title: Unusual two-stage kinetics of ethylene adsorption on Si(100) unraveled by surface optical spectroscopy and Monte Carlo simulation.
abstract: The adsorption of ethylene on a Si(100)-2×1 surface in an ultrahigh vacuum has been monitored at room temperature by use of real-time surface differential reflectance spectroscopy, which clearly demonstrated that the adsorption follows a two-stage process. About half a monolayer is obtained for 1 L, while the second stage is much slower, yielding the complete monolayer for an exposure of ∼400  L. The kinetics over the full range has been successfully reproduced by a Monte Carlo calculation. The key point of this two-stage adsorption kinetic lies in the reduced adsorption probability (by a factor of several hundreds) on the Si dimers, neighbors of dimers which have already reacted, with respect to the adsorption probability on isolated dimers. This new kind of adsorption kinetics, due to a repulsion between already adsorbed molecules and additional molecules impinging on the surface, makes it a textbook case for a "cooperative" adsorption process.
authors.affiliation: Institut des NanoSciences de Paris, CNRS and UPMC University of Paris 06, UMR 7588, 4 place Jussieu, 75005 Paris, France and Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, University of Lorraine and CNRS, UMR 7564, 405, rue de Vandoeuvre, 54601 Villers-lès-Nancy, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Coustel
authors.forename: Yves
authors.initials: Y
authors.lastname: Borensztein
authors.forename: Olivier
authors.initials: O
authors.lastname: Pluchery
authors.forename: Nadine
authors.initials: N
authors.lastname: Witkowski
mesh_terms: D000327:Adsorption; D005030:Ethylenes / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D009010:Monte Carlo Method; D055095:Optics and Photonics / Q000379:methods; D012825:Silicon / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D005030:Ethylenes; C036216:ethylene; D012825:Silicon