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Strong changes in bulk properties, such as modulus and viscosity, are observed near the glass transition temperature, Tg, of amorphous materials. For more than a century, intense efforts have been made to define a microscopic origin for these macroscopic changes in properties. Using transition state theory (TST), we delve into the atomic/molecular level picture of how microscopic localized unit relaxations, or "cage rattles," evolve to macroscopic structural relaxations above Tg. Unit motion is broken down into two populations: (1) simultaneous rearrangement occurs among a critical number of units, nα, which ranges from 1 to 4, allowing a systematic classification of glass formers, GFs, that is compared to fragility; and (2) near Tg, adjacent units provide additional free volume for rearrangement, not simultaneously, but within the "primitive" lifetime, τ1, of one unit rattling in its cage. Relaxation maps illustrate how Johari–Goldstein β-relaxations stem from the rattle of nα units. We analyzed a wide variety of glassy materials and materials with a glassy response using literature data. Our four-parameter equation fits "strong" and "weak" GFs over the entire range of temperatures and also extends to other glassy systems, such as ion-transporting polymers and ferroelectric relaxors. The role of activation entropy in boosting preexponential factors to high "unphysical" apparent frequencies is discussed. Enthalpy–entropy compensation is clearly illustrated using the TST approach. [ABSTRACT FROM AUTHOR]

The solid-state refrigeration technique based on the electrocaloric effect (ECE) of ferroelectric materials has been regarded as a promising alternative to vapor compression systems due to its advantages of high efficiency and easy miniaturization. However, the small adiabatic temperature change (ATC) and narrow operating temperature range of ferroelectric materials are key obstacles for their practical applications of ECE refrigeration. To improve the ECE performance of ferroelectric polymer poly(vinylidene fluoride) [P(VDF-TrFE)], PbZr1−xTixO3 (PZT) nanoparticles with larger polarization is herein introduced to form ferroelectric nanocomposites. The phase-field simulation is employed to investigate the dynamic hysteresis loops and corresponding domain evolution of the ferroelectric nanocomposites. The temperature-dependent ATC values are calculated using the indirect method based on the Maxwell relation. The appearance of the double hysteresis loop is observed in P(VDF-TrFE) nanocomposite filled with PbZr0.1Ti0.9O3 nanoparticles [P(VDF-TrFE)–PZT0.9], which is mainly caused by a microscopic domain transition from single domain to polar vortex. Compared to the P(VDF-TrFE), enhanced ATC values associated with the domain transition are unveiled in P(VDF-TrFE)–PZT0.9, and the temperature range of excellent ECE is also effectively broadened. In addition, as the component x of filled PZT nanoparticles increases to cross the morphotropic phase boundary (MPB), the maximum ATC value shows a significant increase. The results presented in this work not only explain the mechanism of domain transition induced excellent ECE in the P(VDF-TrFE)–PZT nanocomposite, but also stimulate future studies on enhancing ECE of P(VDF-TrFE) by introducing ferroelectric nanofillers. [ABSTRACT FROM AUTHOR]

As typical representatives of group III chalcogenides, InSe, α-In2Se3, and β′-In2Se3 have drawn considerable interest in the domain of photoelectrochemistry. However, the microscopic mechanisms of carrier dynamics in these systems remain largely unexplored. In this work, we first reveal that hot electrons in the three systems have different cooling rate stages and long-lived hot electrons, through the utilization of density functional theory calculations and nonadiabatic molecular dynamics simulations. Furthermore, the ferroelectric polarization of α-In2Se3 weakens the nonadiabatic coupling of the nonradioactive recombination, successfully competing with the narrow bandgap and slow dephasing process, and achieving both high optical absorption efficiency and long carrier lifetime. In addition, we demonstrate that the ferroelectric polarization of α-In2Se3 not only enables the formation of the double type-II band alignment in the InSe/α-In2Se3/InSe heterostructure, with the top and bottom InSe sublayers acting as acceptors and donors, respectively, but also eliminates the hindrance of the built-in electric field at the interface, facilitating an ultrafast interlayer carrier transfer in the heterojunction. This work establishes an atomic mechanism of carrier dynamics in InSe, α-In2Se3, and β′-In2Se3 and the regulatory role of the ferroelectric polarization on the charge carrier dynamics, providing a guideline for the design of photoelectronic materials. [ABSTRACT FROM AUTHOR]

Hexagonal manganites can exhibit the low-symmetry ferroelectric (FE) P63cm and partially undistorted anti-ferroelectric (PUA) P-3c1 states. The two states are accompanied by distinct sixfold vortex domain structures. The transition from the FE P63cm and PUA P-3c1 states (FE-PUA transition) is an effective means to control domain structures with distinct FE properties, which is of rich physical properties and potential applications. The FE-PUA transition can only be achieved by doping Ga on the Mn site of InMnO3, but the actual transition path and the associated domain structure evolution are still unclear. Namely, whether this transition goes through an intermediate P3c1 state remains an issue. In this work, we start from the Landau phenomenological theory to investigate the FE-PUA transition by directly tracking the domain structure evolution. The emerging 12-fold vortex domain structure at the intermediate stage of this transition indicates that this transition is not direct, and its actual path follows the P63cm → P3c1 → P-3c1 sequence, demonstrating the essential role of the intermediate P3c1 state. Besides, a pinning effect as a by-product is also discussed. This work comprehensively illustrates the characteristics of domain structure evolution during the FE-PUA transition, refining our understanding of the whole phase transition and topological physics associated with vortex domain structures in hexagonal manganites. [ABSTRACT FROM AUTHOR]

The domain reversal dynamics of the pristine and 10 wt. % BiFeO3 nanoparticle-embedded P(VDF-TrFE) (polyvinylidene fluoride-trifluoroethylene) flexible ferroelectric membranes were investigated. A scaling relation of A∝fαE0β relevant to the domain reversal dynamics was eventually determined. The pristine P(VDF-TrFE) flexible membrane takes the form of A∝f0.04077E00.39748 in stage III of high electric fields. Nevertheless, for BiFeO3-embedded P(VDF-TrFE) [BFO/P(VDF-TrFE)] flexible membranes, the relations are developed as A∝f−0.3326E02.74911 in the low electric fields of stage I and as A∝f0.04309E01.04872 in stage III separately. The negative α indicates that more and more domain reversal lags behind the alternating periodic electric field in stage I. Instead, in stage III, the positive α indicates that most domain reversals can occur anytime whatever the alternating speed of electric fields is. Analogously, the positive β indicates that at any selected frequency, domains can flip at an external electric field. Abnormally, for the pristine P(VDF-TrFE) membrane, the scaling relation in the first E0 stage is broken, reflecting only dielectric contributions this time. The dynamic scaling data are significant for the micromechanism accomplishments of copolymers and for the designs of flexible electric devices. [ABSTRACT FROM AUTHOR]

