Surface analysis of thin stainless steel films and thick-coated steel by simultaneous application of conversion electron and X-ray Mössbauer spectroscopy

Abstract

A dual He/Ar gas counter for simultaneous measurements of conversion electron and X-ray Mössbauer spectra (CEMS and XMS) has been developed and applied to characterization of thin stainless steel films and thick-coated steel. For thin stainless steel films, three depth-selective CEMS spectra were simultaneously obtained by detecting the electrons with three different energy ranges (1 to 3 keV, 3 to 6.5 keV, and 6.5 to 12 keV). The iron oxide layer (4 nm in thickness) on stainless steel was clearly observed by detecting high-energy electrons (>6.5 keV). Ferromagnetic phase was produced by a magnetron Ar sputtering of austenitic stainless steel, and the average hyperfine magnetic field increased from 25 to 28 T by thermal treatment. The magnetic phase was partially converted into austenite (γ-phase) at 500 °C. In the case of thick-coated steel, where the coating was produced by electrochemical sulfurization, CEMS and XMS spectra were simultaneously obtained by detecting all the resonant electrons above 3 keV as well as X-rays between 3 and 6.5 keV. The area ratios of the subspectra assigned to the austenite and ferrite phases were different in the CEMS and the XMS spectra. This suggests that austenite and ferrite at the surface had selective reactivity with the sulfurizing agent. It was shown that the phase analysis of the surface, interface, and substrate was simply and effectively realized by using a dual He/Ar gas flow counter.