Abstract Submitted to the    NANOTUBE'04 Conference:

The nucleation of SWNTs is enhanced by early transition metals or rare earth catalysts. The similarities between the samples synthesized from different techniques, observed in transmission electron microscopy, suggest a common growth mechanism. The proposed scenario is the following : first a condensation step ; carbon atoms condense at high temperature in a low density amorphous state followed by the formation of metallic catalyst particles which dissolve significant amounts of carbon. Then a nucleation and growth process at 1500-2000K : the solubility of carbon decreases; carbon segregates to the surface and the growth proceeds via a root mechanism.

To go beyond this phenomenological approach, Tight - Binding (TB) Monte Carlo simulations are performed in order to simulate the nucleation of C-SWNTS on a metallic (Ni) substrate. A minimal set of parameters is used to obtain a transferable TB parametrization of the C-C, Ni-Ni and Ni-C interactions applicable to binary systems. We have investigated in detail the carbon segregation process and the adhesive properties of C on the Ni surface.