Based upon ab initio total energy calculations, Li, Na and Ag interstitials were found to be stable with at least a 1.56eV energy barrier required to transform to a zinc substitutional site in ZnO, whereas interstitial K required the relatively small energy barrier of 0.79eV. The isolated dopant substitutional defects (LiZn, NaZn, KZn and AgZn) were found to be rather stable, with at least a 3.4eV energy barrier to transform to an interstitial site. All of the dopant interstitials (Lii, Nai, Ki and Agi) were fast diffusers. The diffusion of Li interstitial was isotropic, whereas the diffusion of Na, K and Ag interstitials was highly anisotropic. Fundamental processes of the vacancy-assisted mechanisms were systematically investigated and specific values of the energy barriers were obtained.

First-Principles Study of Diffusion of Li, Na, K and Ag in ZnO. Huang, G.Y., Wang, C.Y., Wang, J.T.: Journal of Physics - Condensed Matter, 2009, 21[34], 345802