Spectroscopic ellipsometry of graphene and an exciton-shifted van Hove peak in absorption

By V. Kravets, A. Grigorenko, R. Nair, P. Blake, S. Anissimova, K. Novoselov, A.K. Geim. Physical review B, 2010

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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 K 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.

Subfields: Biomedical Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/a98d3d805c740760bfa45a6beeeb366c8a2b3bc9

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Citations in the corpus

Graphene based materials: Past, present and future (2011, background): “Graphene transmittance can be well described in terms of fine structure constants [160,199].”
Nobel Lecture: Graphene: Materials in the Flatland (2011, background): “Graphene is unusually optically active (Kuzmenko et al., 2008; Li et al., 2008; Nair et al., 2008; Kravets et al., 2010) and absorbs a rather large fraction of incoming light for a monolayer (2.3%), but this is still significantly smaller than the typical absorption coefficient which could be…”
Fluorographene: a two-dimensional counterpart of Teflon. (2010, methodology): “he upper curve is for graphene and, within experimental error, follows the low-E data of ref. [31]. Beyond the previously reported range (<3eV), graphene exhibits an absorption peak in ultraviolet [35]. Partially fluorinated graphene shows higher transparency (middle curve). FF graphene is transp”
Inkjet-printed graphene electronics. (2011, background): “peak in the UV region being a signature of the van Hove singularity in the graphene density of states.(94) From R≈ 1390 L g 1 m 1 at 660 nm, as for refs 57 and 59, we estimate c ≈ 0.”
Optical Third-Harmonic Generation in Graphene (2013, background): “6 eV [7–9], which is approximately three-photon resonant with our fundamental photon energy of 1.”