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To mimic the intricate and adaptive functionalities of biological ion channels, electrohydrodynamic ion transport has been studied extensively, albeit mostly, across uniformly charged nanochannels. Here, we analyze the ion transport under coupled electric field and pressure across heterogeneously charged nanopores with oppositely charged sections on their lateral surface. We only consider such pores with symmetric hourglass-like and cylindrical shapes to focus on the effects of the non-uniform surface charge distribution. Finite-element simulations of a continuum model demonstrate that a pressure applied in either direction of the pore-axis equally suppresses or amplifies the ionic conductance, depending on the electric field polarity, by distorting the quasi-static distribution of ions in the pore. The resulting anomalous mechanical deactivation and activation of ionic current under opposite voltage biases exhibit the functional modularity of our setup, while their intensities are highly tunable, substantially greater than those of analogous behaviors in other nanochannels, and fundamentally correlated to ionic current rectification (ICR) in our pores. A detailed study of ICR subsequently reveals its counterintuitive non-monotonous variations, in the pores, with the magnitude of applied voltage and the pore length, that can help optimize their diode-like behavior. We further illustrate that while the hourglass-shaped nanopores yield the more efficient mechanical suppressors of ion transport, their cylindrical analogs are the superior rectifiers and mechanical amplifiers of ion conduction. Therefore, this article provides a blueprint for the strategic design of nanofluidic circuits to attain a robust, modular, and tunable control of ion transport under external electrical and mechanical stimuli. [ABSTRACT FROM AUTHOR]

Solar-driven semiconductor photocatalysts are highly appealing in applications of environmental remediation and energy conversion. However, photocatalytic reactions, particularly oxygen evolution reaction (OER), are often constrained by the swift recombination of electron–hole pairs, thereby resulting in low reaction efficiency. Although it is effective to separate charge carriers by constructing heterojunctions to form built-in electric field, the lattice mismatch and inefficient interlayer charge transfer of heterojunctions in the photocatalysts limit their further development. Here, we propose a new strategy by constructing an internal electric field for OER through an individual piezoelectric two-dimensional material. The results indicate that the piezoelectric effect regulates the electronic structure, reduces bandgap, improves light absorption efficiency, and that the displacement of positive and negative charge centers is the key factor in the enhanced OER. This research indicates the feasibility of combining piezoelectric properties of two-dimensional materials with OER (1.19 eV), providing new insights and guidance for applying the piezoelectric effect in the OER and opening up a way to promote efficient separation of charge carriers. [ABSTRACT FROM AUTHOR]

The possibility observation of the electric field controlled multicaloric response through quasi-isostatic compression as a result of the converse piezoelectric effect was demonstrated on the cylindrical type magnetoelectric composite MnAs/PZT. It was shown that an electric voltage of 100 V corresponding to an electric field of E ∼0.3 kV/mm applied to the walls of the piezoelectric component PZT of the MnAs/PZT composite contributes to an increase in the maximum adiabatic temperature change by 0.2 K in the temperature range of the magnetostructural phase transition of MnAs ∼317 K at a magnetic field change of 1.8 T. Numerical analysis using the finite element method has shown that an electric field voltage of 100 V is capable of creating a quasi-isostatic mechanical stress in the region inside a cylindrical PZT tube of ∼3 MPa. Moreover, in the region of weak pressures up to 10 MPa, the contribution to the total adiabatic temperature change from piezo-mechanical compression linearly depends on the electrical voltage that can be used for control by magnetic and caloric properties of multicaloric materials. [ABSTRACT FROM AUTHOR]

Heterojunction catalysts in the field of hydrogen evolution reaction (HER) from electrocatalytic water splitting have recently become a hot research topic. In this paper, we systematically calculated the HER catalytic performance of a MoS2/CoS2 heterojunction for the first time, considering the effect of edge sites regulation, strain and electric field. The results indicate that the MoS2/CoS2 heterojunction exhibits synergistic catalytic performance compared to MoS2 and CoS2, the HER catalytic activity of which can be improved by exposing more edge sites or regulating the S content on the edges, with an optimized ratio of 25%. Surprisingly, applying strain has a slight effect on the catalytic activity of the edge, however, an obvious effect on the basal plane. For example, applying 2% tensile strain on the MoS2/CoS2 heterojunction can improve the edge catalytic performance by 13%, and for the basal plane, this value can reach 92%. In this case, the catalytic performance of the basal plane is better than that of the edge with 2% and without strain. Since the basal plane accounts for the majority of the two-dimensional catalysts, the catalytic performance of the basal plane is generally much lower than that of the edge. This discovery is of great significance, which means by adjusting strain, the catalytic performance of the heterojunction catalyst is likely to be improved by orders of magnitude. Moreover, considering the actual experimental process, we also calculated the effect of the electric field and found that 0.7 V/Å electric field can enhance the HER catalytic activity of the MoS2/CoS2 heterojunction by 23%. [ABSTRACT FROM AUTHOR]

Al2O3/ZrO2 (A/Z) layers with embedded Pt nanoparticles (Pt-nps) at the interface of A/Z have been used to create a dielectric film with an enhanced permittivity. The Pt-nps and dielectrics are both grown by the atomic layer deposition process, which is complementary metal–oxide–semiconductor compatible. In order to control the thickness ratio of Pt-nps in the overall dielectrics more easily, the thickness of the ZrO2 layer is changed from 12 to 30 nm with a fixed thickness of 12 nm for Al2O3 and constant growth cycles of 70 for Pt-nps. The results show that the introduction of Pt-nps is beneficial to the enhancement of the dielectric permittivity. As the thickness of ZrO2 is 30 nm, the capacitance density increases from 2.5 to 5.1 fF/μm2 with the addition of Pt-nps, i.e., a doubling of the capacitance density achieved. Additionally, the leakage current at 2 V increases from 1.1 × 10−8 to 1.5 × 10−7 A/cm2. Furthermore, the dielectric breakdown field decreases from 5.4 to 2.7 MV/cm. The electric field distribution simulation and charging–discharging test imply that interfacial polarization is built at the interface of Pt-nps and the dielectric films, which contributes to the dielectric permittivity enhancement, and local electric field increasing in the affinity of Pt-nps gives rise to the deterioration of the leakage current and breakdown electric field. [ABSTRACT FROM AUTHOR]

We have characterized polarization switching kinetics of Hf0.5Zr0.5O2 (HZO) at cryogenic temperature (T) down to 100 K. By the nucleation-limited-switching model with Lorentzian distribution fittings, the dependences of the average switching time (log τ1) and switching time distribution (ω) on T are extracted. As T decreases from 300 to 100 K, log τ1 first rapidly decreases and then gradually stabilizes. Meanwhile, ω exhibits different trends under different external electric fields (Eext), decreasing under low Eext while increasing under high Eext, eventually stabilizing at non-zero constants. With the further decrease in T (<100 K), log τ1 and ω exhibited by HZO are almost unchanged, indicating the intrinsic properties of ferroelectric multiple domains, which are different from the prediction in previous literature studies that log τ1 and ω will linearly decrease as T decreases. [ABSTRACT FROM AUTHOR]

