Oxygen bombardment effects on average crystallite size of sputter-deposited ZnO films

Zinc oxide (ZnO) film was deposited on a glass substrate by rf magnetron sputtering with O2/Ar as working gases. Structural properties of the films were characterized by XRD. Average crystallite size in the films was strongly dependent on both the gas flow ratio of O2/Ar and rf-power at a constant deposition pressure. During the deposition, energetic species in the plasma were in situ monitored using optical emission spectroscopy. An inverse correlation was observed between the average crystallite size and the emission intensity ratio of IO∗/IArIO∗/IAr. Bombardment of atomic oxygen to the growing surface played an important role in determining the average crystallite size in the films. The average crystallite size could be controlled by the emission intensity ratio of IO∗/IArIO∗/IAr.