Symposium Organizers
David B. Mitzi IBM T. J. Watson Research Center
David Ginley National Renewable Energy Laboratory
Bernd Smarsly Justus Liebig University Giessen
Dmitri V. Talapin The University of Chicago
F1: Nano-Related Deposition
Session Chairs
Tuesday PM, December 02, 2008
Room 208 (Hynes)
9:30 AM - **F1.1
Self-organization and Chemical Doping in Solution Processed Semiconductor Nanocrystal Superlattices.
Christopher Murray 1
1 Chemistry and Materials Science & Eng, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show Abstract10:00 AM - F1.2
Binary Superlattices of PbSe and CdSe Nanocrystals.
Daniel Vanmaekelbergh 1 , Karin Overgaag 1 , Bart de Nijs 1 , Wiel Evers 1 , Rolf Koole 1 , Mark Boneschanscher 1
1 Debye Institute for NanoMaterials Science, University of Utrecht, Utrecht Netherlands
Show AbstractThe formation of binary superlattices via colloidal crystallization is the most promising method to realize nanostructured solids in which different materials are in near contact and ordered in a well-defined 3-D geometry. Despite the obvious importance for novel applications in opto-electronic materials, studies of nanocrystal superlattices consisting of two types of semiconductor quantum dots have been quite limited (1-3). In this presentation we report on the self-organization of PbSe and CdSe nanocrystals into binary superlattices upon evaporation of the solvent from a mixed suspension at elevated temperatures and reduced pressure (3). We show that, besides the choice of the solvent, the size-and concentration ratio of both types of nanocrystals are the relevant parameters determining the composition and structure of the superlattice. We demonstrate AB, AB2, AB5 and AB13 structures (A=PbSe, B= CdSe) obtained by varying the diameter ratio PbSe/CdSe between 0.5 and 0.8. We show that binary superlattices can have an intricate structure that is best resolved by 3-D TEM (tomography). The results are discussed on the basis of newly developed simulation models based on hard-sphere building blocks. The electronic properties of a number of PbSe/CdSe NC superlattices are currently under study. 1) J. J. Urban et al., Nature Mat. 6, 115 (2007)2) Z. Y. Chen et al. J. Am. Chem. Soc. 129, 15702 (2007)3) K. Overgaag et al., J. Am. Chem. Soc. 130, 7833 (2008)
10:15 AM - F1.3
Thin films of Side-functionalized Poly(3-hexylthiophene) and Thymine-capped CdSe Nanocrystals Obtained by Hydrogen Bond Assisted Layer-by-layer Assembly.
Julia De Girolamo 1 , Adam Pron 1 , Peter Reiss 1
1 INAC/SPrAM, CEA Grenoble, Grenoble France
Show AbstractHybrid materials composed of conjugated polymers and semiconductor nanocrystals are promising systems for the fabrication of low cost, large area photovoltaic devices based on the so-called bulk-heterojunction concept. However, in simple blends of both components, generally undesired phase segregation on a submicron level occurs. We present a new approach to overcome this problem and to achieve morphology control of hybrid material thin films. It is based on the molecular recognition process via hydrogen bonding between complementary chemical groups in the side chain of the polymer and on the nanocrystal’s surface.A new copolymer was synthesized, namely poly(3-hexylthiophene) bearing oxydiaminopyrimidine side groups, which are capable of forming triple hydrogen bonds with mercaptohexylthymine-capped CdSe nanocrystals. Due to their different solubility parameters, the functionalized components can be directly deposited on various substrates (glass, ITO, silicon oxide) using the layer-by-layer method. This technique, based on the alternated dipping of the substrate into the polymer solution and into the NCs’ dispersion, allowed us to control the composition and thickness (range: 30-150 nm) of the hybrid films on a molecular level. In addition, the materials’ consumption is significantly reduced in the dip-coating process with respect to the deposition via spin-coating, usually applied for the processing of hybrid materials.Complementary SEM and SAXS investigations of the deposited layers indicate that the polymer and the nanocrystal phases form a quasi-interpenetrating network, which is favourable for their application in thin film solar cells relying on the bulk heterojunction concept. First device tests clearly show the photovoltaic effect with conversion efficiencies in the typical range (0.1% for an active surface of 28 mm2 under AM 1.5 conditions using 100 mW/cm2 simulated white light) observed for blends of 5 nm spherical CdSe NCs with poly(hexylthiophene) or MEH-PPV. Future device improvement is expected through the optimization of the number of deposited bilayers, NCs’ composition, shape and surface chemistry, to list the principal parameters.
10:30 AM - F1.4
Organizing Nanoparticles using Self Assembled Peptide Nanostructures.
Nikhil Sharma 1 2 , Matthew Lamm 1 2 , Darrin Pochan 1 2
1 Materials Science & Engineering, University of Delaware, Newark, Delaware, United States, 2 , Delaware Biotechnology Institute, Newark, Delaware, United States
Show AbstractThe “bottom-up” methodology consists of designing recognition into molecules that then self-assemble into the desired nano-architecture in the appropriate microenvironment. Peptides undergo self-assembly in solution to form hierarchal nanostructures. Herein, we demonstrate the use of a peptidic template for the construction of parallel, linear arrays of inorganic nanoparticles. A 20 amino acid peptide, consisting of alternating hydrophilic (lysine) and hydrophobic (valine) residues flanking a central diproline turn sequence (VKVKVKVKVPPTKVKVKVKV-NH2) was employed as a nano-scale template for the organization of 2nm gold particles. This peptide self assembles into laminated fibrillar morphology in solution and has a periodic nanostructure consisting of alternating hydrophobic and hydrophilic layers with a lateral periodicity of 2.5 nm. Negatively charged gold nanoparticles are templated into the positively charged lysine layer through electrostatic interaction and are aligned within the template that itself swells to a periodic spacing of 4.0 nm in order to accommodate the particles. These 1D nanoparticle arrays have potential applications in fields like nano-electronics, and we are currently attempting to create arrays of quantum dots and hetero-structures of metal and semiconductor particles.
10:45 AM - F1.5
Assembly and Conductivity of Nanocrystal Solids.
Dmitri Talapin 1 2 , Maksym Kovalenko 1 , Elena Shevchenko 2 , Jong-Soo Lee 1
1 , The University of Chicago, Chicago, Illinois, United States, 2 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States
Show Abstract11:30 AM - **F1.6
Structure and Kinetics of Nanocyrstal Self-assembly Probed by Small Angle X-ray Scattering Techniques.
Xiao-Min Lin 1
1 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States
Show Abstract12:00 PM - F1.7
Assembly, Roughness Control, and Arbitrary Chemical-Physical Functionalization of Nanoparticle Thin Films for Optical Applications.
Zekeriyya Gemici 1 , Hiroomi Shimomura 2 , Robert Cohen 1 , Michael Rubner 2
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 AbstractNanoparticles are indispensable ingredients of solution-based optical, dielectric, and catalytic thin films. While solution-based methods are promising low-cost alternatives to vacuum methods, they can have significant limitations. Coating uniformity, thickness control, roughness control, mechanical durability, and incorporation of a diverse set of functional organic molecules into nanoparticle thin films are major challenges.We have used the electrostatic layer-by-layer (LbL) assembly technique to make uniform, conformal multi-stack nanoparticle thin films for optical applications with precise thickness control over each stack. Two particularly sought-after optical applications are broadband antireflection (AR) and structural color. The effects of inter-stack and surface roughness on optical properties of these constructs (e.g., haze and spectral response) have been studied quantitatively using a combination of Fourier-transform methods and atomic force microscopy (AFM) measurements. Deconvoluting root-mean-square (RMS) roughness into its large-, intermediate-, and small-scale components enables enhanced optical simulations. A 4-stack broadband AR coating (<0.5% average reflectance in the visible range, and 0.2% haze) composed of alternating high-index (n~2.1) and low-index (n~1.3) stacks has been made on glass substrate. Films calcinated at 550°C endure a one-hour-long cloth cleaning test under 100 kPa normal stress.Beyond the direct assembly of multi-stack nanoparticle thin films, it would be highly desirable to identify post-assembly modification methods that supplement thickness and roughness control with chemical functionalization. Hydrophilic, hydrophobic, reactive, or inert chemical vapors capillary-condense in the vicinity of contact points between nanoparticles with equal facility. This phenomenon can be used advantageously to functionalize nanoparticle assemblies. The volume fraction of the condensate is particle size-dependent, which allows targeted functionalization in a multi-stack LbL assembly. 2-stack films composed of 8nm and 50nm SiO2 particles on the bottom and top stacks, respectively, were functionalized with oligomers (e.g., PDMS) or UV-sensitive monomers (e.g., tri(ethyleneglycol) dimethacrylate (TEGDMA)). The condensate volume fraction in the bottom stack was significantly higher than that in the top stack, and excellent broadband AR functionality (<0.6% average reflectance in the visible range) resulted from a mere 160nm-thick film. UV-crosslinking ability was demonstrated for TEGDMA-functionalized films. The PDMS-functionalized film was also assembled on epoxy microlenses, and showed no optical or mechanical failure upon repeated rapid (30s) heating-cooling cycles between 25°C and 260°C. Finally, we show that capillary condensation can be used to enhance mechanical durabilities of otherwise delicate nanoparticle assemblies, as well as to prevent their physical-chemical vulnerability to moisture.
12:15 PM - F1.8
Nanopatterning of Narrow-Gap Quantum Dots via “Soft” Electron Beam Lithography (soft-eBL).
Bin Liu 1 , Aiming Yan 1 , Tao Sun 1 , Indika Arachchige 2 , Mercouri Kanatzidis 2 , Vinayak Dravid 1 3
1 Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States, 2 Department of Chemistry, Northwestern University, Evanston, Illinois, United States, 3 International Institute of Nanotechnology, Northwestern University, Evanston, Illinois, United States
Show AbstractSignificant progress in the synthesis of narrow-gap quantum dots, such as PbTe nanocrystals, has triggered recognition of their potential in photovoltaic, thermovoltaic, and thermoelectric applications. Some of the recent advances in enhancing the thermoelectric figure of merit are associated with these materials, due to the strong quantum-confinement effect as well as large phonon scattering. It is essential to develop techniques to fabricate nanostructures containing quantum dots to obtain not only the desired internal microstructures and grain boundary properties, but also to simultaneously maintain the nanoscale particle size. Furthermore for building devices, the site-specificity of the technique and its compatibility with traditional microfabrication procedures are also required. In this study, a versatile nanopatterning approach, soft-eBL, is being employed to prepare various nanostructures. By collectively combining electron beam lithography and deposition of solution precursors of narrow-gap quantum dots, nano-rings/dots/lines of PbTe or/and SnTe are fabricated. By tuning preparation conditions, the nanocrystals are directed to exhibit either short range or long range packing order, which has been confirmed by high-resolution scanning electron microscopy (HRSEM) and scanning transmission electron microscopy (STEM). Quantum-dot nanolines, different from thin-film superlattices, introduce the confinement in one more dimension, which have been confirmed by theoretical study to show higher figure of merit. Chemical treatment with hydrazine and mild heating are performed to increase the electrical conductivity while maintaining high phonon scattering, and thus to increase the thermoelectric figure of merit. Moreover, the nanocrystals with n- or p-typesemiconducting property are also being built into field-effect transistors, which serve as good alternatives to traditional semiconductor circuits. The presentation will cover aspects of soft-eBL nanopatterning and measurements of colloidal assembly of thermoelectric nanostructures.
12:30 PM - F1.9
Broad-Band, Low-Threshold Amplified Spontaneous Emission from Giant Nanocrystal Quantum Dots.
Florencio Garcia-Santamaria 1 , Yongfen Chen 1 , Richard Schaller 1 , Jennifer Hollingsworth 1 , Victor Klimov 1
1 Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractNanocrystal quantum dots (NQDs) are nanosized crystalline semiconductor particles that show near-unity photoluminescence quantum yields and size-dependent emission colors tunable through the quantum-confinement effect. Because of these properties, nanocrystals are attractive materials for various light-emitting applications including optical amplification and lasing. Due to the almost exact balance between absorption and stimulated emission in nanoparticles excited with single electron-hole pairs (excitons), optical gain can only occur when nanocrystals contain at least two excitons. A complication associated with this multiexcitonic nature of light amplification is fast, picosecond optical-gain decay induced by nonradiative Auger recombination, in which one exciton recombines by transferring the energy to the other. A few years ago, it was demonstrated that close-packed films of NQDs can still show both optical gain and amplified spontaneous emission (ASE) when excited with short and intense laser pulses [1]. However, the ASE thresholds are quite high (several mJ/cm2), which seriously hinders lasing applications of NQDs. Here, we present new results from our studies of dense films made of a new type of nanocrystals dubbed “giant” quantum dots (g-NQDs) [2]. These NQDs comprise an emitting core particle of CdSe overcoated with a very thick shell (up to 20 monolayers) of wider-gap CdS. For this new type of NQD, we observe that the ASE threshold drops down to just a few μJ/cm2, which is almost three orders of magnitude lower than that previously reported for CdSe NQDs. We explain this result by a significant increase in the absorption cross-section of g-NQDs compared to traditional nanocrystals and lengthening of biexciton lifetimes. We also observe other unusual optical-gain behaviors for these structures such as multi-band ASE spectra, in which the band-edge emission co-exist with stimulated emission features due to transitions involving excited electronic states. The overall spectral range of optical amplification extends over more than 500 meV; such broad-band ASE has never been previously observed for other types of optical gain media. These results demonstrate that g-NQDs are very promising materials for applications in practical lasing technologies.[1] V. I. Klimov, A. A. Mikhailovsky, Su Xu, A. Malko, J. A. Hollingsworth, C. A. Leatherdale, H.-J. Eisler, M. G. Bawendi, Optical Gain and Stimulated Emission in Nanocrystal Quantum Dots, Science 290, 314 (2000).[2] Y. Chen, J. Vela, H. Htoon, J. L. Casson, D. J. Werder, D. A. Bussian, V. I. Klimov, J. A. Hollingsworth. “Giant” Multishell CdSe Nanocrystal Quantum Dots with Suppressed Blinking, J. Am. Chem. Soc. 130, 5026 (2008)
12:45 PM - F1.10
Electroluminescence from Core/Doped-Shell Nanoparticles using Transparent Metal Oxides.
Vanessa Wood 1 , Jonathan Halpert 2 , Matthew Panzer 1 , Moungi Bawendi 2 , Vladimir Bulovic 1
1 Department of Electrical Engineering and Computer Science, MIT, Cambridge, Massachusetts, United States, 2 Department of Chemistry, MIT, Cambridge, Massachusetts, United States
Show AbstractF2: Solution Processed Electronic/Optical Films and Devices
Session Chairs
Tuesday PM, December 02, 2008
Room 208 (Hynes)
2:30 PM - **F2.1
Nanocrystal-Based Thin Film Optoelectronic Devices: Deposition and Characteristics.
Moungi Bawendi 1
1 Department of Chemistry, MIT, Cambridge, Massachusetts, United States
Show Abstract3:00 PM - F2.2
Patterned Deposition of Solution-Processed Colloidal Nanocrystal Quantum Dots for LEDs Aplications.
Jian Xu 1 , Ting Zhu 1 , Fan Zhang 1 , Jerzy Ruzyllo 2 , Yongqiang Wang 3
1 Engineering Science and Mechanics, Penn State University, University Park, Pennsylvania, United States, 2 Electrical Engineering, Penn State University, University Park, Pennsylvania, United States, 3 , Ocean NanoTech LLC, Fayetteville, Arkansas, United States
Show AbstractThe emergence of colloidal quantum dot-based light emitting diodes (QD-LEDs) offers a great prospect for developing low-cost, efficient, bright, color-saturated, large-area color displays compatible with flexible substrates. An imminent hurdle along the roadmap to QD-LED-based displays is, however, the lack of an appropriate technology to efficiently deposit and pattern QD-layers with precise controls over thickness, composition, surface morphology, and resolution needed to fabricate RGB-pixel arrays of bright QD-LEDs over large surface areas for passive/active matrix displays. Compared to most solution-processed organic LEDs, the efficiency and brightness of QD-LEDs are highly dependent on the thickness of the emissive QD-layer in the device active region. To date, almost all the record-performances of QD-LEDs have been achieved with devices containing QDs of 1-5 monolayer (ML)-thickness. Thicker QD-active regions result in an increase of the operating voltage and decrease of the carrier-injection efficiency due to the slow dot-dot transport. In this conference we will introduce a process of mist-deposition which allows for the simultaneous assembly and patterning of QDs in QD-LED fabrication with precise controls over thickness. The technology of mist deposition was originally developed for the liquid-source chemical deposition of ultra-fine films of ferroelectrics, high-k dielectrics for MOS gates and other applications in the microelectronics industry. It was adapted in the present work to deliver emissive QDs for the formation of ultrathin active layers in QD-LEDs. During the deposition submicron mists of QD solutions are softly and uniformly transported onto the substrate surface, where they subsequently coalesce at a controlled rate, allowing for a higher degree of thickness- and morphology-control as well as lower waste as compared to spin coating. Microscopic characterization of mist-deposited QD-films has indicated that tight controls over the thickness and surface morphology of QD-layers can be achieved by tailoring the process variables. A QD-LED containing the mist-deposited emissive QD-layer was demonstrated with defect-free and uniform brightness. Furthermore, the technique of successive mist-deposition of multi-color QDs through a set of registered shallow masks was employed to create and investigate a 6×6 matrix of alternating pixels composed of 5nm-diameter CdSe(ZnS) QDs (green) and 8nm-diameter CdSe(ZnS) QDs (red) on a single substrate, suggesting the full capacity of mist-deposition technology in the future development of colorful QD-LED displays. It is expected that superior QD-LED performance can be achieved by optimizing the multiple parameters in the mist-deposition process. The demonstrated approach provides a solid platform for the next-stage development of multicolor QD-LED matrices by selectively mist-depositing multispectral QDs with shadow masks.
3:15 PM - F2.3
Ambipolar Behavior in Ion Gel Gated PbSe Nanocrystal Thin Film Transistors.
Moon Sung Kang 1 , Jiyoul Lee 1 , David Norris 1 , C. Daniel Frisbie 1
1 Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractWe present a new type of field-effect transistor (FET) based on films of PbSe nanocrystal in combination with ion gels as the dielectric material. Prior to applying ion gel, PbSe nanocrystal films were treated with hydrazine and stored under vacuum. Gating the film with a conventional SiO2 dielectric, p-channel FETs were obtained with hole mobilities of 0.08 cm2/Vsec and current modulation of < 102 with applied gate voltage of -100 V to 100 V . The same nanocrystal film was then gated with ion gel dielectric, which has large specific capacitance (~ 30 μF/cm2). Ambipolar behavior was observed with improved device performance. In particular, the ambipolar transistor yielded electron and hole mobilities up to 1.9 and 0.2 cm2/Vsec, respectively and current modulations of 102 to 103 with applied gate voltage of -2 V to 2 V.
3:30 PM - F2.4
Nanoscale Zinc Oxide as Semiconductor Material in a Printed Field Effect Transistor Device.
Joerg Schneider 1 , Rudolf Hoffmann 1 , Andreas Klyszcz 2
1 Chemistry, TU Darmstadt, Darmstadt Germany, 2 , Merck, KGaA, Darmstadt Germany
Show AbstractIt is a challenge to develop flat printable electronics based solely on inorganic materials as an active semiconductor. This could be the basis for flexible displays or electronic paper when the active material is processable from solution, shows very good adherence to flexible substrates and excellent physical performance. To meet these challenges any material considered requires a tuned set of functional properties. In general inorganic semiconductors are in advantage over organic materials as far as their physical performance is concerned. However, often processing and adherence to substrates is a problem with inorganic semiconductors. ZnO is available in various morphologies as transparent oxide, it is non toxic, inexpensive and is well known for its promising physical semiconductor properties. Despite a couple of recent reports on the deposition of zinc oxide thin layers in FET devices, processing from solution and conversion into the active FET channel electrode under fairly mild conditions is a great challenge. Chemical bath deposition techniques and sol-gel processes were mainly investigated in this regard. However, both techniques typically require either high processing temperatures (above 300°C) or long reaction times and are thus inappropriate for printing applications on flexible polymer based substrates under state of the art printing conditions. Processing temperatures well below 200° C are the goal for the formation of semiconducting inorganic thin films onto such substrates. We will report on synthesis of a molecular precursor, its use in the formation of naocrystalline ZnO and its conversion into self adhering films which can be deposited on plastics as well as more conventional substrates. Moreover the electrical performance of nanocrystalline ZnO derived therefrom is reported.
3:45 PM - F2.5
High Performance Polymer/ceramic Nanocomposites Based on Surface-modified Metal Oxide Nanoparticles using Functional Phosphonic Acids for Electronic Applications.
Philseok Kim 1 , Simon Jones 1 , Peter Hotchkiss 1 , Xiao-hong Zhang 2 , Natalie Doss 1 , John Tillotson 1 , Benoit Domercq 2 , Joshua Haddock 2 , Jiangyu Li 3 , Bernard Kippelen 2 , Yingying Lu 4 , Qing Wang 4 , Seth Marder 1 , Joseph Perry 1
1 School of Chemistry and Biochemistry, Georgia Inst. of Technology, Atlanta, Georgia, United States, 2 School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Department of Mechanical Engineering, University of Washington, Seattle, Washington, United States, 4 Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractPolymer/ceramic nanocomposites benefit by combining high permittivities (k) of metal oxide nanoparticles with solution-processibility and high dielectric strength of polymeric hosts. Simple mixing of nanoparticles and polymer generally results in poor quality materials due mainly to the agglomeration of nanoparticles and poor miscibility of nanoparticles in host materials. We have shown that surface modification of metal oxide nanoparticles with phosphonic acid-based ligands affords robust surface modification and improves the processiblity and the quality of nanocomposites. We report on the use of phosphonic-acid modified barium titanate (BaTiO3) nanoparticles in dielectric nanocomposites and their applications to high-energy-density capacitors and solution-processible high permittivity gate insulators in organic field-effect transistors (OFETs). Surface modification of BaTiO3 nanoparticles allowed high quality nanocomposite thin films in ferroelectric polymer hosts such as poly(vinylidene-co-hexafluoropropylene) and poly(vinylidenefluoride-co-trifluoroethylene-co-chlorotrifluoroethylene) with large volume fractions (up to 50 vol. %), which are potentially useful materials for electrical energy storage. Similarly, the use of phosphonic acid-modified BaTiO3 nanoparticles in cross-linked poly(4-vinylphenol) allowed to form solution-processible high permittivity nanocomposite gate insulators for organic field-effect transistors. High quality nanocomposite thin films at large nanoparticle volume fractions (up to 37 vol. %) with a large capacitance density (~50 nF/cm^2) and a low leakage current (10^-8 A/cm^2) were obtained. Pentacene-based p-type OFETs using these nanocomposites showed a large on/off current ratio (Ion/off 10^4 - 10^6) due to the high capacitance density and small leakage current of the gate insulator. We will also present the results from a recent experimental and theoretical study where the BaTiO3 nanoparticle volume fraction was systematically varied in a high permittivity (k = 11) host to find the optimum permittivity and dielectric strength providing a guideline to optimize the volume fractions for achieving maximum energy storage density.
4:30 PM - **F2.6
Chemically Derived Nanostructures for Emerging Challenges in Semiconductor Electronics.
Xiangfeng Duan 1
1 Chemistry and Biochemistry, UCLA, Los Angeles, California, United States
Show Abstract5:00 PM - F2.7
Rapid Electrical Sintering of Nanoparticle Stuctures.
