Electric Field Modulation Research Articles

Enhanced luminescence, electric-field and actinic-light modulation of emission in nematic-CdSeS gradient nanocrystal composites by polymer confinement

We demonstrate that dispersing a small amount of CdSeS gradient quantum dots (QDs) in a nematic liquid crystal and geometrically confining the nanocomposite in a polymer network leads to their ordered linear assembly, as observed through electron microscopy. Such an orientational order not only enhances the base photoluminescence (PL), but brings in significant anisotropy in the emission magnitude, a feature barely seen for the system without the polymer network. A high frequency (∼kHz) AC field adds the attractive dimension of on-demand and spatially addressable PL modulation. Using a photoisomerizable azobenzene derivative and a carefully selected excitation wavelength, it is shown that an actinic-light driven modulation of PL is also possible, which is furtherenhanced by the presence of the polymer network.

Magnetoelastic coupling enabled tunability of magnon spin current generation in two-dimensional antiferromagnets

We theoretically investigate the magnetoelastic coupling (MEC) and its effect on magnon transport in two-dimensional antiferromagnets with a honeycomb lattice. MEC coeffcient along with magnetic exchange parameters and spring constants are computed for monolayers of transition metal trichalcogenides with N\'eel order ($\text{MnPS}_3$ and $\text{VPS}_3$) and zigzag order ($\text{CrSiTe}_3$, $\text{NiPS}_3$ and $\text{NiPSe}_3$) by $ab$ $initio$ calculations. Using these parameters, we predict that the spin-Nernst coefficient is significantly enhanced due to magnetoelastic coupling. Our study shows that although Dzyaloshinskii-Moriya interaction can produce spin Nernst effect in these materials, other mechanisms such as magnon-phonon coupling should be taken into account. We also demonstrate that the magnetic anisotropy is an important factor for control of magnon-phonon hybridization and enhancement of the Berry curvature and thus the spin-Nernst coefficient. Our results pave the way towards gate tunable spin current generation in 2D magnets by SNE via electric field modulation of MEC and anisotropy.

The magnetic proximity effect at the MoS2/CrI3 interface

The vicinity to a two-dimensional magnetic material provides a simple and effective way to break the valley degeneracy of transition-metal dichalcogenides because of the magnetic proximity effect. Based on first-principles calculations, we study the band structure of a MoS2/CrI3 van der Waals heterostructure and its manipulation by vertical electric fields. A huge valley splitting of about 19.60 meV, equivalent to an external magnetic fields of about 89.0 T can be generated by an electric field of 0.115 V Å−1. The electric field causes discontinuous changes in the valley splitting. The electric field drives the bands of MoS2 across those of CrI3. At the critical electric fields, the interlayer orbital hybridization leads to the energy level repulsion and an abrupt exchange of the band index. We also study the effect of interlayer distance on the valley splitting and observe a more significant electric field modulation. This work deepens our understanding on the interfacial magnetic proximity effect as a result of the orbital hybridization across the van der Waals gap.

Highly Sensitive Strain Sensor from Topological‐Structure Modulated Dielectric Elastic Nanocomposites

AbstractFlexible strain sensors are critical to several potential intelligent applications, such as human–machine interfaces, soft robotics, human motion detection, and safety monitoring of components. Stretchable functional materials are important components of strain sensors, and they are still a major challenge for high‐performance strain sensors. Herein, a novel strategy of designing and optimizing a flexible strain sensor by developing topological structure modulated high dielectric elastic nanocomposite is demonstrated. The topological structure produces synergistic effects of space charge enhancement and local electric field modulation, and it gives rise to an ultrahigh dielectric permittivity (113.4, at 1 kHz) and excellent comprehensive electromechanical performance for the dielectric elastic nanocomposite. An interdigital capacitive strain sensor is prepared based on the topological structured elastic dielectric nanocomposite, and it possesses positive capacitance response with strain, which breaks through disadvantages of negative sensitivity and narrow linear range for conventional interdigital strain sensors. The strain sensor achieves high signal‐to‐noise ratio, high positive capacitance response sensitivity of 5.7 pF %–1, and wide linear range (strain from 0.1% to 100%). The high permittivity elastic nanocomposite is capable to fabricate integrated microsensor array, making conditions for detecting local strain of convoluted surfaces and motion states of flexible actuators.

