Study On Preparation And Characterization Of Al-doped ZnO Transparent Conductive Thin Films

Al-doped Zn O(AZO) transparent conductive thin films have been widely applied in optoelectronic devices such as solar cells, liquid crystal display and light emitting diodes because of its unique properties, not only its abundant raw materials, high thermal stability, low cost and non-toxicity but also its comparable electrical and optical properties to ITO thin films. The target of the thesis is to prepare AZO thin films with excellent performance by using magnetron sputtering technique at room temperature, which has many advantages such as high deposition rate, low substrate temperature, ect..AZO thin films have been prepared by DC magnetron sputtering at room temperature in the thesis. Effects of Al content on the structural, optical, and electrical properties of AZO thin films have been investigated in detail. Taguchi method was used to find the optimal deposition parameters. Thermal annealing effects on the improvement of optical, and electrical properties of AZO thin films have been discussed. And the properties of AZO thin films deposited on flexible organic substrates have also been studied.Results show that AZO thin films exhibit low resistivity(10-3 Ωcm) and high optical transmittance(> 80%) when Al content is 1.5-2 wt%. Taguchi design method has been successfully employed in AZO deposition process. Substrate-to-target distance plays the most significant role in resistivity of AZO thin films among the four deposition parameters including sputtering power, sputtering pressure, substrate-to-target distance and sputtering time. The optimal conditions are the substrate-to-target distance of 7.5 cm, the sputtering power of 180 W, the sputtering pressure of 0.3 Pa, and the deposition time of 30 min. Stable AZO films nearly in stochoimetric with low resistivity of 8.61×10-4 Ωcm,a mobility of 16.85 cm2/Vs and a carrier concentration of 4.30×1020 cm-3 were obtained. There is nearly no degradation in elelctrical and optical properties during the testing period of four months.Research on annealing of AZO films under different atmosphere showed that the atmosphere has little effect on the properties of the films. However, optical and electrical properties of AZO thin films can be enhanced in a certain content at annealing temperature of 100℃ for 60 minutes. A preliminary study on the growth of AZO films on flexible PET substrate at room temperature showed that optical and electrical properties of AZO thin films are independent on the types of substrates.