Electric Field Switching Research Articles

A novel inverted T-shaped negative capacitance TFET for label-free biosensing application

The promising candidate for designing a highly sensitive biosensor is the negative capacitance tunneling field effect transistor (NCTFET). In this paper, to enhance the sensitivity and performance of the biosensor, we combined inverted T-shaped structure with NCTFET. We introduce negative capacitance effects by stacking ferroelectric materials on the gate dielectric layer. This paper presents a detailed comparative analysis of the proposed inverted T-shaped-NCTFET and TFET based biosensors for different dielectric constants and charge densities of the nano-cavity between the channel and source region locations of biosensor. Sensitivity has been measured in terms of drain current, on-state current, current switching ratio, electric field, and transconductance sensitivity. To establish a benchmark, the sensitivity of the proposed biosensor is also compared with the published literature in order to determine its effectiveness. It is conferred from the results that our biosensor can be a better alternative for the detection of the various neutral and charged biomolecules. All the device simulations are performed in a TCAD environment using a well-calibrated structure.

Delayed phase switching field and improved capacitive energy storage in Ca2+-modified (Pb,La)(Zr,Sn)O3 antiferroelectric ceramics

Antiferroelectric ceramics have captured great attention on capacitive energy storage because of their giant power density and fast discharge speed, which is highly desirable for high- and pulsed-power devices. Nevertheless, the conflict between breakdown electric field and phase switching field of antiferroelectric ceramics blocks to achieve the optimum energy storage capability. In present letter, Ca2+-modified (Pb0.97La0.02)(Zr0.6Sn0.4)O3 ceramics achieved improved breakdown electric field, delayed phase switching field and multiple phase transition under high electric field simultaneously, giving rise to an ultrahigh recoverable energy density of 10.04 J/cm3 and a high energy storage efficiency of 83.95%. Furthermore, the ceramics also displayed excellent thermal reliability as temperature increased to 150 °C, and superior discharge behavior, characterized by Wdis of 5.17 J/cm3 and t0.9 of 5.18 μs. This work not only demonstrates the promising applications of PbZrO3-based antiferroelectric ceramics in energy storage capacitors, but also supplies an effective route to explore high-performance antiferroelectric materials.

Electric-field driven source of photocarriers for tunable electron spin polarization in InGaAs quantum dots

Electric-field control of spin polarization of electrons during injection into InGaAs quantum dots (QDs) was studied via circularly polarized time-resolved photoluminescence. Electric-field modulation of optical spin polarization in QDs will play a key role in future progress of semiconductor opto-spintronics. The tuning of band potentials by applying external electric fields can not only affect spin-injection efficiencies but also switch dominant spin-injection layers. In this study, we developed a QD-based electric-field-effect optical spin device with two different spin-injection layers, which consisted of a GaAs and GaAs/Al0.15Ga0.85As superlattice (SL) barriers. The bias-voltage modulation of the optical spin polarization in QDs was demonstrated by changing the spin polarization degree of electrons injected from these barriers into the QD via the electric-field switching of the spin-injection layers. This was achieved by exploiting the difference in spin relaxation properties between bulk GaAs and the SL. This proposed structure, which comprised of one luminescent layer and two spin-injection layers, is highly scalable because the modulation range of optical spin polarization can be enhanced by changing the combination of spin-injection layers, as well as the material used and its layer thickness.

