Configuration-dependent geometric and electronic properties of bilayer graphene nanoribbons

Configuration-dependent geometric and electronic structures of bilayer zigzag graphene nanoribbons are investigated by first-principles calculations. These properties are dominated by the stacking configurations, interlayer edge-edge interactions, spin arrangements, and ribbon widths. The optimal configuration exists between the AA and ^ABα ( ^AA′ and ^ABβ) stackings, mainly owing to the competition of the stacking and quantum confinement effects. The interlayer edge-edge interactions lead to the destruction or creation of magnetism and cause the AA-stacked system to exhibit a pair of metallic linear bands. However, other stacked nanoribbons are exclusively indirect- or direct-gap semiconductors. The splitting of spin-up and spin-down states could be induced by different magnetic environments. The band-edge states, with a high density of states, are sensitive to changes in the relative displacement.