Electronic and magnetic properties and structural stability of BeO sheet and nanoribbons

The novel electronic and magnetic properties of BeO nanoribbons (BeO NRs) as well as their stability are investigated through extensive density functional theory calculations. Different from semiconducting graphene nanoribbons and insulating BN ribbons, all zigzag edged BeO NRs are revealed to display ferromagnetic and metallic natures independent of the ribbon width and edge passivation. The polarized electron spins in H-passivated zigzag BeO NRs are from the unpaired electrons around the weakly formed Be-H bonds, while those of bare zigzag BeO NRs are due to the 2p states of edge O atoms. In sharp contrast, all armchair BeO NRs are nonmagnetic insulators regardless of the edge passivation. In particular, all bare armchair BeO NRs have a nearly constant band gap due to a peculiar edge localization effect. Interestingly, the band gaps of all armchair BeO NRs can be markedly reduced by an applied transverse electric field and even completely closed at a critical field. The critical electric field required for gap closing decreases with increasing ribbon width, thus the results have practical importance. Further stability analysis shows that bare BeO NRs are more stable than H-passivated BeO NRs of similar ribbon widths and bare armchair BeO NRs are energetically the most favorable among all the nanoribbons.