The dependence of Raman defect bands in silica glasses on densification revisited

This paper focuses on the densification signature measured by Raman spectroscopy in silica-based glasses. We have studied a pure silica glass and a 25GeO2–75SiO2 binary glass fabricated by plasma chemical vapor deposition (PCVD), using the fictive temperature Tf as a variable parameter ranging from 950 to 1400 °C. Macroscopic density measurements highlighted two opposite behaviors: the higher the fictive temperature, the lower the density of the GeO2–SiO2 glass, in contrast to what is observed in the pure silica glass. Yet, Raman spectra of both these glasses showed similar trends: the intensities of the two defect bands, D1 and D2, increase with increasing fictive temperature. Therefore, the D1 and D2 bands cannot be used as a reliable signature of densification in binary glasses.