Model for quantitative analysis of reflection-electron-energy-loss spectra

Two models to reproduce experimental inelastic-electron-scattering cross sections determined from reflection-electron-energy-loss spectroscopy (REELS) are considered. The models take into account the momentum transfer in the inelastic processes. Inputs for the models are the dielectric function and the inelastic electron mean free path, which are both taken from previous works. It is found that a model that takes into account the k dependence of the dielectric function and the effect of the field set up by the incoming electron on the outgoing electron gives the best description. Without any adjustable parameters, a reasonable quantitative agreement between experimental and theoretical cross sections is found for Al, Ti, Fe, Cu, Pd, Ag, and Au in a wide energy range (175--10 000 eV). For a backscattered electron, the effective inelastic mean free path is found to depend strongly on the path length. A method to determine the dielectric function from REELS spectra is suggested.