Effects of power on properties of ZnO thin films grown by radio frequency magnetron sputtering

Zinc oxide (ZnO) thin films have been grown on quartz substrates by using the radio frequency (RF) magnetron sputtering technique with different sputtering power, which was adjusted widely from 10 to 200 W. It was found that the sputtering power play an important role in the growth process of the film. The characteristic features of crystallinity, absorption and photoluminescence (PL) were examined. Furthermore, the surface morphology of the films was also observed by using atomic force microscopy (AFM). Upon increasing the power during the growing process, the films deposited at a RF power of 150 W showed the best crystal quality and optical properties. The inflection point at 150 W is detectable. This tendency is estimated to result from the enhancing of the particles sputtered from the ZnO target induced by the enlarging power. These results demonstrate that there is an optimal power operating window for sputtering technique. The physical mechanism for this has been explained by a straightforward qualitative model and dynamics equations.