Electric Field Current Density Research Articles

Enhancing the circular dichroism of chiral dielectric nanostructure through the addition of a symmetric Au cylinder

Circular dichroism (CD) spectra play a crucial role in recognition, separation and detection of chiral molecules. Due to the inherent weak CD response of natural chiral molecules, researchers have endeavored to enhance CD signals through various artificial nanostructures. In this study, combining the advantages of both the dielectric and metal materials, we propose a hybrid dielectric-metal nanostructure consisting of a chiral Si nanorod dimer coupled with a symmetric Au cylinder to achieve robust CD responses. Owing to the plasmon resonance of the Au cylinder, the scattering-CD and absorption-CD of the hybrid system have been enhanced, which result in the enhanced extinction-CD response. Furthermore, the distributions of electric field, magnetic field and displacement current density of both the Si dimer and hybrid nanostructure have been meticulously crafted to elucidate the physical mechanisms underlying amplified CD signals. The synergistic coupling between the magnetic fields of dielectric materials and the electric fields of the Au cylinder leads to an increase in the electric field strength and the asymmetry of near-field distributions. Additionally, spatial overlaps between electric and magnetic fields occur. These factors contribute to the enhanced chiral response of the hybrid system. Meanwhile, the CD signal can be flexibly tuned by adjusting the size of the Au cylinder and Si nanorods. This design offers a versatile approach to enhancing the chiral response of dielectric nanostructures.

A method for calculating space charge distribution in ultra-high voltage direct current transmission lines based on the transport of diluted species theory

The occurrence of corona discharge in ultra-high-voltage direct current transmission lines results in the generation of space charge, which significantly affects the nearby electromagnetic environment. To investigate the micro-physical mechanisms of discharge and provide better guidance for the calculation of the ground ion current density and total electric field, a method based on the theory of the transport of diluted species is proposed. This method enables the visualization and analysis of the movement process of space charge in air medium, as well as the calculation of the total electric field below the transmission lines. To validate the effectiveness of this algorithm, experimental tests of the total electric field are conducted on actual transmission lines. The experimental results demonstrate that the algorithm not only highlights the evident differences in the transient microscopic processes between positive and negative corona discharges but also accurately calculates the total electric field below the transmission lines. In addition, considering the weather conditions in the Chongqing region, relevant recommendations are provided under the influence of wind speed, aiming to offer protection guidelines for individuals engaged in activities near transmission lines.

Study of the mechanism of single event burnout in lateral depletion-mode Ga2O3 MOSFET devices via TCAD simulation

This study investigates the sensitive region and safe operation voltage of single-event burnout (SEB) in lateral depletion-mode Ga2O3 MOSFET devices via technology computer aided design simulation. Based on the distribution of the electric field, carrier concentration, and electron current density when SEB occurs, the radiation damage mechanism of SEB is proposed. The mechanism of SEB in Ga2O3 MOSFET was revealed to be the result of a unique structure without a PN junction within it, which possesses gate control ability and exerts a significant influence on the conduction of the depletion region.

Influence of temperature and pressure gradient on power deposition and field pattern in High Magnetic field Helicon eXperiment

AbstractBased on High Magnetic field Helicon eXperiment, considering the parabolic distribution and Gaussian distribution of radial plasma density, HELIC code was used to study the influence of temperature and pressure gradient on power deposition, electric field, and current density of Helicon Wave Plasma. Three different gradients (positive, negative, and zero gradient) were selected. The results show that positive temperature gradient is beneficial to increase the relative absorption power at the center of plasma. Compared with negative and zero pressure gradients, positive pressure gradient increases the relative absorption power and weakens the current density at the center of plasma, and increases the electric field intensity at the edge of plasma. Larger edge heating will cause the relative absorption power at edge to rise rapidly, which is not conducive to the coupling at the center of plasma. In practical experiments, it is particularly important to reduce the heating effect at edge by cooling the antenna itself. Three different gradients of temperature and pressure have little effect on electric field intensity and current density in plasma, and the variation trend is basically similar, which proves the stability of the antenna mode: m = 1.

