PLASTIC-DEFORMATION IN SIO2 INDUCED BY HEAVY-ION IRRADIATION

Samples of vitreous silica and quartz were irradiated by different high-energy heavy ions at various temperatures. The dimensions of the samples were measured at room temperature before and after irradiation with different fluences. In the low-fluence range vitreous silica exhibits a long-known compaction which saturates at a density increase of about 3%. In the high-fluence range vitreous silica is, like other amorphous materials, subject to radiation-induced plastic deformation: the dimensions perpendicular to the ion beam grow without tendency to saturation whereas the dimension parallel to it shrinks. The deformation yield per incident ion is the higher, the lower the temperature and the larger the electronic energy loss. The samples of quartz are amorphized in the low-fluence range and subsequently undergo plastic deformation in the same way as vitreous silica. A model describing this plastic deformation is proposed and compared to the experimental results.