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

Abstract With an aim of decreasing the temperature ( T γ ) at which metallic Y reacts with H 2 to form the semiconductor phase YH 3 − 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 H 2 partial pressure of approximately 3 × 10 3 Pa while varying the H 2 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 YH 2± 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 , YH 2± δ , and YH 3 − δ phases from corresponding X-ray diffraction intensities.