J. Phys. IV France 03 (1993) C4-209-C4-211
Defects in vitreous SiO2 probed by positron annihilationA. UEDONO, L. WEI, X. LI and S. TANIGAWA
Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305, Japan
Annihilation characteristics of positrons in a single quartz crystal and vitreous silica glasses (v-SiO2) were studied by measurements of two-dimensional angular correlation of positron annihilation radiations. From the measurements, it was found that positrons and positronium (Ps) atoms mainly annihilate from trapped states by vacancy-type defects in the v-SiO2 specimen. For the v-SiO2 specimen with a cylindrical porous structure, the annihilation of Ps with anisotropic momentum distributions was observed. This was attributed to the momentum uncertainty due to a localization of Ps in a finite dimension of pores. The present investigation showed possibilities for the detection of microstructures in v-SiO2 by the positron annihilation technique.
© EDP Sciences 1993