Growth mechanism of gold particles on Al2O3 substrates

We investigated the growth of small gold particles on thin alumina substrates obtained by oxidation of aluminum. The particles were vapor deposited in vacuum from a Knudsen cell source with a vapor rate of 1·10¹³ cm^?2·s^?1. In our experiments small Au particles on Al₂O₃ were examined by electron microscopy. From electron micrographs we draw a size histogram of Au particles depending on the mean deposit thickness and the deposition rate. For a mean thickness larger than 1.5 nm the particle size distributions show two peaks. The shapes and the positions of these two peaks allow us to determine the particle growth mechanism and to evidence the importance of the liquid-like coalescence resulting of diffusion and collision of the aggregates.