Ferroelectric-Tunable Photoresponse in α- In2Se3 Photovoltaic Photodetectors: An Ab Initio Quantum Transport Study

Two-dimensional \ensuremath{\alpha}-${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ has drawn broad attention due to its high photoresponse and unique room-temperature interlocked in-plane and out-of-plane ferroelectricity with an ultralow switching electric field. Here, we investigate the photoresponse in a lateral monolayer (ML) \ensuremath{\alpha}-${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ p-i-n junction by using ab initio quantum transport simulations. The maximum photoresponses of the lateral \ensuremath{\alpha}-${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ p-i-n junction are up to 69.2 and 31.6 mA/W for the ferroelectric wurtzite and zincblende phases (shortly named WZ' and ZB') \ensuremath{\alpha}-${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$, respectively, which are 8--17 times higher than that of the extensively researched graphene photodetector (4 mA/W). Remarkably, the ferroelectric photoresponses, defined as the photoresponse change ratio between the two ferroelectric states, of the lateral ML WZ' and ZB'-${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ photodetectors have average values of 127% and 121% with surprising maximum values of $2\ifmmode\times\else\texttimes\fi{}{10}^{6}\mathrm{%}$ and $1\ifmmode\times\else\texttimes\fi{}{10}^{7}\mathrm{%}$, respectively. The physical mechanism comes from the electron density redistribution altered by the atomic displacements due to the polarization switch, rather than the built-in potential change induced by the surface polarization charges. Such ferroelectric-tunable photoresponses in the \ensuremath{\alpha}-${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ photodetector suggest a potential in the fabrication of future optical detection and storage integrated devices.

Accessible chemical space for metal nitride perovskites.

Building on the extensive exploration of metal oxide and metal halide perovskites, metal nitride perovskites represent a largely unexplored class of materials. We report a multi-tier computational screening of this chemical space. From a pool of 3660 ABN3 compositions covering I-VIII, II-VII, III-VI and IV-V oxidation state combinations, 279 are predicted to be chemically feasible. The ground-state structures of the 25 most promising candidate compositions were explored through enumeration over octahedral tilt systems and global optimisation. We predict 12 dynamically and thermodynamically stable nitride perovskite materials, including YMoN3, YWN3, ZrTaN3, and LaMoN3. These feature significant electric polarisation and low predicted switching electric field, showing similarities with metal oxide perovskites and making them attractive for ferroelectric memory devices.

Nonvolatile electro-mechanical coupling in two-dimensional lattices.

Electro-mechanical coupling is of great interest for applications in sensors, actuators and energy harvesters. While the control of electrical charge by mechanical force has been studied extensively, reverse coupling is rarely explored, especially in two-dimensional (2D) lattices. Herein, we propose a novel mechanism for electro-mechanical coupling that realizes the electric field switching of the dimensions of a 2D lattice in a reversible and nonvolatile fashion, through the mediated strength of interlayer interactions in ferroelectric bilayer systems. Based on first-principles calculations, the validity of this mechanism is demonstrated in a series of real bilayer materials, i.e., MoS2/ReIrGe2S6, Sb/In2Se3 and bilayer In2Se3. The interface differences due to polarization play a crucial role in realizing such nonvolatile electro-mechanical coupling, and the underlying physical origin is discussed. These explored phenomena and insights offer a novel avenue for the highly desired nonvolatile electric field control of mechanical strain.

Lateral electric field switching in thin ferroelectric nematic liquid crystal cells.

This study shows that, in cells with small thicknesses, the permanent polarization in the ferroelectric nematic phase of RM734 is aligned in the direction opposite to the rubbing direction. The electrode configuration induces an in-plane field near one substrate and a normal field near the other substrate. At low voltages, the permanent polarization rotates parallel to the substrate plane when its original orientation is at an angle with the electric field. The rotation occurs over a distance of more than 100 μm, where the applied electric field is very small. At higher voltages, the polarization aligns perpendicularly to the substrates under the influence of the transverse electric field. After removing the voltage, sometimes a slow reorientation of the polarization can be observed, which is ascribed to the slow release of ionic species. The results provide insight into the complex mechanisms that are involved in the switching of ferroelectric nematic liquid crystals.

