Electrical Resistivity in Non-stoichiometric MoO2

MoO y with 1.85 ≤ y ≤ 2.20 has been studied by X-ray diffractometry and photoemission spectroscopy at room temperature and by electrical resistance as a function of temperature from 2 to 300 K. Although X-ray diffractograms are very similar to the stoichiometric MoO 2 with monoclinic structure of the space group P2 1 /c (14), the electrical properties are strongly dependent on the oxygen composition. Samples with y = 1.85 and 1.90 show anomalous behavior in electrical conductivity. Photoemission and X-ray absorption spectroscopy measurements suggest that this anomalous behavior is related to the presence of Mo 3+ ions such as in K x MoO 2 compound.