Angle resolved XPS study of thin oxide layers formed on the surface of iron-chromium binary alloys exposed to air

Abstract

Recent angle resolved X-ray photoelectron spectroscopy (AR-XPS) on the surface of iron-low chromium alloys due to air exposure at room temperature after sputter cleaning has suggested that an oxide layer of nanometer order of magnitude of thickness formed on the alloys, and a contaminated overlayer covered the oxide layer. In the present work, we have subsequently studied the surface of iron-chromium alloys containing chromium more than 50mass%, in order to confirm the previous remarks for these thin oxide layers on a wider base. Estimation of the effective thickness of these layers by coupling with a model indicates that the thickness of the oxide layer on the surface decreases with increasing chromium concentration up to 50 mass%, and is kept almost unchanged with higher chromium. It is, however, noted that the intensity of metallic peaks in Cr2p XPS spectra still increases with chromium concentration more than 50mass%, and the position of O 1s XPS spectra shifts as the chromium concentration increases. These facts suggest that the characteristic features of the oxide layers are affected, more or less, by the bulk chromium composition.