Diffusive Charge Transport in Graphene on SiO2

TL;DR

This paper reviews how charged impurities, dielectric environment, ripples, and phonons affect charge transport in graphene on SiO2, providing a comprehensive understanding of mobility limitations in this material.

Contribution

It systematically differentiates the effects of charged impurities and short-range scatterers, and evaluates the roles of ripples and phonons in graphene's charge transport.

Findings

Charged impurities cause linear conductivity in density, matching theoretical estimates.

Dielectric screening reduces charged impurity scattering but increases short-range scatterers.

Graphene ripples do not significantly affect mobility via long-range or short-range scattering.

Abstract

We review our recent work on the physical mechanisms limiting the mobility of graphene on SiO2. We have used intentional addition of charged scattering impurities and systematic variation of the dielectric environment to differentiate the effects of charged impurities and short-range scatterers. The results show that charged impurities indeed lead to a conductivity linear in density in graphene, with a scattering magnitude that agrees quantitatively with theoretical estimates [1]; increased dielectric screening reduces scattering from charged impurities, but increases scattering from short-range scatterers [2]. We evaluate the effects of the corrugations (ripples) of graphene on SiO2 on transport by measuring the height-height correlation function. The results show that the corrugations cannot mimic long-range (charged impurity) scattering effects, and have too small an amplitude-to-wavelength ratio to significantly affect the observed mobility via short-range scattering [3, 4]. Temperature-dependent measurements show that longitudinal acoustic phonons in graphene produce a resistivity linear in temperature and independent of carrier density [5]; at higher temperatures, polar optical phonons of the SiO2 substrate give rise to an activated, carrier density-dependent resistivity [5]. Together the results paint a complete picture of charge carrier transport in graphene on SiO2 in the diffusive regime.