Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session X21: Focus Session: Novel X-Ray Instrumentation and Measurement Techniques |
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Sponsoring Units: GIMS Chair: Albert Macrander, Argonne National Laboratory Room: D161 |
Thursday, March 24, 2011 2:30PM - 3:06PM |
X21.00001: Inelastic X-ray Scattering at Third Generation Synchrotron Sources: Present Activities and Future Plans Invited Speaker: This talk will review present activities and future plans for utilizing inelastic x-ray scattering to study excitations in hard condensed matter systems. In particular, at current third generation sources it is now possible to observe the key elementary excitations in solids, including phonons, magnons, orbital excitations and electronic excitations such as plasmons and charge transfer excitations. The technique offers a number of advantages over existing methods for the study of these excitations, including especially, the ability to study very small sample volumes, the range of momentum and energy transfers available and the ability to work in disparate sample environments. A few recent illustrative examples are discussed. The first of these is a study of phonons in SmFeAs(O,F) which show an anomalous renormalization of certain phonons and for which momentum-dependent measurements of the electron-phonon coupling have been made. The second example will focus on work being performed at the Swiss Light Source in which spin waves in (La,Sr)CuO4 have been observed. Finally, the current and future state of inelastic x-ray scattering instrumentation in this country is discussed, including the upgrade plans at the Advanced Photon Source, and plans for new inelastic beamlines at the NSLS-II source currently under construction at Brookhaven National Laboratory [Preview Abstract] |
Thursday, March 24, 2011 3:06PM - 3:18PM |
X21.00002: The new X-ray absorption spectroscopy beamline at Diamond: B18 Silvia Ramos, Giannantonio Cibin, Stephen Parry, Andy J. Dent The new core XAS spectroscopy beamline at Diamond (B18) has been designed to provide a reliable spectrometer for a broad scientific community. The instrument first became operational in April 2010 and is currently combining further commissining with a rapidly growing user programme. The main goal of the optics design of B18 was to achieve high stability in an instrument that can operate over a wide energy range (2.05 to 35.0 keV). XAS measurements can be carried out using several detection methods: transmission, electron yield and fluorescence (with a Ge detector, a Si drift detector or a gas microstrip). It is also possible to carry out combined absorption and diffraction measurements. The instrument offers several sample environments: a liquid nitrogen cryostat capable of loading over 40 samples, a pulse tube cryostat with base temperature of 1.6 K and an infrared furnace with a maximum temperature of 800$^{o}$C and can integrate a variety of specialised set-ups designed by the users. In this talk we will present the beamline and selected examples to show its capabilities. [Preview Abstract] |
Thursday, March 24, 2011 3:18PM - 3:30PM |
X21.00003: The soft x-ray materials research (SXR) instrument at the Linac Coherent Light Source Joshua J. Turner, Oleg Krupin, William Schlotter The soft x-ray materials science research (SXR) instrument completed commissioning in June 2010 and began experimental user operations shortly afterwards. This instrument delivers intense, ultra-short soft x-ray pulses from the Linac Coherent Light Source, the free-electron laser at the SLAC National Accelerator Laboratory. These are fully coherent and can contain up to $10^{13}$ photons per pulse (or about 3 mJ per pulse) with bunch lengths from 300 femtoseconds down to sub-10 femtoseconds. The instrument includes a monochromator whose energy range spans energies from 480 eV - 2000 eV and a Kirkpatrick-Baez mirror system to create a focal spot of a few microns in diameter. The SXR instrument has a diverse set of end stations available to conduct a large variety of experimental techniques such as coherent imaging, resonant x-ray diffraction, photoelectron spectroscopy, and x-ray emission and/or absorption. First studies include fields spanning liquid femtosecond chemistry and time-resolved resonant inelastic x-ray scattering to ordering in solids and ultrafast magnetization. An overview of the instrument and its capabilities will be given. [Preview Abstract] |
Thursday, March 24, 2011 3:30PM - 3:42PM |
X21.00004: Polarization Depend Soft X-ray Scattering of Anisotropic Organic Thin Films H. Ade, E. Gann, B. Collins, H. Yan, J. Cochran, M. Chabinyc Crystalline, semi-crystalline and liquid-crystalline organic materials have locally large anisotropic bond orientation statistics. This strongly impacts the mechanical, optical and electronic properties. For example, charge transport in organic thin films is often highly anisotropic and overall transport depends upon domain size, degree of order within domains, domain correlations, and the domain boundaries. Knowing the relative impact of all parameters is necessary for a detailed understanding of organic thin film transistors. - We demonstrate a novel scattering method to characterize such films: Polarization Dependent Soft X-ray Scattering (P-SoXS). In scattering, the linear dichroic absorption often exploited in x-ray microscopy is accompanied by strong linear dichroic dispersion, leading to large contrast based on bond orientation. This can not be achieved with hard x-rays or neutrons. We demonstrate P-SoXS on devices based on prototypical materials such as pentacene, poly(2,5-bis(3-tetradecyllthiophen-2-yl)thieno[3,2-b]thiophene) (pBTTT) and poly(3-hexylthiophene) (P3HT).~The use of linear or circularly polarized x-rays allows the bond orientation contrast to be switched on and off, respectively, which is very useful to characterize the correlated and individual domain size. [Preview Abstract] |
Thursday, March 24, 2011 3:42PM - 3:54PM |
