Band gap modification of single-walled carbon nanotube and boron nitride nanotube undera transverse electric field

Abstract

The electronic structures of carbon (C) and boron nitride (BN) nanotubes under atransverse electric field were investigated through the first-principles pseudopotentialdensity-functional theory (DFT) calculations. It was found that band gap modificationsoccur both in the semiconducting C and BN nanotubes under an external electric field byinducing a semiconductor–metal transition. The variations of the band gap sizes withtransverse electric fields are very different between C and BN nanotubes. In thesemiconducting C nanotube, a sharp semiconductor–metal transition does not occur until athreshold electric field is achieved; the BN nanotube, on the other hand, shows a gradualreduction of the band gap size once an external electric field is applied due to the largerionicity of BN bonds. In addition, the semiconductor–metal transition in both C and BNnanotubes occurs at a lower value of electric field with increasing diameter. The ability totune the band gap in both C and BN nanotubes by an external electric field providesthe possibility for future electronic and electro-optic nanodevice applications.