ION-INDUCED CRYSTALLIZATION AND AMORPHIZATION AT CRYSTAL AMORPHOUS INTERFACES OF SILICON/

New empirical equations describing the rate of ion-induced crystalliza tion at a Si crystal/amorphous interface have been developed. In our m odel, crystallization/amorphization at the interface arises from forma tion of hot spots and of knock-ons in the collision cascades. It is pr esumed that the hot spots induce amorphous-to-crystal transformation w hich lowers the free energy, similarly to heating to high temperatures , and that the bond rearrangement by a series of displacements by knoc k-ons and recombination to the original lattice point in collision cas cades can lead to both crystal-to-amorphous and amorphous-to-crystal t ransformations. In both hot-spot and knock-on effects, the presence of di-vacancies under irradiation with ion beams is assumed to prohibit crystallization. The model can explain the experimental observation th at the crystallization/amorphization rate is scaled by X = phi(1/2)exp (E/2kT), the product of the root of the flux and the inverse of root o f the Boltzmann factor for the motion of the di-vacancies. Crystalliza tion rate in the hot-spots derived assuming that an incident ion induc es spontaneous crystallization within a characteristic volume along th e track reveals that the radius is 10 atomic distances and the thickne ss of is about 0.3 monolayer for 1.5 MeV Xe ions. The calculated cryst allization/amorphization rate fits to experimental results over a wide temperature range.