Deuterium retention in carbon and tungsten-carbon mixed films deposited by magnetron sputtering in D2 atmosphere

Deuterium (D) retention in carbon (C) and tungsten-carbon (W-C) mixed films deposited by reactive magnetron sputtering in D2 atmosphere has been investigated by means of secondary ion mass spectrometry and residual gas analysis measurements. In the C and W-C films, D is distributed homogeneously throughout the film thickness. With the deposition temperature increase, the D concentration in the C films is varied from ∼0.4 D/C (in units of atomic ratio) at 400 K to ∼0.02 D/C at 973 K. In its turn, the D concentration in the W-C films falls from ∼0.02 D/(W+C) at 400 K to values below 10-4 D/(W+C) at 973 K. In spite of the presence of carbon atoms in the W-C mixed films (up to 30%), the concentration of deuterium in these films is much lower than is expected from the assumption that the W-C mixed film consists of tungsten and graphite inclusions. The deuterium concentration in the W-C mixed films is close in value to that in pure tungsten or tungsten carbides. The co-deposition of carbon and tungsten atoms is speculated to lead to the formation of tungsten carbides even at temperatures as low as 400 K