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TT: Fachverband Tiefe Temperaturen

TT 78: Graphene: Electronic Properties (organized by O)

TT 78.5: Vortrag

Mittwoch, 2. April 2014, 17:00–17:15, WIL C107

Scattering mechanisms in Tl-doped epitaxial graphene — •Carola Straßer¹, Bart Ludbrook², Andrea Damascelli², Christian R. Ast¹, and Klaus Kern^1,3 — ¹Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany — ²Quantum Matter Institute, UBC, Vancouver, BC V6T 1Z4, Canada — ³Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland

Since the charge carrier density in graphene can very easily be tuned by means of chemical doping this approach counts as a promising way to design graphene-based future electronic devices. It was shown [1] that the Fermi level can be shifted over a wide range in either direction. But one has to consider that the dopants do not just donate or take the electrons but they have an impact on the electronic structure: they act as scattering centres and change the charge carrier mobility.

We investigated small amounts of Thallium atoms on a monolayer of epitaxial graphene by angular resolved photoemission spectroscopy and did a careful analysis of the line width. Although Tl is very weakly bound and at first sight a paradigm long-range scatterer, we found that it introduces a sizeable short-range contribution. Only by using a model which combines both, long-range and short-range scattering we were able to describe our observations. This allowed us to put an upper limit on the dielectric constant for Tl-doped epitaxial graphene.

[1] H. Liu et al., J. Mater. Chem. 21, 3335 (2011)