Novel Vertical Power MOSFET With Step Hk Insulator Close to Super Junction Limit Relationship Between Breakdown Voltage and Specific ON-Resistance by Improving Electric Field Modulation

A new vertical double-diffused metal oxide semiconductor field effect transistor (MOSFET) is presented based on the high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> (Hk) MOSFET concept in this article with the step high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> insulator, named as step Hk vertical double-diffused metal oxide semiconductor (VDMOS), to improve the electric field modulation effect. For step Hk VDMOS, the depletion is increased by the electric field modulation effect of step Hk insulator, which decreases the specific on-resistance of step Hk VDMOS compared to the conventional Hk VDMOS. The various thickness of the Hk insulator modulates the vertical electric field distribution in the drift region, which increases the breakdown voltage (BV) of the step Hk VDMOS. Meanwhile, an analytical model for novel step Hk VDMOS is obtained by solving the 2-D Poisson equation in an N-type drift region, and the 2-D Laplace equation in the step Hk region, which can reasonably explain the modulation effect of the step Hk region on the electric field distribution. The results show that the BV of the step Hk VDMOS is increased from 639 V of the conventional Hk VDMOS to 736 V with the same drift length of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$42~\mu \text{m}$ </tex-math></inline-formula> . The theoretical results of the electrical characteristics are in good agreement with the results from numerical simulations.

A novel technique for accurate electrode placement over cortical targets for transcranial electrical stimulation (tES) clinical trials

Objective. We present an easy-to-implement technique for accurate electrode placement over repeated transcranial electrical stimulation (tES) sessions across participants and time. tES is an emerging, non-invasive neuromodulation technique that delivers electrical stimulation using scalp electrodes. Approach. The tES electrode placement technique was developed during an exploratory clinical trial aimed at targeting a specific MNI-atlas cortical coordinate in N = 59 depressed participants (32 F, mean age: 31.1 ± 8.3 SD). Each participant completed 12 sessions of active or sham stimulation, administered using high-definition (HD) or conventional sized electrode montages placed according to the proposed technique. Neuronavigation data measuring the distances between the identified and the intended stimulation site, simulations, and cerebral blood flow (CBF) data at baseline and post-treatment were acquired to evaluate the targeting characteristics of the proposed technique. Main results. Neuronavigation measurements indicate accurate electrode placement to within 1 cm of the stimulation target on average across repeated sessions. Simulations predict that these placement characteristics result in minimal electric field differences at the stimulation target (>0.90 correlation, and <10% change in the modal electric field and targeted volume). Additionally, significant changes in %CBF (relative to baseline) under the stimulation target in the active stimulation group relative to sham confirmed that the proposed placement technique introduces minimal bias in the spatial location of the cortical coordinate ultimately targeted. Finally, we show proof of concept that the proposed technique provides similar accuracy of electrode placement at other cortical targets. Significance. For voxel-level cortical targets, existing techniques based on cranial landmarks are suboptimal. Our results show that the proposed electrode placement approach provides high consistency for the accurate targeting of such specific cortical regions. Overall, the proposed technique now enables the accurate targeting of locations not accessible with the existing 10–20 system such as scalp-projections of clinically-relevant cortical coordinates identified by brain mapping studies. Clinical trial ID: NCT03556124.

