Ion irradiation induced Al-Ti interaction in nano-scaled Al/Ti multilayers

Interactions induced in Al/Ti multilayers by implantation of Ar ions at room temperature were investgated. Initial structures consisted of (Al/Ti) × 5 multilayers deposited by d.c. ion sputtering on Si(1 0 0) wafers, to a total thickness of ∼250 nm. They were irradiated with 200 keV Ar⁺ ions, to the fluences from 5 × 10¹⁵ to 4 × 10¹⁶ ions/cm². It was found that ion irradiation induced a progressed intermixing of the multilayer constituents and Al-Ti nanoalloying for the highest applied fluence. The resulting nanocrystalline structure had a graded composition with non-reacted or interdiffused Al and Ti, and γ-AlTi and AlTi₃ intermetallic phases. Most intense reactivity was observed around mid depth of the multilayers, where most energy was deposited by the impact ions. It is presumed that Al-Ti chemical reaction is triggered by thermal spikes and further enhanced by chemical driving forces. The applied processing can be interesting for fabrication of tightly bond multilayered structures with gradual changes of their composition and properties.