A highly sensitive terahertz stereo metasurface sensor, characterized by a high quality factor (Q-factor) and based on dual toroidal dipole (TD) resonance, has been proposed. The optimal structural parameters are ascertained by comparing the pertinent parameters of the stereo and planar structures in relation to TD modal excitation. The effective excitation of the TD mode is demonstrated using the calculations of multipole scattered power, reflection spectra, surface currents, electric fields, and magnetic field distributions. It is crucial that the stereo metasurface exhibits simplicity and that the dual TD resonance can be readily excited through simple adjustments in the distance and height of the intermediate gap. It also demonstrates exceptionally high sensitivity and Q-factor, both of which are essential for sensing applications. Moreover, the proposed stereo terahertz metasurface sensor still shows excellent sensing performance in a wide range of incidence angles (±40°), which is of great significance for practical applications. In conclusion, this structure offers a novel design framework for high-performance terahertz sensors based on the TD mode. [ABSTRACT FROM AUTHOR]

Zwitterions have been shown experimentally to enhance the dielectric constant of ionic media, owing to their large molecular dipole. Many studies since explored the enhancement of ionic conductivity with zwitterion additives as well as bulk behavior of zwitterions. Here, we examine the capacitance behavior of zwitterions between charged parallel plates using a mean-field theory. Employing only chain connectivity of a cation and anion with neutral monomers in between with mean-field electrostatics, we show that our model captures the high-dielectric behavior of zwitterions. We also predict an optimum in the capacitance of zwitterionic media as a function of chain length. To address the issue of zwitterion screening near charged surfaces, we demonstrate that zwitterions simultaneously partially screen charged walls and act as a pure dielectric that propagates the electric field far from the surface. Moreover, we show that salt solutions with zwitterionic additives outperform the energy density of both salt-only and zwitterion-only capacitors. We find that salt-only capacitors perform better at low applied potential, whereas salt capacitors with zwitterionic additives perform better at high applied potential. [ABSTRACT FROM AUTHOR]

Ice accumulation under static electric fields presents a significant hazard to transmission lines and power grids. Contemporary computational studies of electrofreezing predominantly probed excessive electric fields (109 V/m) that are significantly higher than those typically encountered in proximity to transmission lines. To elucidate the influence of realistic electric fields (105 V/m) on ice crystallization, we run extensive molecular dynamics (MD) simulations across dual ice–water coexistence systems. Three aspects of work were accordingly examined. First, we investigated the influence of the effect of static electric fields, with a strength of 105 V/m, along three orthogonal axes on the phase transition during the encountered freezing and melting processes. Second, we established the mechanism of how the direction of an electric field, the initial ice crystallography, and the adjacent crystal planes influence the solidification process. Third, the results of our MD simulations were further post-processed to determine the dipole moment, radial distribution, and angle distribution resulting from the static electric field. Our results indicate that while weak electric fields do not cause complete polarization of liquid water molecules, they can induce a transition to a more structured ice-like geometry of the water molecules at the ice–water interphase region, particularly when applied perpendicular to the ice–water interphase. Notably, the interface adjacent to cubic ice exhibits a greater response to the electric fields than that adjacent to hexagonal ice. This is attributable to the intrinsic differences in their original hydrogen bonding networks. [ABSTRACT FROM AUTHOR]

Understanding how external electric fields (EFs) impact the properties of aqueous molecules is crucial for various applications in chemistry, biology, and engineering. In this paper, we present a study utilizing molecular dynamics simulation to explore how direct-current (DC) and alternative-current (AC) EFs affect hydrophobic (n-triacontane) and hydrophilic (PEG-10) oligomer chains. Through a machine learning approach, we extract a 2-dimensional free energy (FE) landscape of these molecules, revealing that electric fields modulate the FE landscape to favor stretched configurations and enhance the alignment of the chain with the electric field. Our observations indicate that DC EFs have a more prominent impact on modulation compared to AC EFs and that EFs have a stronger effect on hydrophobic chains than on hydrophilic oligomers. We analyze the orientation of water dipole moments and hydrogen bonds, finding that EFs align water molecules and induce more directional hydrogen bond networks, forming 1D water structures. This favors the stretched configuration and alignment of the studied oligomers simultaneously, as it minimizes the disruption of 1D structures. This research deepens our understanding of the mechanisms by which electric fields modulate molecular properties and could guide the broader application of EFs to control other aqueous molecules, such as proteins or biomolecules. [ABSTRACT FROM AUTHOR]

The second-order nonlinear Hall effect in 8-Pmmn monolayer borophene under the influence of an out-of-plane electric field and intrinsic spin–orbit interaction is reported. This unconventional response sensitive to the breaking of discrete and crystal symmetries can be tuned by the applied electric field, which can vary the bandgap induced by spin–orbit coupling. It is described by a Hall conductivity tensor that depends quadratically on the applied electric field. We find that the nonlinear Hall effect strongly depends on the spin polarization. In particular, it exhibits out of the phase character for spin-up and spin-down states. Remarkably, it undergoes a phase flip in the spin-up state at a large out-of-plane electric field that generates a staggered sublattice potential greater than the spin–orbit interaction strength. It is shown that the nonlinear Hall effect in the system originates from the broken inversion symmetry that plays an indispensable role in developing finite Berry curvature and its relevant dipole moment. It is found that at zero temperature, the nonlinear Hall response is maximal when the Fermi energy is twice the bandgap parameter and vanishes at large Fermi energies. Notably, the peak of nonlinear Hall response shifts to lower Fermi energies at finite temperature. [ABSTRACT FROM AUTHOR]

Electromagnetic applications of composites often impose constraints on the internal electric fields, such as an upper limit on the field strength to prevent local heating or dielectric breakthrough. However, owing to heterogeneity, the local fields in a composite differ from those in a homogeneous material. Moreover, they are accessible neither by experiment nor by effective medium theories, at least for arbitrary microstructures. In this work, we use numerical simulations to evaluate the electric field distribution and the effective permittivity for 3D systems of monodisperse impenetrable spheres dispersed in a continuous matrix phase. We restrict ourselves to loss-free dielectric materials and to a random spatial distribution of particles. Samples are placed in a parallel plate waveguide and exposed to a transverse electromagnetic wave. The local field amplitudes are calculated via the finite element method and are normalized to those of a homogeneous sample exhibiting the same effective permittivity and geometry. We analyze the distribution of the local electric field strength in both constituents, namely, particles and matrix. Thus, we evaluate mean values and standard deviations as well as the field strengths characterizing the highest and lowest percentiles. Increasing particle concentration or permittivity enhances heterogeneity, and so the local electric field strength in some domains can become much higher than its average value. The methods we apply here can also be used in further investigations of more complex systems, including lossy materials and agglomerating particles. [ABSTRACT FROM AUTHOR]

