D. Yu. Biryukov

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.

Photoemission and luminescence properties of quartz glass implanted with Cu + ions

The special features of optically stimulated electron emission and luminescence of defects in KV quartz glass after Cu+ ion pulse implantation are studied. It is shown that the ion-beam modification of the photoemission and luminescence properties of samples is due to the formation of radiation defects and by dimensional factors caused by the appearance of Cu nanoparticles.

Nonradiative relaxation of photoexcited O 1 0 centers in glassy SiO2

The processes involved in the excited-state relaxation of hole O10 centers at nonbridging oxygen atoms in glassy SiO2 were studied using luminescence, optical absorption, and photoelectron emission spectroscopy. An additional nonradiative relaxation channel, in addition to the intracenter quenching of the 1.9-eV luminescence band, was established to become operative at temperatures above 370 K. This effect manifests itself in experiments as a negative deviation of the temperature-dependent luminescence intensity from the well-known Mott law and is identified as thermally activated external quenching with an energy barrier of 0.46 eV. Nonradiative transitions initiate, within the external quenching temperature interval, the migration of excitation energy, followed by the creation of free electrons. In the final stages, this relaxation process becomes manifest in the form of spectral sensitization of electron photoemission, which is excited in the hole O10-center absorption band.

Electron-emission activity of defects in surface layers of crystalline and vitreous silica

This paper deals with the photoemission activity of radiation defects in crystalline and vitreous silica. Spectral and kinetic parameters and the concentration of defects in the surface layer and the bulk of the material were determined. Some features of the distribution of radiation-induced defects along the depth of samples having different degrees of order were analyzed. Regularities of relaxation of excited states of emission centers suggested that thermally activated processes were involved in the release of electrons.

Formation and electron-beam annealing of implantation defects in a thin-film Si-SiO2 heterostructure

The radiation-induced defects in a 20-nm-thick SiO2 film on a silicon wafer are studied by optically stimulated electron emission. Accelerated (12-keV) silicon ions is found to generate various oxygen-deficient centers, among which E′-type defects are dominant. Subsequent irradiation by 23-MeV electrons changes the defect structure of the SiO2 film: the defects induced by ion implantation decompose.

Influence of Point Defects in a Surface Layer on the Strength Characteristics of Glasses

The influence of the nature and the concentration of defects in a surface layer on the radiation resistance and the microhardness of silicate glasses is studied by photoemission spectroscopy. The investigation is performed with two types of silicate glasses: the K8 optical glass irradiated with fast electrons and an industrial sheet glass with a thermally polished surface. It is established that the radiation resistance and microhardness of glasses are determined by the content of structural defects of a particular nature. The radiation resistance of the surface of K8 optical glass decreases with an increase in the concentration of radiation E–4-centers, which are representative of the density of band-tail localized electron states recharged by irradiation. The microhardness of the studied glasses with different treatment of their surface depends linearly on the number of defect centers at the nonbridging and radiation-damaged bridging bonds of the silicon–oxygen network.