Infrared spectroscopic study of carrier scattering in gated CVD graphene

TL;DR

This study uses infrared spectroscopy to analyze how different scattering mechanisms affect carrier mobility in gated CVD graphene under various environmental conditions, providing a comprehensive scattering map.

Contribution

It presents the first complete scattering map of CVD graphene, identifying dominant scattering sources and their strengths under different conditions.

Findings

Charged impurities and defects dominate low-temperature scattering.

Surface polar phonons are the main scattering source at room temperature.

Adsorbed gas molecules contribute to scattering as charged impurities and resonant centers.

Abstract

We measured Drude absorption of gated CVD graphene using far-infrared transmission spectroscopy, and determined carrier scattering rate (g) as function of the varied carrier density (n). The n-dependent g(n) was obtained for a series of conditions systematically changed as (10 K, vacuum) -> (300 K, vacuum) -> (300 K, ambient pressure), which reveals that (1) at low-T, charged impurity (=A/sqrt(n)) and short-range defect (=B*sqrt(n)) are the major scattering sources which constitute the total scattering g=A/sqrt(n)+B*sqrt(n), (2) among various kinds of phonons populated at room-T, surface polar phonon of the SiO2 substrate is the dominantly scattering source, (3) in air, the gas molecules adsorbed on graphene play a dual role in carrier scattering as charged impurity center and resonant scattering center. We present the absolute scattering strengths of those individual scattering sources, which provides the complete map of scattering mechanism of CVD graphene for the first time. This scattering map allows us find out practical measures to suppress the individual scatterings, the mobility gains accompanied by them, and finally the ultimate attainable carrier mobility for CVD graphene.