The effect of low energy irradiation, where the sputtering is imperceptible, has not been deeply studied in the pattern formation. In this work, we want to address this question by analyzing the nanoscale topography formation on Si surface, which is irradiated at room temperature by Ar + ions near the displacement threshold energy, for incidence angles ranging from 0 to 85 •. The transition from smooth to ripple patterned surface, i.e. the stability/instability bifurcation angle is observed at 55 • , whereas the ripples with their wave-vector is parallel to the ion beam projection in the angular window of 60-70 • , and with 90 • rotation with respect to the ion beam projection at the grazing angles of incidence. A similar irradiation setup has been simulated by means of molecular dynamics, which made it possible, firstly, to quantify the effect of the irradiation in terms of erosion and redistribution using sequential irradiation and, secondly, to evaluate the ripple wavelength using the crater function formalism. The ripple formation results can be solely attributed to the mass redistribution based mechanism, as erosion due to ion sputtering near or above the threshold energy is practically negligible.

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We demonstrate that surface ripples with an exceptionally high degree of order can develop when germanium is bombarded with a broad beam of gold ions. In contrast, if silicon is sputtered with an Au− beam, patches of ripples with two distinct wave vectors can emerge. These types of order can be understood if the coupling between the surface morphology and composition is taken into account.

We have observed the formation of ripples in a number of thin metal films, e.g. Au, Pt, Ag, Cu and Co under Ar^{+} ion beam sputtering at grazing incidence. The structures are found to be quite stable under ambient conditions. The results show that the ripple formation in polycrystalline metallic films relies on the erosion-induced surface instability similar to that in amorphous materials.Comment: 8 pages, 1 fig file containing 4 figure

Thin films of silver nanoclusters deposited on Si substrates are studied using scanning electron microscopy along with energy dispersive x-ray spectrometry. The nanoclusters are produced by dc magnetron sputtering followed by gas aggregation in a dense buffer gas. The film deposition is performed in a low impact energy regime with mass (size) selected clusters. These clusters were treated with rapid thermal annealing that gives an idea about the melting and evaporation mechanism of silver nanoclusters. Subsequent annealing of the grown silver film allows one to analyse the structure of the film and the character of its evolution. At room temperature, deposited clusters are distributed randomly, and annealing of the film leads to joining of clusters–monomers in non-compact clusters. At high temperatures, evaporation of clusters takes place. Parameters of the processes under consideration are estimated.