Understanding of surface morphology evolution induced by ion erosion is still limited. Continuum models cannot explain microscopic processes. On the other hand, so far atomistic simulations could not describe pattern evolution on experimental spatiotemporal scales. Therefore, recently continuum equations were feeded with MD simulation results, which allows the understanding of smoothing mechanisms like an effective mass ‘downhill’ current induced by ballistic drift.

We developed a novel program package which unifies the collision cascade with kinetic Monte-Carlo simulations. This allows a fully atomistic description on experimental spatiotemporal scales.  3D atom relocations were calculated using the binary collision approximation, whereas the thermally activated relaxation as well as diffusive processes were simulated by a bit-coded kinetic 3D Monte Carlo program. Effects like ballistic mass drift or dependence of local morphology on sputtering yield are automatically included by this approach.

The mechanism of ripple formation induced by a local surface currents is studied. The quantitative description of current vectors for different environmental parameters, and initial surface condition of sinusoidal structure, can be analized in time and space, following the local atomic drift. Different driving forces can be distinguished. Without ion irradiation the mass current vectors are always parallel to the surface plane with down-hill direction. Collision-cascade-induced defects change the mass currents significantly. Up-hill currents induce self-organization for certain obligue ion incidence angles. This driving forces causes patterning even without sputtering events.