AVS 52nd International Symposium
    Nanometer-Scale Science and Technology Friday Sessions
       Session NS-FrM

Paper NS-FrM11
Direct Synthesis of Suspended Single-Walled Carbon Nanotubes Crossing Plasma Sharpened Carbon Nanofiber Tips

Friday, November 4, 2005, 11:40 am, Room 210

Session: Nanotube Processing and Properties
Presenter: K.C. Leou, National Tsing Hua University, Taiwan
Authors: C.H. Weng, National Tsing Hua University, Taiwan
K.C. Leou, National Tsing Hua University, Taiwan
W.Y. Lee, National Tsing Hua University, Taiwan
Z.Y. Juang, National Tsing Hua University, Taiwan
C.H. Tsai, National Tsing Hua University, Taiwan
Correspondent: Click to Email
Single-walled carbon nanotubes are one of the most important quasi-one-dimensional nano-materials but their properties or associated device characteristics are very sensitive to the surroundings, e.g., surfactants or wrapping materials, and ambient gases, etc. It has been shown that such environmental perturbation effects could be minimized by suspending the SWNTs. Here we report a novel method for direct synthesis of suspended single-walled carbon nanotubes (su-SWNTs) using vertically-aligned carbon nanofibers (CNFs) as templates via a three-step fabrication process. Plasma enhanced chemical vapor deposition (PECVD) is first employed to grow vertically aligned CNFs on silicon substrates patterned with coated catalytic nickel film of 10 nm thickness. The CNFs are then post-treated by energetic argon plasma in the same reactor to yield structural transformation of CNFs with sharpening tips embedded with catalytic nanoparticles of a favorable size, presumably below 10 nm. A thermal CVD process then subsequently followed to directly synthesize SWNTs suspended across the tips or sidewalls of post-treated CNFs (PT-CNFs) with a span up to 10 µmm, as revealed by the analysis using scanning electron microscopy and resonance micro-Raman spectroscopy. We also demonstrated that one can maximize the yield of su-SWNTs on the tips of PT-CNFs by optimizing the post-treatment conditions to provide a protective coating to suppress the growth of SWNTs from sidewalls. The method of fabricating su-SWNTs described in this letter can be extended to position a single isolated SWNT for the purpose of either minimizing environmental perturbations during SWNT characterization or enhancing performance in nano-device applications.@footnote 1@ @FootnoteText@ @footnote 1@ This work was supported by the National Science Council of the Republic of China and the Center for Nano Science and Technology in the University System of Taiwan.