Quantum confinement structures are attractive for their unconventional size dependence of the optical and electrical properties. There are still challenges to control the size uniformity for the application. The thesis studies the correlation between the size distribution of CdSe/ZnS quantum dots (QD), and the fluorescence properties to understand the shape and size influences of their fluorescence properties.
Results from the transmission electron microscopy (TEM) provide the structure and size distribution of the samples. Excitation dependent fluorescence spectra as well as the PL excitation at various emission wavelength confirm that the inhomogeneous distribution of the samples. The results show that the samples are mostly composed of QDs with quasi-spherical structure (aspect ration between 1.1 and 1.5 ;76%) and spherical structure ( aspect ratio < 1.1; 12.8%). In addition, it exhibits a distribution of the long axis of 5.4nm¡Ó1.3nm.
By measuring the fluorescence spectra of individual QDs, we construct the distribution. The peaks of the fluorescence spectra show a Gaussian distribution with center at 615.7 nm and width 13.8 nm. In addition, the spectra exhibit a width of 19.7¡Ó8.0nm. This is consistent with the ensemble measurement of the fluorescence from a solution (peak at 616 nm, and width 25 nm). Results of the fluorescence lifetime on the individual QDs indicate the lifetime distribution of 10.3¡Ó5.6ns.
Further analyze the size distribution by constructing the size ¡V fluorescence spectrum relationship. By analysis the distribution of the fluorescence spectra, it results the corresponding size distribution of width 0.7 nm. This is much narrower than the size distribution of the long axis measured by TEM, but is more consistent with the corrected size distribution considering the short axis contribution. We conclude that the deviation results from the non-spherical structures in the samples.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0805105-074009 |
| Date | 05 August 2005 |
| Creators | Lin, Wen-Bin |
| Contributors | Chao-Kuei Lee, S. J. Bai, Jui-Hung Hsu |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0805105-074009 |
| Rights | withheld, Copyright information available at source archive |
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