Berlin 2012 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
O: Fachverband Oberflächenphysik
O 86: Graphene VI
O 86.1: Vortrag
Freitag, 30. März 2012, 10:30–10:45, MA 041
Observation of an activation barrier in the interaction between graphene and a metal tip by using atomic force-microscopy and -spectroscopy — •Thomas Hofmann, Alfred J. Weymouth, Joachim Welker, and Franz J. Giessibl — University of Regensburg, Faculty of Experimental and Applied Physics, Universitätsstrasse 31, D-93053 Regensburg
For chemical bonding of adsorbed atoms onto graphene, the participating carbon atom has to change its hybridization state from sp2 to sp3. This rehybridization has been described for bonding of hydrogen on graphite, leading to an activation barrier [1]. We studied the interaction of a tungsten tip with monolayer graphene with a low temperature atomic force microscope. As the tip is approached to the surface, atomic contrast initially is obtained in a repulsive regime, i.e. the carbon atoms appear to repel the tip similar to measurements on pentacene [2]. Upon further reducing the distance, the image contrast flips and the carbon atoms attract the tip, as has been proposed by DFT calculations [3]. Force versus distance spectroscopy shows a pronounced barrier that has to be overcome before the carbon atoms appear attractive.
[1] L. Jeloaica, V. Sidis, Chem. Phys. Lett. 300, 157 (1999)
[2] L. Gross et al., Science 325, 5944 (2009)
[3] M. Ondráĉek et al., Phys. Rev. Lett. 106, 176101 (2011)