Electrochemical Study of Bi2Se3 Single Crystals

Abstract

Bi2Se3 single crystals have attracted the attention of an extensive research community because of their many attractive properties: as a model topological insulator (TI), a layered structure and a promising platform for surface catalysis studies. However, despite often being studied under ultrahigh vacuum, there are very few studies of either the surface chemistry at ambient pressure or their electrochemistry. We have already demonstrated the protection and in-situ imaging and modification of bismuth chalcogenide single crystals in an electrochemical environment1,2. The present work shows that different choices of chalcogenide (Se in place of Te) and electrolyte yield differences in the oxidative dissolution process. We also investigate how the charge transfer resistance changes during electrochemical oxidation and reduction processes. Oxidative dissolution significantly increases the Bi2Se3 charge transfer resistance, measured by electrochemical impedance spectroscopy (EIS) using the ferrocyanide/ferricyanide redox couple. The charge transfer resistance only partially recovers during subsequent electrochemical reduction. As a further step in the electrochemical modification of bismuth chalcogenides, we studied metal electrodeposition. For example, we imaged Bi electrodeposition on a bismuth selenide single crystal in-situ for the first time, showing that it gives rise to characteristic triangular structures with kink-free step edges, the motion of which can be followed during island growth. The deposition is also highly reversible.