Berlin 2015 – wissenschaftliches Programm
TT 50.15: Poster
Dienstag, 17. März 2015, 18:15–21:00, Poster A
Preparation of high mobility graphene samples for combined transport and STM experiments — •Tjorven Johnsen, Felix Jekat, Nils Freitag, Peter Nemes-Incze, and Markus Morgenstern — II. Physikalisches Institut B, RWTH Aachen, Otto-Blumenthal-Straße, 52074 Aachen
Graphene on boron nitride provides the possibility to measure high mobility two dimensional electron systems by scanning tunneling microscopy. For this kind of measurement clean surfaces are crucial leading to the requirement that the exposed graphene surface has to be clean of processing residues. Adapting a dry transfer method presented by Kretinin et al.  for graphene transfer on boron nitride and employing shadow mask evaporation we are able to produce ultra clean graphene surfaces. A graphene flake is placed on a boron nitride flake exfoliated on SiO2/Si chip serving as the back gate. Charge carrier concentration can thus be controlled during the experiment. The graphene flake (30 × 30 µ m, bubble free area of 10 × 10 µ m) is contacted by 50 nm gold contacts defined by shadow mask evaporation. Homemade glass fibers  and TEM grids are utilized as shadow masks with alignment precision down to 2 µm. Four probe transport measurements exhibit high mobility (50,000 cm2/Vs) and symmetry breaking in Quantum Hall Effect at 0.3 K. We also report on the less successful contacting by microsoldering .
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V. Geringer et al., Appl. Phys. Lett. 96, 082114 (2010)