Elastic electron backscattering from surfaces in selected angular ranges

Abstract

Theoretical models describing the probability of elastic electron backscattering from surfaces require knowledge of the elastic scattering cross-sections for atoms constituting the solid. It has been shown that these cross-sections depend on the potential describing the interaction of electron with the scattering centre. The largest differences between cross-sections, which may reach 600%, occur in the angular range of deep minima. These angular ranges were selected for experimental and theoretical determination of the ratios of elastic backscattering probabilities. It turned out that the calculated ratios depend strongly on the potential. Mean percentage difference due to the use of elastic scattering cross-sections originate from the Thomas–Fermi–Dirac (TFD) or Dirac–Hartree–Fock (DHF) potentials is 11.7%. Difference between theoretical and experimental ratios is larger; on average this difference is equal to 25.5 and 29.2% for TFD and DHF potentials, respectively. After taking into account the surface energy losses, these differences decrease to 19 and 23.5%, respectively. The IMFP values resulting from elastic peak electron spectroscopy, measured in geometries corresponding to deep minima, may be burdened with similar uncertainities due to the fact that the interaction potential between electron and the scattering centres of a solid is unknown, and may be different from the DHF and the TFD potentials.