Suneel Kodambaka University of California-Los Angeles
Guus Rijnders University of Twente
Amanda Petford-Long Argonne National Laboratory
Andrew Minor Lawrence Berkeley National Laboratory
Stig Helveg Haldor Topsoe A/S
Alexander Ziegler Max-Planck Institute for Biochemistry
NN1/EE1: Joint Session: In-situ Nanomechanics
Monday PM, December 01, 2008
Room 200 (Hynes)
9:00 AM - NN1.1/EE1.1
SEM In situ Compression of Silicon Nanowires.
William Mook 1 , Rudy Ghisleni 1 , Karolina Rzepiejewska-Malyska 1 , Samuel Hoffmann 1 , Laetitia Philippe 1 , Johann Michler 1 Show Abstract
1 , Swiss Federal Laboratories for Materials Testing and Research (EMPA), Thun Switzerland
Silicon nanowires have created a great deal of interest for over a decade due to their enhanced electrical properties when compared to bulk values. These structures also show size-dependent mechanical properties and since they can determine the reliability of many nanodevices and nanosystems, it necessary to quantify their elastic and plastic mechanical response to externally applied loads. This, however, is experimentally challenging due to the length scales involved. Therefore uniaxial compression experiments have been performed in situ with a high resolution scanning electron microscope (SEM) on single crystal silicon nanowires with diameters ranging from 100 nm to 1 μm. A flat-punch indenter can be positioned above the structure of interest with nanometer precision without modifying it due to deformation from mechanical scanning. Compressions are then run under displacement-control at 1 nm/s. By observing the deformation and contact area throughout the experiment engineering stress-strain curves can be extracted from the load-displacement data. Nanowire compressive strength is compared to silicon micropillar compression experiments and to silicon wires in bending.
9:15 AM - NN1.2/EE1.2
SEM In situ Micropillar Compression - Room Temperature Ductile to Brittle Transition of Si, GaAs, InP Semiconductors.
Johann Michler 1 , Fredrik Oestlund 1 , Karolina Rzepiejewska-Malyska 1 , William Mook 1 , Klaus Leifer 2 , Rudy Ghisleni 1 Show Abstract
1 , Swiss Federal Laboratories for Materials Testing and Research (EMPA), Thun Switzerland, 2 Electron Microscopy and Nanoengineering, Department of Engineering Science, Uppsala University, Uppsala Sweden
Current fabrication technology is capable of producing micro- to nano-meter scale structures. The mechanical response of such structures has been shown to depend upon length scales such as pillar diameter. These findings contradict the classical laws of mechanics which assume that mechanical properties are independent of sample size. This contradiction has fostered an increasing number of investigations into mechanical size effects in order to accurately design and fabricate devices at these scales. In an effort to characterize and understand the mechanical behaviour dependence on the size, an investigation on single crystal semiconductor micropillars is presented. Single crystal silicon, gallium arsenide, and indium phosphide micropillars were fabricated by a focused ion beam (FIB) technique. The diameter of the pillars ranged from 200 nm to 10 μm with a length to diameter aspect ratio of three. The micropillars’ mechanical response was investigated by uniaxial compression tests performed with a diamond flat punch using an in situ SEM nanoindenter instrument.Engineering stress-strain curves as a function of pillar diameter are presented. The results show that all the investigated semiconductor materials exhibited a brittle to ductile transition with a decrease in pillar diameter. The deformation mechanism that is responsible for the plasticity is shown to be the formation of Shockley partial dislocations. The decrease of the projected pillar diameter on the crystal slip plane below the equilibrium distance (proportional to the stacking fault energy) between the leading and trailing partial dislocation controls the transition from a brittle to ductile behavior.
9:30 AM - NN1.3/EE1.3
In-situ Investigation of Nano-scale Plasticity in Cubic and Tetragonal Crystals via Homogeneous Deformation of Nano-Pillars.
Julia Greer 1 , Ju-Young Kim 1 , Steffen Brinckmann 1 Show Abstract
1 Materials Science, California Institute of Technology, Pasadena, California, United States
Strength of crystalline materials at reduced dimensions is important for fabrication and reliability of devices at nanometer scales such as MEMS and NEMS, bio-cell sensors, and fuel cells. Plastic flow stress of crystals, a size-independent property for bulk, is found to strongly depend on sample size as it is reduced to nano-scale. To investigate plasticity under homogeneous deformation, we have developed an in-situ micro-deformation methodology, where nano-pillars are mechanically deformed in a one-of-a-kind instrument, SEMentor, which merges the strengths of SEM and Nanoindenter, and offers the advantage of measuring mechanical response of nano-scale materials while capturing video frames throughout the deformation process. We present for the first time results of compression and tension tests performed in-situ inside SEMentor, where load-displacement data is correlated with real-time slip step formation on the surface of the deforming specimens. We perform a new robust technique for stress-strain calculation based on load-displacement data. We also report mechanical strengths of uniaxially-deformed single crystalline nano-pillars with different crystallographic structures (Au, Al, In, Mo) and compare them with one another. Our experiments demonstrate pronounced differences in the behavior of individual structures, and possibly plasticity mechanisms are discussed. We find that although all crystals show an increase in flow stress with decreasing diameter in a power-law fashion, the slopes of these size effects vary with the material, and the ratio between the observed maximum flow stress and the theoretical strength vary significantly.
9:45 AM - NN1.4/EE1.4
Quantitative In Situ Tensile Testing of 1D Nanostructures.
Daniel Gianola 1 , Reiner Moenig 1 , Oliver Kraft 1 2 , Cynthia Volkert 3 Show Abstract
1 Institute for Materials Research II, Forschungszentrum Karlsruhe, Karlsruhe Germany, 2 , University of Karlsruhe, Karlsruhe Germany, 3 Institut für Materialphysik, Universität Göttingen, Göttingen Germany
Plasticity in extremely small volumes is fundamentally different than in large materials; the law of averages gives way to discrete processes that dominate the response. Probing the mechanical response and uncovering the underlying deformation mechanisms of diminishingly small structures at the micro- and nanoscale requires new strategies and approaches that circumvent difficulties associated with handling, gripping, loading, and measuring small specimens. The need for in situ experiments that give a one-to-one correlation between mechanical response and deformation morphology is exacerbated by the fact that electron optics are needed to image and manipulate nanostructures. Tensile experiments are the preferred modality at larger scales since they apply a homogeneous stress state and are less sensitive to boundary conditions, easing interpretation. Meanwhile, results obtained using the popularly employed techniques at the nanoscale (e.g. nanoindentation, micro-compression testing) are clouded by these unresolved issues. Here we describe quantitative in situ tensile experiments on 1D nanostructures in a dual-beam scanning electron microscope (SEM) and focused ion beam (FIB). Specimen manipulation, transfer, and alignment are performed using an in situ manipulator, independently-controlled positioners, and the FIB. Gripping of specimens is achieved using electron-beam assisted Pt deposition. Local strain measurements are obtained using digital image correlation of SEM images taken during testing. Examples showing results for single-crystalline metallic nanowires and nanowhiskers, having diameters between 30 and 300 nm, will be presented in the context of size effects on mechanical behavior, the theoretical strength of crystals, and the influence of defects on the accommodation of plasticity in small volumes.
10:00 AM - **NN1.5/EE1.5
Observation of Size-Dependent Plasticity by In Situ SEM and TEM.
Gerhard Dehm 1 2 Show Abstract
1 Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben Austria, 2 Materials Physics, University of Leoben, Leoben Austria
The continuing trend of miniaturizing materials in many modern technological applications has led to a strong demand for understanding the complex mechanical properties of materials at small length scales. This talk focuses on the recent understanding of the size-dependent plasticity in face-centered cubic metals with dimensions of several microns down to some tens of nanometers. At that length scale sophisticated measurement approaches are required with the advantage of in situ microscopy techniques providing both, control of the deformation experiment and insight in the underlying deformation mechanisms. Size effects of the flow stresses are compared for “wires” and thin films on compliant or stiff substrates. The interpretation of the results is based on recent insights on dislocation nucleation, glide band formation, and dislocation mobility stemming from in-situ SEM and TEM studies of single-crystalline and polycrystalline samples. The results are discussed with the attempt to explain the size effects in straining experiments at small length scales.Acknowledgement: Significant contributions from D. Kiener, R. Pippan, S.H. Oh (Leoben), M. Legros (Toulouse), and P. Gruber (Stuttgart) are acknowledged.
11:00 AM - NN1.6/EE1.6
In Situ Examination of Nanoscale Deformation of Thin Film Bridges within a Scanning Electron Microscope.
Erik Herbert 1 , Arnold Lumsdaine 1 , R. Brian Peters 1 , Warren Oliver 1 Show Abstract
1 , Agilent Technologies, Oak Ridge, Tennessee, United States
Using a high precision nanoindentation head, a new technique has recently been developed to determine the elastic modulus and residual stress of a free-standing doubly-clamped thin film bridge . A desire to examine the impact of certain anomalies in the experimental results (possibly occurring due to misalignment of the tip of the nanoindentation head with the surface of the bridge or due to adhesion of the tip with the surface of the bridge) motivates an examination of the experiment within a scanning electron microscope (SEM). A linear feedthrough mechanism has been developed to position the indentation head within the SEM chamber for precise targeting of the thin film bridge sample (placed on the SEM sample stage). This configuration also allows for the examination of the multi-dimensional deformation state of the bridge when the indentation head contact occurs offset from the center of the bridge.E.G. Herbert, W.C. Oliver, M. P. de Boer, and G.M. Pharr, “Measuring the Elastic Modulus and Residual Stress of Free-Standing Thin Film Bridges by Nanoindentation,” 2007 MRS Spring Meeting, 2007.
11:15 AM - **NN1.7/EE1.7
A New Perspective on Nano-Mechanics: Quantitative Deformation Test in the TEM
Zhiwei Shan 1 , A. Minor 2 3 , J. Nowak 1 , S. Syed Asif 1 , O. Warren 1 Show Abstract
1 , Hysitron Inc., Eden Prairie, Minnesota, United States, 2 , Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 , University of California , Berkeley, California, United States
It is often a challenge to measure accurately the mechanical properties of nanostructures and nanomaterials on account of their extremely small physical dimensions. Recently, we have developed an in situ TEM nanomechanical testing apparatus. This device enables one to acquire quantitative mechanical data while simultaneously recording the microstructural evolution of the materials during deformation, developing a one-to-one relationship between an imposed stress and an individual deformation event. In this talk, we report on the current progress in the application of this in situ TEM device for measuring the mechanical behavior of individual single crystal nickel and metallic glass (MG) pillars. Prior to the deformation tests, the Focused Ion Beam (FIB) fabricated nickel pillars were observed to contain a high density of defects. However, quite unexpectedly, the defects density was observed to decrease dramatically during the deformation process and, in some cases, even resulted in a dislocation-free crystal. The phenomena which we termed as “mechanical annealing” is the first direct observation of the dislocation starvation mechanism and sheds new light on the unusual mechanical properties associated with submicron- and nano- scale structures (Shan et al, Nature Materials, 2008). The compression tests on Cu-Zr-Al MG pillars revealed the intrinsic ability of fully glassy MGs to sustain large plastic strains, which would otherwise be preempted by catastrophic instability in macroscopic samples and conventional tests (Shan et al, PRB, 2008).
11:45 AM - NN1.8/EE1.8
In- Situ Observation of Deformation Characteristics in Nanotwinned Copper Pillars.
Vinay Sriram 1 , Jia Ye 2 3 , Andrew Minor 2 3 , Jenn-Ming Yang 1 Show Abstract
1 Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, California, United States, 2 National Centre for Electron Microscopy, Lawrence Berkeley National Lab, Berkeley, California, United States, 3 Department of Materials Science and Engineering, University of California Berkeley, Berkeley, California, United States
The semiconductor industry is currently moving towards integration of “air gap” technology beyond the 32nm node. A major concern in the introduction of air gap technology is the mechanical integrity, reliability and stability of the vias and interconnects line structures. A new method based on In-situ Transmission Electron Microscopy nanocompression testing of copper pillars which are of the same size scale of vias, interconnects will be presented. Copper pillars having nanotwined boundaries and nanocrystalline grains were tested by this technique. We show direct evidence that twin boundaries can withstand extensive plastic deformation and still retain their structure when compared to regular grain boundaries. The deformation mechanisms of twin boundaries predicted by Molecular Dynamic (MD) simulations has been verified by real-time TEM analysis. Quantitative in-situ stress measurements for deformation twinning are in close agreement with those reported by first principle based calculations.
