Effect of bias sputtering condition on structure of LaNi₅ films

Purification of hydrogen using a hydrogen storage alloy film has various advantages such as low operation energy and low costs of the equipment. However, because of the surface roughness of a substrate, the surface of the sputtered film was not smooth and had some pinholes. It was considered that use of a bias sputtering method might solve these problems. Hence, in this study, the influence of the bias power on the composition, microstructure and crystal structure of the LaNi₅ sputtered film were investigated. When the film was deposited with a direct current sputter power W_S = 50 W and a radio frequency bias power W_B = 20 W, the diffraction peak of LaNi₅ was not observed on the film. With W_S = 200 W and W_B = 20 W, the film had crystal structures. However, when the W _B was increased more than 40 W with W_S = 200 W, the film became the amorphous structure. It is considered that, to make the amorphous structure and the dense film with higher W_S, the W_B has to be increased.