ScAlN MEMS Cantilevers for Vibrational Energy Harvesting Purposes

Abstract

Piezoelectric energy harvesting offers the possibility to make use of ambient vibrations most beneficially to feed low power sensor nodes. This paper demonstrates the fabrication and characterization of piezoelectric cantilevers with AlN and Sc <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> N (x = 27%) thin films for the evaluations of their energy harvesting performance. The characterization mainly focuses on the measurement of the output power at variable load resistance to achieve maximum power output. Superior properties of ScAlN thin films for energy harvesting compared with AlN films are confirmed. Furthermore, an analytical model is employed to extract material parameters for ScAlN. High piezoelectric coefficients e <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> = 1.6 C/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> = 6.9 pm/V are determined for ScAlN. Finally, a proof mass is attached to further increase the output power at optimized load resistance.