Thiol Terminated 1,4-Benzenedimethanethiol Self-Assembled Monolayers on Au(111) and InP(110) from Vapor Phase

We present results of a clean vacuum evaporative adsorption method of assembly of the conjugated dithiol molecule 1,4-benzenedimethanethiol on the surfaces of gold and indium phosphide. Measurements of direct recoil spectroscopy with time-of-flight analysis show in both cases formation of a self-assembled monolayer (SAM) with S atoms available at the SAM-vacuum interface. Investigation of the adsorption kinetics shows that a lying-down phase is formed at low exposures, which precedes the standing up SAM phase. The standing up SAM formation requires exposures of the order of a mega Langmuir. A study of the SAM stability with temperature shows that the S terminated layer survives up to ∼370 K, above this temperature a reordering of the layer takes place where S atoms are no longer available at the vacuum interface. Final desorption occurs around 450 K for Au and around 500K for InP.