Small Electric Field Research Articles

The enhanced ferroelectric properties of flexible Hf0.85Ce0.15O2 thin films based on in situ stress regulation

As the core component of ferroelectric memories, HfO2-based ferroelectric thin films play a crucial role in achieving their excellent storage performance. Here, we improved the ferroelectric properties and domain switching properties through in situ stress loading during annealing. The thin films are annealed under different bending states by applying different stress actions, and it is observed that, within a certain range of stress bending, the optimization of the ferroelectric properties of the annealed thin films can reach an extreme value. Specifically, under the influence of a small electric field, the 2Pr values of thin films annealed at +10 and −10 mm increased by 87.1% and 71.1%, respectively, compared with the unbent films. Additionally, these thin films exhibit extremely high domain wall mobility and excellent domain switching capabilities. Once the ferroelectric phase is formed through in situ stress modulation, it remains stable even under multiple service environments.

Guanine-based spin valve with spin rectification effect for an artificial memory element.

Non-volatile electronic memory elements are very attractive for applications, not only for information storage but also in logic circuits, sensing devices and neuromorphic computing. Here, a ferroelectric film of guanine nucleobase is used in a resistive memory junction sandwiched between two different ferromagnetic films of Co and CoCr alloys. The magnetic films have an in-plane easy axis of magnetization and different coercive fields whereas the guanine film ensures a very long spin transport length, at 100K. The non-volatile resistance states of the multiferroic spintronic junction with two-terminals are manipulated by a combined action of small external magnetic and electric fields. Thus, the magnetic field controls the relative orientation of the magnetization of the metallic ferromagnetic electrodes, that leads to different magnetoresistance states. The orientation and the magnitude of the electric field controls the orientation of the polarization of the guanine ferroelectric barrier, that leads to different electroresistance states, respectively. Moreover, we have observed a strong interfacial coupling of the two parameters. Consequently, positive and negative magnetoresistance hysteresis loops corresponding to spin rectification effects and non-hysteretic (erased) resistive states are manipulated with the electric field by switching the orientation of the electrical polarization of the organic ferroelectric.

The negative differential resistance of nitrogen implanted TiO2

The microstructure and negative differential resistance (NDR) effect of nitrogen implanted rutile TiO2 were investigated by measuring the XPS, Raman spectra and current voltage curves. It was found that the light illumination has large influence on the NDR effect. Under the illumination of 60 mW laser light, a large NDR with a small electric field (1250 V/cm) is obtained. This electric field is about three orders smaller than that reported in literature (1×106 V/cm). The electric field induced tunneling is the possible mechanism of electric transport at higher field region. The NDR is thought to be related to the light and nitrogen dopant induced reaction including the destroying of water, the scavenging of electron, and the surface oxidation transform of non-stoichiometric TiO2−x to stoichiometric insulating state. The results of this paper are not only useful in understanding the mechanism of NDR, but also useful in providing an effective method in manipulation NDR.

Bandgap opening of ferric chloride intercalated graphene by applying small electric field

Graphene has exceptional properties with great promise for various applications. However, pristine graphene cannot be used in nano-electronics because it lacks a gap in energy dispersion at the Dirac point. Therefore, researchers have been developing methods to open the gap, which would open the door for the use of graphene in a wide range of electronic and photovoltaic devices. Through density functional theory calculations, we identified a specific range of electric field values that could potentially open the Dirac cones and separate the two π (VB) and two π* (CB) bands belonging to each graphene layer in FeCl3 intercalated bilayer graphene. To our knowledge, no such findings have been reported in the literature. These findings could aid in developing a better understanding of the electronic structure of materials and enable the design of more efficient electronic devices.

Verification of electromagnetic simulation capabilities in global gyrokinetic particle-in-cell code GTS

Recently, the numerical scheme presented by Mishchenko et al. [Phys. Plasmas 21, 052113 (2014); 21, 092110 (2014)] enabled explicit gyrokinetic simulations of low-frequency electromagnetic instabilities in tokamaks at experimentally relevant values of plasma β. This scheme resolved the long-standing cancellation problem that previously hindered gyrokinetic particle-in-cell code simulations of magnetohydrodynamic phenomena with inherently small parallel electric fields. Moreover, the scheme did not employ approximations that eliminate critical tearing-type instabilities. Here, we report on the implementation of this numerical scheme in the global gyrokinetic particle-in-cell code GTS. This implementation allows for a more complete and accurate picture of interaction between small scale turbulence and MHD modes in tokamaks. Additionally, we present a comprehensive set of verification simulations of numerous electromagnetic instabilities relevant to present-day tokamaks. These simulations encompass the kinetic ballooning mode, the internal kink mode, the tearing mode, the micro-tearing mode, and the toroidal Alfven eigenmode destabilized by energetic ions, which are all instrumental in understanding tokamak physics. We will also showcase the preliminary nonlinear simulations of kinetic ballooning instabilities and (2,1) island formation due to tearing mode instability. These simulations validate the accuracy of the scheme implementation and pave the way for studying how these instabilities affect plasma confinement and performance.

