IMFP measurements near Au–Ni alloy surfaces by EPES: indirect evidence of submonolayer Au surface enrichment

Abstract

Abstract Electron inelastic mean free paths (IMFPs) in Au x Ni 1− x alloy samples ( x =1, 2 and 5 at.%) were determined experimentally by elastic peak electron spectroscopy. In addition, we also explored the effect of the Au surface segregation in the determination of the IMFP. The measurements were performed with respect to a Ni standard (relative measurements) and without a standard material (absolute measurements). Two Monte Carlo (MC) algorithms were used to calculate the IMFPs. The energy dependence of the IMFP for alloy surfaces with both a nominal composition and enriched in Au up to ∼25 at.% was obtained in the electron energy range 200–2000 eV. The measured IMFPs were compared with IMFPs calculated from the TPP-2M predictive formula. It was found that the IMFPs for the studied alloys determined from absolute measurements were considerably lower than the calculated IMFP values and IMFPs determined from relative measurements as well. This deviation can be explained by the surface composition change since the experimental IMFPs depend considerably on the Au surface concentration in the low energy electron range 200–1000 eV.