Preparation of single phase tungsten carbide by annealing of sputtered tungsten-carbon layers

Tungsten carbide layers were prepared by sputtering from a stoichiometric WC target and subsequent annealing. Carbide formation was found at temperatures above 800 degrees C. Annealing in pure hydrogen ambient results in a carbon depletion in the layers and the formation of a dominant W2C phase. We demonstrate that propane added to the annealing ambient stimulates a transformation of the tungsten-carbon layers to a stoichiometric WC phase. The variation of the propane concentration allows a continuously alteration of the layer structure between single phase WC and a mixed layer with dominant W2C and the adjustment of different values of the electrical resistance and the optical constants. (C) 2000 Elsevier Science S.A. All rights reserved.