Browsing by Author "Lai, HJ"

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Growth behavior and interfacial reaction between carbon nanotubes and Si substrate
(2004-07-01)
Hsu, CM
;
Lai, HJ
;
Kuo, CT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The effect of the interfacial reaction of Co catalyst with a Si substrate on growth of carbon nanotubes (CNTs) was investigated. Well-aligned multiwall CNTs (MWCNTs) were synthesized and applied barrier layers by microwave plasma-enhanced chemical vapor deposition (MPECVD). Growth proceeded in a flowing mixture of H-2, CH4, and N-2 as precursors at a temperature of 600 degreesC and a -200 V substrate bias; Co was sputtered as the catalytic material. Transmission electron microscopy (TEM) and x-ray diffraction were employed to examine the growth behavior of CNTs on Si (100) substrates on which Co had been deposited by MPECVD. The TEM results indicate that discrete conical CoSi2 layers with {111} and (100) faceted interfaces were formed on a Si (100) substrate during CNTs growth. Direct evidence that the growth is by tip growth and base growth is presented. The results show that well-aligned CNTs exhibit a significant emission current. The field emission characteristics of CNTs are contributed to the relationship between the application of different barrier layers and the growth mode of CNTs. (C) 2004 American Vacuum Society.
Root growth of multi-wall carbon nanotubes by MPCVD
(2005-01-03)
Hsu, CM
;
Lin, CH
;
Lai, HJ
;
Kuo, CT
;
材料科學與工程學系
This work examines the relationships among the growth and interlayer reactions of carbon nanotubes (CNTs) to develop an effective process for controlling the nanostructure, orientation and characteristics of CNTs. Vertically oriented CNTs were successfully synthesized by microwave plasma chemical vapor deposition (MPCVD) with CH4/H-2 as source gases. Additionally, the Ti and SiO2 barrier layers and the Co catalyst were used in an experiment on the growth of CNTs on the Si wafer. Then, the SiO2 barrier layer was deposited by low-pressure chemical vapor deposition (LPCVD). The Ti barrier layer and Co catalyst films were deposited on the Si wafer by physical vapor deposition (PVD). The deposited nanostructures were characterized by scanning and transmission electron microscopy, the results of which reveal that the deposited MWCNTs were grown under the influence of a catalyst on Si substrates with or without a barrier layer, by MPCVD. Vertically gown, dense MWCNTs attached to a catalytic film demonstrate that various MWCNTs penetrated the root particles. The diameter of the root particles, of approximately in the order of 100 nm, is larger than those of the tube, 10-15 nm. The well-known model of the growth of CNTs includes base- and tip-root growth. The interaction between the catalytic film and the supporting barrier layer is suggested to determine whether the catalytic particles are driven up or pinned down on the substrate during the growth. (C) 2004 Elsevier B.V. All rights reserved.