Sticking, Desorption, Condensation and Evaporation
In this chapter we consider the simplest surface reactions: either a particle is in a dilute gas and reacts with the surface of a solid or liquid phase, or it is in a dilute solution and reacts with a solid surface. If, after the reaction, the particle stays on the surface for a time τ res (the residence time) long compared to microscopic time scales, one calls this process sticking or adsorption if surface and particle are different substances, and condensation if the substances are the same. In the first case one deals with a chemical reaction, in the second with a phase transition. The chemical reaction, however, is of a special kind. For instance, the stoichiometric coefficients have no precise meaning. Furthermore, there are gradual transitions between both processes in molecular beam epitaxy, when gradually more and more layers of one substance are grown on another. Since the physical mechanism of all these processes is the same, one should treat them on the same footing. This is what we are going to do. The corresponding inverse processes are adsorption and sublimation or evaporation.
KeywordsPartition Function Molecular Beam Epitaxy Desorption Rate Stoichiometric Coefficient Precise Meaning
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