Influence of hydrogen incorporation on texture and grain size in YH2 films

We have investigated the influence of hydrogen absorption on crystal quality of dihydride of Y by selecting the type of a cap layer for the Y surface from non-capped, Gd capped, Pd capped, and Ni capped cases. Our experiments revealed that (i) the grain size (D) of YH2 does not correlate with that of Y, but is strongly affected by the type of cap layer; the presence of Pd layer reduces D   by a factor of ∼1.5∼1.5 when hydrogenated, whereas Ni capped, Gd capped, and non-capped cases increase D   by a factor of ∼2∼2 when hydrogenated, (ii) as deposited non-capped and Pd capped Y films having high crystal textures (T) yield YH2 films also having high T but a slight difference in T present in as deposited films is non-linearly enhanced upon hydrogenation so that the highest T value obtained in this study was found to be larger than those reported so far.

► The grain size (D) of YH2 does not correlate with that of Y. ► The presence of Pd cap layer on Y reduces D by a factor of 1.5 when hydrogenated. ► As deposited Y films having high crystal textures (T) yield YH2 having high T. ► A slight difference in T present in Y films is non-linearly enhanced upon hydrogenation.