A study of the critical factor determining the size of etched latent tracks formed on SiO2 glass by swift-Cl-ion irradiation

When a Cl ion with energy of the order of megaelectronvolts collides with SiO2 glass, it penetrates the glass along a straight line. The region through which the ion passes and its vicinity, called the latent track, can be easily etched by hydrofluoric acid, resulting in the formation of a nanopore. With increasing ion energy, the nanopore radius first increases, reaches a maximum, and then decreases. In order to analyze this strange phenomenon, we investigated the radius of the region that melted upon ion irradiation, as one of the possible approaches. We calculated its radius using heat diffusion equations and compared it with the radius of nanopores. We found that both the radii depend on the ion energy in a similar manner.