Metallic Contact Formation for Molecular Electronics: Interactions Between Vapor-Deposited Metal (Au, Al and Ti) and Self-Assembled Monolayers of Conjugated Mono- and Dithiols

We present grazing incidence FTIR data of Au, Al, and Ti vapor-deposited onto self-assembled monolayers (SAMs) of conjugated mono- and dithiols. SAMs of 4,4'''-dimercapto-p-quarterphenyl, 4.4''-dimercapto-p-terphenyl, and 4,4'-dimercapto-p-biphenyl have reactive thiols at the SAM/vacuum interface that interact with vapor-deposited Au or Al atoms, preventing metal penetration. Conjugated monothiols lack such metal blocking groups and metals (Au,Al) can penetrate into their SAMs. Vapor deposition of Ti onto conjugated mono- and dithiol SAMs and onto hexadecanethiol SAMs destroys the monolayers.