GROWTH OF CARBON NANOTUBES

The production, morphologies and atomic structures of carbon nanotubes are reviewed, and a mechanism for tube growth is discussed on the basis of transmission electron microscopy observations. Capping of carbon nanotubes is explained nicely in terms of pentagons; distributions of pentagons in a hexagon network cause various cap morphologies. Heptagons, resulting in negative curvature into a graphitic plane, also provide a variety of graphitic structures. Pentagons and heptagons seem to play a key role in tube growth. On the basis of the consistency of various tube morphologies, we propose a model for tubule growth, in which the tubules are open at their ends while growing in the carbon arc plasma. To support this open-end growth mechanism, other evidence such as layer-by-layer growth on the tube surfaces and ''over-shooting growth'' on tube tips is given.