Berlin 2012 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 90: Graphene: Transport incl. Spin Physics and Magnetic Fields II
HL 90.4: Talk
Thursday, March 29, 2012, 17:45–18:00, ER 270
Influence of indium contacts on electronic transport in graphene — •Felix Nippert, Harald Scheel, Janina Maultzsch, and Christian Thomsen — Insititut für Festkörperphysik, Technische Universität Berlin
We study the influence of micro-soldered indium contacts on electronic transport in graphene. In four point transport measurements using a variable back gate voltage VG we observe a strong electron-hole-asymmetry that is associated with a Fermi energy shift in the vicinity of the contacts. This is due to n-type doping caused by differing work functions of graphene and indium. We propose a simple analytical model based on different mobilities for electrons and holes and a standard distribution of the Fermi level position to explain this asymmetry and the observed minimum conductivity.
We notice an additional resistance on the hole side, which we associate with a graphene pn-junction that arises when the bulk graphene is p-type while the region influenced by the contacts is still n-type. We compare our results with similar measurements in the literature involving other contact metals and show that they support our model.