Shape memory effect in sputtered Ti–Ni thin films

• Published in: Journal of magnetism and magnetic materials Vol. 290; pp. 865 - 867
• Main Authors: Arranz, M.A., Riveiro, J.M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-04-2005
• Subjects: Electrical resistivity; Martensitic transformation; Microstructure; Shape memory; TiNi films; 81.30.Kf; TiNi films; 81.15Cd; 73.50.−h; Electrical resistivity; Shape memory; Martensitic transformation; Microstructure
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2004.11.396

The microstructure and electrical transport properties of Ti–Ni granular films have been investigated with X-ray diffraction and DC resistivity measurements, respectively. Samples with the eutectoid composition (
∼
50
at
%
Ni
)
were grown by RF magnetron sputtering on a heated sample holder. These films comprised
Ti
2
Ni
,
TiNi
3
and TiNi granular phases, their relative proportions and microstructures critically depending on the substrate temperature. A majoritary metastable TiNi phase was obtained in samples grown at temperatures above 600°, as inferred from the discussion of the X-ray diffraction plots. These crystalline films showed the hysteretic behaviour of the electrical resistance which is attributed to the characteristic shape memory effect of such a binary alloy. Besides, the DC resistivity measurements are accomplished in Joule-heated samples by which efficiently modify their microgranular structure from amorphous to crystalline, or even stabilize the TiNi phase after a flash annealing.