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Triangularity is an important shaping parameter in tokamak plasmas that affects the edge plasma state. In this work, we utilize the BOUT++ code to study the effect of positive and negative triangularity on the peeling–ballooning modes with H-mode profiles. The model equilibria with a JET-like geometry are self-consistently generated by the CORSICA equilibrium code, with a fixed pressure profile when varying triangularity. The linear simulations reveal that increasing positive triangularity results in the increase in magnetic shear and decrease in radial electric field (Er) curvature, leading to the stabilization of the peeling–ballooning modes. On the contrary, the increase in negative triangularity results in a destabilizing effect due to the decrease in magnetic shear and increase in Er curvature. It is found that the modification of Er shear due to triangularity variation cannot impact edge stability significantly. The nonlinear simulations further demonstrate that more positive triangularity results in reduced nonlinear energy loss fraction or pedestal collapse, while more negative triangularity results in increased nonlinear energy loss fraction or pedestal collapse. These results provide qualitative insights into experimental observations of the high pedestal pressure profiles with positive triangularity configuration and restricted low pedestal pressure profiles with negative triangularity configuration. [ABSTRACT FROM AUTHOR]

The vertical stacking of different two-dimensional materials to construct van der Waals heterostructures (vdWHs) opens up a promising platform for designing high-efficiency photocatalysts. Direct Z-scheme heterostructures for photocatalytic dissociation have received much attention in recent years, in which charge carriers migrate directly between two semiconductors without redox mediators. Here, the electronic and optical properties as well as the solar-to-hydrogen conversion efficiency of g-GeC/ PtSe2 vdWHs are systematically investigated, especially for their high-efficiency visible-light water splitting catalyst features. Calculations show that the g-GeC/ PtSe2 vdWH is a semiconductor with an indirect band gap of 1.356 eV, featuring a type-II band alignment. The built-in electric field E int and band bending at the interface lead to a direct Z-scheme photocatalytic structure, and photocatalytic water splitting can be realized in the pH range of 0–14. In particular, with biaxial tensile strain ϵ = 4% applied, the g-GeC/PtSe2 vdWH possesses a smaller band gap, wider visible light response range and very high STH conversion efficiency (η STH) up to 49.07%, entirely satisfying the optimal photocatalytic water splitting conditions. This work provides a new perspective for designing promising direct Z-scheme visible light water splitting catalysts with a high-efficiency solar energy conversion, beneficially to the development of clean energy. [ABSTRACT FROM AUTHOR]

We carry out several numerical simulations to illustrate how the radial electric field (Er) impacts the edge magnetohydrodynamic (MHD) instabilities. The analyses reveal that Er-shear ( E r ′ , here the prime denotes the derivative with respect to the radial direction) tends to stabilize the kink / Peeling–Ballooning modes by dephasing the perturbed radial velocity ( v ̃ r ) and displacement ( ξ ̃ r ). However, Er-curvature ( E r ″ ) tends to destabilize the kink/peeling modes by inducing a phase lock between v ̃ r and ξ ̃ r . More specifically, the ratio between them could be measured to quantify their relative competition strength. Consequently, the shape of Er is crucial to the shape of linear growth rate spectrum γ (n) (here n is the toroidal mode number), which further determines the nonlinear dynamics. On the one hand, relatively larger Er-curvature causes narrower γ (n) , leading to larger nonlinear energy loss fraction. On the other hand, relatively larger Er-shear has the opposite effect. [ABSTRACT FROM AUTHOR]

• We fabricate PbZr 0.52 Ti 0.48 O 3 (PZT) based UV photodetectors via facile sol–gel technique. • Modulating PZT film thickness enhances ferroelectric properties, particularly reducing coercivity fields, thus improving photodetection. • External polarization enhances internal electric fields, effectively separating photogenerated carriers and boosting self-powered current. • Film thickness and ferroelectric polarization notably impact photodetector response times. Ferroelectric materials have great promise for use in photodetectors due to their built-in electric field-assisted carrier separation and switchable polarization properties. Carrier separation efficiency is a decisive factor in evaluating photodetector performance. The photodetector optoelectronic performance can be enhanced further by optimizing the thickness of the ferroelectric film to take full advantage of the switchable polarization properties of the ferroelectric material, and by enhancing the built-in electric field to drive carrier separation. In this work, we optimize the performance of PbZr 0.52 Ti 0.48 O 3 (PZT) photodetectors by modulating the thickness of the film. It is observed that thicker ferroelectric films have lower coercivity fields, which are more favorable for ferroelectric domain switching. On this basis, the ferroelectric properties of ferroelectric PZT films were optimized by thickness tuning, and the photodetection performance of PZT-based self-powered photodetectors was explored. It is found that the polarization enhances the internal electric field, driving photogenerated carrier separation and improving the self-powered current, while also selectively enhancing photodetectivity for devices of different thicknesses. Additionally, both film thickness and ferroelectric polarization significantly impact the response time. [ABSTRACT FROM AUTHOR]

