Bandstructure modulation for carbon nanotubes in a uniform electric field

A method to electronically modulate the energy gap and bandstructure of semiconducting carbon nanotubes is proposed. We investigate this bandstructure modulation mechanism using tight-binding and density functional theory (DFT). Results show that the energy gap of a semiconducting nanotube can be narrowed, when the tube is placed in an electric field perpendicular to the tube axis. In contrast, Metallic tubes were found to exhibit a screening behavior, whereby free charge redistributes about the tube circumference as a result of the external field. In this case, the bandstructure shows little perturbation in response to an applied electric field. (C) 2002 American Institute of Physics.