Disorder induced Dirac-point physics in epitaxial graphene from temperature-dependent magneto-transport measurements

TL;DR

This study investigates how disorder affects epitaxial graphene near the Dirac point through temperature-dependent magneto-transport measurements, revealing insights into carrier behavior, scattering mechanisms, and conductivity variations.

Contribution

It provides experimental quantification of disorder effects and impurity scattering in epitaxial graphene, aligning results with theoretical models.

Findings

Carrier density increases quadratically with temperature.

Disorder strength ranges from 10.2 to 31.2 meV.

Minimum conductivity rises with disorder potential.

Abstract

We report a study of disorder effects on epitaxial graphene in the vicinity of the Dirac point by magneto-transport. Hall effect measurements show that the carrier density increases quadratically with temperature, in good agreement with theoretical predictions which take into account intrinsic thermal excitation combined with electron-hole puddles induced by charged impurities. We deduce disorder strengths in the range 10.2 $\sim$ 31.2 meV, depending on the sample treatment. We investigate the scattering mechanisms and estimate the impurity density to be $3.0 \sim 9.1 \times 10^{10}$ cm$^{-2}$ for our samples. An asymmetry in the electron/hole scattering is observed and is consistent with theoretical calculations for graphene on SiC substrates. We also show that the minimum conductivity increases with increasing disorder potential, in good agreement with quantum-mechanical numerical calculations.