Amorphous track formation in SiO2

Amorphous track formation is analyzed in SiO2 alpha-quartz according to a thermal spike model. As predicted by the model, for tracks with R(e) > 4.5 nm R(e)(2) similar to S-e (R(e) - the effective track radius, S-e - the electronic stopping power) fulfils for alpha-SiO2. The efficiency of energy deposition is g = 0.36 for low velocity ion bombardment in excellent agreement with that in yttrium iron garnet and lithium niobate. The high efficiency is the consequence of the effect of the ion velocity on the damage cross section. Tracks with R(e) < 4.5 nm exhibit an ambiguity that can be resolved only by new experiments. The consequences of the variation of the spatial width of the electron energy distribution with the ion velocity are discussed.