In this paper, the effects of harmonic superimposed DC voltage on electrical tree growth characteristics in ethylene propylene diene monomer (EPDM) for HVDC cable accessories insulation are studied. Harmonic component with a frequency from 50 to 450 Hz is superimposed on DC voltage to analyze the mechanism of harmonic amplitude, order and voltage polarity on electrical tree growth. The results show that the electrical treeing process is promoted with an increase in harmonic amplitude and order, which brings a longer tree length and more accumulated damage to the insulation. Especially when the amplitude of harmonic component exceeds that of DC voltage, the electrical treeing processes are significantly deteriorated, resulting from the large amount of energy released by the recombination of hetero charges. The growth of electrical tree has an obvious polarity effect which tends to be branch-like tree under positive voltage and bush-like tree under negative voltage. The polarity effect may be caused by different propagation processes of electron avalanche under different voltage polarities. As harmonic order increases, the main channel of positive electrical tree is broadened, while the negative tree becomes denser with a lot of bifurcation. These results indicate that harmonic component accelerates the initiation and propagation of electrical tree by affecting the charge transport behavior under the superimposed electric field. [ABSTRACT FROM AUTHOR]

In the field of beam physics, two frontier topics have taken center stage due to their potential to enable new approaches to discovery in a wide swath of science. These areas are: advanced, high gradient acceleration techniques, and x-ray free electron lasers (XFELs). Further, there is intense interest in the marriage of these two fields, with the goal of producing a very compact XFEL. In this context, recent advances in high gradient radio-frequency cryogenic copper structure research have opened the door to the use of surface electric fields between 250 and 500 MV m−1. Such an approach is foreseen to enable a new generation of photoinjectors with six-dimensional beam brightness beyond the current state-of-the-art by well over an order of magnitude. This advance is an essential ingredient enabling an ultra-compact XFEL (UC-XFEL). In addition, one may accelerate these bright beams to GeV scale in less than 10 m. Such an injector, when combined with inverse free electron laser-based bunching techniques can produce multi-kA beams with unprecedented beam quality, quantified by 50 nm-rad normalized emittances. The emittance, we note, is the effective area in transverse phase space (x, px/mec) or (y, py/mec) occupied by the beam distribution, and it is relevant to achievable beam sizes as well as setting a limit on FEL wavelength. These beams, when injected into innovative, short-period (1–10 mm) undulators uniquely enable UC-XFELs having footprints consistent with university-scale laboratories. We describe the architecture and predicted performance of this novel light source, which promises photon production per pulse of a few percent of existing XFEL sources. We review implementation issues including collective beam effects, compact x-ray optics systems, and other relevant technical challenges. To illustrate the potential of such a light source to fundamentally change the current paradigm of XFELs with their limited access, we examine possible applications in biology, chemistry, materials, atomic physics, industry, and medicine—including the imaging of virus particles—which may profit from this new model of performing XFEL science. [ABSTRACT FROM AUTHOR]

To reduce the electric field concentration induced flashover in AC gas insulated line (GIL), a novel concept of surface functionally graded material (SFGM) is proposed in this paper, and the continuously graded high-Ä layer was fabricated by depositing BaTiO 3 on the insulator surface. The iterative method was introduced to optimize the thickness distribution of the BaTiO 3 layer. After four iterations, the layer thickness distribution almost reaches its optimal solution, and the maximum electric field strength is reduced by approximately 70% compared with that of the conventional insulator. To fabricate the optimized SFGM insulator, a rotatable baffle with the designed gap was placed above the insulator during the sputtering process. For comparison, a uniformly sputtered insulator with the 4μm BaTiO 3 layer and a discretely graded insulator with four gradients were prepared. Both electric field simulations and experiments were performed to evaluate the electrical performance of different insulators. The results show that, compared with the conventional insulator, the sputtered insulators, especially the optimized SFGM insulator, can significantly improve the uniformity of the electric field distribution along the insulator surface under a 50 Hz voltage. Accordingly, the discharge inception voltage and flashover voltage of the insulator both increased significantly. Under negative standard lightning impulse voltage (1.2/50 μs), the sputtered insulators show insulation performance comparable to that of the conventional insulator. [ABSTRACT FROM AUTHOR]

The influence of interface barrier on field emission of carbon nanotubes (CNTs) was investigated theoretically and experimentally. A double-potential barrier model was proposed to calculate the electron tunneling probability through the interface and surface barriers. The calculation result reveals that the difference of the electron tunneling probability through the two barriers is responsible for the nonlinearity of the Fowler–Nordheim (FN) plots for the field emission of the CNTs. To verify this model, a series of the CNTs were synthesized on the Si substrates covered with different thicknesses of SiO2 layers as the interface barrier. Based on their field emission properties, it was found that the FN plots of the field emission of these CNTs deviated from the FN law when the applied electric fields were over a critical value, which was strongly dependent on the thicknesses of the SiO2 layer. Therefore, the interface barrier has an important role in determining the field emission property of the CNTs. The experimental results are consistent with the calculation result based on the double potential model. [ABSTRACT FROM AUTHOR]

