The 30 degrees 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 degrees rotation domains have elliptical cylindrical shape, with the longitude axis along one of the < 11 (2) over bar0 > directions and the short axis along one of the < (1) over bar 100 > orientations, respectively. The volume fraction of the 30 degrees rotation domains is about 1%. Due to the elliptical shape of the domain boundaries along the [0001](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. (c) 2006 Elsevier B.V. All rights reserved.