Pecvd Prepared Zno Thin Films And Optical Properties Of Quantum Dots

In this paper, we employ the plasma enhanced chemical vapor deposition (PECVD) to prepare high quality ZnO thin film at low temperature using a zinc organic source (Zn(C2H5)2) and carbon dioxide (CO2) gas mixtures. The effect of the substrate temperature and annealing temperature on the quality of ZnO thin films was studied in detail. In order to prepare the ZnO quantum dot embedded in SiO2 host film, we firstly prepared SiO2 thin film, and analysed the effect of ratio of gas flux on its optical quality. Furthermore, ZnO quantum dot was embedded in SiO2 host film under best condition. The effect of the annealing temperature on the quality of ZnO quantum dot was analysed. The follow is the main result of my experiment.1. The relationships between the substrate temperature and the properties of ZnO films were studied in detail, we obtained a (002) orientated high quality ZnO thin films with the full width at half maximum (FWHM) of 0. 2° located at 34. 42° at a low temperature of 180 ℃. The size of the ZnO nanocrystal grain was so little that the quantum confinement effect should be considered. That makes the band gap wide. Atom transfer rate is affected by the substrate temperature, and the average size of the ZnO nano crystal grain increases with the increasing substrate temperature resulting in the red shift of PL emission position and the narrowness of PL FWHM.2. The relationships between the annealing temperature and the properties of the ZnO films were studied in detail. We obtained a high quality ZnO thin film with the PL FWHM of 94 meV at 900℃.The free exciton binding energy deduced from the temperature-dependent PL spectra is about 59 meV at 900℃, suggesting that the film quality can be improved by annealing process.3. The relationships between the optical properties of SiO2 thin film and the preparing condition were studied. When the ratio of SiH4 to CO2 is 1/3, high optical quality SiO2 thin film was obtained. Under this condition, ZnO quantum dot was embedded in SiO2 thin film. The optical quality is affected by the annealing temperature. When the annealing temperature is 800℃,the stronger E2 mode at 437 cm-1 is obvious in Raman spectra. The ratio of the UV PL intensity to the visible PL intensity is 54, indicating the high quality of ZnO quantum dot was acquired.