Selective Chemical Vapor Growth of Carbon Nanotubes for Application of Electronic-Measuring Nano-Probes
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Selective Chemical Vapor Growth of Carbon Nanotubes for Application of Electronic-Measuring Nano-Probes Hiroki Okuyama, Nobuyuki Iwata and Hiroshi Yamamoto College of Science and Technology, Nihon University, Chiba, Japan ABSTRACT Selectively grown carbon nanotubes (CNTs) and/or vertically aligned CNTs (VACNTs) on patterned metal electrodes have been prepared for applications to a novel electronic-measuring nano-probe. We propose newly a position-controlling method of CNTs by controlling not only a position of catalysts but also the thickness of metal underlayers for the catalysts.
The
selective growth of CNTs was achieved at edges of the metal pattern by thermal chemical vapor deposition. The width of selectively grown CNTs was minimized, about 2.6 µm. The width was about 80 times as small as that of the metal pattern. VACNTs were synthesized by a plasma enhanced CVD method in which the high electric field in a cathode dark space was applied to the substrates. The VACNTs grew up, however, all over the metal pattern.
INTRODUCTION Carbon nanotubes (CNTs) have attracted much attention because of many featured characteristics. High electric conductivity [1] and high permissible current density [2] are suitable for electronic devices.
CNTs grow selectively from catalyst particles by using
chemical vapor deposition (CVD) [3].
CNTs have a high aspect ratio and their growth direction
is controllable by applying electric field during CVD growth [4]. These characteristics are available to fabricate various kinds of nanostructures. CNTs reveal high mechanical strength in spite of high flexibility [5].
Therefore we are aiming at realizing a novel nano-probe with CNTs
which enables to approach it toward contact points on specimen easily without an accurate control for measuring of electric transport properties. The control for position and direction of CNTs is necessary in order to prepare the nanoscaled CNTs electronic devices. Furthermore electrically and mechanically firm contacts between CNTs and metal electrodes are needed. In this work, we tried to prepare selectively grown CNTs and vertically aligned CNTs (VACNTs) on patterned metal electrodes for realization of the novel electronic measuring nano-probe. The selectively grown CNTs are prepared by using the two characteristics as follows. One is that the CNTs grow selectively from fine particle catalysts. The other is that
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we can control the synthesis of the fine particle catalysts by noticing wettability between metal interfaces. Since wettability of metal interface is high, it is hard to form fine particles as overlayers on smooth underlayers. When the surfaces of underlayers are rough, overlayered metals form fine particles.
Therefore we propose newly a position-controlling method of CNTs
by controlling not only a position of catalysts but also a surface morphology of metal underlayers.
EXPERIMENTAL In the first place Ni catalysts and Mo underlayers were deposited on quartz substrates through a metal mask (t
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