Determination of the electron inelastic mean free path in some binary alloys for application in quantitative surface analysis

Abstract

Quantitative surface- and thin film analysis by electron spectroscopies (AES, XPS, EELS) requires the knowledge of one of the most important parameters of the electron transport such as the inelastic mean free path (IMFP) of electrons. Numerous data on the IMFP have been already published, mainly for elemental solids and some inorganic and organic compounds. However, the IMFPs for some binary alloy systems are still lacking. Although IMFP values for complex solids can be calculated from predictive formulae, IMFPs can be also measured experimentally by elastic peak electron spectroscopy (EPES). The present work is dealing with the experimental determination of the IMFP in selected binary alloys, i.e. Au x Cu 100− x ( x=25, 75 at.%), Au x Pd 100− x ( x=10, 90 at.%) and Au x Ni 100− x ( x=5 at.%) within the 200–2000 eV range. The relative EPES experiments have been performed using a double-pass CMA spectrometer and the Ni standard. The measured IMFPs were compared with IMFPs calculated from the TPP-2M predictive formula. The RMS deviation from IMFP values calculated from the TPP-2M equation was 0.6–2.5 Å depending on the alloy surface composition, and it was smallest for the Au 5Ni 95 alloy. The mean percentage deviation from the TPP-2M IMFPs was 4.3–17.6%.