Tunable MXene/WO3 Fabry−Pérot Microcavity Architecture for Bioinspired Soft Electrochromic Actuators with Vivid Colors

AbstractInspired by stimuli‐responsive creatures in nature, developing devices with synergistic color change and deformation will be of great value for realizing the adaptive variants. Yet, integrating adaptive color variation and deformation into a single device remains elusive. Herein, an intriguing electrochromic actuator based on MXene/WO3 bilayer film is developed with Fabry−Pérot (F–P) microcavity, which successfully integrates both functions of reversible deformation and vivid color variations into the same device. Upon applying a small electric field, the ion intercalation/de‐intercalation can synchronously alter the stress distribution and optical absorption of MXene/WO3, resulting in the dual response of electrochromic phenomenon and ultra‐fast deformation with a maximum angle of 95° within 10 s. Moreover, the F–P microcavity architecture with the physical light interaction additionally endows the bilayer film with a bright color gamut and high color tunability (yellow–green, purple, pink, blue, etc.). Furthermore, an asymmetric soft actuator based on MXene/WO3 bilayer film is assembled, which displays robust grasping ability and excellent cycling stability up to 1000 cycles. These findings may open new opportunities for somatosensory soft robots and next‐generation intelligent robots.

The effect of a constant electric field in an undisturbed plasma on the stability of the electron beam–gas discharge collisional plasma system

This work is devoted to the study of a fast non-relativistic electron beam–gas discharge plasma system within the framework of the kinetic theory of stability. The influence of a constant electric field, collinear beam velocity, on the stability of the system in an undisturbed plasma is studied. It is shown that even a relatively small electric field, which does not significantly affect the energy of the electron beam, can lead to significant changes in the parameters of harmonic disturbances propagating in the electron beam–plasma system in the region of its instability. It was found that the reason for such changes is the drift of plasma electrons, which, as a consequence, leads to a change in the frequency of disturbances in the coordinate system associated with the plasma due to the Doppler effect. The results obtained are demonstrated by calculations based on the kinetic theory of perturbation parameters in a low-voltage beam discharge in rare gases, which is used in the development of plasma electronics devices. The effect of electron-atomic collisions on the stability of the electron beam–plasma system is investigated and compared with the results of other authors' works.

The phase composition, dielectric, and energy storage performance of A-site vacancy modulated BaTiO3 ceramics with Bi(In1/2(Li0.5Ta0.5)1/2)O3 modification

The (1-x)Ba0.94Ce0.04TiO3-xBi(In1/2(Li0.5Ta0.5)1/2)O3 (BCT-BILT) relaxor ferroelectric ceramic system was explored based on the A-site vacancy design and defect dipole engineering. The impacts of different doping concentrations on the phase composition, dielectric and energy storage performance of the BCT-BILT ceramics were studied and discussed in detail. The pure BCT and 0.95BCT-0.05BILT samples exhibited a mixed crystal structure of tetragonal (T) and pseudo-cubic (PC) phase, while the BCT-BILT samples with x > 0.05 possessed a cubic (C) phase, accompanied by the secondary phases of BaBi2Ta2O9 and BaTa2O6. With an increase in the BILT doping concentration, the surface morphologies of the ceramics were continuously modulated, and the dielectric loss had been reduced to 0.001 at 1 kHz, which was beneficial to improve the energy storage properties. Compared to the pure BCT, the breakdown field strength was significantly enhanced owing to the formation of Aurivillius phase BaBi2Ta2O9 and the increased dielectric relaxation. Ultimately, the highest energy storage density of Wrec = 0.7 J/cm3 and high energy conversion efficiency of η = 95 % was realized at the composition of x = 0.05 under a small electric field of 130 kV/cm. Furthermore, the good temperature stability with the ΔWrec/Wrec30°C < 9 % and Δη/η30°C < 6.5 % was acquired for the samples with x = 0.20–0.30 in the temperature range of 30–120 °C, owing to the synergistic roles of the defect dipoles, impurities BaBi2Ta2O9, and polar nanoregions (PNRs). The 0.95BCT-0.05BILT ceramic obtains discharge energy density Wdis of 0.35 J/cm3 and fast discharge speed t0.9 of 312 ns at 60 kV/cm, current density CD of 255.4 A/cm2 and power density PD of 10.2 MW/cm3 at 80 kV/cm. This work is of guiding significance for designing and optimizing energy storage performance of lead-free relaxors from the perspective of defect building and engineering.

