Dependency of oxygen partial pressure on the characteristics of ZnO films grown by radio frequency magnetron sputtering

The effects of oxygen and argon gas contents on the structural and optical properties of epitaxially grown ZnO thin films on sapphire substrates by radio frequency magnetron sputtering were investigated. The growth rate of ZnO thin film decreases with increase in oxygen gas contents in the gas mixture. The high-resolution x-ray diffraction (1012) rocking curve and plane-view transmission electron microscopy investigations reveal the presence of a reduced dislocation density in the ZnO thin films with decrease in oxygen/argon flow ratio. However, large density of defects were observed in the boundaries and inside of the micro-hillocks formed on the surface of ZnO thin film grown with pure argon. The increase in oxygen gas ratio resulted in the improvement of optical properties with suppression and red-shift of the deep level emission.