II-VI族化合物半導體奈米粒子合成、鑑定、光物理性質及其應用之研究
Synthesis, Characterization, Photophysical Properties and Applications of II-VI Compound Semiconductor Nanocrystallites
Date Issued
2005
Date
2005
Author(s)
Chen, Chun-Yen
DOI
en-US
Abstract
In this thesis, we focus on the syntheses and characterization of various II-VI compound semiconductor nanocrystallites, including type-I and II quantum dots (QDs), either by a newly developed one-pot synthesis or via the modified methodologies on two-step approaches. Our long-term goal is to exploit this chemically modified QDs in fundamental approaches such as relaxation dynamics and energy/charge transfer processes, or practical application such as bio labeling. Prior to present my work, a general review in terms of chronic progress, fundamental and application of nanoscience is elaborated in Chapter 1.
Through the four-year efforts, I have successfully prepared highly luminescent type-I quantum dots (QDs) with narrow emission spectra. The resulting nanoparticles have been characterized by their corresponding optical properties, EDX, XPS, TEM and powder-XRD. These approaches are highly reproducible, and the average quantum efficiency of as high as 0.5~0.7 can be achieved (Chapter 2). Phase transfer of the QDs from organic solvents to aqueous media was also achieved. The mercaptoacid-capped CdSe/ZnS QDs unveiled remarkable metal ion (e.g. Hg2+) recognition, in which the highly luminescent QDs were drastically quenched upon the addition of Hg(ClO4)2. Although an actual mechanism is pending for resolution, a tentative mechanism is proposed on the basis of redox type of reaction. The practical application onto the solid matrix was also elaborated in Chapter 3.
In Chapters 4, 5 and 6, we then switched our gear toward the synthesis and characterization of type-II QDs, in which the carriers are no longer confined in the core. One of our goals is to utilize the spatial separation between core and shell so that the electron can be ejected out of the shell for further application such as photovoltaic cells. Three classes of type-II QDs, namely CdSe/ZnTe, CdTe/CdSe and CdSe/ZnTe/ZnS, were prepared and characterized, and their corresponding spectroscopes and femtosecond relaxation dynamics were examined comprehensively. Of particular interest is the observation of the size-dependent relaxation dynamics of the excited core electron as well as the acoustic phonon oscillation (in CdTe/CdSe) for the interband emission, which is believed to spark a broad spectrum of interest in the relevant fields.
Subjects
半導體
奈米
量子點
硒化鎘
水溶性
飛秒
semiconductor
nano particle
quantum dots
CdSe
water soluble
femtosecond
SDGs
Type
thesis
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