Electronic and Transport Properties of Boron-Doped Graphene Nanoribbons

We report a spin polarized density functional theory study of the electronic and transport properties of graphene nanoribbons doped with boron atoms. We considered hydrogen terminated graphene (nano)ribbons with width up to 3.2 nm. The substitutional boron atoms at the nanoribbon edges (sites of lower energy) suppress the metallic bands near the Fermi level, giving rise to a semiconducting system. These substitutional boron atoms act as scattering centers for the electronic transport along the nanoribbons. We find that the electronic scattering process is spin-anisotropic; namely, the spin-down (up) transmittance channels are weakly (strongly) reduced by the presence of boron atoms. Such anisotropic character can be controlled by the width of the nanoribbon; thus, the spin-up and spin-down transmittance can be tuned along the boron-doped nanoribbons.

Figure 1

Structural model of (3,0) GNR. (a) Ferro-$F$, and (b) Ferro-$A$ spin configurations.

Figure 2

Electronic band structures for up (solid lines) and down (dot lines) spins of hydrogenated (3,0) GNR. (a) Ferro-$F$, and (b) Ferro-$A$ configurations.

Figure 3

(a) Structural model of (3,0) GNR indicating the boron substitutional sites. Electronic band structures for up (solid lines) and down (dot lines) spins of hydrogenated (3,0) GNR doped with: (b) one boron at $B1$ site (c) two boron atoms at $B1/B2$ sites.

Figure 4

(a) Boron-doped (3,0) GNR, including the left and right (Ferro-$F$) leads. Spin dependent transmission probability, within $\pm 0.2\mathrm{eV}$ with respect to the Fermi level for: (b) (3,0) GNR with $B1$ (blue, dashed lines) and $B1/B2$ (red, solid lines) models, and (c) $B1/B2$ model for (5,0) GNR.

Figure 5

Transport anisotropy ($\xi$) calculated at Fermi energy for boron-doped nanoribbons at the structural model $B1/B2$ in function of different widths.