In this paper, a sandwich structure metamaterial was designed, in which the substrate is radio frequency (RF) F4B, and the metal pattern of copper is prepared by the substrate on both sides. Analyzed the transmission of the structure, and the quad-band and reciprocal electromagnetically induced transparency (EIT)-like phenomena of the structure were obtained. The physical mechanism of the EIT-like phenomenon was explained by the electric field distribution. Discussing the size of the structure, the influence of structure parameters on EIT-like phenomena was further illustrated. By comparing the measured results with the calculated results in a microwave anechoic chamber, the results are in good agreement. This structure has potential applications in multi-band filtering, sensing, and other fields. [ABSTRACT FROM AUTHOR]

Electric field induced time-dependent second harmonic generation (TD-SHG) is an emerging sensitive and non-contact method for qualitatively/quantitatively probing semiconductor parameters. The TD-SHG signal is related to the evolution of the built-in electric field due to laser-induced electron generation and transportation. Here, we conducted a comprehensive study of fixed charge density (Q ox ) and interface state density (D it ) using the conventional conductance method to compare them with the SHG signal from TD-SHG. The extracted Q ox is around 2.49 × 1010 cm−2 regardless of SiO2 thickness, corresponding to the constant SHG intensity at the minimum of TD-SHG. The extracted D it linearly decreases with the SiO2 thickness, which is related to the linear change of extracted time constant from TD-SHG. Therefore, the TD-SHG, being a sensitive and non-contact method as well as simple and fast, can serve as an alternative approach to test the semiconductor parameters, which may facilitate semiconductor testing. [ABSTRACT FROM AUTHOR]

Electroporation technique induced by high-voltage pulses has been successfully used to ablate tumor cells while preserving the function of normal blood vessels. Generally, the tumor blood vessels can provide a pathway to draw nutrients for tumor growth and contribute to invasion and metastasis, which is an obstacle to tumor treatment. The electroporation study of the endothelial cell, which is important in the vasculature microenvironment, is helpful to investigate the influence on both tumor and normal blood vessels. This study built a multicell-layer model of the vascular microenvironment to investigate the discriminative electroporation effect between normal and tumor blood vessels by high-frequency bipolar pulses (HFBPs) and monopolar pulses (MPs). The simulation results showed that both pore number and electroporation region in normal blood vessels are significantly lower than those in tumor blood vessels. The rich vascular smooth muscle cells existed in the normal blood vessels play a protective function for endothelial cells, compared with tumor blood vessels. However, the differences in pore number and electroporation region between normal and tumor blood vessels are gradually smaller with an increased electric field, which demonstrates that the electroporation pulse with higher intensity damages both normal and tumor blood vessels. HFBPs generate a weaker electroporation effect on both normal and tumor blood vessels than traditional MP. However, HFBPs are more suitable to electroporate tumor blood vessels, while preserving the normal blood vessels. Moreover, this study could also provide a multicell-layer model that can be used to analyze the cell electroporation effect in the vascular microenvironment. [ABSTRACT FROM AUTHOR]

An experimental evaluation is presented of a two-equation model for the low frequency (< 25 kHz), large amplitude (> --> 100 % of mean) discharge oscillations exhibited by a 9-kW class magnetically shielded Hall thruster. The model is based on a theoretical treatment of the "breathing mode" oscillations in Hall thrusters (Barral and Peradzyński, "A new breath for the breathing mode," IEPC-2009-070) and includes governing equations for fluctuations in the discharge current and the spatially averaged neutral density in the thruster channel. The derivation of the governing equations is reviewed, and the key simplifying assumptions are formulated in terms of comparisons between the magnitudes of relative fluctuations in spatially averaged plasma properties. Experimental measurements are performed of these plasma properties at an operating condition of 300 V discharge voltage and 10 A discharge current. It is found that all quantities of interest such as drift speed, electric field, and temperature fluctuate on the timescale of the low frequency oscillations. However, the relative phasing of these properties combine in such that the key assumptions of the model are satisfied—all but the neutral density and discharge fluctuations can be neglected in the equations for neutral density and current oscillations. A physical interpretation of the validity of the assumptions is presented, and the model is discussed in the context of its extensibility to other operating conditions. The validated model forms the basis for a parametric study presented in Part II of mode transitions and the criterion for these transitions in a magnetically shielded Hall thruster. [ABSTRACT FROM AUTHOR]

Vibrational sum frequency spectra provide information about interfaces that is sensitive to the orientation of molecules, their electronic environment, and the local electric fields. Here, we use molecular dynamics simulations in order to study a surfactant, para-cyanophenol, at the air–water interface. The volume fractions of water and the organic surfactant are considered at various points over the nanometer-scale region in a Lorentz–Lorenz model. We find that the calculated ratios of nonlinear susceptibility tensor elements are in agreement with experimental data only when this depth profile was considered. We also use these data to evaluate the ratio of the C–N hyperpolarizability tensor elements in the interfacial region. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) have potential applications in separation membranes and nanofluidic devices. It is well known that the behavior of water molecules confined in CNTs is affected by surface functional groups and external electric fields, leading to structural changes. The understanding of these structural changes of water within various CNTs is crucial, particularly in the context of material separation. While there have been many investigations into the effects of individual specific functional groups, a comprehensive understanding of the effect of these functional groups and the electric fields they generate on water molecules remains elusive. In this study, we investigate the properties of water molecules in tip-charged CNTs of (8,8), (10,10), and (12,12) chiral vectors with positive charges at one tip and negative charges at the other tip. Abstraction of ionized functional groups as tip charges enables a comprehensive understanding that is independent of individual functional groups. The symmetrically arranged tip-charges spontaneously generate a strong and symmetric electric field in the CNTs. However, the strength and directionality of the electric field are non-uniform and complex. In the interiors of (8,8) and (10,10) tip-charged CNTs, helical and square structures, which have disturbances caused by the non-uniformity of the electric field, are observed. The properties of the water molecules differed significantly in the center of the CNTs and near positive and negative charges, despite the electric field symmetry. In (12,12) tip-charged CNTs with 12 charges, a local ring structure is observed in the vicinity of negative charges but not in the vicinity of positive charges. It is concluded that the water structures in tip-charged CNTs have different characteristics from those in plain CNTs under a uniform electric field. [ABSTRACT FROM AUTHOR]

We have used surface plasmon resonant metal gratings to induce and probe the dielectric response (i.e., electro-optic modulation) of ionic liquids (ILs) at electrode interfaces. Here, the cross-plane electric field at the electrode surface modulates the refractive index of the IL due to the Pockels effect. This is observed as a shift in the resonant angle of the grating (i.e., Δϕ), which can be related to the change in the local index of refraction of the electrolyte (i.e., Δnlocal). The reflection modulation of the IL is compared against a polar (D2O) and a non-polar solvent (benzene) to confirm the electro-optic origin of resonance shift. The electrostatic accumulation of ions from the IL induces local index changes to the gratings over the extent of electrical double layer (EDL) thickness. Finite difference time domain simulations are used to relate the observed shifts in the plasmon resonance and change in reflection to the change in the local index of refraction of the electrolyte and the thickness of the EDL. Simultaneously using the wavelength and intensity shift of the resonance enables us to determine both the effective thickness and Δn of the double layer. We believe that this technique can be used more broadly, allowing the dynamics associated with the potential-induced ordering and rearrangement of ionic species in electrode–solution interfaces. [ABSTRACT FROM AUTHOR]

