Research On ZnO Piezoelectric Thin Film Energy Harvester Based On MEMS Technology

To improve the application of energy harvester in multi-frequency point,the ZnO piezoelectric thin films energy harvester is designed based on micro-electro-mechanical system?MEMS?technology in this paper,which consists of a silicon cantilever beam array with mass and a piezoelectric structure.In order to realize multi-frequency point energy collection,three cantilever beams with the same beam width,beam thickness and different beam lengths are used as the elastic component for picking up the vibration signal.The three-layer films composed of Pt/Ti bottom electrode,Li-doped ZnO thin films piezoelectric layer and Al top electrode is used as the piezoelectric structure to realize the conversion of vibration energy and electric energy.When the external environment is vibrated,the upper and lower electrodes of the energy harvester generate electrical signals,which can achieve energy collection at a certain vibration frequency.In order to effectively improve the performance of the energy harvester,the Li-doped ZnO piezoelectric thin films were prepared by radio frequency magnetron sputtering method.By X-ray diffraction?XRD?,scanning electron microscopy?SEM?,X-ray photoelectron spectroscopy?XPS?,atomic force.Microscopy?AFM?and piezoelectric response force microscopy?PFM?were used to study the optimized preparation conditions of ZnO thin films.The results show that the 5wt%Li-doped ZnO thin films have a good c-axis preferred orientation,and the piezoelectric coefficient d₃₃ is about 9.86 pm/V,meanwhile,the resistivity is about 45.22 k?·cm.The ANSYS and COMSOL software were used to construct the energy harvester simulation model,and the static mechanical characteristics and piezoelectric characteristics of the energy harvester were analyzed.The chip layout design was completed by L-Edit software.Based on these,the ZnO piezoelectric thin films energy harvester chip is fabricated and packaged.At room temperature,this paper used the built energy harvester test system to test the characteristics of the chip.The results show that the resonant frequencies of energy harvester with a mass of 3.08 mg are 999 Hz,1210 Hz and 1276 Hz,respectively.When exerting an ambient vibration acceleration of 2.2 g and a vibration frequency of 999 Hz,the maximum output voltage of the energy harvester is 1.02 V at a load resistance of 600k?when the upper and lower electrodes are connected in series.The maximum output power of energy harvester is 5.04?W at a load resistance of 40 k?when the upper and lower electrodes are connected in parallel.This structure realizes the collection of environmental vibration energy.