Browsing by Author "Chen, Yuan-Tsung"

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Growth Mechanism of Self-Assembled TixWyO Nanotubes Fabricated by TiW Alloy Anodization
(2018-01-01)
Chang, Yung-Huang
;
Chen, Yuan-Tsung
;
Huang, Chien-Sheng
;
Lu, Chia-Ling
;
Lee, Shih-Hung
Nanostructures, such as nanodots and nanorods, have been fabricated by the anodization process with an aid of anodic aluminum oxide (AAO) for several decades. However, tubular nanostructures have not been reported by using an AAO-assistant anodization technology until now. In this study, we successfully synthesized self-organized TixWyO nanotubes with cap structures for the first time by using a two-step anodization process from Al-coated TiW alloy layers. The TixWyO nanotubes were observed only in the shaped pores of AAO with large enough pore size, and otherwise the nanostructures would become solid rods due to the aggregation of TixWyO. The wall of nanotubes was similar to 30% inside the pores and the other similar to 70% penetrated into the AAO template. Furthermore, no tubular nanostructures were found unless the percentage of W element in TiW alloys is larger than 50%, attributing to the formation of a void by oxygen bubbles arising from the oxidation reaction of tungsten metal. Besides, the height of the nanotubes is limited by an electric field of 0.82 GV/m due to the dielectric breakdown effect. Finally, a bottom-up growth mechanism at the oxide/metal interface is proposed, based on the observation of the cap structure on the top of the tubular architecture. (C) The Author(s) 2018. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License.
The effects of annealing temperature and sputtering power on the structure and magnetic properties of the Co-Fe-Zr-B thin films
(2012-11-01)
Chen, Guo-Ju
;
Jian, Sheng-Rui
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Jang, Jason Shian-Ching
;
Shih, Yung-Hui
;
Chen, Yuan-Tsung
The microstructure and magnetic properties of the amorphous Co-Fe-Zr-B thin films grown on glass substrates by dc magnetron sputtering are investigated using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) techniques. The Co-Fe-Zr-B thin films deposited at room temperature were annealed at temperatures ranged from 683 K to 773 K. Experimental results indicated that the coercivity (H-c) of the Co-Fe-Zr-B thin films is significantly influenced by residual stress and crystalline phases within the films. The correlation of the coercivity and the microstructure of Co-Fe-Zr-B thin films are discussed. After annealed at 683 K, the coercivity of the Co-Fe-Zr-B film was as low as 1.2 Oe. (C) 2012 Elsevier Ltd. All rights reserved.
The influences of H-2 plasma pretreatment on the growth of vertically aligned carbon nanotubes by microwave plasma chemical vapor deposition
(2008-06-01)
Jian, Sheng-Rui
;
Chen, Yuan-Tsung
;
Wang, Chih-Feng
;
Wen, Hua-Chiang
;
Chiu, Wei-Ming
The effects of H-2 flow rate during plasma pretreatment on synthesizing the multiwalled carbon nanotubes (MWCNTs) by using the microwave plasma chemical vapor deposition are investigated in this study. A H-2 and CH4 gas mixture with a 9:1 ratio was used as a precursor for the synthesis of MWCNT on Ni-coated TaN/Si(100) substrates. The structure and composition of Ni catalyst nanoparticles were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The present findings showed that denser Ni catalyst nanoparticles and more vertically aligned MWCNTs could be effectively achieved at higher flow rates. From Raman results, we found that the intensity ratio of G and D bands (I-D/I-G) decreases with an increasing flow rate. In addition, TEM results suggest that H-2 plasma pretreatment can effectively reduce the amorphous carbon and carbonaceous particles. As a result, the pretreatment plays a crucial role in modifying the obtained MWCNTs structures.