Cation ordering induced two-dimensional vertical ferroelectricity in tungsten and molybdenum trioxides

Two-dimensional (2D) materials that exhibit vertical polarization might provide ground-breaking device applications, compatible with electric-field switching even in the presence of a surface-depolarizing field. Here, using first-principles calculations, we focus on vertical cationic off-plane displacements in transition metal trioxides ${M\mathrm{O}}_{3}$ $(M=\mathrm{W}, \mathrm{Mo})$, with a configuration similar to ${\mathrm{CrI}}_{3}$-like hexagonal trihalides. We further design a ${\mathrm{WMoO}}_{6}$ monolayer, with W and Mo arranged in an energetically stable honeycomb-checkerboard pattern, showing a net vertical ferroelectric polarization and a wide band gap. Moreover, the structural, electronic, and ferroelectric properties of ${\mathrm{WMoO}}_{6}$ monolayers are found to be significantly strain tunable. Our results put forward a transition metal trioxide monolayer with switchable vertical ferroelectricity, thus broadening the range of 2D functional ferroelectrics.

Effect of Aged Nonlinear Resistive Field Grading Material on Electric Field Distribution of DC Cone Spacer

Nonlinear resistive field grading materials are widely used in the electrical and electronic applications, and are usually researched based on the initial nonlinear conductivity characteristics of synthetic materials. However, the long-term stability of these materials are rarely reported. In this paper, the effects of thermal ageing on nonlinear resistive field grading material and the electric field distribution of DC cone spacers are studied. The 30 wt.% SiC/epoxy micro-composites are prepared and are thermally aged at 180 °C for 1080 h. The infrared spectroscopy, dielectric properties, breakdown strength and nonlinear conductivity are measured, respectively. In addition, a simulation model for a cone spacer is built, and the electric field and power dissipation density are calculated. With the increasing thermal ageing time, the relative permittivity and loss tangent increase, and the breakdown strength decreases. Besides, the nonlinear coefficient of nonlinear conductivity almost increases, and the switching electric field of nonlinear conductivity decreases. Simulation results show that the aged micro-composites can homogenize the electric field in the cone spacer, but the thermal ageing causes the increase in power dissipation density and threatens the safe operation of the cone spacer.

Enhanced switching electric field and breakdown strength of epoxy composites with core‐shell silicon carbide nanoparticles

AbstractSilicon carbide (SiC) is widely used to improve the non‐linear conductivity of non‐linear resistive field grading composite. In this paper, the SiC nanoparticles are modified into core‐shell nanoparticles with silica (SiO2) coating on the surface and are characterised by transmission electron microscopy and X‐ray diffraction, respectively. The 7 wt% SiC@SiO2/epoxy nanocomposite is then prepared, and the pure epoxy and 7 wt% SiC/epoxy nanocomposite are prepared as a contrast. The relative permittivity, thermally stimulated current, conductivity and breakdown strength are studied, respectively. The presence of SiO2 shell around SiC nanoparticles has a great effect on the relative permittivity and trap distribution. The epoxy nanocomposites show non‐linear conductivity characteristics, compared with pure epoxy. The 7 wt% SiC@SiO2/epoxy nanocomposite has higher switching electric field and breakdown strength than the 7 wt% SiC/epoxy nanocomposite, which is helpful for the application of non‐linear resistive field grading composite in higher‐voltage equipment or components.

Controllable volatile-to-nonvolatile memristive switching in single-crystal lead-free double perovskite with ultralow switching electric field

All-inorganic lead-free double perovskite offers a potential material platform for electronic or optoelectronic memory devices owing to its ionic migration-based electrical transport, high photosensitivity, low toxicity, and environmental stability. However, the commonly used polycrystalline perovskite films severely restrict device performance. Herein, we demonstrate a high-performance memristor based on single-crystal double perovskite Cs2AgBiBr6 with an ultralow switching electric field of 6.67 × 104 V m−1 and a high current on/off ratio of 107. Remarkably, the resistive switching of Cs2AgBiBr6 is found to be thickness-dependent, which evolves from volatile threshold to nonvolatile resistance switching with the crystal thickness from 100 to 800 nm. Elemental analysis reveals that the formation of conductive channels in Cs2AgBiBr6 is associated with the migration of Br vacancies with low activation energy. In addition, the formed conductive channels can be annihilated by light illumination with controlled wavelength and intensity, which leads to the realization of optoelectronic memories with separate electrical-writing and optical-erasing processes. Our findings provide deep insights into the ionic migration in single-crystal perovskite and pave the way for its future application in electronic and optoelectronic memory devices.

