Growth and Optical Properties of ZnO-ZnS core-shell nanostructure
| Autor: | Chih-Nan Lin, 林志南 |
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| Rok vydání: | 2009 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 97 In this research, a three-step process was used to grow ZnO-ZnS core-shell nanostructure on the c-plane sapphire. In the first step, a thin ZnO buffer layer was grown on the c-plane sapphire by pulsed laser deposition (PLD). Then, ZnO nanorods were grown on the c-plane sapphire with ZnO buffer layer by physical vapor-phase transport process (PVT). The diameters of ZnO nanorods were about 40 to 50 nm. In the final step, ZnO-ZnS core-shell nanostructures were formed by PLD of ZnS onto the ZnO nanorods. The morphology and crystal structure of the as-synthesized product were examined using SEM and HRTEM. From these images, the lengthes of ZnO-ZnS core-shell nanorods were about several thousand nanometers. The thickness of the core was about 50 to 60 nm and the thickness of the shell was about 8 to 12 nm. By the XRD patterns, it showed that all the peaks could be attributed to ZnS and ZnO. By the EDS patterns, the S element was found to be present, which was powerful evidence for successful incorporation of ZnS onto ZnO nanorods. Temperature-dependent PL spectra of ZnO-ZnS core-shell nanorods exhibited strong emission from ZnO. The other peak was at 2.5eV. This peak was due to the electronic recombination from the ZnO CBM(3.3eV) to the ZnS VBM(0.8eV). It had blue shift emission when the temperature was increasing. We must discuss this peak, because the photon energy of the peak was close to that of the defect emission. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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