Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 86: Graphene VI
O 86.8: Vortrag
Freitag, 30. März 2012, 12:15–12:30, MA 041
Screening of charges by graphene layers — Daniel Niesner1, Marko Kralj2, and •Thomas Fauster1 — 1Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen, Germany — 2Institut za fiziku, Bijenička 46, HR-10000 Zagreb, Croatia
The screening of external charges by a two-dimensional electron gas is studied by spectroscopy of loosely bound electrons on graphene grown on various substrates. The charge transfer from the substrate to the graphene layer (doping) is correlated with the work function and the energy of the Dirac point in good agreement with theoretical predictions [1]. The spectroscopy of the unoccupied states by two-photon photoemission reveals that the long-range image potential applies only for energies close to the vacuum level. The lowest state is found at 3.7 eV above the Dirac point independent of the substrate. This indicates that for this state the screening is dominated by the electronic structure of the graphene layer.
[1] P. A. Khomyakov et al., Phys. Rev. B 79, 195425 (2009).