Scanning gate microscopy of current-annealed single layer graphene

TL;DR

This study uses scanning gate microscopy to investigate how current annealing affects local conductivity and neutrality point inhomogeneities in single-layer graphene, revealing inhomogeneity reduction and persistent asymmetries.

Contribution

It demonstrates the impact of different current densities during annealing on local electronic inhomogeneities in graphene using scanning gate microscopy.

Findings

Low current annealing causes micron-sized NP inhomogeneities.

Higher current annealing reduces NP inhomogeneity.

Persistent e-h conduction asymmetry linked to contact doping and local NP striations.

Abstract

We have used scanning gate microscopy to explore the local conductivity of a current-annealed graphene flake. A map of the local neutrality point (NP) after annealing at low current density exhibits micron-sized inhomogeneities. Broadening of the local e-h transition is also correlated with the inhomogeneity of the NP. Annealing at higher current density reduces the NP inhomogeneity, but we still observe some asymmetry in the e-h conduction. We attribute this to a hole doped domain close to one of the metal contacts combined with underlying striations in the local NP.