Philip Batson, Rutgers University
Gianluigi Botton, McMaster University
Mathieu Kociak, CNRS
Johan Verbeeck, EMAT, University of Antwerp
Symposium Support Attolight
JEOL USA, INC.
ZZ3: Mapping Fields II
Tuesday PM, April 07, 2015
Marriott Marquis, Yerba Buena Level, Nob Hill C/D
2:30 AM - *ZZ3.01
Direct Imaging of Electromagnetic Fields Inside Materials by Scanning Transmission Electron Microscopy
Naoya Shibata 1
1The University of Tokyo Tokyo JapanShow Abstract
Aberration-corrected scanning transmission electron microscopy (STEM) has become an indispensable tool for characterizing atomic-scale structure in materials and devices. In STEM, a finely focused electron probe is scanned across the specimen and transmitted and/or scattered electrons from a localized material volume are detected by the post specimen detector(s) as a function of raster position. By controlling the detector geometry, we have a lot of flexibility in determining the contrast characteristics of STEM images and the formation mechanisms involved. We have developed an area detector which we refer to as the "Segmented Annular All Field (SAAF)" detector and which is capable of atomic-resolution STEM imaging. This area detector can obtain many simultaneous atomic-resolution STEM images which are sensitive to the spatial distribution of scattered electrons on the detector plane.
By taking the difference between the images from diametrically-opposed detector segments, we can form what are known as differential phase contrast (DPC) images. DPC STEM images approximate the gradient of the object potential (= fields) taken in the direction of the diametrically-opposed detector segments. In this presentation, we will discuss our recent and on-going researches of local electromagnetic field characterization in materials and devices using DPC STEM.
3:00 AM - *ZZ3.02
Deciphering Ferroelectric Order in Individual Nanometer-Scale Crystals
Mark J. Polking 2 Myung-Geun Han 4 Amin Yourdkhani 6 Valeri Petkov 5 Christian F. Kisielowski 3 Vyacheslav Volkov 4 Yimei Zhu 4 Gabriel Caruntu 6 A. Paul Alivisatos 1 Ramamoorthy Ramesh 7
1University of California, Berkeley Berkeley United States2Harvard University Cambridge United States3Lawrence Berkeley National Laboratory Berkeley United States4Brookhaven National Laboratory Upton United States5Central Michigan University Mount Pleasant United States6Central Michigan University Mount Pleasant United States7University of California, Berkeley Berkeley United StatesShow Abstract
Nanoscale ferroelectrics have emerged as leading contenders for the next generation of non-volatile memory devices, nanoscale actuators, energy conversion and storage devices, and many other applications. Vital to the practical success of these devices is a clear understanding of the fundamental nature of ferroelectric order at reduced dimensions. The physical picture of ferroelectric order at nanoscale length scales has continued to evolve from early work indicating the complete quenching of polar order to more recent studies that have explored the disordering of local polar distortions or the emergence of vortex polarization states. In addition, the physical mechanisms governing this size-dependent behavior remain a subject of some contention, with previous reports implicating depolarization fields, internal strains, and other driving forces. Progress on these questions has been hindered both by the difficulty of synthesizing monocrystalline nanomaterials with well-controlled sizes, morphologies, and surface structures and by a reliance on ensemble measurements, which obscure material behavior through statistical averaging. Here, we examine ferroelectric ordering in individual nanocrystals synthesized via colloidal chemistry using atomic-resolution transmission electron microscopy, off-axis electron holography, and piezoresponse force microscopy. We examine two types of ferroelectric nanomaterials in this study: 5-8 nm nanocrystals of the ferroelectric semiconductor GeTe and 5-15 nm nanocubes of the traditional oxide ferroelectric BaTiO3. Through-focus exit wave reconstructions of these particles calculated using the Gerchberg-Saxton algorithm allow sub-Angstrom ferroelectric distortions to be imaged on a local scale in individual particles, leading to spatial maps of ferroelectric order at nanoscale dimensions. These maps are complemented with direct imaging of ferroelectric polarization in BaTiO3 nanocubes using off-axis electron holography. These results indicate a robust, linearly ordered ferroelectric polarization in both GeTe and BaTiO3 down to dimensions of at least 5 nm. Comparison of highly conducting GeTe with insulating BaTiO3 using Raman spectroscopy and X-ray atomic pair distribution function analysis highlights the roles of both depolarization effects and size and shape-dependent internal strains in driving ferroelectric size effects. In addition to our current results, prospects for the discovery of monodomain vortex polarization states, the analysis of ferroelectric phase transitions at the single-particle level, and other emerging directions will be discussed.
3:30 AM - ZZ3.03
Quantitative Measurement of the Influence of Dielectric Precipitates on Electric Field Distributions around Metallic Atom Probe Needles Studied by Electron Holography
Vadim Migunov 2 Andrew London 3 Michael Farle 1 Rafal Dunin-Borkowski 2
1Univ of Duisburg-Essen Duisburg Germany2Ernst Ruska-Centre, Peter Gruenberg Institute, Research Centre Juelich Juelich Germany3University of Oxford Oxford United KingdomShow Abstract
Atom probe tomography (APT) involves the atom-by-atom field evaporation of a needle-shaped specimen, in order to provide a reconstruction of the identity and position of each atom . The influence of different phases in an APT needle on the electrostatic field surrounding it  has been described theoretically but never previously measured experimentally with nm spatial resolution.
Here, we apply off-axis electron holography in the transmission electron microscope (TEM) to study an electrically biased Fe needle that contains Y2O3 precipitates. We examine differences between phase images recorded with different voltages applied between the needle and a counter-electrode, in order to remove contributions to the recorded signal from mean inner potential and magnetic contributions to the phase.
Our results are used to provide maps of the electrostatic potential around the needle with a spatial resolution of approximately 1 nm, both in projection and in three dimensions by acquiring tomographic tilt series of electron holograms. Our measurements are compared with predictions for the effect of precipitates in metallic specimens on the equipotential contours surrounding them .
 Miller, M. K. Atom probe tomography: analysis at the atomic level., Kluwer Academic/Plenum Publishers, New York, 2000.
 Vurpillot, F.; Bostel, A.; Blavette, D. Appl. Phys. Lett. 76 (2000) 3127-3129.
 Oberdorfer, C.; Schmitz, G. Microsc. Microanal. 17 (2010) 15.
3:45 AM - ZZ3.04
Effect of Electron Beam Induced Currents on Electron Holographic Potentiometry of GaN
Tore Niermann 1 Jae Bum Park 1 Michael Lehmann 1
1Technische Universitauml;t Berlin Berlin GermanyShow Abstract
Potentiometry by means of off-axis electron holography is an unique technique, which allows the measurement of the spatially resolved electric potential down to the nanometer scale. Under kinematical diffraction conditions and in the absence of magnetic fields, the electron beam passing through the specimen experiences a phase shift with respect to a vacuum beam. This phase signal is proportional to thickness and potential.
When this technique is applied to model systems like p-n junctions, typically measured phase differences and hence built-in voltages are lower than values expected for the structures. In some semiconductors like Si or GaAs this mismatch is small and can mostly be explained by damages to the surfaces during preparation (structural changes, Fermi level pinning). However, in GaN the observed voltages only are 10-20% of the expected ones.
We conducted electron holographic experiments on GaN p-n junctions in needle-shaped specimen. This geometry restricts possible electric current paths to the needle itself. We observed a logarithmic dependency of the measured potential difference on the intensity of the probing electron beam. A reduction of the illumination dose rate by 3 orders of magnitude gave an increase of roughly 2.5x of the observed potential difference. The measured behavior can be quantitatively explained, when the specimen is modeled like a solar cell under open-circuit conditions.
From Si and GaAs it is known, that expected voltages are most often obtained, when the surface of the specimen is coated with conductive carbon [1,2]. Within the solar-cell model this corresponds to short-circuit conditions, where the voltage drop at the p-n junction equals the drop at the non illuminated junction. The investigated GaN-needles were already covered by conductive carbon contamination during the preparation. After changing the conductivity of the surfaces of the GaN-needles by plasma-cleaning and wet etching, we observed no change in illumination dependency. We conclude from this, that in the contrary to Si the damaged surface layers in GaN bear a large contact resistance and thus a short circuiting is not possible by such simple measures as carbon coating in this material.
Also effects of beam damage were noted over time. A drop of the measured potential by a factor close to two occurred within one hour during illumination with a dose rate of 332 e/nm2s at 300kV. We attribute this effect to the generation of point defects, as no changes in the specimens structure were directly observed.
The experiments clearly show for the first time, that especially the generation of electron-hole pairs and their flux must be considered and controlled in electron holographic experiments in order to obtain quantitative results.
We acknowledge support from the German Research Foundation (DFG) within CRC 787.
 D. Cooper et al., J. Appl. Phys. 101, 094508 (2007).
 M. R. McCartney et al., Appl. Phys. Lett. 80, 3213 (2002).
ZZ4: Novel Imaging and Structure Solution Methods
Tuesday PM, April 07, 2015
Marriott Marquis, Yerba Buena Level, Nob Hill C/D
4:30 AM - *ZZ4.01
Methods to Determine the Atomic Structure of Nanostructured Materials
Joanne Etheridge 1
1and Department of Materials Engineering Monash University AustraliaShow Abstract
Electron wavefields can be brought to a focal point smaller than an atom, enabling small volumes of matter to be probed and characterized. The resultant scattered wavefield contains a wealth of information about the specimen that can be detected selectively to isolate and ‘image&’ specific structural information. This talk will describe different methods to achieve this to solve the atomic structure of nanostructured materials. It will illustrate these with a range of materials applications, such as the determination of the atomic structure and stability of nanoparticle facets ; the determination of the local atomic structure of “chessboard&’ nanostructures in lithium-based titanate perovskites ; and the measurement of local polarity, dopant concentration and atomic-scale morphology in semiconducting nanowire quantum wells [3,4]. Several methods using focused electron wavefields will be described, including: (i) A new approach for the determination of centrosymmetric structures from the direct observation of structure factor phases from features in convergent beam electron diffraction patterns . (ii) Methods for the quantitative interpretation of the intensity in atomic resolution imaging and diffraction data for the measurement of local atomic and electronic structure. (iii) Pseudo-confocal scanning transmission electron microscopy methods which record the scattered intensity in a plane conjugate to the specimen (as opposed to the diffraction plane) for obtaining depth and chemical information [6,7].
 H. Katz-Boon, C. Rossouw, M. Weyland, A. M. Funston, P. Mulvaney, J. Etheridge, Nano Letts (2011) 11, 273-278 and manuscript submitted.
