Excited electron dynamics at ferrocene-terminated self-assembled monolayers on Au(1 1 1): Lengthened lifetime of image potential state

Ultraviolet photoemission spectroscopy (UPS) and two-photon photoemission (2PPE) spectroscopy have been employed to investigate the electronic states and the excited electron dynamics of ferrocene (Fc)-terminated self-assembled monolayers (SAMs) on Au(1 1 1). For the 11-ferrocenyl-1-undecanethiol (FcC11-) SAM, an image potential state (IPS) located at EF +3.8 eV was observed by time-resolved 2PPE. Its lifetime, 90 fs, was found to be much shorter than that of decanethiol (C10-) SAM, 11 ps. By forming the C10-SAM beforehand, the IPS lifetime for FcC11-&C10-SAM was lengthened to ∼9 ps; this can enable improvement in molecular ordering and substantial formation of C10 domains.