Because of the symmetry and unique electron structure of the lattice of carbon molecules that nanotubes are constructed from, the actual structure of a carbon nanotube strongly affects it's electrical properties. For a given (n,m) configuration:
If n = m (armchair) The nanotube is metallic.
If n – m is a multiple of 3 The nanotube is semi-conducting with a very small band gap (energy required to excite charge carriers)
Otherwise The nanotube is a moderate semiconductor.
In theory, a metallic nanotube can carry extremely dense electrical current, around 4 × 109 A/cm2. That's more than 1000 times greater than known excellent conductors like copper.
Because of a property known as “Ballistic Conduction,” where a lack of scattering affects results in unimpeded electron flow in a quasi-one dimensional apparatus, all nanotubes are expected to be good thermal conductors along the tube itself. Theoretically, they can transmit up to 6000 Watts per Meter Kelvin at room temperature. Copper, a well known thermal conductor, transmits 385 Watts per Meter Kelvin.