Structural investigation by the Rietveld method of sputtered tungsten carbide thin films

Thin films of tungsten carbides deposited by reactive radio-frequency sputtering were investigated by X-ray diffraction using the Rietveld method. Two films were selected for the structural refinement. One was biased, the other unbiased. The unbiased film was found to consist of a cubic phase WC1 − x (C0.9) in the space group Fm3m with a lattice parameter of 4.263 (5) Å. A negative substrate bias of − 40 V leads to a multiphasic film: a cubic phase WC1 − x with a lattice parameter of 4.301 (6) Å and a hexagonal phase W2C (P-3m1) with lattice parameters of a = b = 2.787 (1) and c = 4.549 (2) Å. The domain size was found to be of ~ 5 nm. The coexistence of nanocrystalline phases WC1 − x and W2C is in accordance with the decrease of the carbon content (WC0.7) in the biased film.