Effect of Substrate Temperature on the Shape Memory Behavior of Ti-Ni-Cu Ternary Alloy Sputtered Films

摘要

The purpose of this work is to establish a deposition process of Ti-Ni-Cu films showing shape memory effect in the as-deposited state. 5-μm-thick Ti_(50)Ni_(35)Cu_(15) films have been deposited onto thermally oxidized (001) Si wafer by triple-source dc magnetron sputtering at various substrate temperatures. Their shape memory behavior were characterized by XRD, DSC measurements and thermal cycling tests under various constant tensile stresses. We have confirmed that crystalline films can be grown directly when the substrate temperature exceeds 400°C. The films deposited at higher than 450°C showed thermoelastic martensitic transformation and their M_s temperature slightly increased with increasing substrate temperature. Since their M_s temperature were found to be higher than 30°C, they can be used as an actuator at RT. These films were also found to have higher critical stress against plastic deformation than the post-deposition crystallized films. We have also tried to fabricate a prototype of micro-actuator and to characterize their actuation behavior and have confirmed that TiNiCu/SiO_2 double layered diaphragm showed an actuation response to a pulsed current of more than 100Hz.