Evolution of ion track profiles in amorphous SiO2

The folding track replica method is applied to study the amorphous SiO2 layer of Si-SiO2 wafers irradiated with beams of 118 MeV Au197 and 80 and 106 MeV I127 ions. This technique is used to evaluate single track profiles. Measurements of the dimensions and shape of ion track profiles obtained by the track replica technique and observed with transmission electron microscopy are used to determine the curves of diameter and track length evolution with etching time. At certain etching time, an unexpected restriction on the chemical attack velocity at the track vertex is observed. A local generation of recrystallized silicon nanostructures is suggested as a possible explanation of this behaviour. A comparison is also made between results obtained by this technique and by AFM tapping mode observations.