanoparticles can be controlled by adjusting the flow of O2. The peculiar nanostructures exhibit intense near UV emission in cathodoluminescence measurement. By controlling the size of the SnO2 nanoparticles on the SiOx nanorods, the intensity of near UV emission of 398 nm can be enhanced. The nanostructures are potentially applicable as near UV emitters.
9:00 PM - DD16.16
III-VI Compound Semiconductor Indium Selenide (In2Se3) Nanowires: Synthesis and Characterization
Xuhui Sun 1 , Garrick Ng 1 , Thuc Dinh Nguyen 1 , Bin Yu 1
1 Ames Center for Advanced Aerospace Materials and Devices, NASA Ames Research Center, Moffett Field, California, United States
Show Abstract9:00 PM - DD16.17
Syntheses, Structures and Magnetic Properties of 1D Metallomacrocyclic Complexes.
Mi Hyang Jeong 1 , Ju Chang Kim 1 , Young Soo Kang 1
1 Chemistry, Pukyong National Univ., Busan Korea (the Republic of)
Show Abstract9:00 PM - DD16.19
Characterization of Carbon Nanotubes Grown by a Non-Metal Catalyst Method
Shanee Houston 1 , Gail Brown 1 , Bill Mitchel 1 , John Boeckl 1
1 , Wright Patterson Air Force Base/Air Force Research Laboratory, Wright-Patterson , Ohio, United States
Show AbstractCarbon nanotubes (CNTs) have been formed on both the Si and C-face of both 4H and 6H SiC substrates, by sublimation of Si from SiC at elevated temperatures. There is no purification process needed to remove metal from the CNTs after growth, because a metal is not used in the growth process. After subjecting the SiC sample to temperatures ranging from 1400°- 1700°C in a vacuum furnace (10-2- 10-5 torr), oxidation caused SiC to decompose and Si sublimed from the substrate. The remaining carbon atoms left on the surface are the nucleation site for the CNTs; the air in the chamber catalyzes the formation of carbon nanotubes. Characterization of the CNTs grown using this method was performed using: scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and Raman spectroscopy. The SEM showed that CNTs grow at a faster rate on the C-face than on the Si-face of the substrate; and the use of the TEM concluded that the pressure in the vacuum furnace has an affect on the CNT growth. All characterization techniques showed a growth of both multi-walled and single-walled CNTs.
9:00 PM - DD16.2
Solvothermal Synthesis and Self-assembly of One-Dimensional FePt and Fe3O4 Nanoparticles
Min Chen 1 2 , Hongyou Fan 1
1 Advanced Materials Lab, Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 Center for Micro-Engineered Materials, University of New Mexico, Albuquerque, New Mexico, United States
Show AbstractOne-dimensional magnetic nanoparticles are promising for advanced applications in photonic, electronic, and data storage devices because of their anisotropic structures in nanoscale domain. We present here the solvothermal synthesis of one-dimensional FePt nanoparticles from simultaneous decomposition of Fe(CO)5 and reduction of Pt(acac)2 in an organic solvent. Low heating rate favored the formation of smooth nanorods. By simply increasing the heating time, the FePt nanowires with a length up to a few hundred nanometers were formed. Similarity, decomposition of Fe(CO)5 produced Fe3O4 nanorods and nanowires. As prepared, one-dimensional Fe3O4 nanoparticles were amorphous. Upon annealing under protection of nitrogen gas at a temperature of 400 oC, the crystalline Fe3O4 nanorods were formed. The effect of annealing temperature on the crystal structures and magnetic properties of one-dimensional FePt and Fe3O4 nanoparticles will be discussed.
9:00 PM - DD16.20
The Significance of Catalyst to Hydrocarbon Ratio in the CVD Synthesis of Multiwalled Carbon Nanotubes
Gregg McKee 1 , Kenneth Vecchio 1
1 Materials Science and Engineering Program, University of California, San Diego, La Jolla, California, United States
Show Abstract The vapor-phase catalytic chemical vapor deposition (cCVD) synthesis of multi-walled carbon nanotubes (MWNT’s) shares many similarities with the synthesis of vapor grown carbon fibers (VGCF). It has been shown that the catalyst to hydrocarbon feed ratio determines the fiber diameter and aspect ratio of VGCF. As a result of the similar growth processes, it might be expected that the same would apply to the cCVD growth of MWNT, potentially enabling a more direct dimensional control over what is often an empirical synthesis technique. It is also probable that an ideal catalyst/carbon ratio exists which would allow the synthesis of nanotubes of an optimal structure resulting from minimal defect density and maximum chemical stability. This work will examine the significance of the catalyst to carbon ratio in these respects and will establish an optimum ratio allowing for the creation of low-defect nanotubes with high chemical stability. Temperature Programmed Oxidation (TPO) analyses on nanotubes synthesized using varying catalyst/carbon ratios will be described and their results compared with Raman spectra obtained from each sample. It is expected that these methods will indicate an ideal ratio for the synthesis methods used. The results of a TEM survey of the nanotube population will be described which indicate the dimensional dependence of the nanotubes upon the catalyst/carbon ratio.
9:00 PM - DD16.21
One step synthesis and densification of Nanocrystalline NbSi2-Si3N4 Composite by High-Frequency Induction heated Combustion
In-Jin Shon 1 , Hyun-Kuk Park 2 , In-Kyoon Jeong 3 , In-Yong Ko 4 , Jin-Kook Yoon 5
1 Advanced Materials, Chonbuk University, JeonJu, Jeonbuk, Korea (the Republic of), 2 Advanced Materials, Chonbuk University, Jeonju, Jeonbuk, Korea (the Republic of), 3 Advanced Materials, Chonbuk University, JeonJu, Jeonbuk, Korea (the Republic of), 4 Advanced Materials, Chonbuk University, JeonJu, Jeonbuk, Korea (the Republic of), 5 Metal Processing Research Center, Korea Institute of Science and Technology, Seoul, Seoul, Korea (the Republic of)
Show AbstractDense nanostructured 4NbSi2-Si3N4 composite was synthesized by high-frequency induction-heated combustion synthesis (HFIHCS) method within 1 minute in one step from mechanically activated powders of NbN and Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of an induced current and mechanical pressure. Highly dense 4NbSi2-Si3N4 composite with relative density of up to 98% was produced under simultaneous application of a 60 MPa pressure and the induced current. The average grain size and mechanical properties (hardness and fracture toughness) of the composite were investigated. The average grain sizes of NbSi2 and Si3N4 phases in the composite were about 90 and 25nm, respectively. The average hardness and fracture toughness values obtained were 680 kg/mm2 and 3.1MPa m1/2, respectively. The lack of reported data on NbSi2-Si3N4 makes difficult to make direct comparisons, but based on reported data on NbSi2 coating, an approximate comparison shows that the present results exhibit a lower hardness and higher toughness.
9:00 PM - DD16.22
Ultrafast Pulsed Laser Ablation as a Method for Synthesis of Nanocrystals
Bing Liu 1 , Zhendong Hu 1 , Yanbin Chen 2 , Xiaoqing Pan 2 , Yong Che 1
1 , IMRA America Inc., Ann Arbor, Michigan, United States, 2 Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show Abstract9:00 PM - DD16.23
Paramagnetic Polynuclear Transition Metal Clusters with Redox Active Ligands Derived from TTFs.
