Investigation of the hydrogenation properties of Zr films under unclean plasma conditions

Abstract

By the means of non-Rutherford backscattering spectroscopy and elastic recoil detection analysis, the plasma hydrogenation of Zr films with and without a Ni overlayer were investigated. Close to the theoretical maximum hydrogen storage capacity (H/Zr=2) was attained when the sample was exposed to plasma with relative low contamination and a hydrogen pressure of ∼2 Pa and a substrate temperature of 393 K for 10 min. This reaction rate is much higher than obtained for gas hydrogenation. In an unclean plasma condition, the absorption of hydrogen is retarded by C and O contamination occurring on the sample surface. Though the oxide layer does not act as an efficient permeation barrier to atomic hydrogen, the maximum equilibrium hydrogen content dropped drastically with increasing contamination. In contrast to theoretical prediction, the hydrogen capacity for Ti is lower than Zr due to sample contamination. Also, the influence of the Ni overlayer on the plasma hydrogenation is discussed.