Diffraction Studies of Epitaxy

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This is a study of the effects of the structure of the surface of gallium arsenide substrates upon the molecular beam epitaxial growth of compound semiconductors and thin films of metals. The study utilizes reflection high-energy electron diffraction and transmission electron microscopy to characterize the structures. The effects of misorientation of the crystals on the stability of growth and the diffusion of atoms will be determined. The results of the research will enable the formulation of a model for the epitaxial growth of compound semiconductors. Under the previous grant (DMR-8319821). Professor Cohen made significant advances in the field: (i.) improved understanding of reflection high-energy electron diffraction processes in these materials, e.g., determination of the effects of interference on angular dependence of diffraction oscillations, (ii.) measurement of surface diffusion on gallium arsenide, (iii.) determination of means to control the evaporation and growth of gallium arsenide on the level of individual atomic layers, (iv.) measurement of the thickness that indium gallium arsenide thin films can be grown before the onset of strain-related defects. These and other advances are described in more than seven scientific publications. Professor Cohen is acknowledged as one of the leading scientists in the field. The facilities and the institutional environment are excellent for the performance of the research and training of students. His research under the previous NSF grant has been classified by his peers as the pioneering work in the field. The program includes a Research Experience for Undergraduates Supplement for two undergraduate students to get hands-on experience in research. It is hoped that this experience will serve as a stimulus to attract highly-gifted students into research and teaching careers as well as to contribute to the overall goals of this program.