Authors
VG Kravets, AN Grigorenko, RR Nair, P Blake, S Anissimova, KS Novoselov, AK Geim
Publication date
2010/4/15
Journal
Physical Review B—Condensed Matter and Materials Physics
Volume
81
Issue
15
Pages
155413
Publisher
American Physical Society
Description
We demonstrate that optical transparency of any two-dimensional system with a symmetric electronic spectrum is governed by the fine structure constant and suggest a simple formula that relates a quasiparticle spectrum to an optical absorption of such a system. These results are applied to graphene deposited on a surface of oxidized silicon for which we measure ellipsometric spectra, extract optical constants of a graphene layer and reconstruct the electronic dispersion relation near the point using optical transmission spectra. We also present spectroscopic ellipsometry analysis of graphene placed on amorphous quartz substrates and report a pronounced peak in ultraviolet absorption at 4.6 eV because of a van Hove singularity in graphene's density of states. The peak is asymmetric and downshifted by 0.5 eV probably due to excitonic effects.
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VG Kravets, AN Grigorenko, RR Nair, P Blake… - Physical Review B—Condensed Matter and Materials …, 2010