Spectroscopic indication of chlorine, chemically bound to silica

Abstract

Synthesis of high-puny quartz glass tQG) bv chloride deposition has gained widespread acceptance in connection with the rise and rapid development of fiber optics. The chlorine impurity is an inevitable accompaniment of vapor-phase deposition with a nearly total absence of ceramic and metal inclusions (less than 10 -5 wt.%) in the glass. Depending on the specific technology of synthesis the chlorine content is varied from hundredths to tenths of a weight percent (to 0.5 wt.% in the MCVD method). The influence of impurity chlorine on the properties of QG has been scarcely investigated experimentally. There is only indirect evidence for decreased radiation resistance of QG due to the formation of E'-cenlers by reactions involving Si-CI groups 11, 2 I, i.e., chlorine may act as a "predecessor" of radiation defects [3 ]. However, this idea has not yet received support, since there are no direct experimental data on the existence of chlorine that is chemically bound to a silica skeleton of the glass. The presence of the Si-C1 groups in QG, deposited from silicon tetrachloride, is probable, owing to the similar properties of chlorine and fluoride that easily forms Si-F bonds in doped silica. Nevertheless, to this point we have failed to observe bands that could be assigned to atomic vibrations involving chlorine in the Raman spectrum that has characteristic bands of practically all the dopants used for QG (B, P, Ge, etc.). We also do not know of any evidence of other experimental methods for the formation of the groups =Si-CI. In this work we were able to obtain, by the method of Raman scattering, some indirect data on the influence