An enhanced high frequency performance SiC MOSFET with self-adjusting P-shield region potential

An enhanced high frequency (HF) performance SiC metal oxide semiconductor field effect transistor (MOSFET) with self-adjusting P-shield region potential (SA-MOS) is proposed and characterized in this paper. The potential of P-shield region (ground or floating potential) can be adjusted by a depletion P-channel metal oxide semiconductor field effect transistor (PMOS) structure integrated in the SA-MOS. During turn-on of SA-MOS, the channel of integrated PMOS is pinched off and the P-shield region can be at a floating potential. Therefore, SA-MOS shows about 21% specific on-resistance (R on,sp) reduction as compared to the conventional trench gate SiC MOSFET with grounded P-shield (GP-MOS) due to the retraction of depletion layer in drift region. During turn-off of SA-MOS, the integrated PMOS is turned on and the P-shield region is grounded to the source contact. Thus, the high on-state oxide electric field and slower switching speed caused by the floating P-shield region could be eliminated by SA-MOS structure. Furthermore, the gate-to-drain charge (Q gd) of SA-MOS is only 217 nC cm−2 owing to smaller overlap area between drift region and trench gate, which is about 40% lower than that of GP-MOS. The HF figures of merit (HF-FOM= R on,sp × Q gd) for SA-MOS can be as low as 50% or more of GP-MOS. Finally, an analytical model is also developed to describe the variation of P-shield potential in SA-MOS. With the overall improved performance, SA-MOS shows a significant advantage in HF field in comparison with the GP-MOS.

Toward Room-Temperature Electrical Control of Magnetic Order in Multiferroic van der Waals Materials.

Electrical control of magnetic order in van der Waals (vdW) two-dimensional (2D) systems is appealing for high-efficiency and low-dissipation nanospintronic devices. For realistic applications, a vdW 2D material with ferromagnetic (FM) and ferroelectric (FE) orders coexisting and strongly coupling at room temperature is urgently needed. Here we present a potential candidate for nonvolatile electric-field control of magnetic orders at room temperature. Using first-principles calculations, we predict the coexistence of room-temperature FM and FE orders in a 2D transition metal carbide, where the spatial distribution of magnetic moments strongly couples with the orientation of out-of-plane electric polarization. Furthermore, an electric-field switching between interfacial FM and ferrimagnetic orders is realizable through constructing a multiferroic vdW heterostructure based on this material. These findings make a significant step toward realizing room-temperature multiferroicity and strong magnetoelectric coupling in 2D materials.

Generating nonlinear conductive characteristics of micro-silicon carbide/silicone elastomer composites at high temperature utilizing nano-AlN fillers

Due to the micro-silicon carbide/silicone elastomer (m-SiC/SE) composite above the percolation threshold loses its nonlinear conductive characteristics at high temperatures, it is unsuitable for high temperature applications. This paper reports the influence of the nano-AlN (n-AlN) fillers on nonlinear conductive characteristics of m-SiC/SE composites at high temperatures. It is found that the addition of the n-AlN fillers in m-SiC/SE composites achieves a stable nonlinear conductivity without a saturation trend up to 250 °C due to the anchoring and bridging effect of the n-AlN fillers, whereas the heterogenous m-SiC/n-AlN interface barrier decreases the conductivity at low fields and enhances the switching electric field, making it suitable for promising high temperature applications.

