On the optical absorption coefficient of Gd hydride thin films: coexistence of the Gd (GdH₂) and GdH_x(GdH_2+y) phases

Abstract

Electron beam evaporated Pd-capped Gd thin films were deposited on quartz substrates and subsequently hydrided. Transmittance spectra of these bilayer systems, under unpolarized normal illumination, were obtained and used in an inversion approach from which the spectral dependence of the effective optical constants is obtained. The optical absorption coefficient of the β-phase GdHx (with 1 < x ⩽ 2) is reported. The semiconductor GdH2+y state (with 0 < y ⩽ 1) is characterized in terms of the optical absorption coefficient and the optical gap. By assuming a granular morphology of the films, with some of the grains in the metal GdH2 phase and other grains covered with a transition layer containing the semiconducting GdH2+y phase, the hydrogen concentration dependence of the optical gap is shown and the optical absorption edge of the stoichiometric γ-phase GdH3 is reported.

Metal-Semiconductor Transition on the Surface and in the Bulk of Europium Hydride Thin Film

“…Thus the majority of described investigations were performed ex situ and concerned bilayer systems in which RE lm is protected against oxidation by a thin palladium overcoat. This solution has been applied in studies of bulk phenomena (electrical and optical properties) associated with hydride formation in thin lms of several hexagonal metals, like Y [8], Gd [9], Tb [10], Ho [11]. We have recently performed in situ measurements of uncovered thin Gd [12] and Tb [13] lms during interaction with hydrogen, extending investigations into * corresponding author; e-mail: rnowakowski@ichf.edu.pl surface phenomena using the static capacitor method.…”