The plane-wave pseudopotential (PW-PP) formalism is widely used for the first-principles electronic structure calculation of extended periodic systems. The PW-PP approach has also been adapted for real-time time-dependent density functional theory (RT-TDDFT) to investigate time-dependent electronic dynamical phenomena. In this work, we detail recent advances in the PW-PP formalism for RT-TDDFT, particularly how maximally localized Wannier functions (MLWFs) are used to accelerate simulations using the exact exchange. We also discuss several related developments, including an anti-Hermitian correction for the time-dependent MLWFs (TD-MLWFs) when a time-dependent electric field is applied, the refinement procedure for TD-MLWFs, comparison of the velocity and length gauge approaches for applying an electric field, and elimination of long-range electrostatic interaction, as well as usage of a complex absorbing potential for modeling isolated systems when using the PW-PP formalism. [ABSTRACT FROM AUTHOR]

A novel high-power AlGaN/GaN heterojunction lateral photoconductive semiconductor switch (PCSS) based on the SiC substrate is proposed, which achieves high dark-state resistance characteristics by groove etching. Under the action of biased electric field and incident laser, a high concentration of two-dimensional electron gas is formed at the heterojunction interface. The photo-generated free carriers transport along the heterojunction interface, which improves the utilization efficiency of photo-generated carriers. Moreover, the simulation of the current density distribution of the PCSS provides theoretical support for this phenomenon. Compared with the conventional GaN PCSS, the power capacity and conduction characteristics are further improved. The test results show that the output current of the device increases significantly after the introduction of the AlGaN/GaN heterojunction. At the biased voltage of ∼34 kV, the maximum output current of the AlGaN/GaN PCSS reaches 205 A. [ABSTRACT FROM AUTHOR]

Piezoresponse force microscopy (PFM) is one of the most widespread methods for investigating and visualizing ferroelectric domain structures down to the nanometer length scale. PFM makes use of the direct coupling of the piezoelectric response to the crystal lattice, and hence, it is most often applied to spatially map the three-dimensional (3D) near-surface domain distribution of any polar or ferroic sample. Nonetheless, since most samples investigated by PFM are at least semiconducting or fully insulating, the electric ac field emerging from the conductive scanning force microscopy (SFM) tip penetrates the sample and, hence, may also couple to polar features that are deeply buried into the bulk of the sample under investigation. Thus, in the work presented here, we experimentally and theoretically explore the contrast and depth resolution capabilities of PFM, by analyzing the dependence of several key parameters. These key parameters include the depth of the buried feature, i.e., here a domain wall (DW), as well as PFM-relevant technical parameters such as the tip radius, the PFM drive voltage and frequency, and the signal-to-noise ratio. The theoretical predictions are experimentally verified using x-cut periodically poled lithium niobate single crystals that are specially prepared into wedge-shaped samples, in order to allow the buried feature, here the DW, to be "positioned" at any depth into the bulk. This inspection essentially contributes to the fundamental understanding in PFM contrast analysis and to the reconstruction of 3D domain structures down to a 1 μ m-penetration depth into the sample. [ABSTRACT FROM AUTHOR]

Polyurethanes have been extensively studied for their strong electromechanical response. Previous studies have mainly investigated the impact of electrical charges on these polymers' DC conductivity, which was measured on the order of 10−10 S/m. The movement of electric charges is responsible for the macroscopic deformation of polymer films under an electric field. However, this study focused primarily on electric fields below 107 V/m, where the electric current complies with Ohm's law. In this paper, we examine the electric current above this field value and observe a deviation in the current from linearity with the applied field, especially for a high electric field of 106–107 V/m. This change is known in polymers under high electric fields but has never been observed in polyurethane. This suggests the injection of electrode charges into the polymer material. This article provides the threshold at which the transition occurs from linear (Ohm's law) to nonlinear conduction as a result of injected electric charges. [ABSTRACT FROM AUTHOR]

Excess emission has been observed from velvet cathodes with total emission times >150 ns. In this diode experiment, we produce a sub-relativistic electron beam with the ability to consistently change γ from 1.2 to 1.5 and β = 0.5–0.75. Electron emission in this particular diode geometry requires electric fields >40 kV/cm. The current increases at steady rates >0.05 A/ns after the head of the pulse, indicating an expansion of the emission surface and reduction in the effective AK gap. Small transients of excess emission (or arcs) are consistently observed for current pulses exceeding 150 ns. The excess emission results in beam loaded levels ≥ 10 kV on the diode voltage. The effects described here are compounded as diode voltage is increased. The principal objective of these experiments is to quantify electric field emission thresholds, current ramps, excess emission delays, effective beam loading, and impedance collapse. [ABSTRACT FROM AUTHOR]

Optical biosensors with their sensitivity, compact design, and reliability stand out as versatile tools capable of detecting a wide range of analytes. Recently, nanophotonic structures supporting bound states in the continuum (BIC) modes have been actively studied, which is especially interesting for biosensing applications due to their high quality (Q) factor and strongly localized electric field, achieving favorable interaction between field and nanometer scale analyte on the sensing surface. Herein, we demonstrate an optical label-free sensing by accidental or Friedrich–Wintgen (FW) BIC supported on silicon nitride gratings. We compared the sensing performance in terms of bulk, and surface sensitivity, and figure of merit with FW-BIC in the leaky regime and with a symmetry-protected (SP) BIC, which are also supported by the studied platform. We exploit the fact that for FW-BIC a high-Q factor up to 498 comparable to that of SP-BIC (up to 425) retains for a much larger set of interrogation angles, providing excellent interrogation stability. We observed that FW-BIC has slightly higher bulk sensitivity than SP-BIC [186 and 158 nm/RIU (refractive index unit), respectively], but at the same time similar characteristics in terms of surface sensitivity and figure of merit. In addition, we show that both BIC resonances are significantly superior in all respects to the leaky regime due to better field confinement. Finally, the surface of sensing device was also functionalized to detect a cardiac biomarker, myoglobin, exhibiting the limit of detection of 49 ng/ml with clinically relevant level. [ABSTRACT FROM AUTHOR]

Quantum Dot Cellular Automata (QCA) is an emerging trend in the field of nanoelectronics, and computing can be regarded as an alternative to the traditional complementary metal–oxide–semiconductor technology. The paper is devoted to the study of the key functional properties of the cells for molecular QCA based on mixed valence molecules. The theoretical results for the heat dissipation under the conditions of the fast nonadiabatic switching event and cell–cell response function are obtained in the framework of the quantum-mechanical vibronic approach. These results are parameterized using the previous reliable ab initio calculations performed for oxidized norbornadiene and its polycyclic derivatives with variable lengths of the bridge. The comparative analysis of the dimeric and bidimeric molecular cells composed of these compounds is given. It is underlined that the conditions of a strong non-linear response and a low heat release are contradictory. However, despite this problem, a parametric regime is proposed, which provides a low heat release in combination with a strong nonlinear response of the working cell to the electric field induced by the polarized driver cell. [ABSTRACT FROM AUTHOR]

