Si Proof Mass Research Articles

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

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.

Piezoelectric MEMS with multilayered Pb(Zr,Ti)O3 thin films for energy harvesting

This study aims to report the design of high-performance piezoelectric MEMS energy harvesters using a full batch MEMS-fabrication process with a Si proof mass and multilayered Pb(Zr,Ti)O3 (PZT) thin films without bonding of a proof mass and/or bulk piezoelectric ceramics. These devices contain sputtered multilayered PZT thin films with internal metal electrodes as a thick energy-conversion layer. The thickening of the piezoelectric layer by multilayer sputter deposition technique enabled the batch fabrication of high-performance piezoelectric MEMS harvesters. These fabricated device with the footprint of 10 × 10 mm2 was found to provide a high output power of 53.7 μW per gravitational acceleration. These results are expected to be useful for the future development of alternatives to batteries for autonomous sensor systems.

FBAR-on-diaphragm type electro-acoustic resonant micro-accelerometer: a theoretical study

We presented a theoretical study of the performance of a novel FBAR-on-diaphragm sensor-head structure for the FBAR-based electro-acoustic resonant micro-accelerometer. This structure overcomes disadvantages in the FBAR-beam structure for its limited cantilever beam thickness, and deficiencies in the embedded-FBAR structure for its complex micro-fabrication process. Its elastic diaphragm is made of silicon dioxide (SiO2)/silicon nitride (Si3N4) bilayer film, which is not only more susceptible to the IC compatible integration process for the Si-based microstructure and the FBAR, but also improves sensitivity and temperature stability of the BAW accelerometer. FBAR-on-diaphragm type BAW accelerometer integrates the acceleration sensing structure, i.e., the SiO2/Si3N4 bilayer diaphragm and the Si proof-mass, with the AlN FBAR electro-acoustic transducer. Preliminary performance analysis on FBAR-on-diaphragm type BAW accelerometer suggests that the FBAR-on-diaphragm structure is feasible. We obtained modal frequencies of the FBAR-on-diaphragm structure and stress distribution of the diaphragm under 0---100 g acceleration loads through the finite element modal analysis and static simulation, Applying the calculated maximum stress to the piezoelectric film in FBAR for qualitative analysis, and combining the dependency of elastic coefficient on stress in the Wurtzite AlN film calculated with the first-principle method, we roughly predicted the maximum elastic coefficient variation in the Wurtzite AlN film under different acceleration load. With the help of the RF simulation software ADS, we changed the longitudinal wave velocity corresponding to the elastic constants with variant acceleration loads. By comparing the resulted resonant frequencies of the sensor head without and with different acceleration loads, we qualitatively characterized its frequency shift and sensitivity. In our study, we gave further analysis of the simulation results. It reveals that the first-order modal frequency of the SiO2/Si3N4 circular diaphragm is quite far away from the higher ones, which means less cross modal coupling. It also reveals that under the acceleration load, its resonant frequency with a quite linear acceleration---frequency shift characteristic will up-shift with the sensitivity of several KHz/g.

Activation of piezoelectric property of PZT thin films by pulse poling

We have demonstrated the pulse poling technique to activate the piezoelectric property of PZT thin films within 1 second. We have fabricated piezoelectric microcantilevers with Si proof mass using Pb(Zr0.52,Ti0.48)O3 (MPB-PZT) thin films. By applying 1 kHz and 100 V of unipolar triangle pulse voltage, the positive piezoelectric constant |d31| of PZT thin film has been enhanced as high as 95 pm/V, which is larger than dc poled PZT thin films (67 pm/V).

A hybrid micro vibration energy harvester with power management circuit

In this paper, a hybrid micro vibration energy harvester based on piezoelectric and electromagnetic transduction mechanisms is developed and tested, which improves total output power and voltage in low frequency and small amplitude vibration environment. It contains a MEMS piezoelectric (PZT) cantilever array with an integrated Si proof mass, an NdFeB magnet attached to the free end of the cantilever beam, and one multi-layer micro coil fabricated using standard PCB technology placed on the fixed bottom. A mathematical model is established to calculate the output power from the hybrid energy harvester. The optimum size of the device’s structure is obtained based on the finite element analysis. Experimental test results show that the maximum output power of 40.62μW can be drawn from the hybrid energy harvester with the optimal load resistance under the vibration of 0.2g acceleration at the resonant frequency of 55.9Hz. The more power output can be generated than a stand-alone piezoelectric or electromagnetic device, and the output voltage is increased by using the MEMS PZT cantilever array architecture. In order to regulate the output voltage of energy transducer, a low power consumption power management circuit integrated with AC–DC rectifier and DC–DC buck converter is designed and applied in wireless sensor nodes. The test results prove that the hybrid energy harvester can provide a stable output power supply voltage of 3.6V for wireless sensor node.

