Effects of annealing atmosphere on thermoelectric signals from ZnO films

Zinc oxide epilayer films were grown on vicinal cut sapphire substrates by pulsed laser deposition with in situ annealing oxygen pressures varied from 0 to 10 × 10 3 Pa. The best crystalline quality was obtained for ZnO layer with annealing oxygen pressure of 6 × 10 3 Pa. Laser induced thermoelectric voltage (LITV) were observed along the tilting angle orientation of the substrate when the pulsed KrF excimer laser of 248 nm were irradiated on the films. The largest LITV signal was measured for the film grown at 6 × 10 3 Pa annealing oxygen pressure. According to the measured LITV signals, Seebeck anisotropy was evaluated and was found to range from 3 to 12 μV/K for ZnO films annealed at different oxygen pressures from 2 to 10 × 10 3 Pa. It is suggested that oxygen ambient plays an important role in the electronic properties of the ZnO films.