Variability of the Si–O–Si angle in amorphous-SiO2 probed by electron paramagnetic resonance and Raman spectroscopy

We report an experimental investigation by electron paramagnetic resonance (EPR) and Raman spectroscopy on a variety of amorphous silicon dioxide materials. Our study by EPR have permitted us to point out that the splitting of the primary hyperfine doublet of the E γ ′ center shows a relevant sample-to-sample variability, changing from ∼41.8 to ∼42.6 mT in the set of materials we considered. The parallel study by Raman spectroscopy has enabled us to state that this variability is attributable to the different Si–O–Si angle characterizing the matrices of the different materials.