Berlin 2015 – scientific programme
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DS: Fachverband Dünne Schichten
DS 35: Graphen
DS 35.8: Talk
Thursday, March 19, 2015, 11:30–11:45, H 0111
Field induced enhancement of refractive index and conductivity - a substrate effect in graphene — •Matthias Vaupel1, Anke Dutschke1, Ulrich Wurstbauer2, and Frank Hitzel3 — 1Carl Zeiss Microscopy GmbH, Königsallee 9-21, 37081 Göttingen, Germany — 2Dept. of Physics, Columbia University New York, NY 10027, USA — 3DME Nanotechnologie GmbH, D-38106 Braunschweig, Germany
We study the effect of different substrates, conductive Si vs. isolating SiO2, on the electro-optic properties of graphene layers. To this end phase profiles of graphene layers were recorded by total interference contrast (TIC) microscopy, while atomic force microscopy measured the topography of the layers [1]. An optical model consistent with the measured height and phase profile of graphene yields the refractive index N and conductivity of graphene. Extraordinary high N = 3.9 + 9.2 i is obtained for the graphene on conductive substrate. The optical conductivity is 38 fold increased with respect to the reference value obtained on isolating substrate by TIC [1] and by ellipsometry [2]. These observations are mathematically consistent with the dielectric Drude function, which describes a damped harmonic electron oscillation with zero eigenfrequency and nonzero effective electron mass. The model applies for FETs and electro-optic devices made of graphene.
[1] M. Vaupel, A. Dutschke, U. Wurstbauer, F. Hitzel, A. Pasupathy, J.Appl.Phys. 114, (2013) 183107 [2] U. Wurstbauer, C. Röling, U. Wurstbauer, W. Wegscheider, M. Vaupel, P.H. Thiesen, D. Weiss, Appl. Phys. Lett. 97, (2010) 231901