Al2O3 and Pt Atomic Layer Deposition for Surface Modification of NiTi Shape Memory Films

Abstract

Pt coatings on NiTi film micro-actuators and/or sensors can add some useful properties, e.g., they may improve the NiTi anticorrosion and thermomechanical characteristics or activate surface properties beneficial for a specific application (e.g., functionalized surfaces for biomedical applications). Pt coatings prepared via atomic layer deposition (ALD) may help reduce cost due to the nanometric thickness. However, no authors have reported preparation of Pt ALD coatings on NiTi films, perhaps due to the challenge of the concurrent NiTi film oxidation during the Pt ALD process. In the present study, Al2O3 and Pt ALD coatings were applied to NiTi thin films. The ALD coating properties were studied using electron and atomic force microscopies and X-ray photoelectron spectroscopy (XPS). Potential structural changes of NiTi due to the ALD process were evaluated using electron microscopy and X-ray diffraction. The presented ALD process resulted in well-controllable preparation of Pt nanoparticles on ultrathin Al2O3 seed layer and a change of the transformation temperatures of the NiTi films.