A phenomenon of field emission instability is reported. Field emission current oscillation was observed when a single zinc oxide (ZnO) one dimensional nanostructure operated at high current density. As a result, the radius curvature of the nanoemitter apex was sharpened to less than 15 nm. This indicates the oscillation was associated with melting of the emitter material. We found that the oscillation may be ascribed to (i) the behavior of charging and (ii) the shape changing of a metallic liquid ball that exists at the tip apex under high electric field. The net force of electric force and surface tension modifies the radius of the apex periodically, which results in the oscillation of field emission current. This finding may enhance the understanding of the physical process of field emission from ZnO nanostructures. [ABSTRACT FROM AUTHOR]

A method for switching between multiple spin polarization of the electric current injected into a semiconductor is proposed, based on injecting spins from a diluted magnetic semiconductor through a multiferroic tunnel barrier. We show that it is important to combine a diluted magnetic semiconductor electrode with a multiferroic barrier to realize multiple switching of spin polarization on wide range. The reversal of either electric polarization or magnetization in a multiferroic barrier results in a sizable change in the spin polarization of the injected current both in magnitude and in sign, thereby providing a four-state electrical control of spin polarization. The electroresistance and electromagnetoresistance effects can be also realized in this structure. Our investigations may stimulate experimental studies of the multiferroic tunnel junctions. [ABSTRACT FROM AUTHOR]

Superconducting coil is the core component of Tokamak device, and epoxy resin plays the role of mechanical support and electrical isolation. Inevitably, various defects introduced in the casting process of epoxy resin will cause partial discharge. The insulation failure in superconducting coil is mainly caused by continuous partial discharge. In this paper, the electrical conductivity of epoxy resin and the partial discharge characteristics in high magnetic field were investigated. The results show that the conductivity of epoxy resin increases with the increase of magnetic field strength. At the same magnetic field strength, the conductivity of epoxy resin decreases slightly with the increase of magnetic field angle. The partial discharge initiation voltage decreases with the increase of magnetic field, and decreases with the increase of magnetic field angle at the same magnetic field strength. [ABSTRACT FROM AUTHOR]

Nonlinear conductivity composites can be applied to modify the local electric field distribution and accelerate the surface and space charge dissipation in HVDC cables. This paper focuses on the effect of the nonlinear conductivity on the charge transportation under impulse superimposed on DC voltage. The surface-charge-accumulation property of silicone rubber (SiR)/SiC composites under impulse superimposed on DC voltage is studied. The surface potential decay (SPD) is measured after the sample is stressed by impulse superimposed on DC voltage. The effect of nonlinear conductivity on carrier mobility is analyzed. The results show that under DC voltage, the decay rate increases for the rise in the initial surface potential (ISP). Higher surface potential caused by higher impulse voltage leads to a larger nonlinear conductivity, which immediately dissipates the surface charge. The increase in DC voltage is shown to be more effective in accumulating surface charge than impulse. The vertical movement to the ground and the horizontal movement of surface charges are two factors affecting the ISP and SPD, which are both affected by the nonlinear conductivity of SiR/SiC composites. [ABSTRACT FROM AUTHOR]

We compared the resistive switching performances of built-in graded oxygen concentration TaOx films and uniform TaOx films under the 100 μA compliance current. The device with a graded oxygen concentration demonstrates increased low resistance and high resistance states, as well as improved stability without the need of higher switching voltages. Using the pulse mode, the switching voltages were confirmed to be less than 1.0 V for the pulse widths of 100 ns and 50 ns and less than 3.3 V for that of 10 ns, showing great advantages over previous reports. The remarkably high performances are due to the built-in oxygen concentration gradient, which results in an electric-field gradient and temperature along conduction paths, confining the rupture/reformation of the random conductive filaments to the customized highest oxygen concentration zone. [ABSTRACT FROM AUTHOR]

