Evolution of ion-induced ripple patterns on SiO2 surfaces

The evolution of nanoscale ripple patterns during sub-keV ion sputtering of thermally grown, fused, and single crystalline SiO2 surfaces has been investigated by means of atomic force microscopy. For all three materials, different dependencies of the ripple wavelength and the surface roughness on the ion fluence have been found. Within the Bradley-Harper model of pattern formation, the observed differences are consistent with different amounts of surface and near-surface mass transport by ion-enhanced viscous flow which might result from different surface energies of the SiO2 specimens.