Measurement of Scattering Rate and Minimum Conductivity in Graphene

TL;DR

This paper investigates how disorder affects graphene's conductivity, estimating impurity levels and analyzing the roles of short and long-range scatterers across samples with varying mobility.

Contribution

It provides experimental measurements of scattering rates and conductivity in graphene, comparing results with theoretical models to identify disorder types and impurity concentrations.

Findings

Impurity concentrations range from 2 to 15×10^{11} cm^{-2}.

Conductivity at low carrier density varies from 2 to 12 e^2/h.

High mobility samples show short-range disorder, low mobility samples are dominated by long-range scatterers.

Abstract

The conductivity of graphene samples with various levels of disorder is investigated for a set of specimens with mobility in the range of $1-20\times10^3$ cm$^2$/V sec. Comparing the experimental data with the theoretical transport calculations based on charged impurity scattering, we estimate that the impurity concentration in the samples varies from $2-15\times 10^{11}$ cm$^{-2}$. In the low carrier density limit, the conductivity exhibits values in the range of $2-12e^2/h$, which can be related to the residual density induced by the inhomogeneous charge distribution in the samples. The shape of the conductivity curves indicates that high mobility samples contain some short range disorder whereas low mobility samples are dominated by long range scatterers.