Fabrication and Characterization of the Li-Doped ZnO Thin Films Piezoelectric Energy Harvester with Multi-Resonant Frequencies.

Xiaofeng Zhao,Chunpeng Ai,Dianzhong Wen,Sen Li,Hongmei Liu

doi:10.3390/mi10030212

Abstract

A novel piezoelectric energy harvester with multi-resonant frequencies based on Li-doped ZnO (LZO) thin films is proposed in this paper, consisting of an elastic element with three (or more) different length cantilever beam arrays and a piezoelectric structure (Al/Li-doped ZnO/Pt/Ti). The LZO thin films of piezoelectric structure were prepared on Pt/Ti/SiO2/Si by using a radio frequency (RF) magnetron sputtering method under certain process conditions. When the LZO thin films were deposited with an LZO target concentration of 5 wt%, the piezoelectric coefficient d33 was 9.86 pm/V. Based on this, the energy harvester chips were fabricated on a <100> silicon substrate using micro-electromechanical systems (MEMS) technology, and its performance can be measured by fixing it to a printed circuit board (PCB) test substrate. The experimental results show that, when exerting an external vibration acceleration of 2.2 g and a vibration frequency of 999 Hz, the energy harvester can achieve a big load voltage of 1.02 V at a load resistance of 600 kΩ, and a high load power of 2.3 µW at a load resistance of 200 kΩ.

Highlights

It’s well known that vibration is common in the environment, such as motor operation vibration, bridge vibration, etc. [1,2]
Since the bottom electrode of the energy harvester chip is Pt/Ti, a Pt/Ti/SiO2/Si substrate was used to study the effect of Li doping concentrations on the crystal orientation, piezoelectric coefficient, and surface morphology of Li-doped ZnO (LZO) thin films
A novel LZO thin films piezoelectric energy harvester with multiple resonant frequencies was designed in this study

Summary

Introduction

It’s well known that vibration is common in the environment, such as motor operation vibration, bridge vibration, etc. [1,2]. The piezoelectric energy harvesters prepared using the above-mentioned piezoelectric materials have many disadvantages which limit their further development, such as their complicated fabricating process, poor compatibility with micro-electromechanical systems (MEMS) technology, and the need for external power sources. In 2014, Hu, et al presented a high power Co3O4/ZnO piezoelectric transducer with a multi-layer (Au/Co3O4/ZnO/Ti) thin film cantilever beam structure based on the magnetron sputtering method under optimized deposition conditions, achieving an output power 10.9 times higher than that of the ZnO piezoelectric transducer under the conditions of a load resistance of 100 kΩ and a low operating frequency of 37 Hz [5]. A Li-doped ZnO (LZO) thin films piezoelectric energy harvester with multi-resonant frequencies was designed, consisting of an elastic element with three (or more) different LZO length cantilever beam arrays and a piezoelectric structure (Al/Li-doped ZnO/Pt/Ti). This study lays the foundation for preparing a multi-resonant frequencies energy harvester

Basic Structure

Fabrication Technology

Results and Discussion

Characteristics of the Energy Harvester

Conclusions