Photoluminescence excited by ArF and KrF lasers and optical absorption of stishovite mono-crystal

Two photoluminescence bands were found in a stishovite (silicon dioxide) mono-crystal sample under ArF (193nm) and KrF (248nm) excitation. The blue band is situated at 3.17 0.02eV in the case of ArF and at 3 0.2 in the case of KrF. The UV band is at 4.55 0.05eV in the case of ArF and at 4.5 0.05eV in the case of KrF. The position of the UV emission band correlates with that excited by x rays. This position is 4.6 0.05eV with FWHM 0.8 0.05eV (Truhins et al 2003 Solid State Commun. 127 415). The blue band possesses slow decay kinetics with time constant 16 2νs and the UV band is fast on the level of 2 0.5ns, similarly for both lasers. Thermal quenching of both bands begins for T higher than 150K. The activation energies are similar for intensity and time constant, and are equal to 0.23 0.01eV and 0.13 0.01eV for blue and UV bands, respectively, with equal values of frequency factor, 2 × 10¹¹s^-1. Optical absorption contains bands at 4.5, 5.5, and 7eV and a strong band starting from 7eV adjacent to the intrinsic absorption threshold above 8.75eV. Excitation at 7.86eV (F₂ laser) does not provide luminescence. The nature of the luminescence excited in the transparency range of stishovite is ascribed to a defect, presumably created by previous irradiation of the crystal. Similarity of the stishovite luminescence to that of oxygen-deficient silica glass and also to that induced by irradiation of α-quartz crystals allows us to conclude similar natures for the defect centers in these dissimilar materials.