Effect of annealing on photoluminescence of ZnO: Al thin films prepared by sol-gel method

Al doped ZnO thin films were fabricated on quartz substrates by sol-gel method. An X-ray diffraction (XRD) was used to analyse the structural properties of the thin films. All the thin films have a preferential c-axis orientation, which enhances in the annealing process. From the spectrometer transmittance data, the optical absorption of AZO films was found to have a redshift with an increase in annealing temperature. From the PL measurement the near band edge (NBE) emission and deep-level (DL) emission are observed in unannealed AZO thin films. However, after annealing at high temperature, the DL emissions of the thin films are depressed. As the annealing temperature increases, the peak of NBE emission has a shift to region of lower photon energy, which is coincident with the results from