▎ 摘　　要

Electronic structures of zigzag edged graphene nanoribbons (ZGNRs) doped with boron (B) or nitrogen (N) atoms are investigated by spin polarized first-principle calculations. We find the a ZGNRs can be tuned to be either semiconducting, half-metallic by controlling the distance of the impurity atoms to the edges. A new scheme is identified to achieve full half-metallicity in ZGNRs by doping B atom at one edge and N atom at the other. We find that the origin of the half-metallicity is due to interaction between the edge states and B/N atoms which results in direct control over the electron occupation of the edge states. This mechanism is so robust that full half-metallicity can always be produced in ZGNRs irrespective of the ribbon width, which opens new possibilities for applications of ZGNRs in spintronic devices.