Sol ageing effect on the structural, optical and electrical properties of Ga-doped ZnO thin films

Gallium-doped zinc oxide thin films (GZO) were grown on a glass substrate by a simple sol-gel process and spin coating technique. The effects of sol ageing time on the structural, optical and electrical properties of the GZO films were investigated. Experimental results showed that the microstructure, optical transmittance and electrical resistivity of the GZO films depend directly on the sol ageing time. XRD studies revealed the polycrystalline nature of the films with the c-axis grain orientation. Optical transmittance of the films was higher than about 82% within the visible region and the optical direct band gap was increased with increasing sol ageing time. A minimum resistivity of 3.16 x 10(-5) Omega m was observed in the film deposited by a sol aged for 48 h. These results indicate that an appropriate ageing time of the sol is important for the improvement of the properties of GZO films derived from sol-gel method.