Effects of H vacancies on photochromic properties of oxygen-containing yttrium hydride

We present in-situ studies of H loss from YHO films using ion beam analysis and its effect on the photochromic properties. The film evaporates loosely bound H under exposure to a beam of 3056 keV He2+ without a concomitant increase of O. Annealing at 145 °C decreases both the photochromic contrast and the bleaching speed indicating the importance of mobile H for the photochromic reaction.