6533b7d3fe1ef96bd125ff2c

RESEARCH PRODUCT

Oxygen Exchange at the Internal Surface of AmorphousSiO2Studied by Photoluminescence of Isotopically Labeled Oxygen Molecules

subject

description

The exchange between lattice and interstitial oxygen species in an oxide was studied by the $^{16}\mathrm{O}\mathrm{\text{\ensuremath{-}}}^{18}\mathrm{O}$ isotope shift of the ${a}^{1}{\ensuremath{\Delta}}_{g}(v=0)\ensuremath{\rightarrow}{X}^{3}{\ensuremath{\Sigma}}_{g}^{\ensuremath{-}}(v=1)$ infrared photoluminescence band of the oxygen molecules (${\mathrm{O}}_{2}$) incorporated into the interstitial voids of amorphous ${\mathrm{SiO}}_{2}$ ($a\mathrm{\text{\ensuremath{-}}}{\mathrm{SiO}}_{2}$) by thermal annealing in $^{18}\mathrm{O}_{2}$ gas. A large site to site variation of the oxygen exchange rate, originating from structural disorder of $a\mathrm{\text{\ensuremath{-}}}{\mathrm{SiO}}_{2}$, is found. The average exchange rate has an activation energy of $\ensuremath{\sim}2\text{ }\text{ }\mathrm{eV}$, which is much larger than that for the diffusion of interstitial ${\mathrm{O}}_{2}$ ($\ensuremath{\sim}0.8--1.2\text{ }\text{ }\mathrm{eV}$). The average exchange-free diffusion length of interstitial ${\mathrm{O}}_{2}$ exceeds $\ensuremath{\sim}1\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ below $900\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, providing definite evidence that oxygen diffuses as interstitial molecules in $a\mathrm{\text{\ensuremath{-}}}{\mathrm{SiO}}_{2}$.