Internal Electric Field Distribution Research Articles

Development of IPMC actuators with high bending uniformity and orientation

Ionic polymer-metal composite (IPMC) actuators have attracted considerable scientific interest in the field of robotics and artificial muscles due to their low operating voltage, high strain capacity, and lightweight. However, the non-uniform bending of IPMC actuators affects their control accuracy and limits their potential applications. In this work, the surface voltage of IPMC actuators was measured and the internal electric field distribution was numerically computed. It was concluded that the non-uniform bending is mainly due to the non-uniform distribution of hydrated cations inside the IPMC as a result of the inhomogeneous electric field. The bending uniformity is improved by sputtering a gold layer on the surface of the IPMC actuator, and a support strip is introduced to limit the bending of the IPMC in the width direction, resulting in an improvement of its pointing characteristics. It is found that the bending uniformity of IPMC improved by 35.27% and 119.48% by sputtering at an input voltage of 2.5 V and 5 V respectively. When the input voltage is fixed at 2.5 V and 5 V, the bending in the width direction is reduced by 75.68% and 93.12% with the support structure, respectively.

DFT-Assisted Investigation of the Electric Field and Charge Density Distribution of Pristine and Defective 2D WSe2 by Differential Phase Contrast Imaging.

Most properties of solid materials are defined by their internal electric field and charge density distributions which so far are difficult to measure with high spatial resolution. Especially for 2D materials, the atomic electric fields influence the optoelectronic properties. In this study, the atomic-scale electric field and charge density distribution of WSe2 bi- and trilayers are revealed using an emerging microscopy technique, differential phase contrast (DPC) imaging in scanning transmission electron microscopy (STEM). For pristine material, a higher positive charge density located at the selenium atomic columns compared to the tungsten atomic columns is obtained and tentatively explained by a coherent scattering effect. Furthermore, the change in the electric field distribution induced by a missing selenium atomic column is investigated. A characteristic electric field distribution in the vicinity of the defect with locally reduced magnitudes compared to the pristine lattice is observed. This effect is accompanied by a considerable inward relaxation of the surrounding lattice, which according to first principles DFT calculation is fully compatible with a missing column of Se atoms. This shows that DPC imaging, as an electric field sensitive technique, provides additional and remarkable information to the otherwise only structural analysis obtained with conventional STEM imaging.

Three-Dimensional Transient Electric Field Characteristics of High Pressure Electrode Boilers

An uneven electric field during the operation of an electrode boiler will lead to the emergence of a high field strength area and low field strength area in the furnace, which will endanger the safe and reliable operation and heating efficiency of the electrode boiler. A numerical study of three-dimensional transient electric field distribution characteristics in a 10 kV high-voltage electrode boiler was carried out. The distribution characteristics of the global electric field of the electrode boiler under the nominal voltage of 10 kV were studied, and the distribution law of the electric field of the electrode boiler under poor power quality, such as different bus voltage and three-phase voltage imbalance, was explored. The results show that the electric field distribution characteristics of the three-phase transient are more obvious in the section closer to the electrode disc, and the electric field distribution is the most uniform in the section that is 1.4 m away from the furnace water. In the case of poor power quality, such as different bus voltage and three-phase voltage imbalance, the points of the maximum electric field intensity of the four surfaces change periodically with time, and the greater the bus voltage fluctuation, the more severe the impact on the transient electric field. The three-phase voltage imbalance will shift the peak value of the electric field intensity. The decrease or offset of electric field intensity in the electrode boiler caused by poor power quality will directly affect its heating efficiency. The electric field simulation results have a specific reference value for improving the internal electric field distribution and on-site operation and maintenance of the electrode boiler.

