Physical and electronic structure in carbon nanotubes

Electron nanodiffraction patterns and high-resolution images from bundles o f single-walled carbon nanotubes (SWNTs) have been obtained to determine th e helicity and the packing of tubes. It is found that there is no predomina ting helicity, only a weak tendency of being of 'armchair' structure; the i nter-tube spacing is close to 0.34 nm and several packing orientations may coexist in a single bundle. Electron energy loss spectra from the bundles o f SWNTs and multi-walled carbon nanotubes are used to study electronic stru cture. The pi-bonding is proposed as inter-tube bonding in the bundles. The plasmon energy E-p depends on the diameter and inter-tube (or inter-walled ) spacing. (C) 1998 Elsevier Science B.V. All rights reserved.