Electron inelastic mean free paths (IMFPs) in binary Au-Cu alloys determined by elastic peak electron spectroscopy

Numerous data on the inelastic mean free path (IMFP) of electrons have been published, mainly for elemental solids and some inorganic and organic compounds. However, there is limited information available for IMFP values of binary alloy systems. Although IMFP values for different energies can be calculated for alloys from predictive formulae, IMFPs can be measured experimentally by elastic peak electron spectroscopy (EPES). In the present work, the IMFPs for three Au-Cu alloys - Au (25 at.%)-Cu (75 at.%), Au (50 at.%)-Cu (50 at.%), Au (75 at.%)-Cu (25 at.%)- were determined for the first time. The EPES experiments have been performed in three laboratories using spectrometers with different geometries and energy resolutions. The experiments were performed with the use of an Au standard (relative measurements) and without a standard material (absolute measurements). Two Monte Carlo algorithms were used to calculate the IMFPs. The IMFP energy dependence for the alloy samples has been obtained in the primary electron energy range 200-2000 eV. The measured IMFPs were compared with IMFPs calculated from two predictive formulae, i.e. the TPP-2M equation of Tanuma et al. and the G-1 equation of Gries. The scatter between the measured IMFPs and those calculated from the predictive formulae has been analysed statistically. The root-mean-square deviation from IMFP values calculated from the TPP-2M equation was 1.81-5.97 Angstrom, depending on the alloy surface composition and the particular EPES measurement, and it was smallest for the Au25CU75 alloy. The mean percentage deviation from the TPP-2M IMFPs was similar to 27%. Copyright (C) 2001 John Wiley & Sons, Ltd.