Electric Field Characteristics Research Articles

Drive current enhancement of Si MOSFETs by using anti-ferroelectric gate insulators

Si MOSFETs with anti-ferroelectric (AFE) gate insulators are expected to improve drive current without any hysteresis of off-currents at a gate voltage of 0 V. The contribution of AFE gate insulators to the on-current (Ion) of Si MOSFETs is examined using simulations based on simple analytical models of polarization–electric field (P–E) characteristics. Improvement in Ion would not be expected given the experimental AFE characteristics of Hf1−xZrxO2 (HZO) reported so far because the switching polarization (PAFE–FE) is too high. On the other hand, a minor loop of the P–E characteristics of HZO can increase Ion without any hysteresis in the off-current. Also, when the value obtained by dividing PAFE–FE by the elementary charge (PAFE–FE/q) is ∼1–2 × 1013 cm−2, AFE gate insulators are expected to significantly improve the drive current of Si MOSFETs and suppress a significant increase in the gate leakage current, because the polarization switch associated with the transition from the AFE to the FE phase can enhance the surface carrier concentration of inversion layers as well as reverse the direction of the slope of the band edge of the insulators.

Effects of Annealing on Ferroelectric Hafnium–Zirconium–Oxide-Based Transistor Technology

In this letter, we investigate annealing effects in ferroelectric HfZrO x dielectric in metal–insulator–metal devices and metal–oxide–semiconductor capacitors by comparing two annealing methods: rapid thermal annealing (RTA) and microwave annealing (MWA). The tradeoff characteristics between the annealing conditions, polarization–electric field characteristics, gate leakage current, and interface state density ( ${D} _{\textsf {it}}$ ) are discussed. We show that: 1) a positive correlation between the remanent polarization (Pr), the gate leakage current, and ${D}_{\textsf {it}}$ as the annealing temperature (RTA) and the annealing power (MWA) increase and 2) the MWA is promising for ferroelectric transistors technology, since its low thermal budget can minimize ${D}_{\textsf {it}}$ and avoid increase in the gate leakage current.

Verification of measurement waveforms of transient electric field caused by micro‐gap spark using optical electric field probe

AbstractWith the widespread use of wearable terminals, machine to machine (M2M) and internet of things (IoT) equipment, electrostatic discharge (ESD: Electrostatic Discharge) due to electrification of humans and objects can cause electromagnetic interference (EMI) inside these devices, which is called intra‐EMC (Electromagnetic compatibility). This type of the EMI issue would be often derived from a steep transient electric near field generated by less than 1 kV spark discharges between micro‐gaps. To clarify the characteristics of such electric near field, therefore, an optical electric field probe, which does not disturb any electromagnetic fields to be measured, has been used to measure the transient electric field caused by a micro‐gap spark when charged metal spheres collide, while it is not fully understood whether or not the probe output precisely responds to the transient electric field in the vicinity of the discharge point. In this study, the measured waveforms of the above‐mentioned electric field are verified by comparison with the electrostatic field theoretically derived from image charges and the transient electric field calculated from an image dipole charge model combining a spark resistance law. The result reveals that at a distance near the discharge point the optical field probe does not properly work due to the presence of the electrostatic field, whereas the transient electric field at a distance away from more than twice the diameter of metal spheres from the discharge point can be correctly measured because of sufficient attenuation of the electrostatic field component.

Synchronized Two‐Station Optical and Electric Field Observations of Multiple Upward Lightning Flashes Triggered by a 310‐kA +CG Flash

AbstractA positive cloud‐to‐ground (+CG) lightning flash containing a single stroke with a peak current of approximately +310 kA followed by a long continuing current triggered seven upward lightning flashes from tall structures. The flashes were observed on 4 June 2016 at the Tall Object Lightning Observatory in Guangzhou, Guangdong Province, China. The optical and electric field characteristics of these flashes were analyzed using synchronized two‐station data from two high‐speed video cameras, one total‐sky lightning channel imager, two lightning channel imagers, and two sets of slow and fast electric field measuring systems. Three upward flashes were initiated sequentially in the field of view of high‐speed video cameras. One of them was initiated approximately 0.35 ms after the return stroke of +CG flash from the Canton Tower, the tallest structure within a 12‐km radius of the +CG flash, while the other two upward flashes were initiated from two other, more distant tall objects, approximately 18 ms after the +CG flash stroke. The initiation of the latter two upward flashes could be caused by the combined effect of the return stroke of +CG flash, its associated continuing current, and K process in the cloud. Each of these three upward flashes contained multiple downward leader/upward return stroke sequences, with the first leader/return stroke sequence of the second and third flashes occurring only after the completion of the last leader/return stroke sequence of the preceding flash. The total number of strokes in the three upward flashes was 13, and they occurred over approximately 1.5 s.

