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 comp ounds. However, there is limited information available for IMFP values of b inary alloy systems. Although IMFP values for different energies can be cal culated for alloys from predictive formulae, IMFPs can be measured experime ntally by elastic peak electron spectroscopy (EPES). In the present work, t he IMFPs for three Au-Cu alloys - Au (25 at.%)-Cu (75 at.%), Au (50 at.%)-C u (50 at.%), Au (75 at.%)-Cu (25 at.%)- were determined for the first time. The EPES experiments have been performed in three laboratories using spect rometers with different geometries and energy resolutions. The experiments were performed with the use of an Au standard (relative measurements) and w ithout a standard material (absolute measurements). Two Monte Carlo algorit hms were used to calculate the IMFPs. The IMFP energy dependence for the al loy samples has been obtained in the primary electron energy range 200-2000 eV. The measured IMFPs were compared with IMFPs calculated from two predic tive formulae, i.e. the TPP-2M equation of Tanuma et al. and the G-1 equati on of Gries. The scatter between the measured IMFPs and those calculated fr om the predictive formulae has been analysed statistically. The root-mean-s quare deviation from IMFP values calculated from the TPP-2M equation was 1. 81-5.97 Angstrom, depending on the alloy surface composition and the partic ular 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.