Physical and electronic structure in carbon nanotubes

Electron nanodiffraction patterns and high-resolution images from bundles of single-walled carbon nanotubes (SWNTs) have been obtained to determine the helicity and the packing of tubes. It is found that there is no predominating helicity, only a weak tendency of being of `armchairʹ structure; the inter-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 of SWNTs and multi-walled carbon nanotubes are used to study electronic structure. The π-bonding is proposed as inter-tube bonding in the bundles. The plasmon energy Ep depends on the diameter and inter-tube (or inter-walled) spacing.