Diffusion and mobility of interacting particles on stepped surfaces

We study the mobility and collective diffusion of mutually interacting adparticles on stepped surfaces through Monte Carlo simulations. We consider the case of nearest-neighbor repulsive interactions and different binding energies at the step edges in the disordered phase. We find that the coverage dependence of diffusion across the steps is sensitive to the adparticle interaction energy. For strong step binding, it is known that the corresponding collective diffusion coefficient Dx;cðhÞ has a maximum at a coverage of h 1⁄4 1=L for a given step spacing L. We show that this maximum moves to higher coverages with increasing repulsion, strongly enhancing diffusion. For weak step binding, these effects are even more pronounced. We also find that with a given adparticle repulsion, increasing the step binding energy slows down diffusion but does not change the overall coverage dependence of Dx;cðhÞ. Implications of these findings are briefly discussed. 2003 Elsevier B.V. All rights reserved.