Study of the oxidation of molybdenum surfaces by energy loss spectroscopy combined with Auger electron spectroscopy

The oxidation of molybdenum as an evaporated film and of its annealed surface was investigated by Energy Loss Spectroscopy (ELS) combined with Auger Electron Spectroscopy (AES). The 10 eV and the lower energy loss peaks towards 5 eV were identified as the clean surface and the oxidized layer surface plasma loss peaks, respectively. The behaviours of these surface plasma loss spectra revealed that the oxidation of the evaporated film surface proceeded uniformly, rapidly and without any induction period under vacuum of 10–7 Torr, whereas that of the annealed sample proceeded more slowly through "oxidized patches", exhibiting a considerable induction period under the same vacuum conditions. These phenomena were interpreted with reference to the surface conditions and structures studied by the AES and ELS; the fresh evaporated surface is clean and rough, whereas the annealed surface is smoothed by the heat-treatment and contaminated by sulphur and carbon which partially cover the active surface and give rise to the patchy surface oxidation.