The defect structure of ion irradiation damage localized in latent tracks in amorphous ${\mathrm{SiO}}_2$ and their role in the chemical etch rate of such tracks has been studied. A variety of light and heavy ions were used with energies ranging from 4 to 127 MeV. It was found that the frequency of the infrared absorption associated with the asymmetric stretch vibration of Si-O was significantly reduced following swift heavy-ion bombardment and that the shift correlated with the enhancement of the etching rate. In contrast, no correlation between the etching rate and either the $E^{\prime }$ center or the oxygen deficient center was observed. The IR peak shift has been related to the transition of ordinal six rings of ${\mathrm{SiO}}_4$ tetrahedra to planar three- and four-member rings, which were generated in the latent track due to the flash heating and quenching by bombardment. We propose that large numbers of planar three- and four-member rings in the latent track are responsible for the fast chemical etching rate.

• Received 1 February 2000

DOI:https://doi.org/10.1103/PhysRevB.62.3689