Dresden 2017 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 14: Poster: Two-Dimenaional Materials and Topological Insulators

HL 14.13: Poster

Monday, March 20, 2017, 14:00–18:00, P2-OG3

Optimization of MBE growth of topological insulator thin films and device fabrication — •Andrea Bliesener, Patrick Janoschka, Fan Yang, Alexey Taskin, and Yoichi Ando — Institute of Physics II, University of Cologne

Topological insulators (TIs) belong to a new class of quantum materials in which a strong spin-orbit coupling leads to a band inversion and, as a consequence, to a gapless metallic state on the surface. The realization of many exciting theoretical predictions about the surface transport properties depends greatly on the sample quality and, first of all, on achieving a negligible bulk conductivity. The MBE growth technique is among the best suited for this challenge. Furthermore to observe the novel quantum phenomena, fabrications of thin-film devices are required which allows for tuning the Fermi level across the Dirac point. Here we show the results of growth of a Bi_2−xSb_xTe₃ system, where the optimization of the composition between n-type Bi₂Te₃ and p-type Sb₂Te₃ can give almost perfect compensation. In combination with a greatly reduced bulk-to-surface ratio in the films, this approach allows to obtain TI samples where the surface transport is dominating. We also report a comprehensive method to fabricate a top-gated TI device consisting of a Bi_2−xSb_xTe₃ Hall-bar using photo-lithography and e-beam lithography together with other techniques. With this device we are able to demonstrate the tuning of the chemical potential.