Effects of Varying Annealing Ambient towards Performance of Ternary GaxCeyOz Passivation Layers for Metal-Oxide-Semiconductor Capacitor

In this work, different annealing ambient (nitrogen-oxygen-nitrogen (N2-O2-N2), forming gas-oxygen-forming gas (FG-O2-FG), and argon-oxygen-argon (Ar-O2-Ar)) were explored to investigate the feasibility of employing the annealed ternary GaxCeyOz passivation layer (PL) for development of Si-based metal-oxide-semiconductor (MOS) capacitors. The impact of nitrogen and/or hydrogen in hindering the growth of silicon dioxide (SiO2) interfacial layer (IL) was quantitatively evaluated. The combination of effects brought by nitrogen attached to oxygen vacancies, nitrogen-silicon bonding, and nitrogen accumulation at the GaxCeyOz/Si interface effectively minimized the formation of SiO2 IL. Consequently, among all the samples, the GaxCeyOz PL annealed in N2-O2-N2 ambient exhibited superior MOS characteristics in terms of low effective oxide charge, slow trap density, interface trap density, and interface state density, which have translated into good leakage current density-electric field characteristics.

Study of the influence of virtual guard ring width on the performance of SPAD detectors in 180 nm standard CMOS technology

The influence of the virtual guard ring width (GRW) on the performance of the p-well/deep n-well single-photon avalanche diode (SPAD) in a 180 nm standard CMOS process was investigated. TCAD simulation demonstrates that the electric field strength and current density in the guard ring are obviously enhanced when GRW is decreased to 1 μm. It is experimentally found that, compared with an SPAD with GRW = 2 μm, the dark count rate (DCR) and afterpulsing probability (AP) of the SPAD with GRW = 1 μm is significantly increased by 2.7 times and twofold, respectively, meanwhile, its photon detection probability (PDP) is saturated and hard to be promoted at over 2 V excess bias voltage. Although the fill factor (FF) can be enlarged by reducing GRW, the dark noise of devices is negatively affected due to the enhanced trap-assisted tunneling (TAT) effect in the 1 μm guard ring region. By comparison, the SPAD with GRW = 2 μm can achieve a better trade-off between the FF and noise performance. Our study provides a design guideline for guard rings to realize a low-noise SPAD for large-array applications.

Growth of gallium cerium oxide passivation layer on 4H-Silicon carbide substrate and its metal-oxide-semiconductor characteristics

Gallium cerium oxide (GaxCeyOz) passivation layer was successfully grown on 4H-silicon carbide (SiC) through postdeposition annealing at 800 °C in nitrogen-oxygen-nitrogen (N2–O2–N2) ambient. The gracing incident X-ray diffraction and ultraviolet–visible spectrophotometer measurements have confirmed the successful incorporation of Ga3+ cation into the CeO2 lattice to form the ternary GaxCeyOz passivation layer. In addition, the thicknesses of GaxCeyOz passivation layer and silicon dioxide (SiO2) interfacial layer (IL) were determined using field-emission scanning electron microscopy and X-ray reflectivity characterizations. A high dielectric constant (k) value of 24.11 was attained for the investigated Al/GaxCeyOz/4H–SiC/Al metal-oxide-semiconductor (MOS) structure attributable to the nitrogen ions accumulating at the interface that have retarded the growth of SiO2 IL. Besides, the effective oxide charge, slow trap density, interface trap density, interface state density, as well as leakage current density-electric field characteristic of the investigated GaxCeyOz passivation layer on 4H–SiC substrate was presented in this work.

Ferroelectric YAlN grown by molecular beam epitaxy

We report the demonstration of ferroelectric switching in yttrium (Y)-doped nitride semiconductors. In this study, single-crystalline, wurtzite Y0.07Al0.93N films were epitaxially grown on GaN/sapphire templates by plasma-assisted molecular beam epitaxy. The ferroelectric switching process has been investigated by current density–electric field (J-E) and polarization–electric field (P-E) loops as well as positive-up-negative-down measurements, showing a coercive field of ∼6 MV/cm and a switchable polarization of ∼130 μC/cm2. Ferroelectric switching was further confirmed via butterfly shape capacitance–voltage (C-V) loops and polarity-sensitive wet etching. The realization of ferroelectric, Y-doped AlN films further extends the family of nitride ferroelectrics and unravels a wealth of intriguing opportunities in III-nitride based electronic, piezo-electronic, and optoelectronic devices.

