Optical properties of As doped ZnO thin films prepared by pulsed laser deposition technique

ZnO thin films are deposited on glass substrates at adapted experimental conditions during the pulsed laser deposition (PLD). The as-deposited thin films are attached by GaAs wafers and annealed at different temperatures and for different times. Transmittance and photoluminescence (PL) are measured to evaluate the As doping. With increasing annealing temperature and annealing time the transmission of films in the VIS range decreases. The band gap energies are determined by a linear fit of the absorption edge. In PL spectra, two PL emission peaks are found in all samples, one is the near band edge emission, and the ether is green emission. The annealing decreases the intensity of the green emission. The aging is found in ZnO thin films by PL measurements. As time goes on, the green emission peak decreases, and the near band emission peak is enhanced because of the decrease of oxygen vacancies in thin films.