Lahcene Ouahab 1 , Kostyantyn Gavrylenko 1 , Yann Le Gal 1 , Olvier Cador 1 , Stephane Golhen 1
1 Chemistry, UMR CNRS 6226 University of Rennes 1, Rennes France
Show Abstract9:00 PM - DD16.25
The Effect of Ge Layers on the Kinetics of NiSi2 Islands Formation
Ling-Hui Wu 1 , Cho-Jen Tsai 1
1 Material Science and Engineering, National Tsing Hua University, Hsinchu Taiwan
Show AbstractThe effects of a Ge layer on the kinetics of NiSi2 islands formation in Ge/Ni/Si (100) structure were investigated. It was observed that the nucleation and growth of NiSi2 islands were is impeded with increasing thickness of the Ge layers. A Si (100) wafer was cleaned using standard RCA process and dipped into a diluted HF solution. The substrate was further sputtered cleaned using an Argon ion beam for 1 minute before film deposition. One monolayer (ML) of Ni and an amorphous Ge cap layer (5, 10, 15, 20ML) were deposited on Si substrate. The samples were then ex-situ annealed at 400-800 oC. The formation temperature of NiSi2 phase is 500 oC and 580 oC for the Ge layer of 5 ML and 20ML, respectively. The samples were ex-situ characterized using field emission scanning electron microscopy and transmission electron microscopy to study the microstructure and to identify the formation temperature of the NiSi2 phase. The reaction process started with the dissolution of the Ni atoms into the amorphous Ge layer. Next, solid phase epitaxy of the Ge layer followed. The Ni atoms were expelled from the crystallized region and redistributed in the amorphous region. Until the concentration of Ni in the amorphous Ge layer exceeded the solubility limit, the Ni atoms diffused through the crystallized Ge layer and reacted with the Si to form NiSi2 phase. The kinetics of the NiSi2 phase formation is, thus, governed by the rate of solid phase epitaxy. The rate of solid phase epitaxy is impurity dependent. For the same amount of Ni to redistribute in the amorphous Ge cap layer, the thinner Ge layer has higher Ni concentration, which increases the rate of solid phase epitaxy. Besides, in this experiment, the interface between the amorphous layer and the Si substrate is probably mixed due to the ion beam bombardment. Therefore, compared with the pure Ge layers, the solid phase epitaxy in this experiment occurs at the higher temperature. If the amorphous Ge layer has higher Ni concentration, the segregation of Ni in amorphous Ge can reach its solubility limit at smaller thickness of the crystallized Ge. The nucleation of the NiSi2 phase would occur earlier for an amorphous Ge with higher Ni concentration than that with lower Ni concentration. For thicker Ge cap layer, because the concentration of Ni in the amorphous Ge layers is lower, the nucleation of the NiSi2 island would occur at a higher temperature. Hence, the appearance of the NiSi2 phase is kinetically retarded. This experiment demonstrates that the nucleation and growth of NiSi2 islands are controlled by using a Ge layer with different concentration of Ni atoms. It is a new method to form silicides, which is different from the oxide mediated epitaxy or the nitride mediated epitaxy.
9:00 PM - DD16.26
New Palladium Nanomaterials for Catalysis : Mechanisms Controlling Formation and Evolution of Nanostructures in a Seed-mediated Synthesis.
Laure Bisson 1 2 , Cedric Boissiere 1 , Clement Sanchez 1 , Cecile Thomazeau 2 , Denis Uzio 2
1 Catalyse et Séparation, Institut Français du pétrole, Vernaison France, 2 , Laboratoire Chimie de la Matière Condensée, UPMC, Paris France
Show Abstract9:00 PM - DD16.27
Low Density Aerogels and Foams: Self-assembled Macroscopic Structures Controlled on the Nanometer Scale.
John Karnes 1 , Streit John 1 , Nicole Petta 1
1 , Schafer Corporation, Livermore, California, United States
Show Abstract9:00 PM - DD16.28
Formation of Zinc Layered Double Hydroxide in Colloidal ZnO Nanoparticles
Dazhi Sun 1 , Minhao Wong 2 , Nobuo Miyatake 3 , Hung-Jue Sue 1
1 Mechanical Engineering Department, Texas A&M University, College Station, Texas, United States, 2 , Kaneka Corporation, Takasago, Hyogo, Japan, 3 , Kaneka Texas Corporation, Pasadena, Texas, United States
Show AbstractColloidal ZnO nanoparticles with sizes ranging from 2-5 nm have been synthesized by adding zinc acetate methanol solution into KOH/methanol solution. Zinc layered double hydroxide (Zn-LDH) was found to exist in the precipitates from the ZnO sol of early stage. The formation of Zn-LDH in ZnO colloids was investigated. It was found that Zn-LDH formation was greatly affected by reactant concentrations, reacting time, and temperature. The growth of ZnO nanoparticles and the structural transformation of acetate zinc hydroxide to spherical ZnO nanocrystals by solvent evaporation were monitored via X-ray diffraction and transmission electron microscopy. Our results suggest that solvent evaporation is an effective approach to remove layered double hydroxide from the ZnO nanocrystals.
9:00 PM - DD16.29
IB Element Doped p-ZnO Nanorods and their Optical Properties.
Ji-Won Choi 1 , Jung-Wook Lee 1 , Heung-Chun Park 1 , Hyunmi Hwang 2 , Jaeyong Lee 2 , Won-Kook Choi 1
1 Thin Film Materials Research Center, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 2 Department of Physics, Yonsei University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - DD16.3
Single-crystalline Si Nanotip Array Fabricated Using Si-based Porous Anodic Alumina Template.
GaoShan Huang 1 , XingLong Wu 1 , Paul K. Chu 2
1 National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 China, 2 Department of Physics and Materials Science, City University of Hong Kong, Kowloon Hong Kong
Show Abstract9:00 PM - DD16.30
In-Situ Core/Shell Structured FePt/ZnFe2O4 Magnetic Nanoparticles
Ki-Eun Kim 1 , Yun-Mo Sung 1
1 Materials Sci. & Eng., Korea University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - DD16.31
Structural Control of Carbon Nanowalls and Their Properties as a Transparent Conducting Material
Suguru Noda 1 , Rie Nishimoto 1 , Hisashi Sugime 1 , Susumu Inasawa 1 , Yoshiko Tsuji 1 , Yukio Yamaguchi 1
1 Department of Chemical System Engineering, The University of Tokyo, Tokyo Japan
Show AbstractCarbon forms a variety of nanostructures with unique properties. Since the recent discovery of carbon nanowalls (CNWs) or carbon nanosheets [1], their synthesis methods and their applications to field emitters have been studied by several groups. CNWs can be grown by plasma enhanced chemical vapor deposition (PE-CVD) without catalysts, but the growth conditions and the resulting structures vary from group to group. In this work, we investigated the effect of growth conditions on CNW structures, tried to control the structure by controlling the nucleation and growth steps, and examined their properties as a transparent conducting material.CNWs were grown on quartz glass substrates by a cold-wall PE-CVD reactor from C2H4 at around 800 K with a r.f. power of 150 W. Its growth nature depended largely on the C2H4 pressure; deposition hardly occurred at a pressure lower than 0.13 kPa, CNWs grew after a incubation time around 10 min at 0.13-0.2 kPa, and they grew without any incubation at 0.27 kPa and above. CNWs grown at 0.27 kPa and above for 5 min typically had a transparency around 80 % and a sheet resistance of 5-10 kΩ/sq. The CNW structures were observed by a field emission scanning electron microscope, and they proved to have a networked structure with a few nanometer wall thickness and a several tens nanometer spacing. When we consider their application to a transparent conducting material, enlarging these dimensions is important because the number of grain boundaries, and thus the electrical resistance, among the walls can be reduced. For this purpose, we examined a three-step-growth process, i.e. seeding, etching and regrowth, only by changing the gas pressures. By switching the gas from C2H4 to H2, CNWs can be easily etched. CNWs with a 80 % transparency were mostly etched in 1 min by H2 plasma at 0.8 kPa, resulting into small CNWs isolated each other. Then we switched the gas from H2 to C2H4/H2 mixture to mildly grow these "seeds" without additional nucleation of CNWs. The spacing among CNWs increased by a factor of 2-3, but the sheet resistance did not change so much. To improve the electrical conducting property, control of other structures such as crystalline defects and hydrogen inclusion will be important as well.[1] Y. Wu, et al., Adv. Mater. 14, 64 (2002).
9:00 PM - DD16.32
Expansion and Characterization of Mesostructures in Aerosol-generated Particles.
Malin Sorensen 1 , Juan Valle-Delgado 2 , Robert Corkery 1 , Peter Alberius 1
1 , Institute for Surface Chemistry, Stockholm Sweden, 2 Department of Chemistry, Surface Chemistry, Royal Institute of Technology, Stockholm Sweden
Show Abstract9:00 PM - DD16.33
Vertically Aligned Growth and Characterization of III-Nitride Nanowires and Heterostructure Nanowires.
