High dose ion irradiation effects on immiscible AlN/TiN nano-scaled multilayers

The effects of high dose Ar ion irradiation on immiscible AlN/TiN multilayered structures were studied. The structures with 30 alternate layers of a total thickness of ∼ 260 nm were deposited by reactive sputtering on (100) Si wafers. Individual layer thickness was ∼ 8 nm AlN and ∼ 9.3 nm TiN. Irradiation was done with 180 keV Ar⁺ ions to 1 × 10¹⁶–8 × 10¹⁶ ions/cm², with the projected range around mid-depth of the structures. It was found that the highest applied dose induced a considerable intermixing, where the growing TiN grains consume the adjacent AlN layers, transforming partly to (TiAl)N phase. Intermixing occurs due to a high contribution of collision cascades, which was not compensated in demixing by chemical driving forces. However, a multilayered structure with relatively flat surface and interfaces is still preserved, with measured nano-hardness value above the level for the as-deposited sample. The results are compared to other systems and discussed in the light of the existing ion beam mixing models. They can be interesting towards better understanding of the processes involved and to development of radiation tolerant coatings. - Highlights: ► Argon ion irradiation effects on immiscible AlN/TiN multilayers were investigated. ► High dose of 8 × 10¹⁶ Ar/cm² induced intermixing and formation of (TiAl)N phase. ► In the mixing process, TiN grains grow and consume the adjacent AlN layers. ► Despite intermixing, a multilayered structure and interface planarity are preserved. ► The results can be interesting for development of radiation tolerant coatings