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Structure of a CH3S monolayer on Au(111) solved by the interplay between molecular dynamics calculations and diffraction measurements

Mazzarello, R.
Cossaro, A.
Verdini, A.
Rousseau, R.
Casalis, L.
Danışman, Mehmet Fatih
Floreano, L.
Scandolo, S.
Morgante, A.
Scoles, G.
We have investigated the controversy surrounding the (root 3x root 3)R30 degrees structure of self-assembled monolayers of methylthiolate on Au(111) by first principles molecular dynamics simulations, energy and angle resolved photoelectron diffraction, and grazing incidence x-ray diffraction. Our simulations find a dynamic equilibrium between bridge site adsorption and a novel structure where 2 CH3S radicals are bound to an Au adatom that has been lifted from the gold substrate. As a result, the interface is characterized by a large atomic roughness with both adatoms and vacancies. This result is confirmed by extensive photoelectron and grazing incidence x-ray diffraction measurements.