&lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$In Situ$ &lt;/tex-math&gt;&lt;/inline-formula&gt; Measurement of Charging Process in Electret-Based Comb-Drive Actuator and High-Voltage Charging

Shibata, Yoichi; Sugiyama, Takeyoshi; Mimura, Hidenori; Hashiguchi, Gen

doi:10.1109/jmems.2014.2379959

Cited by 14 publications

(13 citation statements)

References 24 publications

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“…Devices can be fabricated by attaching electret chips to MEMS devices, but this would interfere the largest feature of MEMS: mass production by batch processing without assembly. Amongst several researches seeking for electret fabrication on micromachined trench structures [2,3], the potassium-ion-electret method [4][5][6] has a high compatibility with silicon MEMS and is used in this research. The electret can be fabricated as a post-processing of silicon micromachining, where the electret potential is formed by applying a DC voltage under high temperature to a thermally grown potassium ion incorporated silicon dioxide.…”

Section: Introductionmentioning

confidence: 99%

An Electret-Augmented Low-Voltage MEMS Electrostatic Out-of-Plane Actuator for Acoustic Transducer Applications

et al. 2020

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Despite the development of energy-efficient devices in various applications, microelectromechanical system (MEMS) electrostatic actuators yet require high voltages to generate large displacements. In this respect, electrets exhibiting quasi-permanent electrical charges allow large fixed voltages to be integrated directly within electrode structures to reduce or eliminate the need of DC bias electronics. For verification, a − 40 V biased electret layer was fabricated at the inner surface of a silicon on insulator (SOI) structure facing a 2 μm gap owing to the high compatibility of silicon micromachining and the potassium-ion-electret fabrication method. A − 10 V electret-augmented actuator with an out-of-plane motion membrane reached a sound pressure level (SPL) of 50 dB maximum with AC input voltage of V i n = 5 V pp alone, indicating a potential for acoustic transducer usage such as microspeakers. Such devices with electret biasing require only the input signal voltage, thus contributing to reducing the overall power consumption of the device system.

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Section: Introductionmentioning

confidence: 99%

An Electret-Augmented Low-Voltage MEMS Electrostatic Out-of-Plane Actuator for Acoustic Transducer Applications

et al. 2020

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“…1. 6,[24][25] First, a Si substrate is thermally oxidized by steam supplied through a KOH solution to obtain a-SiO2 with potassium atoms. In this process, potassium and hydrogen atoms are incorporated into the a-SiO2.…”

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confidence: 99%

Negative-charge-storing mechanism of potassium-ion SiO2-based electrets for vibration-powered generators

Nakanishi

Miyajima

Chokawa

et al. 2020

Applied Physics Letters

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A potassium-ion electret, which is a key element of vibration-powered microelectromechanical generators, can store negative charge almost permanently. However, the mechanism by which this negative charge is stored is still unclear. We theoretically study the atomic and electronic structures of amorphous silica (a-SiO2) with and without potassium atoms using first-principles molecular-dynamics calculations. Our calculations show that a fivefold-coordinated Si atom with five Si–O bonds (an SiO5 structure) is the characteristic local structure of a-SiO2 with potassium atoms, which becomes negatively charged and remains so even after removal of the potassium atoms. These results indicate that this SiO5 structure is the physical origin of the robust negative charge observed in potassium-ion electrets. We also find that the SiO5 structure has a Raman peak at 1000 cm−1.

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“…The electret potential is then supplied by applying a DC voltage at temperatures above 500 • C. The detailed procedure for forming electrets has been published elsewhere. 18,19 Figure 1(a) is the photograph of a comb-drive actuator in which small carbon particles were attracted to one side of the comb-drive electrode, while the opposing side remained free of particles. Since electret materials function as a particle filter, 20 this photograph implies that only one side of electrode was covered with an electret film.…”

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confidence: 99%

“…During the electret charging process, a voltage difference is given to the capacitance in MEMS devices. 19 In order to replicate the potassium ion technique and obtain a larger-scale electret film for the purpose of analyzing, we prepared several p-type silicon chips (1-20 Ωcm) with a thickness of 400 µm, which were cut into 7.5-mm-wide, 15-mm-long pieces. These pieces were then thermally oxidized with steam supplied through a 40 wt% KOH solution at around 80 • C, and a SiO 2 film of about 850 nm in thickness was formed on silicon.…”

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Charging mechanism of electret film made of potassium-ion-doped SiO2

et al. 2016

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A charging model is proposed for an electret film made of potassium-ion-doped SiO2 that can be formed between the two opposing micro-electrodes of a micro-electrostatic actuator, separated by a microscopic gap. On the basis of experimental evidence that charging only occurs in the positively biased electrode during the charging process and that the charging polarity is negative, we assumed that the cause of the electret charges is negatively charged oxygen ions residing in the SiO2 film, which arise as a consequence of potassium ion depletion. This assumption was supported by SIMS (Secondary Ion Mass Spectroscopy) analyses that indicate the presence of a depletion region of potassium ions near the interface of the silicon and the oxide film on the positively biased electrode. Calculations of the charged potential using Poisson’s equation with the spatially distributed negative charges in the depletion region showed good agreement with the measured surface potential. It appears that our charging model can consistently elucidate potassium ion electret technology.

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<inline-formula> <tex-math notation="LaTeX">$In Situ$ </tex-math></inline-formula> Measurement of Charging Process in Electret-Based Comb-Drive Actuator and High-Voltage Charging

Cited by 14 publications

References 24 publications

An Electret-Augmented Low-Voltage MEMS Electrostatic Out-of-Plane Actuator for Acoustic Transducer Applications

An Electret-Augmented Low-Voltage MEMS Electrostatic Out-of-Plane Actuator for Acoustic Transducer Applications

Negative-charge-storing mechanism of potassium-ion SiO2-based electrets for vibration-powered generators

Charging mechanism of electret film made of potassium-ion-doped SiO2

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