The growth mode change in carbon nanotube synthesis in plasma-enhanced chemical vapor deposition

We carried out experiments to investigate the origin of the growth modes in CVD synthesis of multi-wall carbon nanotubes. The results obtained show that the mode of CNT growth depends on the adhesion of the catalyst particle to the substrates. While many growths of CNTs via thermal CVD revealed base growth modes, the thermal synthesis of the CNTs on anodic aluminum oxide showed a tip growth mode indicating that the growth method itself does not determine the growth mode. In the syntheses via plasma-enhanced CVD with varying the plasma power, a change between the base- and tip-growth modes could be observed. In the growth process driven thermally, CNTs grew on partially interconnected particles, involving large adhesion force between the grouped particles and substrate, and, therefore the CNTs synthesis in a tip growth mode was difficult. However, in plasma the bombardment effectively isolated nanoparticles and promoted the tip growth mode. (C) 2004 Elsevier B.V. All rights reserved.