The proposal is for the study of structure of surfaces using the technique of reflection electron microscopy. The objective of the study is twofold: to further develop the technique, which was originally developed by the PI, i.e., to better understand the nature of the information provided by reflection electron microscopy (REM) in terms of atomic structures and defects, and to apply the technique to several technically interesting materials-crystal surfaces, III-V compounds, and interfaces. The approach thus is both to apply the REM technique to materials with known surface structure and defects, and to explore the potential of this relatively novel technique for providing information on the surface structure of a variety of interesting materials. The results should be of both scientific interest, in the development of a new tool for surface analysis, and of practical interest, in providing information on the structural features on the surfaces of several technically important materials. The results should be relevant to both electronic applications, where the surface properties dominate many device properties, and in the areas of sintering, catalysis and crystal growth, where surface effects are also critical in determining the nature of the final material or in its performance.