Electronic States of BCN Alloy Nanotubes in a Simple Tight-Binding Model

Abstract

Electronic states are calculated in boron carbonitride (BCN) alloy nanotubes with a simple tight-binding model. Random replacement of carbon atoms with boron and nitrogen (B–N) ones in metallic carbon nanotubes mainly causes level broadening and the nanotubes remain metallic. On the other hand, the energy gap of boron nitride (BN) nanotubes always survives under random substitution of B–N atoms by carbon ones while it becomes smaller than the original gap. Further, the optical gap does not correspond well with the band gap of the density of states in nanotubes with high B–N concentration. This can be understood in terms of localized states associated with carbon impurities in a BN nanotube.