Vertically aligned carbon nanotubes were selectively grown at temperatures as low as 120 8C by plasma enhanced chemical vapour deposition.W e investigated the effects of acetylene, ethylene and methane as carbon source gases together with ammonia as an etchant and nickel as catalyst material.The diluted acetylene plasma gave the highest nanotube growth rate and showed the most intense C2 Swan bands in optical emission.The activation energy for the growth rate was found to be 0.23 eV, much less than for thermal chemical vapour deposition (1.21.5 eV).This suggests growth occurs by surface diffusion of carbon on nickel. The result allows more cost-effective nanotube production, direct growth of nanotubes onto low-temperature substrates like plastics, and could facilitate carbon nanotube integration into sensitive nanoelectronic devices. 2003 Elsevier B.V. All rights reserved. PECVD