Stability of E' centers induced by 4.7eV laser radiation in SiO2

TL;DR

This study investigates the stability and decay mechanisms of E' centers in silica induced by 4.7 eV laser radiation, highlighting the role of hydrogen and temperature effects on defect annealing.

Contribution

It provides new insights into the formation and stabilization of E' centers in silica, emphasizing the influence of hydrogen and temperature on defect decay.

Findings

E' centers are generated by laser-induced breaking of Si-H precursors.

Hydrogen reacts with E' centers, leading to defect decay post-irradiation.

Lower temperatures slow down defect annealing, freezing it at 200K.

Abstract

The kinetics of E' centers (silicon dangling bonds) induced by 4.7eV pulsed laser irradiation in dry fused silica was investigated by in situ optical absorption spectroscopy. The stability of the defects, conditioned by reaction with mobile hydrogen of radiolytic origin, is discussed and compared to results of similar experiments performed on wet fused silica. A portion of E' and hydrogen are most likely generated by laser-induced breaking of Si-H precursors, while an additional fraction of the paramagnetic centers arise from another formation mechanism. Both typologies of E' participate to the reaction with H_2 leading to the post-irradiation decay of the defects. This annealing process is slowed down on decreasing temperature and is frozen at T=200K, consistently with the diffusion properties of H_2 in silica.