 R. Withers, L.N. Bourgeois, A. Snashall, Y. Liu, L. Noren, C. Dwyer, J. Etheridge, Chem. Mater. (2013) 25 190minus;201 and Y. Zhu et al manuscript in preparation.
 C.L. Zheng, J. Wong-Leung, Q. Gao, H.Tan, C. Jagadish, J.Etheridge, Nano Letts (2013) 13, 3742-3748
 H. Kauko, C.L. Zheng, Y. Zhu, S. Glanvill, C. Dwyer, A.M. Munshi, B.O. Fimland, T.J. van Helvoort, J. Etheridge, App Phys Letts (2013) 103 232111.
 P.N.H. Nakashima, A.F. Moodie, J. Etheridge, Proc Nat Acad Sci (2013) 110 14144-14149 (2013)
 J. Etheridge, S. Lazar, C. Dwyer, G.A. Botton, Phys Rev Letts (2011) 106, 160802.
 C.L. Zheng, Y. Zhu, S. Lazar, J. Etheridge, Phys Rev Letts (2014) 112, 166101.
5:00 AM - *ZZ4.02
Direct Imaging of Surface Reconstructions by Atomic Resolution Secondary Electron Microscopy
Jim Ciston 2 Hamish G Brown 4 Adrian J D'Alfonso 4 Pratik Koirala 3 Colin L Ophus 2 Yuyuan Lin 3 Yuya Suzuki 5 Hiromi Inada 5 Yimei Zhu 1 Les J Allen 4 Laurence D Marks 3
1Brookhaven National Laboratory Upton United States2Lawrence Berkeley National Laboratory Berkeley United States3Northwestern University Evanston United States4University of Melbourne Parkville Australia5Hitachi High Technologies Ibaraki JapanShow Abstract
Modern aberration-corrected scanning transmission electron microscopes have enabled the simultaneous collection of atomically resolved signals relating to coherent scattering (bright field and annular bright field imaging), structural information based on thermal scattering to large angles and known as high-angle annular dark-field (HAADF) imaging, bonding information using electron energy-loss spectroscopy (EELS), and element identification using both EELS and energy dispersive x-ray spectroscopy. Atomic resolution imaging based on secondary electron (SE) signals was also demonstrated in 2009 , but the technique is only slowly growing in use. While these SE signals are highly surface sensitive due to the narrow escape depth of electrons with energies <50eV [2,3], atomic resolution SE imaging of surface structures that differ from a simple bulk termination has not been previously demonstrated. The ability to simultaneously record surface sensitive SE and bulk dominated HAADF signals at atomic resolution makes the problem of surface structure registration to the bulk lattice highly tractable, which is a distinct advantage over other scanning probe methods. However, interpretability of the atomic resolution SE signal relies on the development of first-principles simulations of SE images.
We have recently studied the c(6×2) reconstruction on the (100) surface of single crystal SrTiO3 through simultaneous atomic resolution SE and HAADF imaging and complementary HREM imaging. Preliminary analysis indicates that the registration between the surface structure and bulk of the previously reported structure, primarily refined from surface x-ray diffraction and scanning tunneling microscopy (STM) experiments , is incorrect. Interpretation of the experimental SE measurements from first principles is now possible using a recently developed quantum mechanical model to simulate the SE images. This approach takes into account the probability and angular distribution of electrons that are ejected from atoms in the specimen when ionization of both core and semi-core electrons occurs . Our preliminary simulations of a newly proposed structure of the SrTiO3-<100>-c(6×2) reconstruction are in good agreement with the bulk-subtracted experimental SE data, and consistent with previously reported data from STM, Auger spectroscopy, and x-ray diffraction measurements. The structure solved by SE imaging is also stable in density functional theory simulations, and is on the thermodynamic convex hull of known reconstructions on SrTiO3 <100>.
 Y Zhu et al., Nat. Mater. 8 (2009) p. 808.
 H Seiler, J. Appl. Phys. 54 (1983) p. R1.
 A Howie, J. Microsc. 180 (1995) p.192.
 CH Lanier, et al., Phys. Rev. B 76 (2007) 045421
 HG Brown et al., Phys. Rev. B 87 (2013) 054102.
5:30 AM - ZZ4.03
Quantitative Real Space Crystallography at the Nanoscale
Joseph Houston Dycus 1 Xiahan Sang 1 Adedapo A Oni 1 Christopher Fancher 1 Scott Findlay 3 Jacob L Jones 1 Carl C Koch 1 Les J Allen 2 James M. LeBeau 1
1North Carolina State Univ Raleigh United States2University of Melbourne Parkville Australia3Monash University Parkville AustraliaShow Abstract
Accurate crystallographic determination is essential for gaining key insights into material behavior. X-ray and neutron based diffraction methods, for example, provide excellent precision and accuracy, but have comparatively poor spatial sensitivity. In contrast, scanning transmission electron microscopy (STEM) can directly probe real space crystallographic information with atomic resolution. Although STEM has advanced significantly in recent years, accurate distance information has remained elusive due to specimen drift and scan system distortion.
In this talk, we will demonstrate that revolving STEM (RevSTEM) enables direct, accurate, and precise length measurements at the unit-cell scale. By measuring distortion from a set of images acquired with rotated scan coordinates, we reverse the effects of drift from every frame that are then averaged together. The final image has enhanced signal to noise, which enables precise determination of atom column positions, Using silicon as a calibration, we remove residual distortion introduced by the scan system to obtain an accurate and precise distance scale. This calibration is then applied to subsequent imaging of other samples. As a test of accuracy, we will show that lattice parameters of pure Bi2Te3 and Bi2Se3 obtained from STEM match those from X-ray powder diffraction to within 0.1 %.
Further, we will demonstrate that the approach can even be used to determine alloy composition by applying Vegard&’s Law to the STEM measured lattice parameters using a mixed Bi2Te3-Bi2Se3 crystal. We will also discuss a comprehensive analysis of the atomic structure employing atomic resolution chemical spectroscopy to determine site preference of the atomic species. We will show that Se resides almost exclusively within the middle layer,Te(2), of the Bi2Te3 quintuple - Te(1)-Bi-Te(2)-Bi-Te(1) - which are each held together by van der Waals forces. We will show that within the alloy unit-cell, bond lengths vary between those of the pure samples, as expected. The van der Waals gap, however, is found to vary anomalously by increasing relative to the pure compounds. Finally, we will discuss the general applicability of the approach to other materials systems.
5:45 AM - ZZ4.04
Conventional Transmission Electron Microscopy Imaging beyond the Diffraction and Information Limits
Florian Krause 1 Andreas Rosenauer 1 Knut Mueller 1 Marco Schowalter 1 Thorsten Mehrtens 1
1University of Bremen Bremen GermanyShow Abstract
There are mainly two complementary imaging modes in transmission electron microscopy (TEM): Conventional TEM (CTEM) and scanning TEM (STEM). In the CTEM mode the specimen is illuminated with a plane electron wave, and the direct image formed by the objective lens is recorded in the image plane. STEM is based on scanning the specimen surface with a focused electron beam and collecting scattered electrons with an extended disk or ring-shaped detector. In our contribution we introduce ISTEM (imaging STEM), a new TEM imaging mode [Phys. Rev. Lett. 113 (2014) 096101] which combines STEM illumination with CTEM imaging. We use a CCD camera to acquire images formed with the focused electron beam scanning over the specimen. As the acquisition time of the CCD-camera is equal to the area scan time, the images corresponding to all the probe positions are summed up. The wave functions for different electron beam positions occur at different times, so that they cannot interfere and corresponding images are summed up incoherently. Thus, ISTEM exploits an improvement in resolution obtained by switching the spatially coherent illumination to highly incoherent illumination. The gain in resolution can easily be understood for the case of a completely incoherent illumination where the transfer function is given by the autocorrelation of the coherent transfer function, whereby the maximum spatial frequency transferred by the system is increased by a factor of two. In our contribution we will present a simulation study showing that ISTEM generally allows extending the point resolution of CTEM imaging beyond the diffraction limit. We will also reveal by image simulation that this new TEM mode is more robust against chromatic aberration, which allows overcoming the conventional information limit of a microscope. These calculations are confirmed by experimental data for GaN along the [1-100] and [11-20] directions taken on our TITAN 80/300 microscope with a conventional information limit of 80 pm, where we resolved Ga and N columns at a distance of 63 pm. Thus, ISTEM combines advantages of STEM imaging such as improved point resolution with advantages of the CTEM imaging mode while avoiding disadvantages of STEM. In STEM, the precision for determining atom column positions is limited by scan noise which is caused by errors in positioning the electron probe, and the resolution is influenced by the finite source size effect. In contrast, ISTEM images do neither suffer from scan noise nor is the image resolution influenced by the finite source size. Furthermore, we will show by theoretical considerations that ISTEM is independent of lens aberrations of the probe forming system, but only depends on the radius of the probe forming aperture. Due to the principle of reciprocity, ISTEM can be made equivalent to annular bright field STEM using a ring-shaped condenser aperture, promising ultra-high resolution imaging of light elements by avoiding scan noise and source size effect.
ZZ5: Poster Session: Materials Information Using Novel Techniques in Electron Microscopy
Tuesday PM, April 07, 2015
Marriott Marquis, Yerba Buena Level, Salon 7/8/9
9:00 AM - ZZ5.01
High-Throughput Characterization of Nanoparticles by TEM
Claude Dufresne 1
1Scienion US Inc Monmouth Junction United StatesShow Abstract
Analysis of nanoparticles by TEM is a very useful characterization method. However, by nature of TEM instrument design placing sample grids under high vacuum, the number of samples that can be looked at in a given time period is very limited. Indeed, for each sample placed on a TEM grid, the TEM has to undergo a complete cycle of losing and re-establishing vacuum conditions. Having the capability to insert multiple samples at once inside the TEM and then acquiring all images without breaking vacuum for each one, would result in a tremendous increase in the number of samples that can be analyzed per hour.
For over 10 years, SCIENION&’s picoliter liquid dispensing technology has been used to deposit arrays of different sample solutions onto a wide variety of substrates. Applying this well-proven technology to dispense multiple liquid samples onto a single TEM grid is an obvious extension.
In this presentation, we illustrate the process by which one can deposit up to 100 different samples onto a single 3 mm TEM grid&’s 1 x 1 mm window. In summary, analytical suspensions of nanoparticles are loaded in the instrument using a 96-well plate. For each sample, the instrument aspirates a small aliquot of a few microliters, and dispenses 50-100 picoliters onto a precise, indexed location inside the TEM window. The process is repeated until all samples have been deposited inside the grid in different locations. The most suitable TEM windows have to be selected according to the nature of the nanoparticles to be investigated. The hydrophilicity of the window material is important to allow high quality spot formation as well as homogeneous distribution of the nanoparticles inside each spot.