The surface electric field (F) of β-FeSi2 has been investigated by Franz–Keldysh oscillations (FKOs) observed in photoreflectance spectra. The FKO signals were observed in an undoped β-FeSi2 epitaxial layer (3 nm) grown on p+-type β-FeSi2 layers (UP+ structure) by molecular beam epitaxy. The surface electric field obtained from the FKO at 11 K was F = 220 kV/cm. The surface electric field was almost independent of the excitation light power and temperature, showing that the surface electric field was not affected by the surface photovoltage effect. In the dependence of F on the thickness of the undoped layer (d), F was nearly constant at d = 2–56 nm. The result showed that the surface electric field of β-FeSi2 was applied to a thin region (<2 nm) at the surface. [ABSTRACT FROM AUTHOR]

This paper reports the changes in morphology and topographic roughness on the surface of a pristine TlGaS e 2 layered crystal caused by an external electric field applied perpendicular to the layer plane at room temperature. These electric-field-induced surface reconstructions and modifications in the TlGaS e 2 sample were monitored through x-ray reflectivity, x-ray diffraction, and atomic force microscopy techniques. Two distinct electric-field-induced surface responses have been observed: the shifting of the XRD peaks to the higher Bragg angles and the variations in the XRR curves depending on the strength and polarity of the applied external electric fields. AFM results show that the applied electric field leads to a reproducible transformation of the surface roughness of the TlGaS e 2 single crystal from smooth to disheveled, with well-defined depth protrusions. The relaxation time of these surface topological configurations induced under an applied dc electric field was found to be much longer than a few days. The electrostatic capacitive behavior of this two-dimensional semiconducting material is believed to be caused by lattice distortions and the formation of inner stresses (strains) during electric field poling, as well as a drop in the unit-cell characteristics of TlGaSe2. The current–voltage (I–V) measurements show a pronounced nonlinear relationship for a previously poled sample. This nonlinearity is attributed to the field-effect-induced capacitance in TlGaS e 2. Electromigration of intrinsic defects such as Se-anion vacancies, which are already present in the crystal lattice structure of virgin TlGaS e 2 , may diffuse into the sample surface from a bulk (or vice versa) during electric field applications. Finally, employing DFT simulations, we present that the Se-anion vacancy model may be beneficial because changes in the charge state of metal ions positioned around selenium vacancies could be expected. The slightly asymmetric capacitance with respect to the polarity of the bias potential applied to the top surface of TlGaS e 2 is justified by our theoretical calculations. [ABSTRACT FROM AUTHOR]

Given the extensive use of fluorination in molecular design, it is imperative to understand the solvation properties of fluorinated compounds and the impact of the C–F bond on electrostatic interactions. Vibrational spectroscopy can provide direct insights into these interactions by using the C–F bond stretching [v(C–F)] as an electric field probe through the vibrational Stark effect (VSE). In this work, we explore the VSE of the three basic patterns of aliphatic fluorination, i.e., mono-, di-, and trifluorination in CF, CF2, and CF3 groups, respectively, and compare their response to the well-studied aromatic v(C–F). Magnitudes (i.e., Stark tuning rates) and orientations of the difference dipole vectors of the v(C–F)-containing normal modes were determined using density functional theory and a molecular dynamics (MD)-assisted solvatochromic analysis of model compounds in solvents of varying polarity. We obtain Stark tuning rates of 0.2–0.8 cm−1/(MV/cm), with smallest and largest electric field sensitivities for CFaliphatic and CF3,aliphatic, respectively. While average electric fields of solvation were oriented along the main symmetry axis of the CFn, and thus along its static dipole, the Stark tuning rate vectors were tilted by up to 87° potentially enabling to map electrostatics in multiple dimensions. We discuss the influence of conformational heterogeneity on spectral shifts and point out the importance of multipolar and/or polarizable MD force fields to describe the electrostatics of fluorinated molecules. The implications of this work are of direct relevance for studies of fluorinated molecules as found in pharmaceuticals, fluorinated peptides, and proteins. [ABSTRACT FROM AUTHOR]

Irradiation of semiconductors by energetic beams generates excess electrons and holes and may cause device degradation or failure. Both gradual degradation by total ionizing radiation (TID) and sudden degradation/failure (soft/hard breakdown) by a combination of energetic heavy ions and high voltages (typically single-event effects or SEEs) are mediated by excess carriers. The role of defect dynamics in TID degradation has been adequately understood by a combination of experiments and density-functional-theory (DFT) quantum calculations, but little has been done so far to document a role for ion-induced defects in SEE. Here, we report proof-of-principle DFT calculations in a model cubic GaN system for two defect-related excess-carrier phenomena that can play a role in various forms of device degradation and failure. The first phenomenon is the existence, dynamics, and potential roles of defect-induced quasi-localized "resonant states" in the energy-band continua. These states can enhance TID-excess-carrier and hot-carrier degradation. Furthermore, they evolve and multiply during energetic-ion-induced atom recoils and defect creation (displacement damage) and can potentially serve as excess-carrier conduction paths in SEE. The second phenomenon is the conversion of isolated vacancies into nanovoids that can participate in the formation of conducting defect "nanowires" dressed by resonances or in explosive SEE hard breakdowns. [ABSTRACT FROM AUTHOR]

We investigate the effects of the circularly polarized light (CPL) and the electric field (EF) on the nonlocal transport in a silicene-based antiferromagnet/superconductor/ferromagnet (AF/S/F) asymmetrical junction. For case I (II), the CPL and the EF are applied simultaneously in the antiferromagnetic (ferromagnetic) region, whereas in the ferromagnetic (antiferromagnetic) region, only a constant EF is considered. The spin-valley-resolved conductance can be turned on or off by adjusting the CPL or the EF. The AF/S/F junction can be manipulated as a spin-locked valley filter for case I, while for case II, it can be used not only as a valley-locked spin filter but also as a nonlocal switch between two pure nonlocal processes. Such interesting nonlocal switch effect can be effectively controlled by reversing the direction of the incident energy axis, the handedness of the CPL, or the direction of the EF. These findings may open an avenue to the design and manufacture of the spintronic and valleytronic devices based on the asymmetrical silicene magnetic superconducting heterostructure. [ABSTRACT FROM AUTHOR]

