Fluctuation X-ray microscopy: a novel approach for the structural study of disordered materials |
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Authors: | L. FAN&Dagger ,D. PATERSON&dagger ,I. McNULTY&Dagger ,M. M. J. TREACY,& J. M. GIBSON&Dagger |
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Affiliation: | Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL 60439, U.S.A.;Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287, U.S.A.;Australian Synchrotron Project, Major Projects Victoria, 800 Blackburn Road, Clayton, VIC 3168, Australia |
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Abstract: | Measuring medium‐range order is a challenging and important problem in the structural study of disordered materials. We have developed a new technique, fluctuation x‐ray microscopy, that offers quantitative insight into medium‐range correlations in disordered materials at nanometre and larger length scales.In this technique, which requires a spatially coherent x‐ray beam, a series of speckle patterns are measured at a large number of locations in a sample using various illumination sizes. Examination of the speckle variance as a function of the illumination spot size allows the structural correlation length to be measured. To demonstrate this technique we have studied polystyrene latex spheres, which serve as a model for a dense random‐packed glass, and for the first time have measured the correlation length in a disordered system by fluctuation X‐ray microscopy. We discuss data analysis and procedures to correct for shot noise and detector noise. This approach could be used to explore medium‐range order and subtle spatial structural changes in a wide range of disordered materials, from soft matter to nanowire arrays, semiconductor quantum dot arrays and magnetic materials. |
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Keywords: | Coherent scattering disordered materials fluctuation X-ray microscopy medium-range order speckle |
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