Electric Field Distribution Characteristics and Space Charge Motion Process in Transformer Oil Under Impulse Voltage

The electric field and space charge dynamics characteristics in oil under impulse voltage are key factors to the transformer insulation design, which are mainly obtained through simulation, falling short of experimental verifications. Applying the Kerr electro-optic method, the present paper carried out an actual measurement for the electric field characteristics in transformer oil under impulse voltage and managed to obtain their correlations with an electrode material, voltage amplitude, and wave-front time, respectively. First, it was found that, under impulse voltage and in pure transformer oil, the aluminum electrode had the largest amount of charge injection, followed by stainless steel and then copper, which was attributed to the different work functions of metal elements in electrodes. Second, with the increase of voltage amplitude, the effect of the space charge on the intermediate electric field of the oil gap was first enhanced, then weakened, and eventually enhanced. Third, as the wave-front time was prolonged, the peak of electric field in transformer oil showed a downward trend. For instance, the peak value of the electric field was reduced by 17.6 % when the wave-front time was increased from 0.5 μs to 40.0 μs. The reason is that when the wave-front time is longer, the amount of injected charge grows larger and the weakening effect becomes stronger. Fourth, a charge dynamic motion model in transformer oil under impulse voltage was established to demonstrate its spatial-temporal effects on the electric field. Besides, this paper has clarified the source of the negative and positive charges in the transformer oil under impulse voltage by using the theories of field emission and field ionization. Moreover, the variation of electron mobility over-voltage amplitude, wave-front time, and spatial distribution was worked out to present the quantitative results of its motion process.

Theoretical aspects of monitoring synergistic processes in the rock massif

In this article, the grounds for considering of rocks massif as a nonlinear medium with dissipative properties have been shown that as a result of the combined influence of normal and tangential stresses around the workings, synergistic effects are observed with the formation of similar structures, which leads to the appearance of a quasi-stationary damped stress wave, and this , in turn, makes it possible to predict the nature of changes in the stress-strain state of the rock massif in space-time continuum. Taking into account the influence of the mining operations speed, a theoretical justification for diagnostics the physicomechanical properties and the stress state of sedimentary rocks has been developed by using the dynamic and kinematic characteristics of acoustic and electric fields. The theoretically established relationship of the stress state of massif of quartz-containing rocks with its elastic and electrical parameters follows taking into account the damped wave nature of the processes around the mine workings. Obtained results indicates the principal possibility of quantitative assessment of stress components acting in the rock massif using determined physical parameters of the massif.

Frequency-Time Domain Characteristics of Radiated Electric Fields in a Multi- Terminal MMC-HVDC Station

A multi-terminal modular multilevel converter-based high voltage direct current (MTDC) system has become a popular research topic. Improvements to the voltage level and capacity have attracted increasing attention to its radiated electromagnetic disturbances. This paper discusses the measurements and analysis of the radiated electric field characteristics for an MTDC station. The control frequency causes the electric field to peak at multiples of 10 kHz, which reach approximately 80–90 dB $\mu \text{V}$ /m with an interval time of $100~\mu \text{s}$ . In addition, the distribution characteristics and influencing factors of the radiated electric fields are also analyzed. The field decreases the fastest within 15 m as the distances from the hall increases. In addition, the electric field in the valve hall has obvious directionality under the influence of radiation structures and disturbance source characteristics. When the normal line of the loop antenna is perpendicular to the phase bus, the electric fields at multiples of 10 kHz are the largest. The radiated electric field intensity of this MMC station meets standard requirements.

Simulation of 3D-Silicon sensors for the TIMESPOT project

Abstract The experimental conditions in future High Luminosity LHC experiments require new detector systems with increased performances compared to the current state of the art. In this context, increasing spacial resolution and including time measurement with a resolution of less than 50 ps for particle tracking systems can avoid false track reconstruction due to event pile up. For this kind of future tracking detectors the 3D silicon sensor technology appears as a good option. In this context the TIMESPOT initiative was launched. Concerning the development of the sensor, different geometrical solutions have been explored and simulated to optimize the timing response of the single pixel sensor using Sentaurus TCAD. The configuration with the best electric field characteristics for timing was selected for signal simulation. In order to compensate the very time-consuming behavior of TCAD simulations, a faster charge transport simulator with TCAD and Geant4 support is under development. Further sensor configurations, including a first primitive capacitive and resistive load, were also simulated and evaluated. This paper shows a general overview of the project with particular attention to the silicon sensor development. First results are presented.

