Recent Advances in Structural Characterization of Materials: Electron and X-Ray Microscopy: Structural Characterization of Nanoscale Materials
Program Organizers: Zhonghou Cai, Argonne National Laboratory; Roumiana Petrova, New Jersey Institute of Tech; Jacob Jones, University of Florida
Wednesday 8:00 AM
October 28, 2009
Room: 306
Location: David L. Lawrence Convention Ctr
Session Chair: Roumiana Petrova, New Jersey Institute of Technology
8:00 AM Invited
Quantitative STEM-EDS Mapping and Analysis: Chad Parish1; Luke Brewer1; 1Sandia National Laboratory
Improving the properties of engineering materials requires insight into the microstructure and chemical homogeneity. In particular, Pb(Zr,Ti)O3 (PZT) thin-film ferroelectrics suffer degraded properties when the cations are arranged inhomogenously within the film thickness. In this work, we describe a method using multivariate statistical analysis of scanning transmission electron microscopy - energy dispersive X-ray spectroscopy spectrum images to map the arrangement of the cations in PZT thin films at a resolution finer than 10 nm. Significant Zr/Ti partitioning is seen in these films, and the La-dopant distribution is also inhomogeneous. We also used experiments and Monte Carlo simulations to explore the accuracy and precision of the proposed method, and find that good statistical bounds for the quantification can be achieved.
8:40 AM Invited
Nanoscale Characterization of Strain in Thin Films and Devices Using the Hard X-Ray Nanoprobe: Jörg Maser1; Martin Holt1; Robert Winarski1; Volker Rose1; 1Argonne National Laboratory
The Center for Nanoscale Materials’ Hard X-ray Nanoprobe Beamline at the Advanced Photon Source is designed to characterize composition and structure of nanoscale materials and devices with high spatial resolution. The beamline provides x-rays with photon energies between 3 keV and 30 keV, thus allowing x-ray fluorescence mapping and –spectroscopy for most elements of the periodic system, as well as x-ray diffraction The Nanoprobe instrument combines interchangeable scanning probe and full-field transmission mode. In scanning probe mode, x-ray fluorescence, diffraction contrast and Bragg coherent diffraction are brought to bear to characterize specimens. In full-field transmission mode, tomographic images of complex materials systems and devices can be acquired. The Nanoprobe instrument is designed to use diffractive optics for both focusing and imaging. An initial spatial resolution of 30 nm has been achieved using Fresnel zone plates. We'll report on initial experiments, with emphasis on nanodiffraction of strained materials and devices.
9:20 AM
Atomic Number Contrast Quantitative Scanning Transmission Electron Microscopy of Nanoparticles and Nanomultilayers: Biao Yuan1; Helge Heinrich1; Aniruddha Dutta1; Beatriz Roldan1; Bo Yao1; 1University of Central Florida
A quantitative method to determine the thickness in TEM using the Scanning Transmission Electron Microscopy (STEM) mode is introduced. With a High-Angle Annular Dark-Field (HAADF) detector, electrons scattered to high angles are collected. The intensity of the HAADF signal is proportional to the sample thickness. With increasing atomic number the HAADF-STEM signal increases resulting in atomic number contrast in combination with linear thickness contrast. To determine thicknesses of nanoparticles, the composition of these particles is determined by elemental analysis using characteristic x-rays or characteristic absorption edges of the transmitted electrons. For the quantitative thickness measurement, multilayered samples provided by TriQuint in Apopka (FL) were used for calibration and yield data on the interaction cross section per atom. These calibrations were applied to determine thicknesses and volumes of individual Au-Fe, Pt, Au, and Ag nanoparticles and concentrations in nanoscale Fe-Pt multilayers.