The surface charges that accumulate on polypropylene (PP) film can induce electrical field distortion and surface flashover, which accelerate the electrical aging of a capacitor. This paper investigated the effect of combined voltage on the surface charge behaviors and flashover voltage and a modification method to inhibit the accumulation of surface charge. The carrier mobility in different conditions was calculated using a surface potential decay process to analyze the transportation of surface charges. Samples that were fluorinated for 15, 30, 45 and 60 min and unfluorinated samples were prepared prior to experiments. The samples were corona charged with a pair of needle-plate electrodes by DC voltage and a combination of DC voltage and pulse voltage. The flashover experiments were performed under DC voltage, pulse voltage and superimposed voltage in atmospheric air. The results indicate that the maximum carrier mobility and maximum flashover voltage can be obtained when the samples are surface modified for 45 min. The surface charge density decreases with an increase in the carrier mobility under DC voltage. Under a combination of DC voltage and pulse voltage, the initial surface charge density is influenced by both the carrier mobility and the pulse voltage. The results suggest that surface modification for a certain time can significantly inhibit the surface charge accumulation, improve the carrier mobility and increase the flashover voltage. [ABSTRACT FROM AUTHOR]

A potential terahertz (THz) radiation source generated by mode conversion from laser to surface plasma waves (SPWs) is proposed. The radiation is produced by a two-color laser interaction with a grating. It is shown that the frequency of the THz radiation can be precisely controlled by the frequency difference of the two-color laser. Two-dimensional (2D) particle-in-cell (PIC) simulations are used to verify this mechanism and the results show that the amplitude of the THz electric field increases nonlinearly with the amplitude of the laser electric field, which theoretically means, before the mechanism fails, the intensity of the radiated THz radiation may reach to a pretty high level as long as the driven laser is intense enough. For our simulations, the intensity of the THz radiation is even more than 10% of the laser. Besides, further analysis shows this mechanism also can be used to generate electromagnetic radiation with many other required frequencies by modifying the period of the grating. [ABSTRACT FROM AUTHOR]

The addition of silicon carbide (SiC) micro powder into silicone rubber (SiR) matrix has been found to introduce a marked nonlinear conductivity into the resulting composites, without a degradation of the insulating properties under low electric field. Owing to these properties, the SiR-based nonlinear conductive composites have a potential use as the field grading material (FGM) layer in high voltage direct current (HVDC) cable accessories, which is employed to uniform electric field and suppress charge accumulation at the interface between crosslinked polyethylene (XLPE) and accessory insulation. In this paper, the space charge transportation and dissipation behaviors of SiC/SiR composites were investigated by pulsed electro-acoustic (PEA) test, in view of the effects of SiC filler size and crystal morphology. The results indicated that with the enhancement of nonlinear conductivity, the charge transportation and dissipation processes were accelerated. Compared with ?-SiC particles, the ?-SiC whiskers could provide a larger nonlinear conductivity. Meanwhile, the trap level distributions of SiC/SiR composites showed that the ?-SiC whiskers introduced a shallower trap level at 0.81 eV than the ?-SiC particles (0.85 eV). In addition, for the ?-SiC particles filled composites, with the increase of the filler size from 0.45 ?m to 5.0 ?m, the shallow trap density increased, and the deep trap density decreased, resulting in an enhancement of space charge dissipation. [ABSTRACT FROM AUTHOR]

One-dimensional modeling and simulations of the electric and weighting fields have been systematically carried out for 2D-Planar-Electrode and 3D type detectors. Poisson and Laplace equations have been solved analytically in Cartesian and cylindrical coordinates with well defined boundary conditions. It has been found that the electric field profile and full depletion voltage depend in general on the detector effective doping density (N e f f) and electrode spacing (λ C), while the weighting field depends only on the electrode spacing and relative geometry size of the collecting electrode with respect to the electrode spacing. For 2D-Planar-Electrode strip and pixel detectors, the full depletion voltage will be somewhat higher than that of 2D pad detectors, and the weighting field will be more concentrated near the collecting electrode due to the "small pixel" effect. For 3D-Trench-Electrode (cylindrical type) detectors, however, exact one-dimensional solutions have been obtained for electric and weighting fields. The results are compared to those obtained for 2D-Planar-Electrode pad detectors and conventional 3D-Column-Electrode detectors. [ABSTRACT FROM AUTHOR]

High temperature vulcanized (HTV) silicone rubber (SiR), due to its excellent electrical insulation, elasticity and temperature resistance, is used in cable accessories for HVDC cables. The space charge, generated under dc stress in SiR, would distort the local electric field, further influencing the characteristics of partial discharge and accelerating the insulation aging. This paper tried to modify the space charge behaviors of HTV SiR composites by incorporating silicon carbide (SiC) particles into the polymer matrix with the filler content of 10, 30, 50, 100 wt%. The effects of the SiC particle content on the field-dependent conductivity and the space charge behaviors of HTV SiR were studied. The conductivities under different electric fields were measured by a three-electrode system at room temperature and the space charge behaviors were observed by the pulsed electro-acoustic (PEA) method. The results indicated that the conductivity of SiR/SiC composites was a nonlinear function of electric field when the content exceeds 30 wt%. With the increase of filler content, the threshold field for nonlinear conductivity decreased and the nonlinear coefficient increased. Meanwhile, the amount of space charges was dramatically reduced. It is suggested that the SiR/SiC composites with nonlinear conductivity can improve the dc conductivity under high electric field, thus raising the carrier mobility and suppressing the accumulation of space charge. [ABSTRACT FROM PUBLISHER]