Characterization of electric field distribution in valve-side casing of 500 kV converter transformer considering AC and DC mixed voltage

The converter transformer, as one of the indispensable core devices in the ultra-high voltage direct current (UHVDC) transmission system, exhibits highly complex electric field distribution characteristics within the valve-side bushing. In-depth research into the electric field distribution characteristics and variation patterns of the valve-side bushing under both alternating current (AC) and direct current (DC) voltage conditions is crucial for ensuring the reliable operation of the transmission system. This study focuses on investigating the electric field distribution of the valve-side bushing under AC and DC voltage excitations. A full-scale finite element model of the valve-side bushing of the converter transformer is constructed using finite element simulation software for modeling and research purposes. The results indicate that the internal electric field distribution of the bushing is generally similar under both AC and DC voltage excitations. However, in the SF6-filled region, a steeper voltage drop is observed under DC excitation compared to AC. The space charges generated in the DC electric field due to field polarization have a significant impact on the distortion of the electric field on the inner and outermost layer electrode plates. These conclusions provide theoretical guidance for the insulation design of the valve-side bushing in converter transformers at the 500 kV voltage level and similar ratings.

Effect of temperature on the internal electric field distribution and discharge mechanism of converter transformer under AC-DC composite voltage

Effect of temperature on the internal electric field distribution and discharge mechanism of converter transformer under AC-DC composite voltage

High discharge energy density in rationally designed graphene oxide@zinc oxide/polymer blend-polyetherimide heterostructured bilayer nanocomposites

The advancement of new dielectric materials exhibiting greater discharge energy density is crucial for current power systems and electronic devices. In this work, various weight percentages of graphene oxide@zinc oxide (GO@ZO) nanofillers were incorporated inside a polymer blend of poly(vinylidene fluoride-hexafluoropropylene)/polyetherimide (P(VDF-HFP)/PEI; shortened as BP) and used as a high dielectric top layer. In contrast, linear-type PEI (L) was used as a bottom insulation layer to achieve a high breakdown strength (Eb) in bilayer nanocomposites. As a result, the 2BP-L composite demonstrated a high discharged energy density of 12.63 J/cm3 at an electric field of 527 MV/m with only 2 wt% GO@ZO nanofillers addition in the top layer. Such a high discharge energy density with minimal nanofiller loading is attributed to the utilization of novel surface-decorated GO@ZO nanofillers and new bilayer-heterostructured linear/ferroelectric-linear polymer. In comparison to its counterparts (i.e., PEI, P(VDF-HFP) and 0BP-L), the 2BP-L nanocomposite showed ∼426.3 %, 92.5 %, and 9.8 % enhancement in discharge energy density, respectively. The discharge rate and stability analysis revealed a significantly higher power density of 0.55 MW/cm3, indicating its high potential to be used as a pulsed power system. Finite element simulation revealed that the effective internal electric field distribution and higher dielectric displacement in 2BP-L resulted in such enhancement over its counterparts. This study presents a new model to maximize the energy storage capability of flexible energy storage devices and advances knowledge of the polarization mechanisms and breakdown of bilayer nanocomposite dielectric materials.

Accelerating Quantum Materials Development with Advances in Transmission Electron Microscopy.

Quantum materials are driving a technology revolution in sensing, communication, and computing, while simultaneously testing many core theories of the past century. Materials such as topological insulators, complex oxides, superconductors, quantum dots, color center-hosting semiconductors, and other types of strongly correlated materials can exhibit exotic properties such as edge conductivity, multiferroicity, magnetoresistance, superconductivity, single photon emission, and optical-spin locking. These emergent properties arise and depend strongly on the material's detailed atomic-scale structure, including atomic defects, dopants, and lattice stacking. In this review, we describe how progress in the field of electron microscopy (EM), including in situ and in operando EM, can accelerate advances in quantum materials and quantum excitations. We begin by describing fundamental EM principles and operation modes. We then discuss various EM methods such as (i) EM spectroscopies, including electron energy loss spectroscopy (EELS), cathodoluminescence (CL), and electron energy gain spectroscopy (EEGS); (ii) four-dimensional scanning transmission electron microscopy (4D-STEM); (iii) dynamic and ultrafast EM (UEM); (iv) complementary ultrafast spectroscopies (UED, XFEL); and (v) atomic electron tomography (AET). We describe how these methods could inform structure-function relations in quantum materials down to the picometer scale and femtosecond time resolution, and how they enable precision positioning of atomic defects and high-resolution manipulation of quantum materials. For each method, we also describe existing limitations to solve open quantum mechanical questions, and how they might be addressed to accelerate progress. Among numerous notable results, our review highlights how EM is enabling identification of the 3D structure of quantum defects; measuring reversible and metastable dynamics of quantum excitations; mapping exciton states and single photon emission; measuring nanoscale thermal transport and coupled excitation dynamics; and measuring the internal electric field and charge density distribution of quantum heterointerfaces- all at the quantum materials' intrinsic atomic and near atomic-length scale. We conclude by describing open challenges for the future, including achieving stable sample holders for ultralow temperature (below 10K) atomic-scale spatial resolution, stable spectrometers that enable meV energy resolution, and high-resolution, dynamic mapping of magnetic and spin fields. With atomic manipulation and ultrafast characterization enabled by EM, quantum materials will be poised to integrate into many of the sustainable and energy-efficient technologies needed for the 21st century.

