Oxidation-induced stoichiometric and morphological change of oxide films on stainless-steel surfaces

The oxidation-induced stoichiometric and morphological changes of the oxide film on a stainless-steel surface are observed by X-ray photoelectron spectroscopy and atomic force microscopy for annealing temperatures in the range 400-500 degrees C in oxygen partial pressures of 10(-9) to 10(-4) Torr With increasing the temperature, a significant shift occurs in the Cr 2p(3/2) binding energy towards higher energies, indicating a change in the oxidation state of chromium. It is found that at 450 degrees C lower oxygen partial pressures favor the formation of a smooth, pure chromium oxide. At a low oxygen pressure the oxide formed mainly consists of chromium oxide that shows a markedly smooth surface with no distinct grains, whereas at a high pressure the oxide formed mainly consists of iron oxide with distinct grains.