Visible to deep ultraviolet range optical absorption of electron irradiated borosilicate glass

To study the room-temperature stable defects induced by electron irradiation, commercial borosilicate glasses were irradiated by 1.2 Me V electrons and then ultraviolet(UV) optical absorption(OA) spectra were measured. Two characteristic bands were revealed before irradiation, and they were attributed to silicon dangling bond(E’-center) and Fe3+species,respectively. The existence of Fe3+was confirmed by electron paramagnetic resonance(EPR) measurements. After irradiation, the absorption spectra revealed irradiation-induced changes, while the content of E’-center did not change in the deep ultraviolet(DUV) region. The slightly reduced OA spectra at 4.9 e V was supposed to transform Fe3+species to Fe2+species and this transformation leads to the appearance of 4.3 e V OA band. By calculating intensity variation, the transformation of Fe was estimated to be about 5% and the optical absorption cross section of Fe2+species is calculated to be 2.2 times larger than that of Fe3+species. Peroxy linkage(POL, ≡Si–O–O–Si≡), which results in a 3.7 e V OA band, is speculated not to be from Si–O bond break but from Si–O–B bond, Si–O–Al bond, or Si–O–Na bond break. The co-presence defect with POL is probably responsible for 2.9-e V OA band.