Light-induced breathing in photochromic yttrium oxyhydrides

Abstract

When exposed to air, opaque yttrium dihydride YH${}_{2}$ turns into transparent and photochromic yttrium oxyhydride YHO. YHO darkens reversibly when illuminated with light of adequate energy and intensity. The darkening is produced by light-induced oxygen release and diffusion. Therefore, the complete bleaching of the darkened films, and hence the reversibility of the process, only takes place if a source of oxygen is provided, e.g. in air.