Local conductance measurements of double-layer graphene on SiC substrate.

The microscopic structural and electrical properties of few-layer graphene grown on an SiC substrate were characterized by low-energy electron microscopy, transmission electron microscopy and scanning probe microscopy measurements of local conductance. The double-layer graphene sheet was confirmed to be continuous across the atomic steps on the buried SiC substrate surface, and the measured local conductance was clearly modified in the vicinity of the steps. The conductance decreased (slightly increased) at the lower (upper) side of the steps, suggesting deformation-induced strain is the origin of the conductance modification. From the contact force dependence of the conductance images, the effective contact areas for both nanogap-probe and point-probe measurements were estimated.