Modified Babinet Principle for Complementary Antennas in a Dielectric Half-Space

In this letter, the modified Babinet principle is applied to complementary antennas on the substrate interface. First, it is verified that the existing Babinet principle only holds for complementary metallic elements in the homogenized substrate. Then, the effective relative permittivity is introduced into the substrate interface through the zero-thickness effective substrate, which can keep the electromagnetic behavior (such as total electrical field and surface current density) of metallic element unchanged. Thereby, the modified Babinet principle can be established for arbitrary complementary metallic elements on the substrate interface. Finally, the proposed theory is applied to input impedances of complementary antennas on the substrate interface. The simulation strongly supports the proposed theory, regardless of the substrates and antenna sizes. The study not only establishes the modified Babinet principle for complementary metallic elements on the substrate interface, but also clarifies the electromagnetic influence of effective relative permittivity for the metallic element at the substrate interface.

Influence of low electric field parts of electric field–current density curves of superconductors on their ac loss characteristics

We performed numerical electromagnetic field analyses to investigate the influence of the low electric field parts of the electric field (E)–current density (J) curves of superconductors on their ac loss characteristics. A simple one-dimensional model across the width of a coated conductor was used for the analyses. Whereas we fixed the n value of the high E part of E–J curves of superconductors, we varied the n values of low E parts. J distributions as well as E distributions were calculated in coated conductors carrying ac currents and/or exposed to ac magnetic fields. We examined the influence of the n values at low E part of E–J curves on ac loss characteristics and discussed the electric field regions that are relevant to ac loss generation. We also discussed the applicability of the results to copper-plated multifilament coated conductors.

Effect of Sc2O3 doping on the microstructure and electrical characteristics of ZnO linear resistors

Herein, to improve the electrical characteristics, ZnO linear resistors mixed with MgO, TiO2, Al2O3, and various concentrations of Sc2O3 (with 0, 0.35, 0.7, and 1.05 wt %) were obtained using the conventional solid-state sintering technique, while the influences of Sc2O3 doping on the micro-morphology and electrical characteristics was investigated in detail. The crystalline phases and microstructure were investigated by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). The dielectric properties and electrical characteristics were evaluated using a precision inductance-capacitance-resistance meter and a high-voltage source meter. Results from SEM micrographs, XRD patterns, and EDS mappings illustrated that the doping of Sc2O3 hinders the growth of ZnO grains. Electric field-current density and resistivity-frequency measurements illustrated that the doping of Sc2O3 improves the linear performance of ZnO linear resistors and increases its grain resistivity and grain boundary resistivity. With Sc2O3 doping, the dielectric properties of the samples are significantly affected, while the resistance-temperature features reveal the negative temperature constant function. By appropriate Sc2O3 doping, the ZnO linear resistors exhibited excellent performance with grain boundary barrier height φb of 0.0106 eV, nonlinear coefficient α of 1.03, and resistance temperature constant αT of −2.88 × 10−3. It is beneficial to investigate the influence of Sc2O3 doping on the micro-morphology and electrical performances in detail for the preparation of zinc oxide linear resistors with superior performance.

Study of Electrical Characteristics for Dual-Gate TFTs With Asymmetric Defect Distributions and Gate Work Functions

Combined effects of asymmetric defect distributions and asymmetric gate work functions (WFs) on the performances of self-aligned dual-gate poly-Si TFTs are investigated. Normally, small grains with plentiful grain boundaries (GBs) or other structural defects appear at different positions of the poly-Si film, which is dependent on the growth process of the film. Subgap states of acceptor-like tail, acceptor-like deep-level, donor-like tail, and donor-like deep-level states are used to emulate the defects. Two sets of density of states (DOS) are employed. We find that defects at different positions of the source-side and drain-side channels exhibit different influences on TFT performance and the influences are dependent on the WFs of the gates. TFTs with a higher gate WF can have a higher tolerance to the depth of the defect region. Besides the electrical characteristics, the combined effects of defects and gate WFs on current density distributions and electric field distributions in the channel regions are explored. The performance variations caused by the asymmetric defects along with asymmetric gate WFs can be explained.

