Hydrogenation effects on the structural and optical properties of Si+-implanted fused silica

When excited with 250 nm (5 eV) radiation, Si+-implanted silica layers exhibit defect-related photoluminescence (PL) in the ultraviolet (4.3 eV) and violet–blue (3.2 and 2.7 eV) spectral ranges, well known as α, β, and γ PL bands of oxygen-deficient centers, respectively. The γ-band, relatively weak, is found at higher implant doses. Annealing at 1000°C affect both the absolute and relative intensities of the α- and β-bands. Subsequent hydrogenation at 500°C has a greater effect on the β/α value, which is thought to result from the creation or modification of defect by H. The as-implanted samples produce an electron spin resonance (ESR) signal with g values proportional to dose. For doses greater than 3×1017 cm−2, the ESR signal is resolved into two broad lines. These paramagnetic defects and the γ-band disappear by annealing and do not recover by hydrogenation. Hydrogenation also results in a shift of the Raman line to larger wave numbers meaning an improvement of crystallinity or stress change in the sample. The dose dependence of Raman peak combined with asymmetric broadening of the ESR signal suggests that the stress onto Si crystallites increases with increasing implant dose.