Chemical Interactions at the Interface of Au on Bi₂Se₃ Topological Insulator

This study explores the intricate chemical processes at the interface between the topological insulator Bi₂Se₃ and deposited Au. The study mainly focused on room-temperature interactions that can cause the aging of, e.g., gold contacts on electronic devices based on the topological insulators (TIs) or spintronic devices. Our investigation uncovers a complex mechanism involving redox reactions, diffusion, and structural changes akin to the vapor-liquid-solid process. We observe the precipitation of metallic bismuth on the top of the Au layer and also a similar process, albeit at a slower rate, involving Se⁰. The resulting non-stoichiometry in the interfacial layers is compensated with the formation of an intermetallic compound low on Bi. As the temperature increases, Se diffusion intensifies, now leading to a selenium deficiency at the interfacial region and subsequent restructuring of the interface. These findings provide valuable insights crucial for optimizing material design and device performance, thereby guiding future research endeavors and technological advancements in the field of devices based on TIs.