Geometry and electronic structure of [0001]/((1)over-bar(2)over-bar30) Sigma=7 symmetric tilt boundary in ZnO

The [0001]/((1) over bar (2) over bar 30) Sigma = 7 symmetric tilt boundary in ZnO has been investigated by a combination of static lattice and first- principles molecular orbital calculations. Four types of stable boundary ge ometries with energies of approximately 1.5 J m(-2) were obtained by the st atic lattice calculations. The electronic structures of the derived geometr ies are discussed comparatively with those of ZnO bulk and the (10 (1) over bar 0) surface. In the: configuration with the lowest energy, there are sm all open channels at the boundary core but all the ions have preserved the fourfold coordination. The electronic structure resembles that of the bulk, regardless of the presence of the small open channels, and no remarkable i nterfacial electronic states are observed. The configurations with higher e nergy have relatively large open channels and some of the ions adjacent to the channels have been reduced to threefold coordination. Local electronic states at the ions are similar to the surface states in the valence and the conduction bands. However, no deep interfacial states are found, either.