Crystallization and phase transformations in amorphous NiTi thin films for microelectromechanical systems

摘要: Amorphous sputtered nickel–titanium thin films were deposited onto micromachined silicon-nitride membranes and subjected to heating cooling conditions. Their associated microstructure was monitored directly simultaneously with in situ transmission electron microscopy. These electron-transparent constrained the NiTi rendered it possible for observation of complete transformation cycle, which includes: crystallization amorphous phase austenite (cubic B2 structure) heating; conversion (B2) martensite (monoclinic B19′ cooling. Electron micrographs show nucleation growth grains occurs at a temperature 470°C rate that indicates polymorphic transformation. The onset martensitic between 25 35°C. Calorimetric measurements are consistent observed crystallization.