First principles calculation of effect of graphene coating on transmission coefficient of Cu thin film with low surface roughness

Abstract

In this paper, we calculate the effect of a graphene coating on the transmission coefficient of a Cu thin film with surface disorder. The nonequilibrium coherent potential approximation combined with the linear muffin-tin orbital formulation, which is based on first principles, is applied by assuming that there is surface disorder. The graphene coating mitigates the effect of Cu surface scattering on the transmission coefficient. The weak interaction between Cu and graphene and the upward shift of the Fermi level with respect to the Dirac point improve the transport characteristics by offering more conduction bands. Moreover, graphene-coated Cu with a perfect surface has a completely specular transmission coefficient. The surface disorder decreases the transmission coefficient due to the nonconserved transverse momentum (k) of the scattering wave through the central area of the two-probe system. However, for a graphene coating on a Cu thin film with surface disorder x<3.90%, length l<5.09nm, width 0.25 nm, and thickness 1.23 nm, the transmission coefficient is higher. The increased transmission coefficient due to graphene coating can overcome the diffusive scattering originating from the surface disorder. The coherent potential approximation band structure shows that graphene bands are less affected by Cu surface disorder than Cu bands, which enhances the total conduction by offering additional channels for electrons. Our results demonstrate that graphene is a potential liner material for a Cu thin film with low surface disorder.