12:00 PM - NN1.9/EE1.9
In Situ TEM Nanocompression Testing of Gum Metal.
Elizabeth Withey 1 , Andrew Minor 2 , Jia Ye 2 , Shigeru Kuramoto 3 , Daryl Chrzan 1 , John Morris 1 Show Abstract
1 Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States, 2 , National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 , Toyota Central R&D Laboratories, Inc., Nagakute Japan
“Gum Metal” is a newly developed β-Ti alloy that, in the cold-worked condition, has exceptional elastic elongation and high strength. The available evidence suggests that Gum Metal does not yield until the applied stress approaches the ideal strength, and then deforms by mechanisms that do not involve conventional dislocation plasticity. To study its behavior, submicron-sized pillars of solution-treated and cold-worked Gum Metal were compressed in situ in a quantitative compression stage in a transmission electron microscope. Quantitative load vs. displacement data was correlated to real-time images to determine a pattern of deformation that agrees with previous results from ex situ nanoindentation.
12:15 PM - NN1.10/EE1.10
Thermal Behavior of Gold Nanoparticles on Pyrite and Arsenopyrite Surfaces.
Niravun Pavenayotin 1 , Qiangmin Wei 2 , Yanbin Chen 1 , Lumin Wang 1 2 Show Abstract
1 Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan, United States, 2 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Diffusion of gold nanoparticle on pyrite (FeS2) and arsenopyrite (FeAsS) surfaces was studied under in-situ TEM. The gold nanoparticles were deposited onto the surfaces by sputtering of gold TEM grids by ion milling. The gold nanoparticles have a uniform size of approximately 2 nm in diameter. The samples were heated up using a hot stage in the TEM to 100, 200, 300, 400, 500 and 550°C. The movement and characteristics of the nanoparticles were monitored by in situ TEM. The gold nanoparticles coalesce and grow by Oswald’s ripening as the temperature rises. At 500°C, pyrite starts to decompose into amorphous Fe and S. Gold particles on the decomposed surface are driven together and form particles as large as 30 nm in diameter while at the same temperature the gold particles in arsenopyrite are less than 20nm in diameter. Some of the solid gold nanoparticles on pyrite surface also melt and form a film-like morphology. Arsenopyrite does not decompose until 550°C. The gold particles that reside on top of the amorphous decomposed region are immobile. The particles on the crystalline surface grow at a fast rate and visibly mobile on the surface. The differences in the diffusion behavior of gold nanoparticles on two different pyrites will be explained.
12:30 PM - **NN1.11/EE1.11
Revealing the Deformation Processes Responsible for Controlling Mechanical Properties.
Ian Robertson 1 Show Abstract
1 Materials Science and Engineering, University of Illinois, Urbana, Illinois, United States
Transmission electron microscopes have played a critical role in building our knowledge base regarding dislocations, dislocation-obstacle interactions and microstructural evolution as a function of deformation history. Past usage yielded primarily snapshots of the microstructure, leaving the pathways by which it was attained to be deduced. Development of straining stages for use in electron microscopes, cameras for capturing the reaction dynamics and computer technology and software for image processing have enabled observation of dislocation processes in real time and at the spatial resolution of the instrument. Provided the impact of the thin film geometry and the stress state are appreciated, this technique can and has been used to provide visual and quantitative information about dislocation reactions and processes. The results of these studies are now being incorporated into physically-based models for predicting the mechanical properties. Recent developments in stage design provide the capability to measure the macroscopic response and to simultaneously observe the deformation behavior, thus, providing the opportunity to correlate microscopic processes with a macroscopic property. In this talk, examples of applications of standard and new straining stages will be used to illustrate how these tools have advanced our understanding of dislocation reactions and processes and how this insight has been used to yield new models.
NN2: In-situ Growth and Characterization of Nanotubes
Monday PM, December 01, 2008
Room 102 (Hynes)
2:30 PM - **NN2.1
In-Situ Electrical, Mechanical, and Thermal Properties of Carbon Nanotubes and Nanowires by using a TEM-SPM Platform.
Jianyu Huang 1 Show Abstract
1 Center for Integrated Nanotechnologies (CINT), Sandia National Laboratories, Albuquerque, New Mexico, United States
In this talk, I will review our recent progress in using a transmission electron microscopy – scanning probe microscopy (TEM-SPM) platform to probe in-situ the electrical, mechanical and thermal properties of carbon nanotubes  and nanowires. First, buckyballs are formed inside the hollow of multiwall carbon nanotubes, and the buckyballs shrink continuously until they disintegrate, proving the “shrink-wrap” buckyball formation mechanism. Second, using carbon nanotubes as heaters and carbon onions as high-pressure cells, a temperature higher than 2000 °C and a pressure higher than 40 GPa are created in the core of the carbon onions. At such a high pressure and a high temperature, the diamond formed in the carbon onion core exhibits a quasimelting state. Third, plastic deformation, such as superplasticity, kink motion, dislocation climb, and vacancy migration, is discovered in nanotubes. Fourth, nanowires are elongated to a record length without any dislocation activity. Finally, in-situ thermal measurement will be highlighted. J.Y. Huang et al., Nature 439, 281 (2006); J.Y. Huang et al., Phys. Rev. Lett. 94, 236802 (2005); 97, 075501 (2006); 98, 185501 (2007); 99, 175593 (2007); 100, 035503 (2008).
3:00 PM - **NN2.2
Frontiers of In-situ TEM: Thermal Imaging of Nanotubes and Lorentz Imaging of Nanomagnetic Lattices.
John Cumings 1 , Todd Brintlinger 1 , Yi Qi 1 , Kamal Baloch 1 2 Show Abstract
1 Department of Materials Science and Engineering, University of Maryland, College Park, Maryland, United States, 2 Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, United States
In-situ transmission electron microscopy is a rapidly-growing field with many frontiers of research. Most commonly, in-situ techniques are used to study the processing or growth of novel materials. In a different and expanding area of research, in-situ techniques are used instead for uncovering the properties of operational devices and dynamic systems. One example of this is carbon nanotubes under thermal transport conditions. To study this, we have developed a novel thermal imaging technique, electron thermal microscopy , and I will present results applying this technique to the thermal transport of carbon nanotubes. Another growing area of research is the study of interactions of magnetic elements structured at the nanoscale. In one groundbreaking avenue , interacting magnetic elements are patterned on periodic lattices that prevent long-range order. Such systems are frustrated and have the potential for revealing fundamental microscopic properties in materials as diverse as rare-earth oxides and ice. Furthermore, they are highly relevant to technologies which desire to pack magnetic information into increasingly smaller areas, such as MRAM and magnetic hard disk drives. I will present results on in-situ TEM studies of these novel artificially frustrated magnetic systems, and will discuss some of the implications for emerging technologies. This work was supported in part by the NSF-MRSEC at the University of Maryland and utilized its shared equipment facilities, under contract DMR 0520471 T. Brintlinger et al., Nano Letters, 8, 582 (2008).  R. F. Wang et al., Nature, 439, 303 (2006).
3:30 PM - NN2.3
Local Electrical Transport Measurements at LaAlO3/SrTiO3 Interfaces Using STM in TEM.
Johan Borjesson 1 , Alexey Kalabukhov 2 , Robert Gunnarsson 2 , Tord Claeson 2 , Dag Winkler 2 , Krister Svensson 3 , Eva Olsson 1 Show Abstract
1 Microscopy&Microanalysis, Chalmers University of Technology, Gothenburg Sweden, 2 Microtechnology and Nanosience, Chalmers University of Technology, Gothenburg Sweden, 3 Physics and Electrical Engineering, Karlstad University, Karlstad Sweden
LaAlO3 (LAO) and SrTiO3 (STO) are insulators but when an epitaxial LAO thin film is deposited on a STO substrate the interface can show electrical conduction. The conductivity is believed to be due to an induced two-dimensional electron gas at the interface and/or oxygen vacancy doping of the STO in the vicinity of the film/substrate interface. The properties of the interface depend on the oxygen pressure during the LAO thin film growth and on the film thickness. In this work the atomic structure of different interfaces has been determined by high resolution analytical transmission electron microscopy (TEM) using a Titan 80-300 with a probe Cs corrector and a monochromator. The local electrical transport properties have been studied using an in-situ scanning tunneling (STM)-TEM holder. This holder allows simultaneous contacting/electrical characterization and imaging by TEM and scanning TEM (STEM). A direct correlation between atomic structure and electrical transport properties is thereby obtained. Information about oxygen vacancies at and in the vicinity of the film/substrate interface is obtained by electron energy loss spectroscopy.
3:45 PM - NN2.4
In-situ and Ex-situ TEM Microscopy and Spectroscopy Studies of Interfaces in Li-ion Battery Materials.
Chongmin Wang 1 , Gary Yang 2 , S. Thevuthasan 1 , J. Liu 3 , D. Baer 1 , L. Saraf 1 , Wu Xu 2 , J. Zhang 2 , D. Wang 3 , N. Salmon 4 Show Abstract
1 Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, United States, 2 Energy and Environmental Directorate, Pacific Northwest National Laboratory, Richland, Washington, United States, 3 Fundamental and Computational Science Directorate, Pacific Northwest National Laboratory, Richland, Washington, United States, 4 , Hummingbird Scientific, Lacey, Washington, United States
Electrochemical energy storage devices (EES), such as Li-ion batteries, are complex multi-component systems that incorporate widely dissimilar materials and materials phases in physical and electrical contact. The operation of an EES relies critically on electronic and ionic transference across solid–solid and solid–liquid interfaces and within each of the constituent phases. These interfaces may include a reaction front moving through a particle in a two phase reaction; or an interface between the conducting electrode and the electrolyte. The largest and most critical challenge facing an EES is the basic understanding of the structural evolution within the constituent materials and that across the interface/interphase during the cyclic operation of a cell and the consequence of such structural evolution on the properties and lifetime of the cell. In general, mechanisms associated with the intercalation and deintercalation of Li ions in a Li-ion battery system is not fully understood. The structure of the interface between Li intercalated region and the Li free one and the propagation of this interface during charge and discharge of the battery are not well known. Overall, this imposes a fundamental scientific question as how the microstructures within the constituent materials and across the interface/interphase confined by the constituents evolve and impact the properties of the lithium ion battery. Ex-situ methods based on electron beam imaging and spectroscopy has been widely used for probing the structural features of an EES system. However, due to the dynamic structural nature of the process and the sensitivity of some of the materials to air, the ex-situ method cannot answer some of the questions that are related to the dynamical operation of the EES. In-situ capabilities that enable the observation of the structural and chemical changes during the dynamic operation of a battery are most appropriate for addressing this scientific and technological challenge. We have been developing a Transmission electron microscopy (TEM) holder that allows direct observation of the chemical and structural evolution at the interface between the electrolyte and the electrode as well as within the electrodes under the dynamic operation conditions of the Li ion battery system. We have investigated the structural evolution at the interface between TiO2 nanowire anode and the Li based electrolyte using TEM imaging, electron diffraction, and electron energy-loss spectroscopy (EELS) under the operating conditions a battery.
4:30 PM - **NN2.5
Investigating Catalyst Behavior Prior to and During the Growth of Carbon Nanotubes with Real Time TEM.
Eric Stach 1 , Sueng Min Kim 1 , Dmitri Zakharov 2 , Placidus Amama 4 , Cary Pint 3 , Robert Hauge 3 , Benji Maruyama 5 Show Abstract
1 School of Materials Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana, United States, 2 Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana, United States, 4 , Universal Technology Corporation, Dayton, Ohio, United States, 3 Department of Chemistry, Rice University, Houston, Texas, United States, 5 Materials and Manufacturing Direcorate, Wright Patterson Air Force Research Laboratory, Dayton, Ohio, United States
5:00 PM - NN2.6
In-situ Electrical Probing of Silicon During Nanoindentation.
