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

The phase stability, upon vacuum annealing up to 1000 °C, of nanostructured (Ti,Zr)_1-xSi_xN 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 (40 kV). 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 11 nm) to nanocomposite state (0.19 < x ≤ 0.25, grain size of 5 nm). The phase composition of the films changes from single-phase, cubic c-(Ti,Zr)N columns with (1 1 1) preferred orientation to dual-phase system consisting of c-(Ti,Zr)N crystallites and amorphous SiN_y. Irradiation with He ions at the doses of 2 × 10¹⁶ and 5 × 10¹⁶ cm^-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 (2 0 0) 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.