Low power deposition of high quality hexagonal ZnO film grown on Al2O3 (0001) sapphire by dc sputtering

Abstract

Abstract High quality hexagonal block of nanostructured zinc oxide (ZnO) thin films were grown on Al 2 O 3 (0001) sapphire substrate at room temperature by direct current (dc) magnetron sputtering, with low sputtering power from 10 to 50 W. The effect of sputtering power on the structural, optical and morphological properties of the films was investigated by X-ray diffraction (XRD), photoluminescence spectrometer, UV–vis spectrometer and scanning electron microscope (SEM), respectively. From the XRD pattern, it is inferred that (002) oriented peaks is present in all the samples prepared under various sputtering powers. The presence of a strong single UV emission at 385 nm is attributed to the near band edge emission, confirming that the film have less defect density signifying the high crystal quality of the samples. The films were highly transparent with sharp absorbance edges, and average visible transmittance is of 90%. SEM micrographs revealed that the grains become more uniform with very little mismatch with the surface of c-cut sapphire substrate, with increase of sputtering power. The film prepared at the dc power of 40 W results in a layer containing well shaped hexagonal wurtzite ZnO.