Self-assembled ZnO Nanostructures Grown on Sapphire (0001) Substrates by Radio-frequency Magnetron Sputtering

This paper reports the synthesis and the microstructure of self-assembled ZnO nanostructures grown on sapphire (0001) substrates by radio-frequency magnetron sputtering. In the course of strain relaxation, the growth mode was changed from an initially-strained, flat-layered ZnO to nano-pyramids through intermediate compact nano-islands as the film thickness was increased. The ZnO nano-pyramids were quite uniform and were dispersed densely on the growing fronts. In-plane domain matching between ZnO and sapphire (0001) depended on the residual strain. The self-assembled formation of ZnO nanostructures was quite sensitive to the growth pressure.