The increasing demand of information and communication technology has pushed conventional computing paradigm to its limit. In addition, physical and technological factors have constrained the advancement of conventional memory devices. Considering the rapid back-and-forth transfer of a large amount of information, emerging memory should demonstrate space efficiency, fast speed, and low-cost requirements. Accordingly, ferroelectric films based on HfO x are being intensively researched owing to their high energy efficiency and compatibility with complementary metal oxide semiconductor. Particularly, owing to the simplicity of their structure, low power, and less variation, hafnia-based ferroelectric tunnel junctions (FTJs) stand out among ferroelectric memories. Numerous studies have demonstrated the improved ferroelectricity of FTJs using various engineering methods, including doping, annealing, and varying electrodes. To improve the properties of HfO x -based FTJs and enhance their applications, it is necessary to organize and discuss recent studies and prospects. Therefore, this paper reviews in-depth and comprehensive studies on FTJs and their advantages compared to other emerging devices. Additionally, in-memory computing applications, outlook, and challenges of hafnia-based FTJs are presented. [ABSTRACT FROM AUTHOR]

Polymer-based ferroelectric composites, particularly those containing Poly (vinylidene fluoride) (PVDF), have emerged as preferred materials for flexible electronics and sensors owing to their excellent electro-mechanical attributes and ease of fabrication. The efficacy of PVDF composites is significantly influenced by the fillers and the proportion of the β-phase present. This research details the synthesis of La 0.7 Ba 0.3 MnO 3 (LBMO) particles via solid-state reaction, surface-functionalized with acetic acid, and subsequently introduced as nucleating agents into Poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) to fabricate LBMO/P(VDF-HFP) composite membranes. The LBMO fillers before modification significantly increased the β-phase content from 32.7 % to 87.8 % in 5 wt% unmodified LBMO/P(VDF-HFP) membranes. After modification, the hydroxyl groups attached to acetic acid-modified LBMO form hydrogen bonds with -CF 2 groups in P(VDF-HFP), inducing the formation of the β phase while enhancing macroscopic polarization and piezoelectricity. At a 7.5 wt% acetate-modified LBMO doping level, the composite membrane exhibits a β-phase content of 64.5 %, but concurrently enhancing the film's dielectric properties. At 103 Hz, the dielectric constant of 5 wt% modified LBMO/P(VDF-HFP) membrane increases to 24.8, with a minimal rise in dielectric loss from 0.0293 to 0.0314. Moreover, under a 10 N compressive load at 1 Hz, the 5 wt% modified LBMO/P(VDF-HFP) composite achieves an open-circuit voltage of 4.3 V. These improved dielectric and piezoelectric properties indicate the composite's suitability for energy harvesting applications. [ABSTRACT FROM AUTHOR]

Electrocaloric (EC) cooling presents a promising approach to efficient and compact solid-state heat pumps. However, reported EC coolers have complex architectures and limited cooling temperature lift. In this work, we introduce a self-regenerative heat pump (SRHP) using a cascade of EC polymer film stacks, which have electrostrictive actuations in response to an electric field that are directed to realize efficient heat transfer, eliminating the need for additional transportive or regenerative mechanisms. The SRHP demonstrates a cooling of 8.8 kelvin below ambient temperature in 30 seconds and delivers a maximum specific cooling power of 1.52 watts per gram. The temperature lift of the SRHP is 14.2 kelvin. These results underscore the potential of the compact solid-state cooling mechanism to address the increasing need for localized thermal management. [ABSTRACT FROM AUTHOR]

An innovative approach has been adopted through the synthesis of a cost‐effective ferroelectric host polymer, which was integrated with Barium Titanate (BaTiO3) to develop an efficient electrospun Polyvinylidene Fluoride‐Hexafluoropropylene/BaTiO3 (PVdF‐HFP/BaTiO3) nanocomposite (PBT), designated for energy harvesting and piezocatalytic applications. FT‐IR affirmed the existence of the crystalline β‐phase within the nanofibers. SEM images showed that nanofiber diameter decreases as applied voltage is increased in electrospinning. The BaTiO3 nanoparticles were scattered evenly in PBT, but at lower voltages, they aggregate. PBT showed enhanced piezoelectric performance under higher voltage conditions, registering a maximum piezoelectric output of ~7.7 V and an output current of 0.77 μA. Moreover, the composite exhibited a power density of 14.15 mW/m2 at a load resistance of 20 MΩ. Fabricated piezoelectric nanogenerator (PENG) demonstrated practical utility in flexible electronics, notably in charging capacitors of 0.47 μF and 1 μF. Additionally, the piezocatalytic degradation of the antibiotic ciprofloxacin (CIP) was effectively achieved using the electrospun nanofibers, with an impressive degradation rate of up to 99.6 % within 30 minutes under acidic conditions, and the material displayed notable reusability, maintaining up to 95.5 % efficiency after five cycles. DFT calculations and COMSOL simulations alongside a comparative examination of the electronic properties of PBT. [ABSTRACT FROM AUTHOR]

Shape memory polymers (SMPs) have been extensively investigated because of their wide range of biomedical and robot applications. In most of SMPs, only one temporary shape can be formed and recovered through the mechanism of melting or glass transition. Herein, a multiple shape memory effect (mSME), i.e., formation of at least two temporary shapes, can be realized in polyvinylidene fluoride (PVDF)‐based ferroelectric polymers by exploiting their expanded ferroelectric–paraelectric (F‐P) phase transition temperature range. Although P(VDF‐TrFE) (TrFE: trifluoroethylene) (55/45) copolymer is thought to be a normal ferroelectric, its ferroelectric phase transforms into a paraelectric phase through an intermediate relaxor ferroelectric‐like state and mSME is observed in this extended phase transition temperature range. By incorporating CTFE (chlorotrifluoroethylene) into P(VDF‐TrFE), P(VDF‐TrFE‐CTFE) becomes a relaxor ferroelectric with a further extended phase transition temperature range. The terpolymer exhibits improved mSME and at least three temporary shapes can be formed and recovered. A comparison of SME and structures of several PVDF‐based copolymer and terpolymers suggests that the amount of polar phase is a critical factor affecting the SME. This study not only demonstrates mSME in ferroelectric polymers, which expands their application potential, but also provides an in‐depth understanding of the shape memory mechanism of the polymers. [ABSTRACT FROM AUTHOR]

