Influence of Palladium Overlayer on Switching Behaviour of Samarium Hydride Thin Films

概要

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Samarium films capped with a thin palladium overlayer undergo a metal to semiconductor transition during in-situ hydrogen loading (P_<H2> = 1.01 × 10^5 Pa) at room temperature. The transition is accompanied by a change in optical appearance, i.e. metallic gray samarium films change to golden greenish transparent samarium hydride (SmH_<3-δ>) films. Glancing angle X-ray diffraction (GAXRD) studies show that the rhombohedral structure of metallic samarium films changes to hexagonal structure of the SmH_<3-δ> films with average lattice parameters of a = 3.775 Å, c = 6.743k Å direct optical band gap of 3.0eV has been obtained for SmH_<3-δ> films from reflectance and transmittance data. The Hall coefficient measured as a function of hydrogen concentration, changes from a metal-like R_H value -14.9 × 10^<-10> m^3/C to -1081.8 × 10^<-10> m^3/C for SmH_<3-δ> films. On unloading hydrogen, the value of RH changes to -3.85 × 110^<-10> m^3/C at the dihydride composition.
社団法人応用物理学会の論文
2002-10-15