9:00 AM - ZZ5.02
Angle-Resolved Cathodoluminescence Polarimetry on Bulk and Nanostructured Silicon
Benjamin Brenny 1 Toon Coenen 1 Clara Osorio 1 Femius Koenderink 1 Albert Polman 1
1FOM Institute AMOLF Amsterdam NetherlandsShow Abstract
We use angle- and polarization-resolved cathodoluminescence (CL) imaging spectroscopy to study coherent and incoherent radiation processes in single-crystalline silicon wafers and silicon photonic crystals. Samples are excited using a 30 keV electron beam, and the emitted radiation is collected using an aluminium half-parabolic mirror that is placed between the electron column and the sample. A micromanipulation stage allows accurate alignment of the mirror focus with the electron beam spot. Angle-resolved data are collected using a two-dimensional CCD imaging camera placed in the Fourier plane of the imaging optics, in combination with band-pass filters. Polarization is analysed by rotating a quarter-wave plate in combination with a polarizer in the emitted light beam.
We first analyse the CL emission from a single-crystal Si(100) wafer. The angular CL distribution is composed of a dipolar distribution due to transition radiation and a Lambertian emission profile resulting from the radiative recombination of electron-hole pairs inside the Si wafer. We find that incoherent radiative emission accounts for 25% of the collected light at a wavelength of 400 nm, increasing to 85% at 900 nm.
Next, we determine the full polarization state of the emitted CL in the 600-900 nm spectral range by performing measurements of the angular distribution at six different combined orientations of the quarter-wave plate and polarizer. We separate the polarized and unpolarized components of the emission from bulk Si and reconstruct the polarization vector at each emission angle. The polarizing effect of the Si/air interface on the CL emission generated inside the wafer is clearly observed.
Finally, we introduce the use of a scanning pinhole inside the optical beam path which enables measurements that combine both high angular and spectral resolution, allowing for analysis of strongly dispersive geometries. We analyze the spatially-resolved angular and spectral CL emission profiles from photonic crystal waveguides and cavities that we make using electron-beam lithography using a silicon-on-insulator wafer. From the data, we construct the photonic crystal bandstructure and determine the modal field distributions in the photonic cavities in the 1300-1700 nm spectral range.
9:00 AM - ZZ5.03
3D Characterization Using Electron Tomography with a Parameter-Less Data Processing Revealing Nanometer-Sized Erbium Clusters in Porous Silicon
Tony Printemps 2 Guido Mula 1 Pierre Bleuet 2 Vincent Delaye 2 Adeline Grenier 2 Nicolas Bernier 2 Lionel Herve 2
1Universitagrave; di Cagliari Monserrato Italy2CEA Grenoble FranceShow Abstract
Porous silicon has presented a lot of interest since its discovery in 1956, thanks to a wide range of applications in electronics, optoelectronics, photonics, chemical sensors, biosensors, etc. Many different geometries and morphologies of porous silicon can be obtained, depending on the fabrication parameters. Erbium doped porous silicon is particularly interesting for its luminescent properties at room temperature and could be a relevant material for efficient and cost-effective silicon-based optoelectronic devices. To characterize the geometries and size of pores of a few nanometers as well as the erbium localization, Electron Tomography (ET) is a key technique.
ET is a non-invasive technique to perform 3D imaging of objects of a few hundreds nanometers with a spatial resolution of about one nanometer. A TEM (Transmission Electron Microscope) is used in scanning HAADF (High Angle Annular Dark Field) mode to acquire 2D images of the object under different tilt angles. After careful alignment of the 2D image stack, one can reconstruct the 3D object using analytical or algebraic algorithms such as SIRT (Simultaneously Iterative Reconstruction Technique). Simulations show that SIRT gives almost perfect reconstructions with 180 projections in a 180° angular range. In practice, the resolution of the 3D reconstruction is far from identical to that of the 2D images. Differences between simulations and practice can be explained mostly by the misalignment of the image stack and the presence of noise. Here we propose an automatic alignment and a parameter-less denoising of the projections that help to enhance the resolution and the quality of the 3D reconstruction. This technique has been applied to erbium-doped porous silicon samples. It shows high reconstruction quality and high reliability to perform an efficient segmentation and quantitative analysis of the 3D structures and geometry of the pores. Compared to state of the art complex reconstruction algorithms such as Total Variation Minimization (TVM) based algorithms and Discrete Algebraic Reconstruction Technique (DART), the complete procedure used has the great advantage to be totally parameter-less, i.e. user-independent, and much faster than TVM or DART.
The principle of the technique and its comparison to classical alignment and reconstruction methods will be discussed as well as the quantitative analysis of the 3D reconstruction of erbium-doped porous silicon sample. The 3D reconstruction reveals clusters of a few nanometers, with localization depending on the curvature of the nearest pores surface. The surface curvature dependence is quantitatively demonstrated with a statistical determination of the surface curvature next to the clusters.
9:00 AM - ZZ5.04
Oxygen Deficiency and Strain: Effect on the Structure of LaNiO3 Thin Films
Luis Lopez-Conesa 1 Jose Manuel Rebled 1 2 David Pesquera 2 Florencio Sanchez 2 Nico Dix 2 Josep Fontcuberta 2 Cesar Magen 3 Sonia Estrade 1 Francesca Peiroacute; 1
1University of Barcelona Barcelona Spain2Institut de Ciencia dels Materials de Barcelona (ICMAB) Barcelona Spain3Univ de Zaragoza Zaragoza SpainShow Abstract
LaNiO3 (LNO) is a perovskite of great importance in complex oxide electronics. Its low resistivity at room temperature and high chemical stability make it an ideal electrode candidate for many applications in complex oxide-based devices. Strain, oxygen vacancies and their mutual interplay are key aspects to understand the transport properties of these oxides, since they might affect the Ni-O hybridization. In this study, we perform a thorough analysis of these aspects with high spatial resolution TEM.
We have studied LNO thin films of different thicknesses (14 nm and 35 nm) grown on several substrates that allow studying a wide range of compressive (LAO and YAO) and tensile (LSAT and STO) strain states. Aberration corrected HRTEM, HAADF-STEM, atomic resolution EELS mapping, electron diffraction and image simulation studies have been carried out. Strain states in the films have been studied by Geometric Phase Analysis (GPA) of the high-resolution images.
The presence of an oxygen deficient monoclinic phase has been detected in the LNO strained films. This perovskite-related superstructure occurs when oxygen vacancies order along a given crystallographic direction, consisting in the loss of the two apical oxygen atoms in the Ni octahedra for alternating columns of octahedra and square planes along the c axis. Different crystallographic orientations were prepared for TEM observation. Electron diffraction patterns, contrast modulation in HRTEM images and Z contrast in HAADF images are consistent with this vacancy ordering. Image simulations (both HRTEM and HAADF) support these findings. We report on the effect of the strain state of the film and the film thickness on the occurrence and orientation of the monoclinic superstructure.
9:00 AM - ZZ5.05
In-Situ Transmission Electron Microscopy Study on Ferroelectric Nanodomains
Yu Deng 1 Chengping Zhang 1
1Nanjing University Nanjing ChinaShow Abstract
Nanodomains in ferroelectrics are attractive due to their applications on the ultra-small electric, optical, actuator devices and nonvolatile memory. Recently, the in-situ nanodomain investigations by the Scanning Probe Microscope (SPM) and the sub-atomic resolution Transmission Electron Microscopy (TEM) achieved great successes, revealing numerous novel ferroelectric nanodomain structures such as the self-similar nested bundles, the nanovortex array and the stabilized charged domains. In this work we improved an in-situ system in TEM to study the nanodomain structures in the free-standing nanopillars. With Cs-corrected TEM, different types of nanodomain structures were studied in three dimensions. And the unique properties of the nanodomain structures are discussed as well.
9:00 AM - ZZ5.06
Atomic Level Observation of Au-Cu Core-Shell Nanoparticles Growth Using Graphene Liquid Cell
Sang Yun Kim 1 2 Jong Min Yuk 1 2 Myoungho Jeong 1 2 Hyeon Kook Seo 1 2 Jeong Yong Lee 1 2
1Korea Advanced Institute of Science and Technology (KAIST) Daejeon Korea (the Republic of)2Institute for Basic Science Dajeon Korea (the Republic of)Show Abstract
General transmission electron microscopy (TEM) is not suitable for observing liquid specimen due to high vacuum environment in a TEM. To overcome this problem, previous studies using several type of liquid cell with Si3N4 viewing window. However, thick thickness Si3N4 layers and liquid surrounding the sample are main challenges for atomic-resolution imaging. A novel graphene liquid cell that encapsulating a liquid film between two layers of graphene is expected that could enable atomic-resolution observation of liquid specimens including chemical reaction or nucleation and growth due to outstanding characteristics of graphene. Graphene, a one-atom-thick planar sheet of carbon atoms, can provide a high contrast images in a TEM and sealing any type of material including liquid and gas phase materials because of high flexibility. In order to investigate nucleation and growth behavior of core-shell nanoparticle, we employ the graphene liquid cell. In bimetallic nanoparticles, composed of two different metal elements, the particle size and the structure of bimetallic nanoparticles can affect their catalytic properties including activity and selectivity of catalysts. So it is important to understand growth mechanism of bimetallic nanoparticles. We observed the growth of Cu shells on Au nanoparticles in the TEM using the graphene liquid cell. Graphene liquid cell is prepared by encapsulating Au nanoparticles as templates and Cu growth solution between two graphene layers. Cu nanoparticle growth in the TEM employed the reduction of Cu2+ ion via electron beam illumination. The Au seed nanoparticles and the stock Cu growth solution were observed successfully trapped between the two graphene layers. The growth of Cu shells on Au nanoparticle was initiated by electron beam irradiation and size and shape of the synthesized Au-Cu core-shell nanoparticles are determined by Au seed nanoparticles. We have observed the formation process of Cu shells on Au nanoparticle with atomic-resolution using graphene liquid cell. We speculate that this method can be applied to other bimetallic nanoparticles in order to design the desired bimetallic nanoparticle.
