The Study On The Optical And Electrical Properties Of ZAO Film Prepared By Magnetron Sputtering

Due to high carrier concentration and wide optical band gap transparent conductive oxide thin films exhibit outstanding optical and electrical properties, such as low resistivity and high transmittance in the visible range etc. At present this kind of material system include In2O3, Sn02, ZnO and dopant system In2O3:Sn(ITO), SnO2:Sb, SnO2:F, ZnO:Al(ZAO) etc. Among them, SnO2(TO) and In2O3:Sn(ITO) films have been widely used in liquid crystal display and solar cell as transparent electrode. What'more Al-doped ZnO films show good electrical and optical properties and emerge as a potential alternative candidate for ITO films. Furthermore, they offer a number of advantages compared to the predominant ITO films nowadays: (i) cheap and abundant raw materials; (ii) nontoxicity; (iii) good stability in hydrogen plasma, which is of significance for applications related to amorphous silicon solar cell. So the study on ZAO film is becoming fashionable.Many processes are used to prepare transparent conductive films such as magnetron sputtering, vacuum reactive evaporation, chemical vapor deposition, sol-gel, laser-pulsed deposition. Among these methods, magnetron sputtering is the most widely used technique for preparing thin films owing to its high deposition rate and good uniformity etc.In my experiment, ZAO films were prepared by DC magnetron sputtering in pure argon gas atmosphere using ZnO target mixed with Al2O3(lwt%, 2wt%, 3wt%, 4wt% respectively) and the films were figured by XRD, SEM, XPS, AFM and FTIR, UV photometer. It was concluded that the effect of process parameters on the structural electrical and optical properties of ZAO films had great influence. In addition ZAO films were also deposited in a mixed Argon and oxygen gas, through this way, the effects of oxygen on the properties of the films were studied.The study indicated that when the ratio of Al2O3 in target is 3wt%, the films had the best properties. The peak position of ZAO films prepared at low temperature shifts to the lower angle comparable to that of bulk ZnO due to the residual stress; as-deposited at high temperature or post-annealed ZAO films was polycrystalline with the hexagonal crystal structure and had a strongly preferred orientation of c axis perpendicular to the substrate surface, the minimum resistivity and average transmittance to the visible light can be obtained.During deposition of ZAO films oxygen and DC power had great influence on the optical and electrical properties. The conclusion showed that the oxygen always made film's resistivity increase. The surface sheet resistance decreases with increasing DC power of Zn target, ZAO thin films show minimum resistivity at the power of 100W; the conductivity get worse with further increase in DC power.