Chemical-state information obtained by AES and XPS from thin oxide layers on duplex stainless steel surfaces

Thin oxide films were produced by the exposure of polished, sputter-cleaned metallic surfaces kept in UHV to several thousands of Langmuirs at 10−5 mbar oxygen yielding oxide layers of several nanometers. Metallic substrates used were iron, chromium and duplex stainless steel (DSS 2205). AES and XPS profiling analyses were performed. An attempt was made to use certain features observed in the AES spectra, i.e. to correlate Fe and Cr MNN peak shapes with the chemical state of the corresponding element. A similar approach has been tried before and may, when combined with high-lateral-resolution AES, provide small-area chemical-state information. Localized chemical-state information derived from the MNN peak shapes by a Linear Least Squares Fit (LLSF) procedure appeared to match reasonably well with that provided by XPS, which is averaged over approximately 2 mm2. This is a plausible result for a thin homogeneous layer on a polished substrate.

► AES and XPS depth profiles of oxide films on duplex stainless steels were measured.
► Chemical state specific features of the Fe and Cr AES spectra were studied.
► Information from chemical state specific peak shapes was used in AES depth profiles.
► They were similar to those obtained by XPS, with resolved metallic and oxide states.
► This may enable chemical state analysis with high lateral resolution.