Positron and positronium studies of irradiation-induced defects and microvoids in vitreous metamict silica

M. Hasegawa, M. Saneyasu, M. Tabata, Z. Tang, Y. Nagai, T. Chiba, Y. Ito

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42 Citations (Scopus)


To study irradiation-induced defects and structural microvoids in vitreous silica (v-SiO2), positron lifetime, angular correlation of positron annihilation radiation (ACAR), and electron spin resonance (ESR) were measured on v-SiO2 and quartz (c-SiO2) samples irradiated with fast neutrons up to a dose of 4.1×1020 n/cm2. Two kinds of positron-trapping defects have been found to form in v-SiO2 by fast neutron irradiation: type-I and type-II defects. Similar defects also appear in the irradiated c-SiO2, indicating that both the defects are common in v-SiO2 and c-SiO2. The detailed annealing and photo-illumination studies of positron annihilation and ESR for these two defects suggest that the type-I defects are non-bridging oxygen hole centers (NBOHC), while the type-II defects are oxygen molecules which cannot be detected by ESR. Higher dose irradiation than 1.0×1020 n/cm2 causes c-SiO2 to change to metamict (amorphous) phase (m-SiO2). Positronium (Ps) atoms are found to form in microvoids with an average radius of about 0.3 nm in the v-SiO2 and m-SiO2. This suggests that microvoids proved by Ps are structurally intrinsic open spaces and reflect the topologically disordered structure of these phases in the subnanometer scale.

Original languageEnglish
Pages (from-to)431-439
Number of pages9
JournalNuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Publication statusPublished - 2000 May 2
Event10th International Conference on Radiation Effects in Insulators - Jena, Ger
Duration: 1999 Jul 181999 Jul 23


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