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.