Materials Science

Films from Clusters

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Science  13 Oct 2006:
Vol. 314, Issue 5797, pp. 224
DOI: 10.1126/science.314.5797.224c

In the “atom by atom” growth mode of inorganic films, strain induced by the substrate can largely control the final morphology, dictating outcomes ranging from a smooth film to island formation. Carlier et al. have explored the consequences of delivering material to a surface as clusters rather than individual atoms. Beams of antimony clusters were tuned to peak at different average sizes—either 88 atoms (Sb88) or 300 atoms (Sb300)—and then directed toward a graphite surface. Both types of cluster formed fractal structures on this weakly interacting substrate, but when they were deposited sequentially, distinct morphologies resulted depending on the order of addition. The large clusters, if added second, filled in the center of an Sb88 fractal network. In contrast, the small clusters filled out the ends of a preformed Sb300 network. In the latter case, further deposition of the small clusters created instability, causing the initially thick end groups to flatten out and spread along the graphite in two dimensions. The authors suggest that this transition is triggered because the strain accumulating in the compact end groups eventually exceeds the surface energy cost of producing a flatter but more crystalline structure. — PDS

Nano Lett. 6, 1875 (2006).

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