The morphology of amorphous SiO2 surfaces during low energy ion sputtering

Abstract

The morphology of different amorphous or amorphizedSiO2 surfaces, including thermally grown films, fused silica, and single crystalline quartz, duringlow energy ion sputtering has been investigated by means of atomic force microscopy. Forall three materials, the formation of periodic ripple patterns oriented normal to the direction ofthe ion beam is observed at intermediate incident angles. At near-normal incidence, theSiO2 surfaces remain flat, whereas a rotation of the ripple patterns is observed at grazing incidence.At intermediate angles, the patterns on the different surfaces exhibit wavelength coarseningof different strengths, which can be attributed to different amounts of near-surface masstransport by the surface-confined ion-enhanced viscous flow. In the framework of the recenthydrodynamic model of ion erosion, the observed differences in ripple coarsening are consistentwith this interpretation and indicate that the surface energies of thermally grownSiO2 and amorphized quartz are lower and higher than that of fused silica, respectively.