Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 82: Graphene IV
O 82.6: Vortrag
Freitag, 26. März 2010, 12:30–12:45, H31
Crystal Symmetry and Stress in Epitaxial Graphene Films — •Diedrich Schmidt1 and Taisuke Ohta2 — 1Department of Physical Chemistry II, Ruhr-University Bochum, 44780 Germany — 2Sandia National Laboratories, Albuquerque, NM 87185 USA
We performed combined confocal Raman microspectroscopy and atomic force microscopy (AFM) studies to address discrepancies in the reported electronic properties and characteristic Raman bands of monolayer epitaxial graphene. Monolayer graphene was made by sublimation of Si from a SiC substrate at elevated temperature in an argon environment [1]. Our samples exhibit variation in both the G and 2D peak positions presumably due to strain; similar to previous work [2]. However, our monolayer films show large areas of uniform compressive strain covering ≥40% of the surface with nearly equivalent coverage of smaller, quasi strain-relieved regions which are oriented at multiples of 30∘ to each other. AFM phase data confirm the quasi strain-relieved areas seen in Raman microspectroscopy are physical effects that exist within the monolayer film, or that are induced in the film by interactions with the interface layer. Due to the high symmetry of the C-rich interface layer [3], we propose that these regions are controlled by the interface layer.
This work is supported in part by the LDRD program at Sandia Labs and by the German BMBF under grant 05KS7PC2.
[1] K. V. Emtsev, et al., Nature Materials 8, 203 (2009).
[2] J. A. Robinson, et al., Nano Letters 9, 964 (2009).
[3] K. V. Emstev, et al., Phys. Rev. B 77, 155303 (2008).