ZnO thin film stoichiometry influent by working gas during radio frequency magnetron sputtering

The effects of different working gases on the structural and optical properties of ZnO thin films were investigated under high pressure of 7 Pa deposition using radio frequency (rf) magnetron sputtering. It was found that crystallinities of the ZnO films were increased with the oxygen gas ratio increase; the average of crystallite size was increased as well. The optical emission spectroscopy (OES) in-situ measurement revealed the kinetics species in the rf plasma during the depositions. It was found that the intensity of the excited atomic oxygen (O*) was increased with the oxygen ratio increase, resulting in enhancing the ZnO oxidization during the rf sputtering. In contrary, the intensities of emissions from argon and molecular oxygen (O₂⁺) as well as atomic zinc emission were gradually decreased. The photoluminescence property measurements showed that the ultraviolet (UV) emission decreased with the oxygen ratio increase, meanwhile, the deep level emission from as-deposited films were drastically suppressed.