In situobservation of the generation and annealing kinetics of E ′ centres induced in amorphous SiO₂by 4.7 eV laser irradiation

Abstract

The kinetics of E ' centres induced in silica by 4.7 eV laser irradiation was investigated observing in situ their optical absorption band at 5.8 eV. After exposure, the defects decay due to reaction with diffusing molecular hydrogen of radiolytic origin. Hydrogen-related annealing is also active during exposure and competes with the photo-induced generation of the centres until a saturation is reached. The concentrations of E ' and H(2) at saturation are proportional, so indicating that the UV-induced generation processes of the two species are correlated. These results are consistent with a model in which E ' and hydrogen are generated from a common precursor Si-H.

Urbach rule in photoelectron emission from surface states of low-sized silica

“…In our case they can be ascribed to technological defects that are forming during SiO 2 film growth. Additional increase of E 0 -centers concentration can take place due to optically-stimulated ODC conversion processes (see, for example, [13]). It is also necessary to note that OSEE method sensitivity is extremely high thus providing an opportunity to determine low defect centers density that lie beyond the limits of ESR and other techniques [6,7,12].…”

Influence of Ce codoping and H2 pre-loading on Er/Yb-doped fiber: Radiation response characterized by Confocal Micro-Luminescence

“…We observe that in the present work the radiation exposure is performed without free H 2 in the fiber core. However, hydrogen could be made available by the radiolysis of Si-H and O-H groups [16][17][18], most of them being formed by H 2 loading. The action of the addition of Ce is expected to be completely different from that of H 2 , due to its immobility, and could be related to its multivalent state in silica glass, acting as a reducing or oxidizing element.…”

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

“…In particular, in wet fused silica it was demonstrated that hydrogen and E' are generated together by breaking of Si-H precursors [10]:…”

“…In recent experiments performed on wet fused silica samples, it was observed that 4.7eV laser irradiation at room temperature induces the generation of E' centers by breaking of Si-H precursors [10]. After the end of irradiation, the defects undergo a spontaneous decay whose kinetics lasts a few hours [5,10].…”

“…After the end of irradiation, the defects undergo a spontaneous decay whose kinetics lasts a few hours [5,10]. This process was attributed to reaction (1) by comparison of its kinetics with the diffusion parameters of H 2 , and by the observation by electron spin resonance (ESR) of the concurrent growth of H(II) centers (=Ge-H•) [5], which may considered as a fingerprint of the presence of mobile hydrogen.…”