Simon Ruffell 1 , Jim Williams 1 , Jodie Bradby 1 , Naoki Fujisawa 1 , Ryan Major 2 , Oden Warren 2 Show Abstract
1 Electronic Materials Engineering, Australian National University, Canberra, Australian Capital Territory, Australia, 2 , Hysitron Inc., Minneapolis, Minnesota, United States
The Hysitron nanoECR system allows in-situ electrical measurements to be performed during nanoindentation testing. With examples from our work on nanoindentation-induced phase transformations in silicon, we illustrate that the electrical measurements are extremely powerful in aiding understanding of the phase transformation behaviour. They have high sensitivity and can be directly correlated with the mechanical load/unload data.We have shown that under both constant voltage and I-V sweep modes we can track the formation of high pressure crystalline phases (Si-III and Si-XII) during unloading. Careful analysis of through-tip current during constant voltage experiments reveals that the nucleation of these crystalline phases, from the Si-II phase formed during loading, can also be monitored. In addition, the system can be operated as a point probe which has high sensitivity to the local microstructure of phase transformed zones. In particular the I-V characteristics of the tip/sample contact are extremely sensitive to the local material allowing spatial mapping of conductivity within a residual indent. This high sensitivity has allowed detection of seed volumes of these crystalline phases in amorphous Si, that are below detection limits of ex-situ techniques such as Raman micro-spectroscopy. Subtle changes in the final microstructure, which can be modified by changing the starting matrix (i.e. amorphous or crystalline silicon) can also be detected by through-tip conductivity measurements. Finally, we discuss some technical issues related to the capability of making quantitative measurements and show ex-situ electrical measurements which allow correlation of in-situ electrical measurements with electrical properties of the nanoindentation-induced silicon.
5:15 PM - NN2.7
Atomic Scale In-situ Environmental TEM of the Nanoparticle Catalysts for the Nucleation and Growth of Carbon Nanotubes in CVD Condition.
Hideto Yoshida 1 , Tetsuya Uchiyama 1 , Yuusuke Tanemoto 1 , Kazuto Ofuji 1 , Seiji Takeda 1 , Yoshikazu Homma 2 Show Abstract
1 , Osaka Univ., Osaka Japan, 2 , Tokyo University of Science, Tokyo Japan
5:30 PM - NN2.8
In-situ XPS Study of Supported Transition Metal Catalysts during Carbon Nanotube Growth.
Stephan Hofmann 1 , Raoul Blume 2 , Tobias Wirth 1 , Cecilia Mattevi 3 , Cinzia Cepek 3 , Andrea Goldoni 4 , Axel Knop-Gericke 2 , Robert Schloegl 2 , John Robertson 1 Show Abstract
1 Dep. of Engineering, Cambridge University, Cambridge United Kingdom, 2 , Frtiz-Haber Institute, Berlin Germany, 3 , TASC-CNR-INFM, Trieste Italy, 4 , Sincrotrone Trieste SCpA, Trieste Italy
5:45 PM - NN2.9
Hydrothermal Synthesis of Nano-BaTiO3 Particles using Titanate Nanotubes Precursors – A Kinetic Study.
Paula Vilarinho 1 , Florentina Maxim 1 , Paula Ferreira 1 , Ian Reaney 2 Show Abstract
1 Department of Ceramics and Glass Engineering, University of Aveiro, Aveiro Portugal, 2 Department of Engineering Materials, Univeristy of Sheffield, Sheffield United Kingdom
NN3: Poster Session
Tuesday AM, December 02, 2008
Exhibition Hall D (Hynes)
9:00 PM - NN3.1
In Situ Plasticity Measurements in Metallic Nanostructures.
Douglas Stauffer 1 , Ryan Major 2 , William Gerberich 1 Show Abstract
1 Chemical Engineering & Materials Science, University of Minnesota, Minneapolis, Minnesota, United States, 2 , Hysitron, Inc., Minneapolis, Minnesota, United States
A conductive probe is used to probe incipient plasticity in metallic nanostructures by means of in situ conductivity experiments. In situ conductance measurements during nanoindentation have shown that conductance drops are observed at the instant of displacement excursions upon loading. This behavior is described by Matthiessen’s rule as having an inverse relationship between conductivity and dislocation density. Metallic nanostructures are then deformed in order to increase the local dislocation density. Regions of highly deformed material are scanned with the conductive probe to examine the extent of deformation. The local dislocation density can then be calculated from the conductivity measurement.
9:00 PM - NN3.10
Pulsed Electrical Stressing of Amorphous/Nano-Crystalline Silicon Wires.
Adam Cywar 1 , Gokhan Bakan 1 , Cicek Boztug 1 , Mustafa Akbulut 1 , Nathan Henry 1 , Helena Silva 1 , Ali Gokirmak 1 Show Abstract
1 Electrical and Computer Engineering, University of Connecticut, Storrs, Connecticut, United States
9:00 PM - NN3.12
Negative Thermal Expansion and Other Anomalies in Supported Metal Nanoparticles.
Sergio Sanchez 4 , Laurent Menard 5 , Ariella Bram 1 , Joshua Kas 3 , Qi Wang 1 , Joo Kang 2 , Fernando Vila 3 , John Rehr 3 , Ralph Nuzzo 4 , Anatoly Frenkel 1 Show Abstract
4 Chemistry , University of Illinois, Urbana-Champaign, Illinois, United States, 5 Chemistry, University of North Carolina, Chapel Hill, North Carolina, United States, 1 Physics, Yeshiva University, New York, New York, United States, 3 Physics, University of Washington, Seattle, Washington, United States, 2 , The Dow Chemical Company, Midland, Michigan, United States
Negative thermal expansion (NTE), a peculiar effect reported in 1996 in zirconium tungstate and other framework solids and not expected in fcc metals, was recently observed in alumina-supported Pt nanoparticles. In the smallest particles studied (0.9nm in diameter) the Pt-Pt distance decreased gradually by 0.04 Å over a controlled temperature range spaning ~400 K. These effects were also present in larger particles, albeit less extreme than in the 0.9 nm samples, and were attributed to the charge transfer between the cluster and support. Recently, more experimental information on structure and dynamics of Pt clusters was obtained for different sizes, support materials and gas atmospheres. Experimental results combined with the first principles, real-time calculations uncovered dynamic structure of supported metal clusters that exhibit large dynamic fluctuations. This dynamic behavior, previously unaccounted for by ground state DFT calculations, is characterized by strongly non-vibrational electronic and structural real-time effects in these supported clusters that explain their observed anomalies.
9:00 PM - NN3.4
Evanescent-wave Cavity Ring-down Spectroscopy for in Situ Kinetic Study on the Defect Evolution During the Interaction of Atomic Hydrogen and Amorphous Silicon Thin Films.
Mauritius van de Sanden 1 , Floran Peeters 1 , Jie Zheng 1 , Erwin Kessels 1 Show Abstract
1 Applied Physics, Eindhoven University, Eindhoven Netherlands
9:00 PM - NN3.5
Minute-Long Measurement of Year-Long Creep Properties of Concrete by Nanoindentation.
Matthieu Vandamme 1 2 , Franz-Josef Ulm 2 Show Abstract
1 , Université Paris-Est, Champs-sur-Marne France, 2 Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
With an annual consumption of one cubic meter per person, concrete is the most manufactured material on Earth. But concrete subject to sustained load creeps, at a rate that deteriorates the durability and lifespan of concrete infrastructure. Creep experiments on concrete usually are performed on meter-sized specimens and last up to several years, which is both impractical and expensive.While it is generally agreed that concrete creep originates from the complex viscous behavior of its nanometer-sized building blocks (the calcium-silicate-hydrates C-S-H), the creep properties of C-S-H have never been measured directly since C-S-H cannot be recapitulated ex situ in bulk form. Here we develop a comprehensive nano-investigation approach to the creep properties of the fundamental building block C-S-H. This is achieved by extending the realm of classical indentation analysis of homogeneous solids to highly heterogeneous, linear-viscoelastic, cohesive-frictional materials. A formula is derived that enables the assessment of the contact creep compliance from sharp indentation testing, independent of the instantaneous plasticity exhibited during loading.Nine cement pastes with varying water-to-cement mass ratios (w/c), heat treatments (HT), additions of silica fumes (SF) and additions of calcareous filler (CF) are considered. On each sample, several hundreds of 3-minute-long indentation creep tests were performed. It is found that at the nanoscale all C-S-H phases exhibit a logarithmic creep, whose amplitude is inversely proportional to a contact creep modulus C. The contact creep modulus C governing the C-S-H creep rate (~1/t) scales linearly with the indentation hardness H, independent on mix proportions, processing conditions, or additions. Finally, we show that the logarithmic creep measured by indentation testing in some minutes at the nanoscale is as exact as macroscopic creep tests carried out on meter-sized concrete samples over years. This “length-time equivalence” (large time scales can be accessed by looking at small length scales) may turn out to be invaluable for the implementation of sustainable concrete materials.
9:00 PM - NN3.6
Using Localized Surface Plasmon Resonances to Probe the Nanoscopic Origins of Macroscopic Ordering Transitions in Liquid Crystals.
Gary Koenig 1 , Nicholas Abbott 1 Show Abstract
1 Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States
Surface-induced ordering of micrometer-thick films of liquid crystals (LCs) has been reported to occur on the surfaces of a wide range of organic and inorganic materials. Although such studies reveal the ordering of the LC films to be highly sensitive to details of the structure and chemical functionality of these surfaces, the connection between the ordering of the LCs on the micrometer-scale (as probed, for example, by transmission of polarized light) and the near-surface (<20 nm) ordering of the LCs is complex and not well-understood. Non-linear optical measurements, such as optical second harmonic generation, have yielded important insights, including observations of near-surface order above the bulk nematic-to-isotropic clearing temperatures (TNI). Such measurements, however, are complicated to perform and are not generally possible in the presence of bulk LC due to quadrupolar contributions to the second harmonic signal. In this presentation, we will describe the use of localized surface plasmon resonances (LSPRs) of gold nanodots to characterize the nanoscale ordering of LCs. When combined with in situ polarized light microscopy, we demonstrate that this simple approach permits simultaneous measurement of changes in local (nanoscopic) and far-field (macroscopic) structure during ordering transitions in LCs. Changes in ordering of LCs due to thermal effects as well as specific binding of molecules at surfaces will be described. These results also suggest principles for new classes of plasmonic sensors.
9:00 PM - NN3.7
In-Situ High Resolution TEM Nanoindentation of Silver Nanoparticles.
Christopher Carlton 1 , Oleg Lourie 2 , Paulo Ferreira 1 Show Abstract
1 Mechanical Engineering, University of Texas, Austin, Texas, United States, 2 , Nanofactory Instruments, Gothenburg Sweden
While there are still many questions unanswered in the field of nanomaterials, it is clear that downsizing the characteristic length of materials to the nanoscale has a significant impact on materials behavior and properties. Of particular interest to this work is the effect of the nanoscale on the mechanical behavior of nanoparticles, as well as how the nanoscale environment influences the nucleation and motion of crystalline defects, in particular dislocations. To address this issue, in-situ phase contrast transmission electron microscopy (TEM) nanocompression experiments have been performed on 20nm silver nanoparticles. High-resolution TEM images show the appearance of dislocations within the nanoparticle during deformation. Interestingly, the particle appears to be dislocation free both before and after deformation. An explanation for this behavior is presented, as well as the implications of this experiment to the greater field of nanoindentation in discussed.
9:00 PM - NN3.8
Nanomanipulation and Accurate Electrical Testing of Individual Gold Nanowires Studied by Nanomanipulators In-situ SEM.
