Electrical resistance of individual defects at a topological insulator surface

TL;DR

This study investigates how various nanoscale defects on a topological insulator surface affect electrical resistance, revealing that domain boundaries significantly increase resistance while voids have a minor impact.

Contribution

It provides direct nanoscale measurements of defect-induced resistance variations on a topological insulator surface using scanning tunnelling potentiometry.

Findings

Domain boundaries cause the highest localized resistance.

Void defects have a relatively small impact on resistance.

Resistivity at domain boundaries is about four times higher than at step edges.

Abstract

Three-dimensional topological insulators host surface states with linear dispersion, which manifest as a Dirac cone. Nanoscale transport measurements provide direct access to the transport properties of the Dirac cone in real space and allow the detailed investigation of charge carrier scattering. Here, we use scanning tunnelling potentiometry to analyse the resistance of different kinds of defects at the surface of a (Bi0.53Sb0.47)2Te3 topological insulator thin film. The largest localized voltage drop we find to be located at domain boundaries in the topological insulator film, with a resistivity about four times higher than that of a step edge. Furthermore, we resolve resistivity dipoles located around nanoscale voids in the sample surface. The influence of such defects on the resistance of the topological surface state is analysed by means of a resistor network model. The effect resulting from the voids is found to be small compared to the other defects.