Raman imaging of doping domains in graphene on SiO2

TL;DR

This study uses spatially resolved Raman imaging to map doping domains in single-layer graphene on SiO2, revealing how the G and 2D Raman lines vary with local doping levels and providing insights into doping effects.

Contribution

The paper introduces a method to visualize and analyze local doping domains in graphene using Raman imaging, highlighting differences in doping response between G and 2D lines.

Findings

G and 2D lines are correlated with local doping domains.

2D line position shifts weakly and asymmetrically with doping.

2D line width remains doping-independent, aiding in graphene identification.

Abstract

We present spatially resolved Raman images of the G and 2D lines of single-layer graphene flakes. The spatial fluctuations of G and 2D lines are correlated and are thus shown to be affiliated with local doping domains. We investigate the position of the 2D line -- the most significant Raman peak to identify single-layer graphene -- as a function of charging up to |n|~4 10^12 cm^-2. Contrary to the G line which exhibits a strong and symmetric stiffening with respect to electron and hole-doping, the 2D line shows a weak and slightly asymmetric stiffening for low doping. Additionally, the line width of the 2D line is, in contrast to the G line, doping-independent making this quantity a reliable measure for identifying single-layer graphene.