Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 23: Scanning probe methods II

O 23.3: Talk

Monday, March 14, 2011, 17:45–18:00, WIL C307

Simultaneous current and force microscopy on epitaxial graphene — •Thomas Hofmann, Markus Duschl, and Franz J. Giessibl — University of Regensburg, Faculty of Experimental and Applied Physics II - Physics, Universitätsstrasse 31, D-93053 Regensburg

Graphite has been investigated extensively with NC-AFM at low temperatures [1]. However, at room temperature atomic resolution could not be achieved. We speculate that the weakly bond layers of the graphite lead to large thermal oscillations normal to the surface. This prevents stable oscillation of the cantilever at room temperature. To circumvent this problem, single layer graphene on SiC [2] is used as sample system. We found that in contrast to the findings on graphite, stable imaging at room temperature and at small tip-sample distances is possible. In this talk we present constant height images which show atomic contrast in both the current and the Δf channel. In the current image both six-fold and three-fold symmetry are observed, attributed to the carbon rings and holes respectively. In both cases the Δf images only show the carbon rings. Consistent with the findings of Hembacher et al. [1], the carbon atoms can only be resolved at tip-sample distances, where the tip atom already feels repulsive forces.

[1] S. Hembacher and F.J. Giessibl and J. Mannhart, and C.F. Quate, Phys. Rev. Lett. 94, 056101 (2005)

[2] P. Lauffer, K. V. Emtsev, R. Graupner, Th. Seyller, and L. Ley, Phys. Rev. B 77, 155426 (2008)