Electronic and Magnetic Properties of Hybrid Boron Nitride Nanoribbons and Sheets with 5–7 Line Defects

The first-principles calculations have been used to investigate the electronic and magnetic properties of hybrid boron nitride nanoribbons (BNNR) and sheets, which are constructed by the B-rich or N-rich grain boundaries (GB) with the pentagon–heptagon (5–7) line defect joining together the normal zigzag and armchair BN segments. Our results show that, in contrast to the pristine BN systems, the hybrid BN nanostructures with 5–7 line defects possess some unique electronic and magnetic properties. The hybrid BNNR with H-passivated edge and BN sheet are semiconductors with notably reduced band gap due to the presence of line defect state, as compared to the normal BN systems. The band gaps of H-passivated hybrid BNNR with B-rich and N-rich GB exhibit the different variation with the ribbons width. The hybrid BNNR created by B-rich GB with bare N edge for all widths are half-semiconductors with the ferromagnetic ground state, whereas for the hybrid BNNR with bare zigzag B edge the antiferromagnetic → nonmagnetic semiconductor transition occurred when its narrow zigzag segment is changed to the wider one. Interestingly, totally different from the perfect zigzag BNNR, the hybrid BNNR with two-H-terminated B edge exhibit the metallic → half-semiconducting → half-metallic behavior transitions as its number of zigzag BN chains gradually increases due to the compressed zigzag edge. Therefore, the hybrid BN nanostructures constructed by GB with 5–7 line defects may provide potential applications for BN-based nanoelectronic and spintronic devices.