A note on extracting electronic stopping powers of solid matter for heavy ions from energy loss spectra recorded in transmission geometry

Abstract

We describe and compare two techniques to extract the electronic stopping power of solid materials for energetic ions from energy loss spectra recorded in transmission geometry. Particular attention is attributed to the contribution of the nuclear energy loss to the total energy loss. Energy loss spectra were measured for slow N⁺ and Ar⁺ projectiles transmitted through 200 nm (N⁺ projectile) and 50 nm (Ar⁺ projectile) thick SiC membranes. The measured energy losses are successfully separated into electronic and nuclear losses with the help of a Binary Collision Approximation (BCA) code. The simulations show that the nuclear stopping power in any forward scattering geometry strongly deviates from SRIM predictions. Electronic stopping powers are calculated by two different iterative processes, yielding electronic stopping power at the mean energy or the energy for the mean stopping. The accuracy of the electronic stopping functions gained from these methods is verified by controlling whether the BCA code predicts the measured energy losses correctly using these functions for the simulated electronic stopping power. We show that both algorithms are suitable for extracting the electronic stopping power, even if it shows a pronounced non-linear energy dependence and if the contribution from elastic scattering to the energy loss is large. We compare their performance and show that simultaneous iteration of the electronic and nuclear stopping power provides the most accurate results.