LUMINESCENCE AND DEFECT FORMATION IN UNDENSIFIED AND DENSIFIED AMORPHOUS SIO2

Luminescence and optical absorption induced by an electron pulse and by a subsequent laser pulse have been studied in densified and undensified amorphous SiO2 at 77 K. We find that the decay of the optical-absorption change induced by an electron pulse consists of two components: one which decays following a power law within 1 ms and the other which decays much more slowly. The fast component exhibits the spectrum of the self-trapped excitons, while the spectrum of the slow component includes the E band. The E band thus generated is found to decay with a time constant of about 10 h at 77 K and to be annihilated almost completely by warming to room temperature. We also find that optical excitation of the slow component by a 222-nm laser pulse generates a luminescence band having a peak at 2.1 eV, which is identical to the luminescence band due to the self-trapped excitons. It is likely that the defect pair and the self-trapped exciton have the same composition and both are generated as the result of the relaxation of excitons. © 1990 The American Physical Society.