Polymer‐based pyroelectric thin films are crucial functional materials at the core of flexible and lightweight electronic devices, such as wearable monitoring sensors, energy harvesters, and infrared detectors. Nevertheless, the pyroelectric properties of the polymer films, such as poly(vinylidene fluoride‐trifluoroethylene) (P(VDF‐TrFE)), vanish when the surrounding temperature exceeds the ferroelectric‐to‐paraelectric transition temperature, and thus limits their pyroelectric performance to a low‐temperature range. Herein, to mitigate this issue by employing a new class of P(VDF‐TrFE) copolymer which has a low TrFE molar content is proposed. Fine‐tuning of the structure through thermal annealing in a vacuum environment significantly favors robust and highly polarized polymer films with a large area. Electric poling combined with an optimal annealing temperature (110–120 °C) gives highly ordered ferroelectric crystalline domains in the polymer films. Consequently, this remarkably broadens the temperature range (roughly up to 140 °C) for which the polymer film still presents high pyroelectric properties (pyroelectric coefficient 50 µC (m2K)−1). This study provides an alternative choice for pyroelectric polymer films with enhanced pyroelectricity in applications that require wider temperature ranges. [ABSTRACT FROM AUTHOR]

Soft molecule‐based ferroelectrics with unique structural flexibility hold a promise for versatile applications of non‐volatile memory, imaging and photovoltaic devices. Except for few polymers (e.g., polyvinylidene fluoride, PVDF), it is challenging to exploit soft ferroelectric crystals toward free‐standing flexible photoactive devices. We here report a multiaxial soft molecule‐based ferroelectric, (n‐PA)2PbCl4 (1, where n‐PA+ is n‐pentylammonium), of which spontaneous polarization can be reversibly switched in both crystal and powder forms. Strikingly, single crystals of 1 have unusual structural flexibility and bendability, achieving the self‐standing bending with a bending radius of ~0.22 mm. Besides, the pyroelectric activities are also preserved for these single crystals after several bending cycles. Further, the bendable crystal‐based photodetector of 1 allows broadband photoactivities via the photo‐pyroelectric effect, covering a wide range from 405 to 940 nm spectral region, breaking through the limit of optical absorption bandgap. As the first study of bendable free‐standing photo‐pyroelectric detectors in ferroelectric crystals, our work sheds light on the assembly of flexible smart photoelectric devices. [ABSTRACT FROM AUTHOR]

Dielectric polymers are essential to capacitive capacitors widely used in modern electronic and electrical systems. Most useful dielectric polymers are derived from petroleum while environmentally sustainable dielectric biomass remains mostly unexplored although they are abundant, renewable, and cost‐effective. Here an ultrahigh energy density in cyanoethyl cellulose (CEC) and cyanoethyl pullulan (CEP) obtained by replacing the hydroxyl groups of cellulose and pullulan with cyanoethyl is reported. Large dielectric constants of 16.7 and 20.0 in CEC and CEP due to the strong polarity of cyanoethyl which are comparable to high‐dielectric ferroelectric polymers are shown. CEC and CEP show nearly no degradation of the dielectric constant with increasing electric fields, inhabiting the early polarization saturation and thus leading to improved energy density, which is different from relaxor ferroelectric polymers. Consequently, solution‐processable CEP films exhibit an ultrahigh discharged energy density of 28.2 J cm−3 with an efficiency of 72% at 600 MV m−1, outperforming other all‐organic dielectric biomass materials. The work paves the way for the development of high‐performance dielectric biomass for energy storage applications. [ABSTRACT FROM AUTHOR]

The film photocatalyst is easily recycled and has attracted the widely research interesting. Here the ferroelectric Hf 0.5 Zr 0 · 5 O 2 (HZO) thin film synthesized through the atomic layer deposition (ALD) method is used as a photocatalyst for the rhodamine B (RhB) dye decomposition under visible light irradiation. The photocatalytic RhB dye decomposition performances with or without an external magnetic field excitation provided by a commercial NdFeB magnet are experimentally characterized. With the increasing of the external direct-current (DC) magnetic field from 0 to 3000 Gs, the photocatalytic RhB dye decomposition ratio by HZO film obviously increases from 87.20 % to 98.17 %, which is attributed to the enhanced separation of the photo-induced positive and negative carrier due to the magnetic Lorentz effect. The magnetically-induced enhancement of photocatalysis in the ferroelectric HZO film, provides a method with these advantages of simple external excitation method, remarkable promotion effect and friendly-environment to enhance the dye decomposition ratio, and is potential in the practical application of photocatalytic dye wastewater treatment through harvesting the clean solar energy in future. [ABSTRACT FROM AUTHOR]

Ferroelectric polymer-based separators, known for their flexibility, ease of synthesis, and modifiability through dopants, are currently under extensive study due its potential applications in electronic devices. PVDF nanocomposites, which combine the strengths of their constituents, currently lead in emerging technologies. This research employs Zinc oxide nanoparticles (ZnO NPs) as fillers in the PVDF matrix and investigates their structural, optical, thermal and electrical properties. ZnO NPs synthesized via the combustion method, are being incorporated with varying concentrations (2, 4, 6, 8, and 10 wt%), into PVDF nanocomposite (PNC) thin films through a solution casting process. The PNC thin films are characterized using XRD, FTIR, UV–Vis spectroscopy and thermogravimetric analysis (TGA). Dielectric properties are being explored across a frequency range from 20 to 2 MHz at room temperature, revealing enhanced dielectric constants at lower frequencies, decreasing with frequency due to Maxwell–Wagner interfacial polarization. With increasing frequency, AC conductivity and electric modulus exhibit enhancement. Complex impedance analysis via the Cole–Cole plot indicates a non-Debye type of dielectric relaxation with heightened conductivity. TGA demonstrates improved thermal stability in PNC thin films. These findings suggest the potential application of the prepared PNC thin films as separators in energy storage devices. [ABSTRACT FROM AUTHOR]

