Fabrication Technology and Characteristics Research of the Acceleration Sensor Based on Li-Doped ZnO Piezoelectric Thin Films

Abstract

An acceleration sensor based on piezoelectric thin films is proposed in this paper, which comprises the elastic element of a silicon cantilever beam and a piezoelectric structure with Li-doped ZnO piezoelectric thin films. The Li-doped ZnO piezoelectric thin films were prepared on SiO2/Si by radio frequency (RF) magnetron sputtering method. The microstructure and micrograph of ZnO piezoelectric thin films is analysed by a X-ray diffractometer (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and piezoresponse force microscopy (PFM), respectively. When the sputtering power of 220 W and Li-doped concentration of 5%, ZnO piezoelectric thin films have a preferred (002) orientation. The chips of the sensor were fabricated on the <100> silicon substrate by micro-electromechanical systems (MEMS) technology, meanwhile, the proposed sensor was packaged on the printed circuit board (PCB). The experimental results show the sensitivity of the proposed sensor is 29.48 mV/g at resonant frequency (1479.8 Hz).

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

“…In Figure 5, the most intense peak belongs to the ZnO (002) plane, indicating the (002) diffraction peak position has been modulated with the increase in Li doping concentrations. At 34.44°, the (002) diffraction peak of the LZO thin films deposited with an LZO target concentration of 5 wt% is close to the characteristic diffraction peak of ZnO [27,28,29]. The weak (100) and (101) diffraction peaks of ZnO mean that the crystallinity of the sample is not high at this time.…”

Fabrication and Characteristic of a Double Piezoelectric Layer Acceleration Sensor Based on Li-Doped ZnO Thin Film

“…Based on the elastic mechanism analysis of the cantilever beam [29], the stress σ of the cantilever beam is σ=6Fwchc2lc…”

“…As a third-generation semiconductor with advantages, including a wide band gap [16], high transmittance [17], nontoxicity [18], and high radiation hardness [7], ZnO has a wide range of applications in gas sensors [19,20,21], nanogenerators [22,23,24,25], data storage (memory) application [26,27], and acceleration sensors [11,28,29]. Compared with other piezoelectric materials, in addition to its nontoxicity, ZnO is also compatible with the integrated circuit (IC) process [30].…”

“…Meanwhile, acceleration sensors fabricated by MEMS technology have the advantages of miniaturization, integration, and easy packaging. At the same time, the piezoelectric constant of pure ZnO is limited, and it can be enhanced by doping Li impurities [29]. In order to improve the performance of the device, a multi-piezoelectric layer structure has been reported.…”

“…In our previous work, we designed a ZnO acceleration sensor based on a single piezoelectric layer cantilever structure by doping Li atoms as impurities to increase the resistivity of the ZnO thin film, thereby enhancing its piezoelectric characteristics. The sensitivity could reach 29.48 mV/g [29], based on the above reports [32,33,34]. In order to improve the voltage sensitivity of the acceleration sensor, a series structure double piezoelectric layer acceleration sensor based on the piezoelectric effect of the Li-doped ZnO thin film was designed, fabricated, and analyzed in this study.…”