The atomic and electronic structures of the [00•1]/(¯1¯2•¯0) Σ = 7 symmetrical tilt boundary were investigated by using an ab initio plane-wave pseudopotential method within the local-density approximation. Two types of equilibrium geometry were obtained, which had similar boundary energies. The atomic arrangement was largely reconstructed to eliminate dangling bonds in one configuration, whereas the other configuration involved a small bond distortion but had dangling bonds at the boundary core. The balance between the energies for deformed atomic arrangements, and for the elimination of dangling bonds, was expected to be significant in determining the boundary energies. The electronic structure of the grain boundaries was considered with particular regard to the relationship to bond disorder. Due to the bond distortion and/or the presence of dangling bonds, localized states formed mainly at the lower valence band and at the bottom of the upper valence band. On the other hand, the electronic states in the vicinity of the band-gap were not greatly affected by bond disorder. Deep electronic states were not generated in the band-gap; even for configurations with dangling bonds. This general behavior could be explained by the band structure which was intrinsic to ZnO.

Ab Initio Study of Symmetric Tilt Boundaries in ZnO. F.Oba, S.R.Nishitani, H.Adachi, I.Tanaka, M.Kohyama, S.Tanaka: Physical Review B, 2001, 63[4], 045410 (10pp)