Freiburg 2019 – scientific programme

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FM: Fall Meeting

FM 63: Poster: Enabling Technologies: Quantum Materials, Quantum Dots, Quantum Wires, Point Contacts and Superconducting Systems

FM 63.20: Poster

Wednesday, September 25, 2019, 16:30–18:30, Tents

VLS-Growth and characterization of bulk-insulating topological insulator nanowires — •Felix Münning¹, Oliver Breunig¹, Zhiwei Wang¹, Mengmeng Bai¹, Stefan Roitsch², Klaus Meerholz², Thomas Fischer³, Sanjay Mathur³, and Yoichi Ando¹ — ¹Physics Institute II, University of Cologne — ²Institute of Physical Chemistry, University of Cologne — ³Institute of Inorganic Chemistry, University of Cologne, Germany

We report on the growth of Bi_xSb_2−xTe₃ and Bi₂Te_xSe_3−x nanowires and their characterizations in terms of morphology, material composition and electronic transport at low temperatures. Growth is performed using the vapour-liquid-solid (VLS) method on Si/SiO₂ substrates decorated with 20-nm Au nanoparticles and devices featuring ohmic contacts to the nanowires are fabricated using electron-beam lithography.

Bi_xSb_2−xTe₃ nanowires were successfully grown in a bulk-insulating composition, with the chemical potential tunable through the Dirac point by electrostatic gating. While in Bi₂Te_xSe_3−x the charge-neutrality point could not be reached, the transport appears to be cleaner, featuring AB-like oscillations over a wide range of the chemical potential within the band-gap.

The observed signatures of the topological surface states are modeled on the basis of their size-quantized sub-bands within the insulating band-gap.