George Wang 1 , A. Alec Talin 1 , J. Randall Creighton 1 , Donald Werder 2 , Elaine Lai 1 , Richard Anderson 1 , Ilke Arslan 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractNanowires based on the direct bandgap semiconductor Group III nitride (AlGaInN) materials system have attracted attention as potential building blocks in optoelectronics, sensing, and electronics. We have employed a VLS-based metal-organic chemical vapor deposition process to synthesize highly aligned arrays of single-crystalline GaN nanowires on 2-inch diameter sapphire and GaN substrates without the use of a patterned template. SEM and TEM analysis indicate that the nanowires share a common [11-20] growth orientation and have aligned facets, with a majority of the nanowires lacking a catalyst cluster at the tip. We have found a strong correlation between growth temperature and the optical and electrical properties of the nanowires, which we propose is due to carbon incorporation from the metal-organic source. The effects of substrate and catalyst preparation on the ordered growth will be also discussed. Building on our growth technique, aligned radial heterostructure nanowire arrays consisting of a GaN cores and various III-nitride shell materials, including AlGaN and AlN, were synthesized and characterized. Our results show that the presence of the AlGaN and AlN shell layers in the core-shell nanowires have significant effects on the nanowire transport properties, when compared to GaN nanowires. Additionally, characterization of the heterostructure nanowires via 3D STEM tomography and spatially resolved photoluminescence will be presented. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.
9:00 PM - DD16.34
Synthesis of 1D Nanorods of Phthalocyanine Using Porous Alumina as a Template and Magnetic Control of the Molecular Orientation During Solidification.
Seiichi Takami 1 , Yasuhiro Shirai 1 , Yutaka Wakayama 1 , Toyohiro Chikyow 1
1 Advanced Electronic Materials Center, National Institute for Materials Science, Tsukuba, Ibaraki, Japan
Show AbstractConjugated molecules are expected as a key component to establish organic electronics. Many researchers study the controlled growth of well-ordered solids of organic molecules to realize better electrical properties. In addition to the vacuum deposition of thin films, we believe that the fabrication of nanorods with controlled molecular orientation should be developed as a building block for miniaturized devices. Antiferromagnetic organic molecules are aligned under applied magnetic field. Base on this property, we propose the synthesis of 1D nanorods of phthalocyanine, whose molecular orientation in the nanorods was controlled by an applied magnetic field during solidification. In this presentation, we show the synthesis of the 1D nanorods of phthalocyanine molecules using anodized porous alumina as a template and the control of molecular orientation by applying 5T magnetic field during solidification. We also discuss the effect of pore wall surface of the porous alumina on the moleuclar orientation.
9:00 PM - DD16.35
CoP-based Material as a Catalyst for Carbon Nanotube Via Formation at 400C
Guo-Dung Chen 1 , Tri-Rung Yew 1 , Chung-Min Tsai 1
1 Materials Science and Engineering, National Tsing-Hua University, Hsinchu, Taiwan Taiwan
Show AbstractThis paper presents the investigation of electroless CoP-based material as a catalyst for carbon nanotube (CNT) via formation at 400C. Electroless CoP-based material was not only used as a barrier cap for Cu wiring, but also as a catalyst for CNT growth. To increase CNT density for low resistance via formation, it requires dense and small catalysts for CNT synthesis. The electroless plating process of CoP-based materials was optimized to provide a proper surface morphology and Co distribution for dense CNT synthesis. The CNTs were synthesized by chemical vapor deposition. The surface morphology of CoP-based materials was inspected by atomic force microscopy (AFM). The Raman spectra were used to characterize the CNTs. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were also employed to characterize the CoP-based catalyst and CNTs. Besides, a Cu/low-k dual damascene test structure was used for CNT synthesis to measure via resistance and investigates its feasibility for future CMOS interconnect via application.
9:00 PM - DD16.36
Study on the Growth of ZnO Micro and Nano-structures at Low Temperature and Atmospheric Pressure.
Monica Morales 1 , B. Claflin 1 2 , G. Farlow 1 , D. Look 1 2
1 Physics, Wright State University, Dayton, Ohio, United States, 2 Semiconductor Research Center, Wright State University, Dayton, Ohio, United States
Show Abstract9:00 PM - DD16.37
Synthesis of Zinc-Blende CdSe Core Based Type I (Core)Shell and (Core) Double Shell Quantum Dots and Their Optical Properties.
Sung Jun Lim 1 , Yongwook Kim 1 , Seung Koo Shin 1
1 Chemistry, Pohang University of Science and Technology, Pohang, Kyungbuk, Korea (the Republic of)
Show AbstractHighly luminescent zinc-blende CdSe quantum dots (QDs) of various sizes were synthesized by adopting the injection-free method(1) with some modifications. CdSe QDs were overcoated with wider band-gap semiconductor shells such as CdS, ZnS, and ZnSe. The shell thickness was controlled while suppressing the self-nucleation of the shell materials during overcoating. All three inorganic shells improve the photoluminescence quantum yield (QY), but induce the red-shift of both the absorption and emission maxima. The organic passivation with thiols reduces QY, however the amount of reduction varies with shell materials. All zinc-blende (core)shell QDs were overcoated with additional ZnS layers and made water-soluble and their optical properties were studied.(1) Y.A.Yang, H.Wu, K.R.Williams, and Y.C.Cao, Angew.Chem.Int.Ed. 44 (2005) p. 6712
9:00 PM - DD16.38
Novel Aapproach to the Synthesis of Mn-doped CdSe Nanocrystals.
Woo-Chul Kwak 1 , Yun-Mo Sung 1
1 Materials Sci. & Eng., Korea University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - DD16.39
Water-soluble TOPO-Free All Zinc-Blende Structure (Core)Shell Quantum Dots: Synthesis, Characterization and Fluorescence Tagging on Biomolecules.
Yongwook Kim 1 , Sung Jun Lim 1 , Min-Soo Suh 1 , Hye Jin Ham 1 , Hye-Joo Yoon 1 , Bonghwan Chon 1 , Taiha Joo 1 , Seung Koo Shin 1
1 Dept. of chemistry, POSTECH, Pohang Korea (the Republic of)
Show AbstractAll zinc-blende structure (CdSe)ZnS (core)shell quantum dots (QDs) were synthesized in octadecene in the absence of tryoctylphosphine oxide (TOPO). QDs were made water-soluble by ligand exchange with functionalized thiols, such as 3-mercaptopropionic acid (MPA), 3-mercapto-1-propanol (MPO) and aminoethanthiol (AET). In TOPO-free environment, the QDs surface was covered with thiol ligands only. The hydrodynamic radii of water-soluble QDs were measured by dynamic light scattering (DLS). In all three cases, no aggregates were formed at room temperature. The absorption and photoluminescence (PL) spectra were taken and the PL lifetimes were measured by femto-second time-correlated single photon counting (TCSPC). Each water-soluble functional group was successfully conjugated with biomolecules (protein, DNA) and small molecules by applying various bioconjugate chemistry. QD-biomolecule conjugates were characterized by gel electrophoresis and purified by column chromatography. Both nonspecific binding and biocompatibility were studied in vitro.
9:00 PM - DD16.4
Sol Gel Synthesis of Ge Nanophases in Silica Matrix.
Norberto Chiodini 1 , Sergio Brovelli 1 , Alessandro Lauria 1 , Alberto Paleari 1
1 Dip. di Scienza dei Materiali, Università di Milano-Bicocca, Milano Italy
Show Abstract9:00 PM - DD16.40
Roles of Pre-Laser-Ablation of Mn in Growth of ZnO Nanorods by Chemical Vapor Deposition
Takashi Hirate 1 , Hiroshi Miyashita 1 , Tomomasa Satoh 1
1 Electronics and Informatics Frontiers, Kanagawa University, Yokohama Japan
Show Abstract We studied on a role of laser ablation in fabrication of ZnO nanorods by chemical vapor deposition (CVD) combined with laser ablation of Mn. Metal Zn vapor and O2 gas are used as precursors to synthesize ZnO and N2 is used as carrier gas. The Mn pellet is placed near a Si(111) substrate in a deposition chamber and ablated by a pulsed Nd:YAG laser beam (10 shots/sec, 0.04 J/shot). In this study, the laser ablation of Mn is performed in advance of growth of ZnO nanorods by CVD (pre-laser-ablation), i.e., after the laser ablation of Mn for 1 sec to 1 min, O2 is introduced into a deposition chamber and ZnO nanorods are grown only by CVD for 3 min. The growth conditions are as follows. The growth temperature is 550 degree C. The growth pressure is 27 Pa. O2 flow rate is 1.5 SCCM. We mainly studied on dependency of morphology of ZnO nanorods on the pre-laser-ablation time, and it was found that the pre-laser-ablation is an effective method to analyze a growth mechanism of nanorods. When no pre-laser-ablation is performed, randomly oriented nanorods with 20 nm averaged diameter and 250 nm averaged length are grown with very low number density of 4 per squared microns. The dispersions in diameter, length and growth direction are very large. When the pre-laser-ablation is performed for only 1 sec, however, ZnO nanorods with 64 nm diameter and 500 nm length are uniformly grown, and the number density is about 50 per squared micron. The directions of nanorods, however, are not so uniform. When the pre-laser-ablation is performed for 5 sec, well aligned ZnO nanorods with 40 nm diameter and 650 nm length are uniformly grown, and the number density is about 120 per squared micron. Comparing with the results of 1 sec of pre-laser-ablation, thinner and longer nanorods are grown with well aligned direction and the number density is over the double. A ZnO nucleation layer that is formed continuously between ZnO nanorods and Si substrate is observed, although it is not formed in the case of 1 sec pre-laser-ablation. When the pre-laser-ablation is performed for 30 sec, well aligned ZnO nanorods with 75 nm diameter and 800 nm length are uniformly grown, and the number density is about 70 per squared micron. The thickness of nucleation layer is 170 nm. When the pre-laser-ablation is performed for 1 min, the morphology of nanorods and the thickness of nucleation layer are almost same as those when the pre-laser-ablation time is 30 sec. We consider from the experimental results as followings. Any species of Mn that is laser-ablated and reached on the substrate play a role of ‘nucleus’ for growth of ZnO nanorods. The direction of nanorod grown from this nucleus may be random and the collisions between initial nanorods are occurred. This region may be a nucleation layer. As the results of collisions the growth of nanorods with oblique growth direction is stopped and only the nanorods with vertical growth direction continue to grow.
