Photoelectron spectroscopy of E′ centers in crystalline and glassy silicon dioxide

Radiation-induced E′ centers in SiO₂ were studied to test the possibility of applying optically stimulated electron emission (OSEE) to the spectroscopy of excited states of point defects in dielectrics. The spectral responses of the OSEE of crystalline α quartz and silica glass irradiated by 10-MeV electrons were measured and studied. It was established that volume E′ centers in the crystalline and glassy SiO₂ modifications are dominant emission-active defects. Surface E’_s (1) centers were also detected in glassy SiO₂. A model of the energy structure of E′ centers accounting for the absence of luminescence and taking into account the presence of two nonradiative (intracenter and ionization) relaxation channels is proposed. This model was used to explain the mechanism of photothermal decay of the E′ centers and to determine the ionization activation barriers and quantum yields of these centers. The emission, spectral, and kinetic parameters of the volume and surface E′ centers in glassy SiO₂ were obtained, showing the excited states of these defects to have identical atomic configurations.