Interfacial adhesion evaluation of magnetostrictive thin films applying electrochemical hydrogen loading technique

Inhalt:
Magnetostrictive materials are widely used to build actuators, sensors, and vibration energy harvesting devices. Generally, the interfacial adhesion between the substrate and thin films can be a quite important factor from the practical point of view. Therefore, establishing precise techniques to evaluate the interfacial adhesion energy are quite important as basic technologies in the applications. In this study, we focused on the in-plane stress control by tuning the hydrogen content via electrochemical hydrogen loading. The step-by-step electrochemical hydrogen loading was done for Sm- Fe films and the in-plane stress was evaluated from the curvature at each equilibrium state, applying the Stoney’s equation. It was confirmed that the in-plane stress increased in the compression direction by adding hydrogen to the sample. In some sample, film delamination phenomenon (buckling) was observed as the compressive stress was released. The adhesion energy between the magnetostrictive thin films and the substrate was evaluated by applying Nikitin’s model from the change of energy stare before and the buckling.