▎ 摘　　要

We report a first-principles study of electron transport through armchair graphene nanoribbon adsorbed on Ni(111) and Cu(111) surfaces. The contact with Ni electrodes induces a broad transmission spectrum, mixed transmission profiles in the Brillouin zone, and an opening of multichannel for transmission near the Fermi energy. In contrast, we observe narrow transmission peaks in the Cu-graphene contact, which can be clearly identified as the contribution from graphene molecular orbitals (MOs), and only a single transmission channel exists. These features arise, respectively, from the strong hybridization between graphene and Ni d states and from the weak interaction between graphene and Cu s states. In addition, only a part of the MOs contribute to the transmission of Cu-graphene, depending on the MOs symmetry. As a result of these effects, we find that the contact resistance of the Ni-graphene system is one order of magnitude lower than that of Cu-graphene.