Electric field effect on electronic structure of BN nanotubes: a first principles study

The electronic structure of BN nanotube under electric field was studied using first principles calculations based on density functional theory (DFT). The relaxed structures in the presence of an electric field show that the interlayer distance along tube axis varies irregularly. The energy band structure is shifted towards the lower energy level, and the band gap is decreased significantly for both armchair and zigzag nanotubes by applied electric field. Furthermore, for armchair nanotube, the band gap transition from indirect-to-direct is observed. It can be found that there is obvious difference in partial density of states (PDOS) between half left and half right sides of nanotube. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) indicate that the positive and negative charges are spatial separated along the nanotube axis with the effect of electric field, and thus this can be considered as a pure material PN junction without doping. (authors)