title: Ellipsometric study of dielectric functions of Mg(1-y)Ca(y)H(x) thin films (0.03≤y≤0.17).
abstract: Mg(1-y)Ca(y)H(x) (0.03≤y≤0.17) alloy thin films covered with thin Pd were hydrogenated using 4% H(2) in Ar under atmospheric pressure at room temperature. The complex dielectric functions (ε=ε(1) + iε(2)) in the range of 0.75 to 5.0 eV of these hydrides were evaluated with spectroscopic ellipsometry. The imaginary part of the dielectric function ε(2) was composed of one Drude and three Lorentz oscillator terms whose peak positions were about 1.2 eV (L(1)), 2.8 eV (L(2)), and 5.2 eV (L(3)). The L(3) term observed in all hydrides is attributed to optical absorption of MgH(2) with E(g)=5.16 eV. The Drude term, which may be due to unhydrogenated Mg-metal, was observed in the hydrides with a low Ca composition y of less than 0.04. The L(1) term was observed in the hydrides with a Ca composition of more than 0.05, while the L(2) term was observed for more than 0.11. These L(1) and L(2) terms were estimated from a variation with hydrogenation of ellipsometric angle Ψ which is due to optical absorption of CaH(2-α) (L(1)) and MgCaH(3.72) (L(2)).
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), Anagahora 2266-98, Shimoshidami, Nagoya 463-8560, Japan. yasusei‐yamada@aist.go.jp
authors.forename: Yasusei
authors.initials: Y
authors.lastname: Yamada
authors.forename: Kazuki
authors.initials: K
authors.lastname: Tajima
authors.forename: Masahisa
authors.initials: M
authors.lastname: Okada
authors.forename: Masato
authors.initials: M
authors.lastname: Tazawa
authors.forename: Arne
authors.initials: A
authors.lastname: Roos
authors.forename: Kazuki
authors.initials: K
authors.lastname: Yoshimura