CO2 laser annealing with NiTi thin films deposited by sputtering

It has been proved that NiTi shape memory alloy thin film is the best one for micro actuators as compared with the others, e.g., electrostatic, electromagnetic and piezoelectric thin films. If the deposition of NiTi thin films on silicon wafers is carried out at room temperature, the resultant thin films are normally amorphous without shape memory. Subsequent annealing in a high vacuum chamber is required for re-crystallization. In this paper, we present an alternative annealing approach, namely by CO2 laser. After laser annealing, optical microscope, X-ray diffraction (XRD) and atomic force microscope (AFM) were applied to characterize the NiTi thin films. Strong austenite/martensite lattice structures were observed by XRD. The relationship between the surface roughness of the annealed NiTi thin film and temperature was obtained using AFM. The results indicate that the CO2 laser annealed NiTi thin films are with shape memory.