Fabrication and characterization of hydrogen absorption LaNi₅ alloy films sputtered on nickel substrate

LaNi₅ films were deposited on a nickel substrate using a La₂Ni₇ alloy target with a sputtering power, W_s, of 50-400 W at substrate temperature, T_s, of 323-573 K by a radio frequency magnetron sputtering apparatus. The nickel content of the films decreased with increasing W_s and increased with increasing T_s. At low W_s and low T_s, amorphous films were deposited. In other conditions, the films were polycrystalline. The films deposited at high W_s and low T_s exhibited only a (hk · 0) peak in the X-ray diffraction profiles. This indicates that the c-axis of crystalline films was oriented parallel to the substrate plane. At high W_s and high T_s, the films with columnar structure were obtained. The hydrogen absorption capacity of the films increased with increasing W_s. On the other hand, the equilibrium pressure of the films decreased with increasing W_s. The films deposited at 400 W represented a pressure plateau on the pressure-composition isotherms.