Threshold and criterion for ion track etching in SiO2 layers grown on Si

• We investigated the track “etchability” in SiO2 irradiated with swift heavy ions.
• Results of etching were compared with predictions based on the thermal spike model.
• Radius of molten region along ion path may be used as track “etchability” criterion.
• In the same etching conditions the pore size increases with the molten region radius.

SiO2 layers thermally grown on Si wafers were irradiated with swift heavy ions in the energy range of (20–710) MeV. Subsequent chemical etching in 4% HF for 6 min produced conical pores with diameters from ∼20 to ∼80 nm in the SiO2 layers. We have calculated radii and lifetime of the molten regions in the SiO2 layers and compared them with the pore diameters and diameter dispersions estimated from scanning electron microscopy and atomic force microscopy. It is shown that the existence of a molten region and its radius can serve as a valid criterion for track “etchability”. In the same etching conditions the etched track diameter and the etching velocity in the track region are proportional to the radius and the lifetime of the molten region.