Chemical Interactions\nat the Interface of Au on Bi<sub>2</sub>Se<sub>3</sub> Topological\nInsulator

This study explores the intricate chemical processes\nat the interface\nbetween the topological insulator Bi<sub>2</sub>Se<sub>3</sub> and\ndeposited Au. The study mainly focused on room-temperature interactions\nthat can cause the aging of, e.g., gold contacts on electronic devices\nbased on the topological insulators (TIs) or spintronic devices. Our\ninvestigation uncovers a complex mechanism involving redox reactions,\ndiffusion, and structural changes akin to the vapor–liquid–solid\nprocess. We observe the precipitation of metallic bismuth on the top\nof the Au layer and also a similar process, albeit at a slower rate,\ninvolving Se<sup>0</sup>. The resulting non-stoichiometry in the interfacial\nlayers is compensated with the formation of an intermetallic compound\nlow on Bi. As the temperature increases, Se diffusion intensifies,\nnow leading to a selenium deficiency at the interfacial region and\nsubsequent restructuring of the interface. These findings provide\nvaluable insights crucial for optimizing material design and device\nperformance, thereby guiding future research endeavors and technological\nadvancements in the field of devices based on TIs.