Functionalizing noble metal surfaces with (bio)organic molecules is a vibrant field of research, with key applications in medicine, catalysis, and molecular electronics. Control over the molecular self-assembly is essential to creating functional devices. Here, we exploit our high-pressure, high-temperature scanning tunneling microscope (STM) to relate the effects of controllable parameters (temperature and pressure) to atomic-scale assembly mechanisms. Using methanethiol self-assembly on Au(111) as a model system, we monitor the formation and assembly of the ubiquitous (CH3S)2Au “staple” motif into row structures at pressures of up to 1 bar. We observe a pressure-induced transition from the usual 1/3 monolayer (ML) saturation coverage in vacuum to 3/8 ML at 1 bar, thus providing the first evidence for a pressure gap effect for thiol adsorption. Complementing our experiments, we employed dispersion-corrected density functional theory computations to model the formed surface adlayers, corresponding STM images, and underlying equilibrium thermodynamics.

Additional Metadata
Publisher ACS
Funder I.M.N. Groot (Irene)
Persistent URL
Journal J. Phys. Chem. C
Mom, R.V, Melissen, S.T.A.G, Sautet, P, Frenken, J.W.M, & Steinmann, S.N. (2019). The Pressure Gap for Thiols: Methanethiol Self-Assembly on Au(111) from Vacuum to 1 bar. J. Phys. Chem. C, 123(19), 12382–12389. doi:10.1021/acs.jpcc.9b03045