Nonlinear Electrophoresis of Microparticles in Shear Thinning Fluids.

The nonlinear electric field dependence of particle electrophoresis has been demonstrated to occur in Newtonian fluids for highly charged particles under large electric fields. It has also been predicted to arise from the rheological effects of non-Newtonian fluids even at small electric fields. We present in this work an experimental verification of nonlinear electrophoresis in shear thinning xanthan gum solutions through a straight rectangular microchannel. The addition of polymer into a Newtonian buffer solution is found to change the electric field dependence from linear to superlinear for electroosmotic, electrokinetic, and electrophoretic velocities. The nonlinear index of each of these electrokinetic phenomena increases with the increasing polymer or buffer concentration, among which electrophoresis exhibits the strongest nonlinearity. Both these observed trends are captured by a dimensionless electrokinetic shear thinning number that depends on the power-law index of fluid viscosity and the Debye length.

Intrinsic multiferroicity in molybdenum oxytrihalides nanowires

Low-dimensional multiferroics, which simultaneously possess at least two primary ferroic order parameters, hold great promise for post-Moore electronic devices. However, intrinsic one-dimensional (1D) multiferroics with the coexistence of ferroelectricity and ferromagnetism are still yet to be realized, which will be not only crucial for exploring the interplay between low-dimensionality and ferroelectric/ferromagnetic ordering but also significant in rendering application approaches for high density information technologies. Here, we present a theoretical prediction of intrinsic multiferroicity in 1D molybdenum oxytrihalides nanowires, especially focusing on MoOBr3 nanowires which could be readily extracted from experimentally synthesized van der Waals MoOBr3 bulk materials. Due to the spatial inversion symmetry spontaneously broken by Mo atoms’ displacements, MoOBr3 nanowires exhibit 1D ferroelectricity with small coercive electric field and exceptional Curie temperature (~570 K). Additionally, MoOBr3 nanowires also possess 1D antiferroelectric metastable states. On the other hand, both ferroelectric and antiferroelectric MoOBr3 nanowires exhibit ferromagnetic ordering on account of the half-filled Mo-dyz orbitals, a moderate tensile strain (~5%) can greatly boost the spontaneous polarization (~40%) and a mild compress strain (~−2%) may readily switch the magnetic easy axis of ferroelectric MoOBr3 nanowires. Our work holds potential candidates for developing innovative devices that exploit intrinsic multiferroic properties, enabling advancements in novel electronic and spintronic applications.

Stable WSeTe/PtTe2 van der Waals heterojunction: Excellent mechanical, electronic, and optical properties and device applications

Janus WSeTe and PtTe2 monolayers have attracted much attention due to their outstanding electronic properties. To explore their combined advantages and to find new physics, we construct WSeTe/PtTe2 vdW heterojunctions and use the most stable configurations A4 and B1 to explore their various physical properties and device applications. It is found that both A4 and B1 hold exceptional mechanical properties. They are type-II semiconductors, and types of band alignment and band gap size can be tuned flexibly by external electric field and vertical strain. Based on such a property, we design a strain-controlled high on–off-ratio mechanical switching device. They also show an excellent light response and high photoelectric power conversion efficiency (PCE), which can be tuned greatly by the external electric field and vertical strain as well. For example, light adsorption in visible and infrared region can be improved greatly by the compressive strain. Particularly, we find for B1 in the intrinsic state or with a small tensile strain of 0.3 Å, or for A4 with small electric field of −0.3 V/Å, they all hold type-II band alignment and have very high PCE and large visible light absorption, based on these results, we propose high-performance solar cell devices.