9:40 AM Break
10:00 AM Invited
Submicron Beam X-Ray Diffraction Characterization of Selectively Grown Structures for Optoelectronics: Andrei Sirenko1; 1NJIT
Advanced characterization tools, such as synchrotron radiation based submicron-beam high-resolution x-ray diffraction (HRXRD), are required to support the current trends in monolithic materials integration for optoelectronics. Our recent characterization results have been obtained with a nondestructive HRXRD technique and reciprocal-space-mapping (RSM) with the x-ray beamsize of 240 nm. Our HRXRD experiments have been carried out at two synchrotron facilities: at A2 beamline at CHESS equipped with a one-bounce focusing capillary optics and at the APS 2ID-D microscope beamline equipped with a phase zone plate. We focus our studies on optoelectronic structures with active regions consisted of InGaN/GaN multiple-quantum-wells. Understanding of the fundamental growth mechanisms and how they affect the structural and optical properties of the GaN-based NSAG structures is an important step towards their industrial applications. Thickness, strain, composition variation, and details of precursor surface migration have been determined for various structures obtained by nanoscale selective area growth.
10:40 AM
Three Dimensional Characterization of Magnetic Induction Using Lorentz Transmission Electron Microscopy: Charudatta Phatak1; Emma Humphrey1; Amanda Petford-Long2; Marc De Graef1; 1Carnegie Mellon University; 2Argonne National Laboratory
The Lorentz TEM observation mode can be used to characterize the magnetic induction of thin foil samples. The technique generates a two dimensional projection of the actual 3-D field in and around the sample. Combining this technique with tomographic reconstruction methods, one can obtain quantitative information about the true 3-D nature of the magnetic induction in and around the sample. In this contribution, we will present experimental and numerical procedures to achieve a 3-D characterization of the magnetic induction. Experimental data was obtained on a single sample using two instruments: a Tecnai F20 and a JEOL 2100F. Tomographic reconstructions will be compared to each other and to a theoretical model; the sources of deviation from the predicted values will be discussed, as well as improvements which can be made by the use of an aberration corrected instrument.
11:00 AM
Studies on Size-Dependent Crystallinity of Pt Nanoparticles Supported on γ-Al2O3: Long Li1; Lin-lin Wang2; Sergio Sanchez2; Joo Kang2; Qi Wang3; Zhongfan Zhang1; Anatoly Frenkel3; Duane Johnson2; Ralph Nuzzo2; Judith Yang1; 1University of Pittsburgh; 2University of Illinois at Urbana-Champaign; 3Yeshiva University
Platinum nanoparticles (NPs) supported on γ-Al2O3 were synthesized with a size range from sub- to several nanometers in order to study size-dependency of their atomic structure. High-resolution transmission electron microscopy (HRTEM) and focal series reconstruction (FSR) revealed a size-dependent crystallinity of the Pt NPs, where Pt NPs with size <1 nm adopted disordered structure and the ones with size >2.5 nm showed an FCC crystalline structure. A transition zone exists between 1.1 and 2.4 nm, in which ~85% of NPs appeared disordered and ~15% ordered. X-ray absorption spectroscopy (XAS) measurements support this result where static disorder of Pt-Pt bond length distribution evidently increased with decreasing Pt nanoparticle size. Molecular dynamics (MD) simulation confirmed that the ground state structure of Pt37/γ-Al2O3(100) (1.1 nm in size) is disordered and more energetically favorable than the ordered close-packed structure by 0.04 eV per Pt atom.
11:20 AM
High Contrast Hollow-Cone Dark Field Transmission Electron Microscopy for Nanocrystalline Grain Size Quantification: Bo Yao1; Tik Sun1; Andrew Warren1; Kevin Coffey1; Katayun Barmak2; 1Advanced Materials Processing and Analysis Center and Department of Mechanical, Materials and Aerospace Engineering, University of Central Florida; 2Department of Materials Science and Engineering, Carnegie Mellon University
Grain size and grain size distribution strongly influence many materials properties of interest, including mechanical and electrical properties. For nanocrystalline materials, the scale of grain size necessitates the use of transmission electron microscopy (TEM) for quantification. Given the complex contrast of TEM images of some materials, grain size quantification still requires hand-tracing of grain boundaries in high quality TEM images, where each grain has adequate contrast to its neighbor grains. Conventional bright-field and dark-field TEM images often cannot provide this contrast for all the grains in the field of view. In this study, hollow-cone dark field (HCDF) is used to form high contrast images suitable for nanocrystalline grain size quantification. The critical factors influencing the image quality are summarized. The techniques that we recently explored for rapid preparation of high-quality samples for HCDF TEM are also discussed. Both film and bulk form nanocrystalline samples are used as examples.