XPS excitation dependence of measured cobalt 2 p[formula omitted] peak intensity due to auger peak interference

Abstract

Quantitative X-ray photoelectron spectroscopy (XPS) analysis of cobalt-nickel (80:20) alloy material has revealed that the observed Co/Ni ratio using Al Kα excitation is about 20% higher than that observed with Mg Kα excitation. The ratio observed with Mg Kα is correct to within experimental error. Analysis of pure cobalt metal shows that the apparent increase in the alloy ratio with Al Kα excitation is primarily due to interference in the Co 2 p 3 2 spectral region by the cobalt L 3 M 23 M 45 Auger peak, which causes the Co 2 p 3 2 integrated intensity to be overestimated by about 15%. Analysis of fully oxidized cobalt shows that the Auger peak no longer significantly affects the measured Co 2 p 3 2 intensity, due to a chemical shift in the XPS peak and a change in structure of the Auger peak. Thus the contribution of the Auger peak to the measured Co 2 p 3 2 intensity varies with the degree of oxidation, and this should affect the interpretation of data in analyses of mixed oxide-metal systems, such as sputter profiling from oxidized to metallic cobalt. When Mg Kα excitation is used the same Auger peak interferes with the oxygen 1s photoelectron peak.