Regensburg 2013 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 28: Poster Session: Graphen; Transport properties; Transport in high magnetic fields / Quantum Hall effect; Metal-semiconductor hybrid systems

HL 28.4: Poster

Montag, 11. März 2013, 16:00–20:00, Poster A

Graphene nanostructures produced from suspended and transfered layers — •Christopher Belke, Dmitri Smirnov, Johannes C. Rode, Hennrik Schmidt, and Rolf J. Haug — Institut für Festkörperphysik, Leibniz Universität Hannover, D-30167 Hannover, Germany

Graphene consists of carbon atoms, which are arranged in a two-dimensional honeycomb lattice. It has unique electronic properties, which can be examined in high quality samples. These are often prepared by mechanical exfoliation on a silicon wafer with silicon dioxide on top. This substrate has a strong influence on the transport properties due to charge traps and surface roughness [1]. To reduce these effects, there are different possibilities, from which two were tested on flakes with different numbers of layers.
a) Etching of the SiO₂ under the flake with hydrofluoric acid is used to make the samples suspended [2]. Afterwards, the flake is cleaned by current annealing, in which a high current flows through the flake, so that contaminations are removed by the generated heat.
b) Transfer of the flakes [3]. For this, graphene is exfoliated on a thin PMMA layer, which can be detached from the silicon wafer. This layer is then placed on another flake or substrate of choice.
Using these two methods, different nanostructures were produced and characterized.

[1] P. Barthold et al. NJP 13, 043020 (2011).

[2] K. I. Bolotin et al. Science-Direct, 146, 351 (2008).

[3] C. R. Dean et al. Nature nanotechnology, 5, 722 (2010).