Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session Q27: Focus Session: X-ray and Neutron Instruments and Sciences II |
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Sponsoring Units: GIMS Chair: Dennis Mills, Argonne National Laboratory Room: 329 |
Wednesday, March 18, 2009 11:15AM - 11:27AM |
Q27.00001: 3D Mapping of Strain and Dislocation Gradients near Surfaces and Interfaces via Polychromatic Microdiffraction Rozaliya Barabash, Gene Ice The results of 3D polychromatic X-ray microbeam analysis (PXM) of strain and dislocation gradients are presented. Two examples are considered: (1) FIB machined nano-size trenches in thin GaN/InGaN multylayers; (2) natural nanosize Mo pillars in the NiAl matrix of the eutectic composite alloy. Position sensitive $d$-spacings were obtained from Laue patterns. The PXM results show that FIB induces structural changes and \textit{lattice rotations} in the InGaN/GaN layer not only in the immediate trench region but in the surrounding area as well. For embedded nanosize Mo fibers, the measured elastic strain is consistent with the predicted thermal mismatch strain between the NiAl and Mo phases. However, when the NiAl matrix is etched back to expose Mo micro-pillars, the $d$-spacing increases to that of unconstrained Mo, indicating release of the compressive residual strain in the Mo fibers. [Preview Abstract] |
Wednesday, March 18, 2009 11:27AM - 11:39AM |
Q27.00002: Strain Fields in Zeolite Microcrystals by Coherent X-ray Diffraction Hyunjung Kim, Wonsuk Cha, Sanghoon Song, Nak Cheon Jeong, Kyung Byung Yoon, Ross Harder, Ian K. Robinson We measured coherent X-ray diffraction (CXD) on zeolite microcrystals in order to get information on internal density distribution and to map deformation field of stress or strain during the fabrication process. The experiments were performed at the beamline 34-ID-C in Advanced Photon Source and employed monochromatic radiation with x-ray energy of 9 keV. The sample size was about $\sim$2{$\mu$}m. The diffraction patterns were obtained at (200) Bragg condition with unfocused beam. We inverted the diffraction patterns to obtain three dimensional images of the shapes and internal strain fields of zeolite microcrystals using phase retrieval algorithms of error reduction and hybrid input-output method. The internal density and strain distribution as a function of temperature will be discussed. [Preview Abstract] |
Wednesday, March 18, 2009 11:39AM - 11:51AM |
Q27.00003: Silicon x-ray monochromator surfaces by independent oxidation and etching steps Albert Macrander, Kimberley MacArthur, Josef Maj, Jun Qian, Dan Linnen, Ruben Khachatryan, Michael Wieczorek, Ray Conley, Alan Genis X-ray monochromators should ideally possess a surface that does not distort a diffracted beam. Beam distortions have been observed at the APS for rough surfaces. Mechanical polishing leaves sub-surface damage. The standard method to remove this damage is to wet etch Si crystals in a mixture of nitric acid and hydrofluoric acid. During the etch an oxide is produced and removed in the same acid bath. X-ray diffraction from a bulk reflection that is largely unaffected by strain can be obtained by this method. However, the smoothness is degraded to produce an orange-peel morphology. For the present study we carried out the oxidation and etching steps independently. By first growing an oxide layer in a furnace and subsequently etching away the the oxide layer, we find that sub-surface damage can be removed and the surface quality can be improved over that found with only wet etching. [Preview Abstract] |
Wednesday, March 18, 2009 11:51AM - 12:03PM |
Q27.00004: Observation of annealing of grains in high purity aluminum using High Energy X-ray Diffraction Microscopy C.M. Hefferan, S.F. Li, U. Lienert, R.M. Suter High energy x-ray diffraction microscopy (HEDM) is capable of measuring volumes of polycrystal microstructure on a granular basis, producing spatial maps of crystallographic orientation covering ensembles of grains with micron resolution. A non-destructive experimental probe capable of observing the response of polycrystals to thermo-mechanical stimulus, HEDM establishes constraints on analytic materials models. HEDM uses high-brilliance, line focused synchrotron x-rays to image diffracted beams emanating from individual grains in a succession of planar sections. Area detector images of diffraction patterns are collected as the sample rotates normal to the beam plane. A forward modeling computer simulation adjusts local crystallographic orientations and compares simulated scattering to experimental images in order to optimize the match with observations. Three dimensional digital representations are generated from large numbers of reconstructed sections. Growth measurements on high purity polycrystalline aluminum have been conducted at the 1-1D beamline at the Advance Photon Source at Argonne National Laboratory and reconstructions have been obtained using the Pittsburgh Supercomputing Center. Both defect annealing and grain boundary motions have been observed and will be described. [Preview Abstract] |