Mark Allen 1 , Mikko Aronniemi 1 , Ari Alastalo 1 , Tomi Mattila 1 , Kimmo Ojanpera 1 , Mika Suhonen 1 , Heikki Seppa 1
1 VTT Sensors and Wireless Devices, VTT, Espoo Finland
Show AbstractWe present a method to electrically sinter nanoparticle structures [1,2]. For an inkjetted silver nanoparticle conductor, a conductance increase of more than five orders of magnitude is demonstrated to occur in less than a millisecond such that most of the conductance change (four orders of magnitude) takes only a few microseconds.The demonstrated method is an alternative to, for example, conventional thermal (oven) sintering, laser sintering [3], photonic sintering [4] and microwave sintering [5].A central prerequisite for the rapidness of the curing process is the voltage boundary condition. Namely, the resistivity of the printed structure being a decreasing function of local temperature results in increase of power dissipation and thus causes a strong positive feedback. The obtained final conductivities are within a factor of two from the bulk silver conductivity, as calculated for the external geometric dimensions of the structure which overestimates the particulate structure volume. The experiments have been performed at ambient temperature (without any convective or radiative heating).The central benefits of the method include (i) reduced substrate heating as illustrated by fabricating high-quality conductors on a paper substrate that does not tolerate the oven sintering temperature of the ink, (ii) easy control of the final conductivity level with external bias resistors, and (iii) suitability of the method for area-specific processing (direct writing).To gain insight into the electrical sintering process, we have performed modelling which takes both macroscopic material properties as well as electron tunnelling processes into account. The experimental results include IR (λ ~ 10um) video microscopy. In addition to metallic conductors, the method is potentially applicable to other inorganic conductors such as indium-tin-oxide (ITO) and semiconducting materials. More generally, the method offers a versatile tool in nanotechnology for electrical functionalization of the nanoparticle structures.[1] Mark L Allen, Mikko Aronniemi, Tomi Mattila, Ari Alastalo, Kimmo Ojanperä, Mika Suhonen and Heikki Seppä, Nanotechnology 19 175201 (2008).[2] M. Allen and H. Seppä, Patent Application WO2008009779A1.[3] N.R. Bieri, J. Chung , S.E. Haferl, D. Poulikakos D andC.P. Grigoropoulos, Appl. Phys. Lett. 82 3529 (2003). [4] K. A. Schroder, S. C. McCool and W. R. Furlan, NSTI Nanotech 2006. www.novacentrix.com. [5] J. Perelaer, B.-J. deGans and U.S. Schubert , Adv. Mater. 18 2101 (2006).
5:15 PM - F2.8
Thermal and Photo-Induced Phase Transformations ofSilver(I)-2-[2-(2-methoxyethoxy)-ethoxy]acetat.
Alexander Jakob 1 , Stephan Jahn 2 , Afshin Abbasi 3 , Thomas Blaudeck 2 , Cameliu Himcinschi 4 , Marion Friedrich 4 , Heinrich Lang 1 , Reinhard Baumann 2 , Michael Schreiber 3 , Dietrich R. T. Zahn 4
1 Inorganic Chemistry, TU Chemnitz, Chemnitz Germany, 2 Print and Media Technology, TU Chemnitz, Chemnitz Germany, 3 Theory of Disordered Systems, TU Chemnitz, Chemnitz Germany, 4 Semiconductor Physics, TU Chemnitz, Chemnitz Germany
Show AbstractSilver(I)-complexes and derivatives can serve as precursors for the metallization of various materials used in contemporary microelectonics [1], as the metallization process mainly comprises a spin-on deposition of the dissolved precursor on the substrate followed by a subsequent thermal treatment. However, for most flexible substrates used in organic and large-area electronics, the metallization is a severe challenge as the respective approaches have to cope with the limited thermal stability of the materials in use. We report on silver(I)-2-[2-(2-methoxyethoxy)-ethoxy]acetat (usually known for thermographic and photothermic imaging) as a suitable precursor molecule for a photo-induced metallization of substrates with limited stability. Comparative monitoring of thermal and photo-induced transformation processes by conductance measurements, Raman and Fourier transform infrared (FTIR) spectroscopy along with density functional theory (DFT) calculations indicates that the formation of metallic layers from the wet-deposited films comprises at least two solid-state phase transformations. Our experiments complement the studies by Olson et al. which discuss the subsequent formation of metallic silver nanoparticles and micro-islands during the thermally induced reduction of silver carboxylates [2].The knowledge on the physical and chemical details of the transformation process may pave the way for a replacement of the thermal treatment by alternative techniques suitable for substrates with low thermal stability such as poly(ethylene terephthalate) (PET).
5:30 PM - F2.9
Solution Processed Silver Sulfide Filament Memories.
Shong Yin 1 , Vivek Subramanian 1
1 Electrical Engineering, UC Berkeley, Berkeley, California, United States
Show AbstractIonic resistive switches are emerging as a potential successor for flash in non-volatile memory applications. In ionic switches, metal cations migrate through a solid electrolyte forming filaments on an inert cathode that results in an abrupt increase in conductivity. This process is reversible, and the switches may be reverted to a low-conductive state. These switches have low transition voltages and fast read speed. The low switching energy potentially makes them more scalable than many other resistive memories. Silver Sulfide Resistive switches have been fabricated by sulfidizing evaporated silver films in Sulfur solutions. XPS is used to quantify stoichiometry of resultant films. SEM and AFM indicate that surface roughness increases with sulfidation time as the bulk silver film is consumed in forming the silver sulfide. XRD has confirmed presence of the acanthite phase of Silver Sulfide in the films. The entire process is performed at temperatures below 200C, so the devices are potentially stackable over conventional CMOS substrates in a BEOL process, and are applicable to printable electronics on plastic substrates. Initial characteristics measured on these cells are very promising, exhibiting low energy switching and good programming margins. Write/Erase voltages for cells were 400mV and -200mV respectively. Ron/Roff ratios range from 10 to 10,000 depending on process conditions. Impact of bath concentration, bath temperature and post-annealing on the silver sulfide film structure and ionic conducting properties are studied.
5:45 PM - F2.10
Microfabrication using UV Photo-patternable Semiconductor Nanocrystals.
Won Jin Kim 1 , Sung Jin Kim 1 2 , Marek Samoc 1 , Alexander Cartwright 1 2 , Paras Prasad 1 2 3
1 Institute for Lasers, Photonics and Biophotonics, University at Buffalo, State University of New York, Buffalo, New York, United States, 2 Electrical Engineering, University at Buffalo, State University of New York, Buffalo, New York, United States, 3 Chemistry, University at Buffalo, State University of New York, Buffalo, New York, United States
Show AbstractF3: Poster Session: Nano and Electronic Devices
Session Chairs
Wednesday AM, December 03, 2008
Exhibition Hall D (Hynes)
9:00 PM - F3.1
Monolayer Film of Gold Nanoparticles on a 3 inch or Larger Silicon Wafer.
Matthew Martin 1 , Sang-Kee Eah 1
1 Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractWe report a very easy, simple, and cheap fabrication method for depositing a monolayer film of gold nanoparticles on any substrate without any size limitation. We present a hexagonal close-packed monolayer of 7 nm gold nanoparticles on a 3 inch silicon wafer. For this purpose we have been developing a new method for chemical synthesis of 3-7 nm gold nanoparticles coated with organic molecules with a special property of floating at the air-toluene interface of a toluene droplet. There they form a hexagonal close-packed monolayer, which can be deposited to any substrate after the toluene molecules' evaporation. There is no size limitation, since a toluene droplet can be as large as 3 inches or larger covering the whole surface of a substrate like a silicon wafer.We chemically synthesize gold nanoparticles in water by mixing an aqueous solution of H+, AuCl4-, and Cl- with an aqueous solution of OH-, BH4-, and Na+. By mixing the two solutions as uniformly and quickly as possible, we can make nearly monodisperse gold particles in water in the diameter range of 3-7 nm. These gold nanoparticles are phase transferred to hexane with 1-dodecanethiol (DDT) molecules simply by vigorous shaking for 1 minute. During the shaking, DDT molecules coat gold nanoparticles and extract them from the water phase to the hexane phase. We found out that these gold nanoparticles coated with hydrophobic organic molecules are negatively charged in a non-polar solvent, hexane. They are stable in hexane but unstable in toluene. If we mix a droplet of hexane containing these gold nanoparticles with a toluene droplet, the gold nanoparticles float at the air-toluene interface as the hexane molecules evaporate 4 times faster than the toluene molecules.In this two-dimensional (2D) self-assembly the purity of the gold nanoparticles solution is very important, because all the non-volatile impurities remain on the substrate after the evaporation of the volatile solvent molecules. Bigioni et al. [1] reported a similar 2D self-assembly method for gold nanoparticles, where they emphasize the importance of the excess DDT molecules and propose the mechanism of their 2D self-assembly as the organic surfactant molecules cover the interface and ‘attract’ gold nanoparticles. Therefore the monolayer film of gold nanoparticles contains a lot of DDT molecules beneath or above the gold nanoparticles monolayer. In our case the gold nanoparticles solution in hexane is very clean with the only impurity of excess DDT molecules, which can be precisely controlled during the chemical synthesis. All the reaction byproducts remain in the water phase. We present results related to the effects of excess DDT molecules on the quality of the gold nanoparticles monolayer, such as the presence of regions without gold nanoparticles.[1] T.P. Bigioni, X.-M. Lin, T.T. Nguyen, E.I. Corwin, T.A. Witten, & H.M. Jaeger, Nature Mater. 5, 265–270 (2006).
9:00 PM - F3.10
Optimization of Inkjet Printed CdSe/ZnS Quantum Dot Packing via Bifunctional Self-Assembled Monolayer.
Hanna Haverinen 1 2 , Andrew Wang 3 , Risto Myllyla 2 , Ghassan Jabbour 1 2 4
1 , Flexible Display Center at Arizona State University, Tempe, Arizona, United States, 2 , University of Oulu, Oulu Finland, 3 , Ocean Nanotech, Fayetteville, Arkansas, United States, 4 , Advanced Photovoltaics Center, Tempe, Arizona, United States
Show Abstract9:00 PM - F3.11
An Evaporative Co-assembly Method for Highly-Ordered Inverse Opal Films.
Benjamin Hatton 1 , Lidiya Mishchenko 1 , Joanna Aizenberg 1
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - F3.13
Stable Binary Complementary White Light Emitting Diodes based on Quantum Dot/Polymer Bilayer Structures.
Zhanao Tan 1 , Brittany Hedrick 1 , Fan Zhang 1 , Ting Zhu 1 , Shuai Gao 1 , Jian Xu 1 , Ron Henderson 2
1 Department of Engineering Science and Mechanics, Penn State University, University Park, Pennsylvania, United States, 2 Department of Physics, Middle Tennessee State University, Murfreesboro, Tennessee, United States
Show AbstractA binary complementary white light-emitting-diode (LED) was designed and fabricated by employing a colloidal quantum-dot (QD)/polymer-bilayer configuration in the device active region. Stable white electroluminescence was observed from the fabricated device, arising from the additive mixture of the emission from the yellow-emitting CdSe/ZnS core-shell QDs and blue-emitting poly(N,N’-bis (4-butylphenyl)- N,N’-bis(phenyl)benzidine) (Poly-TPD) molecules. The white chromaticity of the LED output can be tailored by varying the respective thicknesses of the constituent emissive layers; whereas the emission color exhibits little dependence on the applied bias over a wide voltage rang. The maximum luminance of the device reaches 2600 cd/m2 under a bias of 9.4 V.
9:00 PM - F3.14
Ultraviolet Ozone Sintering of Pd Nanoparticles.
Liwei Huang 1 2 , Yayong Liu 1 , Howard Wang 1 2 , Sushil Satija 2 , Bulent Akgun 2
1 Mechanical Engineering, Binghamton University, Binghamton, New York, United States, 2 NCNR, National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show Abstract9:00 PM - F3.15
Fabrication of PLZT Film-on-Foil Dielectric Sheets for Embedded Passives.
Beihai Ma 1 , Manoj Narayanan 1 , U. (Balu) Balachandran 1
1 Energy Systems Division, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractFerroelectric film-on-foil capacitors hold special promise to replace discrete passive components in the development of electronic devices that require greater performance and smaller size. High permittivity ferroelectric thin films were deposited on base metal foils by chemical solution deposition to form film-on-foil capacitor sheets. These capacitors can be embedded into printed circuit boards (PCBs). However, the formation of a parasitic low permittivity interfacial oxide layer during thermal processing of the ferroelectric significantly reduces the capacitance density. Two approaches were taken to overcome this challenge. In the first, a conductive oxide buffer layer acting as a bottom electrode is inserted between the ferroelectric and the metal foil to obviate the deleterious interfacial oxide. In the second, the high temperature processing is done under low oxygen partial pressures such that no interfacial oxide is formed. We have grown high quality ferroelectric (Pb,La)(Ti,Zr)O3 thin films on Ni and Cu foils. Relative permittivity ≈1300 and dielectric loss (tan δ) ≈0.05, leakage current density of 6.6×10-9 A/cm2, and mean breakdown field strength >2.4×106 V/cm were measured. Based on their high-field hysteresis loops, an energy density of ≈17 J/cm3 can be stored in such a capacitor at one half of its mean breakdown field. Details of processing conditions, dielectric properties, and breakdown strength will be presented.Work was supported by the U.S. Department of Energy, Office of FreedomCAR and Vehicles Technology Program, under Contract DE-AC02-06CH11357.
9:00 PM - F3.16
Investigation of the Adhesion of Electroless Copper to Glass Substrates.
Xiaoyun Cui 1 , David Hutt 1 , Paul Conway 1
1 Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Leicestershire United Kingdom
Show AbstractCurrently, device interconnect technology is being greatly improved to produce the next-generation high-density and high speed integrated circuits. However, the fabrication of matching printed circuit boards (substrates) results in manufacturing difficulties due to the reduction in metal line widths and pitches. Thin glass is a potential alternative material to manufacture multilayer substrates for flip-chip devices, instead of the traditional FR4, as it offers good dimensional stability and coefficient of thermal expansion similar to silicon. In addition, the transparency of glass makes it suitable for carrying optical signals and enables the alignment of electrical interconnects. Metallisation is a key step in the elaboration of multilayer substrates for flip-chip assembly built up from thin (100μm) glass sheets. Electroless copper deposition is an attractive method due to its relatively low cost and potential for high volume production. However, metallising the glass using electroless methods to prepare electrically conductive tracks, with sufficient thickness for solder interconnect, is challenging due to the need to activate the surface to achieve good adhesion of the copper coating which is critical for the reliability of the device. In this work, (3-aminopropyl)-trimethoxysilane (APTS) was used to pre-treat the glass, which was subsequently activated with a Pd/Sn catalyst followed by electroless copper deposition. The influence of the deposition process on the adhesion was investigated qualitatively using standard tape tests. The APTS solution and catalyst immersion times, electroless bath temperature and pH value were all controlled in order to establish the treatment parameters that enabled uniform copper deposition. In general, it was found that the APTS pre-treatment was necessary to assist in the attachment of the catalyst. Adhesion of the copper varied with catalyst immersion time: short or extended catalyst immersion times led to lower adhesion. In addition, thin copper coatings adhered well to the glass, but for layers thicker than 160 nm tape tests removed large areas. To identify the locus of failure, the fracture surfaces of copper layers peeled off the glass were examined by X-ray Photoelectron Spectroscopy (XPS) and SEM which indicated that the failure occurred between the copper and catalyst. The surface of the glass was analysed at each stage of the deposition process with particular emphasis on the influence of catalyst immersion time using XPS and Time-of-Flight Secondary Ion Mass Spectrometry. The XPS core level peaks of Pd showed that Pd(0) became stronger than Pd(II) with increasing immersion time. The presence of Pd(II) with short catalyst immersion time was indicative of PdCl2 left as residual reactant. Meanwhile, field emission SEM and atomic force microscopy were used to characterize the glass surface and Cu film structure at different stages of the deposition process for different preparation conditions.
9:00 PM - F3.17
Solution-deposited Low Voltage Zinc Oxide Transistors Using Sol-gel-derived Sodium beta-Alumina (Superionic Conductor) as Gate Dielectric.
Bhola Pal 1 , Howard Katz 1
1 Material Sc. And Engineering, Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractSodium beta-Alumina (SBA) is a layered crystal that exhibits very high ionic conductivity in two dimensions. The ionic conductivity of SBA is due to the motion of sodium ions in lattice planes, which are separated by a distance of 11.3 Å. Between the planes there are non-conducting spinel-like blocks of Al and O ions. This kind of SBA crystal can be synthesized by sol-gel methods and subsequent heat treatment. A film of SAB can provide very high capacitance due to its highly conducting Na+ ion; while causing negligible leakage current due to the lack of electron carriers inside the crystal. A typical 70-nm-thickness SBA film has a capacitance of 300 nF/cm2. We have used this kind of film as a gate insulator for a solution-deposited n-channel ZnO field effect transistor. The film was fabricated by simple dip coating and subsequent heat treatment of a zinc acetate film. The resulting transistor needs only few volts to give considerably high drain current. The maximum field effect mobility of electrons achieved by this method is 1.0 cm2/Vs with On/Off ratio of 102.
9:00 PM - F3.18
Optimization of Solvent Casting Process of Ge23Sb7S70 Thin Films.
Shanshan Song 1 2 , Nathan Carlie 3 , Laeticia Petit 3 , Kathleen Richardson 3 , Craig Arnold 1 2 4
1 Department of Electrical Engineering, Princeton University, Princeton, New Jersey, United States, 2 Princeton Institute for the Science and Technology of Matierials, Princeton University, Princeton, New Jersey, United States, 3 Advanced Materials Research Laboratory, Clemson University, Anderson, South Carolina, United States, 4 Department of Mechanical & Aerospace Engineering, Princeton University, Princeton, New Jersey, United States
Show AbstractChalcogenide glasses are important low-loss mid-infrared materials, and exhibit a wide range of photo-induced phenomena and optical nonlinearities. In particular, Ge-Sb-S films have drawn attention for their high nonlinear optical properties and compositional dependencies of various optical and structural properties. In this study, we demonstrate and optimize the preparation of Ge23Sb7S70 chalcogenide thin films by solvent-casting and spin-coating techniques from liquid solutions. Four different solvents (potassium hydroxide, ammonium hydroxide, propylamine and butylamine) are tested and the dissolution kinetics of Ge23Sb7S70 and As40S60 in these solutions is studied and explained. Thin films of Ge23Sb7S70 glass are spin-coated and heat-treated under different conditions with amine-based solutions which are found to produce films with the most consistent film compositions. The film deposition process is optimized by examining the effects of the solvent, the glass to solvent ratio, the time elapsed during dissolution on the film composition, the effects of spin speed and of the annealing heat treatment on the composition of the thin film, the thickness and optical properties homogeneity over a microscope slide scale, and the effects of processing atmosphere (in air vs. inside a nitrogen-purged glove box). The film quality is examined by energy-dispersive x-ray spectroscopy (EDS), optical spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and Zygo optical profilometry. When deposited using the optimal parameters, the film is found to have a composition similar to the bulk glass and a surface roughness around 5 nm. The optical properties of the films, including refractive index and optical band gap, are found to be closely related to heat treatment conditions.
9:00 PM - F3.19
Langmuir-Blodgett Assembly of Graphite Oxide Single Layers.
Jiaxing Huang 1 , Laura Cote 1 , Franklin Kim 1
1 Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractSingle layer graphite oxide is a model system for studying two dimensional membranes and has recently been recognized as a promising material for composite and electronics applications. For both the fundamental understanding of soft membrane properties and the practical applications of GO based materials, especially in a form of thin films, it is important to know how these atomically thin sheets assemble and how they interact with each other, e.g., edge-to-edge and face-to-face. Such assembly behavior can be studied using Langmuir-Blodgett technique. In addition, 2D tiling of flat graphite oxide single layers can be achieved over large areas with continuously tunable packing densities.
9:00 PM - F3.2
Highly Efficient Green Quantum Dot Based Light-Emitting Diodes.
Jeonghun Kwak 1 , Wan Ki Bae 2 3 , Seonghoon Lee 3 , Kookheon Char 2 , Changhee Lee 1
1 School of Electrical Engineering & Computer Science and Inter-university Semiconductor Research Center, Seoul National University, Seoul Korea (the Republic of), 2 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of), 3 School of Chemistry, Seoul National University, Seoul Korea (the Republic of)
Show AbstractQuantum dot based light-emitting diodes (QLEDs) have been investigated for several years as one of the most promising candidates for next-generation display and lighting, because colloidal nanocrystal quantum dots (QDs) have unique optical properties such as high color purity with narrow emission spectra, easy control in emission wavelength by their size, and superior luminescence efficiency in solid state compared with conjugated polymers or organic molecules. Although much progress in QLEDs have been made by controlling QD structures or optimizing device structures, QLED devices (particularly in green or blue emitting region) still suffer from low efficiency, low brightness and low color purity.In this work, we report color-saturated green QLEDs with a high efficiency of 5.2 cd/A and high color purity (above 99 % of total emission from QDs). Green QLEDs with different emission wavelengths (peak at 510 nm, 524 nm, 542 nm) were fabricated with the device structure of ITO / PEDOT:PSS / poly-(N,N’-bis(4-butylphenyl)-N,N’-bis(phenyl)benzidine) (poly-TPD) / QDs / 1,3,5-tris(N-phenylbenzimidazol-2,yl) benzene (TPBI) / LiF / Al. They showed excellent performances such as low turn on voltage (3.5 V), the maximum brightness above 10,000 cd/m2, and narrow spectral bandwidth (FHWM < 30 nm) without parasitic emission originating from the organic layers proximal to the QD layer (i.e., poly-TPD or TPBI). We attribute these performances to the chemical composition gradient structure of QDs as well as the uniform and high surface coverage of the QD layer.
9:00 PM - F3.20
Polycrystalline Thin Film FeS2 Pyrite Produced via Post Deposition Anneal of Spin Coated Iron Hydroxo-nitrate and Hydroxo-oxalate.
Heather Platt 1 , Stephen Meyers 1 , Jeremy Anderson 1 , Douglas Keszler 1
1 Chemistry, Oregon State University, Corvallis, Oregon, United States
Show AbstractFeS2 pyrite is a moderate band gap semiconductor with an optical absorption coefficient on the order of 105 cm-1. These properties, along with the low cost and benign nature of the constituent elements, make it an attractive candidate for the absorber layer of a solar cell. Small open circuit voltages obtained from thin films have limited development, however. To examine the prospects for production of high quality polycrystalline FeS2 films, we have deposited smooth amorphous iron hydroxo-nitrate and hydroxo-oxalate films from unique aqueous precursors and converted them under flowing H2S(g). In this contribution, we describe the deposition methodology and optical, electrical, and morphological characterization of the resulting FeS2 pyrite films.
9:00 PM - F3.21
Microstructure Dependence of Liquid-Phase Deposited SiO2 Films on Solution Parameters.