For ferroelectric (FE) thin films, working in the harsh environment of a high electric field (E) or high temperature (T) remains a great challenge. As a post-treatment approach, dead-layer engineering exhibits a certain generality and could improve the dielectric strength (Eb) via depositing a specially designed artificial "dead-layer" on most of the as-prepared FE thin films. However, physical essence of the artificial dead-layer needs further analysis. Great challenges are the abundant and complicated conduction mechanisms in the FE-based thin films and the lack of adequate research on modulating these conduction mechanisms by this artificial dead-layer. As a vital part of the conduction mechanisms, electron injection can be easily triggered under E and thermal excitation that almost appeared in all FE-based thin films. Here, the ultrathin artificial dead-layer of Ca0.2Zr0.8O1.8 (CSZ) was used to restrain multiple electron injection in low-Eb LaNiO3/Ba0.58Sr0.42TiO3 (LNO/BST) FE thin films, including thermal emission and tunneling effect, under a high E and T, even under an opposite E. It was found that the suppressing effect on the multiple electron-injection mechanisms via the artificial dead-layer mainly comes from its wall-like energy-barrier structure, which is composed of two opposite and high interface energy barriers (BST/CSZ: 2.95 eV, CSZ/Au: 3.92 eV) and a wide depletion layer. The generality of protecting the ferroelectric thin films from electron injection via the artificial dead-layer was discussed. [ABSTRACT FROM AUTHOR]

Recently, a number of two-dimensional van der Waals (vdW) ferroelectrics have been reported, showing the potential to develop various ultra-thin smart devices down to the atomic monolayer limit. In particular, they have been demonstrated to exhibit intriguing polar domain structures. However, phenomenological thermodynamic models of vdW ferroelectrics, which can capture their ferroic domain structure evolution, are still lacking, limiting our further exploration of domain-structure-related applications. In this work, combining first-principles calculations, we construct a phenomenological phase field model for monolayer ferroelectrics, FEβ-In2Se3. Based on the model, one can calculate the phase stability, ferroelectric hysteresis curves, and domain structures of FEβ-In2Se3 under different loading conditions, showing the feasibility of electromechanically driving the rotation of in-plane polarization and manipulation of the domain structures. By including the second-order partial derivative gradient energy term, the model further captures well the antiferroelectric–ferroelastic domain structures of β′-In2Se3 observed in previous experiments. The developed phase field model should help better understand the domain structure evolution behavior in low-dimensional materials and promote further exploration of domain-structure-related applications. [ABSTRACT FROM AUTHOR]

Recently, a number of two-dimensional van der Waals (vdW) ferroelectrics have been reported, showing the potential to develop various ultra-thin smart devices down to the atomic monolayer limit. In particular, they have been demonstrated to exhibit intriguing polar domain structures. However, phenomenological thermodynamic models of vdW ferroelectrics, which can capture their ferroic domain structure evolution, are still lacking, limiting our further exploration of domain-structure-related applications. In this work, combining first-principles calculations, we construct a phenomenological phase field model for monolayer ferroelectrics, FEβ-In2Se3. Based on the model, one can calculate the phase stability, ferroelectric hysteresis curves, and domain structures of FEβ-In2Se3 under different loading conditions, showing the feasibility of electromechanically driving the rotation of in-plane polarization and manipulation of the domain structures. By including the second-order partial derivative gradient energy term, the model further captures well the antiferroelectric–ferroelastic domain structures of β′-In2Se3 observed in previous experiments. The developed phase field model should help better understand the domain structure evolution behavior in low-dimensional materials and promote further exploration of domain-structure-related applications. [ABSTRACT FROM AUTHOR]

In modern electronics and power systems, good-performance dielectric capacitors have an essential function. Polymer-based dielectrics are widely used in the field of dielectric capacitors because of their large dielectric constant, flexibility, low density, and ease of processing. At present, ferroelectric polymers suffer from low breakdown field strength and high dielectric losses. How to improve the performance of dielectric materials in capacitors is still a promising research. This paper chooses the ferroelectric polymer poly(vinylidene fluoride) (PVDF) that worked as the matrix, and the linear polymers polyimide, cyanoethyl pullulan (CR-S), polyethersulfone, and cyanoethylated cellulose served as fillers. This all-organic dielectric composite produced as films working in electrostatic energy storage devices is prepared by using a casting method. Analyzing the test results, the composite film exhibited excellent electrical properties when the CR-S doping content was 5 wt. %. The organic composite dielectric based on CR-S/PVDF has a breakdown field strength of 450 MV/m, a discharge energy storage density (Ue) of 10.3 J/cm3, a high dielectric constant of 10.9, and a low dielectric loss of 0.004 at 1 kHz, which is a significant improvement compared with other dielectric composites. This all-organic dielectric composite strategy offers a new approach to achieve better-performance dielectric energy storage materials. [ABSTRACT FROM AUTHOR]

Adding excessive metal oxide doping to a powder batch is a known way to compensate for the loss of volatile cation species during high temperature sintering. An important case in the piezoelectric ceramics is the bismuth oxide in the lead-free ferroelectric ceramic bismuth sodium titanate (BNT). Building from the earlier knowledge about excessive bismuth oxide's influences on the properties of BNT, we further note that varying the sintering temperature can both control the distribution of excessive Bi3+ and impact the relaxor/normal ferroelectric behaviors and corresponding phase transition. In addition to the nature of polarization, the sintering temperature also significantly manipulates the electrical conductivity. A hypothetical mechanism for the resistive grain boundary is proposed, based on inferences from electrical—microstructure—processing relations in 85% Bi0.5Na0.5TiO3-15% BaTiO3 with batched Bi2O3 excess and acceptor Mg2+ in a co-doped strategy. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the dependence of dynamic hysteresis on the electric field amplitude E0 and the frequency f in organic ferroelectric copolymer polyvinylidene fluoride-trifluoroethylene [P(VDF-TrFE)] thin films prepared by a spin-coating method on fluorine-doped tin oxide conductive glass. Three stages can be observed of the hysteresis area vs the field strength E0. In stage I of low E0 values, the area ⟨ A ⟩ dependent on E0 follows the law of ⟨ A ⟩ ∝ E 0 1.92795 , whereas the diverse distribution of the area ⟨ A ⟩ with frequency f is found. In stage II of the intermediate E0 values, ⟨ A ⟩ ∝ E 0 β is not applicable owing to collective contributions between 180° domain and chiral domain, while a relation of ⟨ A ⟩ ∝ f − 0.18636 can be deduced, a fascinating characteristic distinguishing from the nonlinear relations of the inorganics in this section. In stage III of high E0 values, the scaling law is ⟨ A ⟩ ∝ f 0.08447 E 0 0.49394 where the chiral domain is active. The positive β in the law of ⟨ A ⟩ ∝ f α E 0 β illustrates that a growing number of chiral domains in P(VDF-TrFE) can keep pace with the variation of E0. Especially, the negative α in the transition zone, resembling some inorganics under low electric fields, probably indicates 180° domain reversal failing to follow with the alternating velocity of the increasing periodic electric field. [ABSTRACT FROM AUTHOR]