9:00 AM - ZZ5.07
Cathodoluminescence as a Technique for the Determination of Dopant Distribution in Europium-Doped Hydroxyapatite
Luz Zavala 2 Manuel Herrera 2 1 Olivia A. Graeve 1 2
1UCSD San Diego United States2UNAM Ensenada MexicoShow Abstract
Hydroxyapatite [Ca10(PO4)6(OH)2, HAp] is one of the primary constituents in hard biological tissues and in its synthetic form has significant potential uses in the medical industry, mainly for its applications in bone regeneration. The apatite lattice is very tolerant of substitutions, and many kinds of cations can be introduced into the lattice. In particular, doping with rare-earth ions is of great interest because the material can be used as a fluorescent probe in the medical industry. Cathodoluminescense (CL) is a very efficient technique to study the luminescent properties of several materials locally. When adapted in an SEM, it permits one to obtain luminescent properties at great magnifications, sometimes overlooked in bulk measurements. In this work, we present an in-depth analysis of the CL response of europium-doped hydroxyapatite powders in order to demonstrate the dopant distribution in the host. Samples were synthesized using combustion synthesis at different pH values and the same amount of Eu precursor. CL spectra show UV-blue emissions between 350 - 440 nm attributed to transition 4f65d1-4f7(8S7/2) of the Eu2+, and orange-red bands in the range 575-700 nm generated by transitions 5D0 → 7FJ of the Eu3+. Monochromatic CL images acquired at 425 and 616 nm show inhomogeneity in the spatial distribution of Eu2+ and Eu3+ in the samples, revealing bright regions at the edge of the HAp:Eu microstructures for the Eu3+ emission. XPS measurements confirm the presence of Eu+3 and Eu+2 ions in the samples, with a concentration ratio Eu+2/Eu+3 of about 0.22 that corresponds to a preferential incorporation of Eu+3 on the surface.
9:00 AM - ZZ5.08
Combined EELS and Cathodoluminescence Analysis in a STEM Microscope of GaN / InGaN Quantum Wells for LED Applications
Paolo Longo 1 David J Stowe 1 Ray Twesten 1
1Gatan Inc Pleasanton United StatesShow Abstract
The correlation between a material&’s luminescence properties and its nanoscale morphology, microstructure and local chemistry offers great benefit in the understanding of many technologically important materials and devices. This has encouraged a growing interest in performing cathodoluminescence (CL) microscopy at high spatial resolution in a STEM microscope . Here, we use combined electron energy loss spectroscopy (EELS) and CL analysis of the GaN / InGaN quantum well (MQW) from a light emitting diode (LED) to investigate the role of In clustering in luminescence efficiency; sub-nanometer compositional information is correlated with the luminescence from individual quantum wells with the MQW.
III-nitride semiconductors are technologically important materials with GaN / InGaN MQWs being the source of light emission in current generation blue and white LEDs. However, efficient white LEDs based entirely of III-nitride semiconductors remain elusive due to poor efficiency at green emission wavelengths, the so-called ‘green-droop&’. The reason for low efficiencies at high In content is not well understood; auger electrons fluctuations in quantum well and In composition are two of the many proposed mechanisms. Thus, understanding how the structure, composition and luminescence (intensity and emission wavelength) of MQW structures are correlated is ultimately very important for improving device performance.
For the results of this paper, compositional information was obtained from sub-nanometer scale EELS analysis using means of MLLS fitting to extract the composition and the local luminescence was measured simulatnously using CL. The CL light was acquired using miniature elliptical mirrors (solid angle of about 7.3 sr) integrated into the tip of a conventional cryogenic TEM holder. Light is coupled out of the holder through two optical fibres to an optical spectrometer fitted with a PMT and CCD detectors. This combined EELS / CL system offers the advantage of the best in spectral resolution (up to 4 meV), spatial resolution analysis and sensitivity to microstructural changes. Simultaneous EELS / CL data was collected with the sample at -171C minimizing the influence of the electron beam on the sample and increasing the spatial resolution of the Cl data as result of the enhanced rate of radiative recombination within the QWs. The analysis was carried out across the GaN / InGaN MQWs and superlattice layers where each layer is just a couple of nanometers wide. Variations of the luminescence quantum efficiency by more than an order of magnitude was observed between regions separated by only a few tens of nanometers and free extended defects; we analyse how the composition measured by EELS affects the luminescence.
 Zagonel L. F., Mazzucco S., Tence&’ M., March K., Bernard R., Laslier B., Jacopin G., Tchernycheva M., Rigutti L., Julien F. H., Songmuang R. and Kociak M., Nanoletters 11, 2011, 568
9:00 AM - ZZ5.10
Nanoscale-Spatially Resolved Cathodoluminescence for Investigating Eu2+ and Dy3+ Co-Doped Boron-Incorporated Strontium Aluminate Long Persistence Phosphors
Cleva W. Ow-Yang 2 1 Guliz Inan Akmehmet 2 1 Laura Bocher 3 Mathieu Kociak 3 Saso Sturm 4
1Sabanci University Istanbul Turkey2Sabanci University Istanbul Turkey3CNRS UMR8502 Orsay Cedex France4Jozef Stefan Institute Ljubljana SloveniaShow Abstract
Long persistence SAEDB phosphors consist of luminescent rare earth atoms, i.e. Dy2+ and Eu3+, embedded in a B-incorporated Sr4Al14O25 matrix. We have previously demonstrated that the addition of boron into the strontium aluminate system dramatically extends the persistence duration from several minutes to more than 8 hours . However, the exact mechanism by which B extends afterglow is still unclear, and the potential for such materials to be exploited in energy-efficiency applications motivated our study.
As a key step in a broader effort to understand the mechanisms of persistence in phosphors, we combined electron-based spectroscopy techniques by means of cathodoluminescence (CL) and electron energy-loss spectroscopy (EELS) in a dedicated scanning transmission electron microscope (STEM) . This unique approach enables us to probe locally their optical and chemical heterogeneities down to the nanoscale, and therefore to correlate spatially the cation homogeneity and luminescence uniformity in SAEDB phases. Because the 4f65d1 agrave; 4f7 transition of Eu2+ engenders luminescence in the visible light spectrum, we probed locally the spatial distribution of this luminescence, after excitation by energy absorbed from the probe electrons. We could then map the B chemical distribution in the oxide matrix, by probing the B-K core-loss edge by EEL spectroscopy.
The particles studied were synthesized by a modified Pechini process, yielding powders of Sr4Al14O25 doped with 1 mol% Eu2+, 1 mol% Dy3+, and 7 mol% B (Sr4A7EDB). The crystal structure, as well as the cationic stoichiometry, was first characterized by means of XRD, high-resolution TEM imaging, and ICP analysis. While a 2-D CL map in the spectral range of 413-436 nm appeared relatively homogeneous, a CL-filtered-map in the 277-300 nm spectral range was not uniform. A CL peak centered at 288 nm with a FWHM of ~65 nm was precisely localized on one side of the probed particle. This strong cathodoluminescence feature is consistent with the strong absorption of Sr4A7EDB in the region below 350 nm, with absorption peaks at 250nm, 288 nm, and 350 nm. In this spectral region, the control specimen, which did not contain boron, absorbed with much lower intensity, and no sharp features above the weaker background absorption. We thus report a correlation between luminescence and the spatial distribution of boron in Eu2+ and Dy3+ co-doped boron-incorporated strontium aluminate (SAEDB) phosphors.
 M.G. Eskin, Sabanci University, M.Sc. Thesis (2011).
 L. Zagonel et al., Nanoletters, 11 (2011) 568
Acknowledgement: The research leading to these results has received funding from the European Union Seventh Framework Programme under Grant Agreement 312483 - ESTEEM2 (Integrated Infrastructure Initiative - I3)
9:00 AM - ZZ5.11
Structure and Chemical Bonding of Thermoelectric Half-Heusler Alloys Studied by Transmission Electron Microscopy and Electron Energy Loss Spectroscopy
Raluca Tofan 1 Cristina Echevarria 3 Anette Eleonora Gunnaes 1 2 Oystein Prytz 1 2
1Centre for Materials Science and Nanotechnology, University of Oslo Oslo Norway2University of Oslo Oslo Norway3Institute for Energy Technology Kjeller NorwayShow Abstract
Thermoelectric materials have the capability to directly generate power using the Seebeck effect or refrigerate using the Peltier effect, without the need of additional moving parts. The figure of merit, ZT, defines the efficiency of thermoelectric materials: ZT=(S2σ/k)T, where S is the Seebeck coefficient, σ is the electrical conductivity, k is the thermal conductivity and T is the absolute temperature at which the properties are measured . For the thermoelectric device to be competitive, an average value of the ZT larger than 1 is needed within the application range - usually from room temperature to 900°C. Achieving this goal requires a detailed understanding of the atomic and electronic structure of the materials involved.
The Half-Heusler alloys are a promising group of materials for thermoelectric applications. They are ternary semiconductor or metallic materials, having the stoichiometry XYZ (1:1:1), with X and Y transition metals (e.g., X=Ti, Zr, Hf and Y=Ni, Co) and Z a metal or metalloid (Sn, Sb). The electronic structure, and charge carrier concentration and scattering may be manipulated by substitution on three crystallographic sites in order to enhance the thermoelectric properties.
In this contribution, we study a series of Half-Heusler compounds with the starting composition TiNiSn, but where we allow the following substitutions: Ti with Zr, Hf; Ni with Co; and Sn with Sb. The crystal structure and the chemical composition are investigated with electron diffraction and Energy Dispersive X-ray Spectroscopy analyses, while the transition metal oxidation state and d-state occupancy are tracked by Electron Energy Loss Spectroscopy .
 G. S. Nolas, J. Sharp and H. Goldsmid, Thermoelectrics: Basic Principles and New Materials Developments, Springer, New York, 2001;
 D. Rowe, Thermoelectrics Handbook: Macro to Nano, CRC Press, Boca Raton, 2006;
 D. H. Pearson, C. C. Ahn and B. Fultz, PRB Vol 47 (1993);
 Y. Shao, C. Maunders, D. Rossouw, T. Kolodiazhnyi, G. A. Botton, Ultramicroscopy Vol 110 (2010).
9:00 AM - ZZ5.12
High Energy Resolution EELS on ZnO/Cu2O Heterostructures
Cecilie S. Granerod 1 2 Phuong Dan Nguyen 1 2 Wei Zhan 1 2 Ola Nilsen 3 Edouard Monakhov 1 2 Anette Eleonora Gunnaes 1 2 Oystein Prytz 1 2
1University of Oslo Oslo Norway2University of Oslo Oslo Norway3University of Oslo Oslo NorwayShow Abstract
In the search for new solar cells with higher efficiencies and lower production costs, thin films have shown great potential and could eventually replace silicon. As the films are on the nanometer scale, and the interface is strongly dependent on the processing methods, the electronic properties across the interface become important.