Field-induced heterophase state in PbZrO3 thin films

Applications of epitaxial antiferroelectrics face scientific challenges, such as limited understanding of degraded (in comparison to bulk) switching behavior and its relation to nanoscale structural organization. We report on an unusual structural response of ${\mathrm{PbZrO}}_{3}/{\mathrm{SrRuO}}_{3}/{\mathrm{SrTiO}}_{3}$ (001) heterostructures to precritical (lower than required for switching) electric fields. In situ x-ray diffraction shows a ferrielectric-like structure, which forms gradually upon increasing the applied field and makes up a heterophase state with the host antiferroelectric phase. The field-induced structure is similar to the antiferroelectric parent phase in the octahedral-tilt pattern, but differs from it in the lead-ion displacement pattern. The latter can be encoded as $\ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\uparrow}\phantom{\rule{4pt}{0ex}}\ensuremath{\downarrow}\ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\downarrow}$ provided that the antiferroelectric structure is encoded as $\ensuremath{\downarrow}\ensuremath{\downarrow}\ensuremath{\uparrow}\ensuremath{\uparrow}$. We propose that the unusual commensurateness (as opposed to the more ubiquitous incommensuration in similar materials) between the modulation periods of host and guest phases can be explained by accounting for the energy of heterophase boundaries, which is important in dense nanostructures due to the high surface-to-bulk ratio of nanodomains. An analysis using the ab-initio-correlated, but empirical (parametrized) energy model suggests that the observed field-induced structure is likely to be selected in ${\mathrm{PbZrO}}_{3}$ instead of the others in the case when the above commensuration effect is at play. The results point to the mechanism leading to the smearing of polarization-field loops in such heterostructures and suggest a perspective for the controlled creation of delicate dipolar orderings for ferroic-based memory.

Robust Piezoelectric Coefficient Recovery by Nano-Inclusions Dispersion in Un-Poled PVDF–Ni0.5Zn0.5Fe2O4 Ultra-Thin Films

This work aimed to study the influence of the hybrid interface in polyvinylidene fluoride (PVDF)-based composite thin films on the local piezoelectric response. Our results provide evidence of a surprising contradiction: the optimization process of the β-phase content using nano-inclusions did not correspond to the expected nanoscale piezoelectric optimization. A large piezoelectric loss was observed at the nanoscale level, which contrasts with the macroscopic polarization measurement observations. Our main goal was to show that the dispersion of metallic ferromagnetic nano-inclusions inside the PVDF films allows for the partial recovery of the local piezoelectric properties. From a dielectric point of view, it is not trivial to expect that keeping the same amount of the metallic volume inside the dielectric PVDF matrix would bring a better piezoelectric response by simply dispersing this phase. On the local resonance measured by PFM, this should be the worst due to the homogeneous distribution of the nano-inclusions. Both neat PVDF films and hybrid ones (0.5% in wt of nanoparticles included into the polymer matrix) showed, as-deposited (un-poled), a similar β-phase content. Although the piezoelectric coefficient in the case of the hybrid films was one order of magnitude lower than that for the neat PVDF films, the robustness of the polarized areas was reported 24 h after the polarization process and after several images scanning. We thus succeeded in demonstrating that un-poled polymer thin films can show the same piezoelectric coefficient as the poled one (i.e., 10 pm/V). In addition, low electric field switching (50 MV/m) was used here compared to the typical values reported in the literature (100–150 MV/m).

Bipolar Electric-Field Switching of Perpendicular Magnetic Tunnel Junctions through Voltage-Controlled Exchange Coupling.

Perpendicular magnetic tunnel junctions (p-MTJs) switched utilizing bipolar electric fields have extensive applications in energy-efficient memory and logic devices. Voltage-controlled magnetic anisotropy linearly lowers the energy barrier of the ferromagnetic layer via the electric field effect and efficiently switches p-MTJs only with a unipolar behavior. Here, we demonstrate a bipolar electric field effect switching of 100 nm p-MTJs with a synthetic antiferromagnetic free layer through voltage-controlled exchange coupling (VCEC). The switching current density, ∼1.1 × 105 A/cm2, is 1 order of magnitude lower than that of the best-reported spin-transfer torque devices. Theoretical results suggest that the electric field induces a ferromagnetic-antiferromagnetic exchange coupling transition of the synthetic antiferromagnetic free layer and generates a fieldlike interlayer exchange coupling torque, which causes the bidirectional magnetization switching of p-MTJs. These results could eliminate the major obstacle in the development of spin memory devices beyond their embedded applications.