Yong Peng 1 2 , Guenter Moebus 1 , Tony Cullis 2 , Beverley Inkson 1 Show Abstract
1 Engineering Materials, University of Sheffield, Sheffield United Kingdom, 2 Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield United Kingdom
Suneel Kodambaka University of California-Los Angeles
Guus Rijnders University of Twente
Amanda Petford-Long Argonne National Laboratory
Andrew Minor Lawrence Berkeley National Laboratory
Stig Helveg Haldor Topsoe A/S
Alexander Ziegler Max-Planck Institute for Biochemistry
NN4: Nucleation, Growth and Coarsening Kinetics of Nanostructures
Tuesday AM, December 02, 2008
Room 102 (Hynes)
9:15 AM - NN4.2
Thermal Stability of TiO2 Nanoparticles with Controlled Size and Shape:in-situ Studies by XRD and TEM.
Celine Perego 1 , Renaud Revel 1 , Olivier Durupthy 2 3 , Sophie Cassaignon 2 3 , Jean-Pierre Jolivet 2 3 Show Abstract
1 , IFP-Lyon, 69360, Solaize France, 2 , UPMC Univ Paris 06, UMR 7574, Laboratoire de Chimie de la Matière Condensée de Paris, 75005, Paris France, 3 , CNRS, UMR 7574, Laboratoire de Chimie de la Matière Condensée de Paris, 75005, Paris France
Transition alumina are largely used as catalyst supports in refining and petrochemicals. However, titanium dioxide TiO2, was shown to display higher catalytic activity as a support of MoS2 in desulphurization process . The low surface area generally obtained for these materials and the relatively poor thermal stability observed restrain their use. Therefore, the synthesis of smaller particles (10-100 nm) and the preservation of their size during thermal treatment should enhance catalytic performances. Indeed, these properties strongly depend on the surface properties of the support, which are closely related to the structure, the size and the shape of particles .We present in-situ studies of thermal stability of TiO2 nanoparticles. Those particles are pure phases of TiO2 (anatase, brookite and rutile) with controlled size and morphology [3-5]. For each pure polymorph, several morphologies in nanometric scale have been considered. The thermal stability of these particles, depending of their structure, size and shape, and specific adsorption of ions was studied. We show by in-situ XRD, that the evolution of nanoparticles size and the temperature of phase transition depend not only on the initial structure6, but also on the morphology and the nature of adsorbed species. Another promising result show the impact of the gas atmosphere during sintering on the particles size. The use of a nitrogen atmosphere during anatase sintering leads to much bigger rutile particles after phase transition. Crystal growth mechanisms were investigated through in-situ TEM, and also TDA/TGA, XRD, and HRTEM. Ramirez, J.; Fuentes, S.; Diaz, G.; Vrinat, M.; Breysse, M.; Lacroix, M. Appl. Catal. 1989, 52 (1), 211-224. Dzwigaj, S.; Arrouvel, C.; Breysse, M.; Geantet, C.; Inoue, S.; Toulhoat, H.; Raybaud, P. J. Catal. 2005, 236 (2), 245-250. Cassaignon, S.; Koelsch, M.; Jolivet, J. P. J. Phys. Chem. Solids 2007, 68 (5-6), 695-700. Durupthy, O.; Bill, J.; Aldinger, F. Crystal Growth & Design 2007, 7 (12), 2696-2704. Pottier, A.; Chaneac, C.; Tronc, E.; Mazerolles, L.; Jolivet, J. P. J. Mater. Chem. 2001, 11 (4), 1116-1121. Zhang, H. Z.; Banfield, J. F. J. Phys. Chem. B 2000, 104 (15), 3481-3487.
9:30 AM - NN4.3
In-situ TEM Sintering of FCC Nanoparticles.
Michael Asoro 1 , Desiderio Kovar 1 , Paulo Ferreira 1 Show Abstract
1 Materials Science and Engineering, University of Texas at Austin, Austin, Texas, United States
Nanoparticles are currently of great scientific interest due to their large number of possible applications - such as catalysts in fuel cells and as delivery vehicles for medicine. However, because nanoparticles have a high surface curvature when compared with larger particles, there is a much larger driving force for diffusion. As a consequence, sintering can take place over shorter time scales, even at room temperature. In this context, the objective of this work is to investigate the mechanisms of sintering in nanoparticles at temperatures slightly above ambient. In-situ transmission electron microscopy (TEM) heating experiments on silver nanoparticles are performed at 100°C so that the sintering process could be observed in real time. We observe a large increase in neck radius and a small reduction in inter-particle distance, suggesting that surface diffusion is the dominant sintering mechanism in FCC metals. The surface diffusion kinetics are calculated from the observed changes in nanoparticles morphology.
9:45 AM - NN4.4
Atomic Scale Real Time Observation of Iridium Cluster Formation on MgO Surface from Mononuclear Ir(C2H4)2 Complexes by Transmission Electron Microscopy.
Volkan Ortalan 1 , Alper Uzun 1 , Bruce C. Gates 1 , Nigel D. Browning 1 2 Show Abstract
1 Chemical Engineering and Materials Science, University of California-Davis, Davis, California, United States, 2 Chemistry, Materials and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
10:00 AM - NN4.5
Reduction of Oxide Islands on Metal Surfaces Investigated by In-situ UHV TEM.
Guangwen Zhou 1 2 , Weiying Dai 3 , Judith Yang 4 Show Abstract
1 Mechanical Engineering, State University of New York at Binghamton, Binghamton, New York, United States, 2 & Multidisciplinary Program in Materials Science and Engineering, State University of New York at Binghamton, Binghamton, New York, United States, 3 MR Physics Center, Department of Radiology, Harvard University , Boston, Massachusetts, United States, 4 Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
The reduction of metal oxides plays critical roles in many fields including materials science, microelectronics, and chemical applications. While the reaction equation is simple, many aspects of the reaction still remain poorly understood. Traditionally, the reduction process has been described using phenomenological kinetic models (e.g., “nucleation and growth model” and “interface model”) where the reduced oxide nucleates and grows on the surface of the parent oxide. Although these models have been found useful in the description of the reduction processes of bulk oxides, here we show using in situ UHV-TEM that they do not apply to the reduction of oxide nanoislands on metal surfaces. Our in situ TEM observations reveal that the reduction of Cu2O islands on Cu(100) follows a linear shrinkage behavior and the reduced phase (e.g., Cu) nucleates and grows on the substrate surface surrounding the reducing Cu2O islands, rather than on the parent oxide; this is fundamentally different from the assumption by the traditional phenomenological models. The reduction of these oxide islands leads to the formation of surface craters. Our Monte Carlo simulations reveal that the growth of the crater rim is controlled by the homoepitaxial growth of Cu adatoms decomposed along the perimeter of reducing Cu2O islands. G.W. Zhou, W. Dai, J.C. Yang, Phys. Rev. B. 77, 245427 (2008)  G.W. Zhou, J.C. Yang, Phys. Rev. Lett. 93, 226101 (2004)
10:15 AM - NN4.6
In Situ Transmission Electron Microscopy Studies of the Kinetics of Carbothermal Synthesis of Titanium Carbide.
Marta Pozuelo 1 , Xiaofeng Zhang 2 , Jeung Park 1 , Rasit Koc 3 , Suneel Kodambaka 1 Show Abstract
1 Materials Science and Engineering, University of California Los Angeles, Los Angeles, California, United States, 2 , Hitachi High Technologies America, Inc., Pleasanton, California, United States, 3 Mechanical Engineering, Southern Illinois University , Carbondale, Illinois, United States
Titanium carbide (TiC) has a wide variety of applications in the areas of catalysis, structural reinforcements, and hard wear- and oxidation-resistant coatings due to its extremely good properties such as high melting temperature, high hardness, excellent oxidation resistance, low thermal expansion coefficient, high wear resistance and light weight. One of the most commonly used methods for TiC production is carbothermal reduction of TiO2 at elevated temperatures (>1200 °C). This reduction reaction is suggested to occur via successive formation of lower oxides of titanium along with the emission of CO and CO2 gases. However, the exact details of the reaction kinetics, which control the final particle size, shape, and crystal structure are largely unknown. In situ lattice-resolution transmission electron microscopy (TEM) allows direct observation of the changes in particle shapes and sizes, their crystallinity, and chemical composition. Here, we present in situ TEM studies of the chemical reaction pathways and mass transport mechanisms underlying the carbothermal reduction synthesis of TiC. First, C-coated titania particles are prepared by pyrolysis of propylene (C3H6) gas in an oxygen-free environment at ~ 600 °C in a tube furnace filled with titania powders (average size ~ 20 nm). This process resulted in a uniform coating of pyrolytic carbon shell (thickness ~2-5 nm) around individual oxide particles. In situ TEM experiments are carried out at the Hitachi EM Lab in Pleasanton, California using an atomic resolution Hitachi H-9500 300 kV TEM (base pressure ~ 10-6 Torr) which allows in-situ heating in vacuum or in a gas environment. The oxide-core/C-shell nanoparticles are deposited directly onto a heating filament of the gas injection-heating TEM sample holder. Lattice-resolution TEM images are acquired at video rate (15 frames/s) while heating the particles in vacuum up to 1000 °C for times up to 5 h. Energy dispersive X-ray spectra (EDX) are obtained at room temperature from the samples before and after the annealing experiments. We find several interesting phenomena: 1) crystallization of carbon to form graphene layers preferentially on the lowest-energy planes of TiO2; 2) shrinking and eventual disappearance of the oxide cores while being encapsulated by carbon, resulting in the formation of hollow-core graphene shell structures; 3) reduction of TiO2 to lower oxides. These studies provide kinetic information and atomic-scale insights into the early stage carbothermal reduction process leading to the synthesis of TiC particles.
10:45 AM - **NN4.7
Gas-Induced Transformations in the Synthesis and Evolution of Catalytic Nanomaterials.
Peter Crozier 1 Show Abstract
1 School of Materials, Arizona State University, Tempe, Arizona, United States
Catalytically active nanomaterials play a critically important role in modern technology significantly impacting areas such as energy production as well as pharmaceuticals, chemicals, and materials synthesis. Heterogeneous catalysis relies on the unique ability of highly dispersed forms of material to direct chemical transformations. However, the “active form” of the material may exist only inside a reactor where gas induced changes in the nanostructure of the catalyst such as phase transformation, shape changes and surface reconstructions may take place. Nanoscale characterizing of the composition, bonding and structure of the active form of the material is necessary to develop a deep understanding of the structure-property relations for heterogeneous catalysts. We are using in situ environmental transmission electron microscopy (ETEM) to study fundamental questions associated with the synthesis and evolution of catalytic nanomaterials under reactive gas conditions. The ability to perform atomic resolution imaging and nanospectroscopy in a reactive gas environment allows us to explore dynamic variations in the nanostructure and chemistry high surface area catalytic materials. This presentation will focus on the application of ETEM to supported metal and oxide catalysts. The nucleation and growth processes taking place during the synthesis of bimetallic nanoparticles on high surface-area oxide supports will be discussed (RuCo/Al2O3, NiCu/TiO2) [1-3]. Recent work on cerium-based oxide (CeO2 and ZrxCe1-xO2) demonstrates that the activity of individual nanoparticles can be measured and compared [4-6]. References P. Li et al, J. Chem. Phys. B, 109, (2005), 13883. P. Li et al, Surf. Sci., 600 (2006), 693. P. Li, et al, Appl. Catal. A, 307(2006) 212. R. Sharma et al, Phil. Mag. 84, (2004), 2731. R. Wang et al, J. Phys. Chem B, 110 (2006) 18278. R. Wang et al, Nanoletters, 8(3), (2008) 962.
11:15 AM - NN4.8
Environmental Electron Microscopy of the Nucleation and Growth of Si and Ge Nanowires.