9:00 PM - DD16.41
PLA-CVD Growth of Vertically Aligned Carbon Nanotube Arrays.
Zuqin Liu 1 , Alex Puretzky 1 2 , David Styers-Barnett 1 , Chris Rouleau 1 2 , Gyula Eres 1 2 , David Geohegan 1 2
1 Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 2Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show Abstract9:00 PM - DD16.42
Fabrication Of Metallic Chromium Nano- And Micro-Structures By Gas Phase Reaction.
Luis Valentin 1 , Luis Fonseca 1 , Oscar Resto 1
1 Physics, University of Puerto Rico, San Juan, Puerto Rico, United States
Show Abstract9:00 PM - DD16.43
A Study of the Effects of Electrolyte on the Formation of Porous Alumina
Loosineh Avakians 1 , Lynn Trahey 1 , Angelica Stacy 1
1 Chemistry , University of Berkeley California, Berkeley, California, United States
Show AbstractPorous anodic alumina (PAA) templates are commonly used insynthesizing nanowires of materials that are potentially useful as quantum wires. These templates are made by the anodization of aluminum in acidic solutions. The goal of this project is to study the effects of varying the electrolyte choice and concentration on the formation of PAA templates. Although effects of electrolytes such as oxalic, sulfuric and phosphoric acids are well known to researchers, it is desired to investigate the templates in new electrolyte environments that may result in enhancements of pore wall functionalities and dimensions. Therefore, new electrolytes with differing conjugate bases have been studied to determine their potential to serve as pore forming electrolytes. Scanning electron microscopy has been used to study the morphologies of PAA films produced under a variety of controlled conditions.
9:00 PM - DD16.44
Understanding the Growth Mechanism of Single-Walled Carbon Nanotubes Using ``Spin-on-Catalyst" Method.
Seung Min Kim 1 , Mark Pender 2 , Tyson Back 3 , Allison Jacques 2 , Benji Maruyama 2 , Eric Stach 1
1 School of Materials Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana, United States, 2 Materials & Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, United States, 3 Materials Engineering, University of Dayton, Dayton, Ohio, United States
Show Abstract9:00 PM - DD16.45
Low Temperature Synthesis of Thick Diamond Films based on Low Power CVD Techniques.
Xinpeng Wang 1
1 Physics, University of Puerto Rico, Rio Piedras Campus, San Juan, Puerto Rico, United States
Show Abstract9:00 PM - DD16.48
Controlled Growth of Heterophase TiO2 Nanowires via CVD
Jung-Chul Lee 1 , Yun-Mo Sung 1
1 Materials Sci. & Eng., Korea University, Seoul Korea (the Republic of)
Show AbstractTiO2 is a wide-band gap semiconductor showing wide range of applications, including photocatalysts, gas and humidity sensors, and photochemical solar cells. The photocatalytic efficiency of TiO2 is greatly influenced not only by its crystalline structure, such as brookite, anatase, and rutile, but also by its morphological features. With the development of nanotechnology, nanostructured TiO2 is finding wider applications. Several research results reveal that one-dimensional TiO2 nanostructures can be synthesized by a template sol–gel method, a relatively new chemical procedure. With this approach TiO2 nanotubes in polycrystalline anatase were successfully synthesized. However, this wet-chemistry based template method not only arrives at the polycrystalline structures, but also causes contamination problems, which seriously deteriorate physical and chemical properties of TiO2. Furthermore, so far no one has reported the synthesis and characterization of TiO2 NW’s having mixed crystalline phases of anatase and rutile via chemical vapor deposition (CVD).Heterophase TiO2 NW’s were successfully grown all over quartz and sapphire substrates by CVD using Ti powder and liquid TiCl4 at a substrate temperature of 700 °C. X-ray diffraction (XRD) was performed to analyze crystallinity of the TiO2 NW’s. The morphological features of the TiO2 NW’s were characterized by field emission scanning electron microscopy (FESEM). High-resolution transmission electron microscopy (HRTEM) and energy dispersive x-ray spectroscopy (EDS) analysis performed on the individual NW’s indicates that the nanowires are well-defined TiO2 with mixed phases of anatase and rutile. Photocatalytic efficiency was investigated for the TiO2 NW’s measuring the decomposition rates of methylene blue solution, and it was discussed based upon variation in the phase composition and morphological features of the TiO2 NW’s.
9:00 PM - DD16.5
Surface Modification of Si Nanocones Fabricated by Porous Anodic Aluminum Oxide Templation.
Te-Ming Chen 1 , Jui-Yi Hung 1 , Fu-Ming Pan 1 , Shich-Chuan Wu 2 , L. Chang 1
1 Dept. Mat. Sci. Eng., National Chiao Tung University, Hsinchu Taiwan, 2 , National Nano Device Laboratories, Hsinchu Taiwan
Show Abstract9:00 PM - DD16.6
Post-annealing Induced Formation of ZnO Nanowires on the ZnO Films in the N2O Ambient.
Ping-Yuan Lin 1 , Wei-Tsai Liao 1 , Kuo-Yi Yan 1 , Chia-Chi Chang 1 , Jyh-Rong Gong 1 , Jian-Hao Lin 2 , Tai-Yuan Lin 2
1 Department of Physics, National Chung Hsing University, Taichung City Taiwan, 2 Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung Taiwan
Show Abstract9:00 PM - DD16.7
Controlled Synthesis of Highly Branched TiO2 Nanowire
Heawon Chung 1 2 , Young-wook Jun 1 , Mi-yun Kim 1 , Jinwoo Cheon 1 2
1 Department of Chemistry, Yonsei University , Seoul Korea (the Republic of), 2 Nanomedical National Core Research Center, Yonsei University , Seoul Korea (the Republic of)
Show AbstractAnisotropic shape control of nanoparticles is of considerable importance due to their novel characteristics. Particularily in titanium dioxide, there are several notable synthetic methods among previous findings, but their shape is not methodically regulated nor their crystalline phase can be systematically varied. Here we demonstrate the synthesis of titanium dioxide of branched multipod nanowire structures via simple nonhydrolytic colloidal growth process. By controlling the introduction point of oxygen generating molecular precursor, two different crystalline phases rutile and anatase simultaneously form in one-pot; in consequence material shapes can be tuned from nanorod to branched nanowire structure. The length of nanowires can be varied from 20 nm to 200 nm and branched structures are typically bipods and tripods. We’ll discuss the mechanism of multi-branched TiO2 growth in detail along with photochemical properties associated with the anisotropy.