In this project, we study interfaces in different types of ZnO/Cu2O heterostructures. Films of Cu2O are deposited onto ZnO substrates by sputtering, and TEM samples are prepared by cutting, grinding and polishing. The structure and composition of the heterostructure interfaces are studied using a probe-corrected and monochromated FEI Titan 60-300 STEM. Furthermore, using high energy resolution monochromated EELS we investigate the dielectric properties and band gap variations across the interfaces.
The critical voltage of Cerenkov radiation for ZnO is 79 kV, and to avoid this Cerenkov limit the microscope is operated at a high tension of 60 kV. The goal is to measure the band gap close to the interface, an also consider the inelastic delocalization of the electrons  .
 Egerton, R. F., Ultramicroscopy 107 (2007) 575-586
 Stöger-Pollach, M., Ultramicroscopy 145 (2014) 98-104
9:00 AM - ZZ5.14
Combining STEM Orientation Imaging and STEM EELS to Statistically Correlate Grain Boundary Orientation and Composition in Polycrystalline Doped CeO2 Electrolytes
William John Bowman 1 Amith Darbal 3 Peter A. Crozier 2
1Arizona State University Tempe United States2Arizona State University Tempe United States3AppFive LLC Tempe United StatesShow Abstract
CeO2 (ceria) doped with aliovalent cations such as Gd3+ and Sm3+ is a common solid state O2- conductor in solid oxide fuel cell (SOFC) electrolyte research due to its high ionic conductivity at low and intermediate temperatures (300 °C - 550 °C) . However, at such temperatures the resistance contribution from grain boundaries in polycrystalline electrolytes also becomes considerable due to an intrinsic electrostatic space charge potential barrier emanating from grain boundary cores. This argument generally assumes grain boundaries have similar properties and ignores the potential differences in grain boundary structure . And because atomic structure is thought to be a principal component of the origin of the grain boundary space charge potential , the authors hypothesize that because grain boundary structures vary, their electrostatic potentials vary as well, manifesting as variation in other grain boundary properties including composition and electrical conductivity. In practice, there may be many different types of grain boundaries in a polycrystalline ceramic and it is important to provide statistical context to the atomic resolution information derived from TEM. In this contribution we employ orientation imaging performed with a nanometer-sized probe in the scanning transmission electron microscope (STEM) to determine the character of hundreds of grain boundaries. This data provides a rapid statistical distribution of the grain boundary character which can then be used to guide the atomic resolution structural and compositional analysis by imaging and electron energy-loss spectroscopy. All measurements were performed on a JEOL ARM 200F aberration-corrected TEM/STEM equipped with an ASTAR precession nanodiffraction system. Data are presented on the grain boundary distribution and statistical prevalence, correlated with point defect segregation at grain boundaries in a polycrystalline Gd/Pr doubly-doped ceria specimen. Preliminary data shows that the dopant segregation varies with grain boundary angle.
1. Fergus, J., et al., eds. Solid oxide fuel cells: materials properties and performance. CRC Press, 2008.
2. N. Shibata , F. Oba , T. Yamamoto, Y. Ikuhara. Structure, energy and solute segregation behaviour of  symmetric tilt grain boundaries in yttria-stabilized cubic zirconia, Philosophical Magazine84:23 2381 (2004).
3. Tschöpe, A. Interface Defect Chemistry and Effective Conductivity in Polycrystalline Cerium Oxide. Journal of Electroceramics14 5-23 (2005).
4. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1311230, and NSF DMR-1308085. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.
ZZ1: Adding the Third Dimension
Tuesday AM, April 07, 2015
Marriott Marquis, Yerba Buena Level, Nob Hill C/D
9:30 AM - *ZZ1.01
High Resolution Imaging of Nanomaterials in 3 Dimensions
Sara Bals 1 Bart Goris 1 Thomas Altantzis 1 Daniele Zanaga 1 Annick De Bakcer 1 Stuart Turner 1 Sandra Van Aert 1 Bert Freitag 2 Gustaaf Van Tendeloo 1
1EMAT-University of Antwerp Antwerp Belgium2FEI Company Eindhoven NetherlandsShow Abstract
Matter is a three-dimensional (3D) agglomeration of atoms. The properties of materials are determined by the positions of the atoms, their chemical nature and the bonding between them. Therefore, reaching atomic resolution in 3D has been the ultimate goal in the field of electron tomography for many years.
In addition to the use of discrete tomography [1-3], one of the possibilities to perform electron tomography with atomic resolution is by applying reconstruction algorithms based on compressive sensing. The methodology was applied to high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images acquired from Au nanorods. In the final 3D reconstruction, the Au crystal lattice was reproduced without using prior knowledge on the atomic structure . Going further than determining the positions of atoms is the aim to determine the type of individual atoms in hetero-nanoparticles. Again using a combination of HAADF-STEM and compressive sensing, we were able to distinguish individual Ag from Au atoms in core-shell Au@Ag nanorods, even at the metal-metal interface .
Also energy dispersive X-ray (EDX) mapping can be combined with electron tomography and the use of the Super-X system, consisting of 4 EDX detectors symmetrically arranged with respect to the sample is hereby very beneficial. EDX tomography was applied to obtain qualitative information concerning a galvanic replacement reaction in AuAg nanoparticles and to investigate the 3D composition of Fe and Co in nanodumbbells [6,7]. Quantification 3D EDX results can be considered as the next crucial step.
Finally, by combining electron tomography with electron energy-loss spectroscopy at high energy resolution, we were able to determine the valency of the Ce ions in CeO2-x in 3D. These unique experiments revealed a clear facet-dependent reduction shell at the surface of ceria nanoparticles, invisible to modern high resolution TEM structural imaging techniques .
We kindly acknowledge Prof. L. M. Liz-Marzán and Prof. K. Soulantica for the provision of the samples.
 S. Van Aert, K. J. Batenburg, M. D. Rossell, R. Erni, G. Van Tendeloo, Nature 470 (2011) 374
 S. Bals, M. Casavola, M. A. van Huis, S. Van Aert, K. J. Batenburg, G. Van Tendeloo, D. Vanmaekelbergh, Nano Lett. 11 (2012) 3420
 B. Goris, S. Bals, W. Van den Broek, E. Carbo-Argibay, S. Gomez-Grana, L. M. Liz-Marzan, G. Van Tendeloo, Nature Mater. 11 (2012) 930
 B. Goris, A. De Backer, S. Van Aert, S. Go#769;mez-Gran#771;a, L. M. Liz-Marzán, G. Van Tendeloo, S. Bals, Nano Lett. 13 (2013) 4236
 N.Liakakos, Ch. Gatel, Th. Blon, Th. Altantzis, S. Lentijo-Mozo, C. Garcia-Marcelot, L.-M. Lacroix, M. Respaud, S. Bals, G. Van Tendeloo, K. Soulantica Nano Lett.14 (2014) 2747
 B. Goris, L. Polavarapu, S. Bals, G. Van Tendeloo, L. M. Liz-Marzán Nano Lett. 14 (2014) 3220
10:00 AM - *ZZ1.02
Scanning Confocal Electron Energy Loss Microscopy (SCEELM) for High-Throughput 3-D Spectroscopic Imaging
Huolin L. Xin 1
1Brookhaven National Lab Upton United StatesShow Abstract
The ever increasing complexity of the 3-D architectures of modern nanodevices drives the demands to image nanoscale features in 3-D. ADF-STEM tilt-series tomography can reconstruct materials with nanometer and even atomic-scale resolution; however it often requires days to align and reconstruct the tomograms. With the development of aberration correctors where the depth of focus has been reduced to the sub-10nm region, 3-D imaging by depth sectioning becomes a possibility. It potentially allows for a reconstruction of nanomaterials by simply recording a through-focal series. Unfortunately, it has been demonstrated that both ADF-STEM and bright-field scanning confocal electron microscopy (BF-SCEM) have cones of missing information that produce excessive elongation artifacts in the resulting reconstructions. Here, we explore the inelastic counterpart of BF-SCEM—scanning confocal electron energy loss microscopy (SCEELM). This technique is free of the missing-information cone and resulting elongation artifacts. In a microscope without post-specimen chromatic aberration (Cc) correction, this method has a dose efficiency comparable to that of ADF-STEM depth sectioning if valence-loss signals are used. However, the efficiency can be increased by a factor of 10-100 with post-specimen Cc correction by parallel acquisition of SCEELM signals in spectroscopy mode. It can potentially enable a rapid and reliable 3-D reconstruction of materials with sub-10 nanometer depth resolution in Cc-corrected confocal TEMs1,2,3,4.
1 HLX is supported by the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.
2 Scanning Confocal Electron Energy-Loss Microscopy Using Valence-Loss Signals, H. L. Xin*et al,Microscopy and Microanalysis, 19, 1036-49 (2013)
3Three-dimensional imaging in aberration-corrected electron microscopes, H. L. Xin* and D. A. Muller, Microsc. and Microanal. 16, 445 (2010)
4Aberration-corrected ADF-STEM depth sectioning and prospects for reliable 3D imaging in S/TEM, H. L. Xin* and D. A. Muller, J. Electron Microsc. 58, 157 (2009)
10:30 AM - ZZ1.03
Direct Observation of Interfacial Au Atoms Using STEM Depth Sectioning
Wenpei Gao 1 Shankar Sivaramakrishnan 1 Jianguo Wen 1 Jian-Min Zuo 1
1University of Illinois at Urbana-Champaign Urbana United StatesShow Abstract
Interfacial atoms located between metal nanoparticles and supports are proposed active sites, because of their distinct physical and chemical properties [1,2]. However, the atomistic details are difficult to resolve in the interface; the lack of knowledge has been a major obstacle toward unraveling their roles in chemical transformations. Here we report the detection of interfacial Au atoms on the rutile (TiO2) (110) surfaces thanks to the improved spatial resolution and depth of focus brought by aberration corrected scanning transmission electron microscopy (STEM).
Au on TiO2 is selected because it shows remarkable catalytic activity as the sizes of Au particles reduce to ~3 nm or below, for the oxidation of CO. The Au catalysts are typically prepared by Au precipitation on titania support, followed by calcination in air or reduction under H2 at elevated temperatures. Extensive study has been done concerning the mechanism of CO oxidation catalyzed by gold and the role of interfacial gold atoms. However, direct observation of interfacial Au atoms has not been reported before. A major obstacle is the TiO2 support surface, which is often highly complex, undetermined and varies at the nanometer scale. With atomic resolution images recorded at different focuses along TiO2 , we have reconstructed the 3D intensity profiles of interfacial atoms. The results lend to direct support to the presence of interfacial Au atoms, embedded in a single interfacial layer.