Stephan Hofmann 1 , Renu Sharma 2 , Tobias Wirth 1 , Caterina Ducati 3 , Takeshi Kasama 3 , Rafal Dunin-Borkowski 4 , Peter Bennett 5 , Jeff Drucker 5 , John Robertson 1 Show Abstract
1 Dep. of Engineering, University of Cambridge, Cambridge United Kingdom, 2 LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, Arizona, United States, 3 Dep. of Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom, 4 Center for Electron Nanoscopy, TU Denmark, Lyngby Denmark, 5 Department of Physics, Arizona State University, Tempe, Arizona, United States
Silicon and germanium nanowires could be important constituents of future nano-electronic devices. These applications require greater control of the growth process and if possible the use of catalysts other than gold. We present a video-rate environmental transmission electron microscopy study of Si nanowire nucleation from Pd  and Ni under disilane exposure. The Pd and Ni catalyst films form silicide particles, which remain solid during nanowire nucleation and growth. A Si crystal nucleus forms by phase separation, as observed for the liquid Au–Si system, which we use as a comparative benchmark. The dominant coherent Pd silicide/Si growth interface subsequently advances by lateral propagation of ledges, driven by catalytic dissociation of disilane and coupled Pd and Si diffusion. We compare these catalyst interface dynamics to Ge nanowire growth from digermane. S Hofmann et al, Nature Materials 7, 372 (2008)
11:30 AM - **NN4.9
Materials Interactions During the Growth of Heterostructure Nanowires.
Frances Ross 1 Show Abstract
1 TJ Watson Research Center, IBM Research Division, Yorktown Heights, New York, United States
Semiconductor nanowires formed via the vapour-liquid-solid mechanism have a wide variety of technological applications, but many of the most exciting electronic device possibilities require the growth of heterostructures, where for example the wire composition changes along its length. Creating such heterostructures permits an extensive variety of interactions between the different materials in the wire and the catalyst itself. In this talk we focus on the use of in situ microscopy to unravel some of these interactions. We will discuss two cases of particular technological interest: the growth of “hybrid” nanowires, which contain segments of group IV and group III-V materials, and the formation of III-V nanowires on Si substrates. We show that certain materials pairs, such as GaP and Si, can be grown in the same nanowire using the same Au catalyst, and we present real-time observations, made using UHV-TEM, of the changes in composition and structure of catalysts on III-V wires as the second material, Si or Ge, is introduced. In situ observations allow us to characterize surface and interface reactions and measure parameters such as the critical supersaturation for nucleation of the second material. By visualizing the morphology of the second material as it grows, in situ observations also allow us to understand the overall morphology of the resulting wire, in particular whether it is straight or kinked, leading to the exciting possibility of growing interleaved segments of group IV and III-V semiconductors for electronic and optoelectronic applications. For III-V nanowires grown on Si substrates, we show that interactions between components of the wire, such as In, and the Au catalyst, can strongly influence the catalyst stability and hence the overall wire morphology in terms of tapering and growth rate. The mechanism of this effect is a change in the surface diffusion of Au on Si due to alloying, suggesting ways to control nanowire structure. These examples barely scratch the surface of the rich variety of materials interactions in play during nanowire growth, and it is clear that in situ observations are essential to understanding and controlling the formation of complex nanowire structures for applications.
12:00 PM - **NN4.10
Kinetics of Nano Silicide Formation in Nano Si Wires.
King-Ning Tu 1 , Kuo-Chang Lu 1 , Yi-Chia Chou 1 Show Abstract
1 , University of California at Los Angeles, Los Angeles, California, United States
When two nanowires cross each other, they form a point contact. Point contact reaction between a nano metal wire and a nano Si wire has been studied by using ultra-high vacuum and high resolution transmission electron microscopy. Axel epitaxial growth of nano-silicdes of NiSi and CoSi2 in nanowires of Si has been observed. Due to the potential application of axel hetero-structure of silicide/Si/silicide as biosensor, we have been able to control the length of the nanogap of Si between the two silicide electrodes down to 2 nm. The nucleation stage and stepwise growth stage of the reactive epitaxial growth of nano silicide on nano Si have been measured. A repeating event of nucleation has been observed, which may enable us to estimate the number of atoms in a critical nucleus and the Zeldovich factor. A supply-controlled growth mode of point contact reactions in nanowires is assumed, which is different from the well-known diffusion-controlled and interfacial-reaction-controlled mode of growth in thin film and bulk reactions.
12:30 PM - NN4.11
In-situ TEM Observation of Repeating Events of Nucleation in Epitaxial Growth of Nano CoSi2 in Nanowires of Si.
Yi-Chia Chou 1 , King-Ning Tu 1 , Wen-Wei Wu 2 , Lih-Juann Chen 2 Show Abstract
1 Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California, United States, 2 Materials Science and Engineering, National Tsing Hua University, Hsinchu Taiwan
The formation of CoSi and CoSi2 in Si nanowires at 700 °C and 800 °C, respectively, by point contact reactions between Co and Si nanowires have been investigated in situ in a ultrahigh vacuum high-resolution transmission electron microscope. The CoSi2 has undergone an axial epitaxial growth in the Si nanowire and a stepwise growth mode was found. We observed that the stepwise growth occurs repeatedly in the form of an atomic step sweeping across the CoSi2/Si interface. It appears that the growth of a new step or a new silicide layer requires an independent event of nucleation. We are able to resolve the nucleation stage and the growth stage of each layer of the epitaxial growth in video images. In the nucleation stage, the incubation period is measured, which is much longer than the period needed to grow the layer across the silicide/Si interface. So the epitaxial growth consists of a repeating nucleation and a rapid stepwise growth across the epitaxial interface. This is a general behavior of epitaxial growth in nanowires and it is also observed in NiSi formation in a Si nanowire. A discussion of the kinetics of supply-limited and source-limited reaction in nanowire case by point contact reaction is given. The axial heterostructure of CoSi2/Si/CoSi2 with sharp epitaxial interfaces has been obtained, which is promising as high performance transistors based on intrinsic Si nanowires.
12:45 PM - NN4.12
In situ Transmission Electron Microscope Study of the Nucleation and Growth of Platinum Nanocrystals in Solution.
Haimei Zheng 1 2 3 , Rachel Smith 3 , Young-wook Jun 2 3 , Chrisian Kisielowski 1 2 , Paul Alivisatos 2 3 , Ulrich Dahmen 1 2 Show Abstract
1 National Center for Electron Microscopy, Lawrence Berkeley National Lab, Berkeley, California, United States, 2 Chemistry, University of California, Berkeley, California, United States, 3 Materials Sciences Division, Lawrence Berkeley National lab, Berkeley, California, United States
NN5: Ultra-Fast Microscopy and Diffraction
Tuesday PM, December 02, 2008
Room 102 (Hynes)
2:30 PM - **NN5.1
Dynamic Transmission Electron Microscope: Studying Nanoscale Material Processes with Nanosecond Time Resolution and Beyond.
Thomas LaGrange 1 , Geoffery Campbell 1 , Nigel Browning 1 2 , Bryan Reed 1 , Judy Kim 1 , James Evans 1 , Mitra Taheri 1 3 , Wayne King 1 Show Abstract
1 Chemistry Materaials and Life Sciences, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Department of Chemical Engineering and Materials Science, University of California-Davis, Davis, California, United States, 3 Department of Materials Science and Engineering, Drexel University , Philadephia, Pennsylvania, United States
There have been many efforts in the past decades to improve the spatial resolution of transmission electron microscopes but little in way of improving the temporal resolution of in situ transmission electron microscopy. Most materials dynamics occur at rates much faster than can be captured with standard video rate acquisition methods. Thus, there is a need to increase temporal resolution in order to capture and understand salient features of these rapid materials processes. To meet the need for studying fast dynamics in material processes, we have constructed a nanosecond dynamic transmission electron microscope (DTEM) at Lawrence Livermore National Laboratory to improve the temporal resolution of in-situ TEM observations. The DTEM consists of a modified JEOL 2000FX transmission electron microscope that provides access for two pulsed laser beams. One laser drives the photocathode (which replaces the standard thermionic cathode) to produce the brief electron pulse. The other strikes the sample, initiating the process to be studied. A series of pump-probe experiments with varying time delays enable, for example, the reconstruction of the typical sequence of events occurring during the martensitic phase transformation. This presentation will discuss the core aspects of the DTEM instrument and how the DTEM has been used to study rapid solid-state phase transformations and chemical reactions.. Work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory and supported by the Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, of the U.S. Department of Energy under contract No. DE-AC52-07NA27344.
3:00 PM - **NN5.2
Lights, Action, Camera: Making Movies of Molecules (and Materials) with Ultrafast Electron Diffraction.
Bradley Siwick 1 Show Abstract
1 Departments of Physics and Chemistry, McGill University, Montreal, Quebec, Canada
Is it possible to obtain a real-time view of chemical reactions by fully resolving the elementary atomic motions that accompany the breaking and making of chemical bonds in the transition state region between reactant and product states? Or to make direct observations of the collective atomic motions that lead to structural phase transitions in material systems as they take place? The development of time-resolved diffraction techniques – both x-ray and electron – with ultrafast temporal resolution (< 10 ns) has recently made such experiments a reality. My talk will focus on ultrafast electron diffraction. I will describe its goals and methods as well as the technical challenges associated with the development of femtosecond electron sources. Despite these difficulties it is possible to design relatively simple pulsed electron sources that are effectively equivalent in flux to 3rd generation synchrotron sources of x-ray pulses, but 2-3 orders of magnitude better in temporal resolution. Experiments performed using such an electron source to study laser-induced solid-to-liquid phase transitions in metals will be discussed. Detailed pictures of the atomic configuration during the melting transition have been obtained in these studies – a molecular movie of sorts. I will conclude by describing one very promising way to significantly advance the current state-of-the-art that makes use of radio-frequency cavity technology; a common element in particle accelerator beamlines.
3:30 PM - NN5.3
Nanosecond Imaging in the Dynamic TEM Reveals Transient Phase Separation.
Judy Kim 1 2 , Thomas LaGrange 1 , Bryan Reed 1 , Nigel Browning 1 2 , Geoffrey Campbell 1 Show Abstract
1 CMS, LLNL, Livermore, California, United States, 2 Chemical Engineering and Materials Science, University of California, Davis, California, United States
Until recently, materials science characterization techniques have lacked the means for direct observation of sub-micron, dynamic materials processes that occur faster than the millisecond scale. Due to electron current density limitations and slow CCD readout times, Transmission Electron Microscopy (TEM) techniques that reveal nanoscale phase and morphology with real-space imaging and structure from diffraction have been limited to video-rate (~10-3 s) time-resolution.The Dynamic TEM (DTEM) has been developed  to address this gap in characterization capability by using a photoemitted electron pulse to probe dynamic events with “snap-shot” diffraction and imaging at 10 ns resolution. Using this capability, the moving reaction front (~10 m/s) of reactive nanolaminates is directly observed in situ. DTEM images show a transient cellular morphology in a dynamically mixing, self-propagating reaction front, revealing brief phase separation, and thus provide fundamental insights into the mechanisms driving the self-propagating high-temperature synthesis. Reactive Multilayer Foils (RMLF), also called nanostructured metastable intermolecular composites, are layers of polycrystalline reactant materials that go through exothermic, self-propagating reactions when mixing is driven by an external stimulus. Since RMLFs produce immense heat over a small surface area, they are used in application as localized heat sources for material bonding or biological neutralization. In addition, the periodic nano-construction makes RMLFs relevant for examination of in situ progression of interface-controlled diffusion.In this study, the foils undergo an exothermic self-propagating reaction as the bilayers mix to form intermetallics. This reaction front travels at a velocity of ~10 m/s and is observed directly in the DTEM for the complete progression of the material transition. By studying the transient states of these dynamic materials to identify the mechanisms that govern the rate of heat generation and transport, we can understand more about atomic diffusion between thin films and phase boundary motion for optimized engineering applications. A comparative study of varied stoichiometry in NiV/Al foils will be presented. The data reveals the variations in phase formation/separation morphology as well as highlight the relationship between foil stoichiometry and reaction front velocity. This experiment continues with foils of varied geometry and composition .References M. R. Armstrong, et al., Ultramicroscopy 107 356-367 (2007). This work performed under the auspices of the U.S. Department of Energy, Office of Basic Energy Sciences by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
3:45 PM - NN5.4
Femtosecond and Nanosecond Pulsed Laser Ignition Thresholds of Al/Pt Multilayer Foils.
Joel McDonald 1 , Eric Jones 1 , Kathryn Chinn 1 , Yoosuf Picard 3 , Steven Yalisove 2 , David Adams 1 Show Abstract
1 Thin Films, Vacuum, and Packaging, Sandia National Labs, Albuquerque, New Mexico, United States, 3 , Naval Research Lab, Washinton, District of Columbia, United States, 2 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
4:30 PM - NN5.5
In-situ Analysis and Characterization of Morphology Evolution During Reaction of Energetic Co/Al Multilayer Foils.
