Scanning Gate Microscopy of Localized States in Wide Graphene Constrictions

Abstract

In graphene nanoconstrictions, charge puddles due to substrate-induced potential inhomogeneities can form quantum dots. We use a scanning gate microscope to probe a short, wide graphene constriction and observe a set of ring-shaped resonances in maps of the graphene conductance as a function of the local potential perturbation, a signature of quantum dot-mediated transport. By varying the scanning tip height and applied tip voltage, we observe the screening effect of the nearby graphene. Introducing a simple capacitive model to account for screening, we model the conduction of the graphene constriction and how the tip gates the quantum dots. We identify the locations of some of the quantum dots and extract their parameters.