Compositional and structural characterization of temperature-induced solid-state reactions in Al/Ni multilayers

Diffusion controlled solid-state reactions during the annealing of Al/Ni multilayers deposited by rf magnetron sputtering onto silicon substrates have been studied. The samples with an overall atomic concentration of Al0.5Ni0.5 consisted of four Ni and four Al sublayers with a double layer thickness of 50.3 nm. The temperature induced compositional and structural changes during the annealing periods of 45 min were determined by Auger electron spectroscopy (AES) sputter depth profiling and x-ray diffraction. Up to 120 ^∘{}C no intermetallic phase was detected, albeit the AES sputter depth profiles indicated a significant enrichment of Ni in the Al layers. At temperatures around 160 ^∘{}C these sublayers nucleated completely into the Al₃Ni phase. With a further increase of the annealing temperature the reaction proceeded to the formation of Al₃Ni₂, and finally above 250 ^∘{}C to a homogeneous layer of bcc ordered AlNi.