Origin of Current Enhancement through a Ferrocenylundecanethiol Island Embedded in Alkanethiol SAMs by Using Electrochemical Potential Control

Electroactive ferrocenylundecanethiol islands embedded in an n-decanethiol SAM matrix were studied under potential control using in situ scanning tunneling microscopy (STM). Contrary to previous reports, the positive charges on ferrocene moieties are not a prerequisite to enhancing the current through ferrocenylundecanethiol on gold. Rather, conduction paths are opened at determined potentials for both neutral and monocationic ferrocene moieties. In addition, although stable and reproducible images were obtained under potential control, conventional STM measurements under N₂ atmosphere were sometimes unstable and irreversibly changed the sample, indicating that current measurements of ferrocenylundecanethiol are much easier under an electrochemical environment.