Raman spectroscopy of pristine and doped single wall carbon nanotubes

Pulsed laser vaporization (PLV) of a heated, Fe/Ni or Co/Ni catalyzed carbon target in Argon gas has been used to synthesize single-wall carbon nanotubes (SWNTs). The Raman spectrum of SWNTs is very different from that observed for graphite (the nanotube's Bat parent) and these differences can be understood as a result of the cyclic boundary condition imposed on a graphene sheet rolled up to form a seamless nanotube. Optical resonances are observed which are associated with the one-dimensional character of the electronic states of these novel quantum wires. The high frequency tangential mode frequency is significantly upshifted (downshifted) when the SWNT bundles are exposed to acceptor (donor) dopants. (C) 1998 Elsevier Science S.A. All rights reserved.