Low-temperature and low-H2 pressure synthesis of hydride semiconductor YH3−δusing Pd/Ni co-capped Y films

Publication date: 28 February 2017
Source:Thin Solid Films, Volume 624
Author(s): K. Yabuki, H. Hirama, M. Sakai, Y. Saito, K. Higuchi, A. Kitajima, S. Hasegawa, O. Nakamura
With an aim of decreasing the temperature (T γ ) at which metallic Y reacts with H2 to form the semiconductor phase YH3−δ , we employed Pd and Ni co-capping layers as catalysts, and compared the result with those obtained when employing Pd or Ni single-capping layers. These Y films capped with three types of catalytic layers were deposited by electron beam evaporation, and subsequently hydrogenated at a H2 partial pressure of approximately 3×10³ Pa while varying the H2 reaction temperature ($T_{H_2}$) from 20° C to 500° C. Pd/Ni co-capping materials exhibited a T γ of ≃ 50° C, which is approximately 40° C lower than that of Ni capped materials. With regard to Pd-capped material, the metal-dihydride phase YH2±δ prevailed for all investigated $T_{H_2}$. Quantitative studies in terms of the Gibbs free energy were conducted by assessing the molar concentrations of the YH δ <0.21, YH2±δ , and YH3−δ phases from corresponding X-ray diffraction intensities.