Tight-Binding Band Structures of Nanographite Multiribbons

Electronic properties of AB-stacked nanographite ribbons depend on the edge structure, the ribbon width ( N y ), and the ribbon number ( N z ). All zigzag ribbons are metals, while armchair ribbons are metals only for N y =3 I +2 ( I an integer). The dependence of energy gap on the ribbon number is weak for the semiconducting armchair multiribbons with N z >5. The semiconductor-metal transition is absent in the increasing of N z . Density of states exhibits many special structures. The interlayer interactions would affect the energy dispersions of band structures. They could induce the hybridization of energy bands, the new partial flat bands along the k x - or k z -direction, the asymmetry of the electronic structure about the Fermi level, the change from the direct energy gap into the indirect energy gap, the destruction of the state degeneracy, and the alternation of the special structures in the density of states.