Charge Puddles in Graphene Near the Dirac Point

Understand

The charge carrier density in graphene on a dielectric substrate such as SiO$_2$ displays inhomogeneities, the so-called charge puddles.

• Because of the linear dispersion relation in monolayer graphene, the puddles are predicted to grow near charge neutrality, a markedly distinct property from conventional two-dimensional electron gases.
• By performing scanning tunneling microscopy/spectroscopy on a mesoscopic graphene device, we directly observe the puddles' growth, both in spatial extent and in amplitude, as the Dirac point is approached.
• Self-consistent screening theory provides a unified description of both the macroscopic transport properties and the microscopically observed charge disorder.