CURVATURE-INDUCED BONDING CHANGES IN CARBON NANOTUBES INVESTIGATED BYELECTRON-ENERGY-LOSS SPECTROMETRY

Effect of curvature-induced strain on the covalent bonding in isolated and selected single-shell and multi-shell carbon nanotubes is explore d, using electron energy-loss spectroscopy (EELS) on the core K level, which probes the distribution of available unoccupied states in the c onduction band. Results show that the curvature and mostly the layer s tacking affect the sigma conduction states. On the contratry, no infl uence is detected concerning the pi band, even with corrugation angle s up to 7 degrees in a 1-nm-wide single-walled tube. First-principle l ocal-density calculations are used to relate the features in the EELS spectra to the different atomic interactions in nanotubes. Finally, th e covalent character of the bonding in existing nanotubes is discussed .