Inelastic Scattering in Low-Energy Electron Diffraction from Silver

Abstract

In a low-energy electron diffraction experiment on Ag (111) we have studied the inelastically scattered current of electrons having lost $\lesssim 10$ eV. We show quantitatively that this current, which is strongly peaked in the directions of Bragg reflections, arises from a two-step process involving both an elastic and an inelastic scattering. A model based on the two-step process is developed and then compared with experimental results. The model allows one to separate the Bragg and phonon components of the inelastic scattering and to extract an energy-loss spectrum which is independent of the elastic scattering. The structure, intensity, angular widths, and angle-of-incidence dependence of the energy-loss spectra are compared with the predictions of a dielectric-constant energy-loss formalism using known optical constants. The comparison, which includes both surface and volume losses, shows reasonable agreement and indicates that the surface losses predominate.