Browsing by Author "Tai, Han-Chung"

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Growth and field emission characteristics of carbon nanotubes using Co/Cr/Al multilayer catalyst
(2007-07-01)
Cheng, Huang-Chung
;
Lin, Kao-Chao
;
Tai, Han-Chung
;
Juan, Chuan-Ping
;
Lai, Rui-Ling
A multilayer catalyst, Co/Cr/Al, was employed to synthesize carbon nanotubes (CNTs) at atmospheric pressure by thermal chemical vapor deposition (thermal CVD). The relative growth rates, calculated on the basis of the average lengths of nanotubes grown at different temperatures, were utilized to estimate an activation energy of 0.84eV for the multilayer catalyst. Such a low activation energy implies that the nucleation and growth of nanombes could be effectively enhanced via the multilayer catalyst due to the well-distributed small catalytic nanoparticles by Al supporting layer and higher activity by Cr co-catalyst layer. It was also found that nanotubes grown using this configuration at 500 degrees C exhibited excellent field emission characteristics, and showed a highly uniform emission image in a phosphor-coated anode plate.
Properties of carbon nanotubes via a thin Ti capping layer on the pretreated catalyst
(2007)
Lai, Rui-Ling
;
Shiu, Jiun-Kai
;
Chang, Yao-Ren
;
Lin, Kao-Chao
;
Chang, Pei-Chi
Screening effect and reliability are two of the most important issues in carbon nanotube-based field-emission devices. A thin Ti capping layer has been deposited on the hydrogen-pretreated catalytic iron nanoparticles to control the density of subsequently grown carbon nanotubes. In this way, the screening effect can be remarkably reduced due to the density of carbon nanotubes down to 10(7) from 10(9) cm(-2) as compared to the control specimens. Thus, the turn-on field can be improved to be 2.1 from 3.8 V/mu m at the emission current density of 10 mu A/cm(2). Furthermore, the electrical breakdown field can be increased to more than 7 V/mu m and the lifetime of carbon nanotubes at high electric field (10 V/mu m) can be greatly prolonged from a few seconds to more than 1 h. This can be attributed to better adhesion and lower contact resistance between the carbon nanotubes and the substrate. (c) 2007 The Electrochemical Society. All rights reserved.