Inelastic mean-free paths and surface excitation parameters by absolute reflection electron-energy loss measurements

Abstract

An analytical approach is proposed for simultaneously determining the inelastic mean-free path (IMFP), the surface excitation parameter (SEP), and the differential SEP (DSEP) in absolute units from an absolute reflection electron energy loss spectroscopy (REELS) spectrum under the assumption that the normalized differential inelastic mean-free path for bulk excitations and the elastic scattering cross section are known. This approach was applied to an analysis of REELS spectra for Ni, and the IMFP, SEP, and DSEP in Ni for $300--3000\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ electrons were determined. The resulting IMFPs showed good agreement with those calculated using the TPP-2M predictive equations and with those calculated from optical data. The deduced DSEPs show a reasonable agreement with those theoretically predicted. The obtained SEPs were compared with those calculated using several predictive equations. The present SEP results agreed well with the Chen formula with a material parameter proposed for Ni. The present approach has high potential for the experimental determination of IMFPs, SEPs, and DSEPs in absolute units.