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Abstract:
We report ARUPS, TDS and AUGER data for the interaction of O2 with WC(0001). Depending on the preparation conditions, the adsorption of O2 leads to different compounds on the surface. Exposure to several millibars of O2 induces the formation of WO3 with no carbon left on the surface. The tungsten trioxide may be reduced towards WO2 by annealing in an H2 atmosphere. Less intensive oxygen treatment (some 10−5 mbar) leads, depending on the oxygen pressure and surface temperature, to elemental tungsten, tungsten oxide and carboxide in the surface region with the elemental tungsten being covered by a thin oxide layer. At elevated temperatures, oxygen reacts with the carbon and desorbs as CO, as observed via TDS and ARUPS.
