Symposium Organizers
John Cumings University of Maryland
Dillon Fong Argonne National Laboratory
Jianyu Huang Sandia National Laboratories
Stuart Lindsay Arizona State University
Guangwen Zhou State University of New York, Binghamton
SS1: Advanced Imaging with X-Rays
Session Chairs
Paul Fenter
David Jacobson
Monday PM, November 29, 2010
Gardner (Sheraton)
9:15 AM - **SS1.1
X-ray Microscopy.
Janos Kirz 1
1 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractX-rays penetrate objects opaque to electrons and visible light. X-ray spectra near absorption edges reveal the local chemical environment. Linear and circular dichroism provide contrast in magnetic materials. Advances in X-ray optics, as well as lensless imaging methods, provide high spatial resolution. X-ray free-electron lasers coming on line may open the door to sub-nm resolution imaging of macromolecules.
9:45 AM - SS1.2
3D Imaging of Whole, Unstained Cells by Using X-ray Diffraction Microscopy.
Huaidong Jiang 1 2 , Changyong Song 3 , Tetsuya Ishikawa 3 , Fuyu Tamanoi 4 , Jianwei Miao 1
1 Physics And astronomy, University of California Los Angeles, Los Angeles, California, United States, 2 State Key Laboratory of Crystal Materials, Shandong University, Jinan, Shandong, China, 3 , RIKEN SPring-8 Center, Hyogo Japan, 4 Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles,, Los Angeles, California, United States
Show AbstractCoherent diffraction microscopy (also termed coherent diffractive imaging) is a lensless imaging technique in which the coherent diffraction pattern of a non-crystalline specimen or a nanocrystal is measured and then directly phased to obtain an image. The well-known phase problem is solved by using the oversampling method in combination with the iterative algorithms. Since its first experimental demonstration in 1999, coherent diffraction microscopy has been applied to imaging a wide range of materials science and biological specimens such as nanoparticles, nanocrystals, biomaterials, cells, cellular organelles, viruses and carbon nanotubes by using synchrotron radiation, high harmonic generation and soft X-ray laser sources, free electron lasers and electrons [1,2]. Here we apply coherent X-ray diffraction microscopy to quantitative 3D imaging of a whole, unstained yeast spore at a resolution of 50–60 nm [3]. We identified the 3D morphology and structure of cellular organelles including spore wall, vacuole, endoplasmic reticulum, mitochondria, granules, nucleus and nucleolus inside a yeast spore cell. Furthermore, we observed a 3D structure protruding from the reconstructed yeast spore, suggesting the spore germination process. This work hence paves a way for nondestructive 3D characterization of a wide range of biological specimens at nanometer-scale resolutions that are too thick for electron microscopy. References:[1] J. Miao, P. Charalambous, J. Kirz and D. Sayre, Nature 400, 342-344 (1999).[2] J. Miao, T. Ishikawa, T. Earnest and Qun Shen, Annu. Rev. Phys. Chem. 59, 387-409 (2008).[3] H. D. Jiang, C. Song, C. C. Chen, R. Xu, K. S. Raines, B. P. Fahimian, C. H. Lu, T. K. Lee, A. Nakashima, J. Urano, T. Ishikawa, F. Tamanoi & J. Miao, Proc. Natl. Acad. Sci. USA, 107, 11234-11239.
10:00 AM - SS1.3
Coherent X-Ray Diffraction Characterization of Epitaxial Bi2O3 Nanostructures.
Stephan Hruszkewycz 1 , Paul Fuoss 1 , Martin Holt 2 , Ross Harder 3 , Ash Tripathi 4 , Matt Highland 1 , Joerg Maser 2 , Dillon Fong 1 , Danielle Proffit 1 5 , Gou-Ren Bai 1 , Jeff Eastman 1
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Center for Nanoscale Materials, Argonne National Laboratory, Argonne , Illinois, United States, 3 X-Ray Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 4 Department of Physics, University of California San Diego, San Diego, California, United States, 5 Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractX-ray coherent diffraction imaging (CXDI) techniques have the potential to nondestructively resolve structural features in complex samples in extreme environments with, potentially, wavelength-limited resolution. We are using CXDI to study the structural properties of δ Bi2O3 nanostructures grown on single crystal (001) surfaces of SrTiO2. δ Bi2O3 is an exceptionally good oxygen conductor that could greatly improve the performance of devices relying on high ionic conductivity. In the bulk, δ Bi2O3 is only stable at high temperature (from approximately 725 to 825°C). However, we have recently succeeded in stabilizing this phase at room temperature via strained, epitaxial growth. We have collected three dimensional Bragg coherent diffraction data from individual 300-900 nm sized δ and β Bi2O3 particles using both focused and parallel coherent radiation at the Advanced Photon Source in order to image internal particle strain fields and to better understand the role of epitaxial strain in Bi2O3 nanostructure phase differentiation. We will discuss techniques to measure high quality coherent diffraction and approaches to invert that data to obtain real space, three-dimensional images of the density and internal strain of the particles. Further development of x-ray CDI techniques will open the door to a wide range of in situ studies of nanostructured oxide samples by imaging the evolution of internal strain fields of individual structures during various stages of growth or as a function of temperature and partial oxygen pressure.
10:15 AM - SS1.4
In-situ Study of Dealloying of Nanoporous Gold using Transmission X-ray Microscopy.
Yu-chen Chen 1 2 , Steve Wang 2 , Wah-Keat Lee 2 , Peter Voorhees 1 , Ian McNulty 2 , David Dunand 1
1 Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States, 2 Advance Photon Source, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractDealloying to fabricate nanoporous metallic structures (with potential applications including catalysis, sensors and actuators) typically involves dissolving a less noble element from an alloy system using electrochemical means. This results in a fairly complicated three-dimensional interconnected porous structures, with pores ~5-30 nm in size. We studied dealloying of silver-gold alloy to form nanoporous gold to establish a theoretical understanding of dealloying and the structure-property relationship in these nano-foams. High resolution imaging has proven indispensable to study the interconnected structures in nanoporous metals. For instance, 3D imaging by tomography has been done using both the transmission electron microscope and x-ray transmission microscope. However, no direct imaging to study the structural evolution and the kinetic of the dealloying process has been reported, mainly because of the corrosive liquid environment, and the nanometer imaging resolution required.X-ray techniques are ideal for probing structural evolution in-situ. Here, we use transmission x-ray microscopy at the Advanced Photon Source to directly observe the dealloying front propagation, corresponding to the interface between the dealloyed nanoporous gold and the non-dealloyed silver-gold alloy. The kinetics of dealloying are determined quantitatively from the analysis of in-situ measured image series. In addition to the dealloying kinetics, the experimental technique is also discussed. The spatial and time resolution of this work (~50 nm, on the order of seconds), and the capability to study thick samples (tens of microns) were made possible by combining nano-fabricated x-ray optics with the brilliance of a third-generation synchrotron x-ray source.
10:30 AM - SS1.5
X-ray Dual Imaging of Droplet Evaporation.
Byung Mook Weon 1 2 , Jung Ho Je 1 , Christophe Poulard 3
1 X-ray Imaging Center, Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of), 2 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 3 Laboratoire de Physique des Solides, Universite Paris-Sud 11, Orsay France
Show AbstractDroplet evaporation on solid surfaces is a topic of great current interest and plays a key role in natural and technological processes such as coffee-ring formation and drying-mediated self-assembly. The static situation of a gas-solid-liquid contact line is well explained by the Young theory based on the balance of surface tensions at the droplet edge. The dynamical situation during evaporation is often complicated by the fact that the edge of the drying droplet gets ‘pinned’ at points on the surface. Although most liquid droplets follow classical diffusion-limited drying kinetics through a proportion of evaporation rate with contact radius, water droplets often show abnormal behaviors. Abundant experiments on evaporating sessile droplets suggest that contact radius and contact angle have power-law time dependences. To understand droplet evaporation, we need to precisely measure the scaling exponents and the vanishing time of the power-law dependences in real time. In this study, we develop a dual imaging method of combining X-ray transmission and reflection, which allows two and three dimensional information of drying drops in real time by simultaneously taking transmission and reflection images at a grazing angle (~1.3 mrad) using synchrotron X-ray microscopy (from the PLS 7B2 beamline, Pohang, Korea). This in-situ imaging method allows precise measurements of droplet geometry and drying time from nanoliter drops of 3 to 500 nl, which are very small compared to drops of 1 to 3 µl studied in common methods. We find that wetting modes modulate drying rates of nanoliter water drops on silicon surface; specifically, receding drops evaporate faster than pinning, shrinking, or spreading drops. We suggest a general relation to link evaporation rate and contact radius synchronously evolving in drying and wetting dynamics. For in-situ studies of drying sessile drops or thin liquid films, it can be a worthy strategy to use the dual imaging method of combining X-ray transmission and reflection.
11:15 AM - **SS1.6
Imaging Interfacial Topography and Reactivity using X-ray Reflection Interface Microscopy (XRIM).
Paul Fenter 1
1 Chemical Sciences and Engineering, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractA fundamental understanding of interfacial reactivity is essential for a diverse range of fields ranging from geochemistry to materials science. X-ray reflection interface microscopy (XRIM) is a powerful new tool for interfacial studies that uses the weak interface-reflected X-ray beam to image a surface through full-field imaging. It therefore incorporates all of the sensitivities of X-ray reflectivity (XR), including sensitivity to interfacial topography, structure and composition, along with the ability to spatially resolve laterally heterogeneous interfacial structures and processes. This presentation will review recent applications of XRIM. Initial ex-situ observations performed on the orthoclase KAlSi3O8 (001) surface have: demonstrated the ability to see elementary surface topography (i.e.,. 6.5 Å-high steps) with ~100 nm spatial resolution [1]; clarified the basis for XRIM image contrast [2]; and demonstrated the first use of XRIM to image interfacial reactivity [3]. Ongoing work to establish the feasibility of XRIM as an in-situ probe of mineral-water interfaces will also be presented. I will describe the challenges associated with in-situ imaging, including an intrinsically smaller signal strength as well as the limitations associated with interfacial damage associated wtih water radiation chemistry. Future planned improvements of the resolution, contrast, and throughput of the XRIM instrument will be discussed, especially in the context for the use of XRIM as an in-situ real-time probe of interfacial processes.References:[1] Fenter et al., Nature Physics 2(10) 700-704 (2006).[2] Fenter et al., Journal of Synchrotron Radiation, 15, 558-571 (2008). [3] Fenter et al., Geochimica et Cosmochimica Acta, 74, 3396-3411 (2010). This work supported by the Geoscience Research Program of the US Department of Energy, Office of Basic Energy Sciences. This work is done in collaboration with M. J. Bedzyk, J. Catalano, S. S. Lee, C. Park, N. C. Sturchio, Z. Zhang, and P. Zschack.
11:45 AM - SS1.7
Strain Screening by Mobile Oxygen Vacancies in SrTiO3.
Yongsam Kim 1 , Ankit Disa 1 , Timur Babakol 1 , Joel Brock 1
1 Applied Physics, Cornell University, Ithaca, New York, United States
Show AbstractRecently, Freedman et al. [Phys. Rev. B 80, 064108 (2009)] calculated the elastic dipole tensor for several types of point defects in SrTiO3 and showed that it is nearly traceless for oxygen vacancies. Thus, mobile oxygen vacancies are predicted to screen elastic strain fields. Here, we review our report [Appl. Phys. Lett. 96, 251901 (2010)] of detailed diffuse x-ray scattering measurements of bulk SrTiO3 crystals prepared with controlled oxygen vacancy distributions. We verify the traceless nature of the elastic dipole tensor of an oxygen vacancy and demonstrate both correlations between oxygen vacancies and elastic strain screening by oxygen vacancies. We then discuss extensions of this work to in situ surface studies, specifically on the possibility of measuring the oxygen vacancy concentration during thin film growth.
12:00 PM - SS1.8
Simultaneous Time Resolved X-ray Phase Contrast Imaging and X-ray Diffraction Investigations of Irreversible Phase Transformations During Rapid Heating.
Stephen Kelly 1 , Sara Barron 1 , Timothy Weihs 1 , Kamel Fezzaa 2 , Todd Hufnagel 1
1 Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 2 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractHighly localized, rapidly changing irreversible transformations present a particularly difficult problem for traditional structural and microstructural characterization techniques. For instance, self propagating high temperature synthesis reactions in metal laminate foils can occur as localized reaction fronts ~100 µm wide traveling at speed of ~10 m/s, reaching temperatures above 1500 °C in under 100 µs. While time resolved x-ray microdiffraction can reveal the sequence of phase formation in these reactions, it provides little information about the real-space morphology of the reaction front and subsequent grain growth in the reacted film. In comparison, recent advances in high-speed x-ray phase contrast imaging techniques now permit direct observation of sample microstructure with micron-scale spatial resolution and microsecond temporal resolution, but provide little information about the phases formed during the reaction.We have developed a hybrid technique which combines simultaneous x-ray diffraction and high-speed x-ray phase contrast imaging in order to leverage the advantages of each individual technique. We illuminate the sample with an unfocused white (~12.4 keV with ~5% bandwidth and ~6 x 1014 ph/s in the fundamental emission peak) x-ray beam from an undulator source and image the sample using a high-speed optical CMOS camera to record the light from a LYSO:Ce scintillator crystal at a frame rate of 135780 frames per second with a 500 ns exposure time per frame. Simultaneous to this we collect the scattered x-rays on a fiber-optic coupled x-ray CCD camera over the 1-2 ms total x-ray exposure time as defined with a fast x-ray shutter. As an example, we present recent results using this technique to observe the passing reaction front in self propagating high temperature synthesis reactions in metal laminate foils containing alternating layers of Al and Zr. In foils with overall composition AlZr and 85 nm bilayer period (the combined thickness of one Al and one Zr layer) we observe a reaction front with a complex, scalloped shape and a resulting striated microstructure after the front passes. Diffraction patterns collected simultaneously indicate a transformation from the initial Al and Zr phases to the AlZr intermetallic phase (B33 structure) as well as Al3Zr2 and the high temperature Al4Zr5 phase. In contrast, foils with overall composition Al3Zr transition via the passage of a relatively planar reaction front while transforming from the Al and Zr initial phases to the intermetallic phase Al3Zr.
12:15 PM - **SS1.9
Shape Reconstruction of Nanoparticles under Reaction Conditions.
