Structural properties of the range-II- and range-III order in amorphous-SiO 2 probed by electron paramagnetic resonance and Raman spectroscopy

. In the present work we report an experimental investigation by electron paramagnetic resonance spectroscopy on the hyperfine structure of the E' _γ point defect, probing the local arrangement of the network (range-II order), and by Raman spectroscopy on the D 1 and D 2 lines, probing mean features of the network (range-III order). Our studies, performed on a-SiO 2 samples thermally treated at 1000 °C in air for different time durations, show that changes of the hyperfine structure and of the D 1 and D 2 lines occur in a correlated way. These results give strong evidence that the range-II and range-III order properties are intimately related to each other and that these properties are determined by the history of the material.