Spatially Resolved Raman Spectroscopy of Single- and Few-Layer Graphene

TL;DR

This study employs spatially resolved Raman spectroscopy to differentiate single- and few-layer graphene by analyzing spectral features, providing insights into their structural properties and defect presence.

Contribution

It introduces a confocal Raman technique with spatial resolution to distinguish graphene layers and explains spectral differences using ab-initio calculations.

Findings

Single-layer graphene shows a single D' peak, while multilayer shows split peaks.

No defects detected within the graphene flakes.

Edge effects can produce D line signals due to symmetry breaking.

Abstract

We present Raman spectroscopy measurements on single- and few-layer graphene flakes. Using a scanning confocal approach we collect spectral data with spatial resolution, which allows us to directly compare Raman images with scanning force micrographs. Single-layer graphene can be distinguished from double- and few-layer by the width of the D' line: the single peak for single-layer graphene splits into different peaks for the double-layer. These findings are explained using the double-resonant Raman model based on ab-initio calculations of the electronic structure and of the phonon dispersion. We investigate the D line intensity and find no defects within the flake. A finite D line response originating from the edges can be attributed either to defects or to the breakdown of translational symmetry.