Andreas Stierle 1
1 Solid State Physics / Interfaces, Universitaet Siegen, Siegen Germany
Show AbstractSubstantial effort was made within the past few decades to understand the fundamentals of oxidation using pioneering-type experiments under highly idealized conditions, such as very low oxygen pressures (10-6 mbar), and very idealized model systems (single crystal surfaces). However, understanding chemical reactions on single crystal surfaces in vacuum very often does not allow prediction of the performance of devices composed of nanoparticles operating at ambient gas pressure, such as catalysts or gas sensors. In my talk I will present a systematic investigation of model systems with increasing complexity (single crystal & vicinal surfaces, epitaxial nanoparticles on single crystal oxide supports). I will demonstrate how synchrotron radiation based x-ray diffraction can be performed under near-atmospheric pressures and elevated temperatures, providing atomistic inside into the structure of metal nanoparticles during oxidation and reduction cycles. In addition, I will present a novel high energy x-ray diffraction scheme for nanoparticles. Together with a combinatorial sample preparation strategy it allows one to do systematic particle size dependent chemical reaction experiments.
SS2: In-Situ Beam Scattering Studies
Session Chairs
Janos Kirz
Andreas Stierle
Monday PM, November 29, 2010
Gardner (Sheraton)
2:30 PM - **SS2.1
Neutron Radiography and Tomography for In Situ Imaging of Hydrogen and Lithium.
David Jacobson 1 , Daniel Hussey 1 , Elias Baltic 1
1 Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show AbstractNeutron imaging as a method to perform in-situ studies of hydrogen fuel cells, hydrogen storage devices, heat pipes, and batteries has made tremendous progress in recent years. Neutrons are useful to study light elements mixed with heavy Z elements where penetration by other forms of radiation is either impossible or incapable of contrasting the light elements. Useful spatial resolution available at neutron imaging facilities is now approaching 10 micrometers. Complimentary time resolution of 30 frames per second or greater is also possible with a spatial resolution approaching 300 micrometers. Here we will provide an overview of the technique of neutron imaging and the facilities around the world that are available for experimental studies with neutrons. Examples of in-situ studies of fuel cells, hydrogen storage devices, heat pipes and batteries will also be presented.
3:00 PM - SS2.2
Modern Diffraction Methods Applied to Thermo Mechanical Processes in Materials Science.
Klaus-Dieter Liss 1
1 The Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales, Australia
Show AbstractPhysical thermo-mechanical simulation is widely used to evaluate micro-structural changes in metals as they occur in production, manufacturing or application processes. Conventionally, such studies are undertaken by mechanical and heat treatment of the material, subsequently quenched and analyzed, and then repeated for various temperature and load parameters.Both neutron and high energy synchrotron radiation are penetrating and allow to investigate the bulk of materials in-situ and in real time. However, the two kinds of radiation differ in brilliance, beam size and interaction with the materials. Neutron radiation bears the advantage to average over larger sample volumes and therefore provide a good powder average, even in coarse grained material, as needed for quantitative phase analysis and the determination of global texture. The different scattering lengths between the two types of radiation can be used to enhance the contribution of particular species of atoms and, in some cases, like in TiAl, be particularly sensitive to atomic order and disorder. Synchrotron high energy X-rays around 100 keV as delivered by undulator beamlines are highly bundled to investigate the local structure of the specimen. Large area high-resolution two-dimensional detectors are employed for a multi-dimensional exploitation of the diffraction patterns and are now fast enough to follow essential steps in real time. Examples shall be presented on selected metallic systems undergoing thermo-mechanical load, revealing features like grain correlations upon phase transformations, grain refinement, subgrain formation, grain rotation, dynamic recovery, dynamic recrystallization, grain growth and the evolution of texture. In order to cope with ever increasing demands in industry-relevant processes, it is proposed, that future thermo-mechanic simulation takes place routinely in a beam of a large user facility.
3:15 PM - SS2.3
In Situ Acoustic Emission and XRD from Cycling Lithium Ion Batteries.
Kevin Rhodes 1 2 , Edgar Lara-Curzio 2 , Nancy Dudney 2 , Claus Daniel 1 2
1 Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee, United States, 2 Materials Science and Technology, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractAs LIB’s cycle, stress and strain develop in active electrode materials and can be accompanied by phase changes and fracture. These phenomena can degrade the performance of the LIB and even lead to its eventual failure. Understanding how these changes occur is the first step to preventing them and novel characterization techniques that can give a fresh perspective are well worth investigating. Acoustic emission (AE) is nondestructive technique capable of recording ultrasonic sounds that may arise from events such as cracking or bubbling. AE has been applied to the in situ study of battery materials as they are cycled. Here AE was combined with X-ray diffraction to study the correlation of lattice parameters and phase composition with the onset of fracture detection. Copper sputtered disks of polyethylene terephthalate were laminated with silicon slurry to make composite electrodes which were assembled versus lithium in coin cell hardware modified to include a port where X-rays may penetrate. Cells were cycled and changes to the active material were monitored. This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725, was sponsored by the Vehicle Technologies Program for the Office of Energy Efficiency and Renewable Energy. Parts of this research were performed at the High Temperature Materials Laboratory, a National User Facility sponsored by the same office.
3:30 PM - SS2.4
In-situ Neutron Diffraction Studies of Energy Related Materials.
Ashfia Huq 1 , Jason Hodges 1 , Olivier Gourdon 2 , Luke Heroux 1
1 Neutron Scattering Science Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Jülich Centre for Neutron Science, Outstation at Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractPOWGEN is a fundamental departure from previous designs for a time-of-flight powder diffractometer at a spallation neutron source and may be considered a third-generation design. The instrument is optimized for both parametric studies of materials under a wide range of conditions (T, P, H, flowing gases, etc) and ab-initio crystal structure determinations of complex solid-state materials with asymmetric unit-cells of the order ~1500 Å3. The geometric design of the instrument allows for all detected scattered neutrons to be focused onto a single diffraction profile yielding high count rate while preserving good resolution Δd/d = 0.0015 at d = 1 Å. This design along with the high penetration properties of neutron makes it an ideal instrument to do in-situ measurements of materials such as solid oxide fuel cell, battery materials, catalysis etc. To this end we have developed an integrated gas handling system that allows the users to flow various different gases to achieve various levels of partial pressure of oxygen while collecting neutron diffraction data. Preliminary results of such in-situ measurements from this instrument will be the topic of this presentation.SNS is operated with the support from the Division of Scientific User Facilities, Office of Basic Energy Sciences, US Department of Energy, under contract DE-AC05-00OR22725 with UT-Battelle, LLC.
3:45 PM - SS2.5
Fast in-situ Neutron Diffraction Measurements during Cyclic Deformation using the VULCAN Diffractometer at the Spallation Neutron Source.
Alexandru Stoica 1 , Ke An 1 , Sheng Cheng 2 , Harley Skorpenske 1 , Xun-Li Wang 1
1 NSSD, ORNL, Knoxville, Tennessee, United States, 2 MSE, UTK, Knoxville, Tennessee, United States
Show AbstractThe neutron diffractometer VULCAN, recently commissioned at the Spallation Neutron Source, Oak Ridge National Laboratory, provides exquisite capabilities to investigate fast cyclic phenomena due to the high beam intensity, as well as, the novel data acquisition system based on event mode data storage. Using VULCAN, we were able to demonstrate a data collection time down to 10 s, and the ability to measure directly the lattice strain evolution for cyclic uni-axial deformation at 0.01Hz. For higher frequencies, up to 1 Hz, we introduced a stroboscopic technique of averaging the diffraction data over a few cycles. A time-frequency representation was developed to characterize the lattice strain amplitudes and phase evolution during the fatigue life. Our study on a model alloy system, 316LN stainless steel, reveals the evolution of intergranular strains and tension-compression asymmetry, as well as, the intragranular strain development due to the accumulation of dislocation debris. The results are compared with our previous measurements performed ex-situ or in-situ at a slow deformation rate.
4:30 PM - SS2.6
Quantitative X-ray Synchrotron Analysis of the FFC Cambridge Process.
Rohit Bhagat 1 , David Dye 2 , Seema Raghunathan 2 , Douglas Inman 2 , Kartik Rao 3 , Richard Dashwood 1
1 , University of Warwick, Coventry United Kingdom, 2 , Imperial College London, London United Kingdom, 3 , Metalysis Ltd, Sheffield United Kingdom
Show AbstractDespite over ten years of research into the low-cost electrowinning of titanium direct from the oxide, the reduction sequence of TiO2 pellets in molten CaCl2 has been the subject of debate, particularly as the reduction pathway has been inferred from ex-situ studies. Here, for the first time white beam synchrotron X-ray diffraction is used to characterise the phases that form, in-situ during reduction and with ~100 um spatial resolution. It is found that TiO2 becomes sub-stoichiometric very early in reduction facilitating the ionic conduction of oxygen ions, that CaTiO3 persists to nearly the end of the process and that, finally, CaO forms just before completion of the process. The method is quite generally applicable to the in-situ study of industrial chemical processes. Implications for the industrial scale-up of this method for the low-cost production of titanium are drawn.
4:45 PM - SS2.7
Towards in-situ Monitoring of Structural Changes in Inorganic Materials by Synchrotron Laue X-ray Microdiffraction.
Catherine Dejoie 1 , Martin Kunz 1 , Nobumichi Tamura 1 , Colin Bousige 2 , Kai Chen 3 , Simon Teat 1 , Christine Beavers 1 , Lynne McCusker 4 , Christian Baerlocher 4
1 ALS, LBNL, Berkeley, California, United States, 2 , ILL, Grenoble France, 3 Department of Earth and Planetary Sciences, UC Berkeley, Berkeley, California, United States, 4 Laboratorium f. Kristallographie, ETH Zürich, Zürich Switzerland
Show AbstractLaue X-ray microdiffraction is a powerful tool for mapping grain orientation and strains in polycrystalline materials and single crystals with submicron spatial resolution. The use of white radiation allows simultaneously satisfying Bragg condition for a number of reflections. A single Laue pattern obtained using an area detector is therefore all what is required to determine crystal orientation as well as measuring crystal distortion and thus strain. This allows for rapid data collection limited only by the speed of the equipment (detector, sample stage) and the number of x-ray photons, so that in-situ studies of the evolution of material microstructures is possible. Examples of the use of Laue X-ray microdiffraction include the study of the effect of electromigration on the microstructure of metal interconnects. However, Laue diffraction is intrinsically "blind" to the wavelengths causing the reflections so that the use of the intensity of the reflections besides their positions is usually neglected. The systematic exploitation of the reflection intensities opens new possibilities in the use of Laue X-ray microdiffraction. It would allow precisely monitoring rapid structural modifications as well as determining structure of unknown crystals in difficult cases not solvable by conventional monochromatic techniques (such as very small crystals, crystals embedded in a heterogeneous matrix, non stationary sample in suspension in a liquid or inside a diamond-anvil cell). In an effort toward this step, we devise ways to extract the integrated intensities from a Laue pattern in cases where high reflection redundancy cannot be achieved (typically for small unit cell crystals of inorganic compounds and small molecules). The data reduction process involves determining a number of corrective factors specific to broad bandpass diffraction such as harmonic deconvolution and the incident white beam flux curve.
5:00 PM - SS2.8
Spatially-Resolved X-ray Microdiffraction Studies of the Metal-Insulator Transition in Vanadium Dioxide.
John Budai 1 , Alexander Tselev 1 , Jonathan Tischler 1 , Sergei Kalinin 1 , Andrei Kolmakov 2
1 , Oak Ridge National Lab, Oak Ridge, Tennessee, United States, 2 , Southern Illinois University Carbondale, Carbondale, Illinois, United States
Show AbstractWe have used scanning x-ray microdiffraction to investigate domain formation and local microstructural changes associated with the metal-insulator transition (MIT) in the strongly-correlated electron material, vanadium dioxide (VO2). The in-situ experiments were performed at the Advanced Photon Source beamline 34-ID-E with a polychromatic (~8-25 keV) x-ray beam focused to a diameter of ~400 nm by Kirkpatrick-Baez mirrors. Bulk VO2 exhibits a first-order phase transition from a high-temperature, tetragonal (rutile) metal to a lower-symmetry monoclinic (M1) insulator at around 67°C. We investigated samples consisting of quasi-two-dimensional VO2 micro-platelets (~600 nm thick, <10 μm wide and up to a few hundred μm long) grown by vapor transport on thin SiN membranes and on Si wafers. In these quasi-2D microcrystals, the MIT behavior can be affected by substrate-induced strain and by geometrical frustration. By scanning the focused x-ray beam over individual microcrystals and analyzing the Laue diffraction patterns, we obtained spatially-resolved maps of the crystal structure (phase) and orientation as a function of temperature. In addition, by inserting a double-crystal monochromator into the beam and measuring the energy for a particular Bragg peak, the lattice strain was mapped. At room temperature, the individual microcrystals contained four different orientations of M1 twin domains, typically with lamellar patterns in narrow microcrystals and more complex labyrinth patterns in wider crystals. These ferroelastic homophase domains are presumably caused by strain minimization as the lower-symmetry monoclinic phase is formed during cooling. At intermediate temperatures near the MIT, phase coexistence was observed in some microcrystals, and the microstructure within a particular platelet depended on substrate-induced strain and on the crystal morphology. At high temperatures, each platelet transformed to a rutile single crystal. In this talk, we will discuss both the MIT results for VO2 microcrystals and the general use of Laue x-ray microdiffraction for in-situ, spatially-resolved scattering studies._ _ _ _ Research supported by the U.S. DOE, Basic Energy Sciences, Materials Sciences and Engineering Division (JDB, JZT), by the BES Scientific User Facilities Division (AT, SK) and by the NSF (AK, sample growth). XOR-UNI at APS supported by DOE BES Scientific User Facilities Division.
5:15 PM - SS2.9
X-ray Diffraction Study of Nanoporous Gold.