Joel McDonald 1 , Eric Jones 1 , Kathryn Chinn 1 , Michael Hobbs 1 , David Adams 1 Show Abstract
1 , Sandia National Labs, Albuquerque, New Mexico, United States
4:45 PM - NN5.6
In Situ X-ray Icrodiffraction with Microsecond Temporal Resolution of Phase Transformations in Rapidly Propogating Exothermic Reactions in Nanoscale Multilayers.
Jonathan Trenkle 1 , Lucas Koerner 3 , Mark Tate 3 , Sol Gruner 3 4 , Timothy Weihs 2 , Todd Hufnagel 2 Show Abstract
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Physics, Cornell University, Ithaca, New York, United States, 4 Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York, United States, 2 Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States
Reactive multilayer foils are comprised of alternating nanoscale layers of materials that can sustain a self-propagating exothermic reaction. Depending on the foil architecture, the reaction can reach temperatures in excess of 1500 K in microseconds, making reactive foils attractive for use in several applications including ignition sources and joining heat-sensitive materials. From a scientific perspective, these materials provide an opportunity to study phase transformations in the presence of high heating rates and steep concentration gradients. In situ characterization of processes in the reaction zone however is challenging, requiring both temporal resolution better than ∼100 μs (the time required for the reaction front to pass a fixed location) and spatial resolution of <100 μm (the approximate width of the reaction zone).We have successfully used synchrotron x-ray radiation and a pixel array detector at the Cornell High Energy Synchrotron Source to study phase evolution in situ during self-propagating reactions in Al/Ni and Zr/Ni reactive multilayers. The temporal resolution (∼50 μs) and spatial resolution (∼60 μm) of the measurements was sufficient to allow us to observe the phase transformation sequence in detail, identifying key transformations in the development of the final structure. For example, in Al/Ni foils with overall composition Al3Ni2 and a heating rate ~106 K s-1, all of the Al and Ni is consumed within the first 200 μs of the reaction to form an Al-rich amorphous phase, which we predict is liquid, and cubic AlNi. The only other reaction occurs some 38 ms later during cooling when the equilibrium Al3Ni2 phase forms in a peritectic reaction. Similar results are observed for Al/Ni foils with overall composition AlNi.These results differ significantly from those observed in these foils at slower heating rates (~1 K s-1) where intermediate, metastable crystalline phases (Al9Ni2 and Al3Ni) form prior to final equilibrium phase formation. The in situ results for the Al/Ni systems thus provide a more accurate picture of the phase progression in self-propagating reactions in Al/Ni. In the case of Zr/Ni reactive foils, however, the first phase to form in a self-propagating reaction (with a heating rate of ~105 K s-1) and during annealing at slower heating rates (~1 K s-1) is a solid amorphous phase.
5:00 PM - NN5.7
Solving the Structure of Reaction Intermediates by Time-Resolved X-ray Absorption Spectroscopy.
Qi Wang 1 , Anatoly Frenkel 1 , Jonathan Hanson 2 Show Abstract
1 Department of Physics, Yeshiva University, New York, New York, United States, 2 Chemistry Department, Brookhaven National Laboratory, Upton, New York, United States
A robust data analysis method of time-resolved x-ray absorption spectroscopy (TR-XAS) experiments suitable for chemical speciation and structure determination of reaction intermediates is presented. In this method, principal component analysis (PCA) is performed on the in-situ time-resolved x-ray absorption near-edge structure (TR-XANES) data of the reaction to achieve chemical specification and thus isolate the reaction intermediate. Then theoretical modeling by using FEFF6 is applied to the corresponding extended x-ray absorption fine-structure (EXAFS) data of the selected intermediate to determine its local structure. The method will be illustrated by using the reduction and re-oxidation reactions of Cu-doped Ceria catalysts where we detected reaction intermediates and measured fine details of the reaction kinetics. The approach can be directly adapted to many in-situ, real-time, x-ray spectroscopy experiments where new rapid throughput data collection and analysis methods are needed.AIF and QW acknowledge the U.S. Department of Energy (DOE-BES Catalysis Science) grant No. DE-FG02-03ER15476) for financial support of this work. The research carried out at BNL was financed through contract DE-AC02-98CH10886 with the US Dept. of Energy (Division of Chemical Sciences).
5:15 PM - NN5.8
In Situ Electron Transfer Studies of Rigid, Ruthenium Complexes Inducing Aggregation of Spherical Nanoparticles.
Natalie Herring 1 , Jordan Poler 1 Show Abstract
1 Chemistry, University of North Carolina Charlotte, Charlotte , North Carolina, United States
Understanding nanoparticle aggregation is important for achieving long-range control over aggregating nanoparticles; this may provide the ability to direct self-assembly of nanoparticles for use in devices. In solution, coordination complexes act as coagulating agent and induce nanoparticle aggregation. Current studies focus on inducing flocculation of gold colloids using large, rigid, dendritic ruthenium coordination complexes. Dynamic light scattering (DLS) and absorption spectroscopy are being implemented to gain an understanding of in situ interactions of spherical nanoparticles in the presence of coordination complexes. DLS follows the effective hydrodynamic diameter of aggregating colloids and provides size distribution of aqueous solutions. DLS and absorption spectroscopy monitor in situ aggregation rates as a function of coagulant concentration; these methods describe aggregation kinetics and are used to determine the critical coagulation concentration. Conversely, absorption spectroscopy monitors the change in gold colloids’ optical properties, mainly, the surface plasmon absorption band, which is size dependent. Preliminary results yield novel spectra that are inconsistent with electrolyte induced aggregation, indicating charge transfer. Furthermore, scanning electron microscopy (SEM) and atomic force microscopy (AFM) are being utilized to examine the aggregate structure and morphology. Combining these methods provides information on the evolution of nanometer-sized particles into micrometer-sized aggregates for time scales that vary from microseconds to thousands of seconds. Characterization results demonstrate potential for controlling nanoparticles and will likely provide new opportunities for direct 3D manufacturing of nanoscale devices.
5:30 PM - NN5.9
In situ Time-Resolved X-ray Diffraction and X-ray Absorption Spectroscopy Studies of an Industrial Cu,Cr-Fe2O3 Catalyst for the Water-Gas Shift Reaction.
Daniela Zanchet 1 , Daniela Oliveira 1 , Cristiane Rodella 1 , Marco Logli 3 , Valeria Vicentini 3 , Wen Wen 2 , Jonathan Hanson 2 , José Rodriguez 2 Show Abstract
1 Scientific Department, LNLS -Brazilian Synchrotron Light Laboratory, Campinas, São Paulo, Brazil, 3 , Oxiteno S.A. Ind. & Com., Mauá, São Paulo, Brazil, 2 Chemistry Department, Brookhaven National Laboratory, Upton, New York, United States
The water gas shift (WGS) reaction, where CO and steam are converted to CO2 and H2, is an important step in several industrial processes since it removes the residual CO that acts as poison for fuel cells and maximizes the production of H2. In industrial operations, the WGS is carried out in two stages, known as HTS (High Temperature Shift) reaction (350-450°C) and LTS (Low Temperature Shift) reaction (200-250°C). The most common industrial HTS catalyst is commercialized as hematite (alfa-Fe2O3), promoted with chromium and copper. It is converted in-situ to magnetite (Fe3O4) during the activation process, the active phase in the HTS reaction. A careful control of the reducing conditions and temperature during activation and operation of the catalyst is required, to avoid the formation of metallic iron and maximize its performance. In this work, we address the activation and performance in isothermal operation of an industrial HTS (Cu,Cr-Fe2O3) catalyst by in situ time-resolved X-ray diffraction (TR-XRD) and X-ray Absorption Spectroscopy (TR-XAFS). In these experiments, the evolution of the crystalline structure and electronic state of the catalyst under WGS reaction conditions were followed, at the same time that its catalytic activity was measured. Complementary ex-situ data were obtained by X Ray Photoelectron Spectroscopy (XPS) and transmission electron microscopy (TEM). For comparison, samples of pure hematite (Fe2O3) and hematite promoted only with Cr (Cr-Fe2O3) were also studied. We show that the catalytic activities in the case of Fe2O3 and Cr-Fe2O3 catalysts are related to the Fe2O3 -> Fe3O4 transformation and that the presence of Cr delays this phase transition. In the case of the industrial Cu,Cr-Fe2O3 catalyst, however, the presence of Cu has a major effect, and strongly increases the catalytic activity, even before the full transformation to Fe3O4. The smaller Fe3O4 crystalline domains, detected by TR-XRD in the case of the HTS industrial catalyst, should also contribute to make it the most active catalyst. In-situ TR-XAFS gave complementary information about the changes of Fe, Cr and Cu environments during the activation process. While changes in Cr and Fe environments were detected at similar temperatures, above 300°C, Cu suffers major modification at much lower temperatures, segregating as metallic nanoparticles below 300°C. The formation of this metallic Cu matches the increase of the activity at low temperatures and contributes to the highest catalytic activity of Cu,Cr-Fe2O3 catalyst, compared to Fe2O3 and Cr-Fe2O3 ones. This is an important information revealed by in-situ time-resolved experiments since most of the works about industrial HTS catalysts target the iron oxide phase. It is clear that the Cu plays an important role and optimization of the activation process and performance requires a better understanding about the factors that affects the segregation of the metallic Cu phase.
5:45 PM - NN5.10
Carrier Behavior in a Quantum-confined Material Under High Applied Pressures: Fundamental Insights.
Jeffrey Pietryga 1 , Kirill Zhuravlev 2 , Victor Klimov 1 , Richard Schaller 1 Show Abstract
1 Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, United States
Semiconductor nanocrystal quantum dots (NQDs) are the subject of intensive research because of their unique optical and electronic properties. These properties can differ markedly from those of the corresponding bulk material, but often arise from a combination of both bulk and size-dependent contributions. In fact, many key, fundamental aspects of even the most well-studied NQD systems remain largely theoretical, as strong assertions regarding this interplay between material and confinement effects lack definitive experimental verification even after 15 years of research. This disconnect ultimately limits the rational design of next-generation NQD-based devices, particularly those that strive to take advantage of phenomena unique to NQDs such as carrier multiplication.In this presentation, we describe the use of applied hydrostatic pressure as a powerful tool for studying and decoupling these co-emergent properties in infrared-emitting lead selenide NQDs. In an unprecedented set of correlated experiments, we combine diamond anvil cell techniques, synchrotron x-ray diffraction, and both static and ultra-fast spectroscopy to arrive at new and exciting conclusions about the behavior of excited carriers in this highly relevant material.
NN6: Poster Session
Wednesday AM, December 03, 2008
Exhibition Hall D (Hynes)
9:00 PM - NN6.1
The Initial Oxidation Behavior of CuNi Alloys Observed by in Situ UHV-TEM.
Zhuoqun Li 1 , Judith Yang 1 Show Abstract
1 Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
9:00 PM - NN6.10
Scanning X-ray Diffraction with 200 nm Spatial Resolution.
