Unraveling the origin of local variations in the step resistance of epitaxial graphene on SiC: a quantitative scanning tunneling potentiometry study

Abstract

By combining highly resolved Scanning Tunneling Potentiometry with the exceptional sample homogeneity of graphene on SiC epitaxially grown by polymer-assisted sublimation growth, we reveal local variations in the resistance associated with substrate steps. We quantify these variations and show that they are an intrinsic property of graphene on SiC. Furthermore, we trace back their origin to variations in the electronic structure of the interface and, thereby, demonstrate the crucial impact of intrinsic proximity effects in graphene on SiC. Moreover, we find a correlation of the step resistance with the local conductivity and show that at room temperature, the step resistance decreases with increasing local conductivity, whereas at low temperatures, it increases with increasing local conductivity. We attribute this inversion to an interplay between the reduction in electron-phonon scattering and potential scattering with decreasing temperature, and the efficiency of the built-up of an almost completely charge carrier depleted zone at the position of the substrate step.