Composition of photochromic oxygen-containing yttrium hydride films

In this work, the composition of oxygen-containing yttrium hydride (YHO) thin films was investigated. The films were prepared by reactive sputter deposition, and were found for have oxygen contents on the order of several tens of per cents. We present depth-resolved atomic composition profiles of photochromic YHO films to study the connection between composition, photochromic properties and growth parameters. Two films, deposited at different pressures, were prepared and characterized using ion beam analysis techniques, i.e. Rutherford backscattering spectrometry and elastic recoil detection analysis. We found that an increase of deposition pressure results in larger [O]/[Y] ratios, while the ratio [H]/[Y] becomes reduced. We also report a gradual oxidation of the films exposed to air as well as hydrogen release under ion bombardment.