Simulations of ripple formation on ion-bombarded solid surfaces

Ripple formation on amorphous carbon surfaces bombarded by 5 keV Ar ions is studied by atomistic simulations. Sputtering is treated in detail by simulating the entire collision cascades originated by the bombarding Ar ions. Surface relaxation is described by a Wolf-Villain-type discrete model. Ripples and wavelike patterns are observed to emerge on the surface. The ripples have a well-defined wavelength and the orientation of the wave crests changes from normal to parallel to the beam, when the angle of incidence is increased from 30 degrees to 60 degrees, respectively. The wavelength is found to depend on the magnitude of the diffusion and orientation of the beam as predicted by the continuum theories.