Dresden 2009 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 48: Poster 2

HL 48.33: Poster

Donnerstag, 26. März 2009, 15:00–17:30, P2

Magnetotransport properties of epitaxial graphene — •Sonja Weingart¹, Claudia Bock¹, Ulrich Kunze¹, Konstantin V. Emtsev², Thomas Seyller², and Lothar Ley² — ¹Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum — ²Lehrstuhl für Technische Physik, Friedrich-Alexander Universität Erlangen-Nürnberg

We have investigated the magnetotransport properties of epitaxial graphene films grown on 6H-SiC(0001). We demonstrate that the temperature dependence of the charge carrier density and mobility is correlated to the annealing conditions during the graphitisation process. Devices in a Hall-bar geometry are characterised in a perpendicular magnetic field up to 8 T at temperatures between 1.5 K and 110 K. The electron density is determined from Shubnikov de Haas oscillations of the longitudinal resistance R_xx and, for comparison, from Hall-effect measurements of the transverse resistance R_xy. The mobility is derived from the conductivity. For graphene films annealed in an Ar atmosphere close to atmospheric pressure (sample A) a mobility (charge carrier density) of 2400 cm²(Vs)⁻¹ (3 · 10¹² cm⁻²) at 4.2 K is extracted. Whereas for sample B annealed under a reduced pressure a lower mobility of 1000 cm²(Vs)⁻¹ and a slightly higher charge carrier density of 4· 10¹² cm⁻² is estimated. Sample A shows a nearly constant carrier mobility for low temperatures (1.5 K up to 60 K) and a linear decrease for higher temperatures. The charge carrier density is constant in the temperature range. For sample B with rising temperature the mobility (charge carrier density) decreases (increases).