Interface mixing in Ni 3N/SiX bilayers induced by swift heavy ions

Abstract

In order to investigate the swift heavy-ion-induced mixing of nitride coatings we have irradiated Ni 3N films on SiO 2-, Si 3N 4-, SiC- and Si-substrates with Ar, Kr, Xe and Au ions of energies ranging from 90 to 350 MeV , for which electronic energy loss dominates. The Ni-concentration profiles at the interfaces before and after irradiation were determined by means of Rutherford backscattering spectrometry with 900 keV He 2+ ions. In all the cases, strong mixing occurred as soon as a material-dependent threshold S ec in the electronic stopping power S e was exceeded. The mixing rate exhibits a squared scaling k= Δσ 2/Φ=η 2 (S e −S ec ) 2 and estimation of the effective diffusion constant indicates interdiffusion in molten ion tracks. The threshold value S ec depends on the substrate material and seems to be determined by its melting point and specific heat.