ION IMPLANTATION-INDUCED AND RADIATION-INDUCED STRUCTURAL MODIFICATIONS IN AMORPHOUS SIO2

Data on the asymmetric infrared stretching mode of the oxygen in the Si-O-Si bridge and on the refractive index are examined for crystalline SiO2 polymorphs and compacted, amorphous SiO2. A set of experimentally based relationships is established between the infrared peak position and bridging bond angle and the refractive index and density. Using these relationships, results on radiation- and ion implantation-induced densification in amorphous SiO2 are examined. It is demonstrated that the saturation densification involves reduction in the bridging bond angle by approximately 10-degrees and a densification less-than-or-equal-to 3%. This result is inconsistent with the observed bond angle/density relationship established for pressure/temperature compacted amorphous SiO2. It is suggested that the overall densification results from a decrease in the bond angle and a simultaneous generation of both small and large rings.