Single layer gold islands at the interface between a self-assembled monolayer and the Au(111) substrate: A high-resolution STM study

Physical vapor deposition of gold onto a self-assembled monolayer (SAM) of octanethiol on Au(111) has been studied at the molecular level in ultra-high vacuum (UHV) using atomic-resolution scanning tunneling microscopy (STM). A specially prepared SAM with not only the usual etch pits but also co-existing phases and domain boundaries is used for the purpose of studying details of the nucleation process. Etch pits are found to be filled by deposited Au atoms. At the same time, preferential nucleation and growth of gold islands at intersections of different domains, as well as inside the domains of the less dense striped phase, is observed. We find no gold islands within the densely-packed (√3 × √3)R30° phase. High-resolution STM imaging shows that the SAM over the newly formed gold islands adopts the same structure as that in the immediate surroundings.