Structural rearrangement of c(70) monolayers induced by octanethiol adsorption

Mixed monolayers of C70 and octanethiol are prepared on Au(111) by a sequential adsorption method. A partial C70 monolayer is first formed and characterized, followed by the vapor deposition of octanethiol. This results in a well-ordered alkanethiol film where single C70 molecules and small molecular clusters are located at domain boundaries and in disordered regions. Substrate step defects have a large influence on the spatial distribution of C70; adjacent to a substrate defect, C70 binds preferentially on the upper terrace and is depleted on the lower terrace. We explain these observations as resulting from the kinetics of alkanethiol monolayer formation, and we present a simple model for the evolution of surface structure in the C70/octanethiol system.