Probing the Intrinsic Properties of Exfoliated Graphene: Raman Spectroscopy of Free-Standing Monolayers
Year: 2008
Type: article
Abstract: The properties of pristine, free-standing graphene monolayers prepared by mechanical exfoliation of graphite are investigated. The graphene monolayers, suspended over open trenches, are examined by means of spatially resolved Raman spectroscopy of the G-, D-, and 2D-phonon modes. The G-mode phonons exhibit reduced energies (1580 cm(-1)) and increased widths (14 cm(-1)) compared to the response of graphene monolayers supported on the SiO(2)-covered substrate. From analysis of the G-mode Raman spectra, we deduce that the free-standing graphene monolayers are essentially undoped, with an upper bound of 2 x 10(11) cm(-2) for the residual carrier concentration. On the supported regions, significantly higher and spatially inhomogeneous doping is observed. The free-standing graphene monolayers show little local disorder, based on the very weak Raman D-mode response. The two-phonon 2D mode of the free-standing graphene monolayers is downshifted in frequency compared to that of the supported region of the samples and exhibits a narrowed, positively skewed line shape.
Source: Nano Letters
DOI: 10.1021/nl8031444
Authors: Stéphane Berciaud, Sunmin Ryu, Louis E. Brus, Tony F. Heinz
Institution: Columbia University
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Awards: CONTROLLING STRUCTURAL, ELECTRONIC AND ENERGY FLOW DYNAMICS OF CATALYTIC PROCESSES THROUG TAILORED NANOSTRUCTURES, Nanoscience and Engineering Center: Columbia Center for Electronic Transport in Molecular Nanostructures, G5646046392, G5648016710, CONTROLLING STRUCTURAL, ELECTRONIC AND ENERGY FLOW DYNAMICS OF CATALYTIC PROCESSES THROUG TAILORED NANOSTRUCTURES, G8476215133
OpenAlex ID: W2140444203