Shielding Strategies for Electric Field Minimization in Current Transformers: A Finite Element Combined Design of Experiment Approach

The internal electric field distribution is a key factor to characterize the partial discharge and voltage resistance of current transformers (CTs), and the conical current transformer has a special structure with complex electric field distribution. Therefore, it is more necessary to study, analyze and optimize the electric field distribution of CTs in the design process. In this paper, a new type of current transformer is taken as the research object. A simulation model is established by using finite element software, and the electric field distribution under the test of power-frequency withstand voltage is investigated. Then, a scheme is proposed, and the response surface is used to optimize the scheme. Experimental verification is conducted to validate the results. In this study, the finite element combined design of experiment approach can serve as a rapid and efficient approach for identifying an optimal solution to minimize the electric field strength within a current transformer.

Self-powered MSM solar-blind AlGaN photodetector realized by in-plane polarization modulation.

Solid-state self-powered UV detection is strongly required in various application fields to enable long-term operation. However, this requirement is incompatible with conventionally used metal-semiconductor-metal (MSM) UV photodetectors (PDs) due to the symmetric design of Schottky contacts. In this work, a self-powered MSM solar-blind UV-PD was realized using a lateral pn junction architecture. A large built-in electric field was obtained in the MSM-type UV-PD without impurity doping, leading to efficiency carrier separation and enhanced photoresponsivity at zero external bias. The solar-blind UV-PD exhibits a cutoff wavelength of 280 nm, a photo/dark current ratio of over 105, and a responsivity of 425.13 mA/W at -10 V. The mechanism of self-powered UV photodetection was further investigated by TCAD simulation of the internal electric field and carrier distributions.

Simulation calculation of electric field distribution in the rat brain irradiated by electromagnetic pulses

Based on the spectrum distribution of electromagnetic pulses (EMPs), we constructed a dispersive electromagnetic model of rats with a fine division of tissues and organs and calculated the internal electric field distribution in the rat brain exposed to EMPs. The results showed that EMP radiation was capable of generating electric field distribution with good uniformity in the rat brain and that the peak field intensity in the rat brain was about 1/250 of that in the spatial domain. The electric field in the cerebral cortex was slightly higher than that in the deep hippocampus, striatum, and thalamus, and it was probably the lowest in the hypothalamus. In the cortex, the electric field was low in the prefrontal cortex, while it was relatively high in the parietal and temporal lobes near the middle and at the back of the brain. The data provide a theoretical quantitative basis for establishment of the dose–effect relationship between the electric field in the rat brain and biological effects of the pulse. In addition, it serves as a reference for simulation calculation of the effect of EMPs in living organisms.

