Growth of High-Mobility Bi2Te2Se Nanoplatelets on hBN Sheets by van der Waals Epitaxy

TL;DR

This paper demonstrates that van der Waals epitaxial growth of Bi2Te2Se nanoplatelets on hBN substrates significantly enhances their structural quality and surface state mobility, enabling better electronic characterization of topological insulators.

Contribution

The study shows improved growth quality and mobility of Bi2Te2Se nanoplatelets on hBN, facilitating surface state analysis and Fermi level tuning, which was less effective on conventional substrates.

Findings

Surface state mobility increased by a factor of 3 on hBN

Observation of well-developed Shubnikov-de Haas oscillations

Fermi level tuning achieved via back gate

Abstract

The electrical detection of the surface states of topological insulators is strongly impeded by the interference of bulk conduction, which commonly arises due to pronounced doping associated with the formation of lattice defects. As exemplified by the topological insulator Bi2Te2Se, we show that via van der Waals epitaxial growth on thin hBN substrates the structural quality of such nanoplatelets can be substantially improved. The surface state carrier mobility of nanoplatelets on hBN is increased by a factor of about 3 compared to platelets on conventional Si/SiOx substrates, which enables the observation of well-developed Shubnikov-de Haas oscillations. We furthermore demonstrate the possibility to effectively tune the Fermi level position in the films with the aid of a back gate.