Photoluminescence Studies of ZnO thin films grown by atomic layer epitaxy

ZnO thin films have been grown on sapphire substrates by the atomic layer epitaxy technique using diethyzinc and H2O as reactant gases at substrate temperatures of 170°C and 400°C and annealed at temperatures of 800–1000°C. In order to investigate the effect of annealing treatment on the optical properties of ZnO films, the films have been annealed at various annealing temperatures after deposition. After the annealing treatment the optical properties of ZnO thin films were characterized by photoluminescence (PL). A strong free exciton emission with a weak defect-band emission in the visible region was observed at room temperature. Based on the full-width at half-maximum measurement of the free exciton emission of 67.54 meV have been made at room temperature. Both the PL intensity peaks in the UV light and visible light regions are increased by annealing the ZnO film in an oxygen atmosphere. In contrast, only the PL intensity peak in the UV light region is selectively increased by annealing it in a nitrogen atmosphere. Also, the ZnO film deposited at 170°C shows better PL characteristics than that deposited at 1000°C.