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. We find the largest localized voltage drop 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 with the other defects.
Highlights
Three-dimensional topological insulators host surface states with linear dispersion, which manifest as a Dirac cone
We used the same sample for scanning tunnelling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES) measurements, which was kept under ultra high vacuum (UHV) conditions at all times to avoid any contamination of the topological insulators (TIs) surface throughout the measurements
This means that the terrace conductivity, which contributes to 56% of the total resistance of the surface channel, is dominated by phonon scattering and scattering at defects, which are smaller than the defects we report here, such as atomic vacancies or anti-site defects[5,13]
Summary
Three-dimensional topological insulators host surface states with linear dispersion, which manifest as a Dirac cone. 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. We use a combination of in situ surface analysis tools, angle-resolved photoemission spectroscopy (ARPES) and four-tip scanning tunnelling microscopy (STM), to achieve a detailed electronic and charge transport analysis of pristine (Bi0.53Sb0.47)2Te3 thin films, respectively. For this compound, it has recently been shown that it has low bulk conductivity, whereas on its surface the Fermi energy cuts only through the TSS10–13. The resistance due to nanoscale voids in the TI surface is miniscule compared with these defects
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