Electron Optical Studies of Crystal Disorders, Defects and Surfaces

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This grant is a renewal for research by Professor John Cowley on the use of high resolution electron microscopy for the investigation of the structure of defects and surfaces of ceramic and electronic materials. The current research concentrates on a range of new techniques and the further advancement of established techniques for the more detailed atomic description of the structures and chemical compositions of crystal surfaces and atomic disorder in thin films and small particles. The effects of surface resonance channelling, which confine the electron beam to the topmost lines or planes of atoms on crystal surfaces will be investigated for the reflection electron microscope. These effects are observed in the Kikuchi line patterns in reflection high energy electron diffraction, and they provide for the basis for the technique developed by this group called electron energy loss spectroscopy. These new techniques allow micro-chemical and atomic analysis of surface monolayers. These techniques are being applied to studies of surfaces of oxide ceramics (e.g. magnesium oxide) and semiconductors (e.g. silicon and gallium arsenide). Two new ultra high vacuum high resolution electron microscopes are to be used for this study. The research of Professor Cowley has been at the leading edge of high resolution electron microscopy for years. It has led to several of the techniques in use worldwide today. The present research will continue to advance these techniques, and their use in characterization of ceramics and electronic materials on the atomic scale. This group at Arizona State University continues to train graduate students and post doctoral students in the use of these advanced analytical techniques.