Vortex dynamics driven by AC magnetic field in YBCO thin films with complex pinning structures

We investigated the AC magnetic response of a YBa2Cu3O7 film with embedded BaZrO3 nanorods and Y2O3 nanoparticles at a static magnetic field Hdc lower than the matching field HΦ. We proposed a practical formula for the determination of the induced current J during AC susceptibility measurements, which allows us to directly obtain the pinning potential Uc from the characteristics of electric field E versus J. We show that the dynamic critical current Jd induced at the depinning frequency fd can be experimentally obtained by measuring m′(T) and m″(T) at different frequencies and amplitudes. It was found that the value of fd obtained by extrapolation of J to Jd in the PHz domain is much higher than the frequency reported for ordinary YBa2Cu3O7 thin films as determined by microwave impedance measurements.

Discharge voltage prediction of complex gaps for helicopter live-line work: An approach and its application

Complex gap discharge voltage is an important parameter to determine the approach path and the minimum air insulation distance for helicopter live-line work (HLLW) by platform method. This paper proposes a novel approach for discharge voltage prediction of complex gaps with a floating object, combining electric field calculation, feature extraction, machine learning and intelligent prediction based on support vector machine (SVM). The methodology is performed by twice electric field calculations and SVM predictions to obtain the withstand voltages of the primary gap and the secondary gap, thus to compute the dielectric strength of the complex gap. A simulation model of the HLLW platform near the 1000kV UHV AC transmission line is presented for electric field calculations, and some electric field features (EFF) are extracted from the calculation results to parameterize the complex gap configuration. Taking the EFF as input variables, a SVM model is applied to predict the switching impulse discharge voltages of different gap configurations relevant to HLLW. The validity of the proposed methodology is demonstrated through comparison with the experimental results. This study offers a possible way to determine the minimum safe gap distance for HLLW by numerical calculation rather than costly and time-consuming experiments.

Observations of Impulsive Electric Fields Induced by Interplanetary Shock

AbstractWe investigate the characteristics of impulsive electric fields in the Earth's magnetosphere, as measured by the Van Allen Probes, in association with interplanetary shocks, as measured by Advanced Composition Explorer and Wind spacecraft in the solar wind from January 2013 to July 2016. It is shown that electric field impulses are mainly induced by global compressions by the shocks, mostly in the azimuthal direction, and the amplitudes of the initial electric field impulses are positively correlated with the rate of increase of the dynamic pressure across the shock in the dayside. It is also shown that the temporal profile of the impulse is related to the temporal profile of the solar wind dynamic pressure, Pd. It is suggested that during the first period of the impulse, the evolution of the electric field is directly controlled by external solar wind forcing, and thus, finite rates of change of Pd should be considered in the study of the interactions between solar wind and magnetosphere. The implications of shock‐induced impulsive electric fields on the acceleration and transport of radiation belt electrons are also discussed.

Electric Field Characteristics of an Arc-Induction-Type DC Circuit Breaker Combined with a Magnet for Stability in the DC Power Grid

For stability in the direct current (DC) power grid, it is very important to limit the current of the fault section and to protect the system in the fault condition. That is the core technology of the DC power grid. This paper suggests characteristics and a limited range of the fault current for the new model as the significant protecting technology in the DC power grid. Such new model is the arc-induction-type DC circuit breaker (CB) combined with a magnet. The magnetic arc-induction-type direct-current circuit breaker (DCCB) consists of a neodymium magnet, an induction needle, and electrical contacts. During fault operation, the arc occurring between the contacts is induced to the induction needle. To increase the induction effect, Lorentz force is applied to blow the arc. A magnet was applied to reduce the initial fault current and to induce magnetic flux. The simulation data were analyzed using the Maxwell 3D software program. The electric field included the electric force and the electric charge. Therefore, it could analyze the arc as the electric field. The simulation was performed based on the preceding study on induction needle. As a result of the simulation, it was confirmed that the electric field value of the induction needle increased when the DCCB was combined with a magnet.

