Stepped carbon nanotubes synthesized in anodic aluminum oxide templates

Anodic aluminum oxide templates with stepped nano channels were fabricated by repeated anodization and pore widening processes, and carbon nanotubes were grown on the templates without catalytic metals by pyrolysis of acetylene. High-resolution transmission electron microscopy revealed that the wall of the CNTs has a multi-wall structure made of stacked graphite flakes of several nut sizes. For the carbon nanotube formation on alumina, we propose a pyrolytic CVD of carbon on alumina surface instead of a synthesis via catalytic action of the alumina. The electrical properties of the stepped and linear CNTs did not show remarkable difference because of the highly defective structure of the flaked tubes. (C) 2003 Elsevier B.V. All rights reserved.