Hydrogen motion in the Cu-H complex in ZnO

Abstract

The Cu-H complex in ZnO consists of Cu on Zn site and a hydrogen atom bound to a nearby O atom, with the O\char21{}H bond oriented in the basal plane of the hexagonal lattice to the $c$ axis. The motion of hydrogen in the Cu-H complex is studied by the stress-induced dichroism. Stress applied at room temperature along $[1\overline{2}10]$ results in an alignment of the Cu-H bond. The reorientation process was found to be thermally activated with the activation energy of $0.52\ifmmode\pm\else\textpm\fi{}0.04\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The connection of the hydrogen movement in the Cu-H complex with the hydrogen diffusion in ZnO is discussed, and consequences for the existence of interstitial hydrogen at room temperature are presented.