Light emission of self-trapped excitons from ion tracks in silica glass: Interplay between Auger recombination, exciton formation, thermal dissociation, and hopping

The initial luminescence yield of amorphous silica under ion irradiation has been studied at temperatures between 30 and 100 K, using swift ions of different masses and energies (3 MeV H, 3.5 MeV He, 19 MeV Si and 19 MeV Cl). The intensity of the 2.1 eV emission band, ascribed to the intrinsic recombination of self-trapped excitons (STEs), has been found to vary systematically with ion mass, energy and irradiation temperature. A detailed model has been developed to quantitatively describe those variations in terms of the competition between non-radiative Auger recombination, STE formation, STE thermal dissociation, and subsequent STE hopping and capture at non-radiative sinks. The model, which uses a thermal spike approach to describe the effect of swift ion bombardment, is found to quantitatively predict the experimental data without adjustable parameters. It provides new insights into the interactions of carriers in an ion track and the behavior of the luminescence emissions during ion irradiation (ionoluminescence). The model is found to predict the correct temperature dependence of the yield if an activation energy for STE thermal migration of 0.12 eV is assumed, which is in good agreement with values previously reported.