Realizing robust half-metallic transport with chemically modified graphene nanoribbons

Although many chemical modification schemes for achieving half-metallicity in zigzag-edged graphene nanoribbons (ZGNRs) have been proposed, practically, half-metallic transport is hardly observable with them due to the resulting negligible energy difference of the anti-ferromagnetic (AF) and ferromagnetic (F) configurations between the two edges. We propose a scheme to achieve robust half-metallic transport by such ZGNRs in which central carbon atoms are substituted by BN pairs. We build transport junctions by connecting the top edge of one ribbon with the bottom edge of another through a carbon tetragon or a carbon hexagon. For both connection styles, we consider two different relative orientations of the BN pairs in the two ribbons, namely, a BN-BN case with the BN pairs in the same direction and a BN-NB case with the BN pairs in the opposite directions. It is found that, for both connection styles, we can always get a BN configuration where the junction is always in a perfect half-metallic state, independent of the magnetic configurations. It is understood by the matching or mismatching of the spin polarity and spatial separation of the edge states of the two ribbons. This should be taken into consideration in the design of spintronic devices with graphene nanoribbons. (C) 2018 Elsevier Ltd. All rights reserved.