Formation of a low energy grain boundary in ZnO:: The structural unit concept in hexagonal symmetry materialsl

ZnO thin films prepared by magnetron sputtering on c-plane sapphire may exhibit a columnar growth with an average column diameter depending on the deposition temperature. In this case two epitaxial relationships coexist and adjacent columns are rotated, one from the other, by 90 degrees around the [0001] direction. The long range rotation between domains is in agreement with the theoretical epitaxial relationships, but the local angles oscillate between 27 degrees and 32 degrees due to the formation of interfaces, which settle into low energy configurations with grain boundary dislocations of a Burgers vectors and 5/7 aligned structural units for the 32.2 degrees tilt angle. (c) 2008 American Institute of Physics.