Dresden 2011 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
O: Fachverband Oberflächenphysik
O 51: Graphene III
O 51.1: Talk
Wednesday, March 16, 2011, 15:00–15:15, WIL B321
A graphene phase transition induced by compressing nanomembranes using STM. — •Alexander Georgi1, Dinesh Subramaniam1, Christian Pauly1, Torge Mashoff1, Ludger Wirtz2, Viktor Geringer1, Marcus Liebmann1, Marco Pratzer1, and Markus Morgenstern1 — 1II. Physikalisches Institut B, Otto-Blumenthal-Straße, RWTH Aachen University and JARA-FIT, 52074 Aachen — 2IEMN, Dept. ISEN, B.P. 60069, 59652 Villeneuve d’Ascq Cedex.
The variety of the different carbon allotropes is due to the energetic similarity between the sp2 and sp3 band. Even a metastable 3d structure of sp2 bands called K4 has been proposed [1].
Applying forces to a graphene flake exfoliated on SiO2 using an STM-tip the valleys of the intrinsic rippling can be lifted [2]. The induced compression during lifting leads to a transition from flat hexagonal graphene to a triangular appearence probably representing a buckled hexagonal structure resembling a diamond-like arrangement of the atoms. Further lifting leads to a reduction of the compression and a corresponding switch-back to the unbuckled phase. For valleys with 1.5 nm2, a buckling amplitude of 5 pm has been deduced, which is only 10% of the buckling within a 2d-diamond crystal. The phase transition cannot be reproduced by DFT Calculations so far.
[1] Itoh et al., Phys. Rev. Lett. 102, 055703 (2009).
[2] Mashoff et al., Nano Lett. 10, 461 (2010).