Shijun Yu 1 , Junghyun Cho 1
1 Dept. of Mechanical Engineering & Materials Science and Engineering Program, State University of New York (SUNY) at Binghamton, Binghamton, New York, United States
Show AbstractThe advantage of near room temperature processes and self-fluorinated characteristics makes liquid-phase deposited SiO2 films as a promising interlayer dielectric. Several research groups reported inconsistent results for SiO2 deposition rates with boric acid addition to the precursor solution, but little work has focused on microstructure differences. In this study, using a supersaturated hydrofluosilicic acid (H2SiF6) aqueous solution ranging from 0.5M to 2M, a series of SiO2 films were deposited both on FTO-coated glass and piranha pretreated silicon, with controllable thicknesses between 50 nm and 1 um. It was observed that these films change from very smooth surface to particle agglomerated porous morphologies as the concentration of boric acid in the solution increases. In parallel, the effect of H2SiF6 concentration and solution temperature on film microstructures was also explored. One goal of this study is to identify an underlying mechanism that can explain the thin film formation involving nucleation, growth, and agglomeration of the SiO2 nanoparticles. Furthermore, the effect of deposition conditions on the porosity and the fluorine content in the films and their influence on dielectric performance are investigated.
9:00 PM - F3.22
Flexible Complementary Inverters Based on Solution-processable Inorganic Nanocrystals.
Jaewon Jang 1 , Junggwon Yun 1 , Kyoungah Cho 1 , Byoungjun Park 1 , Sangsig Kim 1
1 , Korea University, Seoul Korea (the Republic of)
Show AbstractComplementary inverters were fabricated on flexible plastic substrates using solution-based bottom-up strategies. A complementary inverter was constructed with an p-channel HgTe nanocrystal (NC)-based thin film transistor (TFT) used as the load and a n-channel HgSe NC-based TFT used as the driver. The load TFT exhibited a field effect mobility of 0.7 cm2/Vs and an on/off current ratio of ~103. On the other hand, the driver TFT possessed a field effect mobility of 4.0 cm2/Vs and an on/off current ratio of ~102. The fabricated device acted as a typical inverter with the high output state which was over 90% of the full voltages at a low input voltage of 0 V and the low state at a high input voltage of + 5 V. The complementary inverters possessed logic gains of 12~18, a logic swing of 90% and a noise margin (NM) of 2.5 V corresponding to 0~5 V input voltages. The effect of bending strain on electrical characteristics of the complementary inverters was also investigated. The tensile or compressive strain of 0.2% did not affect the electrical characteristics of our devices. When the substrate was subjected to a tensile or compressive strain of 0.7%, the representative complementary inverter revealed the gains of 11~13 and 15~19 at VDD of +15 V and +20 V, respectively. In spite of external tensile or compressive strain, it still showed a high logic swing over 90% and a NM of 2.5 V.
9:00 PM - F3.23
Low-temperature Growth of Uniform ZnO Particle with Controllable Morphologies.
Ming Da Yang 1 , Mean Jue Tung 1
1 , Industrial Technology Research Institute, Hsinchu, Taiwan Taiwan
Show Abstract9:00 PM - F3.24
Magnetic and Metallic Nanoparticle Arrays Prepared Through Spin Casting.
Joseph Tracy 1 , Aaron Johnston-Peck 1 , Junwei Wang 1
1 Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractSpin casting is an economical method for depositing monolayer and multilayer arrays of ligand-protected nanoparticles (NPs) formed through self-assembly. We have investigated the self-assembly process during spin casting by varying different parameters, including substrate functionalization, solvents, spin speeds, concentrations, and core sizes of metallic (Au) and magnetic (FePt and Ni) NPs. The local ordering, defects, and grain boundaries in these NP arrays have been characterized using electron microscopy. We will also report optical measurements for assessing surface plasmon resonance coupling in arrays of Au NPs and magnetic characterization of dipolar coupling in arrays of magnetic NPs.
9:00 PM - F3.25
Trade-off Between Permittivity and Reliability in BaTiO3-Based Thin Film Capacitors.
Song Won Ko 1 , Clive Randall 1 , Susan Trolier-McKinstry 1 , Michael Randall 2 , Tony Kinard 2 , Uwe Meier 2 , Philip Lessner 2
1 , Pennsylvania State University, University Park, Pennsylvania, United States, 2 , KEMET Electronics Corporation, Simpsonville, South Carolina, United States
Show Abstract9:00 PM - F3.26
Preparation of Smooth Zinc Oxide Thin Film via Liquid Phase Reaction with Cation Additives.
Takeyasu Saito 1 , Yoshihisa Hirata 1 , Naoki Okamoto 1 , Kazuo Kondo 1
1 Chemical engineering, Osaka Prefecture University, Sakai Japan
Show AbstractZinc oxide (ZnO) is a very attractive material as transparent, cheap, stabile semiconductor as well as conductive layers. ZnO films are generally synthesized by dry methods like chemical vapor deposition, sputtering and pulsed laser deposition. However, thin films fabrication from liquid phase could offer a lot of advantages such as simplicity, low cost, large area growth and high throughput. In this study, the effects of positive ions in a solution such as Mg, Ga and Al on film morphology and crystallographic structure were investigated. Slide glass (76mm×26mm×1t), the Si (100) (10mm sq.) and Si (100) with 1um-thick thermal oxide (10mm sq.) were employed as substrates. Nucleation procedures were carried out by dipping in the solutions, SnCl2: 0.1 mol/l → AgCl: 0.1 mol/l → PdCl2: 0.1 mol/l for 10 minutes each. The substrates were hold in a solution of Zn(NO3)2: 0.1 mol/l and dimethylamine-borane (DMAB): 1E-2 to 0.1 mol/l in a range of 60-80°C for four hours. Mg(NO3)2, Ga(NO3)3 or Al(NO3)3 in a range from 1E-4 to 5E-2 mol/l were added as a cation source. Surface and cross-section of ZnO films were observed by FE-SEM and crystallographic structure was determined by X-ray diffraction. The dependency of the DMAB concentration and reaction temperature was investigated and a solution with Zn(NO3)2: 0.1 mol/l and DMAB: 0.05 at 70°C was found to be suitable for continuous film growth with hexagonal ZnO structure, where the growth rate was 0.13um/h. This condition was set as the standard to investigate the effects of cation additives. In the case of Al(NO3)3: 1E-2 mol/l addition, the formation of continuous films was recognized, however the peak of ZnO is not detected, which suggests that the films is amorphous or microcrystalline and that the Al ion beyond a certain amount results in obstructing crystallization of ZnO. On the other hand, a strong peak of ZnO could be recognized when Al(NO3)3 concentration was equal to or less than 1E-3 mol/l, and also the film surface became flat possibly due to the increase of the nucleation density. In the case of Ga(NO3)3 addition, the trend was almost the same compared with the Al(NO3)3 addition except the surface flatness. In the case of Mg(NO3)2 addition, a peak of ZnO was recognized in all the concentration studied here and surface morphology did not change. Compared with the cases with 1E-4 mol/l cation additition, the growth rates with Mg, Ga and Al addition were 0.13um/h, 0.38um/h and 0.35um/h., respectively. The growth rate was enhanced by 1E-4 mol/l of Ga or Al addition. In summary, a solution with Zn(NO3)2: 0.1 mol/l and DMAB: 0.05 at 70°C offered continuous and hexagonal ZnO thin films with the growth rate of 0.13um/h. By adding 1E-4 mol/l of Ga or Al, the growth rate became three times compared with the case without cation and particularly the surface morphology became flat in the case of Al.
9:00 PM - F3.27
CaBi4Ti4O15 Thin Film Deposition on Electroplated Platinum Substrates using a Sol-gel Method.
Takeyasu Saito 1 , Yuichiro Hirota 1 , Naoki Okamoto 1 , Kazuo Kondo 1 , Takeshi Yoshimura 2 , Norifumi Fujimura 2
1 Chemical engineering, Osaka Prefecture University, Sakai Japan, 2 Physics and Electronics , Osaka Prefecture University , Sakai Japan
Show AbstractFerroelectric random access memory (FeRAM) has drawn great attention as one of promising nonvolatile, low operating power, high write speed, and high write endurance device candidates. However, 3-D capacitor-integration technology for larger memory size as well as more robust materials without lead for high temperature operation are the recent important issue. In this work, CaBi4Ti4O15 growth on different Platinum substrates was carried out through a sol-gel method. The effects of crystallization procedures, bismuth concentration on surface morphology and crystallographic structure were investigated. Each of Ca, Bi, Ti containing solution (0.5M/l, Kojyundo Chemical Co, Japan) was employed as a metal source. Three kinds of Pt substrates were used. The first one is the highly oriented sputtered Pt(111) (200nm) substrates without Pt(200) orientation, the second is the sputtered Pt with weak Pt(200) orientation and the third is electroplated Pt (500nm) substrates on sputtered Pt with weak Pt(200) orientation. The ratio of Ca, Bi and Ti was 1, 4 and 4 or 1, 4.8 and 4. The mixed solutions were spin-coated on substrates, followed by a drying process at 120°C for 2 min. The calcination was carried out at 300-400°C for 10 min and then rapid thermal annealing (RTA) at 650-800°C for 10 min was also done in ambient atmosphere. The surface of film was observed by FE-SEM and the crystallographic structure was determined by an X-ray diffraction. Both RTA temperature and excess amount of Bi have an effect on the surface morphology and crystallographic structure. Higher RTA temperature up to 800°C decreased Pyrochlore contents in the films and 20% excess amount of Bi also decreased the contents. The crystalline diameter measured by FE-SEM became larger with increasing RTA temperature from 650-750°C and then remained almost the same at 750 and 800°C. CaBi4Ti4O15 crystallographic structure grown on the highly oriented sputtered Pt(111) substrates has a strong (119) peak and it was the main. However, CaBi4Ti4O15 crystallographic structure on sputtered Pt with weak Pt(200) orientation and that on electroplated Pt (500nm) substrates has several peaks ascribed to c-axis orientation. The reasons for the difference are now under study. In summary, higher RTA temperature and 20% excess amount of Bi decreased Pyrochlore contents in the deposited films. C-axis oriented CaBi4Ti4O15 thin film could be grown on platinum substrates with weak Pt(200) orientation.
9:00 PM - F3.3
Electrophoretic Deposition: An Effective Technique for the Production of Transparent and Luminescent Films of Rare-Earth Sesquioxide (RE2O3) Nanocrystals.
Sameer Mahajan 1 2 , Justine Hart 3 , James Dickerson 2 3
1 Interdisciplinary Program in Materials Science, Vanderbilt University, Nashville, Tennessee, United States, 2 Vanderbilt Institute of Nanoscale Science and Engineering, Vanderbilt University, Nashville, Tennessee, United States, 3 Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, United States
Show AbstractNumerous solution-based synthesis techniques have been developed to fabricate nanocrystalline structures. Integration of these structures into next-generation devices requires them to be distributed into thin film form via low-cost, high throughput techniques. Electrophoretic deposition (EPD) of nanomaterials offers significant control over the thickness, homogeneity, and site selectivity of the thin film. This approach also provides low-cost and high throughput in the film formation. Here, we report the successful deposition of homogeneous and transparent films of sub-3 nm europium sesquioxide (Eu
2O
3), terbium sesquioxide (Tb
2O
3), and gadolinium sesquioxide (Gd
2O
3:RE
3+) nanocrystals via EPD. Eu
2O
3, Tb
2O
3, and Gd
2O
3:RE
3+ are known for their characteristic red and green emission colors arising from Eu
3+ and Tb
3+ ions, respectively. Such materials and their derivatives can be employed in video displays, luminescent biological tags, and light emitting devices in their film form.
[1]The nanocrystals, employed for the film deposition, were synthesized via hot solution phase method and purified with ethanol prior to deposition.[2] The nanocrystals were dispersed in hexane, which facilitated formation of stable dispersion. The films were deposited from the nanocrystal dispersion in presence of high electric field (~ 2-4 kV/cm). The transparent films of the nanocrystals formed on both of the electrodes, anode and cathode. The film roughness was determined with atomic force microscopy (AFM) and film morphology was investigated using scanning electron microscopy (SEM) and optical microscopy. Energy dispersive spectroscopy (EDS) of the film confirmed film deposition on variety of conductive substrates. Film thickness measurements were performed using profilometry. Optical characterization of films was performed with absorption and photoluminescence spectroscopy.
References[1]S. Shionoya, W. M. Yen, Phosphor Handbook, CRC Press, Boca Raton 1999[2]S. V. Mahajan, J. H. Dickerson, Nanotechnology 2007.
9:00 PM - F3.4
Preparation of Highly Luminescent Semiconductor Nanocrystals and Their Application to Light-Emitting Diodes.
Wan Ki Bae 1 , Jeonghun Kwak 3 , Changhee Lee 3 , Seonghoon Lee 2 , Kookheon Char 1
1 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of), 3 School of Electrical Engineering and Computer Science, Seoul National University, Seoul Korea (the Republic of), 2 School of Chemistry, Seoul National University, Seoul Korea (the Republic of)
Show AbstractGreat efforts have been placed on the preparation of colloidal semiconductor nanocrystals (NCs) not only for fundamental studies in nanoscopic materials but also for their potential applications to light-emitting diodes, photovoltaic devices, and biomarkers. Owing to the recent advances in structural design and synthetic procedure of NCs, huge progress has been achieved for useful applications, particularly in light emitting systems even down to practical levels. However, those achievements in the synthesis and applications of NCs reported so far are mostly limited to red emitting NCs.In this work, we present the synthesis of highly efficient green and blue emitting NCs in reproducible and straightforward manner. For green emitting NCs, CdSe@ZnS structures with chemical composition gradient are designed and prepared by the single-step synthesis based on reactivity difference between Cd and Zn or Se and S precursors. For blue emitting NCs, Cd1-xZnxS@ZnS structures with diffuse interface between the core (Cd1-xZnxS) and the shell (ZnS) phase were realized with the one-pot synthesis method in gram-scale. Both prepared NCs exhibit narrow spectral bandwidth (FHWM < 30 nm), high photoluminescence efficiency (up to 80 %), and photo- and colloidal stability. We also demonstrate highly efficient electroluminescent devices based on NCs (EQE above 1.5 %, maximum luminescence above 10,000 cd/m2).
9:00 PM - F3.5
Photocatalytic Oxidation of Surfactants for the Patterned Deposition of Nanoparticles onto Metal Oxide Surfaces.
David Watson 1 , Gregory Soja 1
1 , University at Buffalo, Buffalo, New York, United States
Show AbstractThe patterned deposition of nanoparticles onto substrate surfaces may enable applications in array-based sensors and electronic, photonic, and magnetic devices. One promising fabrication strategy involves the combination of top-down and bottom-up methods. Techniques such as monolayer photolithography, scanning probe lithography, and microcontact printing are used to produce patterned, monolayer-functionalized surfaces, which serve as templates for nanoparticle adsorption. Top-down patterning imparts long-range order, while bottom-up assembly enables control over the connectivity between nanoparticles and the substrate surface.We have developed a solution-phase photolithographic method for the patterned deposition of metallic and semiconducting nanoparticles onto nanocrystalline TiO2 films. The nanoparticles are adsorbed to TiO2 surfaces through bifunctional mercaptoalkanoic acid (MAA) linkers. The color and optical density of the films are tunable by varying the composition and coverage of surface-adsorbed nanoparticles. The photopatterning mechanism involves the TiO2-catalyzed oxidative degradation of surface-adsorbed MAAs, prior to nanoparticle adsorption. Nanoparticles adsorb only to unilluminated regions of the substrate. Illumination through a photomask, under ambient conditions, yields optically patterned surfaces with diffraction-limited resolution. The high surface area of the nanocrystalline TiO2 substrates enables the adsorption of nanoparticles at high surface coverages, leading to optically dense patterns.This presentation will focus on mechanistic aspects of the monolayer photolithography and self-assembly processes. First, we will discuss the influence of surfactant structure, composition, and functionalization on the assembly of monolayers on metal oxide surfaces. Specifically, we will focus on the influence of intermolecular interactions within monolayers on surface attachment reactions, monolayer composition, and the affinity of metallic and semiconducting nanoparticles for monolayer-functionalized surfaces. Second, we will discuss the influence of surfactant structure and functionalization on the kinetics, mechanism, and efficiency of TiO2-catalyzed photooxidation reactions. Our findings lend insight into the mechanisms of TiO2-catalyzed photochemical reactions and reveal optimal conditions for the solution-phase patterned deposition of nanoparticles onto metal oxide surfaces.
9:00 PM - F3.6
Self Assembly Techniques for Fabrication of Composite Isotropic Optical Negative Index Metamaterials.
Joel Therrien 1 , Alkim Akyurtlu 1 , Aaron Bandremer 2
1 Electrical and Computer Engineering, U. of Massachusetts Lowell, Lowell, Massachusetts, United States, 2 Biomedical Engineering and Biotechnology, U. of Massachusetts at Lowell, Lowell, Massachusetts, United States
Show AbstractTechniques for the fabrication of novel optical metamaterials using synthetic chemistry and biological self assembly will be presented. Recently, a novel low-loss and isotropic negative index metamaterial (NIM) design for the visible regime based on silicon carbide (SiC) spherical nanoparticles embedded inside of a MgB2 host has been developed (A. G. Kussow, et al., Physical Review B, 76, 195123, 1-7, 2007). Design parameters of this material are the sizes and fill factor of the SiC nanoparticles. The latter factor also defines the distance between the SiC nanospheres within the host. The main challenge in making such a material lies in the precise placement of the SiC nanoparticles and the avoidance of nanoparticle clustering. Hence, the main goal of this work is to embed SiC nanoparticles at pre-defined distances in the MgB2 matrix. A well-controlled surface modification of SiC nanoparticles will be used to fabricate the desired material. One approach will be the adaptation of methods for the functionalization of silicon nitride (SiN) using alkenes with double functional groups (A. Arafat, et al., JACS, 126, 8600-8601, 2004). We have investigated a 11-carbon alkene with bromine functional end for incorporation into our NIM. Bromine functionalization was verified by XPS, however, thiol substitution using sodium hydrosulfide was discouraging. A bifunctional polyethylene glycol (PEG) with maleimide and silane groups was subsequently investigated. SiC was functionalized with a thiol group and bonded to the maleimide group of the PEG, while the silane group was bonded to a glass substrate used in NIMs functional testing.We will also report on the progress of using biological self assembly for the placement of SiC nanoparticles. We have used phage display to screen for peptides that bind with specificity to the nanoparticles and glass substrates used in testing (S. Whaley, et al., Nature, 405, 665-668, 2000). M13 phages were genetically engineered to display peptides binding the SiC on one terminus of the M13 and the glass substrate at the other terminus with a defined phage length.Difficulties in fabricating this device include adapting SiN chemistry to SiC, verifying functionalization and engineering M13 phage for the biological self assembly approach. The fabrication methods are evaluated using SEM and AFM to determine particle spacing. Once the desired spacing is obtained, MgB2 will be deposited via sputtering. This process will be repeated for two layers of the MgB2/SiC material to obtain the final NIM design. The material will then be characterized using transmission spectra and XRD.
9:00 PM - F3.7
Deposition of Nanostructured Thin Films by Microreactor-Assisted Chemical Processes.
Seung-Yeol Han 1 , Changho Choi 1 , Ana Putnam 1 , Chih-Heng Tseng 2 , Brian Paul 2 , Si-Ok Ryu 3 , Tae-Jin Lee 3 , Chih-hung Chang 1
1 Chemical Engineering, Oregon State University, Corvallis, Oregon, United States, 2 Industrial and Manufacturing , Oregon State University, Corvallis, Oregon, United States, 3 , Yeungnam University, Daedong, Gyeongsan, Korea (the Republic of)
Show AbstractNanostructured thin films were deposited by microreactor-assisted chemical processes. This technique uses continuous flow microreactors for the synthesis and deposition of nanomaterials. In synthesis, microreactor technology offers large surface-area-to-volume ratios within microchannel structures to accelerate heat and mass transport. This accelerated transport allows for rapid changes in reaction temperatures and concentrations leading to more uniform heating and mixing in the deposition process. Consequently, microreactors have been demonstrated to yield dramatic enhancements in controlling the quantum dot size distributions, thereby minimizing particle size variability. The possibility of synthesizing nanomaterials in the required volumes at the point-of-application eliminates the need to store and transport potentially hazardous materials, while providing new opportunities for tailoring novel nanostructures and nanoshaped features. Microreactors have been found to radically improve cycle times and yields associated with the production of a broad range of materials including both inorganic and organic materials that cover a variety of applications such as dendrimers, functionalized metal nanoclusters, metal oxide semiconductor nanoparticles. In particular, we have used microreactors to dispense reactant streams directly onto moving or stationary substrates to yield nanostructured thin films. Results-to-date demonstrate the possibility to control the reacting flux including small intermediate-reaction molecules, macromolecules, nanoclusters, nanoparticlse, and structured assemble of nanoparticles directly after synthesis. These results also suggest the possibility of producing many types of nanostructured films using low cost solution chemistry. In this paper, we will report various examples of MAND.
9:00 PM - F3.8
Self Organized TiO2 Nanoparticles and SWNT Composite for Gate Dielectric of a Flexible Organic Thin Film Transistor (OTFT).
Himadri Acharya 1 , Jinwoo Sung 1 , Tae Hee Kim 1 , Byung Gil Min 2 , Cheolmin Park 1
1 Department of Materials Science and Engineering, Yonsei University , Seoul Korea (the Republic of), 2 School of Advanced Materials and System Engineeing, Kumho Institute of Technology, Kumi Korea (the Republic of)
Show Abstract9:00 PM - F3.9
Binding Characteristics of Surface Ligands on PbSe QDs and Impact on Conductivity.
Won Jin Kim 1 , Sung Jin Kim 1 2 , Jang Won Seo 1 , Alexander Cartwright 1 2 , Paras Prasad 1 2 3
1 Institute for Lasers, Photonics and Biophotonics, University at Buffalo, State University of New York, Buffalo, New York, United States, 2 Electrical Engineering, University at Buffalo, State University of New York, Buffalo, New York, United States, 3 Chemistry, University at Buffalo, State University of New York, Buffalo, New York, United States
Show Abstract
Symposium Organizers
David B. Mitzi IBM T. J. Watson Research Center
David Ginley National Renewable Energy Laboratory
Bernd Smarsly Justus Liebig University Giessen
Dmitri V. Talapin The University of Chicago
F4: Porous and Structured Films
Session Chairs
Wednesday AM, December 03, 2008
Room 208 (Hynes)
9:30 AM - **F4.1
Evaporation Induced Self-Assembly of Porous and Composite Nanostructures.
C. Jeffrey Brinker 1 2
1 Self-Assembly Department, Sandia National Laboratory/UNM, Albuquerque, New Mexico, United States, 2 Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico, United States
Show Abstract10:00 AM - F4.2
Free-standing and Patternable Monolayer Nanoparticle/polymer Arrays Formed by Evaporation Induced Self-assembly at a Fluid Interface.
Shisheng Xiong 1 , Jiebin Pang 1 , Darren Dunphy 1 , Jeffrey Brinker 1 2
1 Department of Chemical Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 2 Advanced Material Laboratory, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractOrdered nanoparticle (NP) monolayers are of fundamental interest as 2D artificial solids in which electronic, magnetic, and optical properties can be tuned through electron charging and quantum confinement of individual NPs mediated by coupling interactions with neighboring NPs. Recently, we have developed a universal, fast and facile method to prepare robust and transferable monolayer nanoparticle arrays by evaporation-induced self-assembly at a fluid interface (JACS 2008). As-synthesized hydrophobic NPs were assembled on a water interface from toluene containing polymethylmethacrylate (PMMA). In this case solvent evaporation concentrates the thinning film in NPs and PMMA, leading to NP self assembly and solidification into an ordered NP/polymer nanocomposite monolayer with physical dimensions of up to 10 cm2. The NP/PMMA monolayer can be transferred to arbitrary substrates and remains stable as a freestanding membrane suspended over cm-sized holes-even with free edges. Moreover, the PMMA serves as a photoresist enabling two modes of electron beam (e-beam) NP patterning. In combination these extensions contribute to the ability to integrate NP arrays into robust micro- and macroscale devices. Au NP/PMMA and CdSe QD/PMMA films transferred to glass slides or silicon wafers have been characterized with UV-vis spectroscopy and photoluminescence spectroscopy, respectively. The electron transport behavior of Au NP arrays with PMMA dielectric spacers is under investigation.
