Ultraviolet Raman Spectroscopy of Single and Multi-layer Graphene

TL;DR

This study explores ultraviolet Raman spectroscopy of graphene, revealing how UV excitation affects the G and 2D peaks, and providing new metrics for determining graphene layer number and quality.

Contribution

It demonstrates the distinct behavior of Raman peaks under UV excitation and introduces UV Raman features as tools for graphene characterization.

Findings

G peak remains prominent in UV Raman spectra.

2D band intensity is severely quenched under UV excitation.

The I(G)/I(2D) ratio evolution differs from visible Raman spectra.

Abstract

We investigated Raman spectra of single-layer and multi-layer graphene under ultraviolet laser excitation at the wavelength of 325 nm. It was found that while the G peak of graphene remains pronounced in UV Raman spectra, the 2D band intensity undergoes severe quenching. The evolution of the ratio of the intensities of the G and 2D peaks, I(G)/I(2D), as the number of graphene layers n changes from n=1 to n=5, is different in UV Raman spectra from that in conventional visible Raman spectra excited at the 488 nm and 633 nm wavelengths. The 2D band under UV excitation shifts to larger wave numbers and is found near 2825 1/cm. The observed UV Raman features of graphene were explained by invoking the resonant scattering model. The obtained results contribute to the Raman nanometrology of graphene by providing an additional metric for determining the number of graphene layers and assessing its quality.