Electrochemically Top Gated Graphene: Monitoring Dopants by Raman Scattering

TL;DR

This study demonstrates electrochemical top gating of graphene using a solid polymer electrolyte, enabling high doping levels and real-time Raman monitoring of doping effects through peak shifts and intensity ratios.

Contribution

It introduces a method for high-level electrochemical doping of graphene with in-situ Raman spectroscopy to monitor doping-induced changes.

Findings

G peak stiffens and sharpens with doping

2D peak shifts differently for electrons and holes

G/2D intensity ratio is highly doping-sensitive

Abstract

We demonstrate electrochemical top gating of graphene by using a solid polymer electrolyte. This allows to reach much higher electron and hole doping than standard back gating. In-situ Raman measurements monitor the doping. The G peak stiffens and sharpens for both electron and hole doping, while the 2D peak shows a different response to holes and electrons. Its position increases for hole doping, while it softens for high electron doping. The variation of G peak position is a signature of the non-adiabatic Kohn anomaly at $\Gamma$. On the other hand, for visible excitation, the variation of the 2D peak position is ruled by charge transfer. The intensity ratio of G and 2D peaks shows a strong dependence on doping, making it a sensitive parameter to monitor charges.