Composition control of NiTi shape memory alloy films formed by sputter deposition with a composite target

In order to obtain NiTi films by magnetron sputtering, the authors devised a target composed of Ti and Ni rings and a Ti disk. The fabricated films were analyzed by energy-dispersive X-ray analysis (EDX) and Rutherford backscattering spectrometry (RBS). X-ray diffraction measurements (XRD) of the films were also carried out. It was shown that the composition of the film formed with the target was easily controlled with an accuracy of 0.5 at.% by changing the electric current flowing through the solenoid coil of an electromagnet. The composition of the film was affected by the Ar gas pressure, It was also shown that a film with an in-depth composition gradient was easily formed. The obtained films were confirmed by a bending test to show the shape memory effect.