10:15 AM - F4.3
Formation of Controlled Alumina Films using Deposition in Supercritical Fluids for Electronic and Telecommunication Devices.
Cyril Aymonier 1 2 , Mélanie Majimel 1 2 , François Cansell 1 2 , Catherine Elissalde 1 , Mario Maglione 1 , Jean-François Sylvain 1 , Jean-Marc Heintz 1
1 ICMCB-Supercritical Fluids, CNRS, Pessac Cedex France, 2 ICMCB-ENSCPB-Supercritical Fluids, Université de Bordeaux, Pessac Cedex France
Show Abstract Alumina is the most widely used oxide ceramic material for many applications in electronics, aeronautics, high temperature metallurgy or biomedicine thanks to its interesting mechanical, thermal, electrical and chemical properties [1]. Even if it is a well known system, it remains challenges, especially the one for obtaining dense nanostructured alumina-based ceramics at low temperatures. We recently showed that the sintering of alumina can be optimized by playing on the cristallinity and structure of the initial material [2]. This can be controlled with the elaboration in different sub- and supercritical media: the transformation of Al(acac)3 precursor in a supercritical CO2/EtOH mixture leads to the synthesis of an amorphous alumina and in a subcritical H2O/EtOH mixture to boehmite. This works has highlighted a decrease of the sintering temperature by using the amorphous alumina powder as starting material in comparison with the use of the boehmite starting powder. This very interesting result can then be applied to the deposition of alumina layers on different kinds of particles or substrates, as an alternative deposition method to CVD or still ALD [3]. We propose to focus this presentation on the chemistry in supercritical fluids applied to the controlled deposition of alumina films on two kinds of substrates:- i) on copper plates used as heat sinks in electronics [4]: in this system, alumina represents a good compromise between thermal conductivity and electrical insulation. The challenge is to form dense alumina films below the melting temperature of copper,- ii) on ferroelectric nanoparticles used as powder for ceramics capacitor in telecommunications [5]: the core@shell nanoparticles act as nanobricks to build new nanostructured composite ceramics keeping interesting dielectric properties (high permittivity and low losses). We will discuss the influence of the main operating parameters of the supercritical fluid chemical deposition process, especially the influence of reaction media, on the characteristics of the alumina film (micro/nanostructure, thickness, interface properties …). We will also present the properties of the obtained devices.References:[1] E. Dörre and H. Hübner, Alumina – Processing, properties and applications, Springer-Verlag, Berlin, 1984[2] C. Bousquet, C. Elissalde, C. Aymonier, M. Maglione, F. Cansell, J.M. Heintz, Tunability of Al2O3 crystallinity using supercritical fluid media: effect on sintering, J. Eur. Ceram. Soc., 2008, 28, 223-228.[3] C. Aymonier, A. Loppinet-Serani, H. Reverón, Y. Garrabos, F. Cansell, Review of Supercritical Fluids in Inorganic Materials Science, J. Supercrit. Fluids, 2006, 38, 242-251.[4] P.M. Geffroy, D. Mathias, J.F. Silvain, Heat sink material selection in electronic devices by computational approach, Advanced Engineering Materials, 2008, 10 (4), 400-405[5] C. Bousquet, F. Cansell, C. Elissalde, M. Maglione, C. Aymonier, manuscript in preparation.
10:30 AM - **F4.4
Synthesis of Nanostructured ZnO Thin Films via Low Temperature Aqueous Deposition.
Yun-Ju Lee 1 , David Scrymgeour 1 , Dana Olson 2 , Matthew Lloyd 1 , Erik Spoerke 1 , James Voigt 1 , Julia Hsu 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , National Renewable Energy Laboratory, Golden, Colorado, United States
Show AbstractSingle crystalline ZnO nanorod arrays (NRAs) represent promising nanostructures for electronic and photonic devices due to properties such as excellent electron mobility, high exciton binding energy, and large area, low temperature fabrication. In the last several years, we have demonstrated the synthesis of ZnO NRAs with highly tunable morphologies and properties using controlled precipitation of ZnO from aqueous solutions. In this talk, I describe the synthesis of various nanostructured thin films based on ZnO NRAs and demonstrate their potential applications in photovoltaics and photonics. First, by changing the seeding and NRA growth parameters, the alignment and dimensions of the ZnO nanorods are systematically varied. Such changes in NRA morphology correlate strongly to differences in the current-voltage response and power conversion efficiency of hybrid conjugated polymer-ZnO NRA photovoltaic devices. Second, with the addition of organic growth modifier, the degree of nanorod tip tapering can be carefully tuned. The resulting textured films with graduated refractive index profiles demonstrate broadband antireflection response in good agreement with theoretical models. Third, the surface of ZnO NRAs is modified after synthesis with conformal coatings of thin inorganic films such as TiOx, which affect open-circuit voltage in solar cells by decreasing carrier recombination. Finally, using codeposition of Zn and appropriate dopant ions in aqueous solution, ZnO NRAs with controlled dopant incorporation are demonstrated. These doped NRAs exhibit changes in electrical properties consistent with dopant type and concentration, and may prove useful in a variety of applications. Other modifications in the morphology and properties of nanostructured thin films based on ZnO NRAs will also be discussed.This project is financially supported by the LDRD program at Sandia National Laboratories. 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.
11:00 AM - F4: Meso
BREAK
11:30 AM - **F4.5
Soft Chemistry Based Routes to Nanostructured Inorganic and Hybrid O-I Thin Films.
Clement Sanchez 1 , Cedric Boissiere 1 , Christel Laberty 1 , David Grosso 1 , Lionel Nicole 1
1 CHEMISTRY LCMCP UMR 7574, CNRS-University of PARIS VI, Paris France
Show AbstractConsiderable effort is being currently directed to the obtention of nanostructured hybrids and transition metal oxides based materials. The use of sol-gel chemistry with or without ordered lyotropic phases as templating agents is a low cost, versatile and convenient way to produce smart functionnal thin films. The control of the nanostructuration, domain sizes, and cristallisation of these sol-gel derived coatings is of paramount importance to be able to tune the resulting properties of the final materials. This conference will present the major advances we have recently performed in the field of sol-gel derived inorganic or hybrid thin films. Some examples concerning the design of inorganic metal oxides and hybrid materials processes as thin films and some of our results concerning membranes having hierarchical structures will be presented. New films and membranes that act as sensors, photocatalysts, conductive membranes and low-k materials will be described.Recent review articles*Design, Synthesis, and Properties of Inorganic and Hybrid Thin Films Having Periodically Organized Nanoporosity. C. Sanchez, C. Boissière, D.Grosso, C. Laberty, and L. Nicole, Chem. Mater. 2008, 20, 682–737, *Applications of hybrid organic–inorganic nanocomposites, C. Sanchez, B. Julian , P. Belleville and M. Popall, J. Mater. Chem., 2005, 15, 3559, *Inorganic and Hybrid Nanofibrous Materials Templated with Organogelators, M. Llusar and C. Sanchez, Chem. Mater. 2008, 20, 782, *Photonic and nanobiophotonic properties of luminescent lanthanide-doped hybrid organic–inorganic materials.P. Escribano, B. Julian-Lopez, J. Planelles-Arago, E. Cordoncillo, B. Viana, C. Sanchez, J. Mater. Chem., 2008, 18, 23 , *Biomimetism and bioinspiration as tools for the design of innovative materials and systems C. Sanchez, H. Arribart, MM Giraud-Guille. Nature Materials, 2005, Vol 4 , p277.*Mechanical properties of hybrid organic-inorganic materials, F. Mammeri, E. Le Bourhis, L. Rozes, C. Sanchez, . Mater. Chem., 2005, 18, 23.
12:00 PM - F4.6
Nanostructured Metal Oxide and Composite Electrodes for Use in Ultracapacitors.
Michael Brumbach 1 , Bruce Bunker 1 3 , Bonnie McKenzie 2
1 Electronic and Nanostructured Materials, Sandia National Laboratories, Albuquerque, New Mexico, United States, 3 Center for Integrated Nanotechnology, Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 Materials Characterization, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractUltracapacitors, or electrochemical capacitors, are known to achieve very high specific capacitances by storing charge in the electrical double layer at the electrode/electrolyte interface where the charges are separated over very short distances. Additionally, charge storage can be accomplished via surface adsorption and/or via redox processes within the bulk electrode. Maximizing power densities and other desired properties of ultracapacitors requires configuring redox-active materials in specific architectures that: 1) maximize electrolyte-electrode contact area, 2) minimize transport distances for both electrons and charge compensating species such as protons, and 3) minimize transport barriers via inclusion of conducting material. We have developed a range of simple solution-based processing methods that enable us to systematically vary the compositions and architectures of multi-component composites at the nano-scale. We have studied the role of architecture on charge storage by using nanocomposites containing electrochemically inert network formers such has TiO2 and Nb2O5. RuO2 functions as the electroactive material while polymeric species can function to direct nanostructure formation and/or to provide conductive pathways. The electrochemical performance of the resulting nano-structured electrodes has been characterized using cyclic voltammetry and electrochemical impedance spectroscopy. The results indicate that these additions have a dramatic effect on improving the performance relative to the base-line material. Mechanisms of the performance boost will be discussed in terms of both composition and architecture as determined via XPS, electron microscopies, FTIR, and a range of other characterization methods.
12:15 PM - F4.7
A Simple Solution-Based Method for Depositing Conductive Nanoscale-Coatings of RuO2 onto SiO2 Filter Paper: Obtaining Macroscopic Conductivity from Nanostructured Features.
Christopher Chervin 1 , Alia Lubers 1 , Jeffrey Long 1 , Justin Lytle 1 , Mark Westgate 2 , Katherine Pettigrew 1 , John Fontanella 2 , Debra Rolison 1
1 Surface Chemistry Branch, Naval Research Laboratory, Washington, District of Columbia, United States, 2 Department of Physics, U.S. Naval Academy, Annapolis, Maryland, United States
Show AbstractWednesday, 12/3New Presentation Time and Paper NumberF4.8 @ 11:30 PM to F4.7 @ 11:15 PMA Simple Solution-Based Method for Depositing Conductive Nanoscale-Coatings of RuO2 onto SiO2 Filter Paper: Obtaining Macroscopic Conductivity from Nanostructured Features.Christopher Chervin
12:30 PM - F4.8
Nanocrystalline Photonic Crystalline Supports as Photoanodes for Water Oxidation.
Nathan Neale 1 , Arthur Frank 1 , Arthur Nozik 1
1 , National Renewable Energy Laboratory, Golden, Colorado, United States
Show AbstractWednesday, 12/3New Presentation Time and Paper NumberF4.9 @ 11:45 to F4.8 @ 11:30 PMNanocrystalline Photonic Crystalline Supports as Photoanodes for Water Oxidation. Nathan Neale
F5: Printing, Lithography, Patterning
Session Chairs
Wednesday PM, December 03, 2008
Room 208 (Hynes)
2:30 PM - **F5.1
Develop Printable Solution Processes for Inorganic Semiconductors.
DooHyoung Lee 1 , Yu-Jen Chang 1 , SeungYeol Han 1 , Wei Wang 1 , Yu-Wei Su 1 , Gregory Herman 2 , Wei-Fang Su 3 , Chih-hung Chang 1
1 Chemical Engineering, Oregon State University, Corvallis, Oregon, United States, 2 , Sharp Laboratories of America, Camas, Washington, United States, 3 Materials Science and Engineering, National Taiwan University, Taipei Taiwan
Show AbstractCurrent methods for the production of functional inorganic electronic devices are based on the sequential deposition, patterning, and etching of selected semiconducting, conducting, and insulating materials. These sequential processes generally involve multiple photolithography and vacuum deposition processes, which contribute to their high manufacturing costs. Solution-based and direct printing of inorganic materials offer the possibility of depositing high quality thin films at low temperature under atmospheric conditions, and the direct additive patterning processes that enable the fabrication of high-performance and ultra-low-cost electronics. Over the last few years, there has been tremendous progress on direct inkjet printing of polymer TFTs. Inkjet printing of inorganic materials is relatively rare compared to the inkjet printing of organic materials, especially for semiconductor materials. Recently, we have developed a simple and general route to form high performance inorganic electronic materials that is suitable for inkjet printing. We have printed a variety of electronic materials including conductors, semiconductors, insulators, and luminescent materials. In this paper, we will report our progress in this area.
3:00 PM - F5.2
Sol-Gel Inks for Direct-Write Assembly of Micro-Periodic Oxide Structures for Photonic and Sensor Applications.
Eric Duoss 1 2 , Mariusz Twardowski 1 2 , David Lorang 1 2 , Avner Rothschild 3 , Harry Tuller 4 , Jennifer Lewis 1 2
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 3 Materials Engineering, Technion – Israel Institute of Technology, Haifa Israel, 4 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractWe have pioneered an innovative and low-cost printing technique, known as direct ink writing (DIW), for the fabrication of micro-periodic oxide structures in both planar and 3D forms.* Using DIW, functional 1D arrays of TiO2 micro-wires and 3D micro-periodic structures have been patterned from concentrated sol-gel inks with characteristic feature sizes that range from ~200 nm (1D sensor arrays) to ~500 nm for 3D photonic crystals. DIW of well-defined 1D arrays of TiO2 microwires offers precise control of filament diameter and spatial location, enabling a systematic study of microwire TiO2 gas sensors. We show that TiO2 microwire arrays serve as highly sensitive gas sensors. To further demonstrate the versatility of the DIW printing approach, 3D micro-periodic structures composed of orthogonally-stacked layers of parallel oxide rods have been produced in a woodpile architecture. These 3D structures exhibit a partial photonic bandgap with a reflectivity of up to 92% in the near IR and a broad stop-peak width of ~26%. * E. B. Duoss, M. Twardowski, and J. A. Lewis, Adv. Mater. 19 (21), 3485 (2007).
3:15 PM - F5.3
Electroactive NanoInks and Printable NanoArchitectures for Energy-Efficient Thin Film Electronics.
Cheng Huang 1 , Peter Rieke 1 , Silas Towne 1 , Jim Holbery 1 , Howard Katz 2
1 Chemical, Materials, and Electrical Engineering, Energy & Environment Directorate, Battelle, Pacific Northwest National Laboratory, Richland, Washington, United States, 2 Materials Science and Engineering, and Chemistry Department, Whiting School of Engineering, Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractWe are carrying out our work on Printed Thin Film Energy (PTFE) based on our competencies of printed thin film electronics, soft solution processing sciences, interface and surface sciences, thin films and smart coating technology. This develops new electroactive nanoinks and chemical printing techniques for rapid, efficient, inexpensive and continuous disposition and architectures of thin films and multilayer assemblies for use in printable electronics, especially for energy harvesting, storage, and conversion devices. Chemical printing offers the potential for rapid multilayer spatially resolved deposition of electroactive nanoinks and printable nanoarchitectures. It also has enhanced performance, higher utilization of inks, rapid and efficient deposition compatible with large area productions. We report the fabrication processes from transistor circuits, solar cells, and fuel cells, which result in high performance, reduced materials costs and reduced fabrication costs. This work was supported by NSF-ECS and DOE.
3:30 PM - F5.4
Nano Imprint Lithography on Silica Sol-gels: a Simple Route to Sequential Patterning.
Christophe Peroz 1 , Vanessa Chauveau 1 , Etienne Barthel 1 , Elin Sondergard 1
1 Surface du Verre et Interfaces, CNRS/Saint-Gobain, Aubervilliers France
Show Abstract3:45 PM - F5.5
The Patterning of Sub-500 nm Inorganic Oxide and Nanocrystalline Semiconductor Structures.
Meredith Hampton 1 , Stuart Williams 1 , Zhilian Zhou 4 , Janine Nunes 1 , Doo-Hyun Ko 1 , Scott Retterer 2 , Joseph Templeton 1 , Edward Samulski 1 , Joseph DeSimone 1 3
1 Chemistry, University of North Carolina, Chapel Hill, North Carolina, United States, 4 , Liquidia Technologies, Research Triangle Park, North Carolina, United States, 2 Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 Chemical Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractThe Pattern Replication In Non-wetting Templates (PRINT1) technique has been extended to patterning of isolated features as well as embossed films of sub-500 nm “hard” inorganic oxides and nanocrystalline semiconductors including TiO2, SnO2, ZnO, ITO, BaTiO3, and CdSe. The low surface energy, chemically resistant, air permeable, elastomeric perflouropolyether (PFPE) based molds allow for numerous materials to be patterned on a variety of substrates including glass and transparent conductive oxides for a wide range of electronic and optical applications. PRINT is a unique route that provides for (1) large area arrays of isolated features with uniformity and precise control over shape and size (2) the patterning of materials with large aspect ratios (3) layer by layer deposition without destruction of the first layer and (4) the patterning of an extensive array of materials with amenability to surface functionalization and (5) a cost effective fabrication process that is scalable for roll-to-roll manufacturing processes. We will additionally discuss pattern replication on the sub-100 nm scale for photovoltaic applications using line gratings fabricated with electron beam lithography.1. Rolland et al. J. Am. Chem. Soc. 2005, 127, 10096-10100.
4:30 PM - **F5.6
Advances in Materials for Printed Transistors.
Beng Ong 1
1 , Institute of Materials Research and Engineering, Singapore Singapore
Show AbstractPrinting thin-film transistors require solution processable conductor, semiconductor, and dielectric materials, which can be printed and retain their required performance characteristics after printing. This lecture reviews the design principles and critical issues for the development of these materials, particularly for high-throughput processing to enable low-cost transistor arrays/circuits. Progress towards design of high-performance semiconductor, conductor, and gate dielectric for this emerging technology will be presented.
5:15 PM - F5.8
Inkjet Printed Narrow Electrodes for High Performance Organic Thin-Film Transistors.
Jason Doggart 1 2 , Yiliang Wu 2 , Shiping Zhu 1
1 Chemical Engineering, McMaster University, Burlington, Ontario, Canada, 2 New Materials Design Lab, Xerox Research Center of Canada, Mississauga, Ontario, Canada
Show AbstractDrop on demand inkjet printing has recently generated a great deal of interest as a fabrication method for printed organic electronic devices such as RFID tags and organic thin film transistors (OTFTs). Specifically, a great deal of research has investigated the use of this technique for high resolution printing of the conductive components of these devices. One of the greatest challenges to achieving this goal is the ability to print electrodes of uniform film thickness, which requires the elimination of the so called ‘coffee ring effect’. This effect describes the propensity of solute to accumulate at the periphery of a drying droplet, a result which can severely diminish the conductivity of printed electrodes. Some groups have suggested that a solution to this dilemma is the addition of a cosolvent which would induce a Marangoni flow to recirculate solvent back to the center. However this solution is only viable when a cosolvent of higher boiling point and lower surface tension than the major solvent is available. Here, we describe a more widely applicable method for eliminating the coffee ring effect which allows us to print highly resolute electrodes with excellent film thickness uniformity. Our study investigated the effect of both line width (controlled via dot-to-dot spacing during printing) and the concentration of a high boiling point cosolvent. It was found that by simultaneously optimizing these two variables, one could essentially eliminate the coffee ring effect and print electrodes of nearly uniform thickness. Furthermore, by increasing the viscosity of this ink (via silver concentration), the resolution was greatly improved, such that source and drain electrodes with both electrode width and channel lengths of less than 50μm could be obtained. Incorporation of these electrodes into OTFT devices using PQT – 12 as a semiconductor yielded high performance devices with mobility of 0.1 cm2V-1s-1 and an on/off current ratio of 107, indicating negligible additional contact resistance was introduced by the printed electrodes.
5:30 PM - F5.9
Ultrasonic Spray Assisted Mist-CVD Method for High-quality Crystalline and Amorphous Oxide Semiconductors Growth.
Hiroyuki Nishinaka 1 , Yudai Kamada 1 , Keiji Kiba 1 , Naoki Kameyama 1 , Shizuo Fujita 1
1 Department of Electronic Science and Engineering, Kyoto University, Kyoto, Kyoto, Japan
Show AbstractEvolution of an inexpensive, safe and environmental-friendly ultrasonic spray assisted mist-chemical vapor deposition (CVD) method is definitely shown with the growth of high-quality crystalline and amorphous oxide semiconductors. In the mist-CVD, we use liquid solutions of source materials as precursors. They are ultrasonically atomized and the mist particles formed are transferred to the reaction area with the carrier gas[1,2]. In this way, the mist sources can substitute for vaporized sources of toxic and/or dangerous metalorganics, and therefore the mist-CVD can possess excellent controllability for source supply even comparable to metalorganic-CVD (MOCVD).An example to be shown and discussed is for the growth of ZnO and related materials. Using Zn(Ac)2 as a precursor for Zn with changing the substrate materials and temperatures, the following results have ever been obtained;(i)transparent and smooth c-axis oriented ZnO thin films were grown on glass substrates, (ii)ZnO films were grown at the temperature lower than 200C, (iii)ZnO nanowires were formed using Au catalyst, (iv)single-crystalline ZnO on sapphire attained the mobility of 70 cm2/Vs, which was reasonably high compared to various ZnO thin films grown by MOCVD, and (v)two-dimensional step-flow growth, which had been difficult by MOCVD, was achieved by homoepitaxial layers on ZnO substrates. Doping and alloy layers were successfully achieved by adding the required source precursors in the source solution. The results showed as followed; (i)Al-doped ZnO on glass attained low resistivity of 6x10-4Ωcm, which was a standard for certain applications as a transparent conducting oxide, and (ii)single crystalline (0001)-oriented wurtzite Zn1-xMgxO thin films on sapphire were prepared between x=0 and 0.25 without phase segregation of rocksalt structure.Other oxide thin films such as Al2O3 and Ga2O3 were also obtained by the mist-CVD method. The mixture of Ga2O3 and Al2O3, that is, (AlxGa1-x)2O3 successfully changed the optical bandgap. It may open new application by the growth of metastable α-Ga2O3, in contrast to strong tendency of growing β-Ga2O3, on sapphire (α-Al2O3), where the crystal structure matches between the epilayer and the substrate.Mist-CVD is a low cost solution-based growth method, but it can be compatible or even superior to MOCVD as evidenced by the growth of high quality ZnO single crystal thin films. This technique is also suitable for the growth of polycrystalline and amorphous films on large substrates for the fabrication of transparent thin films and thin film devices. In the symposium the advantages and potential of the mist-CVD method, which is not only low cost and environmental friendly but also superior to the existing CVD methods for the growth of oxide thin films are demonstrated and discussed.[1]H. Nishinaka, T. Kawaharamura, S. Fujita, Jpn. J. Appl. Phys., 46 (2007) 6811. [2]T. Kawaharamura, H. Nishinaka, S. Fujita, Jpn. J. Appl. Phys., 47 (2008) 4669.
F6: Poster Session: Porous, Sol-Gel and TCO
Session Chairs
Thursday AM, December 04, 2008
Exhibition Hall D (Hynes)
9:00 PM - F6.1
Formation of Mesoporous Silica/Nanostructured Metal Thin Films by Dipcoating and Electrodeposition.
