Monte Carlo simulation study of reflection-electron-energy-loss-spectroscopy spectrum

The study of inelastic scattering of electrons moving in a surface region is important to a comprehensive understanding of the basic process of electron-surface interaction in a surface electron spectroscopy. A numerical formalism was previously developed to calculate the complex electron self-energy near a metal surface. This inhomogeneous self-energy in the depth about the surface is formulated in terms of a wave-vector-dependent dielectric function which is obtained from the optical data. In this paper, we present a numerical calculation result on the spatially varying differential inelastic scattering cross section and the inelastic mean free path. Combining this inelastic scattering cross section and the Mott cross section for electron elastic scattering has led to a Monte Carlo simulation model for electron interaction with a surface. To verify this simulation model we have carried out simulations of rcflection-electron-energy-loss spectroscopy (REELS) spectra for Au and Si, and compared the results with the experimental spectra. The comparison of the spectra shape for Au is quite reasonable. Several surface features for Au having lower-energy losses have been clearly identified, while the higher-energy loss peaks are shown to be mainly of the bulk feature. The simulation result indicates that the energy-loss process of electron in the vacuum region after leaving from a surface makes a dominant contribution to the surface excitation peaks observed in a REELS spectrum.