HTV silicone rubber (SiR), due to its better electrical insulation, elasticity, temperature resistance, is used in cable accessories for HVDC cables. The space charge, formed under dc stress in SiR, would distort the local electric field, and furtherly influence the characteristics of partial discharge and accelerate the insulation aging. Direct fluorination, as a solution to change the chemical component, could alter the electrical properties of the polymer surface layer. This paper focuses on the effect of the fluorination on the space charge accumulation in HTV SiR. In this investigation, the samples were fluorinated at 25 ° using a F2/N2 mixture gas with 20 % F2 by volume at 0.05 MPa for 10, 20, 30 and 40 minutes. The space charge behavior of the fluorinated samples was observed by PEA method and the trap level distribution was obtained by modified isothermal discharge current (MIDC) test. The results indicated that the fluorination for 20 minutes effectively suppressed the space charge injection in SiR. However, excessive fluorination (over 30 minutes) brought in abundant deep traps, and led to significant amount of space charge accumulation in the bulk of polymer. As a consequence, the appropriate fluorination has significant effect on the space charge accumulation in HTV SiR and has a potential application for inner insulation in premolded accessories of HVDC cable. [ABSTRACT FROM AUTHOR]

This review aims to summarise the progress in some materials and structures for electromagnetic applications, such as microwave absorption, electric shielding and antenna designs, which have been developed in recent years. Composites with spherical powders for microwave absorption focus mainly on those based on ferrites (especially hexagonal), carbonyl iron and related alloys and various newly emerged nanosized materials. Composites with long conductive fibres as fillers will be summarised, with speical attentions to prediction, measurment and evaluation of their performances. Metamaterials include structures for microwave absorbing applications, tunable materials or structures with reflection or transmission coefficients that are tunable by external magnetic or electric fields, and specially designed structures for microwave absorbing applications, with thickness much smaller than that of conventional composite materials and performances that can be optimised by the physical properties of substrates, and new metamaterials constructed with ferrite cores wound by metallic wire coils that exhibited unique magnetic properties, with extremely high real and imaginary permeability, which are adjustable or tunable by varying their configurations. Magnetodielectric materials, with matching permeability and permittivity, together with sufficiently low magnetic and dielectric loss tangents, with potential applications in antenna miniaturisation, will be discussed. [ABSTRACT FROM AUTHOR]

Electromagnetic scattering by conducting body of revolution (BOR) is formulated in terms of the electric field integral equation combined with high-order basis function based on curved-wire segment. Owing to the rotational symmetry property of BOR, the currents are represented using high-order basis functions along the generating arc and Fourier series expansion for the periodic azimuthal variation. The method of moment for BOR (BORMoM) is applied to the linear system solved by the direct solver. The parallelisation is carried out in the high-order BORMoM to further reduce the computation time. Numerical results are presented to demonstrate the accuracy and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

Calcium copper titanate (CaCuTiO, CCTO) powder was mixed with boric oxide (BO) glassy phase up to 8% by weight to prepare the composite ceramics. The effects of BO incorporation on the microstructures, electric and dielectric properties of CCTO ceramics have been systematically investigated. Adding BO results in both the decrease of the CCTO grain size. These microstructural changes conjointly affect the dielectric constant. In addition, further BO increase leads to its aggregation at grain boundaries. Meanwhile, the BO addition reduces the nonlinear coefficient and influences the breakdown electric field. [ABSTRACT FROM AUTHOR]

The nature of the magnetism brought about by Fe adatoms on the surface of the topological insulator Bi2Se3 was examined in terms of density functional calculations. The Fe adatoms exhibit strong easy-axis magnetic anisotropy in the dilute adsorption limit due to the topological surface states (TSS). The spin-exchange J between the Fe adatoms follows a Ruderman-Kittel-Kasuya-Yosida behavior with substantial anisotropy, and the Dzyaloshinskii-Moriya interaction between them is quite strong with ∣D/J∣ ≈ 0.3 under the mediation by the TSS and can be further raised to ∼0.6 by an external electric field. The apparent single-ion anisotropy of a Fe adatom is indispensable in determining the spin orientation [ABSTRACT FROM AUTHOR]

Based on the dispersion characteristic of magnetised plasma, an improved shift-operator finite difference time-domain (SO-FDTD) method for anisotropic medium is proposed. The constitutive relations between the polarised current density J and the electric field intensity E in the frequency-domain are written as a rational polynomial function, and the constitutive relations are deduced in the time-domain. Through a shift operator, the constitutive relations in the time-domain are transformed to the discrete time-domain. Thus, the recursion difference equations are obtained for each field component. Compared to the analytical method, current-density (JE) convolution finite difference time-domain method and the original SO-FDTD method, the high accuracy and efficiency of this method are verified by calculating the reflection and transmission coefficient of electromagnetic waves through a magnetised plasma slab. [ABSTRACT FROM AUTHOR]

