Morphology control of the supported islands grown from soft-landed clusters

The morphology of islands grown on surfaces from soft-landed clusters has been investigated by electron microscopy. Compact islands have been observed on amorphous carbon surfaces, whereas an evolution from compact to ramified shapes occurs on graphite surfaces as the mean size of deposited clusters increases. Moreover, by increasing the surface defect density on graphite, a continuous variation of the island morphology is observed, from extended ramified shapes to small compact shapes. In order to account for the island morphologies observed, we propose a crude model involving a competition between the time for aggregated clusters to coalesce and the time interval between successive arrivals of clusters to grow the islands. It shows that there exists a critical island size R-o dividing island shapes into compact shapes for R<R-o and into ramified shapes for R>R-o. This critical size R-o varies as a function of the incident cluster size. Relying on our experimental results, we show how the morphology of the islands can be controlled by the size of the incident clusters and the presence of surface defects. (C) 1999 Elsevier Science B.V. All rights reserved.