Effect of annealing temperature on the optical and electrical properties of aluminum doped ZnO films

Aluminum doped ZnO thin films were successfully deposited on the silicon substrates by spin coating method. The effects of an annealing temperature on electrical and optical properties were investigated for 1.5 at.% of aluminum. Refractive index profile has been obtained for the film annealed at 350 °C using ellipsometry and it has shown minimum refractive index of 1.95 and maximum value of 2.1. Thickness profile shows quite good uniformity of the film having minimum thickness value of 30.1 nm and maximum value of 34.5 nm. Maximum conductivity value obtained was 4.63 Ω ⁻¹-cm ⁻¹ for the film annealed at 350 °C. Maximum carrier density of 2.20 × 10 ¹⁷ cm ⁻³ was deduced from the Hall measurement and Fourier transform infrared spectroscopy clearly reveals major peak at 407 cm ⁻¹ in the spectra associated with the ZnO bond.