Radiation damage in vitreous fused silica induced by MeV ion implantation

Abstract

The nature of E′ 1 defects in vitreous fused silica induced by high energy (1–17 MeV) Cl and F ion implantation in terms of ion fluence, ion energy, saturation behavior and annealing feature, has been studied and compared with results obtained after 2 MeV proton and 0.633 MeV γ-ray irradiation using the electron spin resonance (ESR) method. The ESR spectra of E′ 1 defects created by γ-ray, proton, and MeV ion (at low ion fluence) irradiation are similar, with a mean g factor of 2.0005 ± 0.0004. For MeV heavy ion implantation the density of E′ 1 defects reaches a maximum at a deposited energy density of the order of 10 21 keV cm, and the average yield of E′ 1 defects per unit energy increases with increasing ion mass and decreasing ion energy for a given ion fluence. The influence of ion flux on defect creation as seen in low-energy heavy ion implanted crystal GaAs was not observed. The E′ 1 defects caused by either γ-ray or MeV heavy ion irradiation anneal at a unique stage and bleach at temperatures above 450°C. The annealing feature is dependent on the ion fluence. For 2 MeV proton implantation, the E′ 1 defects decay more slowly and beaach at temperatures above 600°C. The surface cracking produced by MeV heavy-ion implantation has been observed. The crack density increases with ion fluence, reaches a maximum, and then declines. The cracks close up for subsequent higher ion fluences. No surface cracks were seen for 2 MeV proton implantation in the ion fluence range of 1 × 10 14 to 2 × 10 17 protons cm −2.