Fabrication and characterization of sputtered NiTi shape memory thin films

Sputtering conditions to produce nearly equiatomic NiTi films were studied. Two heat treatment methods, substrate heating (550 °C) and post-sputter heat treatments (solution heat treatment at 700 °C and precipitation heat treatment at 400 °C), were used to crystallize NiTi films. The NiTi films were analysed for their atomic composition, crystal structure, transformation temperatures, residual stress and Young's modulus. NiTi films produced by rf magnetron sputtering were slightly titanium rich. With appropriate post-sputter heat treatment, NiTi films with phase transformation temperatures within the human body temperature range (34-42 °C) were produced. The films also demonstrated two-way shape memory training capability.