A dielectrophoretic study of the carbon nanotube chaining process and its dependence on the local electric fields

The chaining process of a system of interacting carbon nanotubes (CNTs) under an alternating current electric field is investigated at two regions of different electric field characteristics. For the region of uniform electric field (far from the electrodes), a two-dimensional multiparticle approach based on the dielectrophoretic (DEP) theory and classical mechanics is proposed to investigate the CNT rotational and translation motion. For this scenario, CNT rotation and alignment along the electric field direction occurs first, followed by the translation and chaining processes which were found to be highly dependent on the CNT-to-CNT initial configuration. On the other hand, the presence of high electric field gradients governs the CNT chaining at regions near the electrodes. DEP forces caused by such gradients were computed by finite element analysis and compared to the magnitude of the CNT-to-CNT interacting forces at zones of uniform electric fields. A critical distance of CNT-to-CNT separation was estimated, which determines if a CNT is attracted towards the electrode or if it is attracted by other CNTs away from the electrodes. Experimental evidence of CNTs dynamic motion under electric fields is presented to support the predicted trends.

The effect of double doped nc-Si:H tunnel recombination junction in a-Si:H/c-Si tandem solar cells

In this study, tunneling mechanisms controlling the a-Si:H thin film/c-Si tandem solar cell were investigated employing numerical simulation. First, the effect of doped nc-Si:H tunnel recombination junction (TRJ) was studied with different structures. The band diagram, electric field, and recombination rate characteristics were investigated under a dark condition with doped nc-Si:H TRJ. The trap-assisted model and field-dependent tunneling were used to model the recombination and transport influence of the valence band offset (ΔEV) between the p-type layer of the top cell and TRJ in the high field region. Simulation results showed that the highest efficiency of 23.98% (Short circuit current density, Jsc = 18.74 mA cm−2, open circuit voltage, Voc = 1.565 V, fill factor, FF = 81.76%) could be obtained in the case of n/p nc-Si:H TRJ.

A full hydrodynamic steady-state model of positive dc corona in coaxial cylindrical electrode

The predictions of the steady-state distributions of the space charge and electric field in the coaxial cylindrical electrode are significant in many industrial applications. The positive dc corona in the coaxial cylindrical electrode is modeled by a full hydro-dynamic steady-state model and solved by the fourth-order Runge-Kutta method and the central finite difference approach. The new model predicts the distributions of the space charge and electric field in the whole electrode space. The effects of the electron diffusion, positive and negative charge recombination, and space photoionization are compared with the simplified model. The results present that the calculation accuracy of the new model is superior to that of the simplified model especially under large current. The simulation results also exhibit the influence of the corona current and conductor radius on the distribution of space charge and electric field and voltage-current characteristics.

Electric Field Distribution and Switching Impulse Discharge under Shield Ball Surface Scratch Defect in an UHVDC Hall

The dimension and surface state of shielding fittings in ultra high voltage direct current (UHVDC) converter station valve halls have a great influence on their surface electric field and switching impulse characteristics, which are important parameters confirming the air gap distance in the valve hall. The characteristics of impulse discharge under different lengths, dent degrees and burrs around the scratches of Φ1.3 m shield balls with a 2 m sphere-plane gap length were tested, in the UHVDC testing base of the Hebei Electric Power Research Institute. The discharge characteristics under the influence of the surface scratches of the shield ball were obtained. The results demonstrate that the discharge voltage of sphere-plane gap decreases obviously when there are unpolished scratches on the surface of the shield ball. However, when the scratches are polished, the discharge voltage has no significant impact. At the same time, a 1:1 full-scale impulse test model was established based on the finite element method. The electric field intensity and the space electric field distribution of the shield ball were obtained under the influence of scratches with or without burrs. The results of the simulation show that when the surface of the shield ball is smooth, the electric field distribution around it is even. The electric field intensity on the surface of the shield ball increases obviously when there are burrs around the scratches. When there is no burr around the scratches, the length and depth of the scratches have no obvious effect on its electric field distribution. Meanwhile, calculation results are consistent with test results. The results can provide an important basis for the design and optimization of shielding fittings, and technical support for its localization.

Interface properties of SiO2/GaN structures formed by chemical vapor deposition with remote oxygen plasma mixed with Ar or He

The impacts of noble gas species (Ar and He) on the formation of a SiO2/GaN structure formed by a remote oxygen plasma-enhanced chemical vapor deposition (ROPE-CVD) method were systematically investigated. Atomic force microscopy revealed that ROPE-CVD with He leads to a smooth SiO2 surface compared with the case of Ar. We found that no obvious oxidations of the GaN surfaces after the SiO2 depositions with the both Ar and He cases were observed. The capacitance–voltage (C–V) curves of the GaN MOS capacitors formed by ROPE-CVD with the Ar and He dilutions show good interface properties with no hysteresis and good agreement with the ideal C–V curves even after post deposition annealing at 800 °C. Besides, we found that the current density–oxide electric field characteristics shows a gate leakage current for the Ar case lower than the He case.

