Sputter-Deposited Shape-Memory Alloy Thin Films: Properties and Applications

MRS Bulletin ◽  
2002 ◽  
Vol 27 (2) ◽  
pp. 111-114 ◽  
Author(s):  
Akira Ishida ◽  
Valery Martynov
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Microelectromechanical Systems ◽  
Sputter Deposition ◽  
Bulk Materials ◽  
Shape Memory Actuators ◽  
Sputter Deposited ◽  
Memory Characteristics

AbstractShape-memory alloy (SMA) thin films formed by sputter deposition have attracted considerable attention in the last decade. Current intensive research demonstrates that unique fine microstructures are responsible for the superior shape-memory characteristics observed in thin films as compared with bulk materials. Simultaneously, much effort has been undertaken to develop and fabricate micro devices actuated by SMA thin films. This article reviews the research to date on shape-memory behavior and the mechanical properties of SMA thin films in connection with their peculiar microstructures. Promising applications such as microvalves are demonstrated, along with a focused discussion on process-related problems. All of the results indicate that thin-film shape-memory actuators are ready to contribute to the development of microelectromechanical systems.

Quantitative phase transformation behavior in TiNi shape memory alloy thin films

2004 ◽  
Vol 19 (10) ◽  
pp. 2822-2833 ◽  
Author(s):  
Bo-Kuai Lai ◽  
H. Kahn ◽  
S.M. Phillips ◽  
Z. Akase ◽  
A.H. Heuer
Keyword(s):  
Thin Films ◽  
Shape Memory Alloy ◽  
Residual Stresses ◽  
Shape Memory ◽  
Microelectromechanical Systems ◽  
Rietveld Analysis ◽  
Phase Fraction ◽  
Temperature Hysteresis ◽  
Noticeable Effect ◽  
Heating And Cooling

Phase transformations in near-equiatomic TiNi shape memory alloy thin films were studied, and the phase fraction evolutions were quantitatively correlated to the stress and resistivity of the films. TiNi thin films with compositions of 50.1, 51.1, and 51.7 at.% Ti all exhibited transformation temperatures between 65 and 100 °C, low residual stresses at room temperature (RT), and high recoverable stresses, thus making them suitable for microactuators in microelectromechanical systems. Low residual stresses at RT, less than 50 MPa, can be obtained even when only a small quantity of martensite, less than 30%, is present. Phase fraction evolution during complete thermal cycles (heating and cooling) was studied using elevated temperature x-ray diffraction, combined with quantitative Rietveld analysis. R-phase always appeared in these near-equiatomic TiNi thin films during cooling but did not have a noticeable effect on the stress–temperature hysteresis curves, which mainly depend on the phase fraction evolution of martensite. On the other hand, the occurrence of R-phase determined the variation of film resistivity. Martensite, austenite, and R-phase coexisting within a single grain were observed using transmission electron microscopy.

Characterization of shape-memory alloy thin films made up from sputter-deposited Ni/Ti multilayers

2000 ◽  
Vol 48 (16) ◽  
pp. 4065-4071 ◽  
Author(s):  
T Lehnert ◽  
H Grimmer ◽  
P Böni ◽  
M Horisberger ◽  
R Gotthardt
Keyword(s):  
Thin Films ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Sputter Deposited

The Fabrication of Thin Film NiTi Shape Memory Alloy Micro Actuator for MEMS Application

1999 ◽  
Author(s):  
John J. Gill ◽  
Ken Ho ◽  
Gregory P. Carman
Keyword(s):  
Thin Film ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Microelectromechanical Systems ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
Niti Shape Memory Alloy ◽  
Cylindrical Shape ◽  
Finish Temperature

Abstract Thin film SMA (Shape memory alloy) is a useful method for MEMS (Microelectromechanical Systems) actuator. This is because the thin film has an improved frequency response compared to bulk SMA, high work density, and produces large strain. A novel two-way thin film NiTi (Nickel Titanium) shape memory alloy actuator is presented in this paper. Thin film shape memory alloy is sputter-deposited onto a silicon wafer in an ultra high vacuum system. Transformation temperatures of the deposited NiTi film are measured by residual stress measurement at temperatures from 25 ° C to 120 ° C. Test results show that the Mf (Martensite Finish Temperature) is around 60 ° C and Af (Austenite Finish Temperature) is around 110 ° C. A free standing NiTi membrane (10 mm × 10mm and 3 μm thick) is fabricated using MEMS technology. We found that a mixture of HF (Hydro Fluidic Acid), HNO3 (Nitric Acid) and DI (Deionized) water with thick photo resist mask works best for the fabrication process. The membrane is hot-shaped in different shapes such as dome shape, pyramidal shape, and cylindrical shape. Results indicate that when the temperature of the NiTi film exceeds Af, the NiTi membrane transforms into the trained hot-shape. When the temperature cools down to room temperature, the membrane returns to the initial flat shape.

Thin Film NiTi Shape Memory Alloy Microactuator With Two-Way Effect

2000 ◽  
Author(s):  
John J. Gill ◽  
Gregory P. Carman
Keyword(s):  
Thin Film ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Frequency Response ◽  
Microelectromechanical Systems ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
Niti Shape Memory Alloy ◽  
Maximum Deflection

Abstract Thin film SMA (Shape memory alloy) is a useful material for MEMS (Microelectromechanical Systems) actuator. This is because the thin film has an improved frequency response compared to bulk SMA, high work density, and produces large strain. A novel two-way thin film NiTi (Nickel Titanium) shape memory alloy actuator is presented in this paper. Thin film shape memory alloy is sputter-deposited onto a silicon wafer in an ultra high vacuum system. Transformation temperatures of the NiTi film are determined by measuring the residual stress as a function of temperature. Test results show that the Martensite-Temperature-Finish (Mf) is approximately 60° C, and the Austenite-Temperature-Finish (Af) is 110° C. A free standing NiTi membrane (12 mm × 12 mm and 2.5 μm thick) is fabricated using MEMS technology. We found that a mixture of HF (Hydro Fluoric Acid), HNO3 (Nitric Acid) and DI (Deionized) water with thick photo resist mask works best for the fabrication process. The membrane is hot-shaped into a dome shape. Results indicate that when the temperature of the NiTi film exceeds Af, the NiTi membrane transforms into the trained hot-shape. When the temperature cools down to room temperature, the membrane returns to the initial flat shape. The performance of the SMA micro actuator is characterized with a laser measurement system for deflection vs. input power and frequency response. The maximum deflection of SMA microactuator is 230 μm. The corresponding frequency responses at the maximum deflection are 30 Hz with Copper (Cu) block placed underneath the microactuator and less than 1 Hz when Plexi-glass is placed.

Characteristics of Sputter-Deposited Ti–Ni–Cu Shape Memory Alloy Thin Films

2018 ◽  
Vol 10 (7) ◽  
pp. 974-978
Author(s):  
Munkhbayar Baatarsuk ◽  
Hyeon-Woo Joo ◽  
Joo-Hyeon Bae ◽  
Sun-Chul Huh ◽  
Gyu-Bong Cho ◽  
...  
Keyword(s):  
Thin Films ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Sputter Deposited
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