Observation of Electron-Hole Puddles in Graphene Using a Scanning Single Electron Transistor

Understand

The electronic density of states of graphene is equivalent to that of relativistic electrons.

• In the absence of disorder or external doping the Fermi energy lies at the Dirac point where the density of states vanishes.
• Although transport measurements at high carrier densities indicate rather high mobilities, many questions pertaining to disorder remain unanswered.
• In particular, it has been argued theoretically, that when the average carrier density is zero, the inescapable presence of disorder will lead to electron and hole puddles with equal probability.