Second Harmonic Generation in 1D Nonlinear Plasma Photonic Crystals

AbstractIn this paper, a 1D nonlinear plasma photonic crystal (NPPC) structure composed of polarized ferroelectric crystals and nonlinear plasma periodic alternation is proposed. The transfer matrix method is employed to analyze the second harmonic generation (SHG) problem of this structure. In the designed NPPCs, the fundamental wave (FW) operates in the gigahertz (GHz) band and the nonlinear plasma is controlled by an external high‐intensity control wave (CW). Numerical simulations are performed to investigate the effects of different incident angles and external CW intensities on the total conversion efficiency (T‐con) of the second harmonic wave (SHW). Additionally, the internal electric field distribution and incident light intensity within the nonlinear structure are analyzed. The importance of the relationship between the FW frequency and photonic band gap (PBG) in enhancing SHG is summarized. The results demonstrate that the optimal structure can be obtained by changing the structural parameters, such that the FW and SHW are tuned to the edge of the PBG. At this point, the electromagnetic field density is large, the group velocity is small, the local field is enhanced, and the nonlinear optical interaction is increased, resulting in a significant increase in the T‐con of the SHW.

Investigating simultaneous effects of temperature, surface heterogeneity and geometry on fluid mixing in electroosmotic flow considering temperature dependent properties by Nernst–Planck Poisson method

Numerical study of the effect of temperature and heat transfer as well as surface heterogeneity effects on mixing and electroosmotic flow in microchannels with convergent/divergent and straight mixing chamber is carried out. The fluid properties and surface zeta potentials are assumed to be temperature dependent. Based on the Nernst–Planck Poisson model, the governing equations of this problem include the Laplace equation, Poisson equation, Navier–Stokes and the propagation equation as well as the energy equation, respectively for the distribution of external electric field, distribution of internal electric field due to the charge of ions, fluid motion, concentration field and temperature distribution, which are solved by the finite element method. Flow rate, the mixing efficiency and a new parameter called mixing capacity, which is achieved by multiplying flow rate by mixing efficiency, are obtained for convergent/divergent and straight microchannels in a constant external electric field distributed under different wall temperatures, and performance of the geometries in flow transfer and mixing development is investigated. For electroosmotic flow, heterogeneous microchannels create vortices which improve mixing. Different arrangements of heterogeneous pieces of the surface create different patterns of vortices, each of which has different effects in the various geometries on fluid flow and mixing. Also, the dependence of the molecular diffusion on temperature causes increasing the mixing of species with the temperature increment. The results show that divergent microchannels have the maximum flow rate and the minimum mixing efficiency, but this efficiency can be increased by increasing the wall temperature. Convergent microchannels also have high mixing efficiency due to low flow rates and sufficient time for mixing even at low and near ambient temperatures, although their mixing capacity is less than the divergent microchannels.

Failure Mechanism of pHEMT in Navigation LNA under UWB EMP.

With the development of microelectronic technology, the integration of electronic systems is increasing continuously. Electronic systems are becoming more and more sensitive to external electromagnetic environments. Therefore, to improve the robustness of radio frequency (RF) microwave circuits, it is crucial to study the reliability of semiconductor devices. In this paper, the temporary failure mechanism of a gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (pHEMT) in a navigation low-noise amplifier (LNA) under the jamming of ultra-wideband (UWB) electromagnetic pulses (EMP) is investigated. The failure process and failure mechanism of pHEMT under UWB EMP are elaborated by analyzing the internal electric field, current density, and temperature distribution. In detail, as the amplitude of UWB EMP increases, the output current, carrier mobility, and transconductance of pHEMT decrease, eventually resulting in gain compression. The injection experiment on LNA, which effectively verified the failure mechanism, indicates that the gain of pHEMT is suppressed instantaneously under the jamming of UWB EMP and the navigation signal cannot be effectively amplified. When UWB EMP amplitude increases to nearly 10 V, the BeiDou Navigation Satellite System (BDS) carrier signal is suppressed by nearly 600 ns. Experimental results accord well with the simulation of our model. UWB EMP jamming is a new and efficient type of electromagnetic attack system based on the device saturation effect. The performance degradation and failure mechanism analysis contribute to RF reinforcement design.

