Creation of glass-characteristic point defects in crystalline SiO2 by 2.5 MeV electrons and by fast neutrons

Abstract

Point defects in crystalline SiO2, created by 2.5 MeV electron irradiation at dose below the amorphization threshold or by fast neutrons, were compared by luminescence spectroscopy. Oxygen dangling bonds ("non-bridging oxygen hole centers", NBOHCs), peculiar to amorphous state of SiO2, were detected for the first time in electron-irradiated non-amorphized αquartz crystal. Their presence may signal the formation of nucleation centers in crystal structure as the first step to radiationinduced amorphization. Compared to crystal, irradiated by 10 19 cm −2 fast neutrons, their concentration was over 100 times lower, and their inhomogeneous broadening was at least 2.5 times smaller. Divalent silicons ("silicon oxygen deficiency centers", SiODC(II)), inherent to oxygen-deficient or irradiated SiO2 glass, were detected in neutron-irradiated (10 19 n/cm 2) α-quartz but were not found after the electron irradiation. Radiation-induced interstitial O2 molecules, characteristic to irradiated glassy SiO2 and other oxide glasses, are found in α-quartz only after neutron irradiation. The oxygen atoms, displaced by the 2.5 MeV e − irradiation of α-quartz for fluences up to 10 19 e − /cm 2 evidently stays entirely in the peroxy linkage (Si-O-O-Si bond) form.

Unusual Luminescence of Quartz from La Sassa, Tuscany: Insights on the Crystal and Defect Nanostructure of Quartz Further Developments

“…In the light of the new information here presented, we may exclude this hypothesis, at least for the ones observed via LIF and PL. In the literature, it is known that NBOHCs emissions occurring in the red region (around 600-650 nm/1.9-2.0 eV) in silica and quartz have two main excitation bands, centered at 2.0 eV and 4.8 eV [20]. We were not able to observe the lower energy one, due to the optical filters used, but we certainly do not observe the second one, at 4.8 eV.…”

“…Another point in favor of excluding NBOHCs from all the emission observed in PL and LIF experiments is shown in Figure 2. The fact that the emission intensity is apparently decreasing with irradiation seems to contradict the works of Skuja et al [20,21], where clearly the behavior of NBOHCs is the opposite: irradiation should increase the number of these centers. Unfortunately, with our equipment, we are not able to explore the same dose ranges studied by Skuja et al in reasonable time (above the MGy, even GGy), and as already stated, the quantitative part of the results should be taken with a grain of salt, but they seem to point to a relevant fact, nonetheless.…”

“…This sensitization process can have an impact in applications where quartz is used as a natural dosimeter [12]. Following our tentative assignment of part of the emission from this sample to NBOHCs and the works from Skuja [20,21], we also tried to observe the influence of X-ray irradiation on its photoluminescence (PL) properties, which are based on the same principles of the previous LIF experiment. Using PL, which also served as a reproducibility proof of the LIF data, we obtained additional information regarding the excitation spectrum of the observed emission, which we could not study with LIF.…”

Luminescence of non-bridging oxygen hole centers as a marker of particle irradiation of α-quartz

“…The PL of NBOHC (≈650nm) can be excited in 2 excitation bands. This paper demonstrates the identification of these PL centers in irradiated crystalline SiO 2 , using the more efficient excitation by UV laser light into the strong 4.8 eV (258 nm) absorption band of NBOHC, compared to the excitation into the weak 2.0 eV (620 nm) resonance absorption band used in the previous work (Skuja et al, 2019).…”

“…In high quality synthetic α-quartz singlecrystals red luminescence is completely absent and is not created by γ-irradiation (Cannas et al, 2004;Kajihara et al, 2013). However, at high irradiation doses by synchrotron X-rays (>20 GGy (G. E. King et al, 2011B)) or 2.5 MeV electrons (7.6 GGy (Skuja et al, 2019)) red luminescence centers are created.…”