PLD Of ZnO Thin Film Structure And Luminescence Properties Study

ZnO is a semiconductor material with wide direct band gap of 3.37eV and a large exciton binding energy of 60meV at room temperature. Theoretically, it can realize stimulated UV emission at RT, which makes it a promising material for using in ultraviolet light-emitting and laser diodes. In this paper, a series of ZnO films were prepared by using a KrF excimer laser at different deposited condition. Through the research of the structural and optical properties of ZnO films, optimized conditions for growing ZnO films were obtained. The results suggested that high quality ZnO films with highly c-axis orientation could be prepared by PLD. By changing different deposited condition some points have been obtained.(1) The ZnO films were prepared at different substrate temperature. XRD results suggested that all samples have c-axis orientation. As the substrate temperature changes from 400℃ to 700 ℃, the FWHM of ZnO (002) diffraction peaks become narrower. The crystallinity of the samples is improved. The surface morphology of the sample grown at 400 ℃ has double structure and the sample grown at high temperature has ring structure, the sample grown at 500℃ has the strongest UV emission. As the substrate temperature increasing, the intensity of UV emission decreases. The article investigates the effect of substrate temperature on the UV emission. The UV luminescence intensity strongly depended on the stoichiometry in the ZnO film rather than the micro-structural quality of the crystal.(2) The ZnO films were prepared at different oxygen partial pressure. As the oxygen pressure for the thin film deposition increases from 10 Pa to 100 Pa, the FWHM of (002) diffraction peaks become larger from 0.19° to 0.43°. The crystallinity of the samples degrades, but the intensity of UV emission improves. The surface morphology of the sample grown at 100Pa has leaves structure with layer symmetry. The UV luminescence intensity strongly depended on the stoichiometry in the ZnO film rather than the micro-structural quality of thecrystal. The green emission may generate from Ozn-(3) The films were prepared on Si substrate with ZnO buffer lay. The ZnO buffer lay was prepared at different substrate temperature. The FWHM of ZnO (002) diffraction peaks of these samples become narrower and the crystallinity of the samples degrades. The buffer lay reduce the lattice mismatch between ZnO and Si. The results show that ZnO buffer layer improves the crystalline quality and the surface morphology of the films relative to the films grown directly on silicon substrates.