Properties of aluminum doped zinc oxide thin film by sol-gel process

The thin films of transparent conductive aluminum doped ZnO have been deposited by the sol-gel process. In this study, important deposition parameters were thoroughly investigated in order to find appropriate procedures to grow large area thin films of low resistivity and high transparency at low cost for device applications. Experimental results indicated that the annealing temperature affected the crystal structure of the aluminum doped ZnO films considerably, but the controlling of effective doping concentration was the key point to achieve low film resistance by sol-gel process. It was adjusted by controlling the precursor concentration. Although the structure of our aluminum doped ZnO films did not have the preferred orientation along (002) plane, they had a high transmittance of over 87 % in visible region. In our experiments, the most suitable Al doped concentration was 1~4 mol%. The annealing temperature for the pre-heat treatment was 250 °C and post-heat treatment was 400-600 °C. The Al doped and undoped ZnO films are very uniform and compact. It is confirmed that the doping concentration and thermal treatment are important factor with electrical conductivity of ZnO films.