Browsing by Author "Kuo, Pai-Chia"

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Development and photoluminescence of ZnO-ZnS core-shell nanotube and nanorod arrays
(2007)
Kuo, Pai-Chia
;
Chen, San-Yuan
;
Bow, Jong-Shing
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材料科學與工程學系
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Department of Materials Science and Engineering
After the wurtzite ZbS nanorods were synthesized by hydrothermal treatment in the presence of ethylenediamine (en) aqueous solutions at 200oC, ZnS-ZnO core-shell nanorods were readily obtained by annealing ZnS nanorods under oxygen at 650oC for 3-5 min. A strong broad peak in the 450-550 nm visible range was clearly detected and its peak intensity could be greatly enhanced after the ZnO shell was developed on hydrothermal ZnS nanorods. On the other hand, using AAO as a template, ZnS-ZnO core-shell nanotubes could be synthesized using atomic layer deposition process along with the sulfuration conversion of the ZnO nanotube array. This ZnO-ZnS core-shell nanotube structure could be confirmed by x-ray photoelectron spectroscopy (XPS) analysis. In addition, an enhanced UV emission along with the reduced visible emission was also detected for the ZnO/ZnS core-shell nanotubes.
Synthesis and optical properties of ZnO-ZnS core-shell nanotube arrays
(2006-09-01)
Liao, Hung-Chou
;
Kuo, Pai-Chia
;
Lin, Chin-Ching
;
Chen, San-Yuan
;
材料科學與工程學系
Heterostructured ZnO-ZnS core-shell nanotube arrays with the diameters of 50-80 nm and lengths up to I mu m were synthesized by a two-step chemical reaction. First, the ZnO layer was grown by atomic-layer deposition. It was found that the preferred, growth orientation was strongly dependent on the substrate temperature. After sulfuration conversion from arrayed ZnO nanorods, the ZnS-ZnO composite arrays can be successfully prepared, as evidenced from transmission electron microscopy. This confirms that the ZnO-ZnS core-shell nanotube-arrayed structure has been fabricated. X-ray photoelectron spectroscopy analysis indicates that the binding energy of S 2p is the same as that of bulk single-crystal ZnS and that the Zn 2p(3/2) peak is shifted about 0.5 eV due to the formation of Zn-S bonds. Photoluminescence shows the relative-intensity ratio of ultraviolet emission (I-UV) to deep-level emission (I-DLE) for ZnO/ZnS core-shell nanotubes can be enhanced to be nine times that of original ZnO nanotubes. (c) 2006 American Vacuum Society.
Synthesis and photoluminescent properties of wurtzite ZnS nanorods by hydrothermal and co-precipitation methods
(2006-11-01)
Kuo, Pai-Chia
;
Wang, Hong-Wen
;
Chen, San-Yuan
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Nanorods of wurtzite ZnS were synthesized by a hydrothermal method at 200 degrees C and a co-precipitation method at room temperature in the presence of ethylenediamine (en) aqueous solutions. It was found that the wurtzite ZnS nanorods with uniform diameter around 80 +/- 20 nm, length about 300 +/- 100 nanometer appears at a proper concentration of en, unit [Zn] : [S] ratio, and an appropriate duration by the hydrothermal method. Much longer wurtzite ZnS nanorods with length from 300 to 2000 nm and diameter from 80 to 200 nm were obtained via the co-precipitation method. A very minor undecomposed ZnS center dot 0.5en phase coexisted with the wurtzite ZnS nanorods in the co-precipitation method was identified and arguably thought to be due to the low temperature used. ZnO coated ZnS core-shell structures were successfully fabricated by annealing the ZnS nanorods in an oxygen flow at 650 degrees C for 3-5 min. The coating of ZnO layer on ZnS nanorods results in a significant increase of photoluminescence (PL) intensity (30 times) at 490-500 nm visible regions for those of hydrothermal method and mild increase (double) for those of co-precipitation method.