Berlin 2015 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 50: Topological insulators: Transport (with MA/O/TT)
HL 50.1: Talk
Wednesday, March 18, 2015, 11:45–12:00, ER 270
Surface Transport on a Bulk Topological Insulator — •Frederik Edler1, Lisa Kühnemund1, Marco Bianchi2, Ellen M.J. Hedegaard3, Martin Bremholm3, Bo B. Iversen3, Philip Hofmann2, and Christoph Tegenkamp1 — 1Inst. f. Festkörperphysik, Uni. Hannover — 2Dep. of Physics and Astronomy, Uni. Aarhus — 3CMC, Dep. of Chemistry and iNANO, Uni. Aarhus
Topological insulators are guaranteed to support metallic surface states on an insulating bulk, and one should thus expect that the electronic transport in these materials is dominated by the surfaces states. Alas, due to the high remaining bulk conductivity, surface contributions to transport have mainly only been singled out indirectly via quantum oscillations, or for devices based on gated and doped topological insulator thin films, a situation in which the surface carrier mobility could be limited by defect and interface scattering. This issue was first overcome for Bi2Te2Se where compensation of defects leads to low bulk conductivity and surface-dominated transport could directly be observed [1]. Here we present a direct measurement of surface-dominated conduction on atomically clean surfaces of Bi2Te3. Using a four tip STM for nano-scale four point transport measurements with variable contact distance we show that the transport at 30 K is again two-dimensional rather than three-dimensional. The sheet conductivity is 7.9(3)× 10−4 Ω−1 corresponding to a mobility of 505 cm2/Vs. Besides, results regarding the temperature dependence of the conductivity and the influence of structural defects, e.g steps, present after cleavage will be discussed. [1] Barreto et al., Nano Lett. 14, 3755 (2014)