Reflection Microscopy in a Scanning Transmission Electron Microscope

Abstract

Reflection Electron Microscopy (REM) has mainly been used to observe flat, clean and crystalline surfaces with the aim of imaging monatomic steps and surface dislocations. These features can be qualitatively understood and more quantitative theories are currently being developed. Most REM studies have concentrated on semiconductors or noble metals on which it is relatively easy to prepare good crystalline surfaces but it is desirable to extend REM to look at a greater variety of samples. This would include surfaces that are chemically more reative, rougher or less crystalline and less homogeneous, such as those with overlayers or oxides. Most of the previous work has used conventional transmission electron microscopes (CTEMs) but the analytical facilities and generally better vacuum of scanning transmission electron microscopes (STEMs) make them a potentially powerful tool for surface studies. The results presented in this paper were obtained from a V.G.HB501 STEM and show how REM can be used to examine surface reactions and inhomogeneous samples.