Browsing by Author "Chou, J. W."

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Fluorescence signals of core-shell quantum dots enhanced by single crystalline gold caps on silicon nanowires
(2009-04-22)
Christiansen, S. H.
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Chou, J. W.
;
Becker, M.
;
Sivakov, V.
;
Ehrhold, K.
We use nanoscale (20-300 nm in diameter) single crystalline gold (Au)-caps on silicon nanowires (NWs) grown by the vapor-liquid-solid (VLS) growth mechanism to enhance the fluorescence photoluminescence (PL) signals of highly dilute core/shell CdSeTe/ZnS quantum dots (QDs) in aqueous solution (10(-5) M). For NWs without Au-caps, as they appear, for example, after Au etching in aqua regia or buffered KI/I(2)-solution, essentially no fluorescence signal of the same diluted QDs could be observed. Fluorescence PL signals were measured using excitation with a laser wavelength of 633 nm. The signal enhancement by single crystalline, nanoscale Au-caps is discussed and interpreted based on finite element modeling (FEM).
Fluorescence signals of quantum dots influenced by spatially controlled array structures
(2009-10-14)
Chou, J. W.
;
Lin, K. C.
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Tang, Y. T.
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Hsueh, F. K.
;
Lee, Yao-Jen
Fluorescence signals of quantum dots (QDs) influenced by different array structures of gold-coated silicon nanorods (SiNRs) were investigated via experimental observations and two-dimensional (2D) finite element method (FEM) simulations. On the densest gold-coated SiNRs array structure, the highest QD fluorescence quenching rates were observed and on the sparsest array structure, the highest QD fluorescence enhancement rates were observed. By developing a new technique which obtains the optical image of the array structures without losing information about the QD locations, we were able to further investigate how the QD fluorescence is influenced by spatially controlled array structures.
Observation of localized surface plasmons in spatially controlled array structures
(2009-07-29)
Chou, J. W.
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Lin, Kao-Chin
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Lee, Yao-Jen
;
Yuan, Chi-Tsu
;
Hsueh, Fu-Kuo
We observed the reflectance spectra of three different nano-scale array structures of Au-coated silicon nanorods. The trends of the reflectance spectra indicate that the localized surface plasmon modes can be spatially controlled by manipulating geometric parameters, namely the lattice constants of the array. In addition, the experimental results were compared with 2D numerical simulations based on the finite element method. Satisfactory agreement between the experimental observations and numerical results was obtained.