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

Abstract

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 ~260nm were deposited by reactive sputtering on (100) Si wafers. Individual layer thickness was ~8nm AlN and ~9.3nm TiN. Irradiation was done with 180keV Ar+ ions to 1×1016–8×1016ions/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.