9:00 PM - DD16.8
Biosynthesis of CdS and ZnS nanoparticles by two different Fungus
Luis Reyes 1 , Idalia Gomez 1 , Teresa Garza 1 , Patricia Zambrano 2
1 Facultad de Ciencias Químicas, UANL, San Nicolás de los Garza, Nuevo León, Mexico, 2 Facultad de Ingeniería Mecánica y Eléctrica, UANL, San Nicolás de los Garza, Nuevo León, Mexico
Show AbstractThe development of synthetic processes for sulfide nanomaterials is an issue of considerable topical interest. While a number of chemical methods are available and are extensively used, the collaborations are often energy intensive and employ toxic chemicals. On the other hand, the synthesis of inorganic materials by biological systems is characterized by processes that occur at close to ambient temperatures and pressures, and at neutral pH. In this paper we show that CdS and ZnS nanoparticles may be produced at room temperature intracellularly by challenging the fungi, Fusarium and Penicillium sp., with mixtures of cadmium and cinc salts. Extracellular hydrolysis of the anionic metal complexes by cationic proteins secreted by the fungi results in the room-temperature synthesis of crystalline CdS and ZnS nanoparticles that exhibit a signature of agglomeration same as assembly in sizes already of 2 micrometers. X-Ray diffraction and SEM microscopy with EDAX analysis let us to confirm the obtention of CdS and ZnS nanoparticles by this route of synthesis.
9:00 PM - DD16.9
Templated Growth of Semiconductor Nanostructures Using Block Copolymer Lithography
Seth Taylor 1 , Azar Alizadeh 1 , David Hays 1 , Kasi Krishnan 1 , Chris Keimel 1 , Lauraine Denault 1 , Rosalyn Neander 1 , Ken Conway 1 , Oliver Boomhower 1 , Sanjay Krishna 2 , Andreas Stintz 2 , Jay Brown 2 , Edit Braunstein 3 , Colin Jones 3
1 , GE Global Research, Niskayuna, New York, United States, 2 , University of New Mexico, Albuquerque, New Mexico, United States, 3 , Lockheed Martin, Orlando, Florida, United States
Show AbstractSemiconductor nanostructures hold great potential for achieving new capabilities in optoelectronics, field emission, and various sensing and detection technologies, but their applications to date have been limited by processing challenges and scale-up issues. Templated growth of semiconductor quantum dots through a nano-patterned mask allows for precise control over dot size, shape, spacing and uniformity, and is therefore a promising route for fabricating large arrays of quantum confined structures. Here, we report on the templated growth of sub-20 nm InAs nanostructures using molecular beam epitaxy (MBE) in concert with block copolymer lithography. Atomic force microscopy, SEM, and high resolution TEM have been used extensively to characterize nanostructure morphology as a function of different growth parameters, and to further quantify quantum dot size, spacing, uniformity and areal density. Using reactive ion etching to form an oxide mask from a block-copolymer template, we demonstrate a dense and highly uniform array of quantum-confined and optically-active InAs dots on GaAs. Correlations are drawn between the optoelectronic performance of the quantum dots, as measured by photoluminescence (PL) spectroscopy at various temperatures, and their internal (defect) structure as revealed by HRTEM. We discuss the potential for this processing technique to overcome some of the fundamental limitations posed by Stranski-Krastanow-based self-assembly approaches for quantum dot formation.
Symposium Organizers
Moonsub Shim University of Illinois, Urbana-Champaign
Masaru Kuno University of Notre Dame
Xiao-Min Lin Argonne National Laboratory
Ruth Pachter Air Force Research Laboratory
Sanat Kumar Rensselaer Polytechnic Institute
DD17: Synthesis and Characterization of Nanoscale Materials II
Session Chairs
Xiao-Min Lin
Horst Weller
Friday AM, April 13, 2007
Room 2001 (Moscone West)
9:30 AM - **DD17.1
Synthesis of Luminescent and Magnetic Nanoparticles and their Use in Materials- and Life Sciences
Horst Weller 1
1 Physical Chemistry, University of Hamburg, Hamburg Germany
Show AbstractThis talk describes recent developments in the synthesis and characterization of semiconductor and metal nanoparticles. Results on the growth kinetics and the control of size, shape and surface chemistry will be addressed. Examples for 2D and 3D self assembly of nanoparticles are given. We report on the formation of colloidal crystals from semiconductor and magnetic nanoparticles as well as on the formation of ordered films using various coating techniques. Moreover we present measurements on the size-dependent magnetic properties of nanoparticles. We also report on the use of nanoparticles for biological and medical applications which include a robust coating with biocompatible polymers and embedding nanoparticles in polymer vesicles. Examples on the improvement of magnetic resonance imaging using tailored superparamagnetic nanoparticles are given.
10:00 AM - DD17.2
Synthesis of Crystalline BaTiO3 Nanocrystals with Surface Capping Ligands and Self-Assembly of Nanocrystals.
Zhuoying Chen 1 2 , Jiaqing He 3 , Yimei Zhu 3 , Stephen O'Brien 1 2
1 Applied Physics and Applied Math, Columbia University, New York, New York, United States, 2 Columbia Materials Research Science and Engineering Center (MRSEC), Columbia University, New York, New York, United States, 3 Center for Functional nanomaterials, Brookhaven National Laboratory, Upton, New York, United States
Show Abstract10:15 AM - DD17.3
Synthesis, Characterisation and Understanding of the Crystal Growth Mechanism in PbS Nanocrystals
Deborah Berhanu 1 , Paul O'Brien 2
1 The School of Chemistry and the School of Materials, The University of Manchester, Manchester United Kingdom, 2 The School of Chemistry and the School of Materials, The University of Manchester, Manchester United Kingdom
Show AbstractThere is considerable interest in developing simple, inexpensive and environmentally benign protocols to grow metal chalcogenide nanomaterials for practical purposes. Semiconductor nanocrystals of PbS are particularly well investigated for telecommunication and biological applications as it exhibits luminescence in the Near IR region. Consequently quantum dots based on semiconductors of group IV-VI materials are particularly appealing.1 Factors effecting this include the relatively small bulk band gaps (PbS 0.41 eV, PbSe 0.28eV) and strong quantum size effects due to the large Bohr radii of both electrons and holes. We have demonstrated a simple “soft-hydrothermal” route to nanocrystalline PbS and CdS nanoparticles, using air-stable crystalline complexes as single-source precursors.2 This technique was further investigated for the preparation of lead chalcogenide nanocrystals using microwave systems. The “soft-hydrothermal” approach involves a single-step “one-pot” protocol that appeals to chemists and others in the field, providing potential for development of nanomaterials using limited resources. This straightforward technique was used in the present study to investigate the crystal growth mechanism in PbS nanocrystals.1. I. Kang and F.W. Wise, J. Opt. Soc. Am. B, 1997, 14(7), 1632.2. D. Berhanu, K. Govender, D. Smyth-Boyle, M. Archbold, D.P. Halliday and P. O'Brien, Chem. Commun., 2006, in press.
10:30 AM - DD17.4
Synthesis and Spectroscopic Studies of Doped II-VI Chalcogenide Quantum Dots
Paul Archer 1 , Daniel Gamelin 1 , Nick Norberg 1
1 Chemistry, University of Washington, Seattle, Washington, United States
Show AbstractAbstract: The challenge of doping colloidal II-VI chalcogenide semiconductor quantum dots (QDs) is addressed through new preparations and spectroscopic analysis. The use of electronic absorption and magnetic circular dichroism (MCD) spectroscopies as probes of 3d transition metal dopant speciation in TM2+:AE QDs (where TM = Co2+, Mn2+, etc.; A = Zn2+, Cd2+; E = S2-, Se2-) will be described. Recent results relating to giant excitonic Zeeman splittings (ΔEZeeman) and size-dependent charge transfer photoionization processes in doped semiconductor nanocrystals will be presented and discussed with respect to potential applications of doped semiconductor nanostructures.
10:45 AM - DD17.5
Oxide-supported Metal Nanoparticles and their Applications.
Nanfeng Zheng 1 , Galen Stucky 1
1 Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, United States
Show Abstract11:00 AM - DD17.6
Ultra Large Scale and Green Synthesis of Monodisperse Magnetite Nanocrystals.
