Observations of optically and thermally stimulated luminescence from aluminosilicate glasses

Analysis of thermoluminescence (TL) glow curves from aluminosilicate glass reveals that the glow curve in the region-400 K--600 K can be partly described by thermally excited tunneling from a defect excited state to the recombination center, plus a TL signal caused by thermal excitation directly to the delocalized band from a distribution of trapping states. Mathematical fitting reveals a range of trap depths and frequency factors for the tunneling which depend upon pre-heat temperature in a manner consistent with that expected from a tunneling model. Optical bleaching removes the TL signal from this region of the glow curve while at the same time producing an optically stimulated luminescence (OSL) signal. The OSL decay curve can be described by optically excited tunneling, plus a term consistent with ionization of trapped electrons directly to the delocalized band. Analysis of the dependence of the optical cross-section for tunneling indicates that the excited state resides within the band-tails states for the glass. Fading of the OSL signal is consistent with ground-state tunneling directly to the recombination site, while fading of the TL signal is consistent of ground-state tunneling plus thermal emptying of the shallower parts of the distribution of trapping states.