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O: Fachverband Oberflächenphysik
O 60: Poster Session IV (Solid/liquid interfaces; Semiconductors; Oxides and insulators; Graphene; Plasmonics and nanooptics; Electronic Structure; Surface chemical reactions; Heterogeneous catalysis)
O 60.38: Poster
Mittwoch, 16. März 2011, 17:30–21:00, P4
Electronic scattering at defects in graphene investigated by scanning tunneling microscopy — •Marco Pratzer, Alexander Georgi, Viktor Geringer, Christian Pauly, Dinesh Subramaniam, Torge Mashoff, Marcus Liebmann, and Markus Morgenstern — II. Physikalisches Institut B, Otto-Blumenthal-Straße, RWTH Aachen University and JARA-FIT, 52074 Aachen
We investigated the electronic scattering pattern appearing at different types of defects in monolayer graphene by scanning tunneling microscopy (STM) at 5 K. The graphene sample has been prepared by exfoliation on a SiO2-substrate and electrically contacted by indium microsoldering.
First the electronic scattering pattern appearing at a monolayer-bilayer step edge has been investigated. Using FFT-filtering a √3×√3 interference pattern could be separated from the atomic corrugation, which is characteristic for the graphene intervalley scattering. The amplitude of the interference pattern decreases with increasing energy. This is caused by the growth of the equipotential lines in k-space leading to the overlap of more wave vectors and partially to a destructive interference. Further we could identify different types of point defects and their characteristic local density of states. In addition to adsorbates on top of the graphene lattice and carbon vacancies we found defects located below the graphene flake at the SiO2 substrate. The interference pattern caused by this type of defects could be suppressed by lifting up the graphene flake from the substrate using tip induced forces.