Wafer curvature measurements were performed  in situ  in order to study the mechanical stresses in amorphous silica during Xe, Ne or Er bombardment at energies of between 0.27 and 4.0MeV. Network compaction, radiation-induced viscous flow, and non-saturating anisotropic deformation were detected. The radiation-induced viscosity was shown to be inversely proportional to the energy density that was deposited into atomic displacements. The relationship between radiation-induced flow and diffusion was considered within the context of the Stokes-Einstein equation. Viscous flow served to relax stress, and yet a continuous non-saturating anisotropic deformation effect caused the stress in the irradiated layer to saturate at non-zero values. Bombardment with Xe at energies of less than 3.6MeV resulted in a tensile saturation stress. At higher energies, a compressive stress built up. These effects were explained in terms of competing bulk and surface deformation processes that resulted from local heating of the silica around the ion tracks. The macroscopic effect of deformation was illustrated by studying the surface morphology after 4.9MeV Er irradiation through a contact implantation mask. An  in situ  stress study was also made of an alkali borosilicate glass. In this case, a fourth radiation-induced effect was observed. This was the generation and annihilation of volume-occupying point defects. These defects were shown to anneal out at room temperature, and exhibited a broad spectrum of activation energies.

E.Snoeks, T.Weber, A.Cacciato, A.Polman: Journal of Applied Physics, 1995, 78[7], 4723-32