Cafer Yavuz 1 2 , Jessica Cox 4 , Carmen Suchecki 5 , Angelina Tran 4 , Vicki Colvin 1 2 3
1 Chemistry Dept., Rice University, Houston, Texas, United States, 2 Center for Biological and Environmental Nanotechnology (CBEN), Rice University, Houston, Texas, United States, 4 , Rice University, Houston, Texas, United States, 5 , Northwestern University, Evanston, Illinois, United States, 3 Chemical Engineering, Rice University, Houston, Texas, United States
Show Abstract11:30 AM - DD17.7
Position-Controlled Doping of Semiconductor Nanocrystals
Y. Charles Cao 1 , Yongan Yang 1 , Ou Chen 1 , Alexander Angerhofer 1
1 Chemistry, University of Florida, Gainesville, Florida, United States
Show AbstractThe ability to precisely control the doping of semiconductor nanocrystals can create an opportunity for producing functional materials with new properties, which are of importance to applications such as biomedical diagnosis, solar cells, and spintronics. This opportunity has stimulated research efforts to develop synthetic methods to incorporate dopants into a variety of colloidal semiconductor nanocrystals. It has been found that nanocrystals with dopants inside their crystal lattice can exhibit different properties from those with dopants on their surface. However, less is known on the fundamental question of whether different dopant positions inside nanocrystals can affect physical properties of doped nanocrystals. Herein, we report a new doping approach, using a three-step synthesis to produce high-quality Mn-doped CdS/ZnS core/shell nanocrystals. This approach allows the precise control of Mn radial position and doping level in core/shell nanocrystals. Based on this synthetic advance, we have demonstrated that optical properties of Mn-doped nanocrystals indeed depend on Mn radial positions inside the nanocrystals. In addition, we have synthesized nanocrystals with a room-temperature Mn-emission quantum yield of 56%, which is nearly twice as high as that of the best Mn-doped nanocrystals reported previously. Nanocrystals with such a high-emission quantum yield are very important to applications such as nanocrystal-based biomedical diagnosis.
11:45 AM - DD17.8
Surface Passivation Effects on Optical and Material Characteristics of Silicon Nanocrystals by High Pressure Water Annealing and Forming Gas Annealing.
Hiroyuki Sanda 1 , Maria Makarova 1 , Jenna Hagemeier 1 , James McVittie 1 , Jelena Vuckovic 1 , Yoshio Nishi 1
1 Electrical Engineering Department, Stanford University, Stanford, California, United States
Show Abstract Silicon based photonics is gaining considerable research attention since this technology can realize silicon light emitting devices. Nanocystalline silicon is a promising candidate to achieve such devices because of the efficient photoluminescence (PL) of silicon nanocrystals (Si-nc) and because of the fabrication compatibility with CMOS processing. Currently, the exact mechanism of the emission, the condition to achieve high quantum efficiency and the procedures for effective surface passivation are all active research topics. In this work, Si-nc was fabricated by sputtering and high temperature annealing in a SiO2 matrix. Post Si-nc formation treatments investigated here included both high-pressure water vapor annealing (HWA) and forming gas annealing (FGA). HWA is of interest since it is an effective surface passivation process for porous silicon, while FGA is the classic silicon passivation process. The optical and material characteristics of the nc-Si were measured and compared before and after HWA and FGA by PL, ellipsometry, X-ray photoelectron spectroscopy (XPS), and infrared absorption spectroscopy, for the first time. We co-sputtered Si and SiO2 onto a silicon substrate without rotation so that an across substrate gradient of Si in SiO2 was achieved. The samples were then annealed using the following processes: high temperature annealing at 1100°C for 1 hour in N2, the same 1100°C annealing followed by FGA at 400°C for 30 minutes, and the same 1100°C annealing followed by HWA at 2.6MPa and 260°C for 5 hours. The excess Si content in the SiO2 matrix ranges from 1 atomic % (at%) to 27 at% across the wafer by XPS. The PL intensity in the range of 600-1000nm is maximized at the position with an excess Si of 8 at%. As the excess Si decreases from 8 at%, the PL intensity decreases because of the reduction of the nc-Si density. On the other hand, as the excess Si increases from 8 at%, the PL intensity decreases probably because the crystal size is too large to emit photons. Both HWA and FGA are shown to enhance the PL intensity by about 3 times at the 8 at% excess Si position, for the first time, suggesting that both processes passivate surface dangling bonds of the nc-Si with hydrogen. In addition, the peak wavelength of the PL spectrum, 775nm, shifts to 750nm after HWA, while it stays the same after FGA. This result suggests that water molecules oxidize Si-nc during HWA. Although, the oxidation states of Si are widely distributed from Si0+ to Si4+ after the sputter deposition by the Si 2p XPS analysis, Si0+ and Si4+ dominate after annealing at 1100 °C because of the phase separation to Si and SiO2. XPS depth profiling shows that the excess Si content is uniform across the film thickness after the 1100 °C annealing, suggesting the slow Si diffusion in SiO2. Transmission electron microscopy (TEM) observation and electron spin resonance (ESR) measurement are in progress and will be discussed at the meeting.
12:00 PM - DD17.9
Optical Properties of Chromophoric Thiol Coated Nanoparticles Prepared by Place Exchange Reactions.
Wojciech Haske 1 , Michal Malicki 1 , Seth Marder 1 , Joseph Perry 1
1 Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States
Show Abstract12:15 PM - DD17.10
Electric Field-Driven Route for Nanocrystal Synthesis
Dong Soo Yun 1 , Angela Belcher 1 2
1 Materials Science, MIT, Cambridge, Massachusetts, United States, 2 Biological Engineering Division, MIT, Cambridge, Massachusetts, United States
Show Abstract To date, nanoparticle synthesis has been successfully demonstrated via either aqueous or non-aqueous solvents. Although metallic oxides are optimal materials for a wide variety of applications, the high equilibrium temperature (Te > 200°C ~ 600°C) of phase formation makes their direct nanoparticle synthesis as well as single crystal oxide growth difficult at room temperature using pure aqueous solution. Little research has been done on metal oxides and metallic compounds using surfactant-free aqueous solvents because it is more difficult to make nanoparticles with well-controlled nanocrystalline properties such as crystallinity, shape, size and oxidation under these conditions. Here, we present a new method that uses high electric fields to form both polycrystalline and single crystal metal oxides, such as hafnium oxide, zirconium oxide, Iridium oxide, and iron oxide. Conditions for this synthesis include aqueous solution in less than one minute at room temperature without any additional processing steps. Non-aqueous solvent-mediated metal oxide, such as hafnium oxide and iron oxide single crystals, were also synthesized using this method. The quality of these materials suggest that this is an appropriate method for nanoparticle synthesis of pure metals and metallic compounds using surfactant-free aqueous solutions at room temperature without reducing agents. In addition, the synthesis of multi-component oxides of high equilibrium temperature (Te >200°C) such as Hf(Zr,Al)O2, was demonstrated at room temperature with reactions times under 5 minutes. These materials are not readily formed using traditional nanoparticle synthesis methods.
12:30 PM - DD17.11
Galvanic Replacement Reaction on Mutiply-twinned Ag Nanoparticles in an Organic Medium.
Xianmao Lu 1 , Marquez-Sanchez Manuel 3 , Younan Xia 1
1 Department of Chemistry, University of Washington, Seattle, Washington, United States, 3 I'NEST Group, Philip Morris USA, Richmond, Virginia, United States
Show Abstract12:45 PM - DD17.12
Heterostructured Nanoparticles Directly Synthesized from Gas Phase
YunHao Xu 1 , Jianmin Bai 1 2 , Jian-Ping Wang 1
1 Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, United States, 2 Research Institute of Magnetic Materials, Lanzhou University, Lanzhou, Gansu, China
Show AbstractDD18: Synthesis and Characterization of Nanoscale Materials III
Session Chairs
Masaru Kuno
Xiao-Min Lin
Ruth Pachter
Moonsub Shim
Friday PM, April 13, 2007
Room 2001 (Moscone West)
2:30 PM - DD18.1
Directed Synthesis of High-aspect-ratio Single crystal PbTe nanorods.
