Thin film shape-memory alloys have been recognized as a promising and high performance material in the field of microelectromechanical systems applications. In this investigation, TiNi films were prepared by sputtering Ti and Ni target in argon gas using a magnetron sputtering system. Chemical composition, crystallography, microstructure and phase transformation behaviors of the deposited TiNi film were studied. Differential scanning calorimeter results showed that a two-stage transformation occurs in a sequence of monoclinic martensitic phase to rhombohedral phase, then to B2 phase upon heating, and vice versa on cooling. X-ray diffraction analysis also revealed the crystalline structure changes with the change of the temperatures. Nano- indentation reveals the elastic modulus of the film is about 5.11 GPa and the film intrinsic hardness is 2.84 +/- 0.5 GPa. By depositing TiNi films on the bulk micromachined Si cantilever structures, we obtained micro-grippers exhibiting a good shape-memory effect.

Date Published: 20 October 2000
PDF: 7 pages
Proc. SPIE 4230, Micromachining and Microfabrication, (20 October 2000); doi: 10.1117/12.404895

Published in SPIE Proceedings Vol. 4230:
Micromachining and Microfabrication
Kevin H. Chau; M. Parameswaran; Francis E.H. Tay, Editor(s)