Wednesday, March 18, 2009 12:03PM - 12:15PM |
Q27.00005: Strain Analysis in 2D and 3D X-ray Microscopy J.Z. Tischler, B.C. Larson, Wenjun Liu, Lyle Levine Spatially resolved strain distributions on the submicron length scale are important for materials problems such as deformation and phase separation, and in heterogeneous systems in general. High-energy 3DXRD techniques have been developed by RISO with a few micron 3D resolution for lightly deformed materials. However, submicron 3D spatial distributions of local strain in heavily deformed materials are often required, such as in for multiscale materials modeling. We have developed a scanning-monochromatic x-ray microbeam technique on sector-34 of the Advanced Photon Source to measure the Q-distribution from submicron volume elements in lightly and heavily deformed materials and in single, polycrystalline, or composite materials. By sorting the intensity from every pixel in an area detector during nested energy and differential–aperture depth scans, Q-distributions are obtained for every spatially resolved volume element. We will present measurement examples and discuss the range of applications. [Preview Abstract] |
Wednesday, March 18, 2009 12:15PM - 12:27PM |
Q27.00006: Towards mapping of defected grains using high energy x-ray diffraction microscopy Shiu Fai Li, C.M. Hefferan, U. Lienert, R.M. Suter High energy x-ray diffraction microscopy (HEDM), the use of focused high energy synchrotron x-ray radiation diffraction imaging, is becoming a promising technique for orientation mapping of polycrystalline material. The nondestructive nature of HEDM makes real-time observation of inter- and intra-grain dynamics possible. Collected HEDM data in the form of diffracted images on a high resolution 2D detector is analyzed by a Monte Carlo fitting algorithm using a forward modeling method, which simulates a set of detector images based from a specified orientation field. Since no specific assumptions are made regarding grain shapes and topologies, internal mosaic structures may be captured. The combination of nondestructive nature and intra-grain resolution makes it an ideal candidate for in situ studies of grain damage due to strain/stress treatment. A proof of concept has been demonstrated in observations of intra-grain orientation mosaics from both orientation maps of polycrystalline aluminum obtained from experiments conducted at beam line 1-ID of the Advanced Photon Source and forward modeling simulations. [Preview Abstract] |
Wednesday, March 18, 2009 12:27PM - 12:39PM |
Q27.00007: A Holographic Iterative Algorithm for X-ray Microscopy Diling Zhu, Benny Wu, Ramon Rick, Joachim St\"{o}hr, Andreas Scherz In recent years X-ray Fourier transform holography has gained recognition as a high resolution microscopy technique. The phase information is encoded in the hologram which renders this lensless approach as a true imaging technique by applying a simple inverse Fourier transform. In previous experiments the resolution was limited by imperfect knowledge of the reference and therefore was determined by the size of the reference. We report an alternative technique based on direct calculation of the encoded phase by recording multiple holograms. This phase information provides additional constraints to uniquely deconvolve the reference and the object using iterative phase retrieval algorithms. In numerical simulations we observe rapid convergence of this new reference-guided phase retrieval method which also shows high immunity against noise. We present two different experimental implementations and their results to demonstrate the feasibility of the concept. [Preview Abstract] |
Wednesday, March 18, 2009 12:39PM - 12:51PM |
Q27.00008: New Method for Inverting X-ray Holographs Yuhao Wang, Jianming Bai, Trevor A. Tyson, Peter Siddons, Gianluigi De Geronimo The matrix solving method is a new class of methods to be applied to inverting an x-ray holograph for obtaining real space structures. The method is shown to provide better resolution and more flexibility than Fourier transform methods. Simulations suggest that non-direct scheme non-indirect scheme x-ray fluoresce holograph, measured with both fixed light source and fixed detector can be inverted with the matrix solving method. Applying pre-determined non negative restrictions can improve the spatial resolution and approach the wavelength of the measuring x-rays. Experimental details and methods for measuring x-ray florescence holography with the matrix solving inversion is discussed. This work is supported by NSF DMR grant MRI-0722730. [Preview Abstract] |