Roger Campbell 1 , Jason Manning 1 2 , Caleb Hill 2 , Martin Bakker 1 2 , Dong Ryeol Lee 3 , Xuefa Li 3 , Jin Wang 3
1 Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama, United States, 2 Center for Materials for Information Technology, The University of Alabama, Tuscaloosa, Alabama, United States, 3 Advanced Photon Source, Argonne National Labortory, Argonne, Illinois, United States
Show AbstractThe simple sol-gel synthesis of mesoporous silica thin films of a variety of geometries coupled with electrodeposition into the films has raised interest in the potential of such hybrid silica/metal nanostructures for applications in catalysis, information and energy storage, and sensors. Electrodeposition into mesoporous silica films has been largely limited to films formed on Indium Tin Oxide conducting glass. We have determined that both SBA-15 and SBA-16 mesoporous silica films can adhere to a range of metals, even after removal of the templating block copolymer. Electrodeposition of nickel and cobalt into the thin films has been clearly demonstrated in the case of the SBA-15, through the use of Grazing Incidence Small Angle X-ray Scattering (GISAXS) and magnetometry. However, TEM imaging suggests that the nanostructures grown into SBA-15 and SBA-16 are not stable for long periods of time.
9:00 PM - F6.10
Stabilizing Mesoporous Silica Films Using Multiple Organosilanes and Manipulating The Functionalization Sequence.
B. Singh 1 , A. Jain 1 , D. Gandhi 1 , R. Moore 2 , G. Ramanath 1
1 Department of Materials Science & Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 College of Nanoscale Science & Engineering, State University of New York, Albany, New York, United States
Show AbstractMesoporous silica (MPS) thin films are attractive candidates for electrically isolating adjacent layers in nanodevice wiring. While porosity decreases the signal propagation delays due to decreased resistance-capacitance coupling, the entailing high surface area makes MPS susceptible to moisture uptake and metal. Here, we show that passivating MPS with more than one organosilane with different molecular termini provides several-fold greater protection against such instabilities, than improvements observed by functionalizing MPS with either type of organosilane individually. We further show that the organosilane functionalization sequence is crucial, and can be used to fine tune the MPS film properties. Our findings are germane for realizing high-stability low k dielectrics for high-performance, high reliability nanodevices. Bias thermal annealing (BTA) measurements of Cu/treated-MPS/Si/Al structures with MPS films functionalized with bis[3-(triethoxysilyl)propyl] tetrasulfide (BTPTS) and trimethylchlorosilane (TMCS) exhibit at least 3 orders of magnitude greater time to dielectric breakdown compared to MPS functionalized individually with either organosilane. Infrared spectroscopy measurements indicate that the increased stability is due to Cu blocking by the multiple sulfur atoms in the tetrasulfide group in BTPTS and decreased moisture uptake is caused by hydrophobic passivation with TMCS. Reversing the functionalization sequence results in lower-k value, lower leakage currents and higher dielectric breakdown voltage. BTA and infrared spectroscopy measurements indicate that this difference is caused by more effective moisture removal in the latter case when MPS is treated with TMCS first. Furthermore, this sequence does not adversely impact Cu immobilization even though X-ray photoelectron and auger electron spectroscopy depth profiles indicate a lower sulfur content in films treated with TMCS first. This strategy can be conceivably extended to other functionalization chemistries for designing high stability porous low-k materials.
9:00 PM - F6.11
Characterization of Nanostructured Magnetite Thin Films Produced by Sol-Gel Processing.
Ali Eken 1 , Ahmet Ozenbas 1
1 Metallurgical and Materials Eng., Middle East Technical University, Ankara Turkey
Show AbstractPresently iron oxides are extensively used in many technological applications. Thin films of magnetite are used for magnetic recording applications, tunnel magnetoresistance (TMR) devices, magnetic sensor technology and room temperature giant magnetoresistance (GMR)applications. Being a half metallic material, magnetite is also a suitable candidate for spintronic device applications because of its 100% spin polarization.Therefore it can be used in magnetoelectronic applications in a wide range of temperature due to its high Curie temperature.Magnetite (Fe3O4) thin films were prepared by a sol-gel process in which, a solution of iron (III) nitrate dissolved in ethylene glycol was applied on glass substrates by spin coating. The film thickness was changed by changing the spinning rate. Xerogel films were obtained by drying the coated films at 110 °C. Xerogel films were annealed between 300 °C and 450 °C in order to observe the phases existing in the films at different temperatures. Viscosity measurements indicated that the solution showed a Newtonian behaviour and viscosity was found as 0.021495 Pa.s. DTA analysis showed that, annealing temperature should be selected between 291 °C and 350 °C in order to produce magnetite thin films. Prepared magnetite thin films were characterized by XRD, SEM, AFM, VSM and UV-Vis spectrometer. From in-plane grazing angle diffraction studies of the thin films, magnetite phase was observed by annealing the films at 300 °C. Reflectivity profile shows that thin film surfaces have roughness of 1.3 nm. From the SEM studies, it was shown that films with defect free surfaces were obtained and by cross section studies, thickness of the films was found as ~100-200 nm. According to the AFM results of the film surfaces, crack free films with near spherical grains (size ~ 55 nm) were obtained. UV-Vis spectrum results showed that transmittance of the films increases with decreasing annealing temperature and increasing spinning rate. Up to 95.99% transmittance is observed between the wavelengths of 900-1100 nm. Magnetic properties of magnetite thin films were also examined by VSM (Vibrating Sample Magnetometer) and ferromagnetic behaviour was shown using VSM data.
9:00 PM - F6.12
Photoinitiated Molecular Assembly and Thin Film Formation in Ti-alkoxide Systems.
J. Musgraves 1 , Zachary Schneider 3 , Kelly Simmons-Potter 2 3 , B.G. Potter 1 , Timothy Boyle 4
1 Materials Science and Engineering, University of Arizona, Tucson, Arizona, United States, 3 College of Optical Sciences, University of Arizona, Tucson, Arizona, United States, 2 Electrical and Computer Engineering, University of Arizona, Tucson, Arizona, United States, 4 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractThe formation of dielectric and charge transporting layers via solution-phase deposition is of interest for microelectronics and energy conversion device structures (photovoltaics, fuel cells) as an alternative to physical or chemical vapor phase deposition routes. In the present work, photosensitive, Ti-alkoxide precursors, possessing bulky ligand groups with enhanced stability against conventional hydrolysis and condensation, have been used to demonstrate the photoinduced formation of partially condensed, oxide-containing thin film materials directly from dilute solution and from spin-coated precursor films. Optical spectroscopic probes of the vibrational and electronic structure of the precursor and photoproducts, in conjunction with quantum chemical computations (density functional theory), have been used to provide insight into the effect of photoexcitation in these systems. Ultraviolet irradiation of hydrous-pyridine solutions of (OPy)2Ti(TAP)2 (where OPy = OC6H6N and TAP = OC6H2(CH2N(CH3)2)3), at photon energies resonant with π-π* transitions of the cyclic ligands present in this alkoxide precursor, has resulted in the preferential disruption of the TAP group and the initiation of hydrolysis and condensation. Electron microscopy of photodeposited films formed from solution reveals a nanoporous material whose microstructure can be altered through control of solution water content as well as irradiation conditions. Spectroscopic results further suggest that inherent differences in the dynamics of molecular assembly between the dilute solution and solid-state precursor materials, as well as the nature of photoexcitation in either case, can influence film formation and the resulting structure of the deposited material. Post-deposition thermal processing has also been employed to remove unreacted organic groups resulting in the production of a fully inorganic material. Through patterned photoexposure, the direct fabrication of microscale physical relief structures has been demonstrated, thus indicating the potential of this deposition technique to simultaneously tailor both nano- and microscale film structure by combining chemical and optical process controls.
9:00 PM - F6.13
Selenium as a Template for the Synthesis of Inorganic Materials with Different Compositions and Properties.
Pedro Camargo 1 , Younan Xia 1
1 Biomedical Engineering, Washington University in St. Louis, St Louis, Missouri, United States
Show AbstractThe reactivity of Selenium (Se) towards metals (such as Ag and Ru) can be exploited to enable the synthesis of inorganic materials presenting a range of different compositions. When colloidal spheres of amorphous Se (a-Se) were reacted with Ag atoms, Se@Ag2Se spheres could be formed. These core-shell spheres were then converted into Se@MSe (M=Zn, Cd, and Pb)via cation-exchange with Zn2+, Cd2+, and Pb2+. All the colloidal spheres prepared using this method are monodispersed in size and characterized by a spherical shape and smooth surface. Starting from the same batch of Se@Ag2Se, the resultant Se@MSe samples were essentially the same in size. To demonstrate their application, they were employed as building blocks to photonic crystals by self-asssembly. Furthermore, these core-shell colloidal spheres can be easily made superparamagnetic by incorporating Fe3O4 nanoparticles into the a-Se cores. In addition to colloidal-spheres, t-Se nanowires can also be employed as templates for the synthesis of inorganic nanotubes.
9:00 PM - F6.15
Capillary-molded Chalcogenide Glass Waveguides for Integrated Photonic Devices.
Candice Tsay 1 , Shanshan Song 1 , Christi Madsen 2 , Craig Arnold 3 1
1 Department of Electrical Engineering, Princeton University, Princeton, New Jersey, United States, 2 Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, United States, 3 Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States
Show AbstractThe optical properties of As2S3 chalcogenide glass at infrared wavelengths - high transmittance and high refractive index - make this an ideal waveguide material for integrated photonic devices. However, due to the material’s low glass transition temperature (Tg ~ 185°C) and high coefficient of thermal expansion (α = 21.4ppm C-1), fabrication using vacuum-based thin film deposition processes is challenging. We report on a solution-based approach for low temperature fabrication of planar As2S3 strip waveguides, wherein a liquid solution of As2S3 glass is created by dissolving bulk glass in propylamine solvent and then cast in capillary channel molds formed by soft lithography. The adaptability of this molding technique allows for the formation of planar waveguide structures with a variety of aspect ratios, faciliating on-chip integration and alignment with other devices. Using this process, straight and serpentine waveguides with a 2:1 width-to-height ratio have been fabricated with widths ranging from 10μm-80μm. Process optimization to reduce film inhomogeneities is discussed along with structural and optical characterization of the waveguides.
9:00 PM - F6.16
Low-Temperature Plasma Processing Promoting Densification-Crystallization of Sol-gel Titanium Oxide Thin Films.
Gregorio Bottaro 1 , Lidia Armelao 2 , Giovanni Bruno 1 , Maria Giangregorio 1 , Maria Losurdo 1 , Eugenio Tondello 3
1 IMIP-CNR and INSTM, Department of Chemistry, Bari University, Bari Italy, 2 ISTM-CNR and INSTM, Department of Chemistry, Padova University, Padova Italy, 3 Department of Chemistry, Padova University, Padova Italy
Show AbstractNowadays, one of the main challenges in materials chemistry concerns the synthesis of advanced functional oxide thin films at mild temperature, yielding device quality characteristics. In particular, growing needs of oxide coatings on plastic and large area substrates for optical and electronic applications, requiring the tailoring of the films/substrates interfaces properties also during the materials synthesis, dictates the development of low-temperature processes. Therefore, numerous thin film fabrication processes for lowering crystallization temperature of amorphous materials have been investigated, based on microwave irradiation, electron beam and/or laser irradiation, and water vapour exposure.In this widespread scenario, an appealing strategy is represented by the original and synergic combination of mild liquid phase techniques for thin film preparation, mainly sol-gel, and “non equilibrium” densification-crystallization processes, thus exploiting the peculiar features of plasmas chemistry. In this framework, our work is dedicated to the study of the morphological, structural and chemico-physical modification of as-prepared sol-gel thin films subjected to plasma treatment. In particular, titanium dioxide (TiO2) has been adopted as a model system for the investigation of the effect of the finite lifetime metastable species and reactive species originated in Ar, O2 an Ar-O2 plasmas on titania densification-crystallization processes. Titania thin films have been prepared by sol-gel dip-coating on Si(100) from alcoholic solutions of titanium n-butoxide. As-prepared films were directly subjected to plasma treatment in a parallel plates radio-frequency reactor. Process parameters have been optimized in order to induce titania crystallization-densification under mild conditions. The process dynamic has been studied by means of multi-techniques characterization playing particular attention to the surface and interface modifications induced by the plasmas treatment. Films have been fully characterized by Glancing Incidence X-ray diffraction (GIXRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Moreover, the microstructural evolution has been correlated to optical properties exploiting Spectroscopic Ellipsometric (SE, UISEL-JY operating in the 0.75-6.5eV range) investigation. The proposed synthesis of high quality titanium dioxide films, based on the innovative combination of the mild sol-gel route and radio-frequency plasma processing, can be effectively extended to the improvement of the microstructural order of various oxide-based films of technological interest (La2O3, ZnO, Cu2O, CuO,…).
9:00 PM - F6.17
Low Temperature Sintering of Titania Nanoparticles Utilizing Hydrothermal Treatments.
Sukanya Murali 1 , Sau Pei Lee 1 , Sarika Phadke 1 , Judith Sorge 1 , Dunbar Birnie, III 1
1 Materials Science & Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States
Show AbstractThe objective of this work is to prepare titania porous coatings with enhanced connectivity between particles in order to increase electrical conductivity within the film. Titania films are utilized for many applications and can be produced with good connectivity between the particles if sintering is done at elevated temperatures such as 450-500°C. A low temperature method for creating the same connectivity between particles as sintering does is necessary for applications that utilize flexible substrates. Currently, this research is focused on coating the titania layers on flourine doped tin oxide glass and indium tin oxide coated flexible polyethylene terephthalate (PET) substrates for use in dye sensitized solar cells. Both a hydrothermal sintering method and steam treatments have been studied and compared to determine their effects on a nanoparticulate titania film. First, green films were produced via doctor blading dispersed titanium dioxide particles and then each of these films were tested with each low temperature sintering method. In the hydrothermal method, the films were placed in a dispersion with titanium dioxide and titanium isopropoxide in either an acidic or basic medium and heat treated at temperatures under 100°C. For the reactive steam sintering, the films were infiltrated with titanium isopropoxide and heated with water vapor. When the water is heated, the steam reacts with the TIP and creates connectivity between the original titanium dioxide particles. These methods were characterized by studying the morphology changes visible in transmission and scanning electron microscopy as well as x-ray diffraction to ensure anatase form of the titanium dioxide.
9:00 PM - F6.18
Structural and Electrical Properties of Indium doped Single Crystal ZnO Films Synthesized by Hydrothermal Method.
Le Quang 1 , Gregory Goh Kia Liang 1 , Lim Swee Kuan 1
1 , IMRE-Singapore, Singapore Singapore
Show Abstract9:00 PM - F6.2
Large Scale 3D Porous Metallic Films for Electronic Applications.
Peng Wan 1 2 , Xindi Yu 1 , Paul Braun 1
1 Department of Materials Science and Engineering, Beckman Institute, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana Champaign, Urbana, Illinois, United States, 2 College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, HuBei Province, China
Show AbstractThree-dimensionally (3D) porous metal structures have been studied for acoustic damping, charge storage, and plasmonic applications because of their unique mechanical, electronic, chemical and optical properties. Here we demonstrate the synthesis of a porous nickel film with uniform 3D interconnected structure via colloidal templating. A hexagonal non-close packed silica colloidal crystal was first formed from 500nm diameter colloidal spheres on ITO substrate by spin coating. The colloidal crystal film is then used as the template for the electrochemical deposition of a 5 µm thick porous nickel film. Both the pore diameter and film thickness can be varied by changing the colloidal particle diameter and electrochemical deposition parameters, respectively. The porosity of the Ni film is further tuned by electrochemical or chemical etching, which increases the pore diameter, and oxidation, which forms a uniform layer of nickel oxide over the structure. The resulting porous nickel/nickel oxide composite film has very interesting electronic and optical properties. The spin coating approach used here is not only a fast and scalable technique that is compatible with standard IC processing, but also eliminates the cracks that usually appear during conventional colloidal crystal growth processes. This proves to be critical for some of the electronic applications, where current needs to flow uniformly across the whole structure.
9:00 PM - F6.20
Preparation and Characterization of ITO Thin Film Grown by Photo Reaction of Nano-particle using Excimer Laser.
Tetsuo Tsuchiya 1 , Fujito Yamaguchi 2 , Isao Morimoto 2 , Tonohiko Nakajima 1 , Toshiya Kumagai 1
1 , National Institute of Advanced Industrial Science and Technology, Tsukuba Japan, 2 Central R&D Laboratories, Asahi Kasei Corporation, Fuji-city Japan
Show AbstractTin doped Indium oxide (ITO) thin film was widely used for optical and electronic applications such as touch panel contacts, electrodes for LCD and electro-chromic displays, energy conserving architectural windows because of its good electrical and optical properties. However, recently, serious problem that Indium resource is lack in next generation has become recognized more and more. Therefore, it is necessary to decrease total amounts of Indium in thin film preparation process. To decrease the indium amounts in the process, a direct writing method using nano-particle would be useful. In this study, we investigated the preparation of ITO film by pyrolysis and photolysis of nano-particle coated on a substrate. ITO nano-particle was synthesis by a solvothermal method. The particle size is 2-4nm. The nano-particle dispersed solution was spin-coated onto a single-crystal substrate, then dried at 100 °C in air to eliminate the solvent. Then, the nano-particle film was irradiated by KrF excimer laser at room temperature. The crystallinity of the obtained films was examined by x-ray diffraction θ-2θscans. The cross-section transmission electron microscopy (XTEM) observations were performed. The resistivity, carrier concentration and mobility of the ITO film were measured by a Van der Pauw method. In the case of thermal process, the resistivity of the film sintered at 500 degree in N2 was 4.0×10-3Ωcm. On the other hand, the film grown by excimer laser irradiation at room temperature showed 5.9×10-4Ωcm. It was found by SEM and TEM observation that these differences are caused by the differences of film microstructure. Detailed procedures of film preparation and the results will be presented in the paper.
9:00 PM - F6.21
Hydrothermal Growth and Electrical Mobility of Oriented ZnO Thin Films on Glass Substrates.
Yan Guo 1 , Suk Jun Kim 1 , Elliott Slamovich 1 , Eric Stach 1 2 , Carol Handwerker 1 2 , Paul Brazis 3 , Dan Gamota 3
1 School of Materials Engineering, Purdue University, West Lafayette, Indiana, United States, 2 Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana, United States, 3 Physical and Digital Realization Research Center, Motorola Labs, Schaumburg, Illinois, United States
Show AbstractOriented zinc oxide thin films were grown on ZnO nanoparticle-seeded glass substrates using a mild aqueous solution by a hydrothermal process at low temperature (90oC). X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the resulting films. Hall-effect measurements were used to assess the film electrical mobility. A variety of microstructures were produced, depending on the supersaturation of the precipitation solution during growth. The morphology and characteristics of films mainly depend on the nucleation states in the hydrothermal precipitation. Spiral growth of ZnO films implies that the nucleation occurs at dislocations on the growing surface. ZnO films composed of a hexagonal nanorod morphology display a strong preferred orientation of <0001> normal to the glass substrate. Seeded ZnO nanorods exhibit very well-aligned textures without deep grain boundaries, whereas unseeded ones have arrays of random grain boundary orientation. This result indicates that ZnO nanoparticle seeds play an instrumental role in the formation of oriented ZnO films. Hall-effect measurements show an increase in the electrical mobility of seeded ZnO nanorods compared to unseeded ones. ZnO films exhibiting the spiral growth mode have the highest mobility (120cm2/Vs), a result that is consistent with microstructural characterization which indicates that coalescence dramatically increases the contact between the ZnO grains. These results will be discussed in the framework of potential impacts of dislocation density and grain boundary on the electronic performance of these films.
9:00 PM - F6.22
Low-Temperature Solution Based Fabrication of ZnO Thin Film Transistors for Flexible Electronics.
Liwei Wang 1 , Sunghee Lee 1 , Junhyun Cho 1
1 Mechanical Engineering, SUNY, Binghamton, New York, United States
Show Abstract9:00 PM - F6.23
High Yield Solution Synthesis of ZnO Nanowires and Films using a Microreactor.
Kevin McPeak 1 , Jason Baxter 1
1 Chemical & Biological Engineering, Drexel University, Philadelphia, Pennsylvania, United States
Show Abstract9:00 PM - F6.25
Layer-by-layer Deposition of Utrathin Ceramic Films by Spin Coating.
Edson Leite 1 , Caue Ribeiro 2
1 Chemistry, Federal University of Sao Carlos, Sao Carlos, Sao Paulo, Brazil, 2 , EMBRAPA, Sao Carlos, Sao Paulo, Brazil
Show AbstractThis work describes the combined use of nanocrystal water-based colloidal dispersion with spin coating deposition in order to obtain ultrathin ceramic films. We have used tin oxide (SnO2) and antimony doped thin oxide (ATO) nanoparticles, with particle size ranging from 1nm to 6 nm, to develop the deposition approach. The films obtained in different deposition condition (solution concentration, speed rotation and deposition time) were characterized by elipsometry, electron microscopy (FE-SEM and TEM/HRTEM) and atomic force microscopy, showing that the process has the ability to produce ultrathin ceramic films, with thickness ranging from 10-100nm, with good particle packing. Additionally, electrical measurement in the films indicates good homogeneity and potential for various applications.
9:00 PM - F6.26
Spin-spray Plated Ferrite Films with Controlling the Crystalline Orientation by Underlayers.
Hajime Wagata 1 , Masaru Tada 2 , Masanori Abe 2 , Masahiro Yoshimura 1 , Nobuhiro Matsushita 1
1 Electronic Chemistry, Tokyo Institute of Technology, Yokohama Japan, 2 Physical Electronics, Tokyo Institute of Technology, Tokyo Japan
Show AbstractThe spin-spray ferrite plating method enables us to deposit spinel ferrite films at very low temperature of 100 degree C just by spraying aqueous solutions to the substrate without post-deposition heat treatment. In spite of a low process temperature, the deposited films (the intermediate between Fe3O4 and γ–Fe2O3) are highly crystallized and exhibit saturation magnetization of 400-480 emu/cm3 as large as the bulk ferrite sintered at 1200 degree C, and coercivity of 20-100 Oe. Their real permeabilities of a few tens up to hundreds MHz is comparable to those of films prepared by the sputtering and the pulse-laser-deposition methods which require a high process temperature above 600 degree C. We reported that the spin-sprayed ferrite films would be applicable as the conducted noise suppressor on the printed circuit boards in the mobile computers and cellular phones utilizing their large magnetic loss in a several GHz range. These excellent properties are also attributed to the columnar structure of films, which are grown perpendicular to the substrate surface with a diameter of few hundred nanometers. In addition to the columnar structures, the crystallite orientation is also important for spinel ferrite films to control their magnetic properties. For example, (111)-orientated spinel ferrite films could exhibit high permeability due to a very small magnetic anisotropy field in film plane, since the first order of magnetic anisotropy constant K1 vanished.In this study, we investigated the control of crystallite orientation of ferrite films by using various kinds of under layers such as sputtered titan metal and nickel oxide underlayers, and solution-processed zinc oxide underlayer on glass substrates.The ferrite (the intermediate between Fe3O4 and γ–Fe2O3) film was prepared by spin-spray technique using a reaction solution containing 20 mM of FeCl2 and an oxidizing aqueous solution containing 65 mM of KCH3COO and 5.0 mM of KNO2. They were sprayed simultaneously at the supplying rate of 50 mL/min onto the substrates fixed on a turning table keeping the temperature at 90 degree C. The crystal structure and orientation were characterized by X-ray diffraction (XRD) and the morphology of the films was observed by scanning electron microscopy (SEM). The thicknesses of films were about 1.0 μm for 30 minutes deposition. The XRD diagram suggested that magnetite films deposited on as-sputtered amorphous nickel oxide unerlayer had well (111) orientation while the films deposited on another underlayers showed no crystalline orientation. From SEM observation, all ferrite films were constructed from columnar structures except for that deposited on the metal titan underlayer. These results indicated that crystalline orientation depended on the kind and crystallite orientation of the underlayer. For next step, their dependencies of magnetic properties on the crystallite orientations are now under investigation.
