Effects of Sapphire Substrate Preparation on ZnO Epitaxial Growth by Atmospheric-Pressure Metal Organic Chemical Vapor Deposition

C-oriented ZnO epitaxial thin films were prepared on sapphire substrates by atmospheric-pressure metal organic chemical vapor deposition using diethyl zinc and water vapor as precursors. In-plane twins observed in ZnO films on sapphire (0001) substrates were reduced markedly by the use of (1120) substrates owing to a coincident-site lattice match and geometrical fitting. An extinction of peak splitting in the ?/2? scan and a reduction in full width at half maximum in rocking curves were also observed. In the case of the sapphire (0001) substrates, the rotational domains of the ZnO films were reduced by air-annealing of the substrates. It seems essential that the sapphire (0001) topmost surface be terminated by a single Al layer to eliminate the rotational domains.