Browsing by Author "Chang, JK"

Now showing 1 - 4 of 4

Anodic aluminum oxide template assisted growth of vertically aligned carbon nanotube arrays by ECR-CVD
(2004-11-01)
Chen, PL
;
Chang, JK
;
Kuo, CT
;
Pan, FM
;
材料科學與工程學系
Highly aligned carbon nanorubes (CNTs) have been successfully grown in vertical channels of the anodic aluminum oxide (AAO) template by microwave plasma electron cyclotron resonance chemical vapor deposition (ECR-CVD). Nanoporous AAO templates with hexagonal pore pattern were prepared by the two-step anodization of A] films. Following the electroplating of Co catalyst into the pore bottom, multiwalled CNTs were synthesized in the ECR-CVD system using a gas mixture of CH4 and H-2. The microstructure of the CNTs was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The CNTs with a very high packing density and a uniform size distribution are well graphitized, and Co particles embedded at their tips implies the tip growth mechanism. The segments of CNTs stretching out of the AAO nanopores still maintain relatively good alignment, and have a very slow growth rate, which allows us to obtain reproducible tube length by tuning the growth time. Field emission measurements of the CNTs showed derivable electron emission properties, attributed to their uniformity in size, good alignment, and good graphitization properties. (C) 2004 Elsevier B.V. All rights reserved.
Fabrication and field emission characteristics of highly ordered titanium oxide nanodot arrays
(2005)
Chen, PL
;
Huang, WJ
;
Chang, JK
;
Kuo, CT
;
Pan, FM
A field emission triode device has been fabricated using self-organized nanodot arrays as the electron emission source. Uniform nanodot arrays of titanium oxide were prepared from the Al/Ti film stack on silicon substrates by electrochemical anodization. The field emission triodes with titanium oxide nanodot emitters exhibited a low gate turn-on voltage of 45 V and high emission current density of 25 mA/cm(2) at 120 V. The excellent electric properties and easily controllable fabrication process of the nanodot triodes show potential applications for field emission displays and vacuum microelectronics. (c) 2005 The Electrochemical Society.
Field emission of carbon nanotubes on anodic aluminum oxide template with controlled tube density
(2005-03-21)
Chen, PL
;
Chang, JK
;
Kuo, CT
;
Pan, FM
;
材料科學與工程學系
The tube number density of aligned carbon nanotubes (CNTs) grown over the nanoporous anodic aluminum oxide (AAO) template can be directly controlled by adjusting the CH4/H-2 feed ratio during the CNT growth. We ascribe the variation of the tube density as a function of the CH4/H-2 feed ratio to the kinetic competition between outgrowth of cobalt-catalyzed CNTs from the AAO pore bottom and deposition of the amorphous carbon (a-C) overlayer on the AAO template. A pore-filling ratio of 18% to 82% for the nanotubes overgrown out of nanopores on the AAO template can be easily achieved by adjusting the CH4/H-2 feed ratio. Enhanced field emission properties of CNTs were obtained by lowering the tube density on AAO. However, at a high CH4 concentration, a-C by-product deposit on the CNT surface can degrade the field emission property due to a high energy barrier and significant potential drop at the emission site. (C) 2005 American Institute of Physics.
Tube number density control of carbon nanotubes on anodic aluminum oxide template
(2005-03-01)
Chen, PL
;
Chang, JK
;
Pan, FM
;
Kuo, CT
;
材料科學與工程學系
We demonstrate that the tube number density of well-aligned carbon nanotubes (CNTs) grown over the nanoporous anodic aluminum oxide (AAO) template can be directly controlled by adjusting the CH4/H-2 feed ratio during the CNT growth in a microwave plasma electron cyclotron resonance chemical vapor deposition (ECR-CVD) system. During the CNT growth, the nanotube growth and the amorphous carbon deposition on the AAO pore wall take place simultaneously. The amorphous carbon sediment will gradually cover up the AAO nanopores and prevent the nanotubes to grow out of the nanopores. By adjusting the CH4/H(2)feed ratio, one can control the amount of the deposited amorphous carbon and thus the number of CNTs grown over the AAO nanopores. It was found that the CNT density decreases linearly with increasing the CH4 concentration. The CNT density decreased by a factor of about 4.5 when the CH4 concentration increased from 9% to 91%. (c) 2004 Elsevier B.V. All rights reserved.