Wednesday, March 18, 2009 12:51PM - 1:03PM |
Q27.00009: Growth and characterization of high k ZrO$_{2}$ on Ge (100) Abdul Rumaiz, Gabriella Carini, Peter Siddons, Joseph Woicik, Pavel Rehak The higher mobility of carriers combined with a low effective mass in Ge as compared to Si has generated a lot of interest in Ge based devices. This is particularly so in X-ray radiation detectors where Si based detectors become transparent at higher energy. The challenge in realizing a Ge based detector is having a robust barrier oxide since the native Ge oxide is hygroscopic. We have grown high k ZrO$_{2}$ on Ge (100) using direct metal sputtering followed by UV oxidation [1]. High energy X-ray photoelectron spectroscopy (XPS) was performed to study the oxidation state of ZrO2 as well the interface with Ge. A simple structure with Ge/GeO/ZrO$_{2}$(25 nm)/Al (200 nm) was created. A significant hysteresis was observed in the capacitance-voltage measurement which is indicative of some interface states [2]. The effect of the intermediate layer between ZrO$_{2}$ and Ge on the interface states will be addressed. Valence band measurement done using high energy XPS will be discussed. [1] C. O. Chui, S. Ramanathan, B. B. Triplett, P. C. McIntrye and K. C. Sarawat, IEEE Electron Dev. Lett. 28, 473 (2002) [2] H. Kim, C.O. Chui, K. C. Sarawat and P. C. McIntrye, Apl. Phys. Lett. 83, 2647 (2003) [Preview Abstract] |
Wednesday, March 18, 2009 1:03PM - 1:15PM |
Q27.00010: High-field pulsed magnet instruments for x-ray studies of materials at the Advanced Photon Source Zahirul Islam, J.P.C. Ruff, Y. Matsuda, Z. Qu, H. Nojiri, B.D. Gaulin, S. Yoshii, Z. Mao, J.C. Lang High-field pulsed magnets are not the solution to x-ray studies of all problems requiring high magnetic fields, but, they are the only solution to many. We present a very high-field pulsed magnet system for x-ray studies of materials at the Advanced Photon Source (APS). The high-field instruments for x-ray studies are unique in the United States. Currently, 30 Tesla split-coil and long-pulse solenoid magnets are in use for scattering and spectroscopic experiments, respectively. The coils are made of CuAg wires. Pulsed fields (1-10 ms in duration) are generated using a configurable bipolar capacitor bank (40 kJ). For scattering studies split coils are mounted on the cold finger of a closed-cycle He cryostat capable of a repetition rate of $\sim$10-20 minutes for peak fields in the range of 20-30 Tesla. Time-resolved scattering data are typically collected using a fast APD detector. Initial scattering studies of a geometrically frustrated magnet will be presented. [Preview Abstract] |
Wednesday, March 18, 2009 1:15PM - 1:27PM |
Q27.00011: Longitudinal and Transverse Components in the X-ray Resonant Magnetic Reflectivity Experiment J.-S. Lee, E. Vescovo, C.-C. Kao, J.-M. Beaujour, A.D. Kent, H. Jang, J.-Y. Kim, J.-H. Park X-ray Resonant Magnetic Reflectivity (XRMR) is a powerful tool: It allows to simultaneously probe the structural and the magnetic properties of complex multilayer structures. It is often advantageous to utilize circular polarized synchrotron radiation to obtain magnetic information. Unfortunately, in XRMR measurement using circular polarization, the transverse and longitudinal components are intrinsically mixed, making a proper vector-analysis of the magnetization usually impossible. In this work, we strive to overcome this restriction. In particular we demonstrate how to effectively separate the transverse and longitudinal components in the scattering experiment using circular polarized light. This is accomplished by taking advantage of x-ray interference effects which fully suppress the longitudinal component at all angles where the magnetic asymmetry ratio is null. At these angles only the purely transverse component is therefore left in the data. [Preview Abstract] |
Wednesday, March 18, 2009 1:27PM - 1:39PM |
