Direct Evidence of Atomic Structure Conservation Along Ultra-Long Carbon Nanotubes

The atomic structure of ultralong carbon nanotubes obtained by catalytic chemical vapor deposition in the kite growth mode has been studied along the nanotube length via electron diffraction and high-resolution transmission electron microscopy. Contrary to other techniques, electron diffraction studies provide a direct determination of the chiral structure of nanotubes. These studies demonstrate that the chirality of the nanotubes remained constant all along their length (i.e., up to several hundreds of micrometers). A tendency of kite-growth nanotubes to be double-walled has been observed as well as a preferential distribution toward high-chiral angles configuration. Furthermore, the studies yield a metallic:semiconducting ratio close to the one expected from a natural distribution of nanotubes (1:2).