X21.00005: Probing buried interfaces by Index-Matched Soft X-ray Scattering E. Gann, J. Seok, J. Cochran, M. Chabinyc, B. Collins, H. Ade Interfaces are often critical to function and performance in systems ranging from electronics to biology. Organic-organic interfaces are the location for charge transport in organic thin film transistors and exciton splitting in organic photovoltaics. Complete morphological characterization of buried interfaces is unfortunately difficult to achieve with conventional tools. We present a new method termed Index-Matched Soft X-ray Scattering (IM-SoXS). By matching the real part of the complex index of refraction of the top layer to that of vacuum through judicious choice of photon energy, we can minimize scatter from the top surface and substantially increase scatter from a buried interface, revealing both the spatial distribution and amplitude of the interfacial roughness. We demonstrate the method on samples with engineered and controlled interfacial roughness and provide examples of systems of scientific interest for which IM-SoXS should provide improved understanding of interface morphology and its relation to performance and function in systems. [Preview Abstract] |
Thursday, March 24, 2011 3:54PM - 4:06PM |
X21.00006: Lensless x-ray imaging in reflection geometry Daniel Parks, Sujoy Roy, Keoki Seu, Run Su, Joshua Turner, Weilun Chao, Erik Anderson, Stefano Cabrini, Stephen Kevan We report on the development of a technique for lensless x-ray imaging in reflection geometry. In an approach similar to Fourier transform holography, we use a set of apertures to define object and reference waves from light which has already scattered from the sample. Back propagation from the apertures gives the image at the sample plane. This technique can be used with extended objects without additional masking, and can be used in reflection and transmission geometries. The extension of lensless x-ray imaging into reflection geometry opens the possibility of imaging surfaces in thin films, buried interfaces in multilayers, or Bragg planes in single crystals. [Preview Abstract] |
Thursday, March 24, 2011 4:06PM - 4:18PM |
X21.00007: Determination of Total X-ray Absorption Coefficient using Non-Resonant X-ray Emission Andrew Achkar, Tom Regier, Eric Monkman, Kyle Shen, David Hawthorn Inverse partial fluorescence yield (IPFY) is a newly developed x-ray absorption spectroscopy (XAS) that utilizes non-resonant emission processes to measure the x- ray absorption of a material. Unlike XAS by traditional transmission, total electron yield and total fluorescence yield, IPFY is free of pinhole, saturation, and self-absorption effects. Moreover, IPFY exhibits a simple angle dependence that can be exploited to deduce the total x-ray absorption coefficient from a series of measurements performed with different experimental geometries. We quantitatively determine the total x-ray absorption coefficient of insulating NiO and NdGaO$_3$ single crystals at soft x-ray energies using this approach. [Preview Abstract] |
Thursday, March 24, 2011 4:18PM - 4:54PM |
X21.00008: Hard X-ray Microscopy with Multilayer Laue Lenses Invited Speaker: The possibility of imaging at near-atomic resolution using x-rays has been a dream ever since the short-wavelength nature of x-rays was demonstrated by von Laue and coworkers nearly a century ago. Even today the scientific impact of atomic-scale focusing of electromagnetic radiation would be deep and broad, because x-ray microscopy provides capabilities (ability to penetrate, sensitive and accurate elemental and structural information) that are complementary to other high-resolution microscopies. Although hard x-rays can in principle be focused to spot sizes on the order of their wavelength (0.1 nm), this limit has never been approached because of the difficulty in fabricating the optics. Multilayer Laue lens(MLL) is a novel diffractive optic for hard x-ray nano-focusing, which can be fabricated by sputter deposition of zone plate structure on flat substrate. According to the theoretical results, MLL is capable of focusing x-rays to well below 1 nm. We have demonstrated 2-dimensional focusing of hard x-rays with MLLs to a spot size of 25 nm x 27 nm with an efficiency of 2{\%} at a photon energy of 12 keV, while 1-dimensional focus of 16 nm has been achieved. In this talk, we will present an overview of MLL microscopy and recent accomplishments for the determination of chemical composition in nanoscale systems. Lastly, we will give the capabilities of MLL microscopy that have the potential to significantly advance materials science, nanoscience, bio-medical science and environmental science. [Preview Abstract] |
Thursday, March 24, 2011 4:54PM - 5:06PM |
X21.00009: Dynamical diffraction effects on beam focusing for x-ray back reflection from curved multi-plate x-ray crystal cavity Ying-Yi Chang, Sung-Yu Chen, Mau-Tsu Tang, M. Yabashi, Yi-Wei Tsai, Yu-Hsin Wu, Shih-Chang Weng, Chia-Hung Chu, Po-Yu Liao, Shih-Lin Chang We have recently observed diffraction enhanced beam-focusing in curved multi-plate x-ray crystal cavities of silicon using (12 4 0) as the back reflection at 14.4388 keV. The measurement on the transmitted x-ray beam size through the crystal cavities shows a reduced focal length and an extremely long beam waist at the focal point. This effect could be understood according to the dynamical theory of x-ray diffraction. Based on the consideration of the excitation of the dispersion surface for each curved crystal surface involved in the crystal device, beam focusing and beam splitting occur, leading to the observed focusing feature. Detailed dynamical calculations on the transmitted intensities at different positions near the focal point will be discussed. [Preview Abstract] |
Thursday, March 24, 2011 5:06PM - 5:18PM |
X21.00010: High-Resolution Thermal Expansion Measurements of Single-Crystal Sapphire for Application as X-Ray Backscattering Monochromator John J. Neumeier, I. Sergeev, D. Bessas, R.P. Hermann We report measurements of the thermal expansion of high-purity single crystal sapphire along the $a$ and $c$ directions. The data were acquired using a thermal expansion cell that is constructed of fused silica with a relative resolution of approximately 3x10$^{-9}$. Comparison will be made to existing literature values determined from dilatometry and high-resolution x-ray diffraction. This project's main goal is the use of sapphire as x-ray backscattering monochromator for phonon spectroscopy using nuclear inelastic scattering. Tuning of the monochromator is done by varying the sapphire temperature, and the new thermal expansion values will improve the energy calibration. [Preview Abstract] |
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