Fabrication and performance of ZnO piezoelectric cantilever for vibration energy harvesting

Zinc oxide (ZnO) thin film piezoelectric cantilevers were fabricated and characterized in this work The ZnO film was deposited by RF magnetron sputtering system under optimized deposition parameters at room temperature. The XRD pattern of the ZnO film showed that it has a highly preferred c-axis orientation. The cross-sectional FE-SEM picture of the ZnO film indicates that the columnar growth of ZnO film is perpendicular to the substrate surface. The AFM images of the ZnO film indicate that its surface is very smooth and the surface roughness is 6.024nm. The dynamic performance of the ZnO piezoelectric cantilever was characterized by impedance analyzer and laser Doppler vibrameter. The resonant frequencies of the piezoelectric cantilever are 24988Hz and 25031Hz measured by impedance analyzer and LDV, respectively. The calculated transverse piezoelectric constant d₃₁ of the ZnO film is -3.21pC/N. A ZnO thin film micro piezoelectric vibration energy harvester is fabricated and characterized at last. The tested results show that the maximal load voltage is 1.77V under load resistance of 1MΩ and the largest load power is 0.98μW under load resistance of 0.38MΩ when the ZnO energy harvester is excited by vibration with 1300Hz frequency and 10m/s² acceleration.