Measurement of the surface excitation probability of medium energy electrons reflected from Si, Ni, Ge and Ag surfaces

Reflection electron energy loss spectra (REELS) are presented for medium energy (200 eV to 5 keV) electrons backscattered from Si, Ni, Ge and Ag surfaces. Multiple bulk inelastic scattering is eliminated from the experimental spectra and the differential surface excitation probability is retrieved from the resulting spectra. The differential as well as the integral surface excitation probabilities are compared with available theoretical results and experimental data published earlier. A material parameter is derived from the measurements that describes the dependence of the average number of surface excitations experienced in a single surface crossing on the electron energy and direction of surface crossing. While the shape of the distribution of energy losses in a single surface excitation is in reasonable agreement with theory, the integral surface excitation probability, i.e. the number of surface excitations experienced by the probing electron during a single surface crossing, exhibits a significant scatter when comparing results from different sources.