Fluorine doped vitreous silica analysis of fiber optic preforms by vibrationnal spectroscopy

Structural role of fluorine in amorphous silica

“…In addition to this new spectral feature, these Raman studies also demonstrate the effect of fluorine on lowering the fictive temperature of the silica glasses. The D1 and D2 defect bands in pure silica, commonly used to quantify the fictive temperature of the glass, are reduced and eventually eliminated as a function of increasing fluorine doping in amorphous silica [16,18]. IR data support the formation of Si-F groups in Fdoped silica, but the absence of bending and scissor modes precludes the formation of silicon tetrahedra with multiple fluorine atoms (i.e.…”

“…There are a number of studies based on Raman and Infrared (IR) spectroscopies, which all show the formation of Si-F bonds in the network. Raman spectra of F-doped silica contain a band around 945 cm À1 which increases in intensity with increasing fluorine content [16,17]. This band has been assigned to the stretching mode of Si-F, where the fluorine has replaced a bridging oxygen on the silicon tetrahedron.…”

The nature of fluorine in amorphous silica

“…Raman spectroscopic studies have shown that addition of fluorine to a-SiO 2 results in a new band near 945 cm À1 , assigned to an Si-F stretching mode [11,12]. To our knowledge, there is only one published report on a detailed study of F-doped a-SiO 2 using nuclear magnetic resonance (NMR) spectroscopy.…”

Structure characterization of F-doped silica glass

“…According to Refs. [8,9], an approximate relationship between the force constant of the Si-F bond and the sum of electronegativities of Si neighbours in various compounds is as follows:…”