Rayleigh Imaging of Graphene and Graphene Layers

• Published in: Nano letters Vol. 7; no. 9; pp. 2711 - 2717
• Main Authors: Casiraghi, C, Hartschuh, A, Lidorikis, E, Qian, H, Harutyunyan, H, Gokus, T, Novoselov, K. S, Ferrari, A. C
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.09.2007
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Graphite - chemistry; Macromolecular Substances - chemistry; Materials science; Materials Testing - methods; Microscopy - methods; Molecular Conformation; Nanostructures - chemistry; Nanostructures - ultrastructure; Nanotechnology - methods; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Particle Size; Physics; Refractometry - methods; Specific materials; Surface Properties; Raman scattering; Graphene; Light scattering; Imaging; Refractive index; Dielectric properties; Optical properties; Graphite; Confocal microscopy; Gallium selenides; Image contrast
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl071168m

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 a few layers (<6), the monochromatic contrast increases linearly with thickness. The data can be adequately understood by considering the samples behaving as a superposition of single sheets that act as independent two-dimensional electron gases. Thus, Rayleigh imaging is a general, simple, and quick tool to identify graphene layers, which is readily combined with Raman scattering, that provides structural identification.