Steven Van Petegem 1 , Andrea Hodge 2 3 , Jurgen Biener 2 , Helena Van Swygenhoven 1
1 NUM/ASQ, Paul Scherrer Institut, Villigen PSI Switzerland, 2 , Lawrence Livermore National Laboratory, Livermore, California, United States, 3 , University of Southern California, Los Angeles, California, United States
Show AbstractRecently nanoporous metals synthesized by selective dealloying of binary alloys have attracted considerable attention because to their possible application as sensors or actuators. These materials exhibit a sponge-like structure with a pore size distribution on the nanometer length scale. Special attention has been given to the Ag-Au model system because it can be synthesized with a wide range of ligaments sizes and densities. Furthermore interesting mechanical properties have been reported such as a size dependent Young’s modulus and strength.Although large progress is made in understanding the dealloying process and corresponding formation of pores, little is known about the evolving microstructure of the Ag-Au alloy and the final Au matrix. In this work we present a comprehensive x-ray diffraction study of nanoporous gold, including in-situ x-ray diffraction during synthesis and ex-situ Laue micro-diffraction. We find that during synthesis the ligament sizes continuously increase with time, even when the dissolving process has finished. Post dealloying microdiffraction experiments indicate that the crystal structure of the grains is very well preserved. No indication for the formation of additional boundaries could be found. Finally we find that the use of focused ion beam milling to prepare lamella for electron microscopy can have profound influences on the observed microstructure and diffraction data.
5:30 PM - SS2.10
In Situ Studies of Equilibrium and Non-Equilibrium Dynamics Over Extended Length and Time Scales Using Ultrasmall-Angle X-ray Scattering / X-ray Photon Correlation Spectroscopy.
Andrew Allen 1 , Fan Zhang 1 , Lyle Levine 2 , Jan Ilavsky 3 , Alec Sandy 3 , Gabrielle Long 3
1 Ceramics Division, NIST, Gaithersburg, Maryland, United States, 2 Metallurgy Division, NIST, Pasadena, California, United States, 3 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractScattering and imaging techniques have enjoyed great success in static microstructural studies over the full nanometer-to-micrometer scale range in advanced materials ranging from nanoparticle suspensions to composites and alloys. Yet the dynamics of these materials, especially their response to abrupt changes in the sample environment, largely remains elusive. X-ray photon correlation spectroscopy (XPCS) has emerged as a measurement technique that offers unprecedented sensitivity to the dynamics of structural changes in materials. However, existing XPCS facilities are limited to microstructure length scales smaller than about 50 nanometers, thus eliminating large classes of materials that are of major technological importance. Recently, we have developed combined ultrasmall-angle X-ray scattering / X-ray photon correlation spectroscopy (USAXS/XPCS) studies to probe the slow equilibrium and non-equilibrium dynamics of optically opaque materials with prominent scattering features in the range 100 nm to several micrometers, i.e., between the ranges of dynamical light scattering and conventional XPCS. Two examples illustrate the in situ applicability and capability of USAXS-XPCS. The first explores the equilibrium dynamics of colloidal dispersions at various volume concentrations as a function of temperature. The second example concerns the nonequilibrium dynamics of a polymer nanocomposite, for which in situ USAXS/XPCS reveals incipient dynamical changes not observable by other techniques.
5:45 PM - SS2.11
In-Plane Correlations in a Polymer-Supported Lipid Membrane Measured by Off-Specular Neutron Scattering.
Mikhail Zhernenkov 1 , Michael Jablin 1 , Boris Toperverg 2 , Manish Dubey 1 , Hillary Smith 1 , Ajay Vidyasagar 3 , Ryan Toomey 3 , Alan Hurd 1 , Jaroslaw Jaroslaw Majewski 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Department of Physics, Ruhr-University Bochum, Bochum Germany, 3 Department of Chemical and Biomedical Engineering, University of South Florida, Tampa, Florida, United States
Show AbstractOff-specular neutron scattering is often neglected even though it is frequently collected and can be used to elucidate in-plane morphology of biologically relevant systems in situ. Analysis of the off-specular neutron scattering from a polymer-supported single lipid bilayer in a liquid environment is used to quantify in-plane height-height correlations of interfacial fluctuations of the system. As temperature is decreased from 37 to 25 °C, the thermoresponsive polymer swells. Consequently, the polymer-supported lipid membrane deviates from its nearly planar prior structure. Modifications of the membrane’s configuration are manifested in pronounced changes in the neutron scattering. Applying the Distorted Wave Born Approximation to analyze the off-specular scattering, a correlation length characteristic of capillary waves was determined to be 30 μm at 37 °C, while reducing to 11 μm at 25 °C. The reduction in length with decreased temperature unambiguously confirms the expected role of the swelling polymer, driving the membrane to a nearly free state with reduced surface tension. A second correlation length related to the membrane bending rigidity is determined to be ~1 μm independent of the state of the supporting polymer
Symposium Organizers
John Cumings University of Maryland
Dillon Fong Argonne National Laboratory
Jianyu Huang Sandia National Laboratories
Stuart Lindsay Arizona State University
Guangwen Zhou State University of New York, Binghamton
SS5: Poster Session: Advanced Imaging and Scattering Techniques for In-Situ Studies
Session Chairs
Tuesday PM, November 30, 2010
Exhibition Hall D (Hynes)
SS3/UU3: Joint Session: Fast Electron Microscopy & Scattering
Session Chairs
Tuesday PM, November 30, 2010
Room 309 (Hynes)
9:30 AM - **SS3.1/UU3.1
The Dynamic Transmission Electron Microscope (DTEM): In-situ Microscopy with Nanometer and Nanosecond Resolution.
Nigel Browning 1 2 3 , Marta Bonds 1 , Geoffrey Campbell 3 , James Evans 2 1 , Katherine Junjohann 1 , Joseph McKeown 3 , Thomas LaGrange 3 , Bryan Reed 3 , Melissa Santala 3
1 Chemical Engineering and Materials Science, University of California at Davis, Davis, California, United States, 2 Molecular and Cellular Biology, University of California at Davis, Davis, California, United States, 3 Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractThe dynamic transmission electron microscope (DTEM) has been developed to obtain both high spatial (~1nm or better) and high temporal (~1microsecond or faster) resolution. The high temporal resolution is achieved by using a short pulse laser to create the pulse of electrons through photo-emission. This pulse of electrons is propagated down the microscope column in the same way as in a conventional high-resolution TEM. The only difference is that the spatial resolution is limited by the electron-electron interactions in the pulse (a typical 10ns pulse contains ~109 electrons). To synchronize this pulse of electrons with a particular dynamic event, a second laser is used to “drive” the sample a defined time interval prior to the arrival of the laser pulse. The important aspect of the DTEM is that one pulse of electrons is used to form the whole image, allowing irreversible transitions and cumulative phenomena such as nucleation and growth, to be studied directly in the microscope. The use of the drive laser for fast heating of the specimen presents differences and several advantages over conventional resistive heating in-situ TEM – such as the ability to drive the sample into non-equilibrium states. So far, the drive laser has been used for in-situ processing of nanoscale materials, rapid and high temperature phase transformations, and controlled thermal activation of materials. In this presentation, a summary of the development of the DTEM and in particular, in-situ stages for both the existing DTEM at LLNL and a new DTEM at UC-Davis will be described. Particular attention will be paid to the potential for gas stages to study catalytic processes and liquid stages to study biological specimens in their live hydrated states. The potential improvements in spatial and temporal resolution that can be expected through the implementation of upgrades to the lasers, electron optics and detectors used in the new DTEM will also be discussed.Development of the DTEM at LLNL was performed under the auspices of the U.S. Department of Energy by 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 DE-AC52-07NA27344. Development of in-situ stages for the DTEM at UC-Davis was supported by DOE NNSA-SSAA grant number DE-FG52-06NA26213 and NIH grant number RR025032-01.
10:00 AM - SS3.2/UU3.2
Dynamic Transmission Electron Microscope Investigations of Chalcogenide-based Phase Change Materials.
Melissa Santala 1 , Bryan Reed 1 , Stefan Meister 2 , Thomas LaGrange 1 , Geoffrey Campbell 1 , Nigel Browning 1 3 4
1 Condensed Matter & Materials Division, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Materials Science & Engineering, Stanford University, Stanford, California, United States, 3 Department of Chemical Engineering and Materials Science, University of California, Davis, California, United States, 4 Department of Molecular & Cellular Biology, University of California, Daivs, California, United States
Show AbstractGe2Sb2Te5 is a chalcogenide-based phase-change material that is technologically significant because of its wide use in optical recording media and its potential for use in non-volatile electronic memory [1]. For either application, rapid switching between the amorphous and crystalline phases is necessary for recording data, and understanding the changes to the crystal structure and microstructure during phase transitions at very short time scales is of scientific and technological interest. The time for laser-induced crystallization (~100ns) and amorphization (~10ns) [2] are difficult to probe with conventional imaging and scattering instrumentation, but are on the scale ideally probed with the dynamic transmission electron microscope (DTEM).The DTEM is a unique, highly-modified electron microscope capable of nanosecond-scale time-resolved imaging and diffraction. It is a powerful tool for the study of dynamic events, such as phase transformations, as demonstrated in metals and semiconductors [3] and is applied here to the study of Ge2Sb2Te5. Phase transformations in continuous and micro-patterned thin films of Ge2Sb2Te5 were induced with a laser in the DTEM. The amorphous-crystalline and melting-solidification transitions were observed and the kinetics of these processes were revealed by time-resolved TEM imaging and electron diffraction on nanosecond time scales. Using an unconventional specimen geometry, repeated switching between the amorphous and crystalline phases has been achieved in the DTEM enabling in situ study of structural changes after repeated switching, which is relevant to device performance. Since the laser absorption and heat transport are sensitive to the specimen geometry, finite element analysis was used to model the laser absorption and heat diffusion in the specimen geometries used. The experimental observations are compared to the modeling results.This work performed under the auspices of the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.References[1]M. Wuttig and C. Steimer, Appl. Phys. A – Mater. 87 (2007) 411-7.[2]V. Wiedenhof, I. Friedrich, S.Ziegler, and M. Wuttig, J. Appl. Phys. 89 (2001) 3168-76. [3]T. LaGrange et al., Ultramicroscopy 108 (2008) 1441-9.
10:15 AM - SS3.3/UU3.3
Imaging of Solid Growth into a Superheated Liquid during Rapid Solidification of Metal Thin Films by in situ Transmission Electron Microscopy.
Andreas Kulovits 1 , Jorg Wiezorek 1 , Thomas LaGrange 2 , Bryan Reed 2 , Geoffrey Campbell 2
1 Mechanical Engineering and Materials Science, Swanson School of Engineering, University of Pittsburgh, Pittsburgh , Pennsylvania, United States, 2 Condensed Matter and Materials Division, Physical and Life Science Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractNanocrystalline metal thin films were molten inside an electron microscope with an excimer laser that illuminates a disk shaped area. With time delays as short as 12nanoseconds ns, an electron pulse illuminates the molten area. This unprecedent nanosecond time resolution in combination with the nanometer spatial resolution allowed us to investigate details of the solidification process. Complete melting in the illuminated area was established by electron diffraction. In imaging mode the character of the advancing liquid solid interface was investigated. The liquid solid interface is planar throughout the entire solidification process. In this process solidification is initiated from the interface between the nanocrystalline solid metal film and the liquid metal once the temperature of the liquid at the interface drops below the melting point. Parallel to the growth direction elongated grains grow from the original liquid solid interface. We used transmission electron microscopy to ex situ analyze the microstructure and defect content of the solidified films. Special attention was paid to the region at the edge of the melt pool to investigate the process of occlusion. We used automated acquisition and indexing of precession diffraction patterns in the TEM (ASTAR/DigiSTAR from NanoMEGAS) to analyze the growth direction of the morphologically elongated grains. No preferential growth orientation was observed. Our observations of a planar liquid solid interface and the lack of a preferential growth direction indicate that the this rapid solidification process despite being orders of magnitude faster than conventional solidification can be described by conventional solidification theory. The Work was performed under the auspices of the U.S. Department of Energy by the 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.
10:30 AM - SS3.4/UU3.4
In-situ TEM Observation of Formation-Retraction-Fracture Experiment of Liquid-Like Silicon Nanocontact.
Tadashi Ishida 1 , Kuniyuki Kakushima 2 , Hiroyuki Fujita 1
1 Center for International Research on Micro Mechatronics, Institute of Industrial Science, University of Tokyo, Tokyo Japan, 2 , Tokyo Institute of Technology, Kanagawa Japan
Show AbstractA liquid-like silicon nanocontact was formed when silicon opposing tips were brought into contact with high bias voltage. In-situ observation by a transmission electron microscope (TEM) during the retraction process showed that the nanocontact easily thinned with nano-scaled step propagation along the surface from the contact to the tip. Repeating this thinning process, the nanocontact was finally fractured at 30 nm in diameter. Silicon is the most common material for micro/nano devices. It is important to measure the electronic and mechanical properties of silicon at the nano scale because the properties are expected to be very different in such a small scale from ordinary scales. Thus, we have studied the electronic and mechanical properties of a silicon nanowire and a nanocontact for the further development of nano devices. The silicon crystalline nanocontact showed twice higher strength than micrometer-sized crystalline silicon structures. However, we found a much softer silicon nanocontact when high bias voltages were applied between tips. In our experimental system, MEMS opposing tips with micro electrostatic actuators with one degree-of-freedom were operated inside an ultra-high-vacuum TEM chamber. MEMS structure with micro electrostatic actuators and silicon opposing tips were fabricated with bulk micromachining and focused ion beam, respectively. A driving voltage for the actuators and a bias voltage for an electrical measurement between tips were applied with feed-throughs. Electron beam for TEM observation was 1.6x103 A/cm2 without an appreciable heating. Using this combination between MEMS and TEM, a deformation of a nanostructure between tips can be in-situ visualized with TEM. Silicon tips were brought into contact with 1 V in bias voltage. The bias voltage increased at 1 V/s and then electric current suddenly jumped up from a few micro amperes to 100 micro amperes around 13 volts. A silicon nanocontact of 98 nm in diameter was formed between tips. Then, we set the bias voltage at 1 V again to decrease the influence of electrical voltage and current between tips; the current was 30 nA. The silicon nanocontact without any lattice fringes was retracted at 2.0 nm/s. The diameter of the necking drastically decreased from 98 nm to 30 nm at the speed of 1.8 nm/s. During this deformation, steps of 4.4 nm in height propagated from the neck to the tip at 7.0 nm/s. The nanocontact was fractured without any retraction when the diameter was 30 nm. The corner of the breakage part was rounded like a liquid droplet to 12 nm in radius of curvature in less than 30 ms. The deformation was completely different from the reported silicon nanocontact. According to the literature, silicon nanocontacts showed both elastic and plastic deformation, and the corner rounding at the breakage point. These results suggest that the properties of nanostructures consisted of the same material can be easily affected by the formation methods.
