Kinetics of NiAl3 growth induced by steady-state thermal annealing at the Ni-〈Al〉 interface

Substrates of large grained aluminum crystals were prepared by the strain annealing technique, and Ni films were vacuum evaporated on these substrates after an in situ sputter cleaning process. Upon thermal annealing of samples in vacuum, a laterally uniform growth of NiAl3 is observed, starting from 330 °C, without any indication of boundary diffusion effects. The aluminide phase grows as (duration)1/2 after an initial incubation period with an activation energy of 1.4 eV, i.e., K=x2/t=0.387 (cm2/s)exp(−1.4 eV/kT) for 600 K<T<650 K. Impurities, either at the interface or inside the Ni film, retard this reaction.