Low temperature synthesis of single-walled carbon nanotubes in an inductively coupled plasma chemical vapor deposition system.

In this work, we present a parametric study on the low temperature synthesis of single-walled carbon nanotubes (SWNTs) in an inductively coupled plasma (ICP) CVD system using dry bi-layered catalytic thin-films (Fe/Al and Ni/Al, deposited by electron-beam evaporation method) as the catalysts. With a low substrate temperature of 550 degrees C and above, SWNTs were successfully synthesized on both catalysts, as revealed from the characteristic peaks of SWNTs in the micro-Raman spectra. By the reduction of plasma power and the shortening of the process times, the lowest synthesis temperature of SWNTs achieved in our system was approached to 500 degrees C on Ni/Al catalysts; on the other hands, the lowest temperature for Fe/Al catalysts was 550 degrees C. Our results suggest that as compared with Fe/Al, Ni/Al is more favorable for plasma-enhanced CVD (PECVD) synthesis of SWNTs at low temperatures. This work can be used for further improvements and better understanding on the production processes of SWNTs by PECVD methods.

Direct synthesis of single-walled carbon nanotubes selectively suspended on tips of vertically aligned silicon nanostructures fabricated by hydrogen plasma etching.

Here we present a method to synthesize single-walled carbon nanotubes (SWNTs) selectively suspended on tips of silicon-based nanostructure (Si-ns) templates. The Si-ns templates vertically aligned to the substrates are fabricated via an anisotropic etch process using reactive hydrogen plasmas, in which the etch-resistive nanomasks are the nanosized particles formed by thermal annealing of multi-layered catalytic thin films. After plasma etching, the nanosized self-masks remaining at the tips of the Si-ns directly serve as the catalysts for SWNT growth by thermal chemical vapour deposition. Consequently, the synthesized SWNTs are selectively suspended on the tips of the Si-ns, as revealed by characterizations using scanning electron microscopy and resonance Raman spectroscopy. This methodology provides a simple and straightforward approach to assemble two different nanomaterials, i.e., Si-ns and suspended SWNTs, together as a building block for constructing nanodevices for possible applications.