10:45 AM - SS3.5/UU3.5
Sintering of Silver Nanoparticles using In-situ TEM Heating.
Michael Asoro 1 , Desiderio Kovar 1 , Paulo Ferreira 1
1 Materials Science and Engineering, University of Texas at Austin, Austin, Texas, United States
Show AbstractNanoparticles possess a wide range of properties used in many applications such as patterned conductors in microelectronics and catalysts in chemical reactions. During processing or usage, nanoparticles have a strong tendency to agglomerate and sinter over short time scales, which can be either beneficial or detrimental, depending on the application. In the present work, a JEOL 2010F transmission electron microscope (TEM), equipped with a novel Protochips AduroTM heating stage, is used to perform in-situ heating experiments. We observe in real time, the sintering of silver nanoparticles as a function of particle size and temperature. These experiments provide real-time dynamic information for a direct investigation of the evolution of sintering, which post-mortem TEM observations are not capable of conveying. The particle radius, neck radius, and dihedral angle can be measured from the TEM images, using Gatan Digital Micrograph software. These values are then used to calculate fundamental material variables, such as surface and grain boundary diffusion coefficients relevant to the understanding of sintering in nanoparticles.
11:30 AM - **SS3.6/UU3.6
Direct Observation of Structural Dynamics with Ultrafast Electron Diffraction.
Nuh Gedik 1
1 Physics, MIT, Cambridge, Massachusetts, United States
Show AbstractThe interaction between electronic, spin and structural degrees of freedoms leads to fascinating properties in strongly correlated electron materials. Although direct probing of electronic excitations can be achieved with ultrashort laser pulses, only indirect information can be obtained about structural excitations using optical probes. I will report direct measurements of structural dynamics with atomic scale spatial resolution by using ultrafast electron diffraction (UED). In UED, a femtosecond laser pulse is split into two, the first part is used to induce structural change and the second part is used to generate ultrafast high energy electron packets via photoelectric effect. Recording the diffraction pattern of these electron packets at different times after the photo-excitation of the sample provides a movie of the laser induced structural change with sub-picosecond temporal and sub-Angstrom spatial resolution. I will discuss recent experiments where we used UED to observe lattice dynamics in correlated electron materials in response to photo-excitation of the charge carriers.
12:00 PM - SS3.7/UU3.7
Time-resolved Imaging of Catalyst Nanoparticles in the Dynamic Transmission Electron Microscope.
Joseph McKeown 1 , Daniel Masiel 2 , Shareghe Mehraeen 2 , Thomas LaGrange 1 , Bryan Reed 1 , Geoffrey Campbell 1 , James Evans 3 , Nigel Browning 1 2 3
1 Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Department of Chemical Engineering and Materials Science, University of California, Davis, California, United States, 3 Department of Molecular and Cell Biology, University of California, Davis, California, United States
Show AbstractThe dynamic transmission electron microscope (DTEM) has the potential to allow direct in-situ imaging of nanoparticle catalysis at both high spatial and temporal resolution. An in-situ gas stage that was designed and built for the DTEM at LLNL facilitates studies of nanoscale catalysis in environments that otherwise cannot be obtained in the vacuum of the electron microscope. While the spatial resolution of the DTEM has thus far been limited by low contrast and signal-to-noise ratios, making experiments involving dispersed nanoparticles at optimal resolutions difficult, the use of an annular objective-lens aperture has been shown [1] to improve the loss of resolution associated with the imaging conditions in the DTEM.Dynamic measurements of chemical processes such as oxidation/reduction reactions will be conducted in the DTEM to monitor catalyst morphologies and reaction sites between nanoparticles and substrates. The DTEM drive laser can easily generate temperatures required for the reactions to be studied, while the in-situ stage provides the desired gas atmosphere. For example, the infiltration of nanoparticles such as Ni, Co3O4, and CeO2 into porous YSZ electrode skeletons has been shown to significantly improve performance in reduced-temperature thin-film solid oxide fuel cells (SOFCs) [2-4]. Mechanisms for this enhancement can be investigated at the nanometer length scale with nanosecond time resolution in the DTEM. Complementary analysis using high-resolution imaging and spectroscopy will be conducted prior to and after dynamic measurements. The results of initial catalytic experiments will be presented, and all aspects of the design and implementation of the in-situ stage in the DTEM will be discussed [5].References[1]Masiel, DJ, et al. ChemPhysChem 11 2010 1. [2]Yamahara, K, et al. Solid State Ionics 176 2005 275.[3]Sholklapper, TZ, et al. Nano Lett. 7 2007 2136.[4]Imanishi, N, et al. Fuel Cells 9 2009 215.[5]Development of the DTEM at LLNL was 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. Development of in-situ stages for the DTEM at UC Davis was supported by DOE NNSA-SSAA grant number DE-FG52-06NA26213 and NIH grant number RR025032-01.
12:15 PM - SS3.8/UU3.8
The Solid-liquid Interface and Transformation Behavior in Sub-micron Al Alloy Particles Analyzed by in situ Transmission Electron Microscopy (TEM).
Prakash Palanisamy 1 , James Howe 1
1 Department of Materials Science and Engg., University of Virginia, Charlottesville, Virginia, United States
Show Abstract Understanding the solid-liquid interface and its transformation behavior is critical for crystal growth technology. This presentation reports on two in situ heating and cooling experiments conducted in the TEM to understand the solid-liquid transformation. The first study tries to understand elemental partitioning at the solid-liquid interface in Al-Si-Cu-Mg alloy powder particles. The particles were heated in a JEOL 2000FX TEM fitted with a high-angle energy-dispersive X-ray (EDX) detector. At 585 deg.C, the alloy particles contain two phases, solid Si in contact with liquid Al, with Cu and Mg in solution in the liquid Al. X-ray spectra were acquired at three different temperatures (585 deg.C and then on cooling to 565 deg.C and 470 deg.C) in the solid Si, liquid Al-rich phase, and at the solid Si-liquid Al interface, using a 25 nm diameter electron probe. It was found that Cu segregates to the solid Si-liquid Al interface when the temperature is decreased from 585 deg.C to 470 deg.C. The segregation of Cu is heterogeneous and appears to participate in nucleating a Cu-rich phase (most likely Al2Cu(Theta) equilibrium phase) at a high-index Si facet. The Cu concentration measured at the solid-liquid interface and in the Al-rich liquid phase at 565 deg.C and 470 deg.C at regular time intervals over 1.5 hr remains practically constant, indicating that the heterogeneous segregation of Cu to the solid Si-liquid Al interface thermodynamically and not kinetically driven. The second set of studies focuses on understanding the solid-liquid transformation and supercooling behavior in sub-micron pure Al particles. The particles were heated above the melting temperature (660 deg.C) in a JEOL 2010F TEM containing an electron energy-loss spectrometer (EELS), which provides information about low-energy plasmon losses through valence EELS (VEELS). It was found that the plasmon energy, which is a measure of free-electron density in the material, decreases non-linearly with increasing temperature. The non-linear change can be explained based on phonon anharmonicity. A sharp discontinuity in the plasmon energy corresponding to the melting temperature is characteristic of the first-order phase transformation. The free-electron density change measured at the melting temperature was 6%, consistent with the theoretical volume change calculated for Al. This study shows that liquid Al particles can be undercooled by 100 deg.C prior to their nucleation, in reasonable agreement with earlier supercooling studies in micron-sized Al particles. The present study also reveals that the plasmon energy change during supercooling of liquid Al is not a direct extrapolation from the liquid state. This research was supported by the National Science Foundation under grant DMR-0554792.
12:30 PM - SS3.9/UU3.9
Atomic–Scale Imaging of Cation Intermixing in Ordered LiFePO4 Nanocrystals at High Temperature.
Sung-Yoon Chung 1 2
1 Materials Sci. & Eng., Inha University, Incheon Korea (the Republic of), 2 , Nalphates LLC, Wilmington, Delaware, United States
Show AbstractOlivine-type lithium metal phosphates have attracted a great deal of attention over the last decade as an alternative cathode material in Li-ion batteries. In particular, to improve the electrochemical performance of LiFePO4, numerous investigations have been made in addition to many studies of the intrinsic ionic and electronic properties and the thermodynamic phase equilibria. The achievement of remarkable high-rate capability and outstanding thermochemical stability in LiFePO4 during the intercalation reaction (S.-Y. Chung et al., Nature Mater., 1, 123 (2002)) have resulted in the recent success of the application as a safe power source adopted for power tools and potentially for hybrid electric vehicles as well (Nature, 444, 16 (2006)).Among a variety of factors that govern the electrochemical cycling behavior in this class of compounds, control of their cation partitioning and the resultant degree of ordering among the equivalent interstitials has been a crucial issue due to Li mobility in the lattice. In particular, if the Li diffusion in LiMPO4-type ordered olivine phosphates is considerably dependent on the crystallographic orientation, precise probing of local cation distribution within individual crystals during synthesis is of great significance for better understanding of the correlation between the cation partitioning and resulting Li intercalation reaction kinetics (S.-Y. Chung et al., Angew. Chem. Int. Ed., 48, 543 (2009)).Using in situ high-resolution high-temperature electron microscopy and crystallographic image processing, as shown in the previous study (S.-Y. Chung et al., Nature Phys., 5, 68 (2009)), we directly demonstrate in real time that significantly different local cation intermixing can be kinetically induced by fast crystal growth during crystallization in olivine-type lithium metal phosphates. The presence of lattice distortion and misfit strain resulting from the different cation configurations is also confirmed quantitatively. The findings in this study show that control of nucleation and subsequent growth during synthesis is of importance to attain a high degree of cation ordering in olivine phosphates.
SS4/UU4: Joint Session: TEM and SPM Studies in New Environments
Session Chairs
Guus Rijnders
Frances Ross
Tuesday PM, November 30, 2010
Room 309 (Hynes)
2:30 PM - **SS4.1/UU4.1
Liquid Cell Transmission Electron Microscopy for in situ Studies of Crystal Growth.
Frances Ross 1
1 , IBM T.J. Watson Research Center, Yorktown Heights, New York, United States
Show AbstractThere is a growing interest in liquid cell transmission electron microscopy that has led to unique results in areas such as self-assembly of colloid particles, biomineralization, and electrochemical nucleation and growth. The spatial and temporal resolution offered by liquid cell microscopy provides quantitative information on the physics of crystal growth. However, interpretation is complicated by the effects of the electron beam, the finite liquid thickness and proximity of the cell windows, and chemical interactions with the materials that make up the cell. In this presentation we will describe electrochemical growth of copper and zinc in the context of these effects, comparing the results of liquid cell microscopy with ex situ results and simulations. During copper growth in the presence of additives, we show how information such as surface diffusion parameters and concentration gradients in the liquid phase can be obtained, but also discuss how the electron beam modifies copper nucleation in chloride solutions and polymerizes organic species. The finite electrolyte thickness constrains dendrite growth and affects diffusion fields, and for zinc deposited from KOH, chemical interactions with the cell materials alter nucleation sites. Quantitative analysis thus requires inclusion of several effects, but can lead in interesting directions such as the electron-beam control of nucleation to produce patterned nanostructures.
3:00 PM - SS4.2/UU4.2
Watching Real-time Assembly of Nanopcrystals Using in-situ Liquid Phase TEM.
Jungwon Park 1 2 , Haimei Zheng 2 , Grauer David 1 , A. Paul Alivisatos 1 2
1 Chemistry, UC Berkeley, Berkeley, California, United States, 2 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractAs-synthesized nanoparticles (NPs) serve as functional materials in devices such as transistors, thermoelectrics, photodetectors, LEDs, and solar cells. Fabrication of these devices often include controlled, macroscopic arrays of NPs as the functional component. Physical properties such as size, shape, composition of individual particles as well as the optoelectrical coupling and communication between the NPs in these arrays are all critical factors for overall device performance. If we consider a NP device as an ensemble, packing density, interparticle medium, and orientation must also be considered and controlled. NPs can be assembled together either in an amorphous phase or in ordered crystalline structures. Controlled arrays of NPs can be tuned by manipulating a combination of particle-particle and particle-substrate interactions, particle solubility, and solvent evaporation rate. Many types of assemblies have been reported with single and multi-component building blocks of charged, magnetic, and semiconductor NPs. Most of these assemblies were mediated by controlled drying of volatile solvents. However, our understanding of NP dynamics during superlattice formation is still far behind empirical procedures. Here, we show the real time observation of cubic Pt nanoparticle superlattice formation via liquid phase in-situ TEM experiment. Recently, a TEM cell with the capability of observing a thin liquid sample has been developed. This technique enabled us to study real time NP dynamics occurring in liquid phase inside a conventional TEM. Pt cubic nanoparicles were prepared in colloidal phase and dispersed in the mixture of pentadecane and oleylamine. We also simulated the evaporation mediated liquid-substrate-air interface during assembly by electron beam. Solvent in a tightly sealed liquid cell can be heated and stilmulated by heat and momentum transfer from the electron beam when we focus the electron beam onto local spots within the cell window. From the real time observations of individual particle motion, we could track the formation of NP superlattices from an initial random distribution. Interestingly, superlattices evolved through two distinct phases: first, a contraction of nearest neighbor particles via capillary forces and the subsequent relaxation of packed particles into an ordered superlattice by particle-particle interaction. In addition, individual particles undergo lateral diffusion and rotation to fill in lattice defects during superlattice formation. We also studied in-situ assembly formation of nanoparticles with different compositions and aspect ratios. This study provides fundamental mechanistic insights into the formation of NP superlattices. These results can be combined with existing empirical knowledge to provide a platform for the rational, controlled design of NP superlattices.
3:15 PM - SS4.3/UU4.3
Application of in-situ Electron Microscopy in Nanoscience and Energy Research.
Jianyu Huang 1 , Li Zhong 2 , Chongmin Wang 3 , Liang Qi 4 , J. Sullivan 1 , Ju Li 4 , Wu Xu 3 , Hongyou Fan 1 , N. Hudak 1 , Liqiang Zhang 2 , A. Subramanian 1 , S. Mao 2
1 , Sandia National Lab., Albuquerque, New Mexico, United States, 2 , University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 3 , Pacific Northwest National Laboratory, Richland, Washington, United States, 4 , University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractBy integrating an atomically sharp scanning tunneling microscopy (STM) probe into a transmission electron microscope (TEM), the atomic structure and physical properties of individual nanostructures can be directly probed in real time at the atomic length-scale. Such studies have revealed a number of unexpected phenomena that only present themselves at the nano-scale. We discovered superplastic elongation of carbon nanotubes, salt nanowires, and nanosized metallic glass. A nanobattery comprised of an individual nanowire electrode was constructed inside a TEM, and the charge and discharge process was revealed in real time, pushing the forefront of knowledge in the highly technologically relevant area of Li-ion batteries.
