Creation of multiple nanodots by single ions

In the challenging search for tools that are able to modify surfaces on the nanometer scale, heavy ions with energies of several 10 MeV are becoming more and more attractive. In contrast to slow ions where nuclear stopping is important and the energy is dissipated into a large volume in the crystal, in the high energy regime the stopping is due to electronic excitations only. Because of the extremely local (< 1 nm) energy deposition with densities of up to 10E19 W/cm^2, nanoscaled hillocks can be created under normal incidence. Usually, each nanodot is due to the impact of a single ion and the dots are randomly distributed. We demonstrate that multiple periodically spaced dots separated by a few 10 nanometers can be created by a single ion if the sample is irradiated under grazing angles of incidence. By varying this angle the number of dots can be controlled.Comment: 12 pages, 6 figure

Molecular dynamics simulations of non-equilibrium systems

Peer reviewe

Effect of stress on track formation in amorphous iron boron alloy : ion tracks as elastic inclusions

In a recently developed model of ion beam induced plastic deformation of amorphous solids, ion tracks are described as cylindrical thermoelastic inclusions formed upon local heating and shear stress relaxation along the ion trajectories. According to this model, track formation call be influenced or even suppressed by an applied stress. This model prediction is tested by studying the influence of stress on the etching of tracks of 2.4 GeV Pb in foil samples of the glassy metal Fe81B13.5Si3.5C2, where a compressive in-plane stress was built up in limited zones by preirradiation with a high fluence of 200 MeV Xe ions. The variation of the size of the observed etch pits with the local stress is found to be consistent with the model predictions, thus confirming the thermal spike origin of the tracks