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 (193 nm) and KrF (248 nm) excitation. The blue band is situated at 3.17 +/- 0.02 eV in the case of ArF and at 3 +/- 0.2 in the case of KrF. The UV band is at 4.55 +/- 0.05 eV in the case of ArF and at 4.5 +/- 0.05 eV in the case of KrF. The position of the UV emission band correlates with that excited by x rays. This position is 4.6 +/- 0.05 eV with FWHM 0.8 +/- 0.05 eV (Truhins et al 2003 Solid State Commun. 127 415). The blue band possesses slow decay kinetics with time constant 16 +/- 2 mu s and the UV band is fast on the level of 2 +/- 0.5 ns, similarly for both lasers. Thermal quenching of both bands begins for T higher than 150 K. The activation energies are similar for intensity and time constant, and are equal to 0.23 +/- 0.01 eV and 0.13 +/- 0.01 eV for blue and UV bands, respectively, with equal values of frequency factor, 2 x 10(11) s(-1). Optical absorption contains bands at 4.5, 5.5, and 7 eV and a strong band starting from 7 eV adjacent to the intrinsic absorption threshold above 8.75 eV. Excitation at 7.86 eV (F-2 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 a-quartz crystals allows us to conclude similar natures for the defect centers in these dissimilar materials.