3:30 PM - SS4.4/UU4.4
In situ Liquid Cell Transmission Electron Microscopy of Dendrite Formation at Battery Interfaces.
Prineha Narang 1 2 , Michael Henry 3 , Arthur Ellis 2 , Xiaoyan Shao 2 , Mark Reuter 2 , Yury Gogotsi 1 , Dan Steingart 3 , Frances Ross 2
1 Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania, United States, 2 , IBM T.J. Watson Research Center, Yorktown Heights, New York, United States, 3 Dept. of Chemical Engineering, City College of New York, New York, New York, United States
Show AbstractThe relationship between the morphology of electrodeposited materials and the conditions under which they are formed is a key issue for the development of improved batteries for energy storage and delivery. Zinc is a particularly important example, as it is an attractive anode material for low cost, cyclable batteries, yet the large body of literature on the microstructure of electrodeposited zinc is inconclusive. Our objective is to establish a mechanism based understanding of dendrite formation and prevention at battery interfaces that eliminates or reduces the need for barriers. Here we show that liquid cell TEM, with its unique ability to provide simultaneous temporally and spatially resolved information, can yield insights into the physics of electrochemical zinc growth. This has been done by directly imaging the morphological evolution of the anode under electrochemical conditions that mimic charge and discharge cycles. We discuss the technique for real time studies of batteries in the TEM in addition to which we show effects of the electron beam on electrolytes commonly used in batteries, impact of the electrochemical cell geometry on simulating battery conditions in situ and correlation with optical electrochemical cell results. Finally we present preliminary analysis of variation in zinc morphologies grown in situ and current- voltage conditions associated with them.
3:45 PM - SS4.5/UU4.5
An In-situ Ex-environmental TEM Study on the Initiation of Pitting Corrosion of Austenitic Stainless Steels in Salt Water.
Xiuliang Ma 1
1 Shenyang National Laboratory for Materials Sciences, Institute of Metal Research, Shenyang China
Show AbstractStainless steels are widely used in modern life for their superior corrosion resistance. However, stainless steels are actually not “stainless”; in the presence of aggressive anionic species they are susceptible to the localized pitting corrosion that is one of the major causes of materials’ failure and hence leads to a huge loss to our society. The pitting event is generally believed to result from the local dissolution in manganese sulphide (MnS) inclusions which are more or less ubiquitous in stainless steels. Nevertheless, the microstructure information on the local site where MnS dissolution preferentially occurs is lacking, which makes pitting corrosion remain the big headache for numerous engineering materials. We have applied in-situ ex-environment transmission electron microscopy to identify the initial site, at an atomic scale, of MnS dissolution which is critically important but unclear so far for understanding the origin of pitting corrosion in stainless steels. We find that a “single-grained” MnS inclusion in the steel is compositionally and structurally inhomogeneous. Fine octahedral precipitates of spinel MnCr2O4 with dimensions of several tens of nanometers, are dispersedly distributed in the MnS inclusions. In-situ TEM studies indicate that the MnS initially dissolves at the MnCr2O4/MnS interface in the presence of salt water, and the dissolution gradually spreads outwards leaving a pit around the MnCr2O4 octahedron. However, the reactivity of these octahedra is various. First-principles calculations indicate that the dynamics of MnS dissolution is the function of the species of terminal ions enclosing the nano-octahedron catalyst. The MnCr2O4 nano-octahedron with metal terminations is more reactive in catalyzing the MnS dissolution than O-terminated ones. This work not only sets up a new basis for understanding the initiation of pitting corrosion, but also presents a novel example of how an inorganic nano-inclusion undermines its metallic matrix in an electrochemical manner which may occur in a wide range of engineering alloys and biomedical materials serving in wet environments.
4:30 PM - **SS4.6/UU4.6
In-situ Monitoring of Oxide Thin Film Growth.
Guus Rijnders 1
1 Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, Enschede Netherlands
Show AbstractComplex oxides have attracted great interest since they exhibit a rich spectrum of physical properties such as ferromagnetism, antiferromagnetism, colossal magnetoresistance, ferroelectricity, dielectricity, and superconductivity. Novel heteroepitaxial devices based on these complex oxides, like spin-polarized ferromagnetic tunnel junctions, superconducting devices and piezoelectric devices, have great potential and are currently under investigation in many groups.The nature of the above-mentioned physical properties in complex oxides is determined by very small characteristic length scales, comparable to the unit cell lattice parameters of complex oxide. Because of these small characteristic length scales, growth control on an atomic level as well as understanding of the different mechanisms affecting the growth mode is essential for the fabrication of epitaxial heterostructures. Two independent processes, i.e., nucleation and growth of islands, play an important role during vapor-phase epitaxial growth on an atomically flat surface. Here, nucleation causes the formation of surface steps and subsequent growth causes the lateral movement of these steps. Both processes are determined by kinetics, since they take place far from thermodynamic equilibrium. These kinetic processes affect the final surface morphology and are, therefore, extensively studied. I will demonstrate the applicability of high-pressure RHEED as well as Scanning Force Microscopy (SFM) to monitor to the growth of complex oxides during Pulsed Laser Deposition (PLD). Because of recent developments, SFM is nowadays also used to study dynamic processes, such as thin film growth and surface reaction mechanisms. We have realized a system, in which SFM can be performed during Pulsed Laser Deposition (PLD). Deposition and force microscopy are performed in one vacuum chamber and via a fast transfer (in the order of seconds) the surface of a sample can be scanned. In our system we take advantage of the pulsed deposition process, because microscopy measurements can be carried out between the pulses. This provides real-time morphology information on the microscopic scale during growth. The transfer mechanism allows switching between microscopy and deposition with a re-position accuracy of ±500 nm which gives new opportunities to study growth processes. Furthermore, it can provide information if RHEED is not possible, for example during amorphous and polycrystalline growth. In this contribution, I will highlight recent advances in oxide thin film growth as well as the latest equipment developments.
5:00 PM - SS4.7/UU4.7
In-situ Observations of Domain Wall Motion by STM-(S)TEM.
Hye Jung Chang 1 , S. Kalinin 1 , S. Yang 3 , S. Bhattacharya 2 , P. Wu 2 , L. Chen 2 , R. Ramesh 3 , S. Pennycook 1 , A. Borisevich 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 , Penn State University, University Park, Pennsylvania, United States, 2 , University of California, Berkeley, California, United States
Show AbstractIn situ application of bias in Scanning Probe Microscope (SPM) – (Scanning) Transmission Electron Microscope (STEM) offers unique advantages for observations of ferroelectric domain dynamics. The domain structure can be monitored as the bias is applied. Observations through the thickness of the film can be made, making it possible to distinguish events such as nucleation occurring at the surface, at the film-electrode interface and in the bulk of the film. Here we use this method to study domain dynamics in cross sections of thin BiFeO3 (BFO) films grown on SrTiO3 substrate with SrRuO3 (SRO) bottom electrode. Bias is applied locally using the electrochemically prepared W tip.Local bias as low as 3.3 V applied to the cross section sample produces almost instantaneous and persistent changes in domain structure. The structure undergoes complex changes, including domain wall motion, domain growth and coalescence and nucleation of new domains at the film surface and film-electrode interface. The 71° domain walls present in the film can also undergo 90° rotation if the bias sign is switched to opposite. Defects at the SRO-BFO interface can serve as domain nucleation sites. Domain wall pinning by defects such as dislocations, resulting in curved domain walls, is also observed. This research is sponsored by the Division of Materials Sciences and Engineering, Office of BES of the U.S. DOE, and by appointment (H.J.C.) to the ORNL Postdoctoral Research Program administered jointly by ORNL and ORISE. Instrument access is supported by ORNL’s SHaRE User Facility, which is sponsored by the Scientific User Facilities Division, Office of BES, the U.S. DOE.
5:15 PM - SS4.8/UU4.8
Observation Of Real-time Thin Film Evolution Using Microcantilever Sensors.
Alan Schilowitz 1 , Dalia Yablon 1
1 Corporate Strategic Research, ExxonMobil Research and Engineering Company, Annandale, New Jersey, United States
Show AbstractAdsorption and desorption kinetics of thin film formation on metal surfaces has been directly monitored in real-time by optically measuring the deflection of activated atomic force microscope cantilevers (microcantilevers). Microcantilever deflection is caused by stress generated during the formation of an adsorbate layer on one side of the microcantilever. In this work, rapid adsorption of carboxylic acid in hydrocarbon solution onto a gold surface was directly observed as a compressive stress developed on the microcantilever substrate. Upon exposure to alkyl thiol the desorption of acid followed by its displacement by alkyl thiol was continuously monitored in real-time. Kinetic rate constants and thermodynamic properties of the adsorption and desorption processes are also discussed. In addition, ex-situ spectroscopic analysis conducted at discrete times during the adsorption process has been used to determine the state of the adsorbed layer as the microcantilever deflects. This analysis suggests that while some film organization and intermolecular interactions are required before measurable surface stress can be detected, significant surface stress is generated before complete organization of the film occurs.
5:30 PM - SS4.9/UU4.9
In Situ SEM Compression Studies of Vertically and Radially Aligned CNT Arrays.
Qiuhong Zhang 1 2 , Robert Wheeler 3 , Matthew Maschmann 1 4 , Liangti Qu 2 , Liming Dai 5 , Jeff Baur 1
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, United States, 2 , University of Dayton Research Institute, Dayton, Ohio, United States, 3 , UES Inc., Dayton, Ohio, United States, 4 , Universal Technology Corporation, Beavercreek, Ohio, United States, 5 Chemcial Engineering, Case Western University, Cleveland, Ohio, United States
Show AbstractGrowth of carbon nanotubes (CNTs) on a rigid substrate offers a promising approach to tailor mechanical, electrical and thermal interfacial properties. However, there is still a need to understand the influence of structural order and response of CNT arrays in order to fully tailor interfacial properties. The small dimensions of CNTs and diversity of potential morphologies of individual elements present significant challenges for experimental study and understanding of their ensemble properties. Early studies of the mechanical properties of individual CNTs focused on theoretical analyses and numerical simulations. More recent studies have focused on vertically aligned CNT (VACNT) arrays on planar surfaces. Experimental evaluation of the mechanical properties of radially aligned carbon nanotube (RACNT) arrays grown on small diameter fiber substrates have been investigated to a lesser extent. A major focal point of recent VACNT array mechanical analysis has been the measurement of mechanical modulus and yield point. The mechanical behavior of CNT arrays beyond yielding have been sparsely reported. Specifically lacking is in situ observations of VACNT array mechanical behavior and exploration of the initiation and evolution of buckling throughout the length of the VACNT arrays while under load.In this study, in situ SEM analysis is utilized to investigate the mechanical response of VACNT and RACNT arrays under uniaxial compressive loading. Simultaneous SEM imaging and force-displacement data collection facilitates detailed evaluation of the elastic and plastic response during compression. The following observations were made: 1) RACNT/CF and VACNT/Si exhibit similar compressive mechanical behavior but different strain recovery capability; 2) the deformation may follow either beam buckling or collective bending behavior depending on array morphology; 3) CNT fracture was not observed even at very high compressive strains; 4) hysteresis is consistently observed in the loading and unloading force-displacement curves.
5:45 PM - SS4.10/UU4.10
Meta-stable Catalyst Phases and Interfacial Dynamics During Ge Nanowire Growth.
Stephan Hofmann 1 , Andrew Gamalski 1 , Caterina Ducati 2 , Renu Sharma 3 , Jerry Tersoff 4
1 Engineering, University of Cambridge, Cambridge United Kingdom, 2 Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom, 3 , National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 4 , T.J. Watson Research Center, Yorktown Heights, New York, United States
Show AbstractThe physical and chemical state of the catalyst is of key importance to nanowire growth kinetics, orientation and interface sharpness in hetero-structures, since it determines how quickly the chemical potential of the growth species can be raised to overcome nucleation barriers for nanowire and interfacial ledge formation [1]. We present lattice-resolved, video-rate environmental transmission electron microscopy that shows the formation of a liquid Au-Ge layer on sub-30 nm Au catalyst crystals, and the transition of this two-phase Au-Ge/Au coexistence to a completely liquid Au-Ge droplet during isothermal digermane exposure at temperatures far below the bulk Au-Ge eutectic temperature [2]. Upon Ge crystal nucleation and subsequent Ge nanowire growth, the catalyst either re-crystallizes or remains liquid, apparently stabilised by the Ge supersaturation. Kinetic and thermodynamic modeling gives insight into the importance of surface energies and catalyst-interface dynamics to nanowire growth and geometry.[1] Hofmann et al, Nature Materials 7, 372 (2008) [2] Gamalski et al, Nano Letters, submitted (2010)
SS5: Poster Session: Advanced Imaging and Scattering Techniques for In-Situ Studies
Session Chairs
Wednesday AM, December 01, 2010
Exhibition Hall D (Hynes)
9:00 PM - SS5.2
In situ Studies of Polymeric Nanostructures Enabled by Stimulated Emission Depletion Microscopy.
Chaitanya Ullal 1 , Roman Schmidt 1 , Marcel Lauterbach 1 , Alexander Egner 1 , Volker Westphal 1 , Stefan Hell 1
1 NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Goettingen, Niedersachsen, Germany
Show AbstractThe non-invasive imaging of polymeric nanostructures by far-field light microscopy has been precluded by its diffraction limited resolution. Nanometric resolution can be achieved by exploiting molecular transitions to switch fluorophores between two distinguishable states. We use Stimulated Emission Depletion (STED) Microscopy to obtain in situ images that would be challenging to obtain via currently established techniques. These include 3D images of micron thick nanostructured block copolymer films and dynamic images of convectively assembled colloidal particles at frame rates as high as 200 Hz. Such studies shorten the process of revealing structure-property relationships in these important classes of self-organizing materials.
9:00 PM - SS5.4
The In-situ Characterization and Structuring of Electrografted Polyphenylene Films on Silicon Surfaces. An AFM and XPS Study.