The bird-streamer caused failures have become one of the major causes of transmission line outages. It is more common and widespread than generally believed, and greatly threatens the reliability of transmission lines. The laboratory study of such failures mechanism is seldom reported especially for long gaps such as 500 kV insulators. Presented in this paper are the results of long air gaps bird streamer flashover experiments conducted on 500 kV and 220 kV transmission line insulators. The experimental results demonstrated that bird-streamer caused surface flashover can happen in 500 kV insulators, however space flashover, because the bird streamer will split into different jets under high electric field cannot short circuit the long air gaps. The high risk areas of flashover for 220 kV and 500 kV insulators were defined in this paper: an elliptical area for 220 kV 1 string insulator and a symmetrical area beside the central line for 500 kV V string insulator. The influence of some main factors on flashover processes is also elucidated, such as volume, conductivity and viscosity of the streamer, and the insulator type and configuration. The paper has significant value in understanding the bird caused failure mechanisms and designing remedies. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study is the evaluation of radiation effects in detectors based on p-type magnetic czochralski (MCz) Si that was converted to n-type by thermal donor (TD) introduction. As-processed p+-p-n+ detectors were annealed at 430°C resulting in p+-n(TD)-n+ structures. The space charge sign and the electric field distribution E(x) in MCz Si p+-n(TD)-n+ detectors irradiated by 24GeV/c protons were analyzed using the data on the current pulse response and the Double Peak (DP) electric field distribution model for heavily irradiated detectors. The approach considers an irradiated detector as a structure with three regions in which the electric field depends on the coordinate, and the induced current pulse response arises from the drift process of free carriers in the detector with variable electric field. Reconstruction of the E(x) profile from the pulse response shapes is performed employing a new method for DP electric field reconstruction. This method includes: (a) a direct extraction of charge loss due to trapping and (b) the fitting of a simulated pulse response to the “corrected” pulse by adjusting the electric field profiles in the three regions. Reconstruction of E(x) distribution showed that in the diodes irradiated by a proton fluence of (2–4)×1014 p/cm2 space charge sign inversion has occurred. This is the evidence that the influence of 24GeV/c proton radiation on MCz Si p+-n(TD)-n+ detectors is similar to that on p+-n-n+ detectors based on FZ or diffusion oxygenated n-type Si. [Copyright &y& Elsevier]

We analyze negative refraction in two-dimensional photonic crystals that are made from electro-optical active materials. Application of an electric field to the photonic crystal changes the dielectric constant of the material and consequently modifies the photonic band and dispersion properties. We have investigated focusing properties of the photonic crystal slab lens at different frequencies within the first two bands and under various magnitudes of electric field. The simulation results reveal that one can dynamically tune negative refraction by means of index-tunable photonic crystals. [ABSTRACT FROM AUTHOR]

An application of a polarized electric field to reduce adhesion of a biological sludge to the dryer wall was studied experimentally by contact drying of a sludge cake deposited on a heated metal plate serving as the cathode. It was found that the adhesion intensity is greatly reduced due to a water layer formed at the heated plate, when a fraction of water in the sludge migrates to the cathode by electro-osmosis, as well as by gas bubbles, which are generated by the electrochemical reaction. The voltage gradient from 4 to 5 V/cm was found optimal for drying 10-mm-thick sludge samples. Under these conditions, the electric energy consumption amounted to 3.87 kWh/t. An increase in cathode temperature reduced the sludge-adhering intensity and shortened drying time. The beneficial effect of an electric field on reducing sludge adherence decreases with increasing wall temperature. [ABSTRACT FROM AUTHOR]

Abstract: Positive space charge build-up was observed in proton—and neutron—irradiated high-resistivity magnetic Czochralski (MCZ) n-type Si detectors after gamma radiation. Space charge sign re-inversion (SCSRI) from negative to positive was achieved at the high dose of 454Mrad in a low-fluence proton irradiated MCZ Si detector. No SCSRI has been observed yet for low-fluence neutron-irradiated MCZ Si detectors at the highest dose in this study (662Mrad), but positive space charge is building up, and SCSRI is expected at higher doses. Up to the highest dose in this study, the double junction or double peak electric field distribution is still preserved even after SCSRI. No SCSRI was observed in control FZ Si detectors. Space charge sign inversion was also observed in high-resistivity as-processed MCZ p-type Si detectors after gamma radiation. [Copyright &y& Elsevier]

