Formation of ZnO nanostructures in energy-controlled hollow-type magnetron RF plasma

In this study, we investigated how zinc, sputtered from a zinc target, reacts with oxygen on the substrate to form ZnO nanostructures when the discharge parameters, such as gas flow ratio and target bias voltage, are controlled in O₂/Ar plasma. The deposits were estimated by SEM and Raman spectroscopy. Under conditions of a Zn to Ar optical emission intensity ratio of 2/1, a target voltage of - 550 V, a total pressure of 40 Pa, a substrate temperature of 150 °C, an RF power of 50 W, and a deposition time of 30 min, many vertically aligned ZnO nanorods were observed to be deposited on the substrate. The diameter of the rods was typically 50 nm. It was found that the film morphology can be controlled by the sputtering rate of zinc varied by the target bias voltage and gas flow rate.