Achraf Ghorbal 1 , Federico Grisotto 1 , Julienne Charlier 1 , Serge Palacin 1 , Adina Morozan 1
1 Chemistry of Surfaces and Interfaces, CEA, Gif sur Yvette France
Show AbstractThe electrochemical grafting by reduction of aryldiazonium salts has recently received a great deal of attention from chemistry, surface and interface scientists. This growing interest was primarily motivated by the potential applications of organic thin films in recent developments of medicine, electronics, photovoltaics … However many studies or organic films prepared from diazonium salts suffer from a lack of characterization, regarding the film adhesion properties or film thickness which definitely govern the efficiency of the organic layers in technological applications. Moreover, the mechanism of the diazonium grafting is not yet well understood and especially on oxide surfaces. In this work, an atomic force microscope was used so as to structure by nano-friction films of polynitrophenylene electrografted on substrates of n-type silicon (100) with the native oxide on the top of the surface. AFM measurements of thin films thickness have been carried out in the electrolytic solution for different applied potentials during the electrografting. This investigation allows (i) to determine the relationship between the applied potential and the final thickness of electrografted polyphenylene films and (ii) to specify how the thin layers grow. XPS analysis confirmed the AFM observations on (i) the effective shaving of the grafted polymer chains under mechanical stress and (ii) the existence of a potential threshold for electrografting a polyphenylene film on silicon oxide surfaces. The presence of a residual film in the rubbed zone was attributed to stronger interactions between the first electrografted layer and the native oxide of silicon (through Si-C or/and Si-O-C bonds) than those insuring the cohesion of the multilayer (C-C and C-N bonds).
9:00 PM - SS5.5
Low Energy Ne Scattering Spectroscopy for Insulators, and Materials in the Electric/Magnetic Fields.
Kenji Umezawa 1
1 Physics, Osaka Pref. Univ., Sakai, Osaka, Japan
Show Abstract Surface structural analysis of insulators requires detailed knowledge of microscopic process for both fundamental and technological reasons. Generally speaking, measurements of insulator surfaces are difficult to study because of charging effects during electron or ion beam bombardment which are mostly employed in surface analysis methods. Low keV energy neutral beam scattering has been developed for determining the composition and structure of the surface layers of materials as a new tool. Low energy neutral beam scattering is a simple and extremely surface sensitive technique because of attributes of low keV energy. It shows short de Broglie wavelength (~ 10^ -14 m), which constrain them to classical behavior, and large collision cross sections. In this study, low energy Ne+ ion scattering spectroscopy has been modified for analysis of insulator surfaces. Besides, this technique is quite useful for the analysis of semiconductor as well as metal surfaces in the electric and magnetic fields. One or two atomic layers near the surface, as well as several underlying atomic layers, can be "seen". Spatial resolving power of this technique is less than 0.1 A, because of beam interactions in the energy range below 3 keV, suh as shadowing/blocking conditions. Low energy atom particle beams (2keV-20Ne0) were projected onto the sample surfaces to avoid charging effects. Measurements were carried out by the time-of-flight technique. The equipment of low energy Ne0 scattering spectroscopy system, as described below. It consists of an ultrahigh vacuum (UHV) chamber with the following components: (1) ion beam source (custom made), (2) MCP detector, (3) precision sample manipulator with stepping motors (custom made), (4) pre-amplifier (custom made), (5) amplifier (custom made), (6) 4ch multiple-stop time-to-digital converter (custom made), (7) pulse generator (custom made), (8) soft wares to collect data and control stepping motor. The chopping of the ion beam is carried out when ion beam passes the deflector to produce a pulse beam. A pulse beam is neutralized in the a small charge exchange cell where Ne gas was introduced through a variable leak valve up to a pressure of 1x10^-2 Pa. Thus, 20Ne0 particles impinge on a sample and the scattered particles are detected by an MCP which is located at 180°. The sample of MgO(001) cleary shows the observed periodicity of 45 deg. for the azmithal angle scans (an eight fold symmetry). The atomic dsicance betwenn first-layer and second-layer of Mg or O atoms is around three percent smaller than that between second-layer and third-layer. It has been made sure of working well in the field of electric/magnetic fiields for measurements. It is the usuful real-space observation of nanomaterial growth and direct imaging. A UHV chamber for sample measurements is kept a base pressure of ~ 10^-8 Pa for the study. These components will be described in detail.
9:00 PM - SS5.8
In situ Observations of Rapid Solidification of Metal Thin Films.
Andreas Kulovits 1 , Jorg Wiezorek 1 , Thomas LaGrange 2 , Bryan Reed 2 , Geoffrey Campbell 2
1 Mechanical Engineering and Materials Science, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Condensed Matter and Materials Division, Physical and Life Science Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractWe used the Dynamic transmission electron microscope DTEM at Lawrence Livermore National Laboratory for in situ studies of rapid solidification of metal thin films. Al, Cu, Ag and Cr thin films were molten inside the electron microscope using an excimer laser. With time delays, as short as 12 nanoseconds, an electron pulse illuminates the molten area. This unprecedent nanosecond time resolution in combination with the nanometer spatial resolution allowed us to investigate the morphology and kinetics of the advancing solid liquid interface during the solidification process. Using electron diffraction we established complete melting of the metal thin films in the illuminated area. In imaging mode we analyzed the morphology of the interface, which is planar throughout the entire solidification process. The acquisition of a series of images at different time delays in imaging mode allowed us not only to determine an average velocity ~ 4 m/s of the liquid solid interface but also how the velocity changes throughout the solidification process. In the case of Al thin films the solidification front velocity initially decreases from about ~ 10 m/s and stabilizes at about ~ 3 – 4 m/s as the solidification process progresses. These direct, in situ observations of the velocity and morphology of the rapid moving liquid solid interface during the solidification process will allow to verify theoretical models and to test computational simulations. The Work was performed under the auspices of the U.S. Department of Energy by the 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.
Symposium Organizers
John Cumings University of Maryland
Dillon Fong Argonne National Laboratory
Jianyu Huang Sandia National Laboratories
Stuart Lindsay Arizona State University
Guangwen Zhou State University of New York, Binghamton
SS6: In-Situ Studies of Magnetic and Electrical Nanostructures
Session Chairs
Wednesday AM, December 01, 2010
Gardner (Sheraton)
9:30 AM - **SS6.1
Electron Phase Microscopy of Magnetic Fields in Ferromagnets and Superconductors.
Akira Tonomura 1
1 , Hitachi, Ltd., & RIKEN, Hatoyama Japan
Show AbstractMagnetic lines of force can be quantitatively visualized by using the interaction of electron waves with electromagnetic fields. The basic principle behind this observation is given by the Aharonov-Bohm effect [1], which states that electron waves are phase-shifted by ‘vector potentials’ even when electron waves pass through spaces free of electromagnetic fields. For magnetic fields, the effect can be expressed in the simplest terms: a relative phase shift between two electron paths is given by 2 (e/h) times the enclosed magnetic flux irrespective of the velocities of electrons used. Therefore, the phase contours in an electron interference micrograph directly indicate the projected magnetic lines of force in constant magnetic flux units of h/e [2]. This observation method, which is similar to that of SQUID except for using h/e instead of h/2e for the measurement unit of magnetic flux, became possible through the use of the bright field-emission electron beams developed over the past 40 years [3].My talk will cover applications of this electron interference technique to the static and dynamic observation of the microscopic distributions of magnetic fields of magnetic heads used for high-density perpendicular recording [4], Josephson magnetic vortices penetrating between layers in high-Tc YBCO superconducting thin films, and nucleating ferromagnetic phase assisted by magnetic fields in colossal magnetoresistance [5].[1] Y. Aharonov and D. Bohm, Phys. Rev. 115 (1959) 485.[2] A. Tonomura, T. Matsuda, J. Endo, T. Arii, and K. Mihama, Phys. Rev. Lett. 44, No. 21 (1980) 1430.[3] A. Tonomura, Proc. Natl. Acad. Sci. USA. 102, No. 42 (2005) 14952.[4] J. J. Kim, K. Hirata, Y. Ishida, D. Shindo, M. Takahashi, and A. Tonomura, Appl. Phys. Lett. 92 (2008) 162501/1.[5] Y Y. Murakami, H. Kasai, J. J. Kim, S. Mamishin, D. Shindo, S. Mori, and A. Tonomura, Nat. Nanotech. 5, No 1. (January 2010), 37.
10:00 AM - SS6.2
Magnetic Domain Manipulation in Magnetostrictive Fe70Ga30 Thin Films via Direct Application of Strain Fields Observed with Lorentz Microscopy.
Paris Alexander 1 , Stephen Daunheimer 1 , Dwight Hunter 1 , Arun Luykx 1 , Lourdes Salamanca-Riba 1 , Ichiro Takeuchi 1 , John Cumings 1
1 , University of Maryland, College Park, Maryland, United States
Show AbstractThe controlled and reversible switching of magnetic domains using static electric fields has been previously demonstrated via
magneto-electric (ME) coupling in a multiferroic system.
* Piezoelectricity and
magnetostriction are coupled by way of an interfacial transfer of strain in this bilayer device in order to control magnetic switching. However, the nature of the interfacial transfer of strain in such devices is not well understood. We use
Lorentz-force transmission electron microscopy to observe the magnetic domain structure dynamics resulting from direct application of strain on magnetostrictive
iron gallium (Fe
70Ga
30) thin films. Iron-gallium films were deposited on flexible free standing membranes, and using a mechanically manipulated tip, a strain is applied directly to the film. The varied hysteretic behaviors under applied magnetic and strain fields will be presented, and the relationship between the induced magneto-crystalline anisotropy and local magnetization will be discussed.
This work was supported by the NSF-MRSEC at the University of Maryland, DMR 0520471.
*Brintlinger, T. et al. Nano Letters 10, 1219-1223 (2010).
10:15 AM - SS6.3
In Situ Transmission Electron Microscope Observation of the Dynamic Behavior of Ferroelastically Switched Domains in Bismuth Ferrite.
Christopher Winkler 1 , Lane Martin 2 , Mitra Taheri 1
1 Materials Science & Engineering, Drexel University, Philadelphia, Pennsylvania, United States, 2 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractSelect multiferroic materials exhibit a coupling between ferroelectric and magnetic order parameters, mediated by a quantum-mechanical exchange interaction. One of the most widely studied magneto-electric multiferroics is the perovskite BiFeO3 (BFO). The magneto-electric coupling in BFO allows for control of the ferroelectric domain structures via applied electric fields. BFO and other magneto-electric multiferroics constitute a promising class of materials for incorporation into devices such as high density ferroelectric and magnetoresistive memories, spin valves, and magnetic field sensors. However, the magneto-electric coupling in BFO is mediated by volatile ferroelastically switched domains that make it difficult to incorporate this material into devices. To facilitate device integration, an understanding of the microstructural factors that affect ferroelastic relaxation and ferroelectric domain switching must be developed.We investigate the evolution of ferroelastically switched ferroelectric domains in BFO thin films during many switching cycles using in situ TEM. We present evidence of domain nucleation, propagation, and switching even at applied electric fields below the coercive field. These observations indicate that the occurrence of ferroelastic relaxation in switched domains and the stability of these domains is influenced by the local microstructure of the BFO film. These biasing experiments provide a real time view of the complex dynamics of domain switching and complement scanning probe techniques.
10:30 AM - SS6.4
Dynamics and Switching of Ferroelectric Domains in Multiferroic (001) BiFeO3 Thin Films by In-situ TEM.
Christopher Nelson 1 , Pingping Wu 2 , Colin Heikes 3 , Adam Melville 3 , Carolina Adamo 3 , Chad Folkman 4 , Chang-Beom Eom 4 , Darrell Schlom 3 , Long-Qing Chen 2 , Xiaoqing Pan 1
1 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Materials Science and Engineering, Penn State University, University Park, Pennsylvania, United States, 3 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 4 Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States
Show AbstractThe dynamic processes of domain formation and growth in ferroelectric films are not fully understood. In-situ transmission electron microscopy (TEM) allows direct observation of the domain nucleation and switching pathways. In this work we study the structure and dynamics of ferroelectric domain walls such as domain nucleation and switching under applied electric field by in-situ TEM. Switching is performed using a thin-film capacitor geometry with a platinum top electrode deposited on a ferroelectric BiFeO3 film and also in a surface-probe geometry where the top switching electrode is a sharp STM tip in contact with the film surface. In both geometries the BiFeO3 films were grown by molecular beam epitaxy on TbScO3 substrates which include an epitaxial conductive LaxSr1-xMnO buffer layer to serve as a bottom electrode. The domain structure and the local polarization were determined by the relative positions of ions in atomic resolution scanning transmission electron microscopy (STEM) images. We found that the as-grown BiFeO3 films are polydomain, consisting of all four ferroelastic variants. The domain walls have an average spacing of ~10 times larger than the film thickness so that single-domain regions can be switched without interacting with the preexisting domain walls. Under the uniform field of the thin film capacitor geometry domain growth initiates at regions with the lowest nucleation energy such as dislocations and interfaces. In the inhomogenous field of the surface probe geometry, switching initiates beneath the tip and slowly propagates laterally. Since the polarization vector is inclined in (001) rhombohedral ferroelectrics such as BiFeO3, different domains are stable on opposite sides of the tip which result in a domain wall forming under the tip. We present real-time video of these switching processes and compare them to phase field simulations.
10:45 AM - SS6.5
Direct imaging of 180o Ferroelectric Domain Evolution by In Situ TEM.