Q27.00012: Monte-Carlo Resampling Analysis of Neutron and X-ray Reflection Data F. Heinrich, P. Shekhar, P. Kienzle, M. Loesche In most cases, reflectivity data analysis relies on the use of a structural model with reasonable physical constraints. Commonly, parameter confidence intervals are estimated, and the choice of the adequate model solely relies on the of the experimenter. We present the implementation of a Monte-Carlo resampling technique for reflectometry data analysis [F. Heinrich et al. A new lipid anchor for sparsely-tethered bilayer lipid membranes. Langmuir, submitted]. It is based on the statistical evaluation of a large number of fits with resampling. This technique provides access to precise confidence intervals for model parameters and parameter correlation matrices. It allows one to identify an over-parameterization of the model and provides a tool for a controlled model extension with additional parameters. This becomes especially important in the prospect of the new neutron sources where data with higher information content will be available. We also present an emerging application of the Monte-Carlo resampling technique that allows the determination of unknown elements free of any structural assumptions. [Preview Abstract] |
Wednesday, March 18, 2009 1:39PM - 1:51PM |
Q27.00013: Scatterless Hybrid Metal-Single Crystal Slit for Small Angle X-ray Scattering and High Resolution X-ray Diffraction. Youli Li, Roy Beck, Tuo Huang, Myung Chul Choi, Morito Divinagracia A simple hybrid design has been developed to produce effectively scatterless aperture slits for small angle x-ray scattering (SAXS) and high resolution x-ray diffraction. The hybrid slit consists of a single crystal (Si, Ge) edge bonded to a tapered high density metal base. The beam-defining single crystal tip is oriented at a large tilt angle with respect to the beam and far from any Bragg peak position, and hence should produce no slit scattering commonly associated with conventional metal slits. The scatterless performance of the new slit design was confirmed by experiments conducted with laboratory x-ray sources as well as third generation synchrotron radiation. The new scatterless slits have been successfully used for SAXS application, where it led to a greatly simplified Single Aperture SAXS design with dramatically increased intensity (3-fold observed) as well as improved low angle resolution compared to a conventional three-pinhole set up.* Y. Li, R. Beck, T. Huang, M.C. Choi, M. Divinagracia, J. Appl. Cryst. (2008) 41, 1134-1139 [Preview Abstract] |
Wednesday, March 18, 2009 1:51PM - 2:03PM |
Q27.00014: Resonant soft x-ray scattering from Cu valence modulations in oxygen ordered YBCO David Hawthorn, K.M. Shen, J. Geck, D.C. Peets, H. Wadati, Ruixing Liang, D.A. Bonn, W.N. Hardy, G.A. Sawatzky, J. Okamoto, D.J. Huang, H.-J. Lin, Jonathan Denlinger Recently resonant elastic soft x-ray scattering (RSXS) has emerged as a powerful new tool to study electronic ordering in materials like cuprates and manganites. The power of this technique is to combine x-ray scattering, which is sensitive to spatial order, with x-ray spectroscopy, which is sensitive to the valence, spin and orbital symmetry of specific atoms. This combination allows one to probe very directly and considerable detail a variety of exotic spin, charge, orbital or structural ordering phenomena. I will discuss the application of this technique to an important test case, oxygen ordering in YBCO. In this system we are able to accurately calculate the energy dependence of the scattering intensity, providing a basis for understanding the spectroscopy of more complex systems. [Preview Abstract] |
Wednesday, March 18, 2009 2:03PM - 2:15PM |
Q27.00015: Phase Separation of Water/Glycerol Binary Mixtures Next to Lipid Monolayers -- An X-ray and Neutron Reflectivity Study Luka Pocivavsek, Brian Leahy, Mati Meron, Binhua Lin, Jarek Majewski, Ka Yee Lee We recently developed a general model for studying instabilities like wrinkling and folding in interfacial membranes on fluid substrates. The dominant length scales describing the instability are set by the elastic response of the membrane (primarily bending) and the ``stiffness'' of the substrate. These length scales, like the wrinkle wavelength and fold amplitude, are independent of the particular interfacial molecular interactions for micron thick membranes where typical system energies like the membrane bending stiffness are thousands of times larger than intermolecular potentials. However, as the membranes become thinner and thinner and eventually approach molecular membranes only a couple of nanometers thin, the chemical interactions between the membrane and the fluid substrate strongly influence the wrinkling and folding length scales. We present data for two such systems (a lipid monolayer and a gold nanoparticle layer) on different hydrogen bonding fluids and discuss possible mechanisms and modifications of our wrinkle-to-fold scaling laws to account for this new degree of freedom. [Preview Abstract] |
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