Thermal stability of nanostructured TiZrSiN thin films subjected to helium ion irradiation

Abstract

The phase stability, upon vacuum annealing up to 1000°C, of nanostructured (Ti,Zr)1−xSixN thin films is investigated by X-ray diffraction analysis as a function of Si content (0.13⩽x⩽0.25) and prior irradiation with He ions (40kV). The quaternary TiZrSiN thin films were deposited by reactive magnetron sputtering from elemental targets at the substrate temperature of 600°C. It was found that the increase in Si content, x, results in the transformation of structure from nanocrystalline (x=0.13, grain size of 11nm) to nanocomposite state (0.19<x⩽0.25, grain size of 5nm). The phase composition of the films changes from single-phase, cubic c-(Ti,Zr)N columns with (111) preferred orientation to dual-phase system consisting of c-(Ti,Zr)N crystallites and amorphous SiNy. Irradiation with He ions at the doses of 2×1016 and 5×1016cm−2 does change the phase composition of the films. It is found that the onset temperature for phase decomposition decreases from 1000°C to 800°C with increasing Si content for unirradiated films. The formation of a secondary ZrN phase is observed concomitantly with increased broadening of the (200) c-(Ti,Zr)N diffraction peak. For irradiated films, the subsequent annealing at 1000°C leads to decomposition of the c-(Ti,Zr)N solid solution into TiN- and ZrN-rich phases as well as crystallization of hexagonal Si3N4 phase.