Effect of boundary plane on the atomic structure of [0001] ∑ 7 tilt grain boundaries in ZnO

The atomic structure of [0001] ∑ 7 tilt grain boundaries with {123̄0}∥{123̄0}, {145̄0}∥{145̄0} and {101̄0}∥{358̄0} boundary planes in ZnO was investigated through high-resolution transmission electron microscopy observation of fiber-textured thin films and atomistic calculations. These boundaries were found to comprise three kinds of common structural units that are characterized by fourfold- to eightfold-coordinated channels along the [0001] direction in contrast to sixfold-coordinated channels in wurtzite structure. The boundary structural units are very similar to the multiple core structures of edge dislocations with Burgers vectors of 1/3 <112̄0> . Transformation between two of the three configurations can easily occur through an atom flipping corresponding to dislocation glide. Depending on the orientation of boundary planes with respect to the Burgers vectors, the dislocation-like units exhibit straight or zigzag arrangements with periodicities corresponding to the ∑ 7 misorientation.