Growth Processes And Properties Of Large Size ZnO: Al Thin Films Prepared By Radio Frequency Magnetron Sputtering

Transparent conductive film (TCO) with low resistivity, high transparency in visible range, unique electrical and optical properties, has been widely used in many fields. As an ideal transparent conductive film, Al-doped ZnO (AZO thin films) has a rich source of raw materials which are cheap and non-toxic, and has the merits of stability in an atmosphere of hydrogen plasma relative to ITO films.In this study, ZnO:Al thin films were prepared by RF magnetron sputtering on big size glass substrate (300×300mm) using a zinc oxide target doped with Al2O3 (2wt%.). The scanning sputtering mode was used to prepare the ZnO:Al thin films under different condition, and the uniformity were studied by investigating the lateral distribution of the thickness and resistivity of the films. On the basis of the uniformity of the films, the influences of the sputtering power, substrate temperature and working gas pressure on the deposition rate, structure, surface morphology, optical and electrical properties were studied. The structural, optical and electrical properties of the ZnO:Al thin films were characterized by XRD, SEM, surface profilometer, UV-visible spectrophotometer, Hall effect automatic tester.The results showed the films prepared under scanning sputtering mode had excellent uniformity, and the lateral distribution of the thickness and resistivity of the films on the substrate is uniform. In different sputtering conditions, the prepared ZnO:Al thin film were hexagonal wurtzite polycrystalline structure and showed an oriented film growth, with the crystallographic c-axis along (002) crystal plane perpendicular to the substrate surface. In the different sputtering power conditions, with the increase of the sputtering power, the structural, optical and electrical properties of thin films were improved significantly, when the power was 1400W, the lowest resistivity 1 .006×10?3 ??cmwas got. Deposition rate of the film increased significantly with increasing sputtering power. In the different substrate temperature conditions, with increasing substrate temperature, the film crystalline was getting better. When the substrate temperature was 280℃, the resistivity of films with the best performance was 2. 0224×10?3 ??cm. In different working gas pressure conditions, with increasing Ar pressure, the crystallization of the film was improved, the resistivity decreased first and then increased. When sputtering pressure in the experiment was 0.5 Pa, the minimum resistivity was 1. 5045×10?3 ??cm. The influence of substrate temperature and working pressure on the film deposition rate was not significant. The optical transmittance of films in visible range was over 80%. The band gap of the ZnO:Al was larger than the width of the band gap of intrinsic ZnO.