SILICON DIOXIDE THIN-FILM LUMINESCENCE IN COMPARISON WITH BULK SILICA

The luminescence of the self-trapped exciton (STE) in SiO2 films was m easured at low temperatures on the background of defect luminescence u nder cathodoexcitation and compared with bulk silica luminescence. The defect luminescence is mainly caused by non-bridging oxygen centers ( a red luminescence band at 1.8 eV) and twofold coordinated silicon cen ters (blue and ultraviolet luminescence with 2.7 and 4.4 eV bands, res pectively). The STE luminescence with a band at 2.3 eV is uniformly di stributed within SiO2 film volume. Contrary to defect luminescence, wh ose intensity increases with irradiation time, the STE luminescence de creases almost to zero in a few seconds of irradiation time. The defec t luminescence increase is attributed to transformation of precursors whereas STE luminescence is produced in the continuous network. The de crease of STZ luminescence is attributed to radiation damage in the co ntinuous network. (C) 1998 Published by Elsevier Science B.V.