Structural properties of the range-II- and range-III orderin amorphous-SiO2 probed by electron paramagnetic resonanceand Raman spectroscopy

In the present work we report an experimental investigation by electron paramagnetic resonancespectroscopy on the hyperfine structure of the E γ point defect, probing the local arrangement of thenetwork (range-II order), and by Raman spectroscopy on the D1 and D2 lines, probing mean features ofthe network (range-III order). Our studies, performed on a-SiO2 samples thermally treated at 1000◦Cin air for different time durations, show that changes of the hyperfine structure and of the D1 and D2lines occur in a correlated way. These results give strong evidence that the range-II and range-III orderproperties are intimately related to each other and that these properties are determined by the history ofthe material.