Correlated electric field modulation of electron transfer parameters and the access to alternative conformations of multifunctional cytochrome c

Cytochrome c (Cytc) is a multifunctional protein that, in its native conformation, shuttles electrons in the mitochondrial respiratory chain. Conformational transitions that involve replacement of the heme distal ligand lead to the gain of alternative peroxidase activity, which is crucial for membrane permeabilization during apoptosis. Using a time-resolved SERR spectroelectrochemical approach, we found that the key physicochemical parameters that characterize the electron transfer (ET) canonic function and those that determine the transition to alternative conformations are strongly correlated and are modulated by local electric fields (LEF) of biologically meaningful magnitude. The electron shuttling function is optimized at moderate LEFs of around 1 V nm−1. A decrease of the LEF is detrimental for ET as it rises the reorganization energy. Moreover, LEF values below and above the optimal for ET favor alternative conformations with peroxidase activity and downshifted reduction potentials. The underlying proposed mechanism is the LEF modulation of the flexibility of crucial protein segments, which produces a differential effect on the kinetic ET and conformational parameters of Cytc. These findings might be related to variations in the mitochondrial membrane potential during apoptosis, as the basis for the switch between canonic and alternative functions of Cytc. Moreover, they highlight the possible role of variable LEFs in determining the function of other moonlighting proteins through modulation of the protein dynamics.

Lattice-Matched AlInN/GaN/AlGaN/GaN Heterostructured-Double-Channel Metal-Oxide-Semiconductor High-Electron Mobility Transistors with Multiple-Mesa-Fin-Channel Array.

Multiple-mesa-fin-channel array patterned by a laser interference photolithography system and gallium oxide (Ga2O3) gate oxide layer deposited by a vapor cooling condensation system were employed in double-channel Al0.83In0.17N/GaN/Al0.18Ga0.82N/GaN heterostructured-metal-oxide-semiconductors (MOSHEMTs). The double-channel was constructed by the polarized Al0.18Ga0.82N/GaN channel 1 and band discontinued lattice-matched Al0.83In0.17N/GaN channel 2. Because of the superior gate control capability, the generally induced double-hump transconductance characteristics of double-channel MOSHEMTs were not obtained in the devices. The superior gate control capability was contributed by the side-wall electrical field modulation in the fin-channel. Owing to the high-insulating Ga2O3 gate oxide layer and the high-quality interface between the Ga2O3 and GaN layers, low noise power density of 8.7 × 10−14 Hz−1 and low Hooge’s coefficient of 6.25 × 10−6 of flicker noise were obtained. Furthermore, the devices had a unit gain cutoff frequency of 6.5 GHz and a maximal oscillation frequency of 12.6 GHz.

Study of TID Radiation Effects on the Breakdown Voltage of Buried P-Pillar SOI LDMOSFETs

This paper presents experimental and numerical analysis of a buried P-pillar (BP) lateral double-diffused metal-oxide semiconductor (LDMOS) fabricated on a silicon-on-insulator (SOI) substrate. The experimental results indicate that the specific on-resistance ( R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> on,sp</sub> ) of the SOI BP-LDMOS is 9.5 mΩ· cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with a breakdown voltage (BV) of 229 V, which corresponds to a figure of merit (FOM) of 5.52 MW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The analysis of structural parameter optimization of the SOI BP-LDMOS under different doping concentrations in the drift region and P-pillar layer is conducted via numerical simulation. The results show that the tested sample can achieve about 80% of the maximal FOM. Finally, the experimental and numerical investigation of the total ionizing dose (TID) radiation effect on the BV shift is performed. The TID tolerance of the measured SOI BP-LDMOS can reach 300 krad(Si) to support a voltage of 200 V. Due to the electric field modulation hardening design, compared with the conventional hardened SOI LDMOS, the studied hardened BP-LDMOS can achieve a significant improvement in the TID tolerance from 225 krad(Si) to 525 krad(Si).

Highly Sensitive DNA Detection Beyond the Debye Screening Length Using CMOS Field Effect Transistors

Field effect transistors are considered one of the key technologies to provide real-time and label-free biodetection. Direct detection in physiological solutions is, however, severely limited by the Debye charge-screening effect of the electrical double layer. Most measurements are therefore performed indirectly in diluted ionic-strength solutions. This study proposes a general technique based on modulation of the surface electric field of the CMOS (complementary metal oxide semiconductor) extended-gate field effect transistors (EGFETs) to investigate the screening effect on hybridized DNA (deoxyribonucleic acid) signals from 1 MHz to 15 MHz. The 32 EGFET sensor array exhibited a floating-gate potential change of 17.4 mV/log[DNA] from 1 fM to 100 pM with a near picomolar-level resolution and a response time below 8 minutes.

