Penetration range and backscattering ratio of low-energy electrons in metals

The accuracy of the Ashley's optical-data model [J.C. Ashley, J. Electron Spectrosc. Relat. Phenom. 50 (1990) 323] for describing the energy loss rate and inelastic mean free path of low-energy electrons in Al and Cu has been examined through the use of Ashley's model for calculating the electron penetration range. The latter has also been calculated using the empirical expressions reported by Iskef et al. [Phys. Med. Biol. 28 (1983) 535] and Gryzinski excitation function. The resulting range of penetration is used for determining the electron backscattering coefficients via the use of Vicanek and Urbassek theory [Phys. Rev. B 44 (1991) 7234] where the transport cross-sections are obtained from Rouabah et al. [Appl. Surf. Sci. 255 (2009) 6217] approximation. Besides the electron backscattering coefficients have been calculated from Monte Carlo simulation in which the inelastic scattering processes are handled using Ashley dielectric approach. It is found that the use of Ashley's optical model via Monte-Carlo method gives backscattering coefficients more accurate than those obtained via Vicanek and Urbassek theory. This confirms the accuracy of Ashley's optical model and shows that the Monte-Carlo method is much more accurate and precise than the Vicanek and Urbassek semi-empirical approach. (C) 2012 Elsevier B.V. All rights reserved.