9:00 PM - F6.27
Low-temperature Processing of Sol-gel derived Metal Oxide Thin Films using Supercritical Carbon Dioxide Fluid.
Hiroshi Uchida 1 , Kaori Fujioka 1 , Seiichiro Koda 1
1 Department of Material and Life Sciences, Sophia University, Tokyo Japan
Show AbstractWe demonstrate here a novel technique using supercritical carbon dioxide (scCO2) fluid for lowering processing temperature of sol-gel-derived metal oxide thin films. Conventional sol-gel film deposition includes heat treatment operation at higher temperature for decomposing and crystallizing the precursor gel films although it could be a critical disadvantage due to thermal damage or interdiffusion to neighboring layers and/or substrates. For manufacturing advanced electronic devices such as large-scale integrated circuits, nano-/meso-sized materials, inorganic-organic composites, etc., technical breakthrough for film processing at lower temperature would be required strongly and then various approaches have been examined in recent researches. We recognize that the chemical process using supercritical fluids would be an effective approach because of its unique characteristics; e.g., extraction ability, transportation capability, and reaction equilibrium etc., are quite favorable for decomposition and crystallization of the precursor gel films. In this work, an innovative chemical process for sol-gel synthesis using scCO2 fluid as a reaction media is proposed in order to achieve low-temperature processing of crystalline oxide thin films. The effects of fluid conditions (temperature, pressure, etc.) and additives on the sol-gel synthesis reaction under scCO2 fluid were investigated. The film processing was performed in a hot-wall closed vessel filled with scCO2 fluid. In the case of titanium dioxide (TiO2), precursor gel films prepared on silicon wafer by sol-gel coating using Ti-alkoxide solution were converted to crystalline TiO2 (anatase) films successfully by treatment in scCO2 without additive agent at a fluid pressure of 15 MPa and a substrate temperature of above 250oC, which is significantly lower than the processing temperature of conventional sol-gel deposition. XPS analysis indicated that the hydrolysis and polymerization reactions of Ti-alkoxide in precursor gel films had proceeded at a substrate temperature of above 200oC to form titanium-oxygen (Ti-O) networks and that byproducts such as alcohols were removed from the resulting films, whereas no chemical degradation such as oxidation or corrosion was observed on surface of silicon wafer even after scCO2 treatment at a substrate temperature up to 300oC. Additive agents such as water (H2O) and nitrogen-oxygen mixture (N2-O2) promoted the decomposition and crystallization of precursor gel films in scCO2 fluid furthermore to form the crystalline TiO2 (anatase) films at a substrate temperature at as low as 150oC although it also produced a great deal of surface absorbates consisted of carbonates and hydroxides on the film surface. These results suggest that the sol-gel synthesis using scCO2 fluid enables low-temperature processing of crystalline oxide films rather than conventional techniques such as sol-gel deposition and CVD.
9:00 PM - F6.28
Optical and Electrical Properties of Sol Gel Derived ZnO Thin Films.
Mariyappan Shanmugam 1 , Mahdi Farrokh Baroughi 1
1 Electrical Engineering and Computer Science, South Dakota State University, Brookings, South Dakota, United States
Show Abstract9:00 PM - F6.3
Block Copolymer Solution-Based Patterning and Growth of Size Controlled One-Dimensional Functional Nanomaterials.
Divya Goel 1 , Bo Li 1 , Robert Hamers 1
1 Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States
Show AbstractIn the present work, a facile and low cost solution based approach is developed for the nucleation and growth of large-scale of oriented 1-D nanomaterials, zinc oxide nanorods and carbon nanofibres. ZnO is known as one of the most important multifunctional semiconductor material for its wide band gap and large excitonic binding energy at room temperature. Particularly, one-dimensional (1-D) ZnO nanostructures such as wires, rods, belts, tubes, and whiskers have been extensively studied because of their functional applications in electronic and optoelectronic devices, gas sensors, field-emission devices, solar cells, and photocatalysts. Carbon nanotubes/fibres have potential applications in microelectronic devices, energy storage media and nano-probe tips. CNTs have especially been regarded as the most promising materials for emitters in field emission displays due to their low turn-on field and high emission current. Substrates coated with nanocatalyst for seeded growth of well-oriented 1-D arrays were made by self-assembly of amphiphilic block copolymer micelles loaded with precursor catalyst ions. The potential of synthesizing nanocatalysts with adjustable composition is discussed. The ability to tailor seed size and spacing by varying block lengths has been demonstrated to promote controllable synthesis of ZnO nanorods and CNFs with adjustable diameter and density. Manipulation of the growth conditions provided further handle to control the length and the diameter of the 1-D nanostructures. Well-aligned zinc oxide nanorod arrays with high aspect ratios are fabricated on these patterned substrates by a simple solution–phase, low temperature approach in an aqueous solution. Vertically aligned CNFs are grown using low-temperature plasma enhanced chemical vapor deposition technique. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence emission.
9:00 PM - F6.30
Spin-spray Deposited Multiferroic Composite with Strong Interface Adhesion.
Ming Liu 1 , Ogheneyunume Obi 1 , Jing Lou 1 , Stephen Stoute 1 , Jian Huang 3 , Zhuhua Cai 2 , Katherine Ziemer 2 , Nian Sun 1
1 Electrical and Computer engineering, Northeastern University, Bosotn, Massachusetts, United States, 3 Center for Integrated Nanotechnologies (CINT), Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 Chemical Engineering, Northeastern University, Boston, Massachusetts, United States
Show Abstract9:00 PM - F6.31
Influence of Fluid Physical Properties on Ink-Jet Printability.
Daehwan Jang 1 , Dongjo Kim 1 , Jooho Moon 1
1 , Yonsei University , Seoul Korea (the Republic of)
Show AbstractInk-jet printing is an attractive method for patterning and fabricating objects directly without the need for masks. However, the printable ink materials are limited. Inappropriate ink will lead to instable ink-jetting in which long-lived filaments form, leading to the unwanted satellite formation and deposition at incorrect position. Length and life time of the droplet filament influence considerably the printability of the inks. In order to be printed, it is necessary for the fluids to have adequate physical properties. We investigated the inter-relationship between the printability and the physical properties of the fluids for ink-jet printing. Fluid properties are characterized using a dimensionless number, the inverse of Ohnesorge number (Z-1) that relates the viscosity, surface tension force and density of fluid. We have redefined the printable range of the Z-1 by in-situ monitoring droplet formation dynamics for various fluids having varying Z-1 values. The suitable ink-jet printing range can provide a clue whether or not the fluids are stably and accurately printed by ink-jetting. We determine the range of 4 < Z-1 < 14 by considering practical aspects of the printing such as single droplet formability, minimum stand-off distance (i.e., the distance from nozzle tip to the substrate) from nozzle, positional accuracy, and maximum allowable jetting frequency.
9:00 PM - F6.4
TiO2–based Resistance Switching Memory Devices on Plastic.
Junggwon Yun 1 , Kyoungah Cho 1 , Sangsig Kim 1
1 Electrical Engineering and Institute for Nano Science, Korea University, Seoul Korea (the Republic of)
Show AbstractResistance switching memory devices fabricated on flexible plastic substrates through spin-coating of titanium oxide (TiO2) solution were characterized in this study. The memory devices were constructed with vertically stacked layers of Au/TiO2/Au. Resistance switching cycles were observed after electro-forming process. The ratio between a high-resistance state (off state) and a low-resistance state (on state) was larger than 102. The retention of on/off states lasted even after 104 sec. While the substrates experienced a tensile or compressive strain of 0.7%, the resistance switching characteristics remained unchanged. These results open a possibility of the achievement of low-cost and large-area resistance switching memory on plastic.
9:00 PM - F6.6
Preparation and Characterization of Three-dimensionally Ordered Macroporous Niobium Oxide.
Yao Li 1 , Wu-Hong Xin 1 , Jiu-peng Zhao 2
1 Center for Composite Materials, Harbin Institute of Technology, Harbin China, 2 Department of Applied Chemistry, Harbin Institute of Technology, Harbin China
Show Abstract9:00 PM - F6.7
Doped Nanoporous Tin Dioxide Thin Films by a Template Sol-Gel Approach for Sensory Applications.
Ralf Koehn 1 , Shaofeng Shao 1 , Momtchil Dimitrov 1 2
1 Chemistry & Biochemistry, University of Munich (LMU), Munich, Bavaria, Germany, 2 Institute of Organic Chemistry, Bulgarian Academy of Sciences, Sofia Bulgaria
Show AbstractTin dioxide based gas sensors work by monitoring changes in electrical resistance that result mainly from reduction/oxidation of the crystal surface by the target gas. To-date elevated temperatures or UV light are required to achieve rapid adsorption/desorption and oxidation/reduction kinetics needed for a practical, rapid, and sensitive hydrogen detector. Very recently, nanocrystalline tin dioxide sensors showed room temperature sensitivity towards ethanol and carbon monoxide, but exhibited poor sensitivity for hydrogen gas [1-3]. Selectivity is a limitation of existing tin oxide sensors that operate at high temperatures. As hydrogen is currently used in many different sectors of technology and is expected to be the fuel of the future, a hydrogen selective sensor material active at room temperature is of considerable immediate interest [4].
We recently synthesized a unique nanocrystalline, mesoporous tin dioxide thin film exhibiting high sensitivity and selectivity to hydrogen gas at room temperature [5]. An additional advantage of this material is its relative insensitivity to other combustible gases such as CO or methane, or to ubiquitous water vapour. This material is palladium doped and transmission electron microscopy (TEM) proved its high crystallinity and a worm-like disordered mesopore structure. Recently, an adaption of the delayed humidiy treatment (DHT)[6] allowed us to gain ordered mesostructured tin dioxide with palladium contents up to 4%. HRTEM shows near-spherical interconnected nanocrystals with lattice fringe distances corresponding to cassiterite arranged in the order preformed by the used block-copolymer upon film preparation. Another advantage of the DHT is the significant increase of the pore volume and the surface area due the formation of the mesostructure revealing a bimodal pore size distribution. Furthermore, the doped tin oxide proves to be very stable and does not loose any activity due to particle growth upon exposure to reducing or oxidizing agents.
[1] Wang, Y., Jiang, X., Xia, Y., J. Amer. Chem. Soc. 125, 2003, 16176.
[2] Wu, N.L., Wang, S.Y., Rusakova, I.A., Science 285, 1999, 1375.
[3] Shukla, S., Seal, S., Ludwig, L., Parish, C., Sensors & Actuators B 97, 2004, 256.
[4] Favier, F., Walter, E.C., Zach, M.P., Benter, T., Penner, R.M., Science 293, 2001, 2227.
[5] De, G., Koehn, R., Xomeritakis, G., Brinker, C.J., Chem. Commun., 2007, 1840.
[6] Urade, V.N., Hillhouse, H.W., J. Phys. Chem. B 109, 2005,10538.
9:00 PM - F6.8
Low-temperature, Solution-based Processing of TiO2 Thin Films; Fabrication of Dielectric Mirrors and Microcavities.
Kai Jiang 1 , Andriy Zakutayev 2 , Janet Tate 2 , David MyIntyre 2 , Douglas Keszler 1
1 Department of Chemistry, Oregon State University, Corvallis, Oregon, United States, 2 Department of Physics, Oregon State University, Corvallis, Oregon, United States
Show AbstractHigh quality TiO2 thin films have been deposited from aqueous titanium-peroxo solutions via spin coating. The effects of precursor-solution pH on the crystallization behavior, morphology, and refractive index of the films were studied. From XRD measurements, the amorphous as-deposited films were found to crystallize in the anatase phase at 250 °C. Surface and cross-section SEM images reveal that the TiO2 thin film deposited from the acidic precursor is smoother and denser than that deposited from the basic precursor. Wave-guide mode-prism-coupler measurements indicate the refractive indices at 633 nm are 2.24 and 2.13 for 300 °C annealed films deposited from acidic and basic precursors, respectively. High performance dielectric mirrors and microcavities were fabricated by building alternate layers of TiO2 (high index) and AlPOx (low index) with thermal processing as low as 300 °C.
9:00 PM - F6.9
Rapid Fabrication of Microstructured Mesoporous Silica Films by Site-selective Electron Beam Irradiation and Subsequent Chemical Etching.
Atsushi Hozumi 1 , Tatsuo Kimura 1
1 , AIST, Nagoya Japan
Show AbstractMesoporous silica, which is fabricated using surfactant molecules or block copolymers as structural-determination agents, has attracted much attention as catalysts and adsorbents, taking advantage of their large surface area and uniform pore distribution within a mesoscale. Film preparation and micropatterning of such mesoporous materials are further considered key in order to apply them to sensors and electronic or optical devices lately. Considering such device applications, it is of primary importance to eliminate the structural-determination agents at low temperature, since thermal treatment causes not only cracking or peeling due to volume shrinkage, but also damages to substrate and device elements. Thus, an alternative method that may be performed without thermal treatment has been persistently required. In order to satisfy this requirement, we have previously reported a novel calcination technique, namely, photocalcination, using an excimer lamp radiating vacuum ultraviolet light of 172 nm in wavelength. Although this method is advantageous compared with the conventional thermal treatment, since it may be conducted at around room temperature, it requires relatively long treatment time. In this study, we demonstrated rapid and low temperature elimination of surfactant molecules through electron irradiation. A mesostructured film (thickness; ~ 200 nm), which was prepared through hydrolysis and condensation of tetramethoxysilane in the presence of hexadecyltrimethylammonium chloride, was irradiated with LEEB at 25 kV and 300 μA under pressures of 10 and 1000 Pa. The surfactant molecules can be eliminated completely at temperatures less than 40 °C after only 10 min (10 Pa) and 5 min (1000 Pa) of irradiation, resulting in conversion to a highly ordered mesoporous silica film without cracking. The LEEB-irradiated film also showed reasonable chemical resistance towards dilute hydrofluoric acid solution due to sufficient consolidation by cross-linking of silicate networks during the irradiation. The unirradiated regions were etched away preferentially to the irradiated areas and therefore rapid micropatterning of the mesoporous silica film was possible at low temperature by area-selective LEEB irradiation followed by chemical etching.
Symposium Organizers
David B. Mitzi IBM T. J. Watson Research Center
David Ginley National Renewable Energy Laboratory
Bernd Smarsly Justus Liebig University Giessen
Dmitri V. Talapin The University of Chicago
F7/P6: Joint Session: Solution Processed Photovoltaic Materials
Session Chairs
Thursday AM, December 04, 2008
Room 208 (Hynes)
9:30 AM - **F7.1/P6.1
FASST® Reactive Transfer Printing for Morphology and Structural Control of Liquid Precursor Based Inorganic Reactants.
Billy Stanbery 1 , M. Taylor 1 , M. van Hest 2 , J. Nekuda 2 , A. Miedaner 2 , C. Curtis 2 , J. Leisch 2 , P. Hersh 1 , D. Ginley 2 , R. Oswald 1 , L. Eldada 1
1 , HelioVolt Corporation, Austin, Texas, United States, 2 , National Renewable Energy Laboratory, Golden, Colorado, United States
Show AbstractSoluble inorganic precursors to binary Cu-Se, In-Se, and Ga-Se materials have been developed and processed by rapid thermal processing to form solid multinary reactant films for subsequent Copper Indium Gallium Selenide (CIGS) synthesis using the reactive transfer printing method designated by the acronym FASST (Field-Assisted Simultaneous Synthesis and Transfer). The FASST method is a two-stage technique which separates the deposition of two precursors in the first stage from their reactive transformation into the final material layer in the second stage. This separate deposition of the precursors, one onto the final product film’s substrate and the other onto a reusable printing plate, allows independent optimization of their corresponding deposition methods whilst eliminating their pre-reaction. This flexibility has proven immensely valuable as will be demonstrated by comparing the results of depositing these two reactant films by various combinations of low-cost solution-based and conventional vacuum-based physical vapor deposition techniques. High-performance CIGS is characterized by relatively large grain sizes and the formation within individual grains of a nanoscale interpenetrating network of copper-rich and copper-deficient domains which form a percolation network for electrons and holes respectively. Conventional high temperature co-evaporation methods have been used to synthesize all of the world record thin film CIGS devices for more than two decades, and the multi-step deposition sequences developed to achieve this performance always involve the topotactic transformation of a large-grain precursor into CIGS rather than the direct synthesis of CIGS from condensation of elemental vapors as in molecular beam deposition. This same process characteristic is enabled by the two-stage FASST method’s separation of solid multinary reactant film deposition onto two different surfaces in its first stage. This will be demonstrated by comparing the unprecedented large-grain structure of FASST-synthesized CIGS with the results of its direct synthesis from the same soluble inorganic precursors by rapid thermal processing. This unique combination of low-cost solution-based precursor deposition and FASST reactive transfer printing methods provides reduced capital costs compared to vacuum deposition methods, low thermal budget, high throughput, control of CIGS crystallographic orientation, and very high device quality CIGS.
10:00 AM - F7.2/P6.2
Use of Direct Write Methods for Low Cost Photovoltaics.
Maikel van Hest 1 , Jennifer Nekuda 2 , Jennifer Leisch 1 , Peter Hersh 1 , Alex Miedaner 1 , Calvin Curtis 1 , Ken Steirer 2 , Ryan O'Hayre 2 , Reuben Collins 2 , David Ginley 1
1 , National Renewable Energy Laboratory, Golden, Colorado, United States, 2 , Colorado School of Mines, Golden, Colorado, United States
Show Abstract10:15 AM - F7.3/P6.3
CuIn(Se,S)2 Absorbers Processed using a Hydrazine-Based Solution Approach.
Wei Liu 1 , David Mitzi 1 , Min Yuan 1 , Andrew Kellock 2 , S. Jay Chey 1
1 , IBM TJ Watson Research Center, Yorktown Heights, New York, United States, 2 , IBM Almaden Research Center, San Jose, California, United States
Show AbstractWith tunable bandgap and demonstrated high efficiency, the chalcopyrite CuInSe2 and its alloys have shown great potential as absorbers for single and multi-junction solar cells. However, the current deposition techniques mostly rely on expensive vacuum-based processing or involve complicated precursor solution preparation. These high-cost absorber preparation processes make it difficult to commercialize this technology. In this work, CuInSe2-xSx (CIS) absorbers are deposited using a simple hydrazine-based solution process. Precursor solutions were prepared by dissolving the component metal chalcogenides and chalcogen in hydrazine, forming homogeneous solutions containing adjustable concentrations of desired elements mixed on a molecular level. These precursor solutions are then spin coated on substrates followed by a heat treatment in an inert environment to produce high quality CIS thin films. Significantly, no post deposition selenization process is required using this technique. Laboratory scale devices with conventional glass/Mo/CIS/CdS/i-ZnO/ITO structure have been fabricated using CIS absorbers deposited via this process. For the baseline low-bandgap CIS system with no Ga added (to compare with our previously reported results with Ga incorporated), AM1.5 conversion efficiency of as high as ~8% has been achieved for devices with 0.45cm2 effective area.
10:30 AM - **F7.4/P6.4
All-chemically Deposited Thin Film Solar Cells.
P. Karunakaran Nair 1 , Harumi Moreno 1 , Sarah Messina 1 , David Avellaneda 1 , Oscar Gomezdaza 1 , M. T. Santhamma Nair 1
1 Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Temixco, Morelos, Mexico
Show Abstract11:30 AM - **F7.5/P6.5
Solution Routes to Synthesis of Cu(In,Ga)(S,Se)2 Chalcopyrite Solar Cells.
Jean-Francois Guillemoles 1
1 IRDEP, CNRS, Chatou France
Show AbstractLarge scale developement of photovoltaics requires large area coating of semiconductors, something solution based processes can provide. From Cu2S to CdTe or Cu(In,Ga)(S,Se)2, not to mention TiO2 in dye cells, exemples are numerous of efficient (>10%) photovoltaic devices whose semiconductors have been synthesized in aqueous solutions.This presentation will focus on growth of chalcogenides, and more specifically CuInSe2 (CIS), for which (one step)electrodeposition is a method of choice. CIS, and related compounds, are somewhat more complex to prepare than other chalcogenides due to a richer chemistry, as evidenced by the number of phases that can be formed. As grown semiconductors, when prepared at low temperatures are generally unfit for photovoltaic applications: photovoltaic application is very demanding because it is specially sensitive to material defects, already in the ppm range. On the pathway to truly functionnal materials, additionnal steps are therefore required. These involve generally annealings but also surface/interface treatments.The presentation will discuss these different aspects through the exemple of the realisation of electrodeposited CIS solar cells with efficiencies above 10%.
12:00 PM - **F7.6/P6.6
Chalcogenide Solar Cells by Printing and Solution (non-electrodeposition) Based Methods.
Ayodhya Tiwari 1
1 Thin Film Physics Group, ETH , Zurich Switzerland
Show Abstract12:30 PM - F7.7/P6.7
Fabrication and Performance of Highly Textured Electrodeposited ZnO Back Reflector for nc-Si Solar Cells.
Dinesh Attygalle 1 , Qi Hua Fan 1 , Shibin Zhang 1 , William Ingler 1 , Xunming Deng 1
1 Department of Physics and Astronomy, The University of Toledo, Toledo, Ohio, United States
Show AbstractTextured back reflector (BR) is an essential component used in substrate type solar cells for light trapping, which enhances the long wavelength absorption. Most commonly used BR consists of a reflecting metal layer(s) of Ag and/or Al and a transparent conducting oxide (TCO) layer such as ZnO. This type of BR, if properly textured, can lead to about 20% increase in the short-circuit current and cell efficiency. A widely used technique for producing the BR is sputtering due to its simplicity and easy operation for large area thin film solar cell applications. The TCO layer needs to be thick enough (>500 nm) to reach a textured structure and to prevent the metal in the BR from diffusing into the solar cell layers. Thus, the ZnO deposition becomes the bottleneck in the BR process. Significant efforts have been putting on developing novel techniques that can produce ZnO coatings with better texture and high deposition rate. In this paper, we report a novel electrodeposition procedure to fabricate uniformly textured ZnO films at high deposition rate. We show that ZnO films prepared by this novel technique have much larger surface roughness than sputter deposited films, as evidenced by AFM images and optical reflectance measurements. Thin film nanocrystalline silicon (nc-Si) solar cells are fabricated on the electrodeposited BR and sputtering deposited BR. I-V characteristics and quantum efficiency of these solar cells are compared, which show that the solar cells based on the electrodeposited ZnO BR have 2 mA/cm2 higher current density. The improvement is observed in long wavelength region as well as short wavelength region of the spectrum. Possible mechanisms accounting for this improvement is discussed.
12:45 PM - F7.8/P6.8
Zinc Oxide/Cadmium Sulfide Nanocomposites for Solar Energy Conversion.
