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Preparation And Properties Of ZnO Quantum Dots By MOCVD

Posted on:2007-04-26Degree:MasterType:Thesis
Country:ChinaCandidate:L M YangFull Text:PDF
GTID:2178360182988779Subject:Materials Physics and Chemistry
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ZnO is a wide direct-gap semiconductor with a hexagonal crystal structure of wurtzite. It is a compound semiconductor with direct band gap of 3.37 eV at room temperature, and a large exciton binding energy of 60 meV. With optical pumped untraviolet (UV) emitting reported, ZnO attracts as much as GaN in the fields of optoelectronic research. Compared with GaN, ZnO with a much higher binding energy can be synthesized at much lower temperature, which promises strong photoluminescence from bound emission at room temperature. In recent years, ZnO quantum dots, a new nanostructure material indicating significant exciton effect due to quantum confinement effects, has attracted a lot of attention because of its good optical, electrical properties. It has gained more and more attention in optoelectronic devices such as UV light-emitting diodes, laser diodes, and transparent conducting films, LEDs and LDs. The fabrication of ZnO quantum dots with high quality is the base subject in the research of ZnO QDs-based devices.In this thesis, based on a comprehensive review of the research history and current status of ZnO quantum dots preparation and relative theory of Quantum, we conducted a detailed study of ZnO quantum dots grown on Si (111) substrates by MOCVD and its optical properties.The main content of this thesis is listed as follow:1. High quality self-assemble ZnO quantum dots (QDs) have been successfully grown on the Si (111) substrates by metalorganic chemical vapor deposition (MOCVD). The diameter of ZnO QDs is about 10 nm in average. The processes are well repeatable, making the further researches on its properties possible.2. Room-temperature photoluminescence spectra reveal that the ZnO QDs exhibit a band gap blue shift because of the quantum confinement effects. The diffraction angle of the (002) peak in XRD profile is in well agreement with the ZnO bulk single crystal.3. Systematically studied the appearance of ZnO QDs that changed by thetemperature of substrate and the growth time. On one hand, the difference in sizes increases with the grown temperature becoming higher, while the density of ZnO QDs decreases, on the contrary. On the other hand, the density of ZnO QDs increases while the difference in sizes changed slowly with the time growing. As a result, by adjusting the growth temperature or the growth time, we can control the density of the ZnO QDs.4. Studied how the densities and diameters of the ZnO quantum dots changes while the Zn flow rate and flow directions changes, respectively, as well as the N2O or NO is used as the oxygen source.5. Studied other factors that influence the surface morphology of ZnO quantum dots, such as ZnO quantum dots grown by PE-MOCVD compared with MOCVD.In a word, we report on the self-assemble nano-meter ZnO quantum dots on Si (111) substrates grown by MOCVD. We can control the densities and sizes of ZnO QDs, mainly by altering the proper growth conditions.
Keywords/Search Tags:ZnO, quantum dot, MOCVD, quantum confinement effect, blue shift
PDF Full Text Request
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