Investigations of Au Segregation in AuNi Alloys by the Line Shape Analysis of Photoelectron Spectra

Abstract

The surface segregation of Au in Au5Ni95 polycrystalline alloy is studied applying the line shape analysis, known as the fuzzy k-nearest neighbour rule, to the selected X-ray photoelectron and X-ray induced Auger spectra. Each line, characterised by the kinetic electron energy exhibited in the particular transition, samples the depth described by the mean escape depth depending on the inelastic mean free path of electron in the investigated material and the geometry of the measurement. The following electron transitions in the electron kinetic energy range 216.6–1486.6 eV are analysed: Au N5N67V , Ni 2p, Ni L2M23M45–Ni L3M45M45, Au 4d, Au 4f and the valence band transitions (overlapping Au 5d6s and Ni 3d4s transitions). The results of the quantitative analysis using the fuzzy k-nearest neighbour rule are compared to the results of quantitative analysis by the multiline approach which applies the Au 4f and Ni 2p photoelectron transitions. Both methods demonstrate Au surface segregation starting at the temperature above 200◦C. The line shape analysis was shown to be applicable for quantification of the surface region with possibility of investigating the in-depth non-uniform concentration profiles.