Configuration and electronic properties of graphene nanoribbons on Si(2 1 1) surface

We perform first-principles calculations based on density functional theory to study the configuration and electronic properties of graphene nanoribbons (GNRs) on Si(2 1 1) surface. Both [0 1 image] and [image 1 1] adsorption orientations of Si(2 1 1) surface are considered. We find that the adsorption energy is determined not only by the edge states of GNRs, but also by the ribbon width and the orientation of the substrate. Bridge and M-shape adsorption configurations appear gradually as the ribbon width increases. The substrate effectively affects the edge states of GNRs and tends to depress the metallic nature of zigzag GNRs (Z-GNRs) and metallize the armchair GNRs (A-GNRs).