Controlling electronic and optical properties of zigzag graphene nanoribbons by a modulated electric field: significance of σ bands

We investigate the peculiar electronic and optical properties of zigzag graphene nanoribbons (GNRs) under the effects of uniform and modulated electric fields. The hybridization between the four atomic orbitals ( s , p x , p y , p z ) is considered by means of the tight-binding model calculations. Both the π bands originating from the p z orbital and σ bands arising from the ( s , p x , p y ) orbitals play critical roles in the electronic structure and thus the absorption spectra. They determine the Fermi level and the available excitation channels between the occupied and unoccupied states. We show that an in-plane electric field in the form of modulated potential can significantly modify the electronic and optical properties of zigzag GNRs. The field-induced modification in energy dispersion, band-edge states, and band gap gives rise to rich absorption spectra with diverse structures. Our theoretical prediction could be verified by angle-resolved photoemission spectroscopies and optical spectroscopies.

Design of planar waveguide directional couplers with arbitrary modal electric field

The purpose of this work is to present a method for designing planar waveguide couplers of arbitrary modal electric field distributions. The idea here is to create couplers with unusual electric fields, which confine in one planar waveguide. This is possible if a planar waveguide profile supporting two pre-selected mode fields is designed. Their interference will have to transfer the optical power from one region (bottom layer) to another region (top layer) completely. The inverse transmission-line technique and the desired electric field are applied, based on which the refractive index profile of the couplers exhibiting excellent crosstalk is reconstructed. By choosing this technique, it is feasible to design planar components in sensing applications, such as high power, temperature or pressure sensors and numerous other possibilities, using unusual electric field distributions.

Fouling Mitigation by Optimizing Flow Rate and Pulsed Electric Field during Bipolar Membrane Electroacidification of Caseinate Solution

The efficiency of separation processes using ion exchange membranes (IEMs), especially in the food industry, is significantly limited by the fouling phenomenon, which is the process of the attachment and growth of certain species on the surface and inside the membrane. Pulsed electric field (PEF) mode, which consists in the application of constant current density pulses during a fixed time (Ton) alternated with pause lapses (Toff), has a positive antifouling impact. The aim of this study was to investigate the combined effect of three different relatively high flow rates of feed solution (corresponding to Reynolds numbers of 187, 374 and 560) and various pulse–pause ratios of PEF current regime on protein fouling kinetics during electrodialysis with bipolar membranes (EDBM) of a model caseinate solution. Four different pulse/pause regimes (with Ton/Toff ratios equal to 10 s/10 s, 10 s/20 s, 10 s/33 s and 10 s/50 s) during electrodialysis (ED) treatment were evaluated at a current density of 5 mA/cm2. It was found that increasing the pause duration and caseinate solution flow rate had a positive impact on the minimization of protein fouling occurring on the cationic surface of the bipolar membrane (BPM) during the EDBM. Both a long pause and high flow rate contribute to a more effective decrease in the concentration of protons and caseinate anions at the BPM surface: a very good membrane performance was achieved with 50 s of pause duration of PEF and a flow rate corresponding to Re = 374. A further increase in PEF pause duration (above 50 s) or flow rate (above Re = 374) did not lead to a significant decrease in the amount of fouling.

Study of Electric Field Impact on Crystallization in Tunnel Drainage Pipes in Hard Water Area

