Chemistry Publications
Document Type
Article
Publication Date
6-15-2023
Journal
Surface and Interface Analysis
Volume
55
Issue
10
URL with Digital Object Identifier
https://doi.org/10.1002/sia.7243
Abstract
X-ray photoelectron spectroscopy (XPS) is a technique that is widely used to studythin oxide films because of its extremely high surface sensitivity. Utilizing theQUASES (Quantitative Analysis of Surfaces by Electron Spectroscopy) software pack-age developed by Sven Tougaard (University of Southern Denmark), a user canobtain additional information that is not extracted in conventional XPS analysis, spe-cifically the composition as a function of depth. Presented here is the QUASES analy-sis of four Ni-Cr-Mo alloys performed while testing various inelastic mean free path(IMFP) determination methods in the context of providing a framework for the analy-sis of complex oxides in QUASES. Ni-Cr-Mo alloys are often used to replace conven-tional materials under aggressive conditions, because of their exceptional corrosionresistance. Their corrosion resistance is conferred by the formation of an inert sur-face oxide film that protects the underlying metal. Using the QUASES software, thethickness of the air-formed oxide on four Ni-Cr-Mo alloys was found to lie within therange of 2.5–3.6 nm. They were found to be composed of an inner Cr2O3layer andan outer Cr (OH)3layer, with a transition zone where the two coexisted. OxidizedMo species, MoO2and MoO3, were found in trace amounts at the boundarybetween the Cr2O3-only and mixed Cr2O3/Cr (OH)3regions of the oxide. We alsodetermined that using 20% reduced IMFP values gave results similar to thoseobtained using electron effective attenuation length (EAL) values. Auger depth pro-files showed comparable trends to the QUASES models.
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