Determination of the electron inelastic mean free path in solids from the elastic electron backscattering intensity

Abstract

AbstractThe inelastic mean free path (IMFP) of electrons in solids is an important parameter needed for quantitative applications of electron spectroscopies: X‐ray photoelectron spectroscopy and Auger electron spectroscopy (AES). The IMFP values published for compounds or alloys are rather limited, and in general case, the predictive formulas must be used. Unfortunately, accuracy of these formulas may be rather low in some cases. There is an obvious need for a simple method that conveniently provides the IMFP values for a studied solid. Such conditions are satisfied by the method that makes it possible to derive the IMFP values from the measured elastic backscattering probability. The present report contains a concise introduction to this method; the main features of such an approach are briefly reviewed and discussed. The method, with some caution, can be applied to any solid, although the conducting or the semiconductor samples are recommended to avoid charging effects. In contrast with the method involving deposition of overlayers, the IMFP values derived from the elastic backscattering intensity are in agreement with the definition supported by American Society for Testing and Materials (ASTM). The measurements can be made using typical electron spectrometers in situ for samples submitted to other studies. Finally, the measurements are nondestructive. The main problem of this method is the complexity of the theoretical model describing multiple electron scattering events in the solid. To facilitate calculations, an extensive user‐friendly software packet, EPES has been developed. One of the functions of this packet is to determine, from the Monte Carlo (MC) simulations, the so‐called calibration curve, i.e. the dependence of the backscattering probability on the input value of the IMFP. Calculations can be performed for any experimental configuration, and for electron energies ranging from 50 to 10 000 eV. The theoretical model requires knowledge of the total and differential elastic scattering cross sections (DCS). These parameters can be imported from all versions of the NIST Database 64. Copyright © 2005 John Wiley & Sons, Ltd.