Magnesium hydride film formation using subatmospheric pressure H₂ plasma at low temperature Available to Purchase

MgH₂ films were prepared using pure hydrogen plasma under subatmospheric pressures ranging from 13.3 to 53.3 kPa (100–400 Torr). The prepared films were characterized by scanning electron microscopy, x-ray diffraction (XRD), and temperature programmed desorption measurements. The ratio of MgH₂ to Mg in the prepared films was evaluated, as the degree of Mg hydrogenation, by XRD analysis. The plasma was found to be indispensable for the preparation of thick MgH₂ film near normal hydrogen pressure. Hydrogen plasma exposure treatment after Mg film formation had only a very small effect on thick MgH₂ film formation, despite the use of subatmospheric pressure hydrogen plasma with high H atom density. Simultaneous supply of Mg and atomic hydrogen was found to be important in preparing thick MgH₂ films. Therefore, the surface reaction between Mg and H appears to play an important role in the growth process. The flux ratio (Γ_H/Γ_Mg) of atomic H and Mg required to prepare highly hydrogenated Mg was found to be more than 100. The resulting degree of hydrogenation of the prepared MgH₂ film was as good or better than that of commercial powders. MgH₂ film prepared on Si substrate exhibited growth with (211) preferred orientation as the deposition rate was decreased, and a columnar structure along the growth direction. The deposition rate reached 2.9 μm/min while still maintaining a high degree of hydrogenation.