Arup Purkayastha 1 , Qingyu Yan 1 , Darshan Gandhi 1 , Binay Singh 1 , Theodarian Borca-Tasciuc 2 , Ganapathiraman Ramanath 1
1 Department of Materials Science and Engineering, [email protected], Troy, New York, United States, 2 Mechanical Aerospace and Nuclear Engineering, Resselaer Polytechnic Institute, Troy, New York, United States
Show AbstractPbTe is a very important material for many applications such as thermoelectric refrigeration and power generation systems, photoconductive device components and infrared detectors. Nanostructuring is an attractive strategy to increase the thermoelectric figure of merit ZT by reaping the benefits of boundary scattering-induced thermal conductivity decrease and quantum-confinement-induced electrical conductivity increase. For example, quantum dot superlattices of PbSeTe/PbTe film exhibit ZT= 1.6, compared to ZT = 0.4 for bulk PbTe. An even higher ZT could be expected by introducing confinement in two dimensions, i.e., in nanorods and nanowires. Although sonoelectrochemical synthesis of PbTe nanorods have been reported, the nanorod length is very small (100-200 nm), limiting its use for device fabrication. Here, we demonstrate a new solvothermal approach to direct the large scale sequential synthesis of ultra long 1-12 nm long single crystal PbTe nanorods with a diameter of ~60-250 nm by converting Te nanotubes of similar dimensions. The nanorod aspect ratio is between 10 to 36, which is the highest reported for PbTe. The Te nanotubes were prepared by solvothermal reduction of tellurium in the presence soft templates L-cystein ethylester dihydrochloride and cetyl ether (brij 52) in ethylene glycol. In situ reaction of the Te nanotubes with Pb salts and hydrazine, which serves as the reducing agent, converts the Te nanotubes into PbTe nanorods. The nanorod aspect ratio is inherited from the aspect ratio for the tellurium rods. X-ray difraction, and energy dispersive X-ray spectroscopy (EDS) reveal the presence of near stoichiometric (50-50) trigonal PbTe phase. The Te nanotube length, and hence that of the nanorods can be adjusted by changing the concentration of cetyl ether and reaction temperature during Te nanotube synthesis. High resolution transmission electron diffraction analyses reveal that each PbSe rod is a single crystals with low defect concentration. In addition to the mechanism of PbTe nanorod formation, we will present the Seebeck coefficient and electrical conductivity of films of the PbTe nanostructures and individual nanorods.
2:45 PM - DD18.2
Interfacial Synthesis of Platinum Nanowire Networks,
Yujiang Song 1 , Robert Garcia 1 2 , Rachel Dorin 1 2 , Haorong Wang 1 2 , Yan Qiu 1 2 , John Shelnutt 1 3
1 Nanostructure and Semiconductor Physics, Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 Chemistry, Chemical & Nuclear Engineering, and Biology Department, The Univeristy of New Mexico, Albuquerque, New Mexico, United States, 3 Department of Chemistry, University of Georgia, Athens, Georgia, United States
Show AbstractPlatinum nanowire networks are obtained via interfacial chemical reaction of platinum complex in chloroform with sodium borohydride in water under vigorous stirring. These wires range from 2 to 5 nm in diameter and are polycrystalline with junctions at every 10-20 nm in length on average. The key to the synthesis is to take advantage the unique environment brought about by the water/oil/surfactant interface. Platinum complexes were transferred from water phase to chloroform phase by dissolving surfactant in chloroform. Surprisingly, at a certain ratio between platinum salt and surfactant, the transfer of platinum to chloroform is complete as monitored by UV-vis spectra. Since control experiments in the absence of the water/oil interface conducted in either water or chloroform phase lead to platinum nanomaterials with different morphologies from the nanowire networks, it is expected that the interfacial environment plays a crucial role for the formation of the interconnected platinum nanowires. A possible mechanism is suggested. This new form of platinum is characterized by transmission and scanning electron microscopy, electron and X-ray diffraction, cyclic voltammetry, and nitrogen adsorption. The materials possess a high surface area (35 m2/g) and random pores in the range of 2 to 10 nm. This synthetic approach is simple, general, and can be used to prepare a variety of metal nanomaterials. For example, by control of the synthetic parameters, palladium nanoKoosh balls and gold nanowires can be obtained. These nanomaterials are expected to have a wide range of potential applications, including as catalysts.Sandia is multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under Contract DEAC04-94AL85000.
3:00 PM - DD18.3
Synthesis of Si/Ge Nanowire Heterostructures for Strain-Controlled Bandstructure Modification.
Teresa Clement 1 , David Smith 2 , Jeff Drucker 3 , S. Thomas Picraux 1 4
1 School of Materials, Arizona State University, Tempe, Arizona, United States, 2 Center for Solid State Science, Arizona State University, Tempe, Arizona, United States, 3 Department of Physics and Astronomy, Arizona State University, Tempe, Arizona, United States, 4 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show Abstract3:15 PM - DD18.4
Synthesis of Epitaxially Aligned Ge/Si Core-shell Nanowires.
Irene Goldthorpe 1 , Joshua Ratchford 2 , Christopher Chidsey 2 , Paul McIntyre 1
1 Department of Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 Department of Chemistry, Stanford University, Stanford, California, United States
Show AbstractDepositing a Si film around a Ge nanowire (NW) creates a structure with additional advantageous properties beyond that of a single element Si or Ge NW. A heteroepitaxially grown shell may allow for engineering of strain in both the shell and the inner core. Moreover, the valence band offset may allow confinement of holes to the core, reducing the influence of surface defects in carrier scattering for p-type NWs. The Ge-core/Si-shell arrangement is desirable for the higher carrier mobilities of Ge and the superior properties of SiO2 passivation.In this work, vertically aligned Ge/Si core-shell NWs have been synthesized by CVD. First, Ge NWs were heteroepitaxially grown on Si(111) substrates; the NW diameter was controlled through the use of monodisperse Au nanoparticles as the catalysts. Silane was then used to deposit the shell. The Au remaining on the Ge NW tips is problematic since (i) the Au can catalyze unwanted Si NW growth and (ii) the Au particles at the NW tips diffuse into the structure at the temperatures required to obtain single crystalline Si shells. Our experiments have investigated a wet chemical etching procedure for Au removal from the Ge NWs with a KI/I2-based solution. This solution does not appear to etch the NW surface, allowing a heteroepitaxial shell to be obtained following the etching procedure. We have also researched the deposition conditions which dictate whether three-dimensional Si islands or a continuous amorphous, polycrystalline, or crystalline Si film forms around the Ge cores during the subsequent Si growth step, and these results will be summarized.
3:30 PM - DD18.5
Diameter Dependence of Interfacial Abruptness in Si/Si1-xGex Heterostructure Nanowires Grown via Vapor-Liquid-Solid Growth.
Trevor Clark 1 2 , Elizabeth Dickey 1 2 , Kok-Keong Lew 1 2 , Pramod Nimmatoori 1 3 , Ling Pan 1 , Joan Redwing 1 2 3
1 Materials Science and Engineering, Penn State, University Park, Pennsylvania, United States, 2 Materials Reserch Institute, Penn State, University Park, Pennsylvania, United States, 3 Chemical Engineering, Penn State, University Park, Pennsylvania, United States
Show Abstract3:45 PM - DD18.6
Growth and Electrical Properties of Epitaxial Silicon Nanowires grown by Vapor-Liquid-Solid Growth on (111)Si Substrates
Sarah Dilts 1 , Rebeca Diaz 2 , Chad Eichfeld 1 , Bangzhi Liu 1 , Suzanne Mohney 1 , Theresa Mayer 2 , Joan Redwing 1 2
1 Materials Science and Engineering, Penn State University, University Park, Pennsylvania, United States, 2 Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractHigh density arrays of epitaxially-oriented silicon nanowires (SiNWs) are of interest for the fabrication of vertical wrap-gate nanowire transistors. These structures have traditionally been fabricated by the vapor-liquid solid technique using Au thin films deposited on (111)Si substrates and SiCl4 as the source gas for wire growth. In this process, epitaxial orientation of the nanowires is believed to be promoted by a combination of high growth temperature (~900°C) and the presence of HCl, which acts to etch oxide from the substrate surface. Our initial studies have focused on investigating the effect of growth conditions on wire orientation, structure and growth rate with the aim of developing a better understanding of the role of growth chemistry in this process. Silicon nanowire arrays were fabricated using 1 nm Au thin films deposited on (111)Si substrates in an atmospheric pressure hot-wall quartz tube reactor using SiCl4 as the source gas in an H2 carrier gas. Wire orientation was found to be strongly dependent on the growth temperature with ~ 80% of the SiNWs being <111> oriented perpendicular to the substrate at 900°C but dropping to ~18% at 800°C. At low SiCl4 partial pressures (PSiCl4), the growth rate of the wires increases with increasing PSiCl4 reaching a maximum of ~ 3 μm/min at PSiCl4 of 3.7 Torr. Beyond this point, the growth rate begins to decrease with increasing PSiCl4 due to a shift in gas phase chemistry which promotes the reverse HCl etching reaction similar to what is observed in thin film deposition. The resistivity of nominally undoped SiNWs grown under these conditions was studied using four-point measurements carried out on individual SiNWs released from the substrate by ultrasonic agitation and assembled onto pre-patterned back-gated test structures using field-assisted assembly. Nominally undoped SiNWs grown on p-type (111)Si substrates (ρ=1-15 Ω-cm) were determined to be p-type with a room-temperature resistivity on the order of 800 Ω-cm, indicating the presence of unintentional acceptors in the nanowires. By using high resistivity (ρ=2000-10000 Ω-cm) (111)Si substrates, the wire resistivity increased approximately one order of magnitude, indicating that dopants in the substrate are incorporated in the wires during growth and contribute, in part, to the background electrical properties of the nanowires.