To solve the problem of blockage of crystallization in tunnel drainage pipes in hard water area, electric field devices are designed and applied in the transversal tunnel drainage pipe according to the fundamental law of crystallization. Laboratory tests were carried out to test the crystallizing tunnel drainage pipe under the effect of electric field in order to study the law of electric field impact on crystallization in tunnel drainage pipes in hard water area. The test results indicate that the arranged circumferential and parallel plate electric field devices can form an electrical field within a narrow and small space inside the pipe and influence the ion movement in water and adsorption performance between crystals and the pipe. Under the condition of full flow, the amount of crystals in the ordinary pipe without electric field treatment increases progressively along water flow direction and remains relatively uniform later. The amount of crystals along the water flow direction of the pipe treated with circumferential and parallel plate electric fields presents signs of fluctuation in the early stage and then stableness later. The amount of crystals in the fluctuating section is higher and lower in the uniform section, and its uniform section length is longer than that in ordinary pipes. Under the condition of full current, crystallizing speed declines with elapse of running time. After the electric field is imposed, crystallizing acceleration progressively decreased to a relatively lower level. Comparing three voltages of 5 V, 12 V, and 24 V, the effect of scale inhibition under 5 V is superior. When water amount in the pipe varies, the effects of scale inhibition under different electric field modes are different. The electric field effect causes the changes of the external form of calcium carbonate crystal and its surface abrasion, porous crystal, and structural looseness.

Electrical transport modulation of VO2/Si(111) heterojunction by engineering interfacial barrier height

Smart multifunctional materials such as vanadium dioxide (VO2), which exhibit a reversible semiconductor-to-metal transition (SMT), provide a new route toward engineering high speed switchable devices. Here, we present a detailed report on the modulation in the electrical properties of VO2/Si heterostructures by application of an external electrical field across VO2 thin films. Single-phase VO2 thin films have been deposited on an Si(111) substrate using the pulsed laser deposition technique. The electrical transport behavior across the VO2/Si heterostructure has been studied in the temperature range of 35–105 °C, and a reversible SMT can be seen at 68 and 63 °C for heating and cooling cycles, respectively. The temperature-dependent resistance of the device shows a hysteresis loop around the transition temperature of the VO2 thin film. In addition, the device shows a significant change in junction current when an external bias is applied on the VO2 thin film, and this phenomenon has been utilized to study the switching behavior of the device. Such behavior is due to the change in interfacial barrier height because of the bias dependent tilting of electronic energy bands of the VO2 thin film. Our results offer novel opportunities to externally control the electrical transport of vertical heterostructures and can be beneficial for extending the notion of electrical field modulation in electrical switches and sensors.

Properties of the 90° cylindrical energy analyzer with internal deceleration of the beam in real conditions of operation

To measure plasma potential in toroidal magnetically confined fusion plasma, the Heavy Ion Beam Diagnostic (HIBD) employs of the electrostatic energy analyzer. The 90° cylindrical energy analyzer (CEA) developed for the HIBD on the ISTTOK tokamak due to compactness and multislit operation capability, is characterized by large angular aberrations, if operated in conventional mode. A new operation regime was proposed based on numerical investigations, which demonstrated the efficiency of the 90°CEA operation in reducing angular aberrations via the deceleration of the ion beam inside analyzer, resulting also on an improved energy resolution. In this paper, the properties of the 90 ° CEA featuring with guard rings (GR) to shield the analyzer from the surrounding structures are investigated in the internal deceleration mode (ID-mode) for “centric” and “paracentric” injection geometries. The numerical simulations are conducted using SIMION code. Special attention is paid to uniformity of the beam image on detector plate, which is of importance in ion beam energy measurements by split-plate detector technique. The results confirm coupling of analyzer angle aberration properties with beam deceleration inside analyzer. For both “centric” and “paracentric” entrances the existence of the first-order focus in ID-mode is obtained. However, the first order focus ID-mode of 90°CEA with GR is characterized by heterogeneity of the image for the initially uniform beam, determined by modification of electric field inside analyzer. It is revealed that the energy dispersion of the initially monoenergetic ions due to chromatic-like aberration introduced by analyzer plays a contributive role in the beam image non-uniformity. From the beam energy measurements point of view, it is shown that the energy variation due to this chromatic aberration is of the second order of the analyzer intrinsic resolution. The results show that “centric” entrance in ID-mode is preferable as the image non-uniformity is less pronounced and can be effectively restored by manipulation of entrance slit dimensions and potentials on GR. It is concluded that besides detail preparatory numerical optimization, the beam image shape and uniformity control is essential, which can be realized with the dedicated multiple cell detection.

