The 30° rotation domains in wurtzite ZnO films

Abstract The 30° rotation domains in ZnO films were studied by transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). The cross-section and plane-view observations reveal that the 30° rotation domains have elliptical cylindrical shape, with the longitude axis along one of the 〈1 1 2¯ 0〉 directions and the short axis along one of the 〈1¯ 1 0 0〉 orientations, respectively. The volume fraction of the 30° rotation domains is about 1%. Due to the elliptical shape of the domain boundaries along the [0 0 0 1] ZnO direction, partially disordered superlattice-like structures are formed. As shown by the HREM images and Zn elemental mapping, these super-lattices are most likely caused by periodical segregation and depletion of Zn along the domain boundary for compensating the mismatched lattice strain.