The experiment started with forming epitaxial Au nanocrystals (NCs) on rutile (110) by e-beam evaporation deposition followed by annealing in air. The sizes of the Au NCs ranged from 3.5 to 12 nm in width depending upon the annealing conditions. The samples are observed by aberration corrected (AC) scanning transmission electron microscopy (STEM) using the JEOL 2200FS installed at the Center for Microscopy and Microanalysis, Frederick Seitz Materials Research Laboratory, at 200kV. The microscope is capable of resolving atoms separated by 1 Å.
With the interface imaged along TiO2  and , results show that a single interfacial layer forms between Au NCs and the TiO2 (110) surface, with Au atoms embedded inside the layer. The interfacial Au atoms are located in 3D by depth sectioning, and they are separated from Ti-O according to their intensities. A detailed description of interactions between Au NCs and the TiO2 support is made possible from the results.
1. Akita, T., M. Kohyama, and M. Haruta, Electron Microscopy Study of Gold Nanoparticles Deposited on Transition Metal Oxides. Accounts of Chemical Research, 2013. 46(8): p. 1773-1782.
2. Widmann, D. and R.J. Behm, Active Oxygen on a Au/TiO2 Catalyst: Formation, Stability, and CO Oxidation Activity. Angewandte Chemie International Edition, 2011. 50(43): p. 10241-10245.
11:15 AM - ZZ1.04
Exploring the 3D Crystal Structure by Electron Diffraction Tomography
Arnaud Mayence 1 German Salazar-Alvarez 1 Lennart Bergstroem 1 Peter Oleynikov 1
1Stockholm University Stockholm SwedenShow Abstract
Solving the crystal structure of a material using X-ray based techniques is not often an easy task, especially when dealing with nanocrystals. Recent advances in electron microscopy have eased the way to explore the three-dimensional structure of a material using novel TEM-based methods. Three-dimensional electron diffraction tomography (3D EDT) has been recently developed to simplify the electron diffraction data collection process. The program-controlled TEM-based technique is based on fast 3D reciprocal space fine scanning allowing subsequent reconstruction of high resolution reciprocal space volume1. The 3D data set can be further used for the unit cell determination, quantitative intensities extraction and ab initio structure solution. The main advantage is that the 3D electron diffraction data set can be acquired on any randomly oriented crystal unlike the time-consuming conventional electron diffraction acquisition method.
We demonstrate how the 3D EDT technique can be used for fast automated acquisition and processing of a 3D electron diffraction data set in order to solve the crystal structure of any individual sub-micrometer crystals2 or nanocrystals3 on the atomic scale. We also show how the use of 3D EDT can be extended, using small-angle mode, to probe mesoscopic structures such as self-assembled nanoparticle arrays4. This novel technique opens new possibilities to investigate not only challenging inorganic materials but perhaps also a wide range of organic structures.
1. M. Gemmi and P. Oleynikov, Z. Krist., 2013, 228, 51-58.
2. D. Xu, Y. Ma, Z. Jing, L. Han, B. Singh, J. Feng, X. Shen, F. Cao, P. Oleynikov, H. Sun, O. Terasaki, and S. Che, Nat. Commun., 2014, 5, 4262.
3. A. Mayence, J. R. G. Navarro, Y. Ma, O. Terasaki, L. Bergström, and P. Oleynikov, Inorg. Chem., 2014, 53, 5067-72.
4. A. Mayence, D. Wang, G. Salazar-Alvarez, P. Oleynikov, and L. Bergström, Nanoscale, 2014.
11:30 AM - *ZZ1.05
Spectroscopic and Crystallographic Electron Tomography - Challenges and Opportunities for Multi-Dimensional Electron Microscopy
Paul Anthony Midgley 1
1University of Cambridge Cambridge United KingdomShow Abstract
Scanning transmission electron microscopy (STEM) high angle annular dark field (HAADF) imaging has become popular for materials electron tomography for a number of reasons: Firstly image contrast is easily interpreted and the intensity varies monotonically with thickness (at least for reasonable mass-thickness levels). Secondly, HAADF signal is sensitive to atomic number and provides a measure of the local composition. Thirdly, and of importance to this paper, it can be combined easily with analytical techniques such as energy-dispersive xray spectroscopy (EDS), electron energy loss spectroscopy (EELS), and electron diffraction.
When EDS or EELS is combined with tomography, after suitable reconstruction, spectral information is available at every 3D real space location (voxel). Many modern microscopes are now fitted with large solid angle x-ray detectors and when symmetrically disposed around the optic axis offer an efficient means to record EDS spectrum-images as a function of tilt to build up a 4D data set. We have investigated the best use of such detectors, taking into account shadowing and absorption and we will present examples of 3D compositional maps from a number of materials systems. In a similar way, EELS and tomography can be combined to enable 3D compositional maps to be reconstructed (using core loss data) and 3D optical / dielectric maps (using low loss spectra). We will illustrate both but concentrate on the latter where, for example, a 3D imaging technique has been developed to visualise the 3D excitation of localised surface plasmons.
It is also possible to combine tomography with diffraction to enable 3D orientation data to be acquired at each 3D real space position. Scanning precession electron tomography (SPET) uses a scanned beam to record a precession electron diffraction (PED) pattern at every real space pixel, forming a 4D ‘diffraction-image&’. By acquiring a tilt series, both real and reciprocal spaces can be reconstructed for every phase in the volume of interest.
In each of these techniques, the data acquired is likely to be a mixed signal (with overlapping spectral modes in one, overlapping diffraction patterns in the other). In each case that mixed signal needs to be ‘unmixed&’ in an objective fashion. We now use on a routine basis multivariate statistical analyses and in particular non-negative matrix factorisation (NMF) which decomposes each raw signal into a linear sum of positive signal components (e.g. spectral modes or distinct diffraction patterns) weighted by a positive loading (spatial distribution map). Without data reduction techniques of this kind, processing multi-dimensional data sets become intractable. In addition, we will discuss compressed sensing techniques as a framework for incorporating prior knowledge about the object under investigation. This restricts the number of possible solutions in reconstruction space and minimise artefacts in the final tomogram.
ZZ2: Mapping Fields I
Tuesday AM, April 07, 2015
Marriott Marquis, Yerba Buena Level, Nob Hill C/D
12:00 PM - *ZZ2.01
Recent Progress in Electromagnetic Field Mapping at the Nanoscale Using Electron Holography
Rafal E. Dunin-Borkowski 1 Vadim Migunov 1 Jan Caron 1 Andras Kovacs 1
1Forschungszentrum Juelich Juelich GermanyShow Abstract
Off-axis electron holography is a powerful technique for recording the phase shift of the high-energy electron wave that passes through an electron-transparent specimen in the transmission electron microscope. The phase shift is, in turn, sensitive to the electrostatic potential and magnetic induction in the specimen. Recent developments in the technique have included the use of advanced specimen holders with multiple electrical contacts to study nanoscale working devices, the application of electron holographic tomography to record three-dimensional potentials with nm spatial resolution and the use of ultra-stable transmission electron microscopes to achieve sub-2π/1000-radian phase sensitivity. We are currently working on the application of off-axis electron holography to the measurement of electrostatic potentials and electric fields around electrically-biased atom probe tomography needles. Each experiment typically involves applying a voltage between a needle and a counter-electrode. The recorded phase shift can be analyzed either by fitting the phase distribution to a simulation based on two lines of opposite charge density or by using a model-independent approach that involves contour integration of the phase gradient to determine the charge enclosed within the integration contour. Both approaches often require evaluation of the difference between phase images acquired for two applied voltages, in order to subtract the mean inner potential (and sometimes also the magnetic) contribution to the phase. On the assumption of cylindrical symmetry, the three-dimensional potential and field around such a needle can be determined from the results. We are also working on a model-based approach that can be used to reconstruct the three-dimensional magnetization distribution inside a specimen from a series of phase images recorded using electron holography. In order to develop the technique, we are generating simulated magnetic induction maps by projecting three-dimensional magnetization distributions onto two-dimensional Cartesian grids. We use known analytical solutions for the phase shifts of simple geometrical objects to pre-compute contributions to the phase from individual parts of the grids, in order to simulate phase images of arbitrary three-dimensional objects from any projection direction, with numerical discretization performed in real space in order to avoid artifacts generated by discretization in Fourier space without a significant increase in computating time. This forward simulation approach is used in an iterative model-based algorithm to solve the inverse problem of reconstructing the three-dimensional magnetization distribution in the specimen from a tomographic tilt series of phase images. The use of such a model-based approach avoids many of the artifacts that result from using classical tomographic techniques based on backprojection, as well as allowing additional physical constraints to be incorporated.
12:30 PM - ZZ2.02
A Quantum Mechanical Approach to Electron Picodiffraction Reveals Atomic Electric Fields
Knut Mueller 1 Krause Florian 1 Armand Beche 2 Marco Schowalter 1 Vincent Galioit 4 Stefan Loeffler 3 Johan Verbeeck 2 Josef Zweck 4 Peter Schattschneider 3 Andreas Rosenauer 1
1Universitauml;t Bremen Bremen Germany2EMAT - University of Antwerp Antwerpen Belgium3Vienna University of Technology Vienna Austria4Universitauml;t Regensburg Regensburg GermanyShow Abstract
Contemporary aberration-corrected scanning transmission electron microscopy (STEM) enables to probe material properties at a resolution of 80pm and below. However, mapping of atomic electric fields in nanoelectronics remains a challenge. Progress in this field relies on the differential phase contrast (DPC) technique which uses segmented detectors to detect the field-induced angular deflection of the STEM beam via a shift of the central part of the diffraction pattern (the ronchigram), causing a characteristic asymmetry in opposite segments (Nature Phys. 8, 611 (2012); Ultramicroscopy 2, 251 (1977)). The established interpretation of DPC relies on the assumptions that the ronchigram is homogeneously filled and shifted as a whole.
First we focus on the validity of these assumptions. In simulation and experiment we show that ronchigrams neither exhibit homogeneous intensity even for thinnest specimens (1-5nm), nor are they shifted as a whole. Contrary, the effect of electric fields is a complex redistribution of intensity inside the ronchigram which needs to be captured by pixelated detectors such as CCD cameras.
