Implementation of hard magnetic thin films on suspended cantilevers for electromagnetic energy harvesters

Abstract

Microelectromechanical systems (MEMS) have found several applications in various fields from homeland security to personalized health care. However, rendering MEMS into autonomous wireless systems operating in any given environment requires the integration of energy harvesters into the MEMS structures, ensuring thus the self-powering of the devices. In this work, we investigated the mechanical and magnetic properties of Samarium Cobalt (SmCo) thin films, with the goal to implement them into electromagnetic energy harvesters. The films were deposited by sputtering on suspended silicon cantilevers fabricated with a front-side micromachining process. The magnetic films, grown under various pressures and thermally annealed at several temperatures and ambient conditions, were studied in terms of their mechanical and magnetic properties. Depending on the fabrication parameters, the stresses that developed in the magnetic material, deposited on top of the cantilevers, are altered from compressive (downward deflection of the cantilevers) to tensile (upward deflection), indicating that it is possible to control not only the magnetic properties of the films, but also the mechanical properties of the complete structure. Our results suggest that SmCo magnetic films are suitable candidates for integration in suspended structures for the development of electromagnetic micro-generators.