Determining electron inelastic mean free paths by iterative Monte Carlo analysis of the backscattered electron spectrum

Abstract

This study presents a novel method for extracting inelastic mean free paths (IMFPs) of electrons in solids from the backscattered electron spectrum (BES) using iterative Monte Carlo simulations. In our approach, the IMFP is parameterized using the Tanuma–Powell–Penn (TPP-2M) formula and a classical trajectory Monte Carlo simulation is used to model electron transport processes and generate a theoretical BES. Through an iterative process, we optimize the TPP parameters to achieve the best fit between the simulated and experimental spectra over a wide energy range. This method was applied to determine the IMFPs of 25 targets, such as C (graphite), Mg, Al (100), Al (111), Si, Ti, V, Cr, Fe, Co, Ni, Cu (100), Cu (110), Cu (111), Mo, Ru, Rh, Ag, Sn, W, Re, Ir, Pt, Au, and Bi, in the energy range from 200 to 4900 eV, using a comprehensive experimental BES data set. The results demonstrate that the IMFPs obtained with our BES method show an average root-mean-square deviation of approximately 15% from values calculated using the full-Penn algorithm and the standard TPP-2M formula. This approach not only provides a new technique for the IMFP measurement but also offers a novel perspective for utilizing the continuous background signal in surface electron spectroscopy, which is typically overlooked.