Surface-enhanced Raman scattering in graphene deposited on Al$_x$Ga$_{1-x}$N/GaN axial heterostructure nanowires

TL;DR

This study investigates the mechanism of surface-enhanced Raman scattering in graphene on AlGaN/GaN nanowires, concluding that chemical interactions, not electromagnetic effects, drive the enhancement.

Contribution

It provides experimental and theoretical evidence that the SERS in this system is due to chemical mechanisms, not plasmonic electromagnetic effects.

Findings

Raman intensity not correlated with aluminium content

Screening of polarization charges observed via KPFM and electroreflectance

Plasmon resonance in graphene is outside the Raman spectral range

Abstract

The surface-enhanced Raman scattering in graphene deposited on AlxGa1-xN/GaN axial heterostructure nanowires was investigated. The intensity of graphene Raman spectra was found not to be correlated with aluminium content. Analysis of graphene Raman bands parameters, KPFM and electroreflectance showed a screening of polarization charges. Theoretical calculations showed that plasmon resonance in graphene is far beyond the Raman spectral range. This excludes the presence of an electromagnetic mechanism of SERS and therefore suggests the chemical mechanism of enhancement.