Michael Hanke 1 , Martin Dubslaff 1 , Martin Schmidbauer 2 , Torsten Boeck 2 , Sebastian Schoeder 3 , Manfred Burghammer 3 , Christian Riekel 3 , Jens Patommel 4 , Christian Schroer 4 Show Abstract
1 Institute of Physics, Martin-Luther-University Halle-Wittenberg, Halle /Saale Germany, 2 , Institute of Crystal Growth, Berlin Germany, 3 , European Synchrotron Radiation Facility, Grenoble France, 4 , Technical University Dresden, Dresden Germany
9:00 PM - NN6.12
Three-Dimensional X-ray Imaging of Neurons in Brain
Jin Kyoung Kim 1 , So Eun Chang 1 , Im Joo Rhyu 2 , Kyoung Tai Kim 1 , Jung Ho Je 1 Show Abstract
1 , POSTECH, PoHang Korea (the Republic of), 2 , Korea University, Seoul Korea (the Republic of)
Three-dimensional (3D) visualization of soft complex structures is a longstanding challenge of broad scientific interest (1). Recent technological advances need a better collaboration between material scientists and biologists to make a significant breakthrough for imaging of brain (neuron imaging) (2). Neurons are characterized by distinct dendritic morphologies that underlie specific functional properties of the cell. Many neuroscientists are interested in observing neuronal structure in detail. Most of neuronal imaging techniques which are currently applicable, despite well established, are still placed in limitations. For instance, computed tomography (CT) or magnetic resonance imaging (MRI) is unable to detect fine micron-structure in spite of providing better quality of images than conventional radiology. Meanwhile light or electron microscopy mostly provides not only narrow field of view but also 2D information of neurons that are present in thin-section of brain slice.To overcome the limitations, we develop a novel technique of X-ray microscopy (3) using coherent synchrotron X-rays that enables to observe neuronal structure from whole cerebellar structure to high–order dendrites of neurons with submicron resolution in mouse brain (4, 5). Just by combining the new technique of synchrotron X-ray microscopy and the well-established technique of Golgi-staining method, we are able to resolve effectively down to high-order dendrites structure. Based on 3D microtomographs of neurons, we quantitatively analyze their morphologies using segmentation, skeletonization, and 3D Sholl analysis (6). In particular we focus on Purkinje and Golgi cells that are two of representative neurons in the cerebellum. These quantitative results might provide a criterion for a quantitative study of neuronal microstructure in the cerebellum.References: (1) F. Lopez-Munoz, et al. Brain Res. Bull. 70, 391 (2006).(2) R. Wingat, et al. Nature Rev. Neurosci. 7, 745 (2006).(3) Y. Hwu, et al. J. Phys. D 35, R105 (2002).(4) R. V. Sillitoe, et al. Annu. Rev. Cell Dev. Biol. 23, 549 (2007).(5) Roy V. Sillitoe, et al. J. Neurosci. 28, 2820 (2008).(6) D. A. Sholl, et al. J. Anatomy 87, Part 4 (1953).
9:00 PM - NN6.13
In-Situ Synchrotron and First-Principles Studies of Oxygen-Induced Surface Structures on Cu (001).
Dillon Fong 1 , H. Iddir 1 , G. Zhou 1 , P. Fuoss 1 , P. Baldo 1 , P. Zapol 1 , J. Eastman 1 Show Abstract
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States
The key to determining the role of oxygen in processes like oxidation, corrosion, and heterogeneous catalysis is in understanding the dynamic interaction between oxygen and metal surfaces. This insight can facilitate the development of greatly enhanced catalysts for reactions like the water gas shift; here improved copper-based catalysts could significantly lower the reaction temperature necessary for hydrogen production. In this study, we investigate the interaction between oxygen and Cu (001) surfaces through a combination of in-situ synchrotron x-ray scattering and density functional theory (DFT) calculations. We find that oxygen adsorption at temperatures above 473 K creates a c(2×2) oxygen layer atop a ¾-filled Cu plane that displays significant outward relaxation. At temperatures below 473 K, the vacancies within the topmost Cu plane undergo a two-dimensional order-disorder transition, forming a (2√2×√2)R45° reconstruction . We will also describe surface stress-induced lattice constant variations in the c(2×2)-O adsorbate islands, the lattice mismatch scaling inversely with island size. These structural results will be compared with measurements of the adsorbate-induced surface stress by the crystal curvature technique and DFT calculations of the surface structure and surface stress, thereby allowing direct insight into the elastic properties of metal surfaces. This work is supported by the U.S. Department of Energy under Contract No. DE-AC02-06CH11357. H. Iddir et al., Phys. Rev. B 76, 241404(R) (2007).
9:00 PM - NN6.14
Investigation of the Morphology of Nanoporous Silicon by Time-resolved Measurement of Changes to the Porosity during Dissolution.
Bernhard Goller 1 , Gazi Aliev 1 , Dmitry Kovalev 1 , Paul Snow 1 Show Abstract
1 Physics, University of Bath, Bath, Somerset, United Kingdom
Information about the morphology of the nanostructured pores in porous silicon can be obtained by a time-resolved measurement of the change in volume fraction of silicon during dissolution in hydrogen fluoride solution. The change of volume fraction (porosity) of the porous layers has been measured in-situ by monitoring the change in the optical density of a porous layer over a 30 hour period. Optical density has been found via the evaluation of interference fringes in the reflectivity spectrum. The porosity is related to effective refractive index using an effective medium approximation for dielectric constant. The porous silicon has been modelled by assuming that the microstructure can be represented as a regular foam either in the form of a regular 2D honeycomb structure of pores penetrating a solid silicon host or as open-faced cells constructed of “girders” of silicon. For the modelled time evolution during dissolution, it is assumed that the thickness of the foam walls decreases at a constant rate. In the literature, recent studies of the elastic properties of porous silicon layers prepared from heavily boron-doped crystalline silicon wafers have suggested that the dependence of the Young’s modulus on porosity is close to that shown by open-faced cellular foam whilst models for the properties of porous silicon are often based on assuming a honeycomb structure. We will present our dissolution results that are consistent with an open-faced cell model for the nanostructure.
9:00 PM - NN6.15
In-Situ Study of Material Response to Single Ion Events,
Yanwen Zhang 1 , William Weber 1 Show Abstract
1 , Pacific Northwest National Laboratory, Richland, Washington, United States
Knowledge of ion-solid interactions and energy deposition during the slowing-down processes in nanomaterials is of fundamental and practical importance. When an ion penetrates a target, it experiences a number of collisions. Energetic charged particles interact with both electrons and atoms in materials. Kinetic energy transfers to atoms can result in displacement of atoms from their original sites; thereby forming atomic-scale defects in the structure. Energy transfers to the target electrons (either bound or free) produces electron-hole (e-h) pairs. Materials respond uniquely to ion energy deposition in picosecond time frame, such as production of atomic-level defects and electron-hole pairs, and associated secondary processes in nanosecond time frame, such as light emission from excitation-induced luminescence. A unique time-of-flight system has been utilized to study material response to single ion irradiation. Electronic energy loss and straggling in nanometer films is measured, which provides the capacity of a projectile to deposit energy in certain depth scale. Material response to the deposited energy is studied over a wide energy range. For semiconductors, the collected charge pulse response to single ions is measured. For scintillators, the photo emission of crystalline or polycrystalline films to single ion events is investigated, and the corresponding light yield, nonlinearity and energy resolution are used to evaluate materials performance for potential optical applications. Furthermore, ion-solid interaction leads to significant production of electron-hole pairs in the vicinity of the defects, local luminescence from the relaxation of the electron-hole pairs at defects may provide a self-excitation probe of defect production. In situ optical techniques to characterize defects and defect accumulation will be presented.
9:00 PM - NN6.16
Combined Spectroscopic Reflectometry and Spectroscopic Ellipsometry (SRSE) of Zinc Oxide (ZnO) and Strontium Titanate (STO) Thin Films.
Dionne Miller 1 , Glen Kowach 1 Show Abstract
1 Chemistry, The City College of New York, New York, New York, United States
The intense focus on the development of practical optoelectronic and photonic devices demands accurate characterization of the optical properties of the materials of interest. Some of these materials include zinc oxide (ZnO) and strontium titanate (STO). Spectroscopic reflectometry (SR) and spectroscopic ellipsometry (SE) are uniquely powerful tools for accurately characterizing the optical properties, structure and thicknesses of thin films. Combining both techniques in one measurement offers many advantages, not the least of which is reduced systematic errors from the simultaneous analysis of multiple data sets. We report for the first time, the use of SR and SE concurrently (SRSE), to successfully develop optical models, and determine the variation in refractive index, n and extinction coefficient, k above and below the band edge of ZnO, for thin films deposited on silicon and platinum substrates at various deposition temperatures to probe the morphological evolution as a function of substrate temperature during deposition. For the first time, a graded layer model is used to model the surface roughness layers to give extremely accurate fits to the data on Pt substrates.We also report the development of an optical model based on reflectometry (SR) data, for STO films deposited on silicon and platinum at various substrate temperatures. The analysis reveals an index gradient in the bulk of the STO deposited on silicon and no interface layer as reported in other publications. These models provide a more accurate description of the morphology of the film surface and the overall thickness useful for in situ measurements.
9:00 PM - NN6.17
In Situ X-ray Diffraction during Molecular-beam Epitaxy of Ge Islands on Si(001).
Takashi Hanada 1 , Osami Sakata 1 , Hiroo Tajiri 1 , Takafumi Yao 1 Show Abstract
1 Institute for Materials Research, Tohoku University, Sendai Japan
9:00 PM - NN6.18
Thermal Transport Across the Gold Nanorod-Solvent Interface, an Investigation of Ligand Effects by a Pump-Probe Laser Technique.
Joshua Alper 1 , Aaron Schmidt 1 , Andy Wijaya 3 , Matteo Chiesa 1 , Gang Chen 1 , Kimberly Hamad-Schifferli 1 2 Show Abstract
1 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Gold nanorods (Au NRs) are a promising material for a variety of applications due to their unique optical properties. The dependence of the optical properties on their easily tunable size and shape, along with the versatile nature of gold surface chemistry, leads to the use of Au NRs in, for example, tumor hyperthermia, drug delivery, and surface enhanced Raman spectroscopy substrates. For many of these applications heat transfer from the Au NR to the surroundings is critical. To analyze these situations, we need the thermal properties of the interface between the Au NR and the solvent. In this study, we characterize the effect of Au NR’s ligand on the nanoscale thermal transport. We determine the thermal interface conductance of a variety of ligand layers. These include hexadecyltrimethylammonium bromide (CTAB) both around and far from the critical micelle concentration, various lengths polyethylene glycol (PEG) chains, various length mercapto-carboxylic acid and, and various length mercapto-alcohols. Using a pump probe technique, we observe the small changes in the absorption of Au NRs excited by a femtosecond pulsed laser. From this, we deduce the lattice temperature as a function of time after a pump pulse. We fit a numerical model to the collected data and extract the interface characteristics of the Au NR-ligand-solvent system. We find that the ligands have a strong effect on the thermal transport, particularly in the diffusion regime (time > 300 picoseconds after the pump). The observations we make, and the conclusions we draw on the nature of ligand layers are useful in characterizing not only the thermal transport across the Au NR-solvent interface, but also in analyzing any thermal application of nanoparticles.
9:00 PM - NN6.2
In Situ Changes in Cerium Oxide Nanoparticles during Electron Irradiation.
Jonathan Winterstein 1 , Joysurya Basu 1 , C. Barry Carter 1 Show Abstract
1 Chemical, Materials and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, United States
Cerium oxide is important for a number of applications related to alternative methods of generating energy such as catalysis and as a fuel-cell electrolyte. Fluorite-structured oxides and other related oxides also display a high resistance to radiation damage and therefore have potential applications in technologies for producing nuclear energy. The usefulness of cerium oxide for these applications is essentially a result of how charged point defects behave in the material. In situ transmission electron microscopy (TEM) on pure and doped nanoparticles of cerium oxide with dimensions on the order of 10 nm has revealed different chemical and microstructural changes occurring during electron irradiation. Electron energy loss spectroscopy (EELS) reveals that the cerium ions can be reduced by irradiation with the beam. The kinetics of reduction vary significantly with dopant chemistry. The particles also sinter during irradiation and the sintering kinetics can be monitored directly. In addition, motion of surface atoms can be observed using high-resolution TEM. The relationship between behavior during irradiation and behavior under a more conventional driving force will be discussed.
9:00 PM - NN6.20
TEM Cross Section Research on the Interface of γ-Al2O3/NiAl Support.
Zhongfan Zhang 1 , Long Li 1 , Sergio Sanchez 2 , Qi Wang 4 , Lin-lin Wang 2 , Duane Johnson 3 , Anatoly Frenkel 4 , Ralph Nuzzo 2 , Judith Yang 1 Show Abstract
1 Mechanical Engineering and Materials Science Department, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 4 Department of Physics, Yeshiva University, New York, New York, United States, 3 Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
9:00 PM - NN6.21
Uncovering the capabilities of Freeze-Fracture Electron Microscopy for Surface Science in the 21st Century.