Comparisons of Two Turn-off Failures Under Clamped Inductive Load in Planar FS 3.3 kV/50 A IGBT Chip

Turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> failure under clamped inductive load, is one of the most concerns in insulated gate bipolar transistor (IGBT) chips. Besides, this turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> failure can be attributed to two causes, i.e., the dynamic latch-up and the secondary breakdown. Despite great simulation work investigated previously, the experimental research should be further focused. Up to now, the typical features and differences for these two turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> failures still remain unclear. In this article, two failures’ waveforms are first compared in experiment. Moreover, their internal current, electric field, and temperature distributions are compared by simulation in detail. Then, two different failure features, focusing on the failure cell structures, are summarized from the scanning electron microscope (SEM) results for the first time. The marked signatures of these failures, such as the current filament path and the mixture region, are further analyzed in this article. According to the SEM results, the lateral and vertical current paths can be observed in dynamic latch-up chip and secondary breakdown chip, respectively. These failure signatures in waveforms and SEM results can contribute to the distinguished method to the failure causes in IGBT device, and enhance the chip's performance more effectively.

Nanoscale Electric Field Probing in a Single Nanowire with Raman Spectroscopy and Elastic Strain.

In this work we investigate the Raman response of extremely strained gallium phosphide nanowires. We analyze new strain-induced spectral phenomena such as 2-fold and 3-fold phonon peak splitting which arise due to nontrivial internal electric field distribution coupled with inhomogeneous strain. We show that high bending strain acts as a probe allowing us to define the electric field distribution with deep subwavelength resolution using the corresponding changes of the Raman spectra. We investigate the nature of the localization with respect to nanowire diameter, excitation spot position, and light polarization, supporting the experiment with 3D numerical modeling. Based on our findings we propose a research tool allowing to precisely localize the electric field in a certain subwavelength region of the nanophotonic resonator.

InP/InGaAs Uni-Traveling-Carrier Photodiode (UTC-PD) With Improved EM Field Response

In this article, a unique structure of InP/InGaAs uni-traveling-carrier photodiode (UTC-PD) is proposed. Compared with the one-sided junction photodiode, the UTC-PD has the advantages of a simpler epitaxial layer structure while maintaining the characteristics of high bandwidth and high output power loss profile. Simulated results show that a large built-in electric field can be generated under illumination, which aids UTC carrier velocity. The merits of the new structure are compared to a standard UTC-PD photodiode in terms of improved electric field and carrier concentration response. It is demonstrated that the photogeneration and light absorption of UTC-PDs are improved by incorporating a step-like internal texture of cones and dots profile in the photo absorption layer. The simulated device shows a peak electrical 3-dB bandwidth of 65 GHz at a low light intensity and reverse bias voltage. The performance characteristics of 1-D and 2-D UTC-PD simulations, including internal electric field distribution, energy band diagram, carrier concentration, and power loss distribution, are carefully studied. A theoretical discussion of the working principle and key performance characteristics of a UTC-PD enhanced by heterojunction design is reported. The entire physical environment is modeled and simulated through the finite element method (FEM) using commercial software. The proposed photodiode structure configuration is designed and optimized for photodetectors for high RF frequencies at different light intensities. To the best of our knowledge, the obtained bandwidth and electric field response is the fastest among those reported for other various higher wavelength photodiodes.

Numerical simulation of internal electric field distribution in colloidal photonic crystal thin films

We have computed the internal electric field distribution in monolayer, bilayer, and trilayer colloidal photonic crystal thin films on a glass substrate. The field distributions are evaluated on the top photonic crystal layer under the effects of additional layers along the direction of light propagation We have also investigated the field distributions in photonic crystal thin films at on-resonance and off-resonance incident wavelengths. The calculated reflection and transmission spectra of photonic crystal thin films help us choose the right wavelengths for determining the on-resonance and off-resonance conditions. The electric fields across different regions in the crystal plane are evaluated for a quantitative understanding of the field distribution. We have observed that the internal electric field gets redistributed in the plane of a close-packed periodic array of colloids. Our results reveal that the internal electric field is localized and enhanced in the air void region between the dielectric spheres with nearly the same maximum field values for the on-resonance wavelength. We have observed that at off-resonance wavelength, the field gets localized within the dielectric sphere region for the monolayer and bilayer cases. Contrastingly, the field distribution in the trilayer case forms a connecting network within the photonic crystal plane. Under off-resonance wavelength, the trilayer shows a huge enhancement in maximum field values compared to the monolayer and bilayer thin films. These results promise to employ photonic crystal thin films of colloidal dielectric spheres as templates for sensing applications using the surfaced enhanced Raman scattering technique.

