Anisotropic electrical conduction of vertically-aligned single-walled carbon nanotube films |
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Authors: | Cheng-Te Lin Chi-Young Lee Tsung-Shune Chin Rong Xiang Kei Ishikawa Junichiro Shiomi Shigeo Maruyama |
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Affiliation: | aDepartment of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan;bCenter of Nanotechnology, Materials Science, and Microsystems, National Tsing Hua University, Hsinchu 30013, Taiwan;cDepartment of Materials Science and Engineering, Feng-Chia University, Taichung 40724, Taiwan;dHKUST-SYSU Joint Laboratory of Nano Materials and Technology, State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China;eDepartment of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan |
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Abstract: | Anisotropic electrical conduction measurements have been carried out for thin films of vertically-aligned single-walled carbon nanotubes (VA-SWCNTs) grown by an alcohol catalytic CVD process. Combined with controlled synthesis and structure characterization by optical spectroscopy, the influence of the aligned structure on the electrical conduction has been identified. The out-of-plane conductivity of the films was measured to be about 0.56 S/mm, independently of the film thickness. On the other hand, the in-plane conductivity was found to be more than an order of magnitude smaller, which gives rise to highly anisotropic electrical conduction, reflecting the high degree of alignment in the VA-SWCNT films. The in-plane conductivity decreases with increasing film thickness, in contrast to the film of random SWCNT networks, which exhibit thickness-independent in-plane resistance. The thickness-dependent in-plane conductivity can be expounded by a growth model of vertically aligned SWCNT films in which a thin layer of nanotube networks form on top of films at the initial stage of the growth. Such electrical anisotropy of VA-SWCNT films can be useful in miniaturized sensing devices. |
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