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

The morphology of islands grown on surfaces from soft-landed clusters has b een investigated by electron microscopy. Compact islands have been observed on amorphous carbon surfaces, whereas an evolution from compact to ramifie d 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 islan d morphologies observed, we propose a crude model involving a competition b etween the time for aggregated clusters to coalesce and the time interval b etween successive arrivals of clusters to grow the islands. It shows that t here 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 experime ntal results, we show how the morphology of the islands can be controlled b y the size of the incident clusters and the presence of surface defects. (C ) 1999 Elsevier Science B.V. All rights reserved.