A microstructural map of crystallized NiTi thin film derived from in situ TEM methods

Sputtered-deposited nickel titanium thin films are commonly amorphous when synthesized and require annealing to crystallize them. The resulting microstructures, which are governed by nucleation and growth kinetics, dictate the actuation properties. The evolution of these microstructures was studied using in situ transmission electron microscopy (TEM) heating methods. The experimentally-determined kinetic values of nucleation and growth were inserted into a mathematical expression derived from the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory, which predicts the average grain size over a broad range of temperatures.