Diffraction from Disordered Surfaces: An Overview

Reflection high-energy electron diffraction (RHEED) is just one of several diffraction techniques (electron, atom, or x-ray) that have the capability for investigating the crystallography and microstructure of surfaces and very thin films. Diffraction gives a statistical view of disorder rather than a local picture, as would be obtained, for example, in a scanning tunneling microscope. Many processes occurring at surfaces, such as growth, phase transformations, the formation of steps, and so on, involve deviations from perfect order that are stochastic in nature. For such processes a statistical view is appropriate and is directly relatable in a quantitative way to the mechanisms that are involved. All such phenomena can be broadly classified under surface disorder. This paper attempts to review how diffraction, and in particular RHEED, can be used to investigate surface disorder. The intent here is to provide a simple, physically reasonable, pedagogical approach to this subject.[1] We somewhat artificially divide the paper into static phenomena (Sec. II), time-dependent phenomena (Sec. III), and (Sec. IV) issues that complicate the simple picture presented in Secs. II and III. In this section we treat preliminary topics.