Stark shift in a Frost-Musulin quantum dot: Analytical solution

In the research, a quantum dot (QD) under an external magnetic field is theoretically investigated. The confining potential applied to the charge carriers is chosen as the Frost-Musulin (FM) potential model. First, the energy eigenvalues and eigenstates have been analytically obtained by Nikiforov-Uvarov (NU) procedure. Then, an electric field is imposed on the system. The Stark shift effect (SSE) has been calculated and an analytical relation has been obtained in terms of the Jacobi polynomials. The findings show that the shift of electron energy states at large, and small electric fields are different. The shift is small at weak electric fields. The electron energy states decrease with the increment of the electric field. The electron states are increased by enhancing the system size. In summary, the SSE can be tuned by setting the electric field, the potential height, and the size of QD.

The negative differential resistance of nitrogen implanted TiO2

The microstructure and negative differential resistance (NDR) effect of nitrogen implanted rutile TiO2 were investigated by measuring the XPS, Raman spectra and current voltage curves. It was found that the light illumination has large influence on the NDR effect. Under the illumination of 60 mW laser light, a large NDR with a small electric field (1250 V/cm) is obtained. This electric field is about three orders smaller than that reported in literature (1×106 V/cm). The electric field induced tunneling is the possible mechanism of electric transport at higher field region. The NDR is thought to be related to the light and nitrogen dopant induced reaction including the destroying of water, the scavenging of electron, and the surface oxidation transform of non-stoichiometric TiO2−x to stoichiometric insulating state. The results of this paper are not only useful in understanding the mechanism of NDR, but also useful in providing an effective method in manipulation NDR.

Achieving high electromechanical response in lead-free BNT-BT ceramics through synergistic A/B-site doping

Lead-free Bi0.5Na0.5TiO3-based ceramics show great promise for achieving high unipolar strain. However, it remains challenging to implement an effective strategy for microstructural designs with high electromechanical response. Herein, a direct composition-engineering method based on A/B-sites doping is adopted to introduce a synergistic effect of reduced oxygen vacancies, lattice distortion, ferroelectric-to-relaxor phase transition, and nano-sized domains, resulting in a high piezoelectric strain coefficient d*33 of 857 pm/V at a small electric field of 4 kV/mm. Furthermore, a large room-temperature maximum polarization (Pm) of 72.4 μC/cm2 was observed at high electric field. A phase transition from coexisting rhombohedral–tetragonal to pseudocubic was engineered by finely tuning the contents of NaTaO3, leading to a decrease in both remnant polarization (Pr) and coercive field (Ec). The phase diagram of 1-x[0.935(Bi0.5Na0.5TiO3)-0.065(BaTi0.99Nb0.01O3)]-x(NaTaO3) (x = 0–0.04) is proposed, providing a roadmap for engineering high-performance piezoelectric ceramics with enhanced electrostrain responses, which may find potential applications as piezoelectric actuators.

Planar array antenna coupled InGaAs/InAlAs multi-quantum well optical modulator for 60 GHz band millimeter wave signals

A Fe-InP-based planar array antenna-coupled InGaAs/InAlAs multiple quantum well (MQW) optical phase modulator is proposed and demonstrated for radio over fiber (RoF) applications with 60 GHz-band millimeter-wave wireless signals. The modulator comprises five types of five-layer asymmetric coupled quantum wells (FACQWs) and a two-element array antenna. The FACQWs are designed to have a significant electric-field-induced refractive index change with small electric fields induced in the antenna. In the fabricated modulator, a carrier-to-sideband ratio (CSR) of up to 45.9 dB was successfully obtained at a power density of 11 W/m2, corresponding to a phase shift of 10.1 mrad. Furthermore, data transmission of a 2 GHz modulated wave with a 60 GHz wireless carrier wave was demonstrated.

Enhanced electric field-induced strain performance in 0–3 composite ceramics by strain and polarization coupling

Inferior electric field-induced strain and large hysteresis in the high-temperature (1-x)BiFeO3-xBaTiO3-based piezoceramics under low driving electric field, which restricts their practical applications, are dramatically technical bottlenecks. Herein, we successfully prepare the 0–3 type composite piezoceramics with super strain properties under a small electric field. Electric field-induced strain and normalized strain coefficient in the 0–3 composite piezoceramics have been severally increased by 161% and 215% than those of non-composite piezoceramics, and the hysteresis and remnant strain in the 0–3 composite piezoceramics have been decreased by 230% and 165% compared with non-composite piezoceramics. Superior electric field-induced strain properties originate from strain and polarization couple, promoting domain switching at low driving electric field, and the novel strategy will accelerate the development and practical applications of lead-free piezoelectric ceramics.

