MOBILITY AND AGGREGATION OF FREE CLUSTERS SOFT LANDED ON AMORPHOUS AND CRYSTALLINE CARBON SUBSTRATES

Neutral antimony clusters produced by a gas aggregation source have be en deposited at room temperature on thin films of amorphous carbon and cleavage surfaces (0001) of graphite. Antimony islands generated from different mean size distributions of preformed clusters Sb-n(n = 4, 9 0, 150, 250, 600; 2000) have been investigated by transmission electro n microscopy. Only compact islands have been observed on amorphous car bon, whereas an evolution from compact to dendritic shapes occurs on g raphite substrate as the mean size of the deposited clusters increases . For clusters containing more than 150 atoms the dendritic islands ex hibit a fractal character whose dimensional analysis yields a fractal dimension of 1.63 +/- 0.07. The different models for island growth are discussed in the light of these results.