A straightforward scalable method for synthesizing β-poly (vinylidene fluoride) polymer foam from a sugar template has been used. A characteristic β-phase of the foam was confirmed by infrared and micro-Raman spectroscopy with significant enhancement observed after poling. The electrical polarization of the foam revealed a ferroelectric nature with dielectric strength higher than 30 kV/cm which is close to the commercial value. Poled samples had a dielectric constant of 5.5, higher than the value of the unpoled sample (3.05). These values appear stable over the low-frequency range from 1 kHz to 1 MHz. Significant reverse behavior was observed at higher frequencies from 300 GHz to 3 THz frequencies. It was found that the open-cell foam with a porosity of 88% has the lowest dielectric constant value (1.07 at 1.8 THz, reaching 1.04 at 2.9 THz) compared to the foam with 20% porosity (2.17 at 1 THz, reaching 1.83 at 3 THz). Furthermore, the Maxwell Garnett model, in conjunction with THz imaging, confirmed the impact of porosity on dielectric properties. These findings pave the way for the efficient fabrication of ferroelectric porous polymer structures that can be used in dielectric switching at the kHz–THz frequency range. [ABSTRACT FROM AUTHOR]

They found that metal contacts can facilitate the stabilization of the ferroelectric phase, enabling aggressive scaling of 2D ferroelectrics.[13] As a recently discovered vdW ferroelectric, -In SB 2 sb Se SB 3 sb exhibits inter-correlated in-plane and out-of-plane polarization.[[17]] Unlike traditional ferroelectric materials, which are usually insulators, -In SB 2 sb Se SB 3 sb is a semiconductor with a band gap of 1.36 eV (bulk). In recent years, a range of two-dimensional (2D) layered materials have been experimentally confirmed or theoretically predicted to be piezoelectric, pyroelectric, or ferroelectric.[[1], [3], [5], [7], [9]] Compared to their bulk counterparts, 2D piezoelectric, pyroelectric, and ferroelectric materials exhibit many intriguing properties, such as excellent size scaling, tunable bandgap, negative piezoelectric coefficient, and high mechanical flexibility.[[1], [3], [5], [7], [9]] Furthermore, the stackable nature of 2D layered materials makes them promising building blocks for designing functional heterostructures, where the 2D layers can be integrated with conventional piezoelectric, pyroelectric, and ferroelectric oxides and polymers. Piezoelectric, pyroelectric, and ferroelectric materials have attracted tremendous attention owing to their potential applications in nonvolatile memories, logic devices, photodetectors, sensors, actuators, transducers, and energy harvesting devices. 10.1063/5.0116445 40 X. Hong, A. Posadas, K. Zou, C. H. Ahn, and J. Zhu, "High mobility few layer graphene field effect transistors fabricated on epitaxial ferroelectric gate oxides", Phys. [Extracted from the article]

Using the previously developed model, we study the electrocaloric effect (ECE) in antiferroelectric crystals of squaric acid, where the low-temperature polarization reorientation by the external electric field has been earlier predicted to be a two-stage process with the intermediate ferrielectric phase. The T - E landscape of the model entropy is explored. The ECE, characterized by the electric Grüneisen parameter, is found to be negative in the antiferroelectric phase. In the ferrielectric phase, it is positive at low fields but becomes slightly negative below the transition to the ferroelectric phase. In the ferroelectric phase, the ECE is positive at all temperatures and fields. The negative EC temperature shift Δ T of the largest magnitude is predicted to be around − 2.7 K at 200 kV/cm. The supercritical behavior of the Grüneisen parameter in the crossover region between two bicritical end points is studied. [ABSTRACT FROM AUTHOR]

In two-dimensional valleytronics, the controllability of anomalous valley Hall effect is the key to its practical application. However, most of the previously proposed control methods are volatile or irreversible. Here, using first principles calculations, we demonstrate that the GdF2/Sc2CO2 multiferroic heterojunction can exhibit nonvolatile switching of its electronic band structures. Interestingly, the polarization switching of the ferroelectric monolayer induces movement in the valley polarization band of GdF2, enabling manipulation of the valley Hall effect. This allows the memory state encoded in the ferroelectric monolayer to be read out via the anomalous valley Hall signal of the heterostructures. The switchable anomalous valley Hall effect can also be achieved by applying biaxial strain in the GdF2/Sc2CO2 multiferroic heterojunction. By harnessing this intriguing anomalous valley Hall effect switching characteristic, we develop a nonvolatile valleytronics memory device. This work provides a way to achieve nonvolatile control in valleytronics and promotes the design of memory devices. [ABSTRACT FROM AUTHOR]

With the rise of demand for smart wearable and flexible electronic devices in the modern world, high‐performance hybrid mechanical energy harvesters (HMEHs), which can easily convert biomechanical energy into electricity for powering a variety of portable electronic gadgets and operating smart sensors, have gained extensive interest. Herein, propose piezo/ferroelectric and dielectric niobium (Nb)‐doped bismuth titanate (Bi4Ti3‐xNbxO12, NBTO) plates, are proposed and synthesized by a molten‐salt synthesis technique, and they are further embedded into the poly(vinylidene fluoride‐co‐hexafluoropropylene) (NBTO/PVDF‐HFP) flexible composite film (CF) to construct a flexible HMEH. The prepared NBTO/PVDF‐HFP CFs reveal good piezo/ferroelectricity, β‐phase fraction, and dielectric properties, which can improve the electrical output performance of the HMEH. The 2 wt.% NBTO/PVDF‐HFP CF‐based HMEH exhibits high and stable electrical performance of ≈175 V, ≈5.8 µA, ≈76 µC m−2, and ≈2.02 W m−2, respectively. Furthermore, the durability and mechanical robustness analysis of the HMEH is conducted for several days. The real‐time applications of the HMEH are demonstrated by harvesting the biomechanical energy obtained from daily human activities and powering various portable electronics. Also, the HMEH integrated with an Arduino microcontroller unit is employed as a smart sensor switch for implementing smart home/building stair‐sensing applications and sending emergency e‐mail alerts. [ABSTRACT FROM AUTHOR]