The plasma-wall transition is investigated by a one-dimensional steady-state multifluid model, which was presented in detail in Part I [T. Gyergyek et al., AIP Adv. 14, 045201 (2024)]. In this work, the plasma-wall transition is analyzed for the case where the plasma consists of singly charged positive ions, electrons, and singly charged negative ions. When the temperature and initial density of the negative ions are varied, a transition between two types of solutions of the model is observed. We call them the low and high solution, with respect to the absolute value of the potential drop. When the density and temperature of the negative ions are above a critical value, the low solution is observed. As the mass of the positive ions increases, these critical values also increase, but only until the ion mass is below about 1000 electron masses. With larger ion masses, the critical density of the negative ions and the temperature no longer change. In the low solution, the potential drop in front of the sheath is determined by the negative ions and is smaller in absolute terms than in the case of the high solution, where the potential drop in front of the sheath is determined by the electrons. If the problem is analyzed on the pre-sheath scale, the transition between the low and high solution is very sharp. However, when the neutrality condition is replaced by the Poisson equation, this transition becomes blurred and the solutions of the model equations exhibit oscillations. The role of the smallness parameter is highlighted. It is shown how the initial electric field is determined. Deviation of the negative ion density profile from the Boltzmann relation is discussed. [ABSTRACT FROM AUTHOR]

In this work, the electromigration dispersion (EMD) due to the charged electrolytes in microchannels is considered without using the thin electrical double layer assumption. The electrokinetic flow and transport of ions are actuated within a rectangular micro-/nanochannel having a negative surface charge density under the influence of an external electric field. Due to the local variation of the conductivity and the nonvalidity of the electroneutrality condition, the local electric field varies as a function of the solute concentration, wall surface charge density, valency, and Debye layer length. The resulting electrokinetic flow due to the external electric field drives the fluid along with the charged species, where the Taylor–Aris dispersion separates the solutes into their different constituents. The local concentration dependence of the electric field leads to the formation of concentration profiles that are slightly asymmetric with respect to the standard Gaussian distribution. Including a finite Debye layer thickness has an effect on the advection of the species as well as the diffusion of the species. It is found that in cases where Debye layers are thicker, the species advects faster within the microchannel. This might give valuable insights into the nature of the EMD. Our model aims to predict the evolution of ionic concentration at all positions within the channel. A study of the higher-order statistics in skewness and kurtosis has also been conducted to obtain a better understanding of the idealized model consisting of a buffer solution. [ABSTRACT FROM AUTHOR]

The structure of the energy levels of excited symmetric donor–acceptor octupolar molecules suggests a completely symmetric state and a degenerate doublet. For most molecules, the doublet is the first excited state, which is called the normal level order, but there are molecules with the reverse level order. Symmetry breaking charge transfer (SBCT) and its effect on the transient dipole moment in these structures are studied. It has been established that for reverse level order, SBCT is possible only if the reorganization energy exceeds a certain threshold, whereas for the normal level order, there is no such threshold. The lowest completely symmetric excited state is shown to become bright after SBCT. The dependence of the fluorescence transition dipole moment on the SBCT extent is calculated. It was established that the direction and magnitude of the transition dipole moment change similarly to the change in the dipole moment for the reverse level order, whereas for the normal level order, the changes are opposite. The effect of solvent thermal fluctuations on the transition dipole moment is simulated and discussed. A way for controlling the direction of the transition dipole moment by an external electric field is suggested. [ABSTRACT FROM AUTHOR]

Quantum mechanical/molecular mechanics (QM/MM) methods are interesting to model the impact of a complex environment on the spectroscopic properties of a molecule. In this context, a FROm molecular dynamics to second harmonic Generation (FROG) code is a tool to exploit molecular dynamics trajectories to perform QM/MM calculations of molecular optical properties. FROG stands for "FROm molecular dynamics to second harmonic Generation" since it was developed for the calculations of hyperpolarizabilities. These are relevant to model non-linear optical intensities and compare them with those obtained from second harmonic scattering or second harmonic generation experiments. FROG's specificity is that it is designed to study simple molecular liquids, including solvents or mixtures, from the bulk to the surface. For the QM/MM calculations, FROG relies on the Dalton package: its electronic-structure models, response theory, and polarizable embedding schemes. FROG helps with the global workflow needed to deal with numerous QM/MM calculations: it permits the user to separate the system into QM and MM fragments, to write Dalton's inputs, to manage the submission of QM/MM calculations, to check whether Dalton's calculation finished successfully, and finally to perform averages on relevant QM observables. All molecules within the simulation box and several time steps are tackled within the same workflow. The platform is written in Python and installed as a package. Intermediate data such as local electric fields or individual molecular properties are accessible to the users in the form of Python object arrays. The resulting data are easily extracted, analyzed, and visualized using Python scripts that are provided in tutorials. [ABSTRACT FROM AUTHOR]

Oxygen defects are introduced into PbZr0.5Ti0.5O3 films and their impact on ferroelectric behavior, linear dielectric response (LDR), and nonlinear dielectric response (NDR) is studied. Apart from a notable decrease in both polarization and LDR permittivity, the frequency spectra of LDR exhibit a distinctive loss peak. The peak position varies with temperature and oxygen defect concentration. NDR parameters, including the Rayleigh coefficient (α1), the slope (α2) correlating the imaginary part of permittivity with the ac electric field, and the slope (k) between the real and the imaginary parts of permittivity, demonstrate diverse behaviors in response to temperature and oxygen defect concentration. The similarity in the frequency spectra of tanδ and 1/k reveals the correlation between LDR and NDR induced by the presence of oxygen defects. These observations are attributed to the behavior of the single and composite defects associated with oxygen vacancies. [ABSTRACT FROM AUTHOR]

When using metal–organic frameworks (MOFs) as electric field-dependent sensor devices, understanding their dielectric response is crucial as the orientation of polar groups is largely affected by confinement. To shed light on this at the molecular level, the response to a static field was computationally investigated for two structurally related MOFs, depending on their loading with guest molecules. The pillared-layer MOFs differ in their pillar moiety, with one bearing a rotatable permanent dipole moment and the other being non-polar. Two guest molecules with and without polarity, namely, methanol and methane, were considered. A comprehensive picture of the response of the guest molecules could be achieved with respect to both the amount and polarity of the confined species. For both MOFs, the dielectric response is very sensitive to the introduction of methanol, showing an anisotropic and non-linear increase in the system's relative permittivity expressed by a strongly increasing polarization response to external electric fields scaling with the number of confined methanol molecules. As expected, the effect of methane in the non-dipolar MOF is negligible, whereas subtle differences can be observed for the dipolar response of the MOF with rotatable dipolar linker groups. Taking advantage of these anisotropic and guest-molecule-specific confinement effects may open pathways for future sensing applications. Finally, methanol-induced global framework dynamics were observed in both MOFs. [ABSTRACT FROM AUTHOR]

As investigations in the biomedical applications of plasma advance, a demand for describing safe and efficacious delivery of plasma is emerging. It is quite clear that not all plasmas are "equal" for all applications. This Perspective discusses limitations of the existing parameters used to define plasma in context of the need for the "right plasma" at the "right dose" for each "disease system." The validity of results extrapolated from in vitro studies to preclinical and clinical applications is discussed. We make a case for studying the whole system as a single unit, in situ. Furthermore, we argue that while plasma-generated chemical species are the proposed key effectors in biological systems, the contribution of physical effectors (electric fields, surface charging, dielectric properties of target, changes in gap electric fields, etc.) must not be ignored. [ABSTRACT FROM AUTHOR]

