Gold nanoclusters on amorphous carbon synthesized by ion-beam deposition

Gold clusters have been deposited by a monoenergetic, mass-selected ion beam with low energies (20-350 eV) on amorphous carbon substrates in order to minimize the influence of the surface crystallinity and the ion-induced structural changes. Gold has been used as a model system, due to the poor reactivity with carbon, to study the ion-energy dependence, the temporal evolution, and the influence of the temperature on the cluster distribution. The cluster size is very sensitive to the energy and the mean size strongly decreases from 4 to less than 1 nm as the ion energy increases. We can also note that the size distribution becomes broader. For impact energies below 100 eV, surface processes dominate the cluster nucleation and growth. If higher energies are used, an increasing number of ions is implanted below the surface and different processes control the cluster formation. When the energy increases above 350 eV, the cluster size drastically drops below 5 nm. The samples are analyzed with different methods such as atomic force microscopy, transmission electron microscopy, and x-ray photoelectron spectroscopy to determine their size distribution, composition, and structure. (c) 2005 American Institute of Physics.