Micro Grain Analysis in Plastically Deformed Silicon by 2nd-Order X-Ray Diffraction
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.511
Micro Grain Analysis in Plastically Deformed Silicon by 2nd-Order X-Ray Diffraction 1
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Gabriel Dina , Ariel Gomez Gonzalez , Sérgio L. Morelhão , Stefan Kycia
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Department of Physics, University of Guelph, Guelph, Ontario, Canada
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Institute of Physics, University of São Paulo, São Paulo, SP, Brazil
ABSTRACT
Second-order diffraction (SOD) of x-rays refers to all diffraction processes where the photons reaching the detector have been diffracted twice within a crystal lattice. By measuring the two dimensional intensity profile of SOD, it is possible to distinguishing rescattering processes taking place inside each grain (perfect crystal domain) or in between grains. These two SOD regimes, usually called dynamical and kinematical, respectively, are ruled by size and relative orientation of the grains. In this work, we demonstrate how to explore SOD phenomena to understand the micro scale grain structure in plastically deformed silicon single crystal.
INTRODUCTION Plastic deformation of otherwise perfect crystals is an unlikely process to be used for the production of optical x-ray components due to the detrimental impact of the resulting mechanically induced defects on the coherence of the diffracted x-ray waves [1]. However, if controlled, such defects in plastically deformed crystals can enable optics solutions that may outperform current options. Understanding the micro-grain structure of plastically deformed crystals is a key for this goal. Particularly interesting optical components for high energy x-rays are Laue monochromators, which are monochromator crystals based on transmission diffraction as opposed to reflection-like diffraction from a single surface. At synchrotron beamlines Laue monochromators are preferred over standard Bragg monochromators when using high energy x-rays above 30keV. Advantages of using a bent Laue monochromator include increasing the rocking curve width, and hence, the intensity, as a result of the spread in d-spacing produced by both strain and change in Bragg plane orientation [2,3]. Furthermore, bent Laue monochromators do not demand large beam footprints on the
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crystal and allow focusing of the x-ray beam, resulting in increased intensity on a sample or detector. We have been exploring the possibility of producing plastically deformed Laue crystals versus the more widely used elastically bent design. Plastically deformed crystals have the benefits of not needing complicated bender mechanisms and providing the freedom to choose any sagittal and meridional curvature corresponding to the desired shape that meets the exact optical specifications [4]. We have developed high quality curved plastically deformed silicon Laue monochromator crystals. Silicon (
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