Texture development and phase transformation behaviour of sputtered Ni-Ti films

Texture development and phase transformation behaviour of sputtered Ni-Ti films

Martins, R. M. S.; Schell, N.; Silva, R.; Pereira, L.; Mahesh, K. K.; Braz Fernandes, F. M.

The technological importance of thin films has led to an unabated interest in the detailed characterization of their structure, morphology, and their interfaces. A real understanding of the underlying growth mechanisms and their microstructural development requires sophisticated in situ techniques. X-ray diffraction with high-brilliance beams is such a powerful technique, as it is demonstrated here for the study of Ni-Ti films.
Numerous examples of investigations on Ni-Ti films can be found in the literature but it has been reported that the deposition of Ni-Ti films with definite stoichiometry and high purity remains a challenge, and important issues like formation of film texture and its control are still unresolved.
It is essential to identify and control their preferential orientation since it is a crucial factor in determining the shape memory behaviour. Widening the scope of our previous experiments concerning the influence of the deposition parameters on the structure of the Ni-Ti films, the incorporation of a TiN buffer layer has been tested.
Here, it is established a clear relationship between the TiN substrates and Ni-Ti texture development (B2 phase) and it is shown that the distinct crystallographic orientations of the Ni-Ti films influence their phase transformation behaviour. The influence of a substrate bias voltage on the preferential orientation of the B2 phase and transformation temperatures is as well revealed. A lower biaxial stress state and lower phase transformation temperatures have been observed for the films deposited with bias (-45 and -90V). Therefore, the control of the energy of the bombarding ions could be used as a tool for the manipulation of the transformation temperatures.

Keywords: NiTi; shape memory alloys; texture; X-ray diffraction

  • Lecture (Conference)
    2008 International Conference for Shape Memory and Superelastic Technologies, 21.-25.09.2008, Stresa, Italy
  • Journal of Materials Engineering and Performance 18(2009), 543-547
    ISSN: 1059-9495

Permalink: https://www.hzdr.de/publications/Publ-12433
Publ.-Id: 12433