Vacancy generation at steps and the kinetics of surface alloy formation

The role of step fluctuations in surface reactions is explored. Activation energies for various processes relevant to the production of vacancies at steps on the Cu(100) surface are calculated in the second-moment approximation of the tight-binding scheme. Productions rates for vacancies are calculated analytically and by means of Monte Carlo simulations. For the specific system of manganese incorporation into the Cu(100) surface, it is shown that manganese is effectively incorporated at step edges due to the step fluctuations. The migration of the incorporated manganese away from the steps is mediated by the vacancies produced at the steps. Comparison to recent experimental results on the incorporation pattern on differently oriented steps suggests that exchange processes at steps may also play a role in surface alloy formation.