Structural characterisation of NiTi thin film shape memory alloys

NiTi shape memory alloy thin film sensor micro-array for detection of infrared radiation

“…In addition, there were peaks at 2θ = (43.5 • , 77.9 • , 92.7 • ), which correspond to the Ni 3 Ti(0 0 4) and Ni 3 Ti(2 1 6) planes, respectively. This suggests the presence of Ni 3 Ti precipitates which could be formed during high temperature aging [3] in the NiTi thin film.…”

Characterization of Sputtered Nickel-Titanium (NiTi) Stress and Thermally Actuated Cantilever Bimorphs Based on NiTi Shape Memory Alloy (SMA)

“…1 A small change of even 1 atomic percent (at. %) near the equiatomic composition can shift the phase change by as much as 100 °C.…”

“…6,[9][10][11][12][13][14][15] Sputtering is the best option for depositing NiTi thin films because the conventional vacuum evaporation of NiTi leads to the potential problem of difference in evaporation rate due to difference in vapor pressure, thus making composition control more difficult. 1 One of the techniques used for sputtering NiTi onto silicon (Si) wafers is simultaneous cosputtering from a Ni50Ti50 alloy and pure Ti targets. It was noted quite early that the composition of sputtered films from a NiTi target does not match the composition of the target, but rather ends up being Ti deficient.…”

“…This is because it delivers a large output force per unit volume, works as both a functional and structural element, can be actuated electrically or thermally, and shows both thermal and mechanical shape memory. [1][2][3][4] Out of the many different potential SMAs, nickeltitanium (NiTi) and nickel-titanium-copper (NiTiCu) based alloys have been proven as being both commercially practical and having useful engineering properties. 3 However, since Cu-based alloys are brittle in polycrystalline states, most MEMS applications focus on using NiTi-based alloys.…”

“…2 NiTi thin films for MEMS applications compared to other actuation mechanisms such as thermal, magnetic, or electrostatic are more useful because of their high power density, actuation force, and large displacement, and high work output per volume. 1,5 The basic phenomenon of the shape memory effect is the phase transition between a low temperature, low symmetry martensite phase and the relatively high temperature, high symmetry austenite phase, which is a reversible process. 6 During heating, a significant increase in stress is present due to the change from martensite to austenite.…”