Understanding the correlation between intermediate monoclinic phase (Cc) and piezoelectric properties in NaNbO3-BaTiO3-CaZrO3 ternary system with octahedral tilt

Compared with traditional tetragonal (T) P4mm - rhombohedral (R) R3m morphotropic phase boundary (MPB) system, the structure-property relationship of MPB systems with octahedral tilt is still unclear. In this work, the phase structure evolution under composition and electric field modulations in lead-free (0.9-x)NaNbO3-0.1BaTiO3-xCaZrO3 (NN-BT-xCZ) close to the untilt P4mm-tilt R3c MPB was investigated in details by means of the ex- and in-situ x-ray diffraction and various electrical property measurements. Both P4 mm and R3c phases can irreversibly transform into a Cc phase under electric field loading, which should be considered as a result of the cooperative coupling between ferroelectric and antiferrodistortive instabilities. Quantitative analysis indicates that little composition dependent lattice strain and domain switching of P4 mm phase can be observed, and the variation of piezoelectric coefficient is closely related to Cc phase, which exhibits an enhancement of both lattice strain and domain switching within MPB. This suggests that lattice strain and domain switching of Cc phase are coupled. On the contrary, both of them are competed in P4 mm phase because the P4 mm phase is dominated by irreversible domain switching. The experimental results would benefit for deeply understanding the origin of piezoelectric response for many octahedral-tilt MPB piezoelectric systems.

Vortex beam generator working in terahertz region based on transmissive metasurfaces

Owing to the eigenstates of orbital angular momentum (OAM) are infinite and orthogonal to each other, OAM can improve communication capacity infinitely. In this paper, we propose a terahertz vortex beam generator on transmissive metasurfaces. When the y-polarized terahertz wave illuminates vertically to the metasurface along the -z direction, the proposed metasurface generates terahertz vortex beams with topological charges l = ±1, l = ±2 and l = ±3 at the frequency ranging from 0.3 THz to 0.9 THz. We study the far-field radiation, electric field phase, amplitude characteristics, and mode purity with different topological charges. The simulation results are in good agreements with the theoretical predictions.

Carrier-capture-assisted optoelectronics based on van der Waals materials to imitate medicine-acting metaplasticity

Recently, researchers have focused on optoelectronics based on two-dimensional van der Waals materials to realize multifunctional memory and neuron applications. Layered indium selenide (InSe) semiconductors satisfy various requirements as photosensitive channel materials, and enable the realization of intriguing optoelectronic applications. Herein, we demonstrate InSe photonic devices with different trends of output currents rooted in the carrier capture/release events under various gate voltages. Furthermore, we reported an increasing/flattening/decreasing synaptic weight change index (∆Wn) via a modulated gate electric field, which we use to imitate medicine-acting metaplasticity with effective/stable/ineffective features analogous to the synaptic weight change in the nervous system of the human brain. Finally, we take advantage of the low-frequency noise (LFN) measurements and the energy-band explanation to verify the rationality of carrier capture-assisted optoelectronics applied to neural simulation at the device level. Utilizing optoelectronics to simulate essential biomedical neurobehaviors, we experimentally demonstrate the feasibility and meaningfulness of combining electronic engineering with biomedical neurology.

Neutral Wind Profiles During Periods of Eastward and Westward Equatorial Electrojet

AbstractThe equatorial electrojet (EEJ) is a band of zonal electric current flowing along the magnetic equator in the dayside E‐region ionosphere. The direction of the EEJ is often eastward but sometimes westward. The mechanism for generating westward EEJ is not fully understood. This study examines the relationship between the eastward/westward EEJ and equatorial neutral winds using simultaneous observations of the EEJ from the European Space Agency's Swarm satellite mission and thermospheric winds from the Michelson Interferometer for Global High‐resolution Thermospheric Imaging on NASA's Ionospheric Connection Explorer mission during December 2019–January 2021. Significant differences are found in the average zonal wind profiles between times of eastward and westward EEJ. The EEJ intensity correlates negatively (R = −0.54) and positively (R = 0.58) with the eastward wind velocities at ∼110 and ∼140 km, respectively. The results suggest that the modulation of the zonal electric field by the equatorial zonal wind plays a role in producing the westward EEJ.