High-aspect ratio and horizontally oriented carbon nanotubes synthesized by RF-cCVD

Horizontally aligned long carbon nanotubes were efficiently synthesized on Si substrates by using a radio-frequency catalytic chemical vapor deposition method. The morphological as well as the growth properties of these nanotubes were systematically investigated with various analytical techniques including microscopy and Raman spectroscopy. Different reaction parameters such as temperature, type of hydrocarbon gas and catalyst amount were varied and their effects on the nanotube size, quality and alignment are reported. High-aspect ratio and horizontally oriented nanotubes were found to grow following the “tip growth” mechanism. The fast and localized heating rate produced by the RF generator helps nanotubes to separate and lift the nano-particles away from the support and hence contributes to the growth of CNTs with a very high-aspect ratio. Carbon nanotubes synthesized with methane show a better horizontal alignment compared to those synthesized with acetylene, which might be due to the flow rate of the hydrocarbon gas.