Effective Growth of Vertically Aligned Single Wall and Double …

Effective Growth of Vertically Aligned Single Wall and Double
        Wall Carbon Nanotubes at Low Temperatures


                            Vijaya Kumar Kayastha
                          Research Advisor: Dr. Yoke Khin Yap
                  Michigan Technological University, Houghton, MI-49931


Abstract:
Effective growth of single wall and double wall carbon nanotubes (SWNTs and
DWNTs) with high purity is the key step for the realization of Carbon Nanotube
(CNT) based nano-electronic and sensing devices. In addition, their growth at low
temperatures is of great importance due to compatibility issue with current Integrated
Circuit Technology. However, their growths are much more difficult than that of
multiwall carbon nanotubes (MWNTs) due to the requirements of smaller catalyst
particles (~1-2 nm) and much higher strain energy of formation. The vertically aligned
gro w th mod e is an indication of high- yield and optimiz ed gro wth. There are only a
few groups in the world that have achieved this growth mode for DWNTs and
SWNTs. Most of them have used high-temperatures, ethanol, water vapor or oxygen
for achieving this effective growth mode, which will potentially oxidize and damage
the nanotubes. There is almost no report of use of acetylene for these optimized
growths which would enable us to grow them at relatively low temperatures. Here, we
report the thermal chemical vapor deposition growth of vertically-aligned SWNTs and
DWNTs at temperatures, as low as 700oC, by using acetylene gas. The growth rate is
16µm/min which is higher than in most reported works. We have explained the
results by our previously reported growth model which involved dissociative
adsorption of acetylene and Vapor-Solid-Liquid mechanism. Controlled supply of
acetylene and the optimum catalyst films are prerequisites for these high yields, low
temperature growths of SWNTs and DWNTs.