Myung-Geun Han 1 , Marvin Schofield 1 , Chao Ma 1 , Lijun Wu 1 , Jason Hoffman 2 3 , Fred Walker 2 3 , Charles Ahn 2 3 , Yimei Zhu 1
1 Condensed Matter Physics & Materials Science, Brookhaven National Lab, Upton, New York, United States, 2 Department of Applied Physics, Yale University, New Haven, Connecticut, United States, 3 Center for Research on Interface Phenomena and Structures, Yale University, New Haven, Connecticut, United States
Show Abstract180o ferroelectric domain evolution in epitaxial thin films driven by an exteranl bias has been directly imaged by transmission electron microscopy (TEM). A series of external bias was applied to a cross section of Pt-coated Pb(Zr,Ti)O3 thin film grown on Nb-doped SrTiO3 substrate during TEM observation along [010] zone axis. Strong contrast in TEM images evolved around neighboring 180o domains, revealing 180o domain evolution including nucleation, forward growth, and sideway growth under various external biases. Underlying mechanism for 180o domain contrast can be explained by both violation of Friedel’s law and local strain around domain wall, which lead neighboring 180o domains with opposite polarization direction to slightly different Bragg-reflecting conditions each other [1,2]. Existing 90o domains in the film remained unchanged under external biases within the range of -15 V to 15 V, thus they prevented further growing of nearby 180o domain. Annular dark-field (ADF) scanning transmission electron microscopy (STEM) showed large Zr/Ti displacement up to 0.06 ± 0.02 nm from the center of tetragonal unit cell and reversal of local Zr/Ti displacement direction across 180o domain wall. 1. M. Tanaka and G. Honjo, J. Phys. Soc. Jap., 19, 6 (1964). 2. H. Lichte, M. Reibold, K. Brand, and M. Lehmann, Ultramicroscopy 93 (2002).
11:30 AM - **SS6.6
Using Magnetic Force Microscopy to Study Superconducting Vortices.
Ophir Auslaender 1
1 Physics, Technion - Israel Institute of Technology, Haifa Israel
Show AbstractWe have used a magnetic force microscope (MFM) to image and manipulate individual superconducting vortices. The interaction between the magnetic MFM tip and the magnetic field from vortices gives rise to a force which we use for imaging and for manipulation. I will report on experiments in two kinds of detwinned YBa2Cu3O7-δ single crystals. The behavior of individual vortices depends on the doping level. In stark contrast to their behavior in thin films, vortices in a slightly overdoped sample tilt rather than jump when we perturb them strongly. The dragging distance of vortices in this crystal is anisotropic: it is easier to drag vortices along the Cu-O chains than across them, consistent with the tilt modulus and the pinning potential being weaker along the chains. We also find that when we wiggle the top of a vortex we can drag it significantly farther than when we do not, giving rise to a dramatic dynamic anisotropy between the fast and the slow directions of the scan pattern. Surprisingly, the depinning force is not well described by activation, but rather by an exponential. In an underdoped single crystal where superconductivity is so anisotropic that a vortex should be viewed as a stack of two dimensional pancakes, we show that vortices kink rather than tilt when we perturb them. Time permitting I will discuss new results on the pnictides.
12:00 PM - SS6.7
In situ TEM Observation of Electrical Switching Phenomena in Phase Change Nanowire Memory Device.
Sung-Wook Nam 1 , Hee-Suk Chung 1 , Yeonwoong Jung 1 , Pavan Nukala 1 , Ye Lu 2 , A. T. Charlie Johnson 2 , Ritesh Agarwal 1
1 Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractMemory devices based on phase-change materials store data by switching the material into amorphous/crystalline states associated with high/low electrical resistances are being pursued as alternatives to current flash memory. In spite of extensive studies of the switching mechanisms in phase change materials, direct observation of the electrically-driven phase change process has not been achieved since the conventional thin-film phase change memory (PCM) devices are embedded within multi-layer films. One major advantage of utilizing single nanowire (NW)-based devices in lateral configuration is their unique geometry which allows direct investigations of the changes in its structure, morphology and chemical composition via in situ transmission electron microscopy (TEM) during electric switching process. Direct observation of the switching process is required to study the complex interplay of electric field on structural and chemical changes, stress build up and release and electromigration, which cannot be obtained from post-mortem analysis of thin-film devices.We utilized vapor-liquid-solid (VLS) grown Ge2Sb2Te5 (GST) NWs to study the role of electric-field during PCM operation. For TEM observation, we fabricated lateral-type GST NW devices on top of electron transparent Si3N4 membranes. Electrode wiring of the GST NW device was carried out by focused ion beam (FIB) and a specially-designed TEM holder was used to apply electrical pulses to the NW device. Combining with the real-time imaging system, in situ TEM allowed us to operate the PCM device in the TEM column, at the same time while observing the structural and chemical changes between amorphous and crystalline states. Typically, in bright field TEM, amorphous state has bright-contrast while crystalline state has dark-contrast, which comes from the difference of electron beam coherency between the two phases. Most of all, we obtained direct evidence of electric-field assisted nucleation process which guides the crystalline nuclei formation in a correlated manner with the applied electric-field, unlike the random nucleation and percolation behavior typically observed in thermally-induced recrystallization. It is believed that the electric-field lowers the thermodynamic energy barrier for amorphous-to-crystalline phase transformation due to field assisted filament generation. In addition, we will also discuss the effect of electrical stress on the built-in mechanical stress and relaxation during the field driven phase change process. High current density (> MA/cm2) required for joule-heating process induces significant electrical stress which is converted to mechanical stress and possibly influences the reversible switching process. Our observations suggest that the electric-field plays a unique role in fast switching behavior, combined with the thermal and mechanical processes caused by joule-heating process.
12:15 PM - SS6.8
A Fully Piezoelectric Goniometer for TEM Tomography and Differential Tilting.
Wei Guan 1 , Aiden Lockwood 1 , Beverley Inkson 1 , Guenter Moebus 1
1 Engineering Materials, University of Sheffield, Sheffield United Kingdom
Show AbstractPiezoelectric nanoactuators are rapidly becoming the dominant means for position control in transmission electron microscopy (TEM) because of their extremely stable and reproducible positioning ability. This technology combines TEM’s imaging resolution to offer a better way to advance the understanding of nano materials. A family of piezo-drives inserted into TEM goniometers have been developed for different applications including electron tomography which reveals the objects’ physical and chemical structures in three dimensions (3D). In this paper, we present a miniature goniometric nanomanipulation system which is fitted inside a hollowed standard specimen holder for JEOL 2000/3000 series microscopes with neither modifications to the TEM nor compromising the performance of the default TEM goniometer. The movement range of this miniaturized drive is composed of seven degrees of freedom: 3 fine translational movements (X, Y and Z axes) achieved by a quartered piezo tube, further coarse translational movements along all three axes, operated serially to the fine drive, and one rotational movement around the X-axis. Both the coarse drive and the rotary drive are using a slip-stick inertial slider mechanism. The nanomanipulation system is ideal for electron tomography as it overcomes the “missing wedge problem” by providing a full tomographic tilt range of 180° in both directions and even beyond. The smallest angular increment is decided by a single slip-stick actuation pulse, hence it can be well controlled to be less than 0.01°. Although in different parts of the rotation circle the speed can be different due to potentially unevenly distributed load on the shaft, non-uniform surface finish of the shaft etc., using an angular displacement feedback the accuracy of which is down to 0.05°, we can obtain the absolute rotated angle without relying on counting drive pulses or image calibration. A full circle rotation of a single W tip as well as its tomographic reconstruction has been achieved. Besides electron tomography, with the second specimen mount on the TEM holder, differential rotation between two parts is achieved. We have tilted a W tip against a fixed tip over 180 degrees within a gap less than 100nm, and both tips can be rotated together between ±30° by the TEM goniometer. This defines our “goniometer inside the TEM goniometer” approach, with both goniometers applicable in parallel or in series.
SS7: In-Situ TEM Studies of Evolving Nanostructures
Session Chairs
Wednesday PM, December 01, 2010
Gardner (Sheraton)
2:30 PM - **SS7.1
In situ Observation of Nucleation and Growth of Nanomaterials.
Renu Sharma 2 1
2 Center for Nanoscale Science and Technology and National Institute of Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 1 School of Mechanical, Aerospace, Materials and Chemical Engineering, Arizona State University, Tempe, Arizona, United States
Show AbstractUnderstanding the nucleation and growth mechanism of nanomaterials is one of the fundamental steps in scaling up their synthesis. During the last two decades, modified transmission electron microscopes (TEM), such as the environmental scanning/transmission electron microscope (ESTEM), have been successfully employed to follow the synthesis of nanoparticles, nanotubes and nanowires. In most cases, the sample chamber of the TEM column is used as chemical vapor deposition chamber (CVD). One way is to introduce chemical vapor or gaseous source (precursor) in TEM column where electron beam can be used to deposit nanostructures. This method is generally known as electron beam induced decomposition or EBID and the size and morphology of deposited structure is controlled by the deposition time, nature and pressure of the precursor, deposition temperature etc. EBID conditions for controlled synthesis of Fe nanoparticles using ferrocene and iron nonacarbonyl will be used as an example to illustrate the process.Another commonly used method is to introduce precursor over suitable substrate/catalyst combinations, which are heated so that precursor molecules decompose upon contact with the substrate/catalyst to deposit nanostructures. In this case, the catalyst often assists in decomposition as well as nucleation of the nanostructures, and the structure and morphology is controlled by the nature of the catalyst and reaction conditions (temperature and precursor pressure). This method has been successfully used for the synthesis of Si and Ge nanowires and carbon nanotubes. We have also employed the ESTEM to understand the nitridation of Ga/Au droplets to grow GaN nanowires where nitridation reaction kinetics plays an important role in nucleation and growth mechanism. Nucleation and growth mechanisms for nanotubes and nanowires will be explained using suitable examples.
3:00 PM - SS7.2
Release and Mobility of Iron Nanocrystals Encapsulated in Carbon Shells by in-situ STEM/HRTEM Observation.
Zhenyu Liu 1 , Noemi Aguilo-Aguayo 2 , Jacqueline L. Sturgeon 3 , Kristin L. Bunker 3 , Enric Bertran 2 , Judith C. Yang 1
1 Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Departament de Física Aplicada i Òptica, Universitat de Barcelona, Barcelona Spain, 3 , The RJ Lee Group, INC, Monroeville, Pennsylvania, United States
Show AbstractIn this study, we examined the dynamics of the release, migration and agglomeration of iron nanocrystals that were originally encapsulated in graphite-like carbon shells by in-situ scanning transmission electron microscopy (STEM)/high resolution transmission electron microscopy (HRTEM). Iron nanocrystal particles migrate out of the graphite-like carbon shells at temperatures of 400oC and higher. The iron nanocrystal particles inside the graphite-like carbon shells shrank continuously until they had completely vanished and left hollow carbon shells behind. Large iron clusters on the scale of several hundreds nanometers were observed on the surface of the carbon shells in the temperature range of 600~800oC. At temperatures between 800oC and 1200oC, the iron clusters on the surface began to evaporate. After heating to 1200oC, only few iron nanocrystal cores still remained. The electron beam may play an important role in the in-situ observation; at the typical imaging conditions with a beam current density of ~80 PA/cm2, the surface amorphous carbon layer disappeared and the graphite-like carbon shells shrank with graphitic shell number increasing. However, for an electron beam current density of 100 PA/cm2, re-crystallization of the iron nanocrystal cores was observed. We hypothesized that the shrinkage of graphite-like carbon shells induced by electron beam and heating effects produced contraction and high pressure, and caused iron nanocrystals to re-crystallize.
3:15 PM - SS7.3
In Situ TEM Studies of Supported Palladium Catalysts for the Oxidation of Methane.
Jakob Wagner 1 , Jan-Dierk Grunwaldt 2 3 , Thomas Hansen 1 , Rafal Dunin-Borkowski 1
1 Center for Electron Nanoscopy, Technical University of Denmark, Lyngby Denmark, 2 Department of Chemical and Biochemical Engineering, Technical University of Denmark, Lyngby Denmark, 3 Institute of Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Karlsruhe Germany
Show AbstractSupported palladium particles are used in some of the most active catalysts for methane combustion under lean burn conditions in exhausts and turbine combustors.Here, we use in situ transmission electron microscopy (TEM), in situ X-ray absorption spectroscopy (XAS) and catalytic data to gain insight into structure-performance relationships in a flame-synthesized Pd/ZrO2 catalyst during methane oxidation.XAS is used to provide averaged information, while TEM is used to probe individual nanoparticles and agglomerates. Observing the same tendencies using TEM and XAS in situ provides valuable information of the structure, which can then be linked to the performance of the catalyst under working conditions.Earlier studies, which focused on in situ XAS and X-ray diffraction [1], suggested that the reduction of Pd particles takes place rapidly on heating, accompanied by sintering and an associated decrease in catalytic activity leading to a hysteresis during temperature cycling.By using a differently pumped environmental TEM [2], we are able to study the catalyst at elevated temperature (800°C) in 5-10 mbar of flowing CH4:O2 (1:4), while maintaining a spatial resolution that allows atomic planes in both the Pd and the ZrO2 to be resolved. We observe structural changes of both the Pd particles and their support during heating in situ in the TEM. By combining this information with spatially resolved electron energy-loss spectroscopy, we obtain information about the crystal structures, morphologies and electronic structures of individual Pd particles.References[1] J.-D. Grunwaldt, N. van Vegten and A. Baiker, Chem. Commun. 2007 (2007) 4635.[2] T. W. Hansen, J. B. Wagner and R. E. Dunin-Borkowski, Materials Science and Technology (2010) in press.
3:30 PM - SS7.4
Dynamics of Supported Metal Nanoparticles Observed in a CS Corrected Environmental Transmission Electron Microscope.
Thomas Hansen 1 , Jakob Wagner 1 , Rafal Dunin-Borkowski 1
1 Center for Electron Nanoscopy, Technical University of Denmark, Kgs. Lyngby Denmark
Show AbstractMany catalysts consist of metals or metal alloys, which are deposited onto a support material in the form of nanoparticles in order to maximize their exposed surface area. In a catalytic reactor, the particles tend to sinter, resulting in a decrease in catalytic performance. Several models of sintering have been put forward [1, 2]. However, most experimental investigations have been post mortem studies, revealing only the final state of the catalyst.Transmission electron microscopy (TEM) has been used extensively in catalysis research [3]. However, in contrast to chemical reactors, a conventional TEM is a high vacuum tool. Thus, observations do not always reflect the active states of materials. Environmental TEM (ETEM) provides the capability to expose samples to gases during imaging and analysis [4]. Even though the gap between reactor and high-vacuum pressures has not yet been fully bridged, progress has been made towards observing materials in their working environment.The combined capabilities of ETEM and image CS correction provide unique possibilities to study relationships between the surface structures of catalytic materials and surrounding atmospheres. However, as industrial catalysts are usually complex high surface area materials, they are often not suited for fundamental studies. Accordingly, we have studied a model system comprising gold nanoparticles on sheets of boron nitride and graphite. The nanoparticles were formed from a sputter coated thin film of gold, which readily formed nanoparticles ranging from a few nm up to 20 nm in size. The samples were exposed to oxidizing and reducing environments at various temperatures in situ in the ETEM.Under these conditions, mobility of the particles was clearly visible, while maintaining lattice resolution of both the support material and the Au nanoparticles. Some particles remained immobile during observation, while others behaved dynamically. Some of the particles sintered by migration and coalescence, while others were observed to shrink in size and finally disappear as neighboring particles grew by Ostwald ripening. These observations indicate that several sintering mechanisms may occur simultaneously. Particles on steps were observed to be significantly smaller than those on terraces, suggesting a stronger interaction of the metal and support at these sites. By quantifying these observations, fundamental insight into activation energies and energy barriers for sintering processes can be studied. In the future, in order to fully quantify image contrast in such experiments, a deeper understanding of the scattering of fast electrons in the presence of gas molecules in the pole piece gap of the microscope is needed.References[1]J.T. Richardson and J.G. Crump, J. Catal. 56 (1979) 417.[2]C. H. Bartholomew, Appl. Catal. A. 107 (1993) 1.[3]A.K. Datye, J. Catal. 216 (2003) 144.[4]T.W. Hansen, J. B. Wagner and R.E. Dunin-Borkowski, Mater. Sci. Tech. (2010) Accepted.