Current–voltage characteristics, space- and time-resolved optical emission spectroscopy, and 1D fluid modeling are used to examine the effect of dual-frequency sheath oscillations on the ion and electron transport in dielectric barrier discharges sustained by a combination of low frequency (LF, 50 kHz, 650 V) and radiofrequency (RF, 5.3 MHz, 195 V) voltages, exhibiting the α-to-γ mode transition. On one hand, when polarities of the LF and RF voltages are opposite, an electric field near the LF cathode (due to LF cathode sheath) drives the secondary electrons to the plasma bulk and an opposite electric field between the sheath edge and the LF anode attracts the electrons toward the LF cathode (to maintain quasi-neutrality in the plasma bulk). At the sheath edge, electrons become trapped and ions drift toward the cathode and the anode simultaneously according to their position in the gap. On the other hand, when the RF voltage has the same polarity as the LF voltage, the total applied voltage increases and this yields to enhanced production of electrons and ions in the sheath. To maintain quasi-neutrality in the bulk, the electric field along the gap exhibits the same polarity as the one in the sheath, allowing electrons created in the sheath to be evacuated toward the LF anode. The behavior of the LF cathode is, therefore, controlled by the LF sheath, and, thus, by the LF voltage amplitude, while the behavior in the bulk and at the anode alternates on the time scale of the RF voltage. [ABSTRACT FROM AUTHOR]

The phenomenon of dielectric breakdown in microwave windows restricts the enhancement of power capacity in high-power microwave systems. This process starts with the secondary electron multiplication, which significantly influences the breakdown threshold. In this study, we developed 3D simulation models for rectangular, circular, and annular windows to examine the secondary electron multiplication on their surfaces using the particle-in-cell method. Through a comparative study, we assessed the effects of various input powers, initial emission current densities from particle sources, and magnetic fields. Our findings reveal that the initial field emission current density, which ranges from 10−9 to 109 μA/cm2, marginally affects electron multiplication. However, increased microwave power (with power density ranging from 0.1 to 18.75 MW/cm2) accelerates this multiplication. Strong magnetic fields and non-uniform electric fields further enhance the electron multiplication process. [ABSTRACT FROM AUTHOR]

A wire-on-well (WoW) structure was fabricated using InGaAs/GaAs/GaAsP superlattice device growth technology. This structure modifies the local concentration of carriers in the quantum well and lengthens the carrier lifetime to increase carrier transport efficiency. However, the reason for this remains unclear. Therefore, we investigated the detailed carrier transition properties using photoluminescence (PL) and photoreflectance measurements. Regarding the PL spectra at 4 K, two characteristic peaks at 1.39 and 1.34 eV were observed. Both transitions are attributed to the recombination between the first quantum level of the electron (e1) and that of the heavy hole (hh1). We also discussed the carrier distribution in the WoW structure and found that the maximum carrier existing probabilities for e1 and hh1 are located at different positions. The less overlapping of the wavefunctions causes low transition probability and results in the observed long carrier lifetime. An additional prominent result in the WoW structure is the blue shift attributed to the 1.34 eV PL peak induced by increasing laser excitation power. We found that the blue shift occurred by the screening of the electric field caused by the compressive strain, as in the case of the quantum-confined Stark effect. [ABSTRACT FROM AUTHOR]

As an emerging technology in liquid inactivation, one of the main challenges of pulsed electric fields (PEFs) inactivation lies in quantitatively describing and predicting its lethality to microorganisms. However, due to its cross-scaled complexity and the consequent numerous regulatory factors, there is currently still no unified framework to understand the PEF dose–response relationship and the population dynamics theoretically. In this study, a simple yet powerful model from multiscale coarse-graining method is proposed to simulate the bacterial inactivation in suspensions during PEF processing. The complex dose–response effects at the macroscale are successfully reconstructed from simple evolution rules and several coarse-graining parameters, while considering the damage and death of a single bacterium at the microscale. Our model uncovers the seemingly chaotic and even controversial dose–response relationship of PEF in literatures and systematically explores the regulatory effect of experimental parameters in a unified framework. One of the interesting findings is that PEF with shorter pulsed width enhances lethality and reduces the minimal inhibitory time at a constant energy output per pulse, owing to the phase transitions in three bacterial population dynamics (Bistability mode, Avalanche mode, and Hybrid mode). Our study provides a new insight for numerically modeling PEF lethality in liquid inactivation and could serve as a guide for dosage management in practical applications. [ABSTRACT FROM AUTHOR]

The plasmonic coupling between silver (Ag) and gold (Au) nanoparticles (NPs) under four polarization modes was examined: a longitudinal mode (L-mode), where the electric field of a linearly polarized incident light parallels the dimer axis, and three transverse modes (T-modes), where the electric field of the light is perpendicular to the dimer axis. The coupling was studied using the discrete dipole approximation followed by an in-house postprocessing code that determines the extinction (Qext), absorption (Qabs), and near-field (Qnf) spectra from the individual NPs as well as the whole system. In agreement with the literature results, the extinction/absorption spectra of the whole dimer have two peaks, one near the Ag localized surface plasmon resonance (LSPR) region and the other at the Au LSPR region, with the peak at Ag LSPR being reduced in all modes and the peak at Au LSPR being red-shifted and increased in the L-mode but not in the T-modes. It is further shown that the scattering at the Ag LSPR region is reduced and becomes less than the isolated Ag NPs, but the absorption at the Ag LSPR is increased and becomes greater than the isolated Ag NPs for the 50 nm Ag–Au heterodimer. This suggests that the scattering from Ag NPs is being reabsorbed by the neighboring Au NPs due to the interband electronic transition in Au at that wavelength range. The Qext from the individual NP in the heterodimer shows the presence of the Fano profile on the Au NP but not on the Ag NP. This phenomenon was further investigated by using a dielectric particle (DP) placed near the Ag or Au NPs. The Fano profile appears in the absorbing DP spectra placed near either Ag or Au NPs. However, the Fano profile is masked upon further increases in the refractive index value of the DP particle. This explains the absence of a Fano profile on the Ag NPs in the Ag–Au heterodimer. The large near-field enhancement on both Ag and Au NPs at the Au plasmonic wavelength in the L-mode for large NPs was investigated through a DP-Au system. The large enhancement was shown to arise from a large imaginary component of the DP refractive index and a small real component. Through examination of both the near- and far-field properties of the individual NPs as well as the whole system and examinations of DP-Ag and DP-Au systems, our study provides a new understanding of the couplings between Ag and Au NPs. [ABSTRACT FROM AUTHOR]

