CLUSTERING ACROSS CONCENTRATION GRADIENTS

Clustering experiments on surfaces are of fundamental interest to verify theoretical concepts for phase-separation processes such as statistical self-similarity and scaling behaviour. Unfortunately, often the differences between theoretical models are too small to be studied with standard sample preparation techniques, as experimental uncertainties result in variations in the results of the same order of magnitude as the effects that we want to study. In this paper we study a modified approach where two different initial morphologies are prepared on the same surface so that the dynamic processes occur in parallel under identical conditions. From observations of clustering near the concentration step we find that the material transfer during late stage ripening is limited to within a distance that is less than the diffusion length. This result is in agreement with a theoretical model that predicts that the interface is confined to a width of the order of the cluster-cluster distance. The two sides beyond this length evolve independently.