Mapping the Dirac point in gated bilayer graphene

TL;DR

This study uses low temperature scanning tunneling spectroscopy to map the Dirac point in gated bilayer graphene, revealing how electric fields and impurities influence its electronic properties.

Contribution

It provides the first spatially resolved measurements of the Dirac point in bilayer graphene under gating, highlighting impurity effects.

Findings

Dirac point shifts linearly with gate voltage

Electric field induces a band gap opening

Spatial variation of the Dirac point is due to charged impurities

Abstract

We have performed low temperature scanning tunneling spectroscopy measurements on exfoliated bilayer graphene on SiO2. By varying the back gate voltage we observed a linear shift of the Dirac point and an opening of a band gap due to the perpendicular electric field. In addition to observing a shift in the Dirac point, we also measured its spatial dependence using spatially resolved scanning tunneling spectroscopy. The spatial variation of the Dirac point was not correlated with topographic features and therefore we attribute its shift to random charged impurities.