Arrangement of structural units in a ZnO [00▪1] Σ = 49 symmetrical tilt boundary was investigated by using a combination of high-resolution electron microscopy and atomistic calculations. The boundary was found to be described by a combination of two different dislocation-like structural units and a bulk-like structural unit. The two dislocation-like units were very similar to structural units found in a Σ = 7 boundary. One of the dislocation-like units contained threefold-coordinated atoms and the other one has fivefold-coordinated atoms in contrast to the fourfold coordination in bulk ZnO. The Σ = 49 boundary predominantly consisted of a straight alternating array of dislocation-like units and a bulk-like unit. A zig-zag array of the units partly appeared, which could be related to the straight array via atom flipping at the boundary core. It was considered that the alternating array of dislocation-like units effectively relaxed local strain in the vicinity and, hence, minimized the boundary energy.

Arrangement of Multiple Structural Units in a [0001] Σ49 Tilt Grain Boundary in ZnO. Y.Sato, T.Mizoguchi, F.Oba, Y.Ikuhara, T.Yamamoto: Physical Review B, 2005, 72[6], 064109 (7pp)