Interaction of O2 with WC(0001)

We report ARUPS, TDS and AUGER data for the interaction of O-2 with WC(0001). Depending on the preparation conditions, the adsorption of O-2 leads to different compounds on the surface. Exposure to several millibars of O-2 induces the formation of WO3 with no carbon left on the surface. The tungsten trioxide may be reduced towards WO2 by annealing in an H-2 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. (C) 1998 Elsevier Science B.V. All rights reserved.