Low-filled suspensions of α-chitin nanorods for electrorheological applications

Highly anisometric α-chitin nanoparticles isolated by TEMPO-oxidation were investigated as filler for electrorheological fluids. The dimensions of rod-like particles were determined by AFM and cryo-TEM methods. The rheological behavior of α-chitin nanoparticles in polydimethylsiloxane changes from viscous to elastic under electric field. The yield stress reaches about 220 Pa at 7 kV/mm for 1.0 wt% fluid. Despite the nanosize of particles, the suspensions sedimentation ratio was found to be low (~23%). The electrorheological behavior of the fluids was discussed in terms of the Mason numbers. The stability of fluids response under switching electric field was shown. The activation energy of polarization processes in suspensions was calculated as 58 ± 2 and 64 ± 1 kJ/mol for 0.5 and 1.0 wt% filler content from the impedance spectra. The high aspect ratio (~70) and dielectric permittivity result in high electrorheological activity of α-chitin suspensions at extremely low concentrations (≤1.0 wt%).

Influence of temperature on electromechanical responses of PZT-5H and output energy under shock loading

Ferroelectric ceramics are of interest for engineering applications because of their electromechanical coupling and the unique ability to permanently alter their atomic-level dipole structure (i.e., their polarization) and to induce large-strain actuation through applied electric fields. Although the electrical output properties of the material at different strain rates have been studied by quasi-static and dynamic loading, most prior work has ignored the important influence of temperature on the ferroelectric behavior. Here, the experiments of impacting on PZT have been performed at the same loading conditions, different environmental temperatures (−40 °C, −25 °C, 0 °C and 25 °C) and circuit connection modes. The domain switching analyses have been conducted at the different temperatures. The results show that the electromechanical coupling coefficient increases linearly, and the energy barrier across the domain switching and coercive electric field increase with the decrease of temperature, but the piezoelectric coupling behavior was weaken and the residual polarization strength was reduced. Under electrical short-circuit, the energy density of the discharge accounts for about 1‰ of the irrecoverable energy density.

Structural, Magnetic, and Electric Properties of Pt/Co/Au/Cr<sub>2</sub>O<sub>3</sub>/Pt Thin Film with Cr<sub>2</sub>O<sub>3</sub> Layer below 25 nm

Perpendicular exchange bias using magnetoelectric Cr2O3 has an electric-field triggered switching ability, and the thickness limit of the Cr2O3 layer for inducing this bias is a topic of research. In this paper, we investigated the structural, magnetic, and electric properties of Pt/Co/Au/Cr2O3/Pt thin films with a Cr2O3 layer in the thickness range of 5.7 to 25 nm. By using a magnetron sputtering method, a well-crystallized Cr2O3(0001) layer was formed in 5.7-nm-thick Cr2O3. All studied films showed perpendicular magnetic anisotropy. The uniaxial magnetic anisotropy energy density increased as the Cr2O3 thickness decreased, and 810±90 kJ/m3 was obtained for the film with 5.7-nm-thick Cr2O3. Perpendicular exchange bias was evaluated above 80 K, and an exchange anisotropy energy density of 0.30 mJ/m2 was observed for the film with a 25-nm-thick Cr2O3 at 80 K. The exchange bias could not be observed below 18 nm. Instead, coercivity enhancement, which yields the exchange bias by precisely controlling interfacial exchange coupling, was observed. The electric resistivity was about 5 × 105 Ωm for the 5.7-nm-thick Cr2O3 layer, which is sufficiently high for magnetoelectric applications.