Scanning Tunneling Spectroscopy (STS) studies of graphene films on an insulating substrate

Scanning Tunneling Spectroscopy has been utilized to study the differences between the electronic structure of a three-dimensional graphite crystal and its two-dimensional building block, graphene. Single and few-layer graphene samples were isolated on a non-conductive silicon dioxide substrate and contacted at the edges with a gold electrode. For single layer flakes current-voltage dependent I(V) curves, recorded at 4.6 K under Ultra-high Vacuum (UHV) conditions, show no additional features (for states far from the Fermi energy) that might be considered characteristic of a weak interaction between graphene and the substrate. No significant spatial inhomogeneity of local sample properties was observed. Evolution of spectroscopic curves as a function of graphene layers will be discussed.