Characterization of TiNi shape-memory alloy thin films for MEMS applications

Thin film shape-memory alloys (SMAs) have been recognized as promising and high performance materials in the field of microelectromechanical systems ( MEMS) applications. In this investigation, chemical composition, microstruc ture and phase transformation behaviors of sputter deposited TiNi films wer e studied. The surface and cross-section morphology of the deposited coatin g was analyzed using atomic force microscopy (AFM) and scanning election mi croscopy (SEW The results from the differential scanning calorimeter (DSC) showed clearly the martensitic transformation upon heating and cooling. X-R ay diffraction analysis (XRD) also revealed the crystalline structure chang ing with temperature. By depositing TiNi films on the bulk micromachined Si cantilever structures, micro-beams exhibiting a good shape-memory effect w ere obtained. Finite element simulation results of the deformation of micro -beam (using the measured NiTi thin film parameters) agree quite well with the measured behavior. (C) 2001 Elsevier Science B.V. All rights reserved.