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Title: Thermal stability of gamma-irradiation-induced oxygen-deficient centers in silica

Abstract

The effects of isochronal thermal treatments on three {gamma}-irradiation-induced point defects, named the E{sup '}, ODC(II), and H(I) centers, are investigated in various types of commercial silica (a-SiO{sub 2}). ODC(II) is investigated by means of photoluminescence spectroscopy, and the H(I) and E{sup '} centers by electron paramagnetic resonance. The annealing processes of the ODC(II) and H(I) center are shown to be independent of each other, and no conversion mechanisms are evidenced. In contrast, a strong similarity is observed between the annealing curves of the ODC(II) and E{sup '} centers. We tentatively ascribe the annealing processes to reactions of the defects with radiolytically formed molecules. We suggest that the H(I) center reacts with molecular hydrogen diffusing through the matrix, whereas, by analogy with results reported in the literature about the E{sup '} center, the annealing of ODC(II) is attributed to reactions with molecular oxygen or water.

Authors:
;  [1]
  1. Dipartimento di Scienze Fisiche ed Astronomiche, University of Palermo, Via Archirafi 36, I-90123 Palermo (Italy)
Publication Date:
OSTI Identifier:
20788006
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 73; Journal Issue: 11; Other Information: DOI: 10.1103/PhysRevB.73.115203; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; DIFFUSION; E CENTERS; ELECTRON SPIN RESONANCE; ELECTRONS; GAMMA RADIATION; H CENTERS; HYDROGEN; I CENTERS; IRRADIATION; MOLECULES; OXYGEN; PARAMAGNETISM; PHOTOLUMINESCENCE; PHYSICAL RADIATION EFFECTS; POSITRONS; RADIOLYSIS; SILICA; SILICON OXIDES; WATER

Citation Formats

Agnello, S., and Nuccio, L. Thermal stability of gamma-irradiation-induced oxygen-deficient centers in silica. United States: N. p., 2006. Web. doi:10.1103/PHYSREVB.73.1.
Agnello, S., & Nuccio, L. Thermal stability of gamma-irradiation-induced oxygen-deficient centers in silica. United States. doi:10.1103/PHYSREVB.73.1.
Agnello, S., and Nuccio, L. Wed . "Thermal stability of gamma-irradiation-induced oxygen-deficient centers in silica". United States. doi:10.1103/PHYSREVB.73.1.
@article{osti_20788006,
title = {Thermal stability of gamma-irradiation-induced oxygen-deficient centers in silica},
author = {Agnello, S. and Nuccio, L.},
abstractNote = {The effects of isochronal thermal treatments on three {gamma}-irradiation-induced point defects, named the E{sup '}, ODC(II), and H(I) centers, are investigated in various types of commercial silica (a-SiO{sub 2}). ODC(II) is investigated by means of photoluminescence spectroscopy, and the H(I) and E{sup '} centers by electron paramagnetic resonance. The annealing processes of the ODC(II) and H(I) center are shown to be independent of each other, and no conversion mechanisms are evidenced. In contrast, a strong similarity is observed between the annealing curves of the ODC(II) and E{sup '} centers. We tentatively ascribe the annealing processes to reactions of the defects with radiolytically formed molecules. We suggest that the H(I) center reacts with molecular hydrogen diffusing through the matrix, whereas, by analogy with results reported in the literature about the E{sup '} center, the annealing of ODC(II) is attributed to reactions with molecular oxygen or water.},
doi = {10.1103/PHYSREVB.73.1},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 11,
volume = 73,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
  • We report a study of the luminescence activity of oxygen-deficient centers stabilized in as-grown synthetic silica, as compared with the same defects induced by {beta} irradiation at increasing doses, ranging from 1.2x10{sup 3} to 5x10{sup 6} kGy. We experimentally observe a progressive broadening of the luminescence band with increasing total electron dose released on samples. By analyzing our data within a theoretical model capable of separating homogeneous and inhomogeneous contribution to the total luminescence linewidth, we observe that the increasing of the width is entirely ascribable to the inhomogeneous component which increases, in the most irradiated sample, of 60% withmore » respect to the value in the as-grown sample. This effect can be due either to the progressive creation of new defects statistically exploring different sites of the matrix, or to a progressive structural transformation of silica host which affects the optical properties of induced point defects.« less
  • Generation of typical paramagnetic centers by [gamma] irradiation was studied for various kinds of synthetic silica glasses. Growth behavior of [ital E][prime] centers and nonbridging oxygen hole centers (NBOHC's) with [gamma]-ray dose depends on contained preexisting point defects. By irradiation at room temperature, [ital E][prime] centers grow linearly and show a saturating tendency in silicas that contain precursors for [ital E][prime] centers, such as oxygen-deficient centers (ODC's), Si-H bonds or Si-Cl bonds. In silicas that contain very few precursors for [ital E][prime] centers, the growth of [ital E][prime] centers with the dose substantially equals that of NBOHC's and both followmore » a sublinear growth law in which the concentration of the defects is proportional to the square root of the dose. These results lead to the conclusion that [gamma] irradiation fundamentally creates defect pairs of an [ital E][prime] center and an oxygen hole center from an intrinsic Si-O network of amorphous silica; this is in addition to a large amount of [ital E][prime] centers induced from preexisting point defects as precursors. By irradiation at 77 K, [ital E][prime] centers and self-trapped holes are suggested to be formed as the defect pair from the Si-O network, while the conversion of the precursors into [ital E][prime] centers is probably lessened. Concentration of [ital E][prime] centers generated by [gamma] irradiation is almost the same as that of irradiation of ultraviolet lasers and x rays if they are compared based on the absorbed energy. Thus, defect generation with [gamma] rays is suggested to involve similar fundamental processes as those with photons, which have much smaller energy than [gamma] rays.« less
  • The methods for producing the oxygen-deficient centers and the experimental findings on the photoinduced processes in silica and germanosilicate glasses as well as in such optical waveguides manufactured from these glasses that underlie the development of promising integrated-optical and optical fiber devices and instruments are considered. the discrepancy in the photochromic process interpretation made on the ground of the structural models proposed for the oxygen-deficient centers in the glasses under consideration is discussed. The observable photoinduced transformations of the oxygen-deficient centers and associated changes in the physical properties of the glasses are explained on the assumption that photoexcitation initiates notmore » internal ionization, but solid-phase chemical reactions accompanied by the breaking and switching of valence bonds.« less
  • We compare the charging response of rapid thermally annealed (800 and 1000 deg. C) 4 nm thick HfO{sub 2} to as-deposited HfO{sub 2} on Si by measuring the surface potential of the HfO{sub 2} layers after vacuum ultraviolet (VUV) irradiation with 11.6 eV photons. From VUV spectroscopy, we determined all HfO{sub 2} layers show the presence of oxygen-interstitial defects (OIDs). The electronic states of OID in HfO{sub 2} line up in energy with oxygen-deficient Si centers within the SiO{sub 2} interfacial layer. This implies charge exchange between OIDs within HfO{sub 2} and the O-deficient silicon centers within the SiO{sub 2}more » interfacial layer are very important for controlling the radiation-induced trapped charge in HfO{sub 2} dielectric stacks.« less