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

Hashiguchi, Gen; Nakasone, Daiki; Sugiyama, Takeyoshi; Ataka, Mitsuo; Toshiyoshi, Hiroshi

doi:10.1063/1.4943528

Cited by 41 publications

(30 citation statements)

References 25 publications

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“…3). This proton injection resembles the potassium ion injection into silicon oxides for electret formation 40,41 and the field effect surface passivation of solar cells 42 .…”

Section: Electret Formationmentioning

confidence: 92%

Electret formation in transition metal oxides by electrochemical amorphization

2020

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Transition metal oxides (TMOs) are an important class of materials that show a wide range of functionalities involving spin, charge, and lattice degrees of freedom. The strong correlation between electrons in d-orbitals and the multivalence nature give rise to a variety of exotic electronic states ranging from insulator to superconductor and cause intriguing phase competition phenomena. Despite a burst of research on the multifarious functionalities in TMOs, little attention has been paid to the formation and integration of an electret-a type of quasi-permanent electric field generator useful for nanoscale functional devices as an electric counterpart to permanent magnets. Here, we find that an electret can be created in LaMnO 3 thin films by tip-induced electric fields, with a considerable surface height change, via solid-state electrochemical amorphization. The surface charge density of the formed electret area reaches~400 nC cm −2 and persists without significant charge reduction for more than a year. The temporal evolution of the surface height, charge density, and electric potential are systematically examined by scanning probe microscopy. The underlying mechanism is theoretically analyzed based on a drift-diffusion-reaction model, suggesting that positively charged particles, which are likely protons produced by the dissociation of water, play crucial roles as trapped charges and a catalysis to trigger amorphization. Our finding opens a new horizon for multifunctional TMOs.

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“…3). This proton injection resembles the potassium ion injection into silicon oxides for electret formation 40,41 and the field effect surface passivation of solar cells 42 .…”

Section: Electret Formationmentioning

confidence: 92%

Electret formation in transition metal oxides by electrochemical amorphization

2020

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“…It is also difficult to uniformly charge the dielectric film and optimise various parameters, such as the applied voltages and distances, among the needle, grid and sample. Alternative fabrication techniques, including electron beam, photoexcitation, X-ray or thermal excitation and ion implementation, that achieve a high σ value without corona charging have been proposed 2,5,[13][14][15][16][17][18] . However, all these charging processes involve factors that limit the productivity in terms of mass production; thus, simplification or elimination of the charging process would be exceptionally useful.…”

mentioning

confidence: 99%

Self-Assembled Electret for Vibration-Based Power Generator

Tanaka

Matsuura

Ishii

2020

Sci Rep

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the vibration-based electret generators (eGs) for energy harvesting have been extensively studied because they can obtain electrical energy from ambient vibrations. eGs exhibit a sandwich structure of electrodes surrounding an air gap and an electret, which is a dielectric material with a quasi-permanent electrical charge or dipole polarisation. Various charging processes have been developed because the surface charge density (σ) of the electret determines the output power of the device. However, such processes are considered to constitute a key productivity-limiting factor from the mass production viewpoint, making their simplification or elimination a highly desired objective. Herein, a model EG that does not require any charging process by utilising the spontaneous orientation polarisation of 1,3,5-tris(1-phenyl-1H-benzimidazole-2-yl)benzene (TPBi) is demonstrated. The surface potential (V sp ) of an evaporated TPBi film has reached 30.2 V at a film thickness of 500 nm without using a charging process. the estimated σ of 1.7 mC m −2 is comparable with that obtained using a conventional polymerbased electret after charging. Furthermore, V sp is considerably stable in environmental conditions; thus, tpBi can be considered to be "self-assembled" electret (SAe). Application of SAe leads to developing an EG without requiring the charging process.Sensor nodes have become indispensable for obtaining an extensive spectrum of information related to factors such as personal health, human and animal locations and the condition of the natural and built environments, including buildings, bridges and tunnels. However, the problem associated with powering the wireless sensor networks has to be solved for maintaining a society permeated by such devices. Recently, energy harvesting from ambient sources, such as heat, electrical waves, light and vibrations, has attracted considerable attention as a substitute for batteries, which exhibit various problems in terms of, for instance, the necessity for regular replacement and their contribution to toxic waste. Among the ambient-source devices, vibration harvesters are considered to be favourable owing to the presence of vibration in several environments, enabling a potentially extensive range of applications 1 .The vibration-based electret generators (EGs) are of particular interest for energy harvesting because they can provide relatively high output voltages even at low vibration frequencies ranging from few to several tens of hertz without the usage of any external bias source 1-4 . EGs typically exhibit a capacitor structure in which an electret and air gap are sandwiched between the top and bottom electrodes, as depicted in Fig. 1(a). An electret is a dielectric material with a quasi-permanent electrical charge or dipole polarisation 5 . These are indispensable in EGs because charges are induced by the electric field of the electret, eliminating the external bias for charging the capacitor 3,6,7 . An AC current is generated by the variance in air gap due to the out-of-plane (O...

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“…We fabricated the out-of-plane vibration device as an energy harvester using conventional microfabrication techniques and the potassium ion electret technique [ 25 ]. The device is made of a silicon-on-insulator (SOI) wafer with a 300

m thick device layer, a 3

m thick buried oxide layer, and a 450

m thick substrate.…”

Section: Fabrication Of the Vibration Energy Harvestermentioning

confidence: 99%

“…As shown in the lower-right inset in Figure 3 , potassium ions in the SiO

film of the positively biased side are ejected, and hence negatively charged oxygen deficiencies are fixed in the SiO

film, which creates a negative potential between the comb electrodes. The detail of the electret procedure and its charging principle are reported in literature [ 25 ]. After the charging procedure, the maximum surface potential measured by the surface potential meter showed 303 V.…”

Section: Fabrication Of the Vibration Energy Harvestermentioning

confidence: 99%

Development of a Cantilever-Type Electrostatic Energy Harvester and Its Charging Characteristics on a Highway Viaduct

Koga¹,

Mitsuya²,

Honma

et al. 2017

Micromachines

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We have developed a micro-electro-mechanical systems (MEMS) electrostatic vibratory power generator with over 100 μWRMS of (root-mean-square) output electric power under 0.03 GRMS (G: the acceleration of gravity) accelerations. The device is made of a silicon-on-insulator (SOI) wafer and is fabricated by silicon micromachining technology. An electret built-in potential is given to the device by electrothermal polarization in silicon oxide using potassium ions. The force factor, which is defined by a proportional coefficient of the output current with respect to the vibration velocity, is 2.34 × 10−4 C/m; this large value allows the developed vibration power generator to have a very high power efficiency of 80.7%. We have also demonstrated a charging experiment by using an environmental acceleration waveform with an average amplitude of about 0.03 GRMS taken at a viaduct of a highway, and we obtained 4.8 mJ of electric energy stored in a 44 μF capacitor in 90 min.

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

Cited by 41 publications

References 25 publications

Electret formation in transition metal oxides by electrochemical amorphization

Electret formation in transition metal oxides by electrochemical amorphization

Self-Assembled Electret for Vibration-Based Power Generator

Development of a Cantilever-Type Electrostatic Energy Harvester and Its Charging Characteristics on a Highway Viaduct

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