Oriented nickel-titanium shape memory alloy films prepared by annealing during deposition

Abstract

Nickel-titanium shape memory alloy films, between 2 and 10 μm thick, were sputter deposited onto (100) silicon substrates. Films deposited onto a substrate at ambient temperature were amorphous; however, several post-deposition annealing procedures produced crystalline films exhibiting the B2-to-B19' phase transition that gives rise to the shape memory effect. Films that were deposited onto a heated substrate, 350-460°C, crystallized during deposition, eliminating the need for a separate annealing step. Powder x-ray diffraction indicated that these films were highly oriented, with the NiTi (110)B2 face parallel to the silicon substrate (100) face.