Electric field-induced clustering in nanocomposite films of highly polarizable inclusions

A nanocomposite film containing highly polarizable inclusions in a fluid background is explored when an external electric field is applied perpendicular to the planar film. For small electric fields, the induced dipole moments of the inclusions are all polarized in field direction, resulting in a mutual repulsion between the inclusions. Here we show that this becomes qualitatively different for high fields: the total system self-organizes into a state which contains both polarizations, parallel and antiparallel to the external field such that a fraction of the inclusions is counter-polarized to the electric field direction. We attribute this unexpected counter-polarization to the presence of neighboring dipoles which are highly polarized and locally revert the direction of the total electric field. Since dipoles with opposite moments are attractive, the system shows a wealth of novel equilibrium structures for varied inclusion density and electric field strength. These include fluids and solids with homogeneous polarizations as well as equilibrium clusters and demixed states with two different polarization signatures. Based on computer simulations of an linearized polarization model, our results can guide the control of nanocomposites for various applications, including sensing external fields, directing light within plasmonic materials, and controlling the functionality of biological membranes.

Electrically and mechanically driven rotation of polar spirals in a relaxor ferroelectric polymer

Topology created by quasi-continuous spatial variations of a local polarization direction represents an exotic state of matter, but field-driven manipulation has been hitherto limited to creation and destruction. Here we report that relatively small electric or mechanical fields can drive the non-volatile rotation of polar spirals in discretized microregions of the relaxor ferroelectric polymer poly(vinylidene fluoride-ran-trifluoroethylene). These polar spirals arise from the asymmetric Coulomb interaction between vertically aligned helical polymer chains, and can be rotated in-plane through various angles with robust retention. Given also that our manipulation of topological order can be detected via infrared absorption, our work suggests a new direction for the application of complex materials.

Asymptotic study of critical wave fronts for parameter-dependent Born–Infeld models: physically predicted behaviors and new phenomena

In this paper, we study some parameter-dependent reaction-diffusion models governed by the Born–Infeld (or Minkowski) operator. In dependence on two parameters , related to the field strength and to the diffusivity, we investigate the limit critical speed for traveling fronts, together with the limit behavior of the associated critical profiles. As the two main results, on the one hand we rigorously show that for arbitrarily large electric fields the critical speed and the critical profile converge to the ones of the linear diffusion problem, agreeing with the well-known physical prediction that, in this case, Born’s law and Maxwell’s law coincide. Such a result is accompanied by a counterpart for arbitrarily small electric fields and a complete analysis for vanishing/large diffusion. On the other hand, we prove the onset of a new and unexpected phenomenon for the singular perturbation problem: the critical speed of propagation does not converge to zero and, for KPP or combustion-type reactions, the limit front profile becomes sharp on one side only. In fact, this latter coincides with the C 1-gluing of a piecewise linear profile having slope equal to 1 when nonconstant, and of a regular inviscid profile propagating at the limit speed. The gluing point and the value of the limit speed are determined explicitly. The outcomes of the whole discussion, based on a careful analysis of the first-order reduction associated with the original equation, show substantial differences and peculiarities of the Born–Infeld operator with respect to linear or saturating diffusions, and are supported by several numerical experiments.

Measurement of low-frequency electric field waveform by Rydberg atom-based sensor

The high polarizability of Rydberg atoms enables the multi-parameters measurement of electromagnetic fields. In this paper, we report on an atomic antenna based on Rydberg atoms in a room temperature vapor cell. The EIT is a destructive interference spectroscopy with a narrow linewidth and can be used to detect small electric fields through Autler-Townes splitting or Stark shifts. In our experiments, we employ cascade-type two-photon excitation electromagnetically induced transparency (EIT) spectroscopy to measure the shift of the Rydberg energy level. We introduce a low-frequency electric field (~kHz frequency) using a built-in electrode technique in the cesium cell. The interaction between the Rydberg atom and electric field induces the Stark shifts, where the amplitude of the electric field is converted into corresponding two-photon detuning by the EIT effect. Furthermore, the amplitude of the low-frequency electric field is converted into an intensity signal of EIT probe beam. Under weak field conditions, it is an approximate linear relationship between EIT transmission signal and input electric field amplitude, enabling measurement of waveform, amplitude, and frequency. We have demonstrated optical measurements of low-frequency electric field using Rydberg atoms. By increasing the power of probe beam and coupling beam, the EIT can increase the response bandwidth from ~MHz to hundreds of MHz. This provides a scalable approach for measuring high-frequency electric fields.