Monte Carlo simulation of energy loss of electrons backscattered from solid surfaces

A Monte Carlo model developed for simulation of electron scattering in solids is presented here. The method is based on the spatially varying differential inverse inelastic mean free path (DIIMFP), calculated using the dielectric response model proposed by Li and co-workers [Y.C. Li, Y.H. Tu, C.M. Kwei, C.J. Tung, Surf. Sci. 589 (2005) 67]. This direct spectrum simulation model is able to take into account the reduction of the bulk plasmon excitation probability close to the surface boundary and the change of the surface-plasmon excitation probability as a function of the position (both side of the surface) and the velocity of the moving electron. REELS spectra of solid Cu were simulated by the presented MC model for 500-3000 eV primary electron energies and for a given geometry. Comparing the simulated and the experimental spectra, a good agreement can be seen. Since the presented Monte Carlo model is able to separate the bulk and the surface excitation modes inside the sample, the spectral contributions of the clear single bulk excitation and the single surface excitation inside the sample are analysed as well.