Alex Wu 1 , Robert Lamb 2 3 , Grainne Moran 1 , Nick Roberts 1 Show Abstract
1 School of Chemistry, University of New South Wales, Sydney, New South Wales, Australia, 2 School of Chemistry, University of Melbourne, Melbourne, Victoria, Australia, 3 , Australian Synchrotron Company Ltd, Clayton, Victoria, Australia
New Presentation Date/Paper NumberTuesday, 12/2NN3.11 to NN6.21Uncovering the capabilities of Freeze-Fracture Electron Microscopy for Surface Science in the 21st Century. Alex Wu
9:00 PM - NN6.3
Nanostructure Evolution of Deposits Grown by Electron Beam Induced Deposition.
Juntao Li 1 , Milos Toth 2 , Vasiliki Tileli 1 , Kathleen Dunn 1 , Charlene Lobo 2 , Bradley Thiel 1 Show Abstract
1 College of Nanoscale Science and Engineering, University at Albany, Albany, New York, United States, 2 , FEI Company, Hillsboro, Oregon, United States
Environmental scanning electron microscopy (ESEM) was used to fabricate tungsten-containing nanostructures by electron beam induced deposition (EBID), using WF6 precursor. High-resolution transmission electron microscopy (TEM), electron-energy-loss spectroscopy, and energy dispersive x-ray spectroscopy were used to characterize deposit nanostructure and composition. The deposits were found to consist of tungsten trioxide (WO3) nanocrystals embedded in an amorphous matrix. An extract of a mass spectrum of the precursor, were obtained during EBID using a differentially pumped mass spectrometer. The spectrum shows the presence H2O, O2, C2H5 and C2H6, which account for the formation of WO3 and the presence of C in the deposits. Under conditions of fixed electron flux, the degree of deposit crystallinity and WO3 grain size were found to increase with deposition time. These changes in nanostructure are ascribed to electron beam induced modification of the deposits occurring during EBID. Monte Carlo simulations of electron energy deposition into WO3-Si multilayers were performed to understand the changes in nanostructure with deposition. The total electron energy deposition profiles calculated as a function of depth for bulk Si, and for multilayers consisting of a WO3 overlayer on bulk Si, were simulated for WO3 thicknesses in the range of 100 to 800 nm. The energy deposition profiles during EBID of the deposits show that the energy deposited per electron per unit depth increases with the thickness of the WO3 overlayer at every point (z) inside the overlayer. Hence, the rate of electron beam induced material modification occurring during EBID is expected to increase with deposition time, consistent with the nanostructure evolution. Possible mechanisms behind the changes in nanostructure, and implications for EBID of functional materials will be discussed.
9:00 PM - NN6.4
Imaging Individual Nanowire Nucleation Events.
Bong Joong Kim 1 , J. Tersoff 2 , K. Dick 4 , C. Wen 1 , S. Kodambaka 3 , E. Stach 1 , F. Ross 2 Show Abstract
1 Materials Science and Engineering, Purdue University, West Lafayette, Indiana, United States, 2 , IBM T. J. Watson Research Center, Yorktown Heights, New York, United States, 4 Solid State Physics, Lund University, Lund Sweden, 3 Materials Science and Engineering, University of California Los Angeles, Los Angeles, California, United States
When considering nanowires as candidates for electronic and optoelectronic elements, a high level of control over their growth is necessary to achieve a successful manufacturing process. In particular, the reliability of nucleation is a critical roadblock that limits nanowire integration. We have therefore examined nucleation in the model systems Si-Au, and here we present a quantitative analysis of both the initial transformation from solid Au to liquid eutectic and the formation of the nanowire nucleus. To model wire growth on amorphous substrates, Au is deposited onto an electron transparent SiN membrane, heated and exposed to disilane in an environmental transmission electron microscope while recording images. Video analysis shows a striking non-linearity in the growth rate of the nuclei which initially increase rapidly then slow down. We present a theoretical framework that balances the roles of supersaturation, pressure and interface energies during nucleation. Using this model we can determine the supersaturation of Si at which nucleation occurs; we show that it is surprisingly high, around 10% in a typical case. We also quantify the distribution of nucleation times in nominally identical Au particles and examine how nucleation times depend on the initial Au geometry, discussing how both effects relate to wire uniformity. The results of these studies show that it is possible to observe and analyse individual nucleation events in nanoscale systems, with results that may be relevant to the formation of nanostructures for real-world applications.
9:00 PM - NN6.5
A SWNT Synthesis Apparatus for Multivariable Analysis of Nucleation and Growth Factors.
David Liptak 1 2 , Roberto Acosta 1 3 , Benji Maruyama 1 Show Abstract
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States, 2 , UES, Inc., Dayton, Ohio, United States, 3 Department of Physics, Wright State University, Dayton, Ohio, United States
9:00 PM - NN6.6
In Situ EELS in the Study of Dehydration of Mg(OH)2 by Electron Beam.
Nan Jiang 1 , Dong Su 1 , John Spence 1 Show Abstract
1 Physics, Arizona State University, Tempe, Arizona, United States
Nanocrystalline magnesium oxide MgO has attracted substantial interest for its voracious adsorbent properties due to enhanced surface areas and high surface reactivity [1, 2]. Instead of the complicated chemical synthesis or thin film deposition, nanocrystalline MgO can be obtained easily using a thermally activated dehydration process from Brucite Mg(OH)2 at about 450C . During the dehydration reaction, the external shape and dimensions of Mg(OH)2 crystals was retained, while the volume of the MgO unit cell was reduced from the unit cell of Mg(OH)2, which makes MgO a porous material, with nanoscale pores. The decomposition of Mg(OH)2 also occurs in the transmission electron microscope (TEM), induced by electron irradiation [3 – 6]. Interestingly, the dehydration products of MgO in TEM have very similar morphology to that obtained by thermal methods. Their crystallographic relationship with the parent Mg(OH)2 are also similar [ref]. Therefore, it was believed that the dehydration of Mg(OH)2 in TEM was induced by the temperature rise caused by the electron beam, and the mechanisms were considered to be the same [3 – 6].Here, we report experimental observations of dehydration processes in Mg(OH)2 caused by an electron beam, using in situ electron energy-loss spectroscopy (EELS). One of the advantages of EELS over imaging and diffraction techniques is that EELS is more sensitive to the changes in local structure and chemistry. The new evidence shows that the dehydration in Mg(OH)2 using an electron beam is in fact different from that due to thermal annealing. During dehydration in Mg(OH)2, both low energy-loss spectra and the Mg L23 edge show the existence of partially oxidized Mg or O-deficient MgO in the dehydrated products, which is not seen in the thermally dehydrated MgO. Possible mechanisms of dehydration by electron beam may involve hydrogen sputtering by high-energy electrons, followed by release of O, which results in the collapse of layered Mg(OH)2 structure into MgO, accompanied by formation of partially oxidized or O-deficient MgO clusters or layers.This work is funded by the NSF DMR-0603993. The use of the facility within the Center for Solid State Science of ASU is also acknowledged. R. Richards, W. F. Li, S. Decker, C. Davidson, O. Koper, V. Zaikovski, A. Volodin, T. Rieker, K. J. Klabunde, J. Am. Chem. Soc. 122, (2000) 4921.  A. Khaleel, P. N. Kapoor, K. J. Klabunde, Nanostruct. Mater., 12, (1999) 463.  R. R. Balmbra, J. S. Clunie, and J. F. Goodman, Nature (London) 209, (1966) 1083. U. Dehmen, M. G. Kim, and A. W. Searcy, Ultramicroscopy 23, (1987) 365.  P. A. Van Aken, and F. Langenhorst, Eur. J. Mineral. 13, (2001) 329. J. F. Goodman, Proc. Roy. Soc. (London) A 247, (1958) 346.
9:00 PM - NN6.8
X-Ray Microdiffraction in Conjunction with Discrete Dislocation Dynamics to Reveal Grain Boundary-dislocation Interaction Mechanisms.
Ralph Nyilas 1 , Miroslav Kobas 2 , Ralph Spolenak 1 Show Abstract
1 Department of Materials, ETH , Zürich Switzerland, 2 , Swiss Light Source, Villingen Switzerland
Understanding the deformation mechanism of polycrystalline thin metal films on the mesoscale (0.1-10 micron) is crucial for the design and fabrication of microelectronic components. To date, the mechanical response of polycrystalline materials on the mesoscale cannot be understood adequately by continuum mechanics as it is largely determined by the discrete underlying microstructure and grain-to-grain interactions. Local submicron in situ strain and orientation measurements by X-Ray microdiffraction are the key to provide insight into the mechanism of deformation heterogeneities in polycrystalline ensembles. We conducted white beam X-Ray synchrotron microdiffraction experiments at the Swiss Light Source on thin gold films to locally map orientations and strain tensors over a polycrystalline ensemble. The gold films were in situ thermally strained over the complete strain hysterises cycle. We implemented second generation photon counting detector technology obtaining Laue microdiffraction patterns superior in the signal-to-noise ratio compared to conventional CCD detector systems. The local strain tensor and orientation maps in conjunction with a detailed peak profile analysis allowed us to reconstruct the deformation mechanism of several grains within the polycrystalline ensemble. We demonstrate a correlation between the directions of the maximum resolved shear stresses within the grain and an increase/decrease in the misorientation angle of the grain boundaries. The latter observation is interpreted as the transport of polar dislocation density between the grain boundaries. The elastic stress tensor maps show the development of a gradient in the normal and shear stress components around an individual grain prior to a shear and rotational deformation. We implement a discrete disclocation dynamics model simulating the annihilation reaction between edge dislocations emitted from the boundaries. The results suggest a supply of polar dislocation density from the surrounding grains and grain interior via the triple junction entry points to be necessary to generate the experimentally observed magnitude of rotation.
9:00 PM - NN6.9
Kinetic Studies of Initiated Chemical Vapor Deposition of Polymer Nanocoatings.
Gozde Ozaydin-Ince 1 , Karen Gleason 1 Show Abstract
1 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Polymer films formed by the initiated chemical vapor deposition of vinyl monomers have applications ranging from conformal coatings of multiwall carbon nanotubes and microspheres to superhydrophobic fabrics. Copolymer film formation by including divinyl crosslinkers in the deposition process enhances mechanical properties and increases the resistance against solvents which is crucial for fabrication of air-gap structures. In this work, systematic in-situ kinetic studies of the initiated chemical vapor deposition of vinyl monomers and divinyl crosslinkers are performed and the effects of process parameters on deposition are investigated. The reactions are monitored with a gas phase FTIR (Induct 3100 Process Analyzer from MKS). Real-time quartz-crystal microbalance measurements are performed to correlate the surface adsorption to deposition rates. Tert-butyl peroxide is used as the initiator for all depositions.In-situ gas phase FTIR measurements are performed to obtain the concentrations of each chemical during the reaction. Concentrations are calculated by calibrating the carbonyl peaks of the monomers with known concentration values in ppm. Detection limit for the vinyl monomers is approximately .1 ppm.Residence time studies are performed at different reactor pressures and an optimal operating pressure of approximately 200 mTorr for a plug flow is determined. Deposition rates obtained at this operating pressure ranges from 5 nm/min to 70 nm/min for different process parameters.Studies performed at different filament temperatures, ranging from 180oC to 360oC, clearly show the kinetic and mass transfer limited regimes from which the apparent activation energies are extracted. The transition to a mass transfer limited regime is typically observed in the range of 230oC to 270oC. The separate studies of deposition rate dependence on the initiator and the monomer concentrations enable us to determine the reaction rate constant and the order of reaction. The effect of monomer flow on the deposition rate is studied for different flowrates. The overall deposition rate is then correlated to the monomer concentration on the surface by the utilization of the gas phase FTIR and the results are compared to QCM measurements which show a constant deposition rate throughout the experiments. In the final set of experiments, the effects of substrate temperature variations on the deposition rate are studied. The substrate temperature range studied is from 15oC to 45oC. The adsorption kinetics are discussed by using the relation between the substrate temperature variations and the variations in Pm/Psat values for the same flowrates.