Microstructure and Functional Properties of the TiNi- and CuAl-Based SMA Thin Films and Coats Produced by PVD Technique

Kolomytsev, V. I.; Musienko, R. Ya.; Nevdacha, V. V.; Panarin, V. E.; Pasko, Alexandre; Portier, R.; Ochin, P.; Cesari, E.; Seguı́, C.; Humbeeck, Jan Van

doi:10.4028/www.scientific.net/msf.327-328.311

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“…The ability of the martensite to plastically deform by the motion of twin and shear-variant boundaries gives rise to the shape-memory effect (SME), in which large plastic strains imparted to the martensite can be recovered during endothermal transformation to the austenite on heating. It is now well known that these effects are robustly expressed in sputtered thin films of appropriate structure and composition, and very large displacements and forces can be realized from these photolithographically machinable materials [1][2][3][4][5][6][7]. It is not surprising then that considerable interest has developed in the use of such films as actuator materials for microelectromechanical systems (MEMS) and for highly miniaturized biomedical devices [8][9][10][11][12][13].…”

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confidence: 99%

Stress in Sputtered Films of Near-Equiatomic TiNiX on (100) Si: Intrinsic and Extrinsic Stresses and Their Modification by Thermally Activated Mechanisms

Grummon

Zhang

2001

phys. stat. sol. (a)

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The development of intrinsic and extrinsic stresses in TiNi and TiNiHf thin films, and their relaxation during isochronal and isothermal annealing, has been studied in both crystalline and amorphous materials sputtered onto (100) silicon. The development of intrinsic compressive stress was sensitive to both deposition pressure and temperature, and to film thickness, and was thermally stable below the deposition temperature. Kinetic parameters for isothermal stress relaxation and isothermal crystallization were determined. A two-stage process for both isochronal and isothermal stress relaxation was identified, with an initial stress change governed by a structural modification mechanism characterized by large activation volume and energy, giving way to a slower, diffusioncontrolled relaxation mechanism. Tensile stresses developed during isothermal crystallization were found to relax at rates that depended on deviation of the film composition from stoichiometry. The results are important with respect to the deployment of shape-memory thin films in microelectromechanical systems (MEMS), in which large extrinsic tensile stresses can be exploited to enable reversible high-energy mechanical actuation.

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