Effect of irradiation on pyroelectric and electrocaloric parameters in lead-free relaxor ferroelectric ceramic

Ferroelectric materials have a renaissance due to various photosensitive characteristics. In this study, temperature-dependent dielectric, impedance, and ferroelectric measurements were carried out on lead-free Ba0.6(Bi0.5Li0.5)0.4TiO3 (BBLT) ferroelectric ceramic under the dark and exposure of monochromatic 405 nm light conditions. Profound analysis of complex impedance spectroscopy shows a noticeable reduction in bulk capacitance, relaxation time, and constant phase element parameters under illuminated conditions. Relevant phenomenological approaches towards modified Cole−Cole models confirm that the light induces photogenerated nonequilibrium charge carriers. Thus, the trapped charges alter the internal electric field distribution energy. Under illumination, the enhanced polarization and corresponding pyroelectric coefficient enhanced by 40 % and ~260 % at 5 Hz and 10 Hz, respectively, at 20 ℃ were observed. The cross-coupled Electrocaloric (EC) parameters ∆T and ∆S enhanced 600 % and 571 % at 10 Hz, respectively, and 219 % and 218 %, at 5 Hz respectively at 20 ℃ under illumination. This study provides a comprehensive understanding and new insights into the light-dependent dielectric, ferroelectric, pyroelectric and electrocaloric mechanisms in BBLT electroceramics, which encourages the design of modern thermal sensor devices.

Investigation of transport properties of perovskite single crystals by pulsed and DC bias transient current technique

Time-of-flight (ToF) transient current method is an important technique to study the transport characteristics of semiconductors. Here, both the direct current (DC) and pulsed bias ToF transient current method are employed to investigate the transport properties and electric field distribution inside the MAPbI3 single crystal detector. Owing to the almost homogeneous electric field built inside the detector during pulsed bias ToF measurement, the free hole mobility can be directly calculated to be about 22 cm2⋅V−1⋅s−1, and the hole lifetime is around 6.5 μs–17.5 μs. Hence, the mobility-lifetime product can be derived to be 1.4 × 10−4 cm2⋅V−1–3.9 × 10−4 cm2⋅V−1. The transit time measured under the DC bias deviates with increasing voltage compared with that under the pulsed bias, which arises mainly from the inhomogeneous electric field distribution inside the perovskite. The positive space charge density can then be deduced to increase from 3.1 × 1010 cm−3 to 6.89 × 1010 cm−3 in a bias range of 50 V–150 V. The ToF measurement can provide us with a facile way to accurately measure the transport properties of the perovskite single crystals, and is also helpful in obtaining a rough picture of the internal electric field distribution.

Research on discharge characteristics of GLA with surface pollution/icing

In operation of the AC power system, when the surface of gapped line arresters (GLA) is polluted, moist and iced, its internal electric field and potential distribution will be distorted. It will lead to the internal partial discharge and the significantly decrease of the power frequency discharge voltage, which seriously threatens the safety of the power system. Therefore, the influence on the body-gap voltage ratio of two typical structures of GLA under clean, polluted and iced external surface state need to be studied. And the finite-element method was used to calculate the electric field and potential distribution under different surface state. Based on the experiment of discharge characteristics of GLA under different conditions in artificial climate chamber, the electric field and potential distribution under the polluted and iced surface, the body-gap voltage ratio and the discharge characteristics of GLA were obtained, which was of great significance for the safety and stability of power system and the design of GLA.