Fabrication and characterization of vibration-driven AlN piezoelectric micropower generator compatible with complementary metal-oxide semiconductor process

This article describes the aluminum nitride (AlN)-based piezoelectric microgenerator for scavenging energy from ambient vibration. To achieve the low resonance frequency and maximize power density, a parametric study has been carried out by analytical modeling and finite element analysis. The piezoelectric microgenerator consists of AlN piezoelectric thin film with molybdenum (Mo) electrodes and silicon (Si) proof mass. The AlN was deposited on silicon-on-insulator wafer which is used as an insulating layer to defend the leakage current. The Mo electrode provides the excellent c-axis crystal growth of AlN. The fabricated AlN piezoelectric microgenerator can generate up to 6.4 nW at a frequency of 389 Hz and acceleration of 1.0 g (1 g = 9.81 m/s2). In addition, the output voltage and power density are 22.6 mVrms and 11.3 nW/mm3, respectively. The proposed generator is highly suitable for batch processing and has the possibility of harvesting energy from the ambient vibration.

A Vibration-Based MEMS Piezoelectric Energy Harvester and Power Conditioning Circuit

This paper presents a micro-electro-mechanical system (MEMS) piezoelectric power generator array for vibration energy harvesting. A complete design flow of the vibration-based energy harvester using the finite element method (FEM) is proposed. The modal analysis is selected to calculate the resonant frequency of the harvester, and harmonic analysis is performed to investigate the influence of the geometric parameters on the output voltage. Based on simulation results, a MEMS Pb(Zr,Ti)O3 (PZT) cantilever array with an integrated large Si proof mass is designed and fabricated to improve output voltage and power. Test results show that the fabricated generator, with five cantilever beams (with unit dimensions of about 3 × 2.4 × 0.05 mm3) and an individual integrated Si mass dimension of about 8 × 12.4 × 0.5 mm3, produces a output power of 66.75 μW, or a power density of 5.19 μW·mm−3·g−2 with an optimal resistive load of 220 kΩ from 5 m/s2 vibration acceleration at its resonant frequency of 234.5 Hz. In view of high internal impedance characteristic of the PZT generator, an efficient autonomous power conditioning circuit, with the function of impedance matching, energy storage and voltage regulation, is then presented, finding that the efficiency of the energy storage is greatly improved and up to 64.95%. The proposed self-supplied energy generator with power conditioning circuit could provide a very promising complete power supply solution for wireless sensor node loads.

Design and Fabrication of Vibration Based Energy Harvester Using Microelectromechanical System Piezoelectric Cantilever for Low Power Applications

We fabricated dual-beam cantilevers on the microelectromechanical system (MEMS) scale with an integrated Si proof mass. A Pb(Zr,Ti)O3 (PZT) cantilever was designed as a mechanical vibration energy-harvesting system for low power applications. The resonant frequency of the multilayer composition cantilevers were simulated using the finite element method (FEM) with parametric analysis carried out in the design process. According to simulations, the resonant frequency, voltage, and average power of a dual-beam cantilever was 69.1 Hz, 113.9 mV, and 0.303 microW, respectively, at optimal resistance and 0.5 g (gravitational acceleration, m/s2). Based on these data, we subsequently fabricated cantilever devices using dual-beam cantilevers. The harvested power density of the dual-beam cantilever compared favorably with the simulation. Experiments revealed the resonant frequency, voltage, and average power density to be 78.7 Hz, 118.5 mV, and 0.34 microW, respectively. The error between the measured and simulated results was about 10%. The maximum average power and power density of the fabricated dual-beam cantilever at 1 g were 0.803 microW and 1322.80 microW cm(-3), respectively. Furthermore, the possibility of a MEMS-scale power source for energy conversion experiments was also tested.

MEMS 공정을 통한 마이크로 Pb(Zr,Ti)O3박막 압전 외팔보 에너지 수확소자의 제작 및 특성 연구

In this study, we fabricated a micro <TEX>$Pb(Zr,Ti)O_3$</TEX> (PZT) film piezoelectric cantilever with a Si proof mass and dual beams through MEMS process. The size of the beam and the integrated Si proof mass were about <TEX>$4,320{\mu}m{\times}290{\mu}m{\times}12{\mu}m$</TEX> and <TEX>$1,380{\mu}m{\times}880{\mu}m{\times}450{\mu}m$</TEX> each. To reduce the air damping and have the larger displacement of dual beams was used for design. After mounting micro PZT film piezoelectric cantilever on shaker, we measured the resonance frequency and a output voltage while making resonant frequency changed. The resonant frequency and the highest average power of the cantilever device were 110.2 Hz and 0.36 <TEX>${\mu}W$</TEX> each, at 0.8 g acceleration and 23.7 <TEX>$k{\Omega}$</TEX> load resistance, respectively.

