Browsing by Author "Yang, Ching-Jung"

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Characterization and field-emission properties of carbon nanotube arrays in nanoporous alumina template and on blank Si substrate
(2006-11-15)
Yang, Ching-Jung
;
Chen, Chih
;
Shieh, Jia-Min
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材料科學與工程學系
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Department of Materials Science and Engineering
Ordered carbon nanotube (CNT) arrays were synthesized within anodized aluminum oxide template by thermal decomposition of hydrocarbon precursor with hydrogen ambient at growth temperature as low as 500 degrees C. Excess hydrogen in precursor mixture enables a steady supply of mobile hydrocarbon reactant which promotes facile solid-phase diffusion. The activation energy for CNT growth was determined to be 0.55 eV, a number smaller than 1.02 eV for similar precursor in nitrogen ambient. Moreover, CNTs grown in anodized aluminum oxide nanopores in this low temperature process were found to exhibit unusually high field-emission current of 100 mA/cm(2) at 8 V/mu m. (c) 2006 American Institute of Physics.
Fabrication of anodic aluminum oxide film on large-area glass substrate
(2007)
Yang, Ching-Jung
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Liang, Shih-Wei
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Wu, Pu-Wei
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Chen, Chih
;
Shieh, Jia-Min
Fabrication of anodic aluminum oxide (AAO) on 4 in. glass substrate was demonstrated. Using unique structure with quadruple contacts as electrode support during anodization, we reported gradual transformation from opaque aluminum to transparent AAO over the entire substrate. In contrast, partial transformation was observed with typical single contact approach where growth of insulating AAO inhibited subsequent anodization by interrupting current flow from the contact point. Results from optical spectroscope revealed moderate reduction in transmittance after AAO formation. Successful development of large-area AAO on glass substrate opens up opportunities for AAO templated devices that require a large footprint. (c) 2007 The Electrochemical Society.
Fabrication of ordered Ta(2)O(5) nanodots using an anodic aluminum oxide template on Si substrate
(2007-04-01)
Yang, Ching-Jung
;
Chen, Chili
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Wu, Pu-Wei
;
Shieh, Jia-Min
;
Wang, Shun-Min
Ordered arrays of Ta(2)O(5) nanodots were prepared using anodic aluminum oxide (AAO) as a template to support localized oxidation of TaN. Films of TaN (50 nm) and Al (1.5 mu m) were deposited successively on p-type Si wafers and followed by a two-step anodization process at 40 V using oxalic acid as the electrolyte. The first anodization promoted growth of irregular AAO from overlying Al film. After chemical etching, the second anodization was performed to develop well-organized AAO channels and initiate oxidation of underlying TaN film to form tantalum oxide nanodots at the AAO pore bottoms. X-ray photoelectron spectroscopy results confirmed the chemical nature of nanodots as stoichmetric Ta(2)O(5), X-ray diffraction demonstrated the amorphous characteristic of Ta(2)O(5). As shown in field-emission scanning electron microscopy and transmission electron results, the Ta(2)O(5) nanodots exhibited a hillock structure 80 nm in diameter at the bottom and 50 nm in height. We also synthesized 30-nm nanodots by adjusting AAO formation electrochemistry. This demonstrates the general applicability of the AAO template method for nanodot synthesis from nitride to oxide at a desirable size.
Low-temperature growth of ZnO nanorods in anodic aluminum oxide on Si substrate by atomic layer deposition
(2007-01-15)
Yang, Ching-Jung
;
Wang, Shun-Min
;
Liang, Shih-Wei
;
Chang, Yung-Huang
;
Chen, Chih
Low-temperature growth of self-organized ZnO nanorods on Si substrate is achieved using anodic aluminum oxide and atomic layer deposition at 250 degrees C without catalyst or seed layer. Photoluminescence spectrum indicates that the ZnO nanorod arrays exhibit a blue/green luminescence at 480 nm. In addition, the nanorod arrays demonstrate excellent field-emission properties with a turn-on electric field of 6.5 V mu m(-1) and a threshold electric field of 9.8 V mu m(-1), which are attributed to the perfectly perpendicular alignment of ZnO nanorods to the Si substrate. (c) 2007 American Institute of Physics.