Experimental determination of electron inelastic scattering cross-sections in Si, Ge and III-V semiconductors

Elastic peak EPES-REELS spectra have been measured on polySi, aGe, GaAs, GaP, InSb and InAs samples for primary energies E=0.2-5 keV, using the ESA 31 HSA spectrometer. The investigated specimens exhibit plasmon dominated loss spectra. We applied two approaches to separate surface and bulk plasmons. Firstly the normalized K( E, E _L) λ _i( E) inelastic scattering spectra, deduced from REELS (reflection electron energy loss spectroscopy) experiments, are fitted at E= E _p1l bulk plasmon energy. They determine the λ _i inelastic mean free path (IMFP) of electrons and their surface excitation parameter P _s( E) as well. The bulk plasmon peak dominates at E=5 keV. It is described by the 3 parameters Lorentzian-type formula of Tougaard. Above E _p11 the K( E, E _L) λ _i spectra are overlapping. Composing the difference between the normalized experimental spectra and the spectrum at 5 keV results in the surface plasmon contribution after renormalization. P _s( E) is given by the ratio of the integrated surface plasmon with the elastic peak. Secondly we used a direct Monte Carlo simulation, assuming that surface and bulk energy losses are independent processes. In our model a shape of energy loss function based on optical data was used. Surface loss function intensities are fitted according to the measured spectra and P _s( E) values are directly obtained from the simulation. The experimental REELS spectra of Si resulted in good agreement with Monte Carlo simulation. The P _s( E) parameters of Si and Ge resulted in reasonable agreement with the relationship and parameter described by Werner.