The effect of oxygen ratio on the crystallography and optical emission properties of reactive RF sputtered ZnO films

ZnO thin films were successfully grown on fused silica substrates by reactive RF sputtering. The ratio of the reactive oxygen (O2) gas to the sputter argon (Ar) gas varied from 10% to 90%. The XRD results showed a single diffraction peak of (0 0 2) phase, with the values of FWHM tend to decrease as the oxygen ratio increases. The prepared films showed a good optical transmittance with the decrease of refractive index from 2.2 to 1.9 as the oxygen ratio increases. The PL spectra showed a single UV emission with a broad peak at the visible and infrared regions. The UV peak shifted from 3.25 to 3.17 eV, while the intensity decreases as the oxygen ratio increases. The work discussed the influence of the O2 ratio on the structural and optical properties of the films.