Calculations of electronic excitation by protons and α particles in silicon

Abstract

This paper presents a method of calculating the valence electron contribution to the stopping and interaction cross sections of swift ions in matter using linear response calculations of the dielectric function in crystals. The ab initio response function is used to calculate excitations at low energy and momentum transfers to account for material-specific effects, while higher energy and momentum transfers use a free electron gas response for increased computational efficiency. The ECPSSR method for computing core cross sections is modified to allow predictions of the core contribution to electronic stopping. The charge distribution by entrained electrons is explicitly modeled to account for the additional screening beyond linear response. We use the methods developed to predict the electronic stopping of protons and $\ensuremath{\alpha}$ particles in silicon and compare to measured values.