Hydrogen motion in the Cu-H complex in ZnO

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-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 [1210] 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 +/- 0.04 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.