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HL: Fachverband Halbleiterphysik
HL 4: Carbon: Diamond, Nanotubes, and Graphene
HL 4.9: Vortrag
Montag, 14. März 2011, 12:30–12:45, POT 251
Optical Absorption of Free-standing Monolayer and Bilayer Graphene in the Ultraviolet Regime — •Tobias Utikal1,2, Dong-Hun Chae1, Siegfried Weisenburger1,2, Harald Giessen2, Markus Lippitz1,2, and Jurgen Smet1 — 1Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany — 24th Physics Institute, University of Stuttgart, 70550 Stuttgart, Germany
We present direct measurements of the optical absorption of free-standing graphene and Bernal-stacked bilayer graphene from the infrared to the ultraviolet regime. In the visible part of the spectrum our data show a slowly rising absorption towards the blue spectral region. The absolute values clearly reproduce previous findings and can be attributed to a renormalized fine structure constant [1].
However, in the ultraviolet regime, the spectra show a strong increase of the absorption. Broad peaks appear at 4.55 eV and 4.52 eV for monolayer and bilayer graphene, respectively. Using a simple model we can reproduce the experimental data in the ultraviolet as well as in the infrared regime with nearly perfect agreement. From our findings we conclude that the shape of the absorption spectra is a direct consequence of the unique band structure of graphene and its bilayer.
[1] Nair et al., Science 320, 1308 (2008)