Relative Stability of Thiolate and Selenolate SAMs on Ag(111) Substrate Studied by Static SIMS. Oscillation in Stability of Consecutive Chemical Bonds

The stability of chemical bonds at the molecule− metal interface is of fundamental importance for a majority of applications based on organic materials. It remains, however, extremely difficult to determine this stability using experimental and theoretical methods. A detailed analysis of the static SIMS (SSIMS) data obtained for the homologous series of thiolateand selenolate-based self-assembled monolayers (SAMs) on the Ag(111) substrate reveals positional oscillations in the stability of consecutive chemical bonds in the vicinity of the molecule− metal interface. The observed oscillations are much more pronounced compared to recently reported analogous data for the Au(111) substrate, which confirms the universal nature of this phenomenon and its strong dependence on the type of molecule binding atom (S or Se) and the substrate (Ag or Au). Importantly, such an analysis has not been conducted to date using any other technique, and this study not only reveals the universal mechanisms of molecule−metal interface stability but also presents S-SIMS as a unique tool for such an analysis.