Growth and characterization of sidewall graphene nanoribbons

We study the growth of epitaxial graphene nanoribbons on silicon carbide mesa sidewalls by means of scanning probe techniques, local transport, and Raman spectroscopy. The sidewall nanoribbons are demonstrated to consist of charge neutral monolayer graphene with a zig-zag type orientation. Two types of roughness, the step density of the substrate and the roughness of the sidewalls, were identified as being detrimental to the transport properties of these ribbons. By means of 4-point probe experiments, single channel ballistic transport was observed with a mean free path limited by the width of the underlying substrate terraces. Moreover, a transition from ballistic to one-dimensional diffusive transport can be obviously triggered by an increased roughness of the sidewall, e.g., by an enlarged depth of the mesa.