Micromachining of a Bimorph Pb(Zr,Ti)O3 (PZT) Cantilever Using a Micro-Electromechanical Systems (MEMS) Process for Energy Harvesting Application Moonkeun Kim, Beomseok Hwang, Jaehwa Jeong,

We designed and fabricated a bimorph Pb(Zr,Ti)O3 (PZT) cantilever with an integrated Si proof mass to obtain a low resonant frequency for an energy harvesting application. The cantilevers were fabricated on the micro-electromechanical systems (MEMS) scale. A mode of piezoelectric conversions were d31 and d33 mode in cantilever vibration Therefore, we designed and fabricated a single cantilever with d31 unimorph, d31 bimorph, d33 unimorph, and d33 bimorph modes. Finally, we fabricated a device with beam dimensions of about 5,400 microm x 480 microm x 14 microm (< +/- 5%), and an integrated Si proof mass with dimensions of about 1,481 microm x 988 microm x 450 microm (< +/- 5%). In order to measure the d31 and d33 modes, we fabricated top and bottom electrodes. The distance between the top electrodes was 50 microm and the resonant frequency was 89.4 Hz. The average powers of the d31 unimorph, d31 bimorph, d33 unimorph, and d33 bimorph modes were 3.90, 9.60, 21.42, and 22.47 nW at 0.8 g (g = 9.8 m/s2) and optimal resistance, respectively.

Non-Lead Based Piezoelectric Thin Films: Materials and Energy Harvesting Device

Non-lead based piezoelectric thin films of (K,Na)(Nb,Ta)O3–BiFeO3 (NKNT-BF) were successfully fabricated by the chemical solution deposition method. Small concentration of BF (5 mol %) added into NKNT films led to a fully dense microstructure and enhanced dielectric and piezoelectric properties compared to pure NKNT films. The measured dielectric constant and piezoelectric d33 values were around 575 and 50 pC/N, respectively. A thin film NKNT-BF piezoelectric cantilever with a micromachined Si proof mass was fabricated for a low frequency vibration energy harvesting device. The average power and the power density of NKNT-BF energy harvesting cantilever with the device volume of 0.007 cm3 were 1.82 μW and 260 μW/cm3 at the resonance frequency of 130 Hz and the acceleration of 0.75 G. Even if these values were somewhat inferior to those of the conventional PZT energy harvesting device, NKNT-BF thin film provided the promising results as an alternative material of PZT for the piezoelectric MEMS applications in the future.

Design and Fabrication of a PZT Cantilever for Low Frequency Vibration Energy Harvesting

In this study, a PZT cantilever with a Si proof mass is designed and fabricated for a low frequency energy harvesting application. A mathematical model of a multi-layer composite beam was derived and applied in a parametric analysis of the piezoelectric cantilever. Finally, the dimensions of the cantilever were determined for the resonant frequency of the cantilever. Our cantilever design was based on MATLAB and ANSYS simulations. For this simulation, the proof mass volumes were varied from 0 to 0.5 mm3 and resonant frequencies were calculated from 833.5 Hz to 125.5 Hz, respectively. Based on simulation, we fabricated a device with beam dimensions of about 4.10 mm x 0.48 mm x 0.012 mm, and an integrated Si proof mass with dimensions of about 0.481 mm x 0.48 mm x 0.45 mm. The resonant frequency, maximum peak voltage, and highest average power of the cantilever device were 224.8 Hz, 4.8 mV, and 2.24 nW, respectively.

MEMS 공정을 이용한 마이크로 PZT 외팔보 에너지 수확소자의 제작 및 특성

In this work, we designed and fabricated a multilayer thin film Pb(Zr,Ti)<TEX>$O_3$</TEX> cantilever with a Si proof mass for low frequency vibration energy harvesting applications. A mathematical model of a mu lti-layer composite beam was derived and applied in a parametric analysis of the piezoelectric cantilever. Finally, the dimensions of the cantilever were determined for the resonant frequency of the cantilever. W e fabricated a device with beam dimensions of about 4,930 <TEX>${\mu}M$</TEX> <TEX>${\times}$</TEX> 450 <TEX>${\mu}M$</TEX> <TEX>${\times}$</TEX> 12 <TEX>${\mu}M$</TEX>, and an integrated Si proof mass with dimensions of about 1,410 <TEX>${\mu}M$</TEX> <TEX>${\times}$</TEX> 450 <TEX>${\mu}M$</TEX> <TEX>${\times}$</TEX> 450 <TEX>${\mu}M$</TEX>. The resonant frequency, maximum peak voltage, and highest average power of the cantilever device were 84.5 Hz, 88 mV, and 0.166 <TEX>${\mu}Wat$</TEX> 1.0 g and 23.7 <TEX>${\Omega}$</TEX>, respectively. The dimensions of the cantilever were determined for the resonance frequency of the cantilever.

