Microdiffraction, stem imaging and ELS at crystal surfaces

Abstract

The interaction of electrons with the flat face of a small crystal, when the beam is almost parallel to the face, is strongly influenced by the form of the potential field at the surface and the excitations associated with the surface. Microdiffraction patterns show evidence of refraction displacements from which information on the form of the potential distribution can be deduced. Channeling of the electrons along the surface gives additional spots in the microdiffraction patterns and fringes of varying periodicity in the image. The generation of transition radiation as the electron is accelerated in the vicinity of the surface gives rise to prominent characteristic features in the 0–30 eV range of the energy loss spectra. Also the peaks associated with excitations of surface electronic states are strong.