Contact resistivity and current flow path at metal/graphene contact

The contact properties between metal and graphene were examined. The electrical measurement on a multiprobe device with different contact areas revealed that the current flow preferentially entered graphene at the edge of the contact metal. The analysis using the cross-bridge Kelvin (CBK) structure suggested that a transition from the edge conduction to area conduction occurred for a contact length shorter than the transfer length of ∼1 μm. The contact resistivity for Ni was measured as ∼5×10−6 Ω cm2 using the CBK. A simple calculation suggests that a contact resistivity less than 10−9 Ω cm2 is required for miniaturized graphene field effect transistors.