The effect of annealing temperature on the optical properties of aluminum-doped zinc oxide nanostructures

Abstract

The AZO nanostructure samples used in this investigation were made on a glass substrate by spin-coating utilizing an inexpensive sol-gel method. We investigated the effects Effect of annealing temperature on AZO (aluminum doped with zinc) thin film on optical characteristics. The films were annealed in an air environment at (350, 400, 450, 500, and 550) °C for four hours. The measurements of optical transmittance and absorbance were made in the 300–800 nm wavelength range using a single beam spectrophotometer. When the temperature of annealing increases, the optical band gap decreases from 3.36 eV to 3.2 eV and the UV–Vis absorption spectra exhibit a small red shift. The AZO films have transmittances over 35% in the IR region of spectrum for 350°C after annealing sample, but rises to 95% at 550°C after annealing at higher temperatures. With a rise in annealing temperature, AZO film extinction coefficient increased. An increase in annealing temperature results in an increase in both optical and electrical conductivities. The AZO films were characterized with respect to their optical properties using UV-vis spectroscopy, and the optical band gap was computed using the Tauc method. The optical test indicated a direct nature of the optical transition, with an average band gap energy propensity to decrease from 3.36 to 3.20 eV when the temperature was elevated from 350 to 550 °C during the temperature annealing process. The experimental results indicate that the properties of the AZO films were affected by the annealing.