DC plasma-enhanced chemical vapour deposition (PECVD) was used to grow films of aligned carbon nanotubes on a silicon wafer using Fe as catalyst and a C2H2/H-2 gas mixture. The films were of high quality and showed an exceptionally high growth rate compared with other plasma growth techniques. For long growth times, the upper parts of the nanotubes developed additional outer graphite flakes. The onset of the 'tube decoration' correlates with a decrease in linear growth rate and can be related to the gradient of plasma parameters in the cathode sheath. (C) 2003 Published by Elsevier B.V.