A unique on-chip method for the direct correlation of optical properties, with atomic-scale chemical–structural characteristics for a single quantum dot (QD), is developed and utilized in various examples. This is based on performing single QD optical characterization on a modified glass substrate, followed by the extraction of the relevant region of interest by focused-ion-beam–scanning electron microscope processing into a lamella for high resolution scanning transmission electron microscopy (STEM) characterization with atomic scale resolution. The direct correlation of the optical response under an electric field with STEM analysis of the same particle allows addressing several single particle phenomena: first, the direct correlation of single QD photoluminescence (PL) polarization and its response to the external field with the QD crystal lattice alignment, so far inferred indirectly; second, the identification of unique yet rare few-QD assemblies, correlated directly with their special spectroscopic optical characteristics, serving as a guide for future designed assemblies; and third, the study on the effect of metal island growth on the PL behavior of hybrid semiconductor–metal nanoparticles, with relevance for their possible functionality in photocatalysis. This work, therefore, establishes the use of the direct on-chip optical–structural correlation method for numerous scenarios and timely questions in the field of QD research. [ABSTRACT FROM AUTHOR]

The coupling of an electron gas confined by a harmonic potential and submitted to a strong magnetic field tilted in relation to the confining direction creates an excitation called here magneto-polariton. This work describes the origin of this excitation and calculates the energy eigenvalues for different tilted angles. It presents the reasons leading to the crossings and repulsions of the energy bands, the degeneracy of the states, the way the Fermi levels change with the magnetic field, the influence of an external electric field, and how the Hall resistance plateaus change with the change in the tilted angle. [ABSTRACT FROM AUTHOR]

This study analyzes the regulatory mechanism of oxygen vacancy concentration on tail-to-tail charged domain walls (T–T CDWs), along with the writing time, conduction current magnitude, and retention performance of through-type T–T CDWs. The research results show that the highest density and length of T–T CDWs are achieved when the oxygen vacancy concentration is 1 × 1020 cm−3. Moreover, the successful writing of through-type T–T CDWs is limited to a certain electric field range, which is controlled by oxygen vacancy concentration. An increase in the oxygen vacancy concentration leads to a decrease in the maximum and minimum threshold electric fields required for writing through-type charged domain walls. The writing time and conductivity of through-type T–T CDWs determine the information writing speed and signal strength of domain wall memories, and the oxygen vacancy concentration also plays a regulatory role in both aspects. When the oxygen vacancy concentration is 1 × 1020 cm−3, the through-type T–T CDW exhibits the fastest writing speed, requiring only 8 ns. The magnitude of the conduction current of through-type T–T CDWs is directly proportional to the oxygen vacancy concentration. The through-type T–T CDWs formed by the aggregation of oxygen vacancies exhibit excellent retention performance, making them highly promising for applications in ferroelectric domain wall memories. Our research demonstrates that oxygen vacancies have a significant regulatory effect on the morphology and current response of charged domain walls, opening up new avenues for the study of domain wall memories. [ABSTRACT FROM AUTHOR]

Acoustically actuated magnetoelectric (ME) antennas based on resonant magnetoelectric coupling within ferromagnetic/piezoelectric ME laminated composites have recently been considered as a promising solution for antenna miniaturization. However, its radiation performance has been theoretically overestimated, since the negative effects on performances due to the magnetization saturation and the nonlinear mechanical behavior that occur from high-field driving have not been paid enough attention. This work presents a unique equivalent-circuit-based numerical method to analyze the near-field resonance radiation performances of ME antennas driven by high electric fields. In this method, we establish an equivalent circuit of the converse magnetoelectric effect for a ME laminated composite to describe the operating principle of acoustically actuated electromagnetic radiation. The equivalent parameters related to resonance characteristics are determined by fitting the circuit model to the data from frequency response measurements of the near-field magnetic flux density. The validity of the model is verified by comparing the theoretical predictions with the experimental results, in the view of the volume fraction dependence of the mechanical resonance-related radiation characteristics of the fabricated ME composites. Based on the proposed model, the influence of driving voltage amplitude on near-field radiation performances is further analyzed by experimental fitting to the model, and the potential limiting factors of ME antennas are discussed according to the driving-amplitude dependence of parameters obtained from the fit. This work provides an effective and engineering-friendly approach to predict the evolution of ME antenna performances, leading a way to improve the performance limit for resonant magnetoelectric coupling. [ABSTRACT FROM AUTHOR]

GaN/AlxGa1−xN quantum wells were grown by molecular beam epitaxy on high quality bulk (0001) GaN substrates. The quantum well thickness was set in the 6–8 nm range to favor the photoluminescence emission of indirect excitons. Indeed, such excitons are known to be spatially indirect due to the presence of the internal electric field which spatially separates the electron and hole wave functions. The growth conditions were optimized in view of minimizing the photoluminescence peak broadening. In particular, the impact of growth temperature (up to 900 °C) on the surface morphology, structural, and photoluminescence properties was studied. The diffusion of indirect excitons on the scale of tens of micrometers was measured with a micro-photoluminescence setup equipped with a spatially resolved detection. A dedicated model and its analysis allow us to extract from these measurements the exciton diffusion constant and to conclude on the optimum growth conditions for the GaN/AlxGa1−xN quantum well structures suited for studies of quantum collective effects in indirect exciton liquids. [ABSTRACT FROM AUTHOR]

In this work, the piezoelectric properties of chemical solution deposition derived ferroelectric HfO2–CeO2 thin films deposited on platinized silicon substrates are investigated. Large-signal strain-field measurements show an effective piezoelectric coefficient of approximately d 33 , eff = 12.7 pm / V for 17 mol. % cerium under bipolar excitation and d 33 , eff = 8 pm / V under unipolar excitation. Progressive bipolar electric field cycling leads to a reduction in the overall field induced strain although no fatigue with regards to the polarization is observed. To explain this, we propose a model explanation based on changes in the polarization reversal pathway from a primarily ferroelastic, i.e., 90 ° domain wall mediated switching, to a 180 ° type switching. Furthermore, unipolar strain-field measurements reveal a negative intrinsic piezoelectric coefficient in the absence of any ferroelastic contribution, confirming theoretical predictions. The results suggest that the ferroelastic contribution to the field-induced strain needs to be stabilized in Hafnia-based ferroelectric materials to make them more feasible for micro-electromechanical systems. [ABSTRACT FROM AUTHOR]

Dielectric interfaces are crucial to the behavior of charged membranes, from graphene to synthetic and biological lipid bilayers. Understanding electrolyte behavior near these interfaces remains a challenge, especially in the case of rough dielectric surfaces. A lack of analytical solutions consigns this problem to numerical treatments. We report an analytic method for determining electrostatic potentials near curved dielectric membranes in a two-dimensional periodic "slab" geometry using a periodic summation of Green's functions. This method is amenable to simulating arbitrary groups of charges near surfaces with two-dimensional deformations. We concentrate on one-dimensional undulations. We show that increasing membrane undulation increases the asymmetry of interfacial charge distributions due to preferential ionic repulsion from troughs. In the limit of thick membranes, we recover results mimicking those for electrolytes near a single interface. Our work demonstrates that rough surfaces generate charge patterns in electrolytes of charged molecules or mixed-valence ions. [ABSTRACT FROM AUTHOR]