Erik Spoerke 1 , Matthew T. Lloyd Lloyd 2 , Erica Martin 1 , David Scrymgeour 2 , Dana Olson 2 4 , Paul Clem 3 , Julia Hsu 2
1 Electronic and Nanostructured Materials, Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 Surface and Interface Sciences, Sandia National Laboratories, Albuquerque, New Mexico, United States, 4 , National Renewable Energy Laboratory, Golden, Colorado, United States, 3 Microsystem Materials, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractContinued development of designer inorganic materials for modern electronics applications has produced an exciting array of materials with engineered properties such as band gaps, electrical conductivities, optical properties and morphology. While many of these materials are of interest in their own right, combining these materials into composites can produce new, functional behavior and enhanced optoelectronic performance. In the present work, we focus on a specific example of this idea, employing a simple, solution-phase process to create nanostructured composites of cadmium sulfide (CdS) and zinc oxide (ZnO). This process relies on the careful selection of reaction precursors to produce controlled, selective growth of CdS on ZnO. The selectivity and solution-phase nature of the growth process allow us to apply this process to a diverse set of ZnO nanostructured films ranging from planar films to complex extended films of branched ZnO architectures and patterned nanorods. While CdS and ZnO are wide band gap semiconductors commonly found in photovoltaic systems such as CIGS solar cells, our simple, solution phase growth process has allowed us to incorporate this composite material into less conventional hybrid organic/inorganic solar cells with promising results. In particular, we have observed improvements in critical metrics such as open circuit voltage, fill factor, and overall device efficiency when compared to control devices employing ZnO alone. Finally, the chemical flexibility of ZnO and CdS and the solution-phase growth enable us to explore further tailoring of this functional system by doping, alloying, or capping each component to modify overall composite properties. This exciting composite system represents a promising application of simple, solution-based chemistry to produce functional materials for the next generation of optoelectronic applications. 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.
F8: Bath-Based Deposition and Liquid Precursor Routes
Session Chairs
Jean François Guillemoles
Thursday PM, December 04, 2008
Room 208 (Hynes)
2:30 PM - **F8.1
Some Sources of Irreproducibility in Chemical Bath Deposition.
Michael Kokotov 1 , Gary Hodes 1
1 Materials and Interfaces, Weizmann Institute of Science, Rehovot Israel
Show AbstractChemical bath deposition (CBD) is a conceptually very simple method of deposition requiring a minimum of setting up. However, while some depositions can be reliably repeated, there are others where different groups (and not rarely, even the same group) cannot repeat the results of others.Here we focus on factors that affect nucleation of CBD films and give examples that can explain major differences in deposition from what might appear to be identical deposition procedures.The first is the importance of impurities in the deposition bath and how these impurities can promote deposition. In the deposition of ZnO from an ammonia/ethanolamine (EA) bath, it was noted that a particular bottle of EA, which was later found to contain 15 ppm Fe as impurity, gave reproducible films of ZnO nanorods on bare glass (usually, a seed layer is predeposited on glass prior to ZnO deposited from an alkaline solution). In the absence of the impurity, little or no ZnO deposition occurred. This could be explained by the formation of FeOOH nuclei which act as nucleation centres for ZnO growth. Mn salts work as well or, in some cases, even better than Fe salts.A second factor for deposition on glass is the nature of the glass surface. This is particularly marked for glass slides made by the float glass method, where molten glass flows over a molten tin bed and some of the tin is incorporated into the glass. The side of the glass containing tin has been found to enhance nucleation for depositions where heterogeneous nucleation (ion-by-ion mechanism) rather than homogeneous nucleation of colloids in solution (cluster mechanism) occurs. We present examples of ZnO, CdSe and CdS deposition where deposition occurs only on the tin-containing side of the float glass.Finally, we note that ammonia, a common reagent in CBD processes, becomes less concentrated with use (repeated opening of the reagent bottle), and this can typically amount to a 25% or more reduction in concentration over the life of the bottle. These concentration changes may be critical in some depositions and should be taken into account.
3:00 PM - F8.2
Investigate the Reacting Flux of Chemical Bath Depostion by a Continuous Flow Microreactor.
Yu-Jen Chang 1 , Yu-Wei Su 1 , Seung-Yeol Han 1 , Gregory Herman 2 , Chih-hung Chang 1
1 Chemical Engineering, Oregon State University, Corvallis, Oregon, United States, 2 , Sharp Laboratories of America , Camas, Washington, United States
Show AbstractChemical bath deposition also called chemical solution deposition has wildly been used to deposit compound semiconductor thin films owing to its low cost and low temperature processing nature which is suitable for fabricating low-cost large area thin film electronics. Though CBD has many advantages, it suffers from some drawbacks. In case of a batch CBD process, the heat needed for chemical reaction is supplied from the solution bath to the sample surface, resulting in both heterogeneous nucleation at the surface as well as homogeneous particle formation in the bath. The growth solution changes as a function of time and results in the difficulty of thickness control. The depletion of reactants also limits the achievable thickness. Moreover, the unequal bath-to-surface volume used to form the desired thin film generates a lot of waste and creates defects in devices. For a better understanding and optimization the CBD processes, it is necessary to find a method to de-couple the the homogeneous particle formation and deposition from the molecular level heterogeneous surface reaction. We have developved a continuous flow microreactor to achieve this goal. This reactor also provides opportunity to elucidate the growth mechanism that is not achievable from a conventional batch reactor. In this talk, I will report the benefits of using this reactor to deposit functional thin films.
3:15 PM - F8.3
Electrochemical Deposition of (In,Ga)-Se Thin Films.
Serdar Aksu 1 , Jiaxiong Wang 1 , Bulent Basol 1
1 , SoloPower, Inc., San Jose, California, United States
Show AbstractCu(In,Ga)Se2 (CIGS) is one of the most advanced absorber materials for thin film solar cells due to its direct bandgap, high absorption coefficient and ability to yield good quality devices. CIGS-based solar cells have yielded the highest conversion efficiencies of all thin film solar cells, reaching up to about 20%. One technique used to form CIGS layers is a two-stage approach which involves deposition of a precursor layer on a substrate followed by a high temperature activation step that converts the precursor layer into solar cell grade CIGS. The precursor layers employed in a two stage process may be in the form of stacks comprising at least Cu, In and Ga. Some examples of such stacks are Cu-Ga/In/Se, Cu/Ga-Se/In-Se, Cu-Se/In-Se/Ga-Se, etc. Although various techniques such as evaporation and sputtering have been employed to prepare precursor layers for CIGS film formation electrodeposition is especially attractive due its low cost, efficient utilization of raw materials and scalability to high-volume manufacturing. (In,Ga)Se electrodeposition and its possible application to solar cells have been previously studied. Most of these studies, however, concentrated on acidic electrolyte compositions. In this study, we present our results on the electrochemical co-deposition of indium (In) with selenium (Se) and gallium with Se to plate high-quality In-Se and Ga-Se films from aqueous alkaline electroplating solutions containing complexing agents. This way full potential of complexation could be utilized for the first time. Complexing agents were used to solubilize In and Ga ions at high pH regime and bring their reduction potentials down, closer to that of Se reduction potential. Since no complexation occurs between Se and the complexing agents, Se reduction potential could be independently controlled by the amount of dissolved Se. Tartrate and citrate were determined as suitable complexing agents for In and Ga, respectively. By optimizing the concentrations of metal salt, complexing agent, the selenium source, pH and the electrodeposition current density, it was possible to obtain adherent and smooth In-Se and Ga-Se films with high repeatability and controllable molar ratios of In/Se and Ga/Se.
4:30 PM - F8.5
Electrodeposition of Nanostructured ZnO on Textile Electrodes - a New Starting Point Towards Flexible Low-Cost Photovoltaics.
Thomas Loewenstein 1 , Markus Mingebach 1 , Andreas Hastall 1 , Melanie Rudolph 1 , Yvonne Zimmermann 2 , Andreas Neudeck 2 , Derck Schlettwein 1
1 Institute of Applied Physics, Justus-Liebig-University Giessen, Giessen Germany, 2 , Textile Research Institute Thuringia-Vogtland, Greiz Germany
Show AbstractThin porous films of ZnO were deposited on metal- coated polyamide threads, filaments and knitted fabrics as a first step towards textile- based photovoltaics. Textiles are well known as flexible, mechanically rugged and lightweight materials. Over the last years electronics have been more and more integrated into textiles, mainly for sensing purposes. Interest rose to also integrate an independent energy supply, namely photovoltaics. Because of the attractive mechanical properties, textile- integrated photovoltaics are of interest for a number of outdoor activities. Preparation of semiconductor films from precursor solutions represents the most promising approach because of good compatibility of the processes to a low thermal stability of textiles and to the need of a three- dimensional coating process. In this contribution we will discuss the results of electrodeposition of porous ZnO films. Crystalline ZnO was prepared in a cathodic electrodeposition reaction induced by oxygen reduction in an aqueous electrolyte in the presence of Zn2+. Individual fibers showed characteristics of microelectrodes and hence increased deposition rates were obtained relative to traditional planar electrodes. Nevertheless the hydrodynamic flow played a significant role and an optimization is needed in particular for the coating of threads and knitted fabrics. Materials were formed that show photovoltaic activity in dye- sensitized photovoltaic cells. The porous network needed for this purpose was provided by addition of molecular adsorbates to the deposition bath as structure- directing agents (SDA). First sensitization studies will be presented to show the feasibility of the chosen approach, but also indicate the need for further optimization to suppress recombination and back transfer of injected electrons.
4:45 PM - F8.6
A Simple, Low-Cost Approach to Selective Metal Deposition on Polymeric Substrates.
Tricia Carmichael 1 , Gregory Davidson 1 , Michael Miller 1
1 , University of Windsor , Windsor, Ontario, Canada
Show AbstractWe present a general, low-cost method based on soft lithography and electroless metallization to form patterned metal films on polymeric substrates. We have demonstrated this process on flexible polymers such as poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN), and polyimide (PI), rigid polymers such as the epoxy-based photoresist SU-8 and poly(methyl methacrylate) (PMMA), and polymers with low-energy surfaces such as polyethylene (PE), polypropylene (PP), and poly(tetrafluoroethylene) (PTFE). The process begins with the solution-based oxidation of the polymeric substrate to generate carboxylic acid groups at the surface. Selected regions of the oxidized surface are then made active for metal deposition by microcontact printing an aluminum (III) porphyrin bearing an axial methoxy ligand. The aluminum porphyrin reacts with the carboxylic acid groups on the surface by liberating methanol and forming a covalent aluminum carboxylate linkage to the surface. These surface-attached groups then bind a palladium-tin colloidal catalyst that initiates selective electroless plating on the surface. This new method for the production of patterned metal/polymer composites is important to advance the fabrication of electronic devices such as lightweight, flexible displays and wearable electronics, and rigid devices such as microactuators, electrochemical detectors, and radio frequency conductors for microelectromechanical systems.
5:00 PM - F8.7
Liquid Silane Routes to Electronic Materials.
Douglas Schulz 1 2 , Xuliang Dai 1 , Kendric Nelson 1 , Konstantin Pokhodnya 1 3 , Justin Hoey 1 2 , Iskander Akhatov 2 1 , Orven Swenson 3 1 , Philip Boudjouk 1
1 Center for Nanoscale Science and Engineering, North Dakota State University, Fargo, North Dakota, United States, 2 Mechanical Engineering and Applied Mechanics, North Dakota State University, Fargo, North Dakota, United States, 3 Physics, North Dakota State University, Fargo, North Dakota, United States
Show AbstractNew chemistries based upon liquid cyclohexasilane (Si6H12 or CHS) have been used as precursors to silicon-containing electronic materials. Spin-coating of CHS-based inks with subsequent UV light and/or thermal treatment yielded amorphous silicon (a-Si:H) films. While initial ink chemistries gave a-Si:H with high resistivity (i.e., > 106 Ω.cm) [1], several doping strategies are under development to address this limitation. In this contribution, the current status of solution processed rectifying diodes and field effect transistors fabricated from CHS-based inks will be presented. Additionally, a new printing approach termed collimated aerosol beam direct write (CAB-DWTM) was developed that allows the deposition of printed Ag lines 5 μm in width [2]. A status update will be given where CHS-based inks have been used to CAB-DW silicon-based features with linewidths <10 μm. Assuming silicon thin film materials with good electrical properties will be developed, there may be significant cost advantages associated with the ability to controllably deposit the semiconductor in a metered fashion. Citations [1] Han, S.; Dai, X.; Loy, P.; Lovaasen, J.; Huether, J.; Hoey, J.M.; Wagner, A.; Sandstrom, J.; Bunzow, D.; Swenson, O.F.; Akhatov, I.S.; Schulz, D.L. "Printed Silicon as Diode and FET Materials - Preliminary Results", J. Non-Cryst. Solids, 2008, 354, 2623-2626.[2] Akhatov, I.S.; Hoey, J.M.; Swenson, O.F.; Schulz, D.L. "Aerosol Flow through a Long Micro-capillary: Collimated Aerosol Beam", Microfluid. Nanofluid., (2008) doi:10.1007/s10404-007-0239-3. AcknowledgementsThis material is based on research sponsored by the National Science Foundation through ND EPSCoR grant EP-0447679 and the Defense Microelectronics Activity under agreement number H94003-06-2-0601. The United States Government is authorized to reproduce and distribute reprints for government purposes, notwithstanding any copyright notation thereon.
5:15 PM - F8.8
Organosoluble Silicon And Germanium Nanoclusters.
Akira Watanabe 1 , Tokuji Miyashita 1
1 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai Japan
Show Abstract5:30 PM - **F8.9
Polymer-assisted Deposition of Thin Films.
Anthony Burrell 1 , Hongmei Luo 1 , Eve Bauer 1 , Mark McCleskey 1 , Quanxi Jia 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractF9: Poster Session: PV, Chem Bath and Printing
Session Chairs
Friday AM, December 05, 2008
Exhibition Hall D (Hynes)
9:00 PM - F9.1
Synthesis of InGaZnO4 Colloids and Its Application in a TFT Device.
Kan-Sen Chou 1 , Chen-Yu Kao 1 , Ya-Hui Yang 2 , Sidney, S. Yang 2
1 Chemical Engineering, National Tsing Hua University, Hsinchu Taiwan, 2 Electrical Engineering, National Tsing Hua University, Hsinchu Taiwan
Show AbstractFlexible electronics is becoming the focus of intense research in recent years. In theory, it can be produced by continuous and high speed printing technique. Therefore, it has the advantages of being flexible, lightweight, impact resistant and low cost. The TFT devices with amorphous In-Ga-Zn oxide (a-TGZO) channel layer deposited by PVD techniques showed a high mobility (> 10 cm2/V-s), as compared with polycrystalline ZnO layer in the literature. The purpose of this work is to demonstrate the realization of IGZO TFT channel layer obtained by a solution process, which offers a simple and low-cost alternative to vacuum deposition process. Here we will first prepare an ink containing IGZO nanoparticles, synthesized under hydrothermal conditions. The ink will then be deposited as the channel layer to complete the TFT structure for property measurements. The composition of IGZO is fixed at In:Ga:Zn = 1:1:1 in this work. The solution which contains 0.001 mole of each indium nitrate, gallium nitrate and zinc nitrate and 250 ml DI water, is mixed with another solution containing 0.008 mole NH4OH and 250 ml DI water under constant stirring. The co-precipitated material was separated from the solution by centrifuge and washed three times by DI water to remove residual ions. The gel was then heated in an autoclave at 200oC for one hour to obtain crystalline IGZO particles. To get the IGZO ink, the nanoparticles (1 part) was dispersed in DI water (10 part) using CMC (0.1 part) as the dispersant. The mixture was treated by ultrasound for 30 minutes to obtain a stable suspension with solid content of about 9wt% for future applications. As for the bottom-gate type TFT device, the IGZO nanoparticles was used as the channel layer. On a glass substrate, the NiCr of about 100 nm was first deposited by sputtering and defined by a mask to form the gate. Next, an 84 nm silica layer was deposited as the gate insulator. Finally, the source and drain electrode were made by sputter coating 300 nm Au layer. The channel width and length were 210 and 75 micron respectively, yielding a design width-to-length ratio of 2.8 for this case. The IGZO ink was then dripped into the channel region and dried in an oven at 70oC. A 250oC, 1 hr annealing process was also used in this study. The I-V characteristics of this TFT device were measured by Agilent 4155 C. The IDS is 0.32 mA at VGS = 15 V. The leakage current made by the current procedure is rather large with I (on/off) = 1.4. This large leakage current may very well caused by the excessive active layer. A cross section picture of the deposited layer showed that the layer was porous and had a thickness of about 1.35 micron, which was much too thick than desired. Next, the effect of solid content of the ink will be investigated in an attempt to reduce the thickness of the active layer to improve the performance of the TFT device. An optimal procedure will be established.
9:00 PM - F9.10
The Preparation of Silver Nanoparticle Inks for Ink-Jet Printing.
Sung Yeon Cho 1 , Jeong Hyeon Na 1 , Ji Yun Park 1 , Jin Chul Park 1 , Sang Man Koo 1
1 Chemical Engineering, Hanyang University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - F9.11
Roll-to-Roll Printed Rectifier for Providing DC 10V to 13.56 MHz Printed RFID Tags.
Gyoujin Cho 1 , Namsu Lim 2 , Joonseok Kim 1 , Jaeyoung Kim 2
1 School of Applied Materials, Sunchon National University, Sunchon, Jeonnam, Korea (the Republic of), 2 Printed Electronics Research Institute, PARU Co, Sunchon, Jeonnam, Korea (the Republic of)
Show AbstractPrinted electronics will be an only pathway toward the mass production of ultralow-cost RFID tags for item-level tracking of consumer goods. Here, we would like to report our current progress in developing printed rectifying diodes to provide DC power on printed RFID Tag through rectifying the AC voltage induced in the printed RF antenna and convert it into DC voltage that is capable of providing the DC power to the logic circuit printed on the tag. In this presentation, we would like to show a way to print the rectifying diodes that can provide DC 10 V at 13.56 MHz AC using various printing methods such as the inkjet, gravure, and pad printing with ZnO hybrid semiconducting ink.
9:00 PM - F9.12
Conductive Ink for Roll to Roll Gravure Printing Gate Electrodes on PET Foils.
Gyoujin Cho 1 2 , Chaemin Lim 1 2 , Heewon Kang 2 , Dongsun Yeom 2
1 School of Applied Materials, Sunchon National University, Sunchon, Jeonnam, Korea (the Republic of), 2 Printed Electronic Research Institute, PARU Co., Sunchon, Jeonnam, Korea (the Republic of)
Show AbstractPrinted electronics will be a key technology in the near future in the field of macroelectronics. In the practical purpose, roll to roll printing technology will be a key technology especially for ultra-low cost RFID tags and printed flexible displays. Among the devices in the ultra-low cost RFID tags and the printed flexible displays, roll to roll printed thin film transistors (TFTs) are the key devices to be provided with the most priority. To completely roll to roll print TFTs with stable and reliable electrical performances with lower power consumption, lower surface roughness and fine resolution of printed gate electrodes are key factors to be controlled first. In this presentation, we would like to show how the surface roughness and fine resolutions of roll to roll gravure printed gate electrodes can be controlled by changing size and polydispersity of silver nano-particles in the conductive ink while surface tension and viscosity of the inks are systematically changed with the constant roll pressure and web speed of the gravure printer.
9:00 PM - F9.13
Anti-Reflection and High-Reflection Optical Thin Films Based on Dip Coating of Inorganic Particles.
Yuehui Wang 1 2 , Li Chen 1 , Hongjun Yang 1 , Qing Guo 3 , Weidong Zhou 1 , Meng Tao 1 3
1 Electrical Engineering, University of Texas at Arlington, Arlington, Texas, United States, 2 Department of Chemistry and Biology, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan, Guangzhou, China, 3 , ZT Solar, Inc., Fort Worth, Texas, United States
Show Abstract9:00 PM - F9.14
Direct-Write Assembly of Micro-Periodic Sn-doped In2O3 (ITO) Structures.
Bok Ahn 1 2 , David Lorang 1 2 , Eric Duoss 1 2 , Jennifer Lewis 1 2
1 Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractMicro-periodic patterns of Sn-doped In2O3 (ITO) are used extensively as a transparent semiconductor element in a broad array of technological applications, including displays, sensors, solar cells, and photonic crystals. Here, we demonstrate the assembly of micro-periodic, two-dimensional (2-D) and three-dimensional (3-D) structures via direct ink writing (DIW). A concentrated sol-gel ink is produced by mixing indium acetate and tin bis(acetylacetonate) dichloride precursors in an acetylacetone solvent. This ink is then extruded through fine deposition nozzle (1 μm in diameter) and the desired structures are patterned in a layer-by-layer build sequence. The morphology, optical, and electrical properties of the ITO-based structures are characterized after calcining to 600°C.
9:00 PM - F9.15
Low Temperature Solution-Based Fabrications of Metal Oxide Semiconductor Films by Mechanical Sintering.
Manabu Yoshida 1 , Kouji Suemori 1 , Sei Uemura 1 , Satoshi Hoshino 1 , Noriyuki Takada 1 , Takehito Kodzasa 1 , Toshihide Kamata 1
1 Organic Semiconductor Device Research Group, National Institute of Advanced Science and Technology, Tsukuba, Ibaraki, Japan
Show AbstractVarious flexible electronic devices have been intensively studied and developed in this decade. Most consumers expect to obtain these flexible electronic devices in the next decade. The spread of flexible electronic devices depends on the process costs and material costs. Today prices of materials and energy sources are continuously increasing. Therefore, using of expensive materials and wasteful processes for fabricating electronic devices should be reconsidered. Printing techniques, a representative solution process, are inexpensive and very effective for mass production of electronic devices. We have developed a low-temperature process for fabricating flexible printed patterns of metals and semiconductors by using relatively inexpensive commercial pastes. A characteristic of our process is to utilize mechanical energies for sintering particles contained in pastes. In our process, the precise three-dimensional pressure control brings about the improvement of electrical properties in the printed patterns, the preservation of pattern accuracy and the mechanical durability of the printed patterns. In our experiments, we have already fabricated very low resistivity metal patterns (about 6x10^-6Ωcm) at ca.120°C without using any kinds of nano-particle paste, and also fabricated metal oxide semiconductor patterns. *This work is supported by Industrial Technology Research Grant Program in 2008 from New Energy and Industrial Technology Development Organization (NEDO) of Japan.
9:00 PM - F9.17
Properties of Alumina Dielectrics Prepared by Ink Jet Process.
Eunhae Koo 1 , Jong Hee Kim 1
1 Division of Fusion and Convergence Technology, Korea Institute of Ceramic Engineering & Technology, Seoul Korea (the Republic of)
Show AbstractLow loss dielectrics below 10 μm have been fabricated on Si wafer via ink jet process. Alumina suspensions as a dielectric ink were formulated with alumina powder and an anionic polymer dispersants in formamide/water. Alumina powders of the size of 0.2, 0.3, and 0.54 μm were used, respectively. The microstructure was investigated by field emission scanning electron microscope (FE-SEM). We also calculated the alumina packing density of dielectric layer using 0.2, 0.3, and 0.54 μm alumina inks. The volume fraction of alumina of the dielectric layer by ink-jet process is about 65% much higher than that of the dielectric of around 40% fabricated by a conventional wet casting method. Furthermore, the permittivity and Q factor of the dielectrics infiltrated by polymers such as epoxy and PPO were evaluated by impedance analyzer. The results suggest that the dielectrics with high Q value and dimensional stability can be used for high speed electronic applications
9:00 PM - F9.18
Printing Inorganic and Inorganic/Organic Hybrid Materials using Piezoelectric Printing.
