Spatial distribution of irradiation effects on silica glass induced by 15-MeV oxygen ion microbeam

Abstract

High-purity silica glass was irradiated by a focused 15-MeV O4+ microbeam with diameter of 1μm up to a fluence of 1.0×1014ions/cm2. Spatial distribution of irradiation effects by the O4+ microbeam on silica glass was investigated by optical microscopy, microphotoluminescence (PL)/Raman spectroscopy and atomic force microscopy (AFM). Distribution of refractive index change and defect formation was visualized by optical microscopy and PL mapping, indicating the structural changes of silica glass along the ion track up to the depth of 10μm. In addition, we observed deformed side surface with a groove by AFM along the track suggesting the internal compaction in silica glass. This is accompanied by increased threefold rings of SiO2 network detected by Raman scattering. We also discuss technological implications of these results on the applications of microbeam irradiation effects to the fabrication of microoptical elements.