Rayleigh Imaging of Graphene and Graphene Layers

TL;DR

This paper demonstrates that Rayleigh scattering microscopy can effectively identify and characterize graphene layers on various substrates by analyzing contrast variations related to their dielectric properties and thickness.

Contribution

It introduces a quantitative model linking Rayleigh contrast to the complex refractive index, enabling simple and rapid identification of graphene layers.

Findings

Contrast increases linearly with layer thickness for fewer than 6 layers

Rayleigh imaging can distinguish graphene layers from substrates effectively

The method complements Raman scattering for structural analysis

Abstract

We investigate graphene and graphene layers on different substrates by monochromatic and white-light confocal Rayleigh scattering microscopy. The image contrast depends sensitively on the dielectric properties of the sample as well as the substrate geometry and can be described quantitatively using the complex refractive index of bulk graphite. For few layers (<6) the monochromatic contrast increases linearly with thickness: the samples behave as a superposition of single sheets which act as independent two dimensional electron gases. Thus, Rayleigh imaging is a general, simple and quick tool to identify graphene layers, that is readily combined with Raman scattering, which provides structural identification.