Jan Sumerel 1 , Leila Deravi 2 , David Wright 2
1 , FUJIFILM Dimatix, Santa Clara, California, United States, 2 Chemistry, Vanderbilt University, Nashville, Tennessee, United States
Show AbstractPiezoelectric inkjet printing is an attractive technique due to its just push print feature where the ink is deposited as a thinfilm according to a digital image file where film thickness is directly related to contact angle. In addition, when using fluids that impart functionality, the printed features impart function themselves. While it has been determined that printed electronics and printed voltaic materials are both potentially billion dollar markets, the need for formulation of fluids containing inorganic or inorganic/organic hybrid particles that are capable of doing work is still one of the gatekeepers of process adaptation for this deposition technique. In addition, as printhead developers produce smaller and smaller nozzle dimensions on the ink jets, formulation becomes even more paramount. We have developed the first 1 pL printhead suitable for a large variety of chemistries often used in functional fluid development. Functional fluid printing using this printhead produces features that are less than 23 um. We have used a large variety of silver nanoparticle “inks” where the the nanoparticles have been stabilized with a thin organic layer. Upon annealing at low temperatures, these patterned thinfilms are conductive. We will show printed thinfilms both directly after printing and after annealing. We will show their electrical properties. In addition, we will show the deposition of quantum dots and their optical properties. Finally, we will show how to pattern condensed silicon dioxide as a thinfilm using a dendrimeric template and triethoxysilane. We will show that the mesoscale properties of these 3D silicon dioxide patterns are directly related to the patterned dendrimer. In conclusion, we will show whether these patterned glass materials are dielectric.
9:00 PM - F9.19
New Methodology of Microstructure Evolution of Inkjet Printed Ag Film and its Corresponding Properties.
Seol-Min Yi 1 , Ji-Hoon Lee 1 , Ho-Young Lee 1 , Inyoung Kim 2 , Hyun Chul Jung 2 , Jaewoo Joung 2 , Young-Chang Joo 1
1 School of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 2 Central R&D Institute, Samsung Electro-Mechanics, Suwon Korea (the Republic of)
Show AbstractInkjet printing technology is an alternative way to enable low-cost device fabrication. This technology has advantages in fabrication of large-area and flexible devices with roll-to-roll process. Metal interconnect can be formed without complicated and wasteful lithographic processes by this technology. However, this inkjet printed film/line has poorer properties in comparing to vapor-deposited film until now. This printed film has small grain size, grain structure like a stack of nanoparticles, and pores because of nature of metal ink – ink is consisted of metal nanoparticles and organic additives. The organic molecules in the printed film interrupt grain growth and electron current, resulting poor electrical and mechanical properties of inkjet printed film. From our previous results, coarsening of inkjet printed Ag film occurs after the decomposition of organic molecules. These organic molecules decomposed in proper conditions – high temperature, ambient air [1]. Based on these results, we tried to induce grain growth by controlling ambient in order to achieve better properties in this study. Holding inkjet printed Ag film under vacuum, temperature increases to 250 oC. At that moment, ambient air is injected into the chamber in order to induce rapid decomposition of the organic molecules. The films annealed isothermally for various time (10 - 120 min) after injection of air. Grain size and surface morphology of films were observed by field-emission secondary electron microscope (FE-SEM). Cross-sectional image also observed by focused ion beam (FIB) analysis, and film thickness was measured from this image. Electrical resistivity was measured by 4 point probe and mechanical properties (yield strength, ultimate tensile stress, etc.) were measured from tensile test. From the FE-SEM images, coarsening/grain growth was observed as anneal time increases. Median grain size increases and bimodal grain size distribution was observed. The diameter of the largest grain is five times of median grain size after annealing for 60 min. Electrical resistivity also decreases and it is lower than conventional annealing (whole process conducts under air). In observing cross-sectional images, microstructure depends on film thickness. Thin film (~4 μm) shows only dense and coarse microstructure while thick film (~8 μm) has coarse microstructure near the surface and loose microstructure near the bottom of film. The effect of this dense and coarse microstructure also discussed.[1] J.-K. Jung et al., Philosophical Magazine 88 (3), 339-359 (2008).
9:00 PM - F9.2
Effect of UV Light and CNT Dopant on Solution-based IGZO TFTs.
Keunwoo Lee 1 , Kony-Yi Heo 1 , Sang-Hoon Oh 1 , Abderrafia Moujoud 1 , Hyun-Jae Kim 1
1 School of Electrical & Electronic Engineering, Yonsei University , Seoul Korea (the Republic of)
Show AbstractWe studied the optical and electrical properties of sputtered indium gallium zinc oxide (IGZO) TFTs, solution-based IGZO TFTs, and solution-based IGZO/carbon nanotubes (CNTs) TFTs.Intrinsic optical properties such as optical band gap and transmittance of the IGZO films, and TFT’s characteristics under UV illumination are investigated. Without the UV illumination we found out the following electrical properties: For sputtered-IGZO TFTs, the threshold voltage was 1.88 V, field effect mobility of about 7.8 cm2V-1s-1, subthreshold swing of 0.82 V/decade, and on/off ratio over 10^8. In case of solution-based IGZO TFTs, threshold voltage of 7.38 V, field effect mobility of about 0.02 cm2V-1s-1, subthreshold swing of 4.7 V/decade, and on/off ratio over 10^4. In case of solution-based IGZO/CNT TFTs, threshold voltage of -0.04 V, field effect mobility of about 0.17 cm2V-1s-1, subthreshold swing of 1.34 V/decade, and on/off ratio over 10^5.With the UV illumination at the wavelength of 355 nm, the off-state drain current of the sputtered IGZO-TFT increased by four orders. While in the case of solution-based IGZO and solution-based IGZO/CNT TFTs the off-state drain current increased drastically and reach saturation. After removing UV illumination, we observed that the off-state drain current of all TFTs recovered to their initial state. However, in the case of IGZO/CNT TFTs the recovery time is longer (about 13 hours). This longer recovery time is due to the presence of CNT in the solution.Threshold voltage, subthreshold swing, and field effect mobility of all TFTs were also measured during UV illumination and they changed significantly. The solution-based IGZO TFTs and solution-based IGZO/CNT TFTs are more sensitive to UV illumination than sputtered-IGZO TFTs. The observed results are consistent with optical energy band gap. Sputtered-IGZO TFTs optical energy band gap is well known and it is about 3.05 eV1) . We measured the optical energy band gap of solution-based IGZO TFTs, it is about 3.5 eV and for the solution-based IGZO/CNT TFTs the optical energy band gap is about 4.0 eV. These studies suggest that TFTs with larger energy band gap is more sensitive to UV wavelength of 355 nm and the presence of CNT in the solution could control the off-state drain current recovery time. We conclude that our solution-based IGZO/CNT TFTs and solution-based IGZO TFTs can be a good UV photodetecting device. Our results also indicate that these materials are light sensitive when the band gap is above 3.5eV.Reference1)C.S Chuang, T.C.Fung,K.Nomura,B.G.Mullins,H.P.D. Sheih,H.Hosono and J.Kanicki “Photosensitivity of the amorphous IGZO TFTs for active-Matrix Flat Panel Display” SID 08,453 (2008)
9:00 PM - F9.20
TiO2 Nanotube Arrays by using ZnO Nanorod Template through Liquid Phase Deposition for Organic- Inorganic Hybrid Photovoltaic Cells.
Thitima Rattanavoravipa 1 , Takashi Sagawa 1 , Susumu Yoshikawa 1
1 , Institute of Advance energy, Kyoto University, Kyoto Japan
Show AbstractOver the past decade, organic photovoltaic devices attracted enormously due to some advantages of these materials over traditional inorganic semiconductor. Hybrid organic-inorganic photovoltaic cells combine the unique advantage of both organic and inorganic properties. The first report of fabrication of organic-inorganic hybrid structure for solar cells included bilayer devices of polyacetylene and inorganic crystals. In this study, TiO2 has been selected as electron acceptor and transport material and conjugated polymer P3HT blended with PCBM fullerene to achieve the bulk heterojunction polymer have been selected as organic materials. Based on nanorod arrays structure, well aligned TiO2 nanotube arrays are able to act as both electron acceptor and electron transporter to the electrode which can be attributed to increase of the interfacial area for charge acceptance and separation from donor material due to the diffusion length of the excitons in a semiconducting polymer is relatively short. In order to make the process and efficiency easier and higher, we report herein the simple and controllable fabrication of nanotube arrays though liquid phase deposition of TiO2 by using ZnO nanorod as the template and its application to the electron transporting layer for hybrid organic-inorganic solar cells with FTO/nanotube arrays TiO2/dye molecule/P3HT:PCBM/Au structure. The surface modification of the metal oxide with several types of dyes, such as N719, NKX-2677, D149, and Eosin-Y improved the solar cell performance in terms of both Jsc and Voc. Improvement of the interfacial contact between the organic layer and the electron transporting layer may improve the efficiency of electron transfer because the wettability of the surface of TiO2 nanotubes was remarkably increased against the P3HT:PCBM blend solution. In particular, the cell by using the TiO2 nanotube arrays with N719 attained relatively large values of Jsc of 5.7 mW/cm2 and η of 0.656%. On the contrary, un-modified cell demonstrated the Jsc of 1.1 mW/cm2 and η of 0.02%
9:00 PM - F9.21
Development of Embedded Capacitors Using Titania and Barium Titanate Thin Films Grown from Electrodeposition.
Biplab Roy 1 , Guangneng Zhang 1 , Roy Magnuson 2 , Mark Poliks 2 , Junghyun Cho 1
1 Department of Mechanical Engineering & Program of Materials Science and Engineering, State University of New York at Binghamton, Binghamton, New York, United States, 2 , Endicott Interconnect Technologies, Inc., Endicott, New York, United States
Show AbstractElectronic circuit boards require an embedding passive technology for further miniaturization and enhanced performance. A low-temperature, low-cost process to embed a dielectric layer inside the substrate is needed in this technology. To achieve this, deposition of high-k ceramic layer on Cu substrates has been developed from a solution based method while ensuring the protection of copper from corrosion of adverse solution condition. In particular, deposition of titania films was carried out through electrodeposition from a peroxotitanate solution prepared in a mixed solvent (water and methanol). A cathodic bias, determined from thermodynamic calculations, was applied to the metallic substrate to render protection against corrosion during deposition. The resultant titania films show high dielectric constant (> 31 @ 100 kHz ), high capacitance density (> 90nF/in2 @ 100 kHz) and low dielectric loss (< 0.004 @100 kHz). For further improvement of dielectric performance, titania films obtained through electrodeposition were treated for conversion to barium titanate by heating them in a high pH barium ion containing solution with suitable cathodic protection applied to copper. Dielectric properties measured from both titania and barium titanate films exhibited much improved performance, compared to current embedded ceramic-loaded polymer capacitors, thereby showing a great potential in embedded capacitor applications. In this presentation, detailed processing protocols and associated microstructure developments will also be addressed to provide a clear insight of the deposition mechanisms.
9:00 PM - F9.22
Solution Processing of CIGS Absorber Layers for PV Application.
Min Yuan 1 , David Mitzi 1 , Wei Liu 1 , Andrew Kellock 2 , Jay Chey 1 , Vaughn Deline 2 , Lynne Gignac 1
1 , IBM T. J. Watson Research Center, Yorktown Heights, New York, United States, 2 , IBM Almaden Research Center, San Jose, California, United States
Show Abstract9:00 PM - F9.24
Synthesize and Characterization of Highly Transparent Sol Gel Glass for Photovoltaic Applications.
Mariyappan Shanmugam 1 , Mahdi Farrokh Baroughi 1 , XingZhong Yan 1 , David Galipeau 1
1 Electrical Engineering and Computer Science, South Dakota State University, Brookings, South Dakota, United States
Show Abstract9:00 PM - F9.25
Silicon Oxide Composite Film Fabricated by Wet-Process at Low Temperature as a Passivation Layer for Printable Electric Device.
Sei Uemura 1 , Kouji Suemori 1 , Manabu Yoshida 1 , Satoshi Hoshino 1 , Noriyuki Takada 1 , Takehito Kodzasa 1 , Toshihide Kamata 1
1 Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki Japan
Show AbstractPrinting techniques for electric materials such as semiconductor, dielectric, and electrode have been studied extensively from the standpoint of printable electric device. Printing process is demonstrated ability to the full when all vacuum processes in device fabrication are replaced by solution processes. However, promising preparation techniques have not been appeared because passivation layer fabricated by solution processes have not yet reached satisfactory performances. One of the important performances of passivation layer is permeability barrier to moisture. Since most printable semiconductors such as organic material and/or electrode are damaged by moisture, the device driven in the presence of moisture shows unstable electric property and short lifetime. In most printable electric device, permeability of moisture into the device permitted is less than 10mg/m2day. In the case of organic light emitting diode, low permeability is particularly necessary, i.e., 1μg/m2 day. Such high performance has not yet obtained in passivation film produced by solution process. We have reported about a preparation method of silicon oxide by solution process [1]. Silicon oxide film is produced by spin-coating film form a solvent containing silazane compound and was irradiated in the UV region. The silicon oxide film has electric resistivity more than 1e+15Ωcm and electric strength more than 7 MV/cm. In this paper, we applied the film to passivation layer for printable devices. Lowering of the process temperature and optimization of the reaction condition were investigated. Furthermore, nano-composite with silicon oxide and clay mineral was investigated in order to obtain high performance passivation film. [1] 2006 spring meeting of MRS
9:00 PM - F9.26
Improvement of Dielectric Strength of Solution Processed SiO2 Film using Photo-oxidation Process of Silazane Compounds.
Takehito Kodzasa 1 , Sei Uemura 1 , Toshihide Kamata 1
1 , AIST, Tsukuba, Ibaraki, Japan
Show AbstractIt has been often recognized that a SiO2 film prepared by solution process has relatively low dielectric strength. Sometimes, it does not show hard break down. It indicates that it is difficult to use it as an insulator film at high applied electric field. This dielectric property is insufficient as a dielectric layer for conventional devices. Therefore improvement of dielectric strength of the solution processed SiO2 film is strongly required.In order to improve the dielectric strength, it is necessary to prepare a close-grained SiO2 film. In this study, we have applied photo-oxidation process on the solution-based fabrication of a close-grained SiO2 film that shows high dielectric strength. As a precursor material, we used silazane compounds. It was dissolved in the 1,2-dichlorobenzene. The solution of the precursor materials was spread on a glass substrate by spin coating. The spread precursor film was photo-oxidized by UV-light irradiation under ozone gas. Photo-oxidation process reduced process temperature below 200 C. Such a low temperature deposition was effective to reduce stress damage during the film deposition. Furthermore, we have optimized molecular structure of precursor compound to reduce the stress damages during film deposition through photo-oxidation. During the oxidation of silazane compound into SiO2, displacement of N into O occurred. If the bond length between Si-N-Si and Si-O-Si was so much changed during the reaction, the film receives much stress damage. Therefore, bond length design of precursor materials was very important.Consequently, the maximum process temperature was below 180 C. The prepared SiO2 film showed hard break down at high applied voltage. Its dielectric strength was more than 8 MV/cm. In this presentation, we will discuss the relationship between stress damage effect and dielectric properties for the solution-processed SiO2 film.
9:00 PM - F9.27
In-situ Fabrication of Copper Nanoparticle Dispersed Conductive Ink.
Kun-Jae Lee 1 , Namwoo Kim 1 , Younghun Byun 2 , Sung-Jei Hong 3 , Je Hoon Oh 4 , Yong-Ho Choa 1
1 Functional Nanostructured Material Research Lab., Hanyang University, Ansan, Kyounggi, Korea (the Republic of), 2 Advanced Materials Lab., Samsung Advanced Institute of Technology, Yongin, Kyounggi, Korea (the Republic of), 3 Information Display Research Center, Korea Electronics Technology Institute, Seongnam, Kyounggi, Korea (the Republic of), 4 Mechanical Engineering, Hanyang University, Ansan, Kyounggi, Korea (the Republic of)
Show Abstract9:00 PM - F9.3
Study on Ionic Sensitivity of AgIn5S8 Thin Film for Extended Gate Field Effect Transistor.
Yan-Liang Ji 1 , Yi-Fang Chiang 1 , Chia-Feng Chang 1 , Yung-Sheng Lee 1 , Jing-Shun Chen 1 , Jiann-Ruey Chen 1
1 Materials Science and Engineering, National Tsing Hua University, Hsinchu Taiwan
Show AbstractRecently, extended gate field effect transistor (EGFET) had been studied as pH meter and biosensor. In this study, AgIn5S8 coated by hydrothermal method on ITO glass substrate was used as ionic-sensitive film in different concentration solutions of [H], [Cu2+] and [Pb2+]. Ionic sensitivities were measured by electrical properties under both NMOS and PMOS mode by linear and saturate range. The XRD and SEM analysis show highly crystalline and surface area with uniform reticulate texture. The ionic sensitivities of AgIn5S8 were 50.7mV/pH, 23.9mV/p[Cu2+], and 95.9mV/p[Pb2+] in NMOS-EGFET under applied bias-voltage 2.5V, and reliability are more than 0.9. Moreover, the selectivity defined by the ratio of sensitivity between [H+] and [Cu2+] of sulfide film were four times higher than oxide film.
9:00 PM - F9.4
Improvement of Electrochromic Properties of Ti and Nb Doped WO3 Thin Films.
Suvarna Bathe 1 , P. Patil 1 , Ravi Bathe 2
1 Department of Physics, Shivaji University, Kolhapur, Maharashtra, India, 2 , International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, Andra Pradesh, India
Show Abstract9:00 PM - F9.5
Combining Solution Methods to Produce Inorganic Extremely Thin Absorber (ETA) Solar Cells.
Olivia Niitsoo 1 , Miles Page 1 , Yafit Itzhaik 1 , David Cahen 1 , Gary Hodes 1
1 Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot Israel
Show AbstractExtremely Thin Absorber (ETA) solar cells are relatively recent entries in the quest for cheap photovoltaics. In an ETA cell, an ultra-thin light-absorbing layer is deposited on the large internal surface of a porous high band gap metal oxide semiconductor, and the empty volume of the oxide film is filled with a suitable transparent hole conductor. Here we combine solution deposition methods to outline a general process for fabricating low cost, all-solid-state ETA solar cells, applied to a variety of matrix (TiO2 or ZnO) and absorber (CdS, Cu2-xS, Sb2S3 and CdSe) materials. A sol-gel method is used to form dense TiO2 underlayers that serve as a substrate for a porous, high surface area TiO2 nanoparticle network that is spin-coated onto the dense layer. For ZnO-based solar cells, the underlayer is formed by spray pyrolysis, followed by chemical bath deposition (CBD) of ZnO nanowires. CBD was found most suitable for depositing CdS and Sb2S3 on TiO2, while electrodeposition was used for CdSe on ZnO, since it is known to result in a conformal coating. For Cu2-xS cells, we topotactically exchange CdS in an aqueous solution of Cu+ ions. A solution of CuSCN, the hole conductor, is then infiltrated into the cell matrix in a controlled manner, filling the pores until CuSCN covers the surface, by allowing the solvent to evaporate on a hotplate. Cells are completed by evaporating or sputtering a gold top contact.We briefly discuss the photovoltaic performance of these cells, focusing on the effects of the various preparation parameters. We have optimized the CBD parameters for some of the absorbers. The otherwise poor electronic behavior of the high-recombination absorber Cu2-xS was substantially improved by a chemical bath deposited Inx(OH)ySz recombination-reducing buffer layer between TiO2 and Cu2-xS.
9:00 PM - F9.6
Solution Processed MoS2 Thin Films for TFT Applications.
Shahrukh Khan 1 , Robert Dorner 2 , Kamil Klier 2 , Miltiadis Hatalis 1
1 Electrical Engineering, Lehigh University, Bethlehem, Pennsylvania, United States, 2 Chemistry, Lehigh University, Bethlehem, Pennsylvania, United States
Show Abstract9:00 PM - F9.7
Effects of Cu/In Ratio on Electrical and Optical Characteristics of Spin-Coated CuInSe2 Thin Films.
Ik Jin Choi 1 , Bhaskar Mohanty 1 , Deuk Ho Yeon 1 , Yeon Hwa Jo 1 , Yong Soo Cho 1
1 Materials science and engineering, Yonsei University , Seoul Korea (the Republic of)
Show AbstractPolycrystalline thin films of CuInSe2 have been deposited by a spin coating technique. We have studied the chemical composition, the electrical, the optical, and the structural properties of CuInSe2 thin films. These films were deposited starting form mixed aqueous solutions with different chemical compositions ([Cu]/[In] ratio) and a different annealing temperatures. It has been found chalcopyrite structure with the lattice parameter with a = 5.28Å , c = 11.45 Å at composition of [Cu]/[In] ratio = 0.95. The grain size of all composition were measured form XRD and SEM was varied in between 450 and 700nm. The electro-optical properties show a strong dependence on [Cu]/[In] ratio in the solution. The absorption coefficient has been calculated in the range of 10-4cm-1 at the absorption edge for each composition with band gap which is varied from 1.05 to 1.65eV. The results in this work provided an improved process for producing a light absorbing chalcopyrite film, which process is suitable for the mass production of homogeneous and large scale light absorbing films.
9:00 PM - F9.8
Chemically Deposited Thin Films of Antimony Selenide for Solar Cell Applications.
M. T. Santhamma Nair 1 , Sarah Messina 1 , Enue Barrios 1 , P. Karunakaran Nair 1
1 Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Temixco, Morelos, Mexico
Show AbstractThin films of antimony selenide/oxide obtained from chemical baths containing soluble complexes of tartrato-, citrato-, or thiosulfatoantimonates and sodium selenosulfate require heating in presence of selenium to produce polycrystalline orthorhombic Sb2Se3. Such films show an indirect bandgap of 1 – 1.2 eV and photoconductivity of 10-6 (ohm cm)-1 [1]. Solar cell structures, CdS/Sb2Se3/PbS, showing open circuit voltages, Voc, up to 560 mV and short circuit current densities, Jsc, were prepared using such films. Optimization of the solution bath and deposition conditions as well as post deposition annealing in presence of selenium, sulfur, and evaporated Ag, Sn, or In, and/ or with subsequently deposited metal chalcogenides to modify the composition, quality, optical and electrical properties of chemically deposited Sb2Se3 thin films for their use in photovoltaic structures will be discussed.[1] Y. Rodríguez-Lazcano, Yolanda Peña, M. T. S. Nair, and P. K. Nair, Thin Solid Films, 493 (2005) 77-82.
9:00 PM - F9.9
Synthesis and Thin Film Deposition of Colloidal Cu(In,Ga)Se2 (CIGS) Nanocrystals and their Implementation into Photovoltaic Devices.
Vahid Akhavan 1 , Matthew Panthani 1 , Brian Goodfellow 1 , Brian Korgel 1
1 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States
Show AbstractCIGS nanocrystal dispersions might be utilized as “inks” for low-cost roll-to-roll manufacturing of solar cell modules. We report a robust synthesis of colloidal CIGS nanocrystals with controllable In/Ga stoichiometry that are approximately 10 nm in diameter or less, along with their behavior when incorporated as thin films in prototype photovoltaic devices. The nanocrystals are made by high temperature arrested precipitation, and the ligand chemistry turns out to be extremely important as many commonly used ligands, like phosphines and carboxylic acids, do not work because they yield molecular byproducts or undesired crystal compositions and phases. Room temperature deposition strategies were developed to achieve uniform, thick (~1 micrometer) CIGS nanocrystal films largely free of cracks. These thin films were tested as light-absorbing layers in conventional Mo/CIGS/CdS/i-ZnO/ITO solar cell configurations. The as-deposited films are relatively resistive and prototype devices have showed relatively weak photovoltaic response, with overall efficiencies of ~0.1%. Post-deposition treatments of the nanocrystals increase the conductivity of the absorber layer, with significant impact on the photovoltaic response. The results of these tests will be presented.