CONTROLLED PRODUCTION OF ALIGNED-NANOTUBE BUNDLES

Carbon nanotubes(1,2) might be usefully employed in nanometre-scale en gineering and electronics. Electrical conductivity measurements on the bulk material(3,4) on individual multi-walled(5,6) and single-walled( 7) nanotubes and on bundles of single-walled nanotubes(8,9) have revea led that they may behave as metallic, insulating or semiconducting nan owires, depending on the method of production-which controls the degre e of graphitization, the helicity and the diameter. Measurements of Yo ung's modulus show(10) that single nanotubes are stiffer than commerci al carbon fibres. Methods commonly used to generate nanotubes-carbon-a rc discharge techniques(1,2,4), catalytic pyrolysis of hydrocarbons(11 ,12) and condensed-phase electrolysis(13,14)-generally suffer from the drawbacks that polyhedral particles are also formed and that the dime nsions of the nanotubes are highly variable. Here we describe a method for generating aligned carbon nanotubes by pyrolysis of 2-amino-4,6-d ichloro-s-triazine over thin films of a cobalt catalyst patterned on a silica substrate by laser etching. The use of a patterned catalyst ap parently encourages the formation of aligned nanotubes. The method off ers control over length (up to about 50 mu m) and fairly uniform diame ters (30-50 nm), as well as producing nanotubes in high yield, unconta minated by polyhedral particles.