Carbide formation in tungsten-containing amorphous carbon films by annealing

Tungsten-containing amorphous carbon films were produced by dual magnetron sputter deposition. The formation of carbide phases after heat treatment in inert gas at temperatures up to 2800 K was investigated by X-ray diffraction for tungsten concentrations below 25 at.%. After deposition, each film consists of an amorphous carbon matrix with atomically dispersed W inclusions. Annealing up to 2800 K leads to a formation of carbide phases and to nano clustering. Three tungsten carbide phases were observed (WC, W₂C, and WC_1 − x), mostly as mixtures of two phases. The phase combination depends on annealing temperature and W concentration. Additionally, nano diffraction was performed in a scanning transmission electron microscope, to determine the phase of single crystallites at scales, where X-ray diffraction fails.