Quantitative auger electron analysis of homogeneous binary alloys: Chromium in gold

Abstract

Quantitative Auger electron analysis of Cr/Au alloys with up to 20% Cr has been accomplished. The surface composition of scribed areas were compared to bulk compositions and it was shown that corrections for variation of density, escape depth, and electron backscattering must be included; these corrections change the measured surface Cr concentrations by approximately 15%. Alloy sputter yield ratios have been calculated from surface concentrations after sputtering with Ar or Ne (0.5, 1.0, 1.5, and 2.0 keV). The sputter yield ratio of Cr to Au was 0.5 at 1% Cr (significant preferred sputtering) but was near unity at 20% Cr (no preferred sputtering). The sputter yield ratio was nearly independent of ion species and ion energy. The 2 keV argon ion sputter yields for pure Cr and Au were determined to be 2.0 and 7.9 atoms/ion, respectively. However, the 2 keV argon ion sputter yield for Au in the alloys drops rapidly from 7.9 atoms/ion for pure Au, to 5 atoms/ion at 10–20% Cr. The sputter yield for Cr in alloys (5 atoms/ion) is relatively independent of composition and is 2.5 times higher than the yield of pure Cr. No simple model is known by which pure elements sputter yields could be used to predict alloy sputtering behavior.