S156. Electric field induced by rotating permanent magnet stimulation systems

Introduction Conventional magnetic neurostimulation systems use a current-carrying coil to generate a time-varying magnetic field pulse, which in turn produces a spatially varying electric field in the nervous system. An alternative approach to generating the time-varying magnetic field is by means of moving permanent magnets. Several systems have been proposed, involving rotation of high-strength neodymium magnets. One of these systems, termed synchronized transcranial magnetic stimulation (sTMS), was explored as a treatment of major depressive disorder. In this work, we evaluate the electric field characteristics of sTMS using the finite element method. Methods The finite element model was implemented in COMSOL Multiphysics (COMSOL, Burlington, MA) using its version of the IEEE Specific Anthropomorphic Mannequin phantom. The head model (stator) has uniform, isotropic electrical conductivity of 0.33 S/m and relative permeability of 1. Three cylindrical magnets (rotators) are positioned along the midline: Magnet 1 is located over the frontal pole just above the eyebrows. Magnet 2 is 7.1 cm away from Magnet 1, approximately overlying the superior frontal gyrus. Magnet 3 is 9.2 cm away from Magnet 2, approximately overlying the parietal cortex. Each magnet is 2.54 cm in diameter and height, diametrically magnetized, with a residual flux density of 0.64 T. The axes of rotations are perpendicular to the sagital plane; and the rotation velocity is set to 10 Hz, corresponding to approximately peak alpha frequency. Results The electric field distribution of a single rotating magnet was first simulated in a sphere head model with radius of 8.5 cm. As the magnet rotates, the electric field switches from a figure-8 pattern (when the magnetic dipole is perpendicular to the head sphere at multiples of half-period) to a circular pattern (when the magnetic dipole is parallel to the head at multiples of quarter-period). The peak induced electric field strength at the surface of the head is approximately 0.05 V/m, in the direction parallel to the rotation axis of the magnet. The electric field distribution of the full sTMS configuration in the SAM head model shows broadly distributed over midline frontal polar, medial frontal, and parietal regions. The peak induced electric field strength at the surface of the head is approximately 0.06 V/m. At a depth of 1.5 cm from the head surface, corresponding to the depth of the cortex, the electric field strength attenuates to approximately 0.02 V/m. Conclusion We evaluated the electric field characteristics of the sTMS system of rotating magnets using the finite element method. We found that the maximum induced electric field strength at the level of the cortex is approximately 0.02 V/m, which is an order of magnitude lower compared to those delivered by transcranial current stimulation and low field magnetic stimulation. Direct electrophysiological data should also be collected to validate the proposed mechanism of action.

Determination of Threshold Electric Field for PPLP Specimen in Liquid Nitrogen Based on the Measurement of Electrical Conductivity

The externally applied electric field causing sudden increase in electrical conductivity is called the threshold electric field. And the information of this threshold electric field is very important for reliable insulation design of dc power apparatus because dc electric field distribution is governed by electrical conductivity of the insulating material. There are several reports on the threshold electric field of XLPE and polymeric materials used for dc power cables, operated at room temperature. However, there are no previous works on threshold field of cryogenic insulating materials, which is necessary for the reliable insulation design of a superconducting dc cable. Therefore, in this study, we tried to determine the characteristics of threshold electric field of a polypropylene laminated paper (PPLP) specimen in liquid nitrogen by varying the number of PPLP layers. From the experiments, we could observe that there exists the threshold electric field of PPLP in a cryogenic environment. Furthermore, it was found that there was no difference in the measured threshold electric field in spite of different number of PPLP layers. In addition, it was found that if electrical stress exceedes the threshold field on PPLP specimen, the conductivity can be varied according to the number of PPLP layers.

High thermal stability of abrupt SiO2/GaN interface with low interface state density

The effects of postdeposition annealing (PDA) on the interface properties of a SiO2/GaN structure formed by remote oxygen plasma-enhanced chemical vapor deposition (RP-CVD) were systematically investigated. X-ray photoelectron spectroscopy clarified that PDA in the temperature range from 600 to 800 °C has almost no effects on the chemical bonding features at the SiO2/GaN interface, and that positive charges exist at the interface, the density of which can be reduced by PDA at 800 °C. The capacitance–voltage (C–V) and current density–SiO2 electric field characteristics of the GaN MOS capacitors also confirmed the reduction in interface state density (Dit) and the improvement in the breakdown property of the SiO2 film after PDA at 800 °C. Consequently, a high thermal stability of the SiO2/GaN structure with a low fixed charge density and a low Dit formed by RP-CVD was demonstrated. This is quite informative for realizing highly robust GaN power devices.