BiFe 1-2 x Zn x Co x O 3 (BFZCO) thin films (x = 0 %, 1 %, 2 %, 3 %, 4 %, 5 %) were deposited on FTO/glass substrates by sol-gel method. We systematically investigated the effects of equal doping of (Zn, Co) on the crystal microstructure, leakage current, leakage mechanism, and ferroelectric properties of BFZCO thin films. The XRD patterns indicate that all samples matched the chalcogenide structure without any impurity phases. The BiFe 0.96 Zn 0.02 Co 0.02 O 3 (BFZCO-2) film exhibited a large residual polarization (2 P r = 339.9 μC/cm2) at an electric field strength of approximately 2000 kV/cm. The curve of leakage current density shows that equal doping of (Zn, Co) can considerably decrease the leakage current of BFO thin films at low electric fields. Furthermore, the mechanism of leakage conduction has shifted from Ohmic conduction at low electric fields to SCLC conduction at high electric fields. [ABSTRACT FROM AUTHOR]

Ferroelectric flexible polymer composite films of poly(vinylidene fluoride) (PVDF) with different weight percentages (10.0%, 20.0%, 30.0%, 40.0%, and 50.0%) of (Bi0.5Ba0.25Sr0.25) (La0.5Ti0.5) O3 were synthesized by solvent casting method. Analysis using the x‐ray diffractometer and Fourier transform infrared spectroscopy tools revealed the presence of the different phases (α, β) of PVDF. Scanning electron microscope morphology illustrates the homogenous dispersion of ceramics particles in the matrix. The differential scanning calorimetry curve (under 25–400°C) gives the value of melting temperature (Tm=169.98°C) and percentage crystallinity is about 29.45% for 50 wt.% composite. The findings demonstrated that the composite has good thermal stability up to 169.98°C. Dielectric analysis shows ferroelectric and dielectric behavior and also distinguishes α and β phases of PVDF. It was found that the composite film containing 50 wt.% (Bi0.5Ba0.25Sr0.25) (La0.5Ti0.5) O3 had a dielectric constant (εr) of 38 (at 100 Hz) and dielectric loss of 0.059, which are the maximum among the samples. The relative permittivity rises with an increase in filler content due to electrostatics and interfacial polarization between PVDF (CH2CF2 dipole) and ceramic. The real and imaginary part of impedance spectroscopy with frequency (Cole–Cole plots) for composite (10.0–50.0 wt.%) at 25°C are also investigated. The current study provides a fresh perspective on the fact that PVDF‐(Bi0.5Ba0.25Sr0.25) (La0.5Ti0.5) O3 composite system has improved thermal stability and dielectric characteristics. [ABSTRACT FROM AUTHOR]

Polymer blends are regarded as a straightforward and effective method to enhance the energy storage performance of dielectric film capacitors. However, how the components and structures within the blend systems affect the energy density and efficiency remains insufficiently explored in-depth. In this discourse, employing a polymer blend of ferroelectric and linear dielectric phases as a paradigm, we perform phase-field simulations to elucidate the effects of ferroelectric phase volume fractions, geometrical dimensions, and the dielectric constant of the linear phase on the energy storage capabilities. Concurrently, we have devised six divergent blending microstructures to probe the ramifications of structural variances on the overarching performance metrics. We also analyze the domain configurations and switching dynamics under varying electric fields to understand the performance variations and delineate the determinants conducive to superior energy density and efficiency. This paper theoretically establishes the component–content–structure–performance relationships of different polymer blend systems, which is expected to better guide the innovative design of new polymer blend dielectrics. [ABSTRACT FROM AUTHOR]

The present study elucidates the role of annealing with electric field on lamellar crystalline structure and molecular orientation of polymer chains in ferroelectric copolymer (P(VDF‐TrFE)) and ferroelectric terpolymer (P(VDF‐TrFE‐CFE)) spin‐coated thin films. The ferroelectric polymer thin films annealed under an electric field support the growth of nanostructure with an “edge‐on” lamellar crystalline structure having in‐plane molecular chain orientation. The poled P(VDF‐TrFE) thin films have higher remnant polarization (Pr) ≈6.2 µC cm−2 and saturation polarization (Ps) ≈8.2 µC cm−2 at an applied electric field of 250 MV/m compared to unpoled thin films having Pr ≈4.7 and Ps ≈6.2 µC cm−2. Also, poled P(VDF‐TrFE) thin films show lower coercive field (Ec) ≈94 MV/m compared to an unpoled thin film having Ec ≈105 MV/m. Similarly, poled PVDF‐TrFE‐CFE thin film shows better ferroelectric properties having Pr ≈0.4 and Ps ≈5.7 µC cm−2 at an applied electric field of 200 MV m−1 compared to unpoled thin films having Pr ≈0.4 and Ps ≈4.1 µC cm−2. The storage energy efficiency of unpoled and poled P(VDF‐TrFE‐CFE) thin films is measured to be ≈75% and 80%. Annealing of ferroelectric P(VDF‐TrFE) polymer thin films under an electric field demonstrates improved ferroelectric and electroactive properties. [ABSTRACT FROM AUTHOR]

