"Coherent X-ray Scattering Studies of Dynamic Crystal Surfaces"

ND Energy invites all Notre Dame researchers to the following discussion by Dr. Carol Thompson, Professor in the Department of Physics at Northern Illinois University.  

X-rays provide powerful tools for in-situ time-resolved studies of interface and surface evolution during materials processing.  The penetrating nature of high-energy x-rays allows investigations using realistic process environments and conditions, and their short wavelength provides sensitivity to atomic-scale structures and correlations.  A new development in x-ray science is the use of coherent x-ray beams for techniques such as x-ray photon correlation spectroscopy and coherent diffraction imaging.  These coherent x-ray techniques probe dynamics.  For equilibrium crystal surfaces at high temperature, x-ray ‘speckle’ correlations should reveal the dynamics of defects such as steps and adatoms.  For non-equilibrium surfaces as during crystal growth, the two-time and other higher-order correlation functions extracted from x-ray photon correlation spectroscopy may elucidate aspects of island nucleation, step-edge barriers, and transport mechanisms.  The expected increase in coherent flux at high x-ray energy delivered by facilities such as the Advanced Photon Source at Argonne National Laboratory opens up the possibility that these novel techniques can be applied to in-situ studies of dynamic surfaces in complex process environments.  With this goal, an Argonne-NIU collaboration has begun exploring how coherent x-ray studies can be applied to studies of crystal growth.  In this talk I describe these new developments in x-ray studies, and present our simulations and initial measurements of x-ray coherent scattering from dynamic crystal surfaces under in-situ conditions within a metal-organic chemical vapor deposition chamber.  

Work supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Sciences and Engineering.

Carol Thompson, Professor of Physics at Northern Illinois University, is an experimental materials physicist. She started her scientific career at IBM Research Laboratory in New York, moving from there to Polytechnic University in Brooklyn and subsequently to NIU. She received her Ph.D. in Physics from University of Houston, M.S. in Materials Science and Engineering at Stanford University, and B.S. in Engineering and Applied Science at Caltech. 

Hosted by:  Dr. Subhash L. Shinde, Associate Director, Center for Sustainable Energy at Notre Dame

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