The Effect of an External Electric Field on the Electronic Properties of Defective CBN Nanotubes: A Density Functional Theory Approach

We investigated the effects of applying an external electric field on the electronic properties of Stone-Wales (SW) defective carbon-boron-nitride nanotubes (CBN) using first principles calculations. The defective CBN nanotubes were modeled by introducing Stone–Wales defects in the boron-nitride segment (BN-SW), the carbon segment (C-SW), and the carbon-boron-nitride interface segment (CBN-SW). Initially, we studied the formation energies and the structural stability for all models. As a result of adding the SW defects, the calculated bandgap values of the C-SW and CBN-SW models showed significant changes compared to the pristine CBN nanotube. Meanwhile, the BN-SW model showed a slight bandgap change because of the strong covalent bonding between the boron and nitrogen atoms. Applying a transverse electric field induced a fast bandgap closing response in all models, indicating a rapid semiconductor-to-metal phase transition. The defective C-SW and CBN-SW models demonstrated unique bandgap closing patterns in response to applied transverse and longitudinal electric fields, while pristine and BN-SW models had similar bandgap responses.