Synthesis of photochromic oxygen-containing yttrium hydride

Abstract

Photochromic oxygen-containing yttrium hydride has been synthesized using a two step process. The process consists of an initial sputter deposition of oxygen-free yttrium hydride YH${}_{\mathrm{x}}$, followed by a controlled reaction with air that causes incorporation of oxygen into the material. An in-situ study of the YH${}_{\mathrm{x}}$ as it reacted with oxygen was made possible by applying an aluminium capping layer with a low but non-zero oxygen permeability prior to air exposure. During the reaction, the visual appearance of the YH${}_{\mathrm{x}}$ went from dark and opaque to transparent and yellowish. This transition was accredited incorporation of oxygen into the material, as shown through analysis with energy dispersive x-ray spectroscopy (EDS) and x-ray photoemission spectroscopy (XPS). Grazing incidence x-ray diffraction (GIXRD) studies revealed an fcc structure both before and after oxygen exposure, with a lattice parameter that increased from 5.2 Å to 5.4 Å during the reaction. With the lattice parameter in the oxygen free YH${}_{\mathrm{x}}$ being equal to that reported earlier for YH${}_2$, our findings suggest that the non-reacted YH${}_{\mathrm{x}}$ in this study is in-fact YH${}_2$.

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• A new thin film photochromic material: Oxygen-containing yttrium hydride
• Transparent yttrium hydride thin films prepared by reactive sputtering
• Surface oxide on thin films of yttrium hydride studied by neutron reflectometry

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