Transport properties of graphene/metal planar junction

•Metal electrode induces a transmission minimum (TM2) in the graphene/metal planar junction.•The TM2 locates below the Fermi level independence of doping type of graphene.•The electrostatic potential of metal electrode influences the position of TM2.•Work function difference between clamped and suspended graphene affects the position of TM2.•The I–V curves show asymmetric due to the electrostatic potential step around the junction.

The transport properties of graphene/metal (Cu(111), Al(111), Ag(111), and Au(111)) planar junction are investigated using the first-principles nonequilibrium Green's function method. The planar junction induce second transmission minimum (TM2) below the Fermi level due to the existence of the Dirac point of clamped graphene. Interestingly, no matter the graphene is p- or n-type doped by the metal substrate, the TM2 always locates below the Fermi level. We find that the position of the TM2 is not only determined by the doping effect of metal lead on the graphene, but also influenced by the electrostatic potential of the metal substrate and the work function difference between the clamped and suspended graphene.