Infrared study of carrier scattering mechanism in ion-gated graphene

TL;DR

This study investigates how carrier scattering mechanisms in ion-gated graphene vary with carrier density using infrared transmission, revealing the dominance of charged impurity and short-range disorder scattering, and how these are affected by ion-gel gating.

Contribution

It provides a detailed n-dependent map of scattering mechanisms in ion-gated graphene, quantifies their strengths, and compares them with SiO2-gated graphene, highlighting the dual role of the ion-gel layer.

Findings

Carrier scattering rate g(n) decreases then increases with doping.

Charged impurity and short-range disorder are the main scattering mechanisms.

Ion-gel layer enhances scattering compared to SiO2-gated graphene.

Abstract

We performed infrared transmission experiment on ion-gel gated graphene and measured carrier scattering rate g as function of carrier density n over wide range up to n=2E13 cm-2. The g exhibits a rapid decreases along with the gating followed by persistent increases on further carrier doping. This behavior of g(n) demonstrates that carrier is scattered dominantly by the two scattering mechanisms, namely, charged impurity (CI) scattering and short-range disorder (SR) scattering, with additional minor scattering from substrate phonon (SPP). We can determine the absolute strengths of all the scattering channels by fitting the g(n) data and unveils the complete n-dependent map of the scattering mechanisms g(n)=gCI(n)+gSR(n)+gSPP(n). The gCI(n) and gSR(n) are larger than those of SiO2$-gated graphene by 1.8 times, which elucidates the dual role of the ion-gel layer as a CI-scatterer and simultaneously a SR-scatterer to graphene. Additionally we show that freezing of IG at low-T (~200 K) does not cause any change to the carrier scattering.