Low temperature synthesis of carbon nanotubes by microwave plasma-enhanced chemical vapor deposition

We have synthesized pure carbon nanotubes at very low temperature using microwave plasma-enhanced chemical vapor deposition (MPECVD) with methane/hydrogen gas. Ratio of a gas mixture (CH4/H2) and deposition time at a substrate temperature below 520°C are optimized. Pure and dense carbon nanotubes are grown uniformly over a large area of Ni-coated silicon substrates without any pretreatment of substrates. The diameters and lengths of carbon nanotubes could be controlled by changing the ratio of gas mixture and the growth time. Raman spectrum clearly shows the peak at 1592 cm−1 (G-band), indicating the formation of graphitized carbon nanotubes.