Adhesion and interfacial structure of magnetron sputtered TiNi films on Si/SiO 2 substrate

Abstract

Shape memory alloy TiNi films were prepared on Si and Si/SiO 2 by co-sputtering of TiNi target (Ti 50 at.% and Ni 50 at.%) and Ti target (99.999 at.%). When comparing Si/TiNi with Si/SiO 2/TiNi, the addition of SiO 2 sandwich layer did not result in significant change in the crystalline structures and shape memory properties. The SiO 2 sandwich layer served as an effective diffusion barrier in preventing formation of interfacial titanium silicide at the expense of film adhesion. As revealed by X-ray photoelectron spectroscopy, under the same conditions, the interfacial diffusion zone in Si/TiNi system was approximately 120 nm while in Si/SiO 2/TiNi system the diffusion zone was only approximately 30 nm—a four-fold reduction in inter diffusion. Meanwhile, the scratch adhesion testing registered a sharp drop in adhesion of the film from 170 mN in Si/TiNi system to 60 mN in Si/SiO 2/TiNi system.