Hot filament enhanced CVD synthesis of carbon nanotubes by using a carbon filament

The low temperature synthesis of single-walled carbon nanotubes (CNTs) on a Si substrate has been reported. Single-walled CNTs were grown from a CH2 and H-2 mixture by a hot-filament enhanced CVD method using a carbon filament. The catalyst was silica-supported iron-cobalt prepared by sol-gel method. We observed the influence of the catalyst material, C2H2 concentration, growth pressure and substrate temperature on the formation of the CNTs. By optimizing the catalyst, both single-walled CNTs and multiwalled CNTs could be synthesized, depending on the reaction conditions. The formation of single-walled CNTs occurred when the carbon supply was kept low, i.e. low C2H2 concentration and low reaction pressure. The diameter of tubes decreased with increasing the substrate temperature. By optimizing the growth conditions, a small diameter of 0.65 nm single-walled CNTs, estimated from Raman scattering spectrum, was achieved even the low substrate temperature as 660 degreesC. (C) 2003 Elsevier B.V. All rights reserved.