Crystallization kinetics of amorphous equiatomic NiTi thin films: Effect of film thickness

We have investigated the crystallization of amorphous equiatomic NiTi thin films sandwiched between two protective silicon nitride barrier films using optical, atomic force, and transmission electron microscopy. Crystallite nucleation occurs homogeneously inside the NiTi films because small composition shifts at the interfaces between NiTi and surrounding layers suppress heterogeneous nucleation at these interfaces. The crystallite growth rate is independent of film thickness for films thicker than 600 nm. Below 600 nm the growth rate decreases rapidly and has an apparent activation energy that increases with decreasing film thickness. We suggest that diffusion of hydrogen from the film interfaces may be responsible for this unusual behavior. a) Electronic mail: [email protected]