First-principles calculations were carried out to investigate the diffusion behavior of H in Li-doped ZnO and the vibrational properties of the Li-H complexes in ZnO. It was found that a Li-H complex in ZnO could form easily through H diffusion by overcoming an energy barrier of less than 0.5eV, and the dissociation of the Li-H complex requires activation energies of 1.10 to 1.35eV. Moreover, the H atom could hop between two Li-O bonds in the basal plane of the hexagonal lattice, with an activation energy of about 0.32eV only. In addition, the vibrational frequencies were evaluated for the cases of H locating at the ground state site and the second-lowest energy site, from which were found local vibrational modes within the 270 to 400/cm range relevant to the Li-H complex, and local vibrational modes within the 600 to 750/cm range relevant to the O-H and Li-O bonds. These typical modes may serve as additional indicators of the existence and configurations of the Li-H complex in ZnO, like the O-H stretch modes reported in experimental studies.

Theoretical Study of H Diffusion Behavior and the Vibrational Properties of Li-H Complexes in ZnO. Hu, J., He, H.Y., Pan, B.C.: Journal of Physical Chemistry C, 2009, 113[26], 11381-4