Alteration in growth temperatures of metal-organic decomposed GaxCe1-xOyNz passivation layer in nitrogen/oxygen/nitrogen ambient

A quantitative analysis of the morphology, topography, and electrical characterization of the metal-organic decomposed quaternary GaxCe1-xOyNz passivation layer grown on Si substrate in nitrogen/oxygen/nitrogen ambient at temperatures of 600, 700, 800, and 900 °C was carried out. Incorporation of nitrogen into the passivation layer was more prominent at lower temperatures by either attaching to oxygen vacancies sites or staying as dangling bonds in the passivation layer. The increase of annealing temperature to 800 and 900 °C enhanced the adsorption of oxygen to occupy the oxygen vacancies and hence, limiting the incorporation of nitrogen. As a consequence, formation of SiO2 took place at the interface between GaxCe1-xOyNz and Si substrate, degrading the k value of the passivation layer. The largest k value was perceived by the passivation layer annealed at 700 °C, accompanied with the acquisition of the highest positive effective oxide charges and considerably low interface trap densities and low trap density as well as large band gap, which led to an improvement in the current density-electric field (J-E) performance.

Simulation research on corrosion and thinning characteristics of water wall tubes based on electric field array

During service, the water wall tube will inevitably corrode due to various corrosive gases such as SO2, HCl, H2S, etc. To prevent the occurrence of tube burst accidents caused by thinning and income-pressure resistance of the water wall tube, it is necessary to monitor the wall thickness of the water wall tube row in real-time. This paper proposes an array-based method for monitoring the thickness of the water wall tube row, and the different corrosion characteristics models of the water wall tube row are established by using the finite element analysis software Maxwell. Based on the model, the influence of tube wall thickness and material on measurement accuracy is analyzed by current density distribution and electric field intensity. The error of calculation formula is analyzed by simulating different corrosion conditions of tube wall thinning. The calculation formula of the wall thickness after the corrosion of the water wall tube row and the correction formula of the wall thickness of a single water wall tube with the correction coefficient α of 3 are determined. And put forward to define the ”generalized average thickness” of the water wall corrosion of multiple tubes, and determine the correct formula for calculating the thickness of the water wall tube row with a correction coefficient β of 0.85 to 0.95.

Divulging the Potential of Sodium Carbide Thin Film for Semiconductor Applications

The work reported in this article is an attempt to introduce the least explored sodium carbide as a thin film and to explore its semiconducting behavior. The sodium carbide thin film deposited by the radio frequency sputtering technique is subjected to morphology, structure, and spectroscopic characterizations. The floral petal‐like morphology, understood from the field‐emission scanning electron microscopy and atomic force microscopy images, helps in enhancing interaction with the radiation that is revealed through the UV–visible absorption spectrum. X‐ray diffraction, photoelectron and Raman spectroscopic analyses confirm that the film is sodium carbide. The optical emission behavior of the sodium carbide thin film in the blue region is unveiled through the photoluminescence spectrum, power spectrum, color purity, and chromaticity diagram. Employing the refractive index and extinction coefficient values from the specular reflectance data, optical and electrical conductivities, nonlinear refractive index, linear and nonlinear optical susceptibility, dissipation factor, and surface and volume energy loss functions and their wavelength dependence due to interfacial polarization are investigated. The transfer matrix method is used to understand the spatial variation of the induced electric field and optical current density.

