iTS Model-Based Comparative Analysis of Track Formation in Crystalline and Amorphous Silicone Nitride

Abstract

Silicon nitride is a promising candidate material for inert matrix fuel host to be used for transmutation of minor actinides via nuclear reactions. Radiation-induced changes in this material are subjects of extensive studies. Most corresponding literature data focus on radiation damage produced by neutron and charged particle radiation in elastic collisions and much less is known about defects formed via relaxation of dense electronic excitations associated with high-energy heavy ion irradiation. The purpose of this report is the analysis of latent track parameters in polycrystalline and amorphous Si3N4 irradiated with swift (700 MeV) Bi ions deduced from transmission electron microscopy (TEM) examination. We discuss the applicability of the «core-shell» approach based on the inelastic thermal spike model to describe the latent formation in this ceramic comparing experimental and calculated track sizes. The threshold vaporization energy level corresponding to the core radii found from TEM data is equal Eb=1.6 eV/atom for polycrystalline silicon nitride. Additionally, the threshold electron loss energy necessary for track formation was estimated as ~14 keV/nm for amorphous Si3N4 and ~18 keV/nm for polycrystalline Si3N4.