In this study, the growth behavior of carbon nanotubes(CNT) deposited from C2H2 by an atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD) method was investigated. The deposition was performed at 400 degrees C using a modified dielectric barrier discharge using He/C2H2 with additive gases such as N-2 and NH3. The effect of the pretreatment on the surface morphology of the Ni catalyst was also investigated. Treatment of the Ni catalyst surface with a He (6 slm)/NH3 (90 sccm) atmospheric pressure plasma for 5 min at 400 degrees C transformed the Ni surface into more uniformly agglomerated small Ni particles required for the enhanced carbon diffusion during the CNT formation. The CNTs grown by using He (6 slm)/C2H2 (90 sccm) AP-PECVD with additive gases (NH3, N-2) for 5 min at 400 degrees C after the pretreatment showed uniform 1.5-2 mu m long and 20-50 nm diameter multi-layer CNTs. By the application of -1.2 kV of dc bias to the substrate during the growth CNTs by the AP-PECVD, more vertical CNTs could be obtained. FT-Raman data showed the grown CNTs are muti-wall CNTs and have the intensity ratio of D-band/G-band was 0.8-0.9, so defects were involved in the grown CNTs. This study provides a new method growing CNTs at atmospheric pressure and at low temperature, which has special advantages for large scale applications using conventional glass substrates. (c) 2005 Elsevier B.V. All rights reserved.