Demonstration of high-performance piezoelectric MEMS vibration energy harvester using BiFeO3 film with improved electromechanical coupling factor

Abstract

The present study reports the improvement of piezoelectric properties of sputtered BiFeO3 films, and application to piezoelectric MEMS vibration energy harvesters (MEME-pVEHs). (100)-oriented BiFeO3 films were obtained on (100)-oriented LaNiO3 bottom electrodes grown on (100) Si substrates at deposition temperatures ranging from 450 °C to 550 °C. While all the films showed well-defined ferroelectric hysteresis loops at room temperature, the highest e31,f coefficient of −3.6 C/m2 was obtained at 500 °C. The increase of the e31,f coefficient with increasing of the Rayleigh constant indicates the domain wall substantially contributes to the piezoelectric properties of the BiFeO3 films. MEMS-pVEHs measuring 1 × 6 mm2 and Si proof mass of 3.0 mg were fabricated using the BiFeO3 film. The resonance frequency, electromechanical coupling factor, and mechanical quality factor were determined as 151.2 Hz, 0.1%, and 850, respectively. The maximum output power was 2.4 μW at 0.3 G, which is comparable with that of the best-performing MEMS-pVEHs using Pb(Zr,Ti)O3 films.