No abstract

120 keV carbon ions implantations at high fluences (0.5–8×1017 ions cm−2) were performed at elevated temperature (⩾500 °C) in silver layers deposited on various substrates (Si (100), 304 L stainless steel, and pure fused silica). Spherical carbon onions (3–15 nm in diameter) were so produced in the silver layers. A pure carbon onion thin film deposited on the substrate was obtained after annealing in vacuum. Atomic force microscopy and high-resolution transmission electron microscopy experiments were performed to characterize the structure of the thin films. Optical transmittance spectra of carbon onion layers deposited onto silica substrates revealed two absorption peaks centered at 220–230 nm and at 265 nm that were attributed to the presence of carbon onions and residual disordered graphitic carbon, respectively. Tribological experiments performed on silver–carbon onions composite thin films revealed that the friction coefficient is close to that of a pure silver film (0.2) but with much better wear behavior.

Gold clusters have been deposited by a monoenergetic, mass-selected ion beam with low energies (20–350eV) 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 1nm as the ion energy increases. We can also note that the size distribution becomes broader. For impact energies below 100eV, 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 350eV, the cluster size drastically drops below 5nm. 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.