Is Sputtering Relevant For Ion-Induced Self-Organized Pattern Formation?

Recently it was reported that ion-induced mass redistribution rather than sputtering would solely determine ripple pattern formation of ion-irradiated surfaces. We investigate the pattern formation on Si irradiated with Xe ions with energies of 5 and 10 keV. Sputter yield and collision cascade characteristics vary strongly as function of ion energy, ion mass and substrate material and allow us to investigate the contributions of curvature dependent erosion as well as mass redistribution. The experimental results are compared with calculations of the curvature coefficients S-x and S-y. Parameters required for the calculations are extracted from Monte Carlo simulations with program SDTrimSP. The calculated curvature coefficients show that mass redistribution is dominant for parallel ripple formation in most cases. The angle where the pattern orientation changes from parallel to perpendicular ripples is however related to curvature dependent sputtering. We discuss the possibilities to tune the different contributions to pattern formation and examine the possibility to completely eliminate mass redistribution effects.