Deposition of TiN layer on TiNi thin films to improve surface properties

TiNi based shape memory alloy (SMA) thin films have been widely used in biomedical and microelectromechanical systems. However, there are still some concerns for their wide applications because of their unsatisfactory mechanical and tribological performances, chemical resistance and biological reliability. This paper explored the deposition and effects of TiN protective layer on TiNi thin films to improve their surface properties while retaining the shape memory effects. Results indicated that the presence of an adherent and hard TiN layer (300 nm) on TiNi based SMA film (3.5 μm) formed a passivation layer, improved hardness and tribological properties, without sacrificing the phase transformation and shape memory effect of the TiNi film.