Synthesis of Ni/Ti thin film by magnetron sputtering to study the effect of annealing time on microstructure and mechanical properties

Abstract

Thin films composed of a single layer of nickel and titanium were fabricated using magnetron sputtering at room temperature on a Si substrate and the as-deposited films were subsequently annealed to achieve nickel-titanium (NiTi) shape memory alloys. In this paper, we have reported a simplistic way that can be applied to achieve the near equiatomic Ni-Ti alloy thin films with precise controllability of chemical compositions. The compositions were prepared by taking the weight of individual elements in the proper stoichiometric proportions maintaining near equiatomic ratio of Ni and Ti. The surface-interface studies have been performed focusing on interlayer diffusion over the nano-level structure at 500°C for different holding times. The X-ray diffraction patterns of the films annealed at 500°C for different annealing times revealed various kinds of intermetallic compounds and second phase particles along with silicides. Nanoindentation tests on the single bi-layer (two alternative layers) of Ni-Ti thin films were conducted to evaluate the mechanical properties. Subsequent investigation revealed diffusion and migration of atoms between Ni and Ti layers by post-deposition heat treatment consequently have a profound impact on mechanical properties of these films.