Shape memory thin films formed with carrousel-type magnetron sputtering apparatus

Abstract

Ti–Ni thin films were deposited with a carrousel-type magnetron sputtering apparatus. This apparatus has a substrate holder rotating in the center and surrounded by independently controlled multiple targets. The films were prepared by simultaneous sputtering of a Ti–50 at.% Ni alloy target and a pure Ti target. Composition control was performed successfully and composition uniformity was observed over a large area along the rotation direction. Mechanical tests revealed that all the films possessed good mechanical properties and shape memory effect comparable to those of bulk alloys. This sputtering apparatus was also used to fabricate two kinds of bimorph-type micro actuators: a Ti–Ni film/Si substrate bimorph actuator and a Ti–Ni film/SiO2 film bimorph actuator. The curvature measurement during a thermal cycle showed a perfect shape memory effect of the former bimorph actuator. Micro devices with the latter bimorph actuators were fabricated and confirmed to work successfully. In particular, the feasibility of a micro robot capable of moving, with legs made of a shape memory thin film, was demonstrated in association with robustness of the shape memory thin film.