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

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2007-01-05
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.