Surface Enhanced Raman Spectroscopy of Graphene

TL;DR

This paper demonstrates surface enhanced Raman spectroscopy (SERS) on graphene using gold nanoparticle arrays, providing a quantitative theory that explains the enhancement mechanisms specific to the two-dimensional nature of graphene.

Contribution

It introduces a detailed analytical and numerical model for SERS on graphene, highlighting the role of nanoparticle size and separation in the enhancement effect.

Findings

Significant Raman enhancement observed at 633nm on graphene with gold nanoparticles.

The enhancement scales with nanoparticle cross section and the fourth power of Mie enhancement.

The enhancement inversely scales with the tenth power of the separation between graphene and nanoparticles.

Abstract

Surface enhanced Raman scattering (SERS) exploits surface plasmons induced by the incident field in metallic nanostructures to significantly increase the Raman intensity. Graphene provides the ideal prototype two dimensional (2d) test material to investigate SERS. Its Raman spectrum is well known, graphene samples are entirely reproducible, height controllable down to the atomic scale, and can be made virtually defect-free. We report SERS from graphene, by depositing arrays of Au particles of well defined dimensions on graphene/SiO$_2$(300nm)/Si. We detect significant enhancements at 633nm. To elucidate the physics of SERS, we develop a quantitative analytical and numerical theory. The 2d nature of graphene allows for a closed-form description of the Raman enhancement. This scales with the nanoparticle cross section, the fourth power of the Mie enhancement, and is inversely proportional to the tenth power of the separation between graphene and the nanoparticle. One consequence is that metallic nanodisks are an ideal embodiment for SERS in 2d.