29Si Hyperfine Structure of the E'_\alpha Center in Amorphous Silicon Dioxide

TL;DR

This study uses electron paramagnetic resonance to analyze the 29Si hyperfine structure of the E'_alpha defect in amorphous silicon dioxide, proposing a microscopic model based on experimental data.

Contribution

It provides the first detailed EPR analysis of the 29Si hyperfine structure of the E'_alpha center and introduces a microscopic model for its atomic configuration.

Findings

29Si hyperfine lines split by 49 mT observed

E'_alpha center involves a hole in an oxygen vacancy

Proposed model: unpaired electron in a back-projected orbital interacting with an oxygen atom

Abstract

We report a study by electron paramagnetic resonance (EPR) on the E'_\alpha point defect in amorphous silicon dioxide (a-SiO2). Our experiments were performed on gamma-ray irradiated oxygen-deficient materials and pointed out that the 29Si hyperfine structure of the E'_alpha consists in a pair of lines split by 49 mT. On the basis of the experimental results a microscopic model is proposed for the E'_alpha center, consisting in a hole trapped in an oxygen vacancy with the unpaired electron sp3 orbital pointing away from the vacancy in a back-projected configuration and interacting with an extra oxygen atom of the a-SiO2 matrix.