Characterization of sputtering deposited NiTi shape memory thin films using atemperature controllable atomic force microscope

Abstract

NiTi shape memory thin films are potentially desirable for micro-electro-mechanical system(MEMS) actuators, because they have a much higher work output per volume and also asignificantly improved response speed due to a larger surface-to-volume ratio. A newtechnique using a temperature controllable atomic force microscope (AFM) is presentedin order to find the transformation temperatures of NiTi shape memory thinfilms of micrometer size, since traditional techniques, such as differential scanningcalorimetry (DSC) and the curvature method, have difficulty in dealing with samples ofsuch a scale as this. This technique is based on the surface relief phenomenon inshape memory alloys upon thermal cycling. The reliability of this technique isinvestigated and compared with the DSC result in terms of the transformation fraction(ξ). It appears that the new technique is nondestructive, in situ and capable of characterizingsputtering deposited very small NiTi shape memory thin films.