AVS 49th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP24
MCS and KMCS of Adsorption Probabilities: The Auto-catalytic Adsorption Phenomenon

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Surface Science Poster Session
Presenter: U. Burghaus, Ruhr-University of Bochum, Germany
Authors: J. Stephan, University of Potsdam, Germany
U. Burghaus, Ruhr-University of Bochum, Germany
Correspondent: Click to Email
An increase in the coverage, @THETA@, dependent adsorption probability, S(@THETA@), with increasing coverage, i.e. an auto-catalytic adsorption phenomenon which is called for now adsorbate-assisted adsorption, has frequently been observed for the adsorption of prototype molecules on quite different surfaces. However, the effect has rarely been addressed theoretically. We present a steady-state Monte Carlo (MCS) version of the modified Kisliuk model which is consistent with the energy, E@sub i@, dependence of the phenomenon and includes the effect of surface defects on S(@THETA@). Although steady-state MCS lead already to a better understanding of the microscopic scenario than analytical models, the influence of the adsorption temperature, T@sub s@, on S(@THETA@) can in principle not be studied. We therefore present additionally first results of a time-dependent (kinetic) Monte Carlo simulation scheme (KMCS) which can account in principle also for the T@sub s@ dependence of S(@THETA@). The MCS schemes are tested for different adsorption scenarios (such as the Kisliuk and Langmuirian dynamics) and especially for the auto-catalytic adsorption. Furthermore, a comparison of the simulations with experimental data for CO adsorption on both polar (O- or Zn-terminated) ZnO surfaces [Th. Becker, et al., JCP 113 (2000) 6334] will be shown. Although the scheme can be applied to other adsorption systems, the polar surfaces of ZnO are a perfect test system for the algorithm which is mainly based on the differences in the mass-mismatch of the adsorbate (CO) and the surface atoms (O or Zn).