Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 71: Poster Session: Graphene / Topological Insulators / Interfaces and Surfaces

HL 71.20: Poster

Mittwoch, 28. März 2012, 16:00–19:00, Poster D

Transport through structured ultra-thin Bi₂Se₃ flakes — •Regine Ockelmann^1,2, Christian Volk^1,2, Anton Maier^1,2, and Christoph Stampfer^1,2 — ¹JARA-FIT and II. Institute of Physics B, RWTH Aachen, 52074 Aachen, Germany — ²PGI, Forschungszentrum Jülich, 52425 Jülich, Germany

Topological insulators (TIs) are a new class of solid state materials with unique electronic properties showing both carriers mimicking relativistic particles and topological protection of their surface states. Theory predicts topological insulators to exhibit a rich variety of physical phenomena such as anomalous magneto-electric coupling, Majorana excitations and unusual spin-orbit interaction. Bismuth (Bi) based compounds such as Bi₂Se₃ have been shown to be interesting topological insulators with a single Dirac cone surface state and strong spin-orbit interaction.

Here, we present low-temperature transport measurements on structured ultra-thin 3nm-20nm Bi₂Se₃ flakes, such as Hall bars. The ultra-thin flakes have been prepared by exfoliation of bulk Bi₂Se₃ and are placed on SiO₂ on highly doped Si substrates. The final devices are structured with electron beam lithography followed by ion beam etching and contacted by Ti/Au electrodes. Low temperature ∼ 1,5K transport, i.e. conductance measurements have been carried out by driving back gate voltages from −70V to 70V and by varying magnetic fields up to 9T. We observe an ambipolar electric field effect and deduce a carrier mobility of around ∼ 3000 cm²/(Vs), and a carrier concentration of around ∼ 3· 10¹³ cm⁻².