This study investigated the process parameter effects on the structural and optical properties of ZnO thin film using radio frequency (RF) magnetron sputtering on amorphous glass substrates. The process parameters included RF power and working pressure. Results show that RF power was increased to promote the crystalline quality and decrease ZnO thin film defects. However, when the working pressure was increased to 3 Pa the ZnO thin film crystalline quality became worse. At a 200 W RF power and 1 Pa working pressure, the ZnO thin film with an optical band gap energy of 3.225 eV was obtained.ZnO thin films, RF magnetron sputtering, XRD, ultraviolet transmission spectrum ZnO is a kind of hexagonal wurtzite structure (hexagonal system, unit cell parameters: a=0.3249 nm, c= 0.52056 nm, c/a=1.602). ZnO is a novel material for II-VI wide band gap semiconductor material. It has a large room temperature band gap of 3.37 eV and a high binding energy of 60 meV which is much more higher than any other wide bandgap semiconductor materials (GaN: 25 meV, ZnSe: 22 meV). Its high exciton binding energy (60 meV at room temperature), which is much higher than room temperature heat energy (26 meV), will theoretically favor efficient UV emission processes at room temperature. Consequently, ZnO is a potential candidate for applications in optoelectronic device and receiving more and more important attention.
ExperimentalThe ZnO thin films were deposited on amorphous glass substrates by RF magnetron sputtering using Zn (99.999%) target and varying working pressures (1, 1.5, 2, 3 Pa) [1] . The distance between sputter target and substrate was 90 mm. Ar was used as the sputtering gas and O 2 was used as the reactive gas. The thin films were investigated by X-ray diffraction (XRD) [2] and ultraviolet spectrophotometer [3] .
XRD studiesThe Glancing Angle (3°) X-ray Diffraction was used to analyze the ZnO thin films [4] . Figure 1 shows the XRD pattern of different sputtering power ZnO films [5] by 1 Pa working pressure. XRD measurements showed that ZnO thin films deposited under different conditions all gave strong (0 0 2) diffraction peaks. Other peaks with much less intensities were observed, indicating that the films are oriented with their c axis perpendicular to the substrate plane.In this experimental, substrate could not be heated so RF power not only made the neutral gas in the vacuum chamber glow discharge, but also raised the temperature of the substrate and the vacuum chamber. As a result, the RF power improved the reaction between the Zn atoms and O atoms. Because of the RF power affected the sputter rate and the temperature of the substrate and vacuum chamber, both of the sputter rate and the temperature affected the thin films, so the power of the RF power affected the quality of the thin films. The less of the FWHM means the films are oriented with