Second, we present a simple but stringent quantum mechanical interpretation: In recording the 2D intensity distribution in the diffraction pattern, we detect the squared modulus of the specimen exit wave function in momentum space. Hence the intensity I(px,py) in a certain pixel of the CCD is proportional to the probability that the corresponding momentum (px,py) is observed. Thus the centre-of gravity-type summation <p>=int; I(px,py) dpxdpy yields the expectation value <p> for the momentum, independently of the complexity of the diffraction pattern. We demonstrate how the momentum transfer can be related to the electric field convolved with the intensity of the STEM probe in thin specimens. In exploiting Maxwell's equations, we show how our method can pave the way to mapping charge and electron densities.
Third, we present case studies for GaN and SrTiO3 to demonstrate the applicability of this concept. In a simulation study for GaN a set of 80x80 ronchigrams (corresponding to the raster of the STEM probe) has been simulated using the multislice method. These data allow for determining <p>, the electric field, charge- and electron density, and for a comparison with the density functional theory based counterparts. In an experimental study of SrTiO3, a unit cell was rastered with an aberration-corrected STEM probe at 20x20 pixels, and ronchigrams have been recorded for each raster position. Using this 4D data set, we demonstrate the experimental applicability of our method by quantitatively determining both momentum transfer and electric field within the SrTiO3 unit cell. By calculating the divergence of the electric field, we furthermore show the ability to image light atoms such as oxygen, while mapping charge densities in experiment is currently hindered by technical constraints such as scan noise.
12:45 PM - ZZ2.03
Towards a Correct Interpretation of Differential Phase Contrast and Holography of Electric Fields
Ian MacLaren 2 Damien McGrouther 2 Matus Krajnak 2 Vadim Migunov 1 Rafal Dunin-Borkowski 1
1Ernst Ruska-Centre, Research Centre Juelich, Germany Jeulich Germany2University of Glasgow Glasgow United KingdomShow Abstract
We show that a straightforward interpretation of differential phase contrast and holography from materials containing electric fields is problematic. It is confirmed that electric fields in free space deflect the beam in the expected manner and that this is a sufficient explanation for the holography signals in this case. In contrast to this, beam deflections are minimal in polarised perovskites and thus free electric fields are not the main source of any differential phase contrast (DPC) or holographic signal. In contrast to this, strong contrast asymmetries are noted within the primary diffraction disc in areas where strong fields are present. It is found that this diffraction contrast results from polarisation, and this will be the dominant signal contributing to either differential phase contrast or electron holography signals from many materials subjected to electric fields. Thus, any interpretation of differential phase contrast or electron holography of electric fields in materials that does not take explicit account of diffraction contrast in the form of asymmetries within the primary disk is flawed. It is shown that the separation of the effects of E and P fields on the electron beam is best performed using scanned diffraction, and it is suggested that this would be an essential counterpart to future experiments using holography or differential phase contrast in order to provide an unambiguous interpretation of the signals
Philip Batson, Rutgers University
Gianluigi Botton, McMaster University
Mathieu Kociak, CNRS
Johan Verbeeck, EMAT, University of Antwerp
Symposium Support Attolight
JEOL USA, INC.
ZZ7: Adding the Time Dimension/In Situ II
Wednesday PM, April 08, 2015
Marriott Marquis, Yerba Buena Level, Nob Hill C/D
2:30 AM - *ZZ7.01
Understanding Structure-Property Relationships in Nanomaterials by In Situ Electron Microscopy
Joerg R. Jinschek 1
1FEI Company Eindhoven NetherlandsShow Abstract
The strong focus on more efficient energy use and conversion, on more efficient transportation, and on environmental protecting technologies relies heavily on the advancement of (new) functional nanomaterials and nanosystems. At any stage in research and development, studies of these nanomaterials&’ structure, properties, and function are critical, including detailed atomic-scale insights.
Progress in technology and methodology has made scanning / transmission electron microscopes (S/TEM) powerful and indispensable tools for characterizing nanostructures. However, studies e.g. at room temperature and/or under standard high vacuum conditions might be inadequate to investigate the actual functional state of a material or system, whose properties depend on varying operating or environmental conditions.
Fortunately, in recent years the technology has also been significantly advanced to enable in situ studies while maintaining high-resolution imaging and analytical capabilities when applying in situ stimuli to functional nanomaterials, such as temperature, current, gas etc. Implementation of differential pumping apertures in an aberration corrected electron microscope (ETEM ) enables environmental studies, e.g. oxidation, reduction, or corrosion experiments . Further development in in situ heating stages with faster settling time and more accurate knowledge of experimental conditions  enables quantitative atomic-scale studies at elevated temperatures in any (gaseous) environment.
Recent application examples will be presented to highlight in situ S/TEM capabilities and possibilities. As an example, utilizing FEI&’s NanoExtrade;  and ChemiSTEMtrade;  solutions, dynamic EDS studies at elevated temperatures on Boron/Nickel composite nanowires are essential to understand a potential growth model based on coalescence and mobility of Nickel nanoparticles inside the Boron nanowires . Also, reversible pattern evolution of ferroelectric domains in BaTiO3 (BTO) have been observed in heating cycles between room temperature and temperatures above the critical transition temperature (Tc) . Recent relevant ETEM applications will be reviewed as well [1,2].
 J. R. Jinschek, Chemical Communications 50, 2696 (2014)
 P. Schlossmacher et al., Microscopy Today 18 (4), 14 (2010)
 B. Barton, et al., Advances in Imaging and Electron Physics, submitted (2014)
 A. Schilling et al. Microsc. Microanal. 20 (3), 1560 (2014)
3:00 AM - ZZ7.02
In Situ Sintering through Externally Applied Electro-Static Fields at Elevated Temperatures
Klaus Van Benthem 1 Hasti Majidi 1
1University of California, Davis Davis United StatesShow Abstract
The application of electrical fields can enable the accelerated consolidation of materials during field assisted sintering, such as spark plasma sintering or flash sintering. Although such techniques are already employed for the synthesis of a wide variety of microstructures with unique macroscopic properties, a fundamental understanding of the atomic-scale mechanisms that lead to enhanced densification in the presence of electrical fields and/or currents is mostly absent from the literature. In situ transmission electron microscopy experiments will be reported that were designed to investigate densification mechanisms in the absence and presence of electro-static fields. Specific focus is on effects such as dielectric breakdown of passivating oxide layers, neck formation between individual nanoparticles as a function of applied electrical field strength, 3D sintering of Y-stabilized ZrO2 while exposed to electrostatic fields, and strength of individual ceramic powder agglomerates that can limit densification. Such experiments allow the direct structural and chemical characterization of densification mechanisms on the atomic length scale. For Y-stabilzed ZrO2, it was found that densification temperatures and time frames are significantly reduced in the presence of a critical electrical field strength but absence of any currents. The presentation will highlight the current experimental capabilities and report recent results.
Research is supported by the University of California Laboratory Fee Program (12-LR-238313) and the US Army Research Office (program manager: Dr. S. Mathaudu) under grant W911nf-12-1-0491-0.
3:15 AM - ZZ7.03
Dynamics of Nanoscale Dendritic Growth in Liquid
Chung-Hua Chiu 1 Wen-I Liang 1 5 Karen Bustillo 5 Ying-Hao Chu 2 Wen-Wei Wu 3 Haimei Zheng 4
1National Chiao Tung University Hsinchu Taiwan2National Chiao Tung Univ Hsinchu Taiwan3National Chiao Tung Univ Hsinchu Taiwan4Lawrence Berkeley National Lab Berkeley United States5Lawrence Berkeley National Laboratory Berkeley United StatesShow Abstract
Dendritic growth, recognized as a paradigm of non-equilibrium process, is commonly found in nature. However, it still lacks the fundamental understanding of branching mechanisms due to limited capability of imaging nanoscale dendritic growth in solution in situ. With the advances in liquid cell transmission electron microscopy (TEM), we studied the solid-liquid reactions as well as nanocrystal formation. We loaded a precursor solution of iron nitrate, olylamine, oleic acid and benzyl ether into the liquid cell and electron beam induced dendrites growth is observed. The crystal structure and chemical composition have been investigated by high-resolution TEM, electron energy loss spectroscopy (EELS) and energy dispersive x-ray spectroscopy (EDS). The local iron and oxygen ion concentration gradient between the dendritic tip and surrounding solution have been captured. Critical insights have been provided on the solution-based dendritic growth of oxide nanomaterials.
+C. H. C. and W. I. L. contribute equally to the work
We used TEM facilities of the National Center for Electron Microscopy (NCEM) at the Molecular Foundry of Lawrence Berkeley National Laboratory, which is supported by the U.S. Department of Energy (DOE) under Contract No. DE-AC02-05CH11231. HZ thanks the funding support from U.S. DOE Office of Science Early Career Research Program. CHC and WIL acknowledge the funding support from Ministry of Science and Technology (MOST) in Taiwan (No. 103-2917-I-009-185 and NSC 102-2119-I-009-502).
3:30 AM - ZZ7.04
In-Situ Scanning Transmission Electron Micorscopy Study of Liquid-Solid Interactions Using Graphene Liquid Cells
Robert Klie 2 Canhui Wang 2 Tolou Shokuhfar 1
1Michigan Technological Univ Houghton United States2University of Illinois at Chicago Chicago United StatesShow Abstract
Nanoparticle growth, chemical reactions or biochemical activity often occur in the presence of a liquid. To study liquid samples in an electron microscope, several liquid cell designs have become commercially available in recent years that enable materials to be imaged in a carefully controlled liquid environment within the vacuum of a TEM. However, all suffer from a few key limitations that do not allow for atomic-resolution imaging or spectroscopy: 1) two Si3N4 layers (50-500 nm thick) used as electron transparent windows and 2) the thickness of the liquid surrounding the sample. Electron energy-loss spectroscopy (EELS) is degraded by multiple scattering events in the thick window layers, and the strong core-loss signals associated with the presence of Si and N. In addition to the increased sample thickness, radiation damage is a fundamentally limiting factor when examining beam sensitive materials and /or hydrous samples in TEM. It has been shown that coating the specimen with carbon or lowering the temperature have positive effects on radiation damage by reducing electrostatic charging, mass loss, loss of crystallinity, or defect formation rate. However, further reduction of radiation damage is needed for characterization of biological samples.
