Monte Carlo studies of reactive desorption from mixed adlayers

Abstract

Reactive desorption of gas molecules from mixed adlayers containing two species is studied using a Monte Carlo simulation scheme. The effects of lateral interactions among adatoms, adsorbate islanding, surface diffusion and initial surface coverage on the desorption spectra are examined. Results show that for attractive lateral interactions, adsorbate islanding and surface diffusion lead to an increase in the activation energy, whereas for repulsive lateral interactions, the activation energy decreases. Results also indicate that a slowly decaying spectrum may be obtained when the mobile molecules do not interact with other adsorbed molecules due to a sustained diffusion and reaction process. An analysis of the effects of surface diffusion reveals that the desorption rate increases as the mobile species approaches equilibrium distribution. In addition, if lateral interactions enhance the concentration of mobile species near island boundaries, then the mobile species attains equilibrium distribution more rapidly.