Assessment of the Inelastic Scattering Model in Monte-Carlo Simulations

Abstract

Electron backscattering and transmission through thin films have been simulated by the Monte-Carlo method. Instead of the backscattering coefficient we calculated Niedrig’s coefficient C _N = η/(N ₁ Z ² d _1/2), where rj is the backscattering coefficient, N ₁ is the number of atoms in a volume unit, Z is atomic number, and d_1/2 is the film thickness giving a value for the backscattering coefficient of half that for a bulk specimen. In the case of electron transmission, the most probable energy loss, W _p , was found. The calculations were carried out for Al, Cu, and Au, the former for 10–100 keV primary energy and in the 50–2000 µg/ cm² film thickness range, the latter for a primary energy of 20keV and in the 150–650 µg/cm² film thickness range. Tables calculated by means of the Hartree-Fock atom function were used for simulating elastic scattering, and several models of inelastic scattering were employed — the modified Bethe model and models with exponential and hyperbolic shapes of energy losses (with or without electron deflection at scattering). Our findings were compared with published experimental results. In the case of Niedrig’s coefficient, an exact comparison was impossible. Nevertheless, for the systems studied best agreement between calculated and experimental values of W _p was reached when using the model containing the hyperbolic shape of energy loss, (usually without deflection during scattering). This result provided an opportunity, when combined with previous assessments of elastic models, to improve the accuracy of calculation for future employment of the Monte-Carlo method.