We investigate the persistent current in a polyacetylene ring induced by axially symmetric, gauge potentials of both magnetic flux and static electric field using a modified SSH Hamiltonian for the polyacetylene chain. The AB and AC effects for an electron with spin are formulated simultaneously in a completely equal footing. It is shown that the gauge fields result in a Fröhlich-type superconductivity equivalent to the effect of a travelling lattice wave. The total energy as well as the persistent current density are shown to be periodic function of the total effective flux of the both gauge fields of AB and AC embraced by the polyacetylene ring. [ABSTRACT FROM AUTHOR]

Abstract: Non-uniform distribution of the electric field outlined as double peak distortion (DPD) is considered for heavily irradiated silicon strip detectors, which were developed for the CERN-ATLAS semiconductor tracker. DPD originates from the non-uniform accumulation of electrons and holes from the bulk generated current that are captured by radiation induced defects: deep acceptors and donors with mid-gap energy levels. This corresponds to the formation of the low electric field region in the detector central part that consequently will delay charge collection. The electric field distributions at different reverse biases, fluences and detector operational temperatures are calculated using a one-dimensional Poisson equation as it was done earlier for pad detectors. It has been shown that due to the electric field focusing at the strips the DPD effect is more pronounced for strip detectors as compared to that in pad detectors. The double peak electric field distribution is evinced experimentally in current pulse response shape when the charge is collected along the strip axis. [Copyright &y& Elsevier]

A novel high performance carrier stored trench bipolar transistor (CSTBT) with a p-type buried layer (PBL-CSTBT) is proposed. The p-type layer of the structure is formed by ion implantation at the bottom of the trench after a partial etching of the Pbase/Ncs layer and the fabrication process is fully compatible with the conventional CSTBT (C-CSTBT) structure. In comparison with the C-CSTBT without a buried layer, the novel structure offers not only high breakdown voltage, but also improved Eoff-Vce(on) trade-off characteristics. [ABSTRACT FROM AUTHOR]

Based on theoretical and experimental investigation of a compound buried layer SOI with a single window in the upper buried oxide layer (SWCBL SOI), further research on the compound buried layer SOI with double windows (DWCBL SOI) is proposed. Higher concentration interface holes under the drain more effectively enhance the electric field of the lower buried oxide layer, resulting in a higher breakdown voltage (BV) of the device. With the same thicknesses of 20 µm top silicon layer and 3 µm buried oxide layer, the BV of the DWCBL increases to 1040 from 798 V of the SWCBL and 622 V of the conventional SOI, maintaining the low self-heating effect. [ABSTRACT FROM AUTHOR]

A new buffered super junction (SJ) LDMOS on silicon-on-insulator (SOI) is proposed to eliminate the substrate-assisted depletion effect. The trenched buried oxide is self-adaptive to collect the additional charges according to the variable electric field strength, which forms a dynamic buffer between the SJ and the substrate. The collected charges compensate the N pillars, resulting in the charge balance between N and P pillars of the SJ. Numerical simulation results indicate that the proposed device features high breakdown voltage and low on-resistance. [ABSTRACT FROM AUTHOR]

We demonstrate the tunability of the two-photon absorption (TPA) coefficient by adjusting the electric field in a HgCdTe (MCT) photodiode with cutoff wavelength of 5.2 μm. The TPA coefficient was measured by using a picosecond pulsed laser with wavelength of 7.92 μm. An enhancement of the TPA coefficient occurs in the space charge region of the MCT pn junction, which can be attributed to the Franz–Keldysh effect induced by the built-in electric field. By applying a reverse bias to intensify the built-in field, the TPA coefficient is found to be further enhanced by a factor of 18.9. This electric field dependence of the TPA coefficient has been fairly interpreted by the pn junction model with the Franz–Keldysh effect included. [ABSTRACT FROM AUTHOR]

A new SOI high-voltage device with a step thickness sustained voltage layer (ST SOI) is proposed. The electric field in the drift region is modulated, and that in the buried layer is enhanced by the variable-thickness SOI layer, resulting in enhancement of breakdown voltage (BV). BV for the ST SOI with two steps is twice as high as that of the conventional SOI, maintaining the low on-resistance (Ron). [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the result of an investigation into electromigration-driven morphological evolution of inclusions in finite scale thin-film interconnects using phase field method. The results show that morphological evolution and migration of an inclusion are proportional to the electric field strength applied on thin-film interconnects, and that inclusions with anisotropic diffusion interface move slower than those with isotropic interface under the identical electric field, and show irregular patterns when the inclusion is subjected to perturbation. [Copyright &y& Elsevier]

