Photochromic samarium oxyhydride thin films

Photochromism has been reported for several rare-earth (RE) metal oxyhydride thin films and is characterized by a reversible darkening of the sample when exposed to light with energy greater than its optical bandgap. Here, we extend range known photochromic RE-oxyhydrides include samarium oxyhydrides. These SmH3?2xOx are made reactive magnetron sputtering as-deposited SmH1.9+? post-oxidation in air phase. The deposition pressure during used control resultant properties Sm-oxyhydride film, such as bandgap, cubic lattice constant, contrast, bleaching speed. Using Sm RE-cation results slower speeds compared other lanthanides. We posit that this due stability Sm2+ state difficulty oxidizing it back original RE3+ state. This points key role charge material.