| Summary: | 博士 === 國立成功大學 === 電機工程學系碩博士班 === 93 === Three subjects on the II-VI compound phosphors have been studied. The first one is the synthesis of the traditional ZnS phosphors. With different synthesis temperatures, relation between the PL intensity and the synthesis temperature is investigated. And doping with active centers, the different emission wavelengths are obtained. On the second subject, the results obtained in the first subject are applied to synthesize the II-VI ZnS and ZnO nanophosphors. By controlling the particle size and suitable dopant, a near-white-light emission phosphor is obtained in our experiment. On the final subject, the VLS method is adopted to synthesize the II-VI ZnS and ZnO nanowires. Simple introductions of the above three subjects are represented below.
On the first one subject, transformation temperature of the ZnS phosphor is determined using the X-ray diffraction patterns and the Raman spectra. And form the PL spectra, relation between the synthesis temperature and the PL intensity is discussed. In our experiments, the hexagonal ZnS emits the strongest PL intensity and possesses the best emission efficiency. As doping with Mn2+, an emission wavelength around 580 nm is observed and consistent with the data reported by other research groups. Varying the dopant concentration, the concentration quenching effect is observed and the 3 mol% Mn2+ doped ZnS phosphor possesses the best emission efficiency in our studies. Moreover, the rare-earth element is also doped in the ZnS matrix. An orange emission originated form the Er3+ luminescence center is observed in our measurements. This is not consistent with the data reported by others. In those reports, the dopant Er3+ only enhances the emission intensity and emits no light. The detail is discussed in this dissertation.
On the second subject, two methods are adopted to synthesize the II-VI nanophosphors. One is the chemical precipitation method and other, is the low-temperature solid state method. The different atomic ratio of S/Zn is introduced to discuss the emission mechanism of ZnS phosphor in the chemical precipitation method. With smallest value of the atomic ratio, the ZnS phosphors with the smallest particle size are obtained. Besides, a near-white-light emission phosphor is obtained by controlling the particle size and the suitable dopant. Using Mn2+ as the luminescence center, the near-white emission phosphor with 3.9 nm in diameter is obtained at 100℃. By oxidizing the ZnS nanophosphors at the air atmosphere, the ZnO nanophosphors are obtained and possess a green emission in the PL spectra. Mean diameter of the ZnO nanophosphors is about 60 nm.
On the last subject, the VLS method is adopted to synthesize the II-VI ZnO and ZnS nanowires. By controlling the pressure in the quartz tube, the ZnO nanowires are successfully obtained at such low temperature (350℃). And the ZnO nanowires emit a green light at room temperature. Moreover, a brand-new method is utilized to align the nanowires only in the quartz tube without other complicated instruments or synthesis processes.
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