4:30 PM - DD18.7
Atomic, Electronic, and Three-Dimensional Characterization of Core/Shell Nitride Nanowires.
Ilke Arslan 1 , Alec Talin 1 , Francois Leonard 1 , George Wang 2
1 , Sandia National Laboratories, Livermore, California, United States, 2 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractSemiconductor nanowires are being developed as nanoscale building blocks for a variety of new nano-device applications. With these new developments comes a need for sophisticated characterization of the materials properties of the nanowires. The traditional technique of two dimensional (2-D) transmission electron microscopy (TEM), which has thus far been useful for the study of single crystals where the third dimension is uniform, is no longer sufficient to characterize the complex, three dimensional (3-D) structures that define nanotechnology. Therefore, to gain a full understanding of the structure-property relationships of the nanowires, we use a combination of atomic-resolution imaging, atomic-resolution electron energy-loss spectroscopy (EELS), energy dispersive x-ray (EDX) spectroscopy, and three dimensional imaging in the scanning transmission electron microscope (STEM). In particular, it is important to understand the morphology of the nanowires in 3-D since their materials properties are controlled by their 3-D shape and size. The relatively new technique of STEM tomography that we highlight in this paper allows us to reconstruct nanostructures with a resolution approaching 1nm in all three spatial dimensions. Here we present a comprehensive study of GaN/AlN core/shell nanowires, which could have applications in nanophotonics and high mobility nanoelectronics. Using STEM tomography, we are able to directly image the size, shape and morphology of the nanowires in three dimensions. Interestingly, while prior conductivity measurements indicate that the GaN/AlN nanowires are more conductive than GaN in general, there are some cases in which GaN/AlN nanowires of the same length and diameter can be insulating. Our results suggest that this may be due to a discontinuity of the GaN core observed in some of the nanowires, leading to a bamboo-like structure. We will present a detailed analysis comprising 2-D STEM images and 3-D tomograms (providing nanowire morphology) as well as the complementary information from EELS and EDX spectra (providing nanowire compositional analysis). Work at Sandia is supported by the Department of Energy, under contract DE-AC04-94AL85000.
4:45 PM - DD18.8
Selective Plating on n-Type Silicon Nanowires for Junction Delineation and Nanostructure Fabrication
Chad Eichfeld 1 2 , Carolyn Wood 2 3 , Sarah Dilts 1 , Bangzhi Liu 1 , Joan Redwing 1 2 , Suzanne Mohney 1 2
1 Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania, United States, 2 Center for Nanoscale Science, Pennsylvania State University, University Park, Pennsylvania, United States, 3 Department of Physics, Illinois Institute of Technology, Chicago, Illinois, United States
Show AbstractThe in situ growth of p-n junctions in silicon nanowires enables the fabrication of a variety of nanoscale electronic devices. We have developed a method for selective coating of Au onto the n-type segments of silicon nanowire p-n junctions, providing feedback into the study of the growth of nanowire homojunctions. Selective plating allows for quick verification of the position of p-n junctions along the nanowire using scanning or transmission electron microscopy, and it allows for measurement of the length of the p- and n-type segments. Dopant modulated silicon nanowires were fabricated using Au-catalyzed vapor-liquid-solid growth using SiH4 as the source gas and PH3 for n-type doping. Nanowires were fabricated with multiple n+ segments of increasing length that were grown between nominally 1 um long p- segments. Segments of n-type silicon as short as 100 nm in nanowires that were 100 nm in diameter have been plated. Selective plating is furthermore attractive for placing Au catalyst at preset locations along a silicon nanowire for subsequent vapor-liquid-solid growth. The electrochemical mechanism for the selectivity of the plating process is also discussed.
5:00 PM - DD18.9
Springs, Rings, and Spirals of Rutile-Structured Tin Oxide Nanobelts.
Rusen Yang 1 , Zhong Lin Wang 1
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractSynthesis of nanomaterials with well controlled size, morphology and chemical composition has attracted increasing interests, because those novel nanostructured materials are crucial for exploring the chemical and physical properties of those materials originating from their shape, decreased dimension size and crystallographic structure. Wurtzite structured ZnO has been synthesized in the formation of single-crystalline nanorings, nanosprings and nanospiral, [1, 2] which was proposed to be related to the non-central symmetry of wurtzite structure and the spontaneous polarization. In agreement to the polarization induced growth model, we have discovered for the first time the formation of single-crystalline SnO2 springs, rings and spirals [3]. All of the SnO2 nanostructures were synthesized using a solid-vapor process in a horizontal tube furnace and their composition, morphology and crystallographic structure were confirmed by EDS, SEM and TEM. A detail analysis showed that the growth of those nanomaterials could be also understood on the basis of polar surfaces of the rutile-structured SnO2. The SnO2 nanobelts that made of the ring/spring grew along ~[0-11] with dominant +-(011) polar side surfaces. Bending of the belt to form a ring can decrease the electrostatic energy from the spontaneous polarization. The minimization of the total energy contributed by electrostatic polarization energy and elastic deformation energy determines the final morphology of the SnO2 nanobelt, resulting in the formation of the ring, multiply looped spiral or even helical structure.[1] (a) X.Y. Kong; Z.L. Wang, Nano Lett. 3 (2003) 1625-1631. (b) X.Y. Kong; Z.L. Wang; Appl. Phys. Lett. 84 (2004) 975-977. (c) X.Y. Kong; Y. Ding; R.S. Yang; Z.L. Wang, Science, 303 (2004) 1348-1351. (d) R.S. Yang; Y. Ding; Z.L. Wang, Nano Lett. 4 (2004) 1309-1312[2] R.S. Yang, Z.L. Wang, J. Am. Chem. Soc. 128 (2006) 1466-1467.
5:15 PM - DD18.10
Synthesis and Characterization of Novel Nanostructured Thermoelectric Materials.
Xiaofeng Qiu 1 2 , Clemens Burda 1 2
1 Center for Chemical Dynamics and Nanomaterials Research, Case Western Reserve University, Cleveland, Ohio, United States, 2 Chemistry, Case Western Reserve University, Cleveland, Ohio, United States
Show Abstract5:30 PM - DD18.11
Synthesis of Diameter-controlled Bismuth Nanowires using Porous Anodic Alumina Template Coated by Atomic Layer Deposition.
Kyungeun Lee 1 , Bo Kyung Ahn 1 , Sihyeong Kim 1 , Changdeuck Bae 1 , Hyunjung Shin 1
1 School of Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of)
Show Abstract5:45 PM - DD18.12
High Aspect Ratio Nanowires: New Opportunities in Synthesis and Assembly
Byron Gates 1 , Nazanin Mobrhan-Shafiee 1 , Nathanael Sieb 1 , Elham Majidi 1
1 Chemistry, Simon Fraser University, Burnaby , British Columbia, Canada
Show AbstractNew opportunities exist in the synthesis and assembly of high aspect ratio nanowires. It is, hypothetically, much easier to incorporate individual nanowires rather than nanorods into the appropriate test devices to characterize electrical properties of the nanostructured material. Standard lithography tools could be used to pattern the appropriate electrodes for characterizing high aspect ratio nanowires. The appropriate choice of synthetic techniques is, however, essential to achieve nanowires with the necessary aspect ratios for incorporation into these test devices. This presentation will cover recent advances in the development of solution phase synthesis of these nanostructures. Solution phase techniques were chosen, in part, for the ease of incorporating dopants, versatility of surface modification, and simplicity of scaling-up the synthesis to large quantities. Assembly of these nanostructures is increasingly challenging as the aspect ratio also increases. Techniques are presented that address the issues of dispersion, entanglement, and placement of these nanowires into well-defined patterns.