3:45 PM - SS7.5
Sublimation Induced Shape Evolution of Silver Cubes.
Yong Ding 1 , Fengru Fan 1 2 , Zhongqun Tian 2 , Zhong Lin Wang 1
1 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Department of Chemistry, Xiamen University, Xiamen China
Show AbstractSurface energy is a criteria usually employed to identify the stability of a solid surface. Nanoparticles of fcc noble metals are usually enclosed by the lower energy surfaces such as {111} and {100}, because these surfaces are believed to have the lowest energy, typically following {111} < {100} < {110}. However, one of the simple manifestations of the presence of a surface is the relaxation of atoms located at the first, second and even deeper surface layers, either inwards or outwards with respect to bulk terminated positions, which can contribute to the surface energy in a realistic situation. As a result of surface relaxation that may sensitively depend on temperature, the surface energy could be dramatically minimized. Due to the high density of surface atoms and their relative high coordination numbers, the relaxations of metal {111} surface in room temperature are expected to be minimal. With the increase of temperature, the contribution of the lattice vibration to the surface energy increases. As we know that the creation of a crystal surface meaning the broken of bulk translational symmetry, implies that an anharmonic behavior of the restoring forces should be expected. Such anharmonic effects become increasingly crucial on the surface stability with the temperature close to the melting point. According to Lindemann’s melting criterion, the anisotropic surface melting was predicted. Taking Ag as an example, the melting points of {110}, {100} and {111} surface, respectively, are 887, 906 and 966 K. After taking account of the multilayer relaxation effect, the theory by Jayanthi et al. leads to an reversed order in which the low-index surfaces of metals are predicted to become unstable, from {110}-{100}-{111} to {111}-{100}-{110}. In order to clarify which surface in fcc metals is the thermal stable one at high temperature, surface sublimation and shape transformation of silver cubes, enclosed by {100} surfaces with ~100 nanometer in size, were examined by in situ transmission electron microscopy. When temperature increased to above 1000 K, accompanying to the elimination of low-index {100} surfaces via solid state sublimation rather than melting/diffusion process, the high-index {110} surfaces started to form, resulting in the formation of truncated octahedra. The result shows that high-index surfaces of fcc metals are more stable when the temperature is close to its melting point.Reference:Yong Ding, Fengru Fan, Zhongqun Tian and Zhong Lin Wang, Small, 5(24), 2812-2815 (2009).For more information, please visit: http://www.nanoscience.gatech.edu/zlwang
4:30 PM - SS7.6
Effect of Oxygen Pressure on the Initial Oxidation Behaviorof Cu and Cu-Au Alloys.
Langli Luo 1 , Yihong Kang 2 , Zhenyu Liu 2 , Judith Yang 2 , Guangwen Zhou 1
1 Department of Mechanical Engineering & Multidisciplinary Program in Materials Science and Engineering, State University of New York, Binghamton, Binghamton, New York, United States, 2 Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractA wide gap exists between our present atomic-scale knowledge of metal oxidation derived from conventional ultrahigh vacuum (UHV) surface science experiments and the oxidation mechanisms obtained from the growth of bulk oxide thin films under technologically relevant realistic (or near-) atmospheric conditions. To bridge this pressure gap, we present an in-situ transmission electron microscopy (TEM) study of the initial oxidation stage of Cu(100) and Cu-Au (100) surfaces where the oxygen partial pressure varies from 5x10-4 to 150 Torr. For Cu(100), with increasing oxygen partial pressure (pO2), the nucleation density of the oxide islands increases and so does the growth rate of the oxide islands. As the pO2 continues to increase, a transition from epitaxial cube-on-cube Cu2O islands to randomly oriented oxide islands is observed. A kinetic model based on the classic heterogeneous nucleation theory is developed to explain the unusual effect of oxygen partial pressure on the oxide’s epitaxy. It is shown that such a transition in the oxide nucleation orientation is related to the effect of oxygen pressure on the nucleation barrier and atom collision rate. The Cu-Au alloy revealed the same oxygen pressure dependency of the oxide nucleation orientation as pure Cu oxidation but requires a larger supersaturation in oxygen pressure to nucleate oxide islands.
4:45 PM - SS7.7
In-Situ Studies of the Initial Stage of Cu-Ni Alloy Oxidation.
Yihong Kang 1 , Langli Luo 2 , Matthew France 3 , Guangwen Zhou 2 , Judith Yang 3
1 Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Department of Mechanical Engineering & Multidisciplinary Program in Materials Science and Engineering, State University of New York, Binghamton, New York, United States, 3 Chemical Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractIn-situ transmission electron microscopy (TEM) is ideal for providing insights into the nanoscale oxidation processes of metals and alloys. Previous studies show the epitaxial growth of Cu2O islands during the initial stages of oxidation of pure Cu (100), where surface diffusion and strain impact the morphology of the oxide. The addition of a secondary element can change the oxidation mechanism. If the secondary element is non-oxidizing, like Au, it will limit Cu2O growth due to the depletion of Cu near the oxide island that significantly slows down the oxide growth as well as lead to an unusual dendritic shape, limiting its ability to form a uniform protective oxide. On the other hand, if the secondary element is oxidizing, for example Ni, the alloy will show more complex behavior, where duplex oxide islands were observed. In this research, the initial oxidation stage of single crystal Cu-Ni (100) films, which are made by electron beam deposition onto (001)NaCl, is observed under various temperature and oxygen partial pressure (pO2). According to thermodynamic and kinetic properties of Cu and Ni, under lower temperature and pO2 only epitaxial cube-on-cube NiO islands form. As temperature and pO2 increase, Cu2O islands will nucleate and grow. The oxidation behavior of Cu-Ni alloys as function of alloy composition, temperature and pO2 is studied Via in situ TEM. Cross-sectional samples of oxide islands will be characterized by high resolution TEM to reveal the duplex oxide islands formed by NiO and Cu2O. The morphology of oxide islands on Cu-Ni alloys will be compared with oxide islands on pure Cu obtained under the same oxidation conditions in order to reveal the effect of presence of Ni on the oxidation of Cu.
5:00 PM - SS7.8
Effect of Titanium Dioxide Surface Reconstruction on Epitaxy of Gold Nanocrystals.
Shankar Sivaramakrishnan 1 2 , Xin Chen 1 2 , Jian-Min Zuo 1 2
1 Materials Science and Engineering, University of Illinois, Urbana Champaign, Urbana, Illinois, United States, 2 Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana Champaign, Urbana, Illinois, United States
Show AbstractAu nanoclusters supported on TiO2 have attracted much attention due to their ability to function as efficient catalysts. Despite years of research, many fundamental aspects of this simple metal nanocluster /oxide system remain uncertain. For instance, even though it is well known that Au forms stable epitaxial gold nanocrystals (NCs) on TiO2 (110) upon air or vacuum annealing, the origin of this stable interfacial bonding in epitaxial Au NCs is still a point of debate. In this work, we report the structural evolution and epitaxy of gold NCs on TiO2 (110) surfaces for oxidized (oxygen rich) and reduced TiO2 surfaces using in-situ Reflection High Energy Electron Diffraction (RHEED) and ex-situ aberration corrected Scanning Transmission Electron Microscopy (STEM) and Atomic Force Microscopy (AFM) and show that (1x2) reconstructions on TiO2 (110) surfaces play a key role in stabilizing the epitaxy of Au on TiO2 (110). Using in-situ RHEED we observed that for vacuum annealed samples, the onset and completion of Au NC epitaxy happens at much lower temperatures on a reduced (and reconstructed) surface compared to an oxidized (unreconstructed) surface. We will show that the above reported lowering of epitaxial transformation temperature of Au NCs on reduced TiO2 (110) surfaces happens due to the preferential nucleation of Au NCs over (1x2) TiO2 reconstructions. We propose a novel interfacial atomic structure for stable epitaxial Au NCs on (1x2) reconstructed TiO2 (110) using cross-sectional aberration corrected STEM.
5:15 PM - SS7.9
High Spatial Resolution Crystallite Orientation and Phase Mapping in the Transmission Electron Microscope.
Peter Moeck 1 2 , Sergei Rouvimov 1 , Ines Haussler 2 , Anna Mogilatenko 2 , Holm Kirmse 2 , Wolfgang Neumann 2 , Edgar Rauch 3 , Muriel Veron 3 , Stavros Nicolopoulos 4
1 Physics, Portland State University, Portland, Oregon, United States, 2 Physics, Humboldt University, Berlin Germany, 3 SIMAP/GM2 lab, CNRS-Grenoble, Grenoble France, 4 , NanoMEGAS, Brussels Belgium
Show AbstractA novel semi-automatic technique for the mapping of crystallite phases and orientations of polycrystalline materials in a transmission electron microscope (TEM) has been employed. When the TEM is equipped with a field emission gun, this technique delivers (in the nano-probe mode) a significantly higher spatial resolution than electron backscatter Kikuchi diffraction (EBSD) in a scanning electron microscope (SEM) and is also less sensitive to the plastic deformation state and the surface of the crystallites. The technique is based on template matching of experimental electron diffraction spot patterns to their pre-calculated theoretical counterparts. Very promising results have so far been obtained with this technique for polycrystalline metal films, microelectronic composite structures, and inorganic nanocrystalline powders [1]. The procedure of crystallite orientation and phase mapping comprises the automated collection of single crystal precession electron diffraction patterns on an external digital camera while scanning the area of interest with a nanometer-sized primary electron beam, followed by off-line data processing. The software that goes with this hardware is flexible in its intake of experimental data so that it can also create crystallite orientation and phase maps of nanocrystal from the amplitude part of Fourier transforms of high resolution TEM images [2]. For inorganic nanocrystals with small to medium sized unit cells, an objective-lens aberration corrected TEM needs to be utilized. It has also been demonstrated that the single crystal precession electron diffraction (PED) mode [3] improves the reliability of this technique significantly as the 180 degree ambiguity in the indexing of spot patterns from the zero order Laue zone can be reliably overcome. This is because more reflections are excited in PED patterns and there are frequently also reflections from higher order Laue zones. For inorganic nanocrystal without heavy elements and sizes of below some 10 to 50 nm, the intensities of PED reflections are quasi-kinematical (i.e. roughly proportional to the square of the modulus of the structure factors). Such PED patterns are, therefore, very useful for advanced structural fingerprinting of nanocrystals in a TEM [4].[1] E.F. Rauch et al., Zeits. Krist. 225 (2010) 103[2] P. Moeck et al., Mater. Res. Soc. Symp. Proc. 1184 (2009) 49[3] P. Moeck and S. Rouvimov, In: Drug Delivery Nanoparticles: Formulation and Characterization, Informa, New York, 2009, 270[4] P. Moeck and S. Rouvimov, Zeits. Krist. 225 (2010) 110
5:30 PM - SS7.10
Quantitative Single-Image Projected Thickness Map Reconstruction for Dynamic In Situ Transmission Electron Microscopy.
Samuel Eastwood 1 , David Paganin 1 , Amelia Liu 1
1 School of Physics, Monash University, Clayton, Victoria, Australia
Show AbstractPropagation-based phase retrieval techniques are becoming increasingly popular in the transmission electron microscope (TEM) to reconstruct the specimen potential [1], magnetization [2], and structure [3] at the nanometer length scale. While these techniques are quantitative, they often rely on multiple images taken at different objective lens defoci. The success of the reconstructions then relies upon the mechanical and electrical stability of the instrument, the stability of the specimen under electron irradiation and adequate alignment of the images prior to reconstruction. The acquisition of multiple images limits the temporal resolution of these techniques for measurement of dynamic changes to the specimen during in situ experiments.Here we describe a quantitative technique that uses a single under-focused phase contrast TEM image, and essentially reverses the effects of the microscope contrast transfer function to obtain the projected thickness map of the specimen. Our method extends a technique that was developed for x-ray phase contrast microscopy [4], to the spherically aberrated objective optics of the TEM [5]. The reconstruction algorithm is non-iterative and stable, and computationally efficient. It may be applied to single-material objects in the strong phase/weak absorption regime. It requires several input parameters such as microscope defocus and spherical aberration and the material’s linear attenuation coefficient and mean inner potential. Since it only requires a single image, it is ideal for dynamic in situ measurements of phenomena. We anticipate that the technique will be extremely useful for measuring the distribution of voids in glasses during in situ deformation.We will discuss the limits to the spatial resolution of the technique, and the development of iterative algorithms that will optimize the input parameters without precise former knowledge, thereby automating the reconstruction. The automatic reconstruction may be applied to each frame of a movie, allowing for changes to microscope parameters during dynamic experiments.[1] S. Bajt, A. Barty, K. A. Nugent, M. McCartney, M. Wall, D. Paganin, Ultramicroscopy, 83, 67, (2000)[2] T. C. Petersen, V. J. Keast, K. Johnson and S. Duvall, Phil. Mag., 87, 3567, (2007)[3] T. C. Petersen, V. J. Keast and D. M. Paganin, Ultramicroscopy, 108, 805, (2008)[4] D. Paganin, S. C. Mayo, T. E. Gureyev, P. R. Miller, and S. W. Wilkins, J. Microsc., 206, 33, (2002)[5] A. C. Y. Liu, D. M. Paganin, L. Bourgeois and P. N. H. Nakashima, to be published.