The realization and performance of vibration energy harvesting MEMS devices based on anepitaxial piezoelectric thin film

This paper focuses on the fabrication and evaluation ofvibration energy harvesting devices by utilizing an epitaxialPb(Zr0.2Ti0.8)O3 (PZT) thin film. Thehigh quality of the c-axis oriented PZT layer results in a high piezoelectric coefficient and a low dielectricconstant, which are key parameters for realizing high performance piezoelectric energyharvesters. Different cantilever structures, with and without a Si proof mass, are realizedusing micro-patterning techniques optimized for the epitaxial oxide layers, to maintain thepiezoelectric properties throughout the process. The characteristics and the energyharvesting performances of the fabricated devices are experimentally investigatedand compared against analytical calculations. The optimized device based on a0.5 µm thick epitaxial PZT film, a cantilever beam of1 mm × 2.5 mm × 0.015 mm, with a Siproof mass of 1 mm × 0.5 mm × 0.23 mm, generates an output power, current and voltage of, respectively,13 µW g − 2,48 µA g − 1 and0.27 V g − 1 (g = 9.81 m s − 2) at the resonant frequency of 2.3 kHz for an optimal resistive load of5.6 kΩ. The epitaxial PZT harvester exhibits higher power and current with usable voltage,while maintaining lower optimal resistive load as compared with other examplespresent in the literature. These results indicate the potential of epitaxial PZTthin films for the improvement of the performances of energy harvesting devices.

A MEMS-based piezoelectric cantilever patterned with PZT thin film array for harvesting energy from low frequency vibrations

A piezoelectric energy harvesting cantilever integrated with Si proof mass has been presented to realize a low resonant frequency of 35.8Hz. This paper describes the design, microfabrication and measurement of such device for harvesting energy from low frequency environmental vibrations. Instead of deposition of PZT bulk film, ten PZT thin film patterns (PZT patterns) are parallel arrayed and electrically isolated on the supporting beam of the cantilever. The performance of output voltage and power of PZT patterns in series and in parallel connections are studied based on the experimental and simulation results. It is shown that PZT patterns in series and in parallel connections produce the same level of power in the corresponding matched load resistance, but PZT patterns in parallel connection is preferred because of lower matched load resistance required.

CMOS 공정에 적합한 AlN 압전 마이크로 발전기의 제작 및 특성

This paper describes the fabrication and characteristics of AlN piezoelectric MPG(micro power generator). The micro energy harvester was fabricated to convert ambient vibration energy to electrical power as a AlN piezoelectric cantilever with Si proof-mass. To be compatible with CMOS process, AlN thin film was grown at low temperature by RF magnetron sputtering and micro power generators were fabricated by MEMS technologies. X-ray diffraction pattern proved that the grown AlN film had highly(002) orientation with low value of FWHM(full width at the half maximum, $\theta

Micromachined PZT cantilever based on SOI structure for low frequency vibration energy harvesting

A PZT piezoelectric cantilever with a micromachined Si proof mass is designed and fabricated for a low frequency vibration energy harvesting application. The SiO 2 layer in the SOI wafer promotes accurate control of the silicon thickness that is used as a supporting layer in the cantilever beam structure. The entire effective volume of the fabricated device is about 0.7690 mm 3. When excited at 0.75 g ( g = 9.81 m/s 2) acceleration amplitude at its resonant frequency of 183.8 Hz, the AC output measured across a resistive load of 16 kΩ connecting to the device in parallel has an amplitude of 101 mV. The average power and power density determined by the same measurement conditions are, respectively, 0.32 μW and 416 μW/cm 3.

The design, fabrication and evaluation of a MEMS PZT cantilever with an integrated Si proof mass for vibration energy harvesting

A microelectromechanical system (MEMS) piezoelectric energy harvesting device, a unimorph PZT cantilever with an integrated Si proof mass, was designed for low vibration frequency and high vibration amplitude environment. Pt/PZT/Pt/Ti/SiO2 multilayered films were deposited on a Si substrate and then the cantilever was patterned and released by inductively coupled plasma reactive ion etching. The fabricated device, with a beam dimension of about 4.800 mm × 0.400 mm × 0.036 mm and an integrated Si mass dimension of about 1.360 mm × 0.940 mm × 0.456 mm produced 160 mVpk, 2.15 μW or 3272 μW cm−3 with an optimal resistive load of 6 kΩ from 2g (g = 9.81 m s−2) acceleration at its resonant frequency of 461.15 Hz. This device was compared with other demonstrated MEMS power generators.