Dynamic Behavior of Au Surfaces
Cynthia M. Friend
The Au-S interaction is very important in several technologies such as Au ore formation and controls the structure and stability self-assembled-monolayers (SAMs) used in soft lithography to write small features on a surface. We have demonstrated that the Au(111) surface is very dynamic when it interacts with sulfur. Sulfur induces lateral expansion of the surface which ultimately leads to ejection of Au from the surface and incorporation of Au atoms into a growing two-dimensional AuS phase. These results suggest that the smallest size scale and the definition of features made with soft lithography, which relies on S binding to Au, will be limited by the dynamic behavior of Au.
Dynamics of the formation of a 2D AuS overlayer captured by real-time imaging using scanning tunnelling microscopy during continuous SO2 exposure at room temperature to make a Au-S layer. (A) Au(111) partly covered with sulfur (B) Early stage of S-induced corrosion/etching of the Au(111) surface. Dark areas (emphasized in the close-up) correspond to pits in the surface that are one atom deep. Simultaneously small AuS clusters appear on flat regions of the surface. (C) The number of both pits and AuS clusters increases as the amount of S on the surface increases. (D) The reaction is completed once the surface is covered with a sponge-like gold sulfide overlayer.