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HL: Fachverband Halbleiterphysik

HL 22: Graphene 2 (Joint Session with TT)

HL 22.7: Vortrag

Dienstag, 23. März 2010, 11:15–11:30, H21

Top and bottom gated field effect devices on epitaxial graphene — •Daniel Waldmann¹, Johannes Jobst¹, Florian Speck², Thomas Seyller² und Heiko B. Weber¹ — ¹Lehrstuhl für Angewandte Physik, Universtität Erlangen-Nürnberg, Erlangen, Germany — ²Lehrstuhl für Technische Physik, Universtität Erlangen-Nürnberg, Erlangen, Germany

We fabricate high-quality epitaxial graphene devices (Hall bars) for electrical transport measurements. In order to tune the charge density in the graphene layer, we developed different gating schemes (top gate and bottom gate). As a top gate we either used an electrochemical gate employing an ionic liquid or a solid state gate using aluminium oxide. A bottom gate has the advantage of leaving the graphene layer open. We have opted for an implanted conducting layer buried in the semi-insulating silicon carbide substrate. Hence, the SiC above the implanted gate serves both as substrate and gate dielectric. We present experimental data from low temperatures to room temperature which cover a broad range of charge densities including the electron hole transition at the Dirac point. Advantages and limitations of each method are discussed.