Clustering on surfaces at finite areal coverages

Clustering is a phase separation process often observed in growth on surfaces and of technological relevance in heteroepitaxy. Cluster size distributions for three-dimensional cluster ripening on surfaces has been studied to test predictions for the dependence of ripening on finite areal cluster fractions. We show that the distribution broaden relative to the mean field model and also exceed the increase in width predicted in simulations for three-dimensional systems caused by the interaction between neighboring clusters. The observed data are in significant disagreement with the model and the simulations in respect of the skewness of the cluster size distributions which can be associated with unexpectedly intensive coalescence effects even at areal coverages as low as 10%.