XPS study of MnO oxidation

The oxidation of a MnO layer has been studied by XPS at 400°C. Pure Mn oxides have been measured for comparison and the Mn oxidation states have been identified by Mn2p binding energy, Mn2p satellite structure, Mn3s multiplet splitting and valence spectra. A progressive oxidation of MnO to Mn2O3 without intermediate formation of Mn3O4 has been observed. Comparison of core and valence spectra seems to indicate that a thin layer of Mn2O3 is initially formed on top of MnO. At higher O2 exposure the MnO is completely oxidized to Mn2O3.