This work describes the synthesis of a polysilane (PSH)–barium titanate (BT) ferroelectric polymer composite that keeps stable in the presence of ultraviolet light (UV). To evaluate the stability in the presence of UV radiation and the mechanism of interaction between the PSH matrix and BT, FTIR measurements were carried out. The UV/VIS absorption measurement reveals that PSH absorbs strongly in the ultraviolet range, while the composite behaves similarly to BT. Although PSH is a semiconductor, the dielectric spectrometry analysis determined that BT is a ferroelectric material due to its high dielectric constant and low dielectric losses. In contrast to the polymer matrix, the composite polymer has a greater dielectric constant and a lower loss permittivity. PSH is a semiconductor, as indicated by its electrical conductivity of 10−5 S/cm; nevertheless, the UV-irradiated polymer has antistatic properties (10−8 S/cm). Irradiated or not, the polymer composite is a semiconductor, with conductivity of 10−6 S/cm, significantly lower than that of PSH. The interaction with electromagnetic radiation indicates electromagnetic shielding behavior for both BT (highest absorption magnitude of −57 dB) and the polymer composite (maximum absorption magnitudes range from 8.4 to −15.2 dB). Based on these research results, the novel composite with specific characteristics may be used in electronic applications in UV-irradiated conditions. [ABSTRACT FROM AUTHOR]

Ferroelectric polymers have emerged as crucial materials for the development of advanced organic electronic devices. Their recent high‐end commercial applications as fingerprint sensors have only increased the amount of scientific interest around them. Despite an ever‐larger body of studies focusing on optimizing the properties of ferroelectric polymers by physical means (e. g. annealing, stretching, blending or nano‐structuring), post‐polymerization chemical modification of such polymers has only recently become a field of active study with great promise in expanding the scope of those polymers. In this work, a solution‐based post‐polymerization modification method was developed for the safe and facile grafting of a plethora of functional groups to the backbone of commercially available Poly(vinylidene fluoride‐co‐trifluoroethylene P(VDF‐co‐TrFE) ferroelectric polymers. To showcase the versatility of this approach, photosensitive groups were grafted onto the polymeric backbone, enabling them to undergo photo‐cross‐linking. Finally, these modified polymers were used as functional negative photoresists in a photolithographic process, highlighting the potential of this method to integrate ferroelectric fluorinated electroactive polymers into standard electronic microfabrication production lines. [ABSTRACT FROM AUTHOR]

This study explores the potential advantages of metal–ferroelectric–insulator–semiconductor (MFIS) structures compared with established metal–ferroelectric–semiconductor (MFS) and metal–ferroelectric–metal structures in the context of nonvolatile memory devices. Despite the superior performance of MFS structures in terms of electric field maintenance, switching speed, and power consumption, the presence of interface-related issues between the ferroelectric material and the semiconductor may degrade device performance. We propose an MFIS structure incorporating ultrathin interfacial layers (ILs) of SiO 2 , HfO 2 , and ZrO 2 to address these issues. These insulator layers enhance device endurance by reducing physical stress and trap density at the interface, thereby improving electrical performance and long-term stability. Moreover, the presence of an IL reduces charge leakage between the ferroelectric layer and semiconductor, contributing to the resolution of the sneak path current problem. An additional feature of MFIS devices is their self-rectifying behavior, simplifying circuit design and manufacturing processes by eliminating the need for an external rectification circuit, consequently reducing costs. Through a series of experiments, this study evaluates the performance of the MFIS structure, investigates the ferroelectric properties of HfAlOx-based FTJs, and examines the conduction mechanism of the MFIS structure. By comparing the o-phase of MFS, SiO 2 , HfO 2 , and ZrO 2 devices via grazing incidence X-ray diffraction (GIXRD) and using the positive-up-negative-down method to extract polarization and coercive voltage, we provide a comprehensive investigation of the impact of ultrathin ILs on ferroelectric properties. This research aims to offer valuable insights into the advancement of memory device technologies, presenting the MFIS structure as a promising platform for next-generation memory technologies. Further sections will elaborate on the experimental setup, methodology, and detailed study findings. [ABSTRACT FROM AUTHOR]

The association of 2D materials and ferroelectrics offers a promising approach to tune the optoelectronic properties of atomically thin Transition Metal Dichalcogenides (TMDs). In this work, the combined effect of ferroelectricity and light on the optoelectronic properties of monolayer (1L)‐MoS2 deposited on periodically poled lithium niobate crystals is explored. Using scanning micro‐photoluminescence, the effect of excitation intensity, scanning direction, and domain walls on the 1L‐MoS2 photoluminescence properties is analyzed, offering insights into charge modulation of MoS2. The findings unveil a photoinduced charging process dependent on the ferroelectric domain orientation, in which light induces charge generation and transfer at the monolayer‐substrate interface. This highlights the substantial role of light excitation in ferroelectrically‐driven electrostatic doping in MoS2. Additionally, the work provides insights into the effect of the strong, nanometrically confined electric fields on LiNbO3 domain wall surfaces, demonstrating precise control over charge carriers in MoS2, and enabling the creation of deterministic p‐n homojunctions with exceptional precision. The results suggest prospects for novel optoelectronic and photonic application involving monolayer TMDs by combining light‐matter interaction processes and the surface selectivity provided by ferroelectric domain structures. [ABSTRACT FROM AUTHOR]

The association of 2D materials and ferroelectrics offers a promising approach to tune the optoelectronic properties of atomically thin Transition Metal Dichalcogenides (TMDs). In this work, the combined effect of ferroelectricity and light on the optoelectronic properties of monolayer (1L)‐MoS2 deposited on periodically poled lithium niobate crystals is explored. Using scanning micro‐photoluminescence, the effect of excitation intensity, scanning direction, and domain walls on the 1L‐MoS2 photoluminescence properties is analyzed, offering insights into charge modulation of MoS2. The findings unveil a photoinduced charging process dependent on the ferroelectric domain orientation, in which light induces charge generation and transfer at the monolayer‐substrate interface. This highlights the substantial role of light excitation in ferroelectrically‐driven electrostatic doping in MoS2. Additionally, the work provides insights into the effect of the strong, nanometrically confined electric fields on LiNbO3 domain wall surfaces, demonstrating precise control over charge carriers in MoS2, and enabling the creation of deterministic p‐n homojunctions with exceptional precision. The results suggest prospects for novel optoelectronic and photonic application involving monolayer TMDs by combining light‐matter interaction processes and the surface selectivity provided by ferroelectric domain structures. [ABSTRACT FROM AUTHOR]

