This Letter outlines a model to account for the catalyzed growth of nanotub
es by chemical vapor deposition. It proposes that their formation and growt
h is an extension of other known processes in which graphitic structures fo
rm over metal surfaces at moderate temperatures through the decomposition o
f organic precursors. Importantly, the model also states that the form of c
arbon produced depends on the physical dimensions of the catalyzed reaction
s. Experimental data are presented that correlate nanotube diameters to the
size of the catalyst particles. Nanotube stability as a function of nanotu
be type, length and diameter are also investigated through theoretical calc
ulations. (C) 1999 Elsevier Science B.V. All rights reserved.