Transient thermal processes in heavy ion irradiation of crystalline inorganic insulators

A review of matter transformation induced in crystalline inorganic insulators by swift heavy ions is presented. The emphasis is made on new results obtained for amorphizable materials such as Gd3Ga5O12, GeS, and LiNbO3 and for non-amorphizable crystals such as SnO2, LiF and CaF2. Assuming that latent tracks result from a transient thermal process, a quantitative development of a thermal spike is proposed. The only free parameter is the electron-lattice interaction mean free path lambda. With this parameter it is possible to quantitatively describe track radii, whatever the bonding character of the crystal is, in a wide range of ion velocities assuming two specific criteria: tracks may result from a rapid quenching of a cylinder of matter in which the energy deposited on the lattice has overcome either the energy necessary to reach a quasi-molten phase in the case of amorphizable materials or the cohesion energy in the case of non-amorphizable materials. The evolution of the lambda parameter versus the band gap energy of the considered insulator will be presented. On the basis of this discussion some predictions are developed. (C) 2000 Elsevier Science B.V. All rights reserved.