Regensburg 2019 – scientific programme

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O: Fachverband Oberflächenphysik

O 96: Focus Session: Surface Transport at the Atomic Scale

O 96.6: Talk

Friday, April 5, 2019, 12:15–12:30, H15

Parallel conduction channels in topological insulator thin films: Role of the interface layer and the band bending in the film — •Sven Just^2,3, Felix Lüpke⁴, Stefan Korte¹, Vasily Cherepanov¹, Frank Stefan Tautz¹, and Bert Voigtländer¹ — ¹Peter Grünberg Institute (PGI-3) and JARA-FIT, Forschungszentrum Jülich, Germany — ²II. Physikalisches Institut B, RWTH Aachen, Germany — ³Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Germany — ⁴Departement of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA

Topological insulator (TI) thin films can exhibit multiple parallel channels for current transport: beside the topological surface states (TSS), e.g. the interior of the TI film, the interface layer and the substrate. A crucial task is to minimize the influence of the parasitic channels for taking advantage of the TSS properties. We present a method for determining the conductivity of the interface between substrate and TI film by distance-dependent surface-sensitive four-probe measurements with a multi-tip STM. Moreover, as the conductivity of the interior of the TI thin film (bulk) is difficult to access by measurements, we propose here an approach for calculating the near-surface band bending and the mobile charge carrier density inside the TI thin film based on data from surface-sensitive measurements, e.g. (gate-dependent) four-point resistance measurements and ARPES. It turns out that in the thin-film limit the band-bending is largely independent on the dopant concentration of the film, which allows to estimate the total mobile charge carrier density and the conductivity of the TI thin film.