This study focuses on the properties of the B i O i (interstitial Boron–interstitial Oxygen) and C i O i (interstitial Carbon–interstitial Oxygen) defect complexes by 5.5 MeV electrons in low resistivity silicon. Two different types of diodes manufactured on p-type epitaxial and Czochralski silicon with a resistivity of about 10 Ω ⋅ cm were irradiated with fluence values between 1 × 1015 cm-2 and 6 × 1015 cm-2. Such diodes cannot be fully depleted and thus the accurate evaluation of defect concentrations and properties (activation energy, capture cross-section, concentration) from Thermally Stimulated Currents (TSC) experiments alone is not possible. In this study we demonstrate that by performing Thermally Stimulated Capacitance (TS-Cap) experiments in similar conditions to TSC measurements and developing theoretical models for simulating both types of B i O i signals generated in TSC and TS-Cap measurements, accurate evaluations can be performed. The changes of the position-dependent electric field, the effective space charge density N eff profile as well as the occupation of the B i O i defect during the electric field dependent electron emission, are simulated as a function of temperature. The macroscopic properties (leakage current and N eff) extracted from current–voltage and capacitance–voltage measurements at 20 °C are also presented and discussed. [ABSTRACT FROM AUTHOR]

Abstract: The reverse current of irradiated Si detectors was analyzed in terms of carrier generation via defects with the energy levels in the Si bandgap. The data for detectors irradiated by 23GeV protons and 1MeV neutrons were obtained in the temperature (T) range of 200–300K. Two models of the bulk generation current were developed to allow fitting and simulation of the reverse current vs. T data. These are a model of carrier generation via a single effective energy level for the direct estimation of detector performance, and a model of two generation centers with the effective energy levels originating from radiation-induced deep levels adjacent to the midgap. The influence of the bandgap temperature dependence (E g (T)) on the parameters of the current generation centers was estimated. The first model gives the effective level energy of E v +0.65eV and a linear dependence of the effective defect concentration on fluence. The second model involves contribution from deep donors and deep acceptors positioned at E v +0.48eV and E c −0.52eV, respectively, and is adapted for simultaneous calculation of the reverse current and the electric field distribution in irradiated detectors. The results of the study show that: (a) both models fit well to the experimental data; (b) contribution of the E g (T) dependence to E t does not exceed 5%; (c) taking into consideration the bulk generation current gives the correct electric field distribution, which is a key reference for other characteristics of irradiated Si detectors; and (d) the generation lifetime is significantly larger than the carrier trapping time constant pointing to additional levels taking part in trapping of the drifting charge. [Copyright &y& Elsevier]

Abstract: The model explaining an enhanced collected charge in detectors irradiated to 1015–1016 neq/cm2 is developed. This effect was first revealed in heavily irradiated n-on-p detectors operated at high bias voltage ranging from 900 to 1700V. The model is based on the fundamental effect of carrier avalanche multiplication in the space charge region and in our case is extended with a consideration of p–n junctions with a high concentration of the deep levels. It is shown that the efficient trapping of free carriers from the bulk generation current to the deep levels of radiation induced defects leads to the stabilization of the irradiated detector operation in avalanche multiplication mode due to the reduction of the electric field at the junction. The charge collection efficiency and the detector reverse current dependences on the applied bias have been numerically simulated in this study and they well correlate to the recent experimental results of CERN RD50 collaboration. The developed model of enhanced collected charge predicts a controllable operation of heavily irradiated detectors that is promising for the detector application in the upcoming experiments in a high luminosity collider. [Copyright &y& Elsevier]

Abstract: A heavily irradiated (3×1015 1MeVneq/cm2) Current Injected Detector (CID) was tested with 225GeV muon beam at CERN H2 beam line. In the CID concept the current is limited by the space charge. The injected carriers will be trapped by the deep levels and this induces a stable electric field through the entire bulk regardless of the irradiation fluence the detector has been exposed to. The steady-state density of the trapped charge is defined by the balance between the trapping and the emission rates of charge carriers (detrapping). Thus, the amount of charge injection needed for the electric field stabilization depends on the temperature. AC-coupled 16cm2 detector was processed on high resistivity n-type magnetic Czochralski silicon, and it had 768 strips, 50μm pitch, 10μm strip width and 3.9cm strip length. The beam test was carried out using a silicon beam telescope that is based on the CMS detector readout prototype components, APV25 readout chips, and eight strip sensors made by Hamamatsu having 60μm pitch and intermediate strips. The tested CID detector was bonded to the APV25 readout, and it was operated at temperatures ranging from −40 to −53°C. The CID detector irradiated at 3×1015 1MeVneq/cm2 fluence shows about 40% relative Charge Collection Efficiency with respect to the non-irradiated reference plane sensors. [Copyright &y& Elsevier]

Abstract: Experimental results and simulations of Charge Collection Efficiency (CCE) of Current Injected Detectors (CIDs) are focused. CID is a concept where the current is limited by the space charge. The injected carriers will be trapped by the deep levels. This induces a stable electric field through the entire bulk regardless of the irradiation fluence the detector has been exposed. Our results show that the CCE of CIDs is about two times higher than of regular detectors when irradiated up to 1×1016 cm−2. The higher CCE is achieved already at −50°C temperatures. [Copyright &y& Elsevier]