Modelling of track formation in nanocrystalline inclusions in Si3N4

Abstract

A multiscale modeling is applied to investigate structural changes caused by impacts of swift heavy ions in Si3N4 nanoclusters imbedded into amorphous and crystalline silicon nitride matrices. The approach combines the Monte Carlo code TREKIS describing the excitation kinetics of electronic and atomic subsystems and a classical molecular dynamics tracing subsequent relaxation of lattice atoms. Ion impacts in amorphous and crystalline Si3N4 result in formation of a cylindrical amorphous region of a reduced material density, surrounded by a shell with an increased density. The track diameter inside a nanosized inclusion in crystalline or amorphous matrices was found smaller than in surrounding materials, which can be explained by a heat confinement by grain boundaries.