First-principles study of the F-terminated Boron Nitride nanoribbons

Using first-principles calculations we study the electromagnetic properties of the F-terminated Boron Nitride nanoribbons (BNNRs) with both zigzag and armchair edges (ZBNNRs and ABNNRs). The results show that, compared with the indirect the H-terminated ZBNNRs, the F-terminated ZBNNRs are direct semiconductors and also the band gaps decrease monotonically with the increasing ribbon width, while the ABNNRs maintain the direct character. The band gap of the F-terminated BNNR is lower than that of the H-terminated one with the same ribbon width because of the mixing effects from the non-bonding 2p electrons of F and N atoms. Both the ZBNNRs and ABNNRs maintain the non-magnetic characters. Compared with the scarce contribution from H atom, the charge density of the highest valence band and the lowest conduction band analyses show that the contribution from F atom cannot be neglected. The N–B, B–F and B–H are ionic bonds with different bonding strength, while the N–F and N–H are all covalent bonds with different charge density accumulation.