Analysis of surface structural defects using LEED and RHEED

Abstract

Surface structural defects can have an important influence on a wide variety of phenomena at surfaces, including electronic, chemical, transport, and mechanical properties. Diffraction techniques that are sensitive to the surface can, in principle, be used to study surface structural defects, in the same manner that X-ray diffraction has been used for the analysis of bulk defects and finite-size phenomena. Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED) are two techniques that can be used in this way. By measuring the angular distribution of intensity in diffracted beams, different types of surface defects can be distingueshed and quantified. Recent progress in the use of LEED to analyze steps, finite-size overlayer domains, surface strain, and mosaic effects is reviewed. In particular, overlayer studies present challenging and interesting problems, because they can involve the combination of finite-size effects in the overlayer with the scattering from a coherent substrate. Examples of defect analysis on several surfaces are given. Recently renewed interest has been shown in the use of RHEED for surface defect studies. The capabilities for defect studies of conventional RHEED, as found in crystal surface studies or epitaxial growth experiments, are described and compared to those of LEED.