Photoluminescence study of ZnO thin films deposited by pulsed laser ablation

Zinc oxide (ZnO) thin films were fabricated by pulsed laser deposition (PLD) technique on Si (001) substrates. Two types of targets, ZnO target and Zn target, were used and the results are compared. The ambient gas was oxygen, and the gas pressure was varied from 1 mTorr to 10 Torr. The substrate temperature was controlled in the range of RT-800 degrees C. Optimum oxygen pressure was found to be about 1 Torr and substrate temperature to be about 600 degrees C for both ZnO and Zn targets, and at these conditions a strong ultraviolet photoluminescence (UV PL, lambda similar to 380 nm) appeared with little visible PL. The UV PL was stronger for ZnO target at optimum substrate temperature, but it was stronger for Zn target at lower ternperatures. The films grown at RT were post-annealed at 600 degrees C. Post-annealing had little effect on UV luminescence and the structure of ZnO film for both types of targets.