Effects of annealing and laser irradiation on optical and electrical properties of ZnO thin films

Zinc oxide (ZnO) thin films were deposited on a sapphire (001) by pulsed laser deposition technique at room temperature. The profound changes of ZnO thin films had been observed. The large surface morphology difference of ZnO thin films between annealing and laser irradiation was found. Meanwhile, the dependence of photoluminescence (PL) spectra on annealing temperature and laser irradiation energy had been investigated. As the annealing temperature and laser irradiation energy increased, the PL intensity of visible luminescence decreased. In contrast, the intensity of ultraviolet (UV) emission increased largely with the increasing laser energy. However, annealing treatment had no effect on the UV emission behavior. The results from Hall measurements and the variation of visible emission indicated annealing and laser irradiation had the same influence on controlling the concentration and some native defects in ZnO thin films. Besides, the thermal and photochemical effects of KrF excimer led to an enormous accumulation of zinc interstitial, and the carrier concentration increased up to six orders of magnitude. Furthermore, the origins of UV and visible emissions were discussed.