Electronic structure of twist grain-boundaries in ZnO and the effect of Sb doping

We have investigated the properties of two Σ=7 [0 0 0 1] twist grain boundaries in ZnO using ab initio plane wave pseudopotential density functional theory. The calculations confirm the stability of the atomic models and enable a comparison between two energetically similar boundaries which exhibit bond stretching and bending. It is shown that shallow states exist as a consequence of the distortions in the grain boundaries, but no deep states. One of the boundaries was doped with a substitutional Sb impurity and it was seen that electron localisation takes place in the form of a weak Sb-metal host bond across the interface raising the possibility of further stabilisation of the boundary.