The theory of atomic desorption within the harmonic approximation

Abstract

A formal extension of earlier one-dimensional theories is given for models in which the gas-surface interaction potential can be taken to be of the cut-off harmonic form. The rate equation for finite-temperature surfaces is given in one and three dimensions for the case where the adsorbed atom interacts with a single active site. It is shown that for any harmonic substrate, the three-dimensional rate equation is a function only of the physical parameters of the adatom-active site pair. The pre-exponential factor derived in three dimensions is a function of both the temperature of the surface and the desorption energy. The angular intensity distribution of the desorbed flux is shown to be predominantly cosine-like for this model. Reasonable values are obtained for the potential parameters obtained by fitting the rate equation to experimental data for the Ga-GaAs system.