Considering the growing demand for piezoelectric energy harvesting from ferroelectric–polymer-based composite materials and the benefits associated with them, this work focuses on piezoelectric energy harvesting from poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP)/BZT-BCT/GO hybrid composite films synthesized via solution casting followed by the hot-pressing method. Structural properties were analyzed using XRD, FTIR, and Raman spectroscopy. SEM micrographs confirmed the presence of pores in the synthesized samples that provided an added advantage toward enhancing its piezoelectricity. The dielectric and ferroelectric properties were studied, in which the dielectric constant increased up to 20.69, and the remnant polarization was found to be 0.0560 μ C cm−2. A PUND analysis was performed to validate the data obtained from the static hysteresis loop. Piezoelectric charge and voltage coefficients were measured, which reach up to "−31 pC N−1" and "−252.5 mV m N−1," respectively. Figure of merit, electromechanical coupling coefficient, and quality factor of the as-synthesized samples were calculated. A harvester prototype was fabricated to investigate the energy harvesting performance of the synthesized hybrid composite films. The highest open circuit voltage, short circuit current, and power density were recorded as 2.19 V, 24.17 nA, and 468.43 μ W m−2, respectively. The harvested energy can be utilized for powering low-power devices, showing the real-time applicability of the synthesized hybrid composite films. [ABSTRACT FROM AUTHOR]

Achieving energy-efficient and high-performance field-effect transistors (FETs) is one of the most important goals for future electronic devices. This paper reports semiconducting single-walled carbon nanotube FETs (s-SWNT-FETs) with an optimized high- k relaxor ferroelectric insulator P(VDF-TrFE-CFE) thickness for low-voltage operation. The s-SWNT-FETs with an optimized thickness (∼800 nm) of the high- k insulator exhibited the highest average mobility of 14.4 cm2 V−1s−1 at the drain voltage (I D) of 1 V, with a high current on/off ratio (I on/off >105). The optimized device performance resulted from the suppressed gate leakage current (I G) and a sufficiently large capacitance (>50 nF cm−2) of the insulating layer. Despite the extremely high capacitance (>100 nF cm−2) of the insulating layer, an insufficient thickness (<450 nm) induces a high I G, leading to reduced I D and mobility of s-SWNT-FETs. Conversely, an overly thick insulator (>1200 nm) cannot introduce sufficient capacitance, resulting in limited device performance. The large capacitance and sufficient breakdown voltage of the insulating layer with an appropriate thickness significantly improved p-type performance. However, a reduced n-type performance was observed owing to the increased electron trap density caused by fluorine proportional to the insulator thickness. Hence, precise control of the insulator thickness is crucial for achieving low-voltage operation with enhanced s-SWNT-FET performance. [ABSTRACT FROM AUTHOR]

Lead halide molecular ferroelectrics represent an important class of luminescent ferroelectrics, distinguished by their high chemical and structural tunability, excellent processability and distinctive luminescent characteristics. However, their inherent instability, prone to decomposition upon exposure to moisture and light, hinders their broader ferroelectric applications. Herein, for the first time, we present a series of isoreticular metal–organic framework (MOF)‐type lead halide luminescent ferroelectrics, demonstrating exceptional robustness under ambient conditions for at least 15 months and even when subjected to aqueous boiling conditions. Unlike conventional metal‐oxo secondary building units (SBUs) in MOFs adopting highly centrosymmetric structure with limited structural distortion, our lead halide‐based MOFs occupy structurally deformable [Pb2X]+ (X=Cl−/Br−/I−) SBUs that facilitate a c‐axis‐biased displacement of Pb2+ centers and substantially contribute to thermoinducible structural transformation. Importantly, this class of MOF‐type lead halide ferroelectrics undergo ferroelectric‐to‐paraelectric phase transitions with remarkably high Curie temperature of up to 505 K, superior to most of molecular ferroelectrics. Moreover, the covalent bonding between phosphorescent organic component and the light‐harvesting inorganic component achieves efficient spin‐orbit coupling and intersystem crossing, resulting in long‐lived afterglow emission. The compelling combination of high stability, ferroelectricity and afterglow emission exhibited by lead halide MOFs opens up many potential opportunities in energy‐conversion applications. [ABSTRACT FROM AUTHOR]

Neuromorphic ferroelectric transistors integrating sensing and memory capabilities for photoelectric stimuli have provided a remarkable platform for multifunctional bionic vision. However, most hardware demonstrations utilizing ferroelectric transistors cannot implement multiple bio‐visual functions simultaneously under a small operating voltage with scalable material systems, which reduces the compatibility with complementary metal‐oxide‐semiconductor (CMOS) technology and blocks further bio‐visual applications. Herein, an optoelectronic transistor gated is constructed with ferroelectric LiNbO3, which exhibits sensing‐memory‐processing functions and logic integration simultaneously under a low operating voltage (≈1.5 V). Benefiting from the programmable photoinduction and strong ferroelectric polarization, the reliable and highly controllable synaptic characteristics and the bio‐visual selective learning behavior are successfully demonstrated. A high recognition accuracy (≈94.5%) in simulations is also achieved due to the unique linear synaptic plasticity. Furthermore, based on dual‐wavelength modulation, the full‐optical logics "AND" and "OR" are established within the same device. This work provides novel opportunities for the complex multifunctional bionic vision and toward large‐scale integration compatible with silicon‐based CMOS processes. [ABSTRACT FROM AUTHOR]

Neuromorphic optoelectronic vision system inspired by the biological platform displays potential for in‐sensor computing. However, it is still challenge to process multiwavelength image in noisy environment with simple device configuration and light‐tunable biological plasticity. Here, a prototype visual sensor is demonstrated based on ferroelectric copolymer poly(vinylidene fluoride‐trifluoroethylene) (P(VDF‐TrFE)) and 2D rhenium disulfide (ReS2) with integration of recognition, memorization, and pre‐processing functions in the same device. Such synaptic devices achieve impressive electronic characteristics, including a current on/off ratio of 109 and mobility of 45 cm2 V−1 s−1. Various synaptic plasticity behaviors have been achieved owing to the switchable ferroelectricity, enabling them to establish an artificial neural network (ANN) with high digit recognition accuracy of 89%. Through constructing optoelectronic device array, object extraction is achieved with wavelength‐selective capability in noisy environment, closely resembling human retina for color recognition. Above outcomes bring a notable improvement in the image recognition rate from 72% to 96%. Besides, low energy consumption comparable to single biological event can be realized. With these multifunctional features, this work inspires highly integrated neuromorphic systems and the development of wavelength