Scanning Tunneling Microscopy of Gate Tunable Topological Insulator Bi2Se3 Thin Films

TL;DR

This study demonstrates gate-tunable topological insulator Bi2Se3 thin films using scanning tunneling microscopy, revealing significant Fermi level shifts and detailed electronic structure changes at low temperatures.

Contribution

First to combine in-situ molecular beam epitaxy growth with STM/STS for gate-tunable Bi2Se3 thin films on SrTiO3 substrates.

Findings

Fermi level shifted by 250 meV via gating

Detailed surface state dispersion observed

Band gap and electronic structure modulated by electric field

Abstract

Electrical field control of the carrier density of topological insulators (TI) has greatly expanded the possible practical use of these materials. However, the combination of low temperature local probe studies and a gate tunable TI device remains challenging. We have overcome this limitation by scanning tunneling microscopy and spectroscopy measurements on in-situ molecular beam epitaxy growth of Bi2Se3 films on SrTiO3 substrates with pre-patterned electrodes. Using this gating method, we are able to shift the Fermi level of the top surface states by 250 meV on a 3 nm thick Bi2Se3 device. We report field effect studies of the surface state dispersion, band gap, and electronic structure at the Fermi level.