In this contribution, we will present a novel approach of encapsulating liquid containing samples in monolayers of graphene. This not only allows biological samples to be directly imaged at atomic resolution in a native liquid state without limitations from the window thickness, but also enables nm-scale analysis using EELS to quantify reactions in an aqueous environment. It will be shown that the energy deposited by the incoming electrons is dissipated by graphene from the area irradiated at a rate equivalent to the beam current of several electrons per Å2 per second, reducing the effects of radiation damage and allowing for high-resolution characterization of beam sensitive materials. As a model system, ferritin molecules are examined, and it will be shown that individual Fe atoms or polypeptide of unstained protein can now be resolved in a liquid environment. EELS elemental identification of ferritin molecules with 1 nm resolution is achieved. By carefully controlling the induced electron dose rate, reactions, such as liquid/ gas phase transition can be quantified at selected locations in the graphene liquid cell at nm resolution
3:45 AM - ZZ7.05
In-Situ TEM Mechanical Strain Mediated Carrier Scattering and Its Role in Charge and Thermal Transport
Sandeep Kumar 1 Aman Haque 2
1University of California, Riverside Riverside United States2Pennsylvania State University University Park United StatesShow Abstract
In bulk metals, mechanical strain is known not to influence electrical and thermal transport. However, their high volume fraction of grain boundaries and different deformation mechanisms may make nanocrystalline metals violate classical physics. To investigate this hypothesis, we developed an experimental approach, where we performed thermal and electrical conductivity measurements on 100 nm thick freestanding nanocrystalline aluminum films in situ inside a transmission electron microscope (TEM). We present experimental evidence of decrease in thermal conductivity and increase in electrical resistivity as a function of uniaxial tensile strain. In-situ TEM observations suggest that that grain rotation induced by grain boundary diffusion is the dominant deformation mechanism in these thin films. We propose that diffusion causes rise in oxygen concentration resulting in increased defects at grain boundaries. Presence of oxygen only at the grain boundaries is confirmed by energy dispersive spectroscopy. Increased defect concentration by mechanical strain at grain boundary causes the change in thermal and charge transport.
4:30 AM - ZZ7.06
Studies on In Situ Heat-Treatment and Corrosion of Al Alloy 2024 in a TEM
Sairam Malladi 1 Ahmet Erdamar 1 Tom de Kruijff 1 Chunhui Liu 2 1 Frans Tichelaar 1 Henny W. Zandbergen 1
1Delft University of Technology Delft Netherlands2Center for High Resolution Electron Microscopy Changsha ChinaShow Abstract
Over the years, Transmission Electron Microscopy (TEM) has been a primary characterization tool to understand the structure-property relationship of most of the materials. In most of the studies, the specimens are investigated post-mortem. There have been several successful attempts to carry out in situ TEM experiments wherein dynamic changes in a specimen are investigated while applying a stimulus like heating, electrical bias, mechanical deformation or exposing to a reactive environment. With the advancements in TEMs and micro-electro-mechanical systems (MEMS), the area of in situ TEM has progressed extensively over the last decade. Here, we show the application of MEMS based devices developed in-house to carry out in situ heat-treatment and environmental TEM studies. For environmental TEM studies, a controlled environment is established inside the TEM by one of the following approaches: the open type, using a differentially pumped vacuum system where the reactive gases are spread around the specimen area of the TEM; and the closed type, using a windowed environmental cell. Our studies are based on the closed environmental cell called the nanoreactor. The nanoreactor consists of two silicon chips facing each other with thin electron-transparent silicon nitride membranes. One half of the nanoreactor (bottom half) is embedded with a Pt coil for resistive heating. Using one half of the nanoreactor, we have demonstrated the growth of S-type precipitates in Al alloy 2024 while heating in the range of 180 - 250 °C. When closed with the other half, we have succeeded in studying the localized corrosion of Al alloy 2024-T3 at room temperature. The initial experiments were carried out by gluing both the halves of the nanoreactor together.
One of our recent developments is a holder that allows assembling a leak-tight nanoreactor without any gluing. The main advantage of using such a holder is the possibility to dissemble the nanoreactor to carry out any further analysis like chemical mapping and tomography after a chemical reaction with the surrounding environment. Furthermore, the contamination due to gluing is also avoided. In the present study, using this holder, we demonstrate the corrosive attack of an Al alloy that has been heat-treated at 250 °C in an environment of oxygen bubbled through aqueous HCl of pH 3. After corrosion, STEM-tomography has been carried out to understand the propagation of the corrosive attack. These sort of experiments are critical to understand the performance of engineering materials in service conditions. It is now possible to correlate the microstructural changes happening during the service of an engineering alloy, due to any processes that can heat the material like welding or higher operating temperatures, with the changes in the environment.
4:45 AM - ZZ7.07
In-Situ Investigation of the Reaction of Calcium Sulfate Nanoparticles in Deionization Water
Kun He 1 3 Anmin Nie 3 Constantine Megaridis 2 Tolou Shokuhfar 3 Yu-Peng Lu 1 Reza Shahbazian-Yassar 3
1Shandong University Ji'nan China2Univ of Illinois-Chicago Chicago United States3Michigan Technological University Houghton United StatesShow Abstract
It is very common to synthesize and use some nanomaterials nowadays. Because most nanomaterials are prepared in the laboratory, especially for those synthesized using chemical methods in aqueous environments, it is difficult to observe and understand the reaction process accurately. Herein, employing transmission electron microscopy (TEM), aberration-corrected scanning transmission electron microscopy (STEM) and liquid holder techniques, we investigate the reaction of calcium sulfate with water. Using TEM, we obtain unambiguous evidence that the morphology and microstructure of calcium sulfate hemihydrates (Bassanite, CaSO4bull;0.5H2O) and calcium sulfate dihydrate (Gypsum, CaSO4bull;2H2O) are both changed when reacting with deionized (DI) water. Bassanite reacts with water to form gypsum, with the microstructure changing from powder to nanowires with needle or rod shape; when gypsum reacted with DI water, the microstructure changed to nanowires without any compositional or crystallographic variation, as proven by electron diffraction. However, the reaction of gypsum with water was a complex process that did not reveal new information on the microstructure evolution.
Using liquid holder under TEM mode, the structure transformation of the gypsum was tracked and recorded in real time. The gypsum powder was observed to dissolve in DI water. The dissolution of nanowires that formed during reaction of gypsum powder and water started when the nanowires were exposed to electron beam. Initially, fractures formed inside the nanowire. And then the size of the nanowires decreased as they dissolved in the water until they were invisible in TEM.
5:00 AM - ZZ7.08
In-Situ Quantitative TEM Studies with Micro-Electro-Mechanical Systems
Baoming Wang 1 MD Tarekul Alam 1 Raghu Pulavarthy 1 Aman Haque 1
1Penn State University University Park United StatesShow Abstract
In this study, we design, simulate and fabricate a micro-electro-mechanical system (MEMS) based experimental setup, which is capable of performing mechanical tests inside a transmission electron microscope (TEM) at elevated temperature up to 1000 °K. The MEMS device is fabricated on silicon-on-insulator (SOI) wafer and has integrated heaters, force sensors and thermal actuators. The device can be co-fabricated with thin films deposited on the wafer, as long as they can be patterned and subsequently released from the substrate to create freestanding uniaxial tension specimens. Young&’s modulus, fracture stress as well as stress-strain relationship of thin films at high temperatures can be demonstrated to visualize deformation and fracture mechanisms inside the TEM. The device is demonstrated on metal films as well as graphene, molybdenum di-sulfide and boron nitride. Addition of microelectrodes in the device also allows in-situ measurement of thermal and electrical conductivity in-situ inside the TEM while the specimen microstructure is modulated by external stimuli such as temperature or stress.
5:15 AM - *ZZ7.09
Electron Beam Decoherence Produced by Thermal Fluctuations
Javier Garcia de Abajo 1
1ICFO-The Institute of Photonic Sciences Barcelona SpainShow Abstract
A detailed analysis of thermal decoherence in electron beams is presented. We find that thermal noise during the interaction of the electrons with distant materials leads to observed stochastic deflection angles and losses of visibility in self-interference experiments that are relatively insensitive to the conductivity of the material. Interestingly, the electron undergoes angular broadening even in symmetric configurations, such as when it moves along the axis of a hollow tube. The presented formalism can be readily applied to arbitrary materials and interaction geometries. Besides their fundamental interest, these results are of interest for the improvement of spatial resolution in future electron microscopes.
ZZ6: Adding the Time Dimension/In Situ I
Wednesday AM, April 08, 2015
Marriott Marquis, Yerba Buena Level, Nob Hill C/D
9:30 AM - *ZZ6.01
Nanoplasmonic Imaging with Ultrafast Transmission Electron Microscopy
Aycan Yurtsever 1
1Institut National de la Recherche Scientifique (INRS) Varennes CanadaShow Abstract
Localized electric fields that are induced optically exhibit unique phenomena of fundamental importance to nanoplasmonics. In recent years, they have been considered for efficient photovoltaic and light harvesting devices, single molecule detection, biomolecular labeling and manipulation, and surface enhanced Raman scattering. Success has been made in developing experimental methodologies to probe the effect of their presence, but it remains difficult to directly and robustly image the optically induced near-fields, both in space and time. Herein, we introduce a novel imaging methodology that can directly map the near-fields of nanoplasmonics with spatiotemporal resolutions that were not possible before. Ultrafast transmission electron microscopy (UTEM) enables the direct visualization of the electric fields as they rise and fall within the duration of the excitation laser pulse (few hundreds of femtoseconds) with several nanometers of spatial resolution. This imaging approach is based on an inelastic photon-electron interaction process, where the probing electrons gain energy equal to the integer multiple of the photon quanta (2.4 eV in these experiments). This new phenomenon in electron energy loss spectroscopy and its fundamentals are discussed. Furthermore, we present images, and movies, of the near-fields of particle dimers, nanoparticles with different sizes and shapes, particle ensembles and standing-wave plasmons at the step edges of layered-graphene strips. These results establish UTEM as a tool with unique capabilities to approach nanoplasmonics.
10:00 AM - ZZ6.02
Deep Ultraviolet Dielectric Response Forces in Nanometer-Sized Gold Particles
Maureen Joel Lagos 2 Alejandro Reyes-Coronado 3 Pedro Echenique 1 Javier Aizpurua 1 Philip Batson 2
1CSIC-UPV/EHU San Sebastian Spain2Rutgers University Piscataway United States3Universidad Nacional Autoacute;noma de Meacute;xico (UNAM) Mexico City MexicoShow Abstract
In the first experimental imaging of Au atoms and nanometer sized Au particles using aberration-corrected STEM, copious movement of particles, including both attractive and repulsive forces, was immediately apparent . Numerical calculations, by us and by others, confirmed this hypothesis and also identified a repulsive force for sub-nanometer impact parameters,  but did not yield a detailed understanding of the mechanisms