An Improved Calculation Method Based on Newton–Raphson Method for Ion Flow Field of UHVDC Transmission Lines at High Altitude

The fast and accurate solution of the total electric field and ion current density is crucial for the electromagnetic environment of ultra high voltage direct current (UHVDC) transmission lines. In this article, an improved method based on Newton–Raphson method (NRM) and upstream finite element method (UFEM) is proposed to calculate the ion flow field under complex conditions. According to the gas motion theory, the corona-onset electric field, ion mobility, and recombination coefficient are obtained at high altitude and put into the ion flow field model in this article. Subsequently, the charge density is used to solve Poisson’s equation, and the current continuity equations are calculated by UFEM. After that, the charge density of the conductor surface is updated based on NRM. These three parts are iterated repeatedly until the convergence conditions are met. According to the test results of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 800-kV UHVDC transmission line at high altitude, the validity and rationality of the proposed method are verified. The result demonstrates that due to the reduction of atmospheric pressure at the high altitude, the corona-onset electric field decreases, and the ion mobility and recombination coefficient increase, which makes the total electric field and ion current density at ground level increase. Compared with the traditional methods, the improved method is insensitive to the initial value of the surface charge density. Moreover, this proposed method can effectively improve the convergence ability and achieve the stable and fast calculation of the ion flow field at high altitude.

Calculation of the Electric Field Strength and Current Density Inside a Thin Metal Layer, Taking into Account the Skin Effect

Calculation of the Electric Field Strength and Current Density Inside a Thin Metal Layer, Taking into Account the Skin Effect

Calculation of the Electric Field Strength and Current Density Inside a Thin Metal Layer, Taking into Account the Skin Effect

For the first time, the problem of the distribution of the electric field and electric current inside a thin metal layer in the presence of the skin effect is solved, taking into account the mirror-diffuse nature of the reflection of electrons from the inner surfaces of the layer. Limiting cases are considered and the results obtained are discussed.

Electrodeposited 3D lithiophilic Ni microvia host for long cycling Li metal anode at high current density

The uneven deposition of Li metal is the main reason leading to Li dendrite growth, dead Li formation and infinite volume change, shortening the Li metal battery lifetime and causing catastrophic safety hazards. The widely studied 3D micro-nanostructured lithiophilic Li metal anode hosts can suppress the Li dendrite growth, however, it could barely endure high-rate cycling due to the exacerbated uneven deposition of Li metal at a high current density. Herein, we report an electrodeposited 3D microvia structured lithiophilic Ni skeleton on planar Cu with a nanoscale surface roughness as Li metal anode current collector. The high specific surface area and nanoscale rough surface can achieve both low local current density and uniform electric field distribution, which contribute to the even deposition of Li metal at a high current density. Additionally, the in-situ formed Ni(OH)2 thin layer during electrodeposition is lithiophilic, which could induce the uniform Li nucleation. This 3D lithiophilic Ni microvia (3D NMV) host endow the Li metal anode with long cycling performance for over 830 cycles at an ultra-high current density of 10 mA cm−2. Our work illustrates the synergic effect of 3D structure and surface flatness in achieving high-rate cycling performance.

Electro-assisted catalytic oxidation of flue gas desulfurization-derived magnesium sulfite using cobalt ferrite as catalyst under moderate condition

The catalysts were prepared by supporting cobalt ferrite (CoxFe3−xO4) on the surfaces of sphere mesoporous silica (MCM−41) nanoparticles. The electro-assisted catalytic oxidation of MgSO3 displayed an improved oxidation rate under moderate temperatures. Electric field and CoFe2O4/MCM−41 exhibited a beneficial synergistic effect because the associated MgSO3 oxidation rate is 3.38 times the oxidation rate when only the electric field was present, and 1.83 times the oxidation rate when only the catalyst was present. The cyclic voltammetry results proved that the catalysts reduced the oxidation potential of SO32− in the presence of an electric field, and increased the electron transfer rate in the oxidation. Both the X-ray photoelectron spectroscopy (XPS) characterization and free radical scavenging experiment results indicated that Co2+ served as the initiator in the generation of superoxide ions (O2−·), which was the primary active free radical responsible for the oxidation of SO32−. The electron spin resonance (ESR) spectra showed that the electric field and high current density expedited the production of O2−·. The XPS results convincingly demonstrated that the electric field effectively alleviated the catalyst deterioration, and, as a result, significantly improved the catalyst's recyclability. Lastly, the synergistic mechanism between the electric field and the catalyst in the catalytic oxidation of MgSO3 was explored.