Microstructural Studies of Epitaxial ZnO Films Deposited on Sapphire by Reactive RF Magnetron Sputtering

ZnO films were grown epitaxially on (0001) sapphire substrates by reactive sputtering of a zinc target. Films of thickness in the range of 25-300 nm were deposited in the substrate temperature range of 300-500 degrees C. Powder and high-resolution X-ray diffraction studies have been used to study the effect of substrate temperature and thickness on crystallite size, mosaic tilt and twist. The films deposited below 300 degrees C and thickness less than 50 nm exhibit misaligned mosaicity, which improves significantly in films with thickness similar to 100 nm. The effect of growth conditions on twist is more significant than on tilt, implying a higher sensitivity to edge dislocations.