Browsing by Author "Hwang, J."

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Gravity-assisted chemical vapor deposition of vertically aligned single-walled carbon nanotubes
(2007)
Yeh, C. M.
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Chen, M. Y.
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Gan, J.-Y.
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Hwang, J.
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Lin, C. D.
Temperature and CH4/H-2 ratio of gas-flow rates are the two factors that strongly affect the qualities of vertically aligned single-walled carbon nanotubes (SWCNTs) in gravity-assisted chemical vapor deposition (CVD). The qualities of SWCNTs and other carbon products grown by gravity-assisted CVD were characterized by scanning electron microscopy and Raman spectroscopy. At temperatures between 850 and 900 degrees C, SWCNTs of very good quality stand alone on the substrate. At other temperatures, nanofibers or irregular islands of carbon are present on the substrate. The CH4/H-2 ratio influences the quality of SWCNTs more abruptly than temperature. At low ratio, no carbon nanotube is formed. The window of CH4/H-2 ratio for the growth of vertically aligned SWCNTs ranges from 160:80 to 160:40. At a ratio higher than 160:40, multiwalled CNTs replace SWCNTs and become the dominant product. (C) 2007 The Electrochemical Society.
Growth of 3C-SiC on Si(111) using the four-step non-cooling process
(2010-08-02)
Liu, Jui-Min
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Chen, Wei-Yu
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Hwang, J.
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Huang, C-F.
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Wang, Wei-Lin
A modified four-step method was applied to grow a 3C-SiC thin film of high quality on the off-axis 1.5 degrees Si(111) substrate in a mixed gas of C(3)H(8), SiH(4) and H(2) using low pressure chemical vapor deposition. The modified four-step method adds a diffusion step after the carburization step and removes the cooling from the traditional threestep method (clean, carburization, and growth). The X-ray intensity of the 3C-SiC(111) peak is enhanced from 5 x 10(4) counts/s (the modified three steps) to 1.1 x 10(5) counts/s (the modified four steps). The better crystal quality of 3C-SiC is confirmed by the X-ray rocking curves of 3C-SiC(111). 3C-SiC is epitaxially grown on Si( 111) supported by the selected area electron diffraction patterns taken at the 3C-SiC/Si(111) interface. Some (111) stacking faults and twins appear inside the 3C-SiC, which may result from the stress induced in the 3C-SiC thin film due to lattice mismatch. The diffusion step plays roles in enhancing the formation of Si-C bonds and in reducing the void density at the 3C-SiC/Si(111) interface. (C) 2010 Elsevier B.V. All rights reserved.
Liquid crystal alignment on the a-C : H films by Ar plasma ion immersion
(2007-07-31)
Chang, S. J.
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Wu, K. Y.
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Yang, Y. H.
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Hwang, J.
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Wu, Hsin-Ying
A plasma ion immersion treatment has been developed to enhance the liquid crystal (LC) alignment on the hydrogenated amorphous carbon (a-C:H) layer in an inductively coupled plasma (ICP) chamber. No LC alignment was observed for the a-C:H layer tilted at an angle of 0 degrees during the bombardment with plasma ions. The LC alignment occurs for the a-C:H layer tilted at an angle of 30 degrees or 60 degrees. Their pretilt angles (similar to 1.4 degrees) are approximately the same. The azimuthal anchoring strength is 1.98 x 10(-6) J/m(2) at a tilted angle of 30 degrees and 1.14 x 10(-4) J/m(2) at a tilted angle of 60 degrees. The mechanism for the LC alignment is attributed to the oblique incidence of ions within the matrix sheath of non-uniform thickness near the a-C: H surface under a negative pulse bias. The matrix sheath of non-uniform thickness is confirmed by the plasma density distribution in the ICP chamber and the X-ray photoemission spectra across the a-C:H layer. (C) 2007 Elsevier B.V. All rights reserved.