Roughness study of ion-irradiated silica glass surface

We have investigated the surface roughness of ion-irradiated silica glass by the use of atomic force microscopy (AFM). Highly polished synthetic silica glass was irradiated with 120 keV Ar+ ion at a dose range of1 × 1012−1 × 1017ions/cm2. The surface roughens progressively at an ion dose up to1 × 1014ions/cm2, whereas smoothing occurs at an ion dose above1 × 1014ions/cm2. The smoothing in the high dose region is attributed to the viscous relaxation induced by ion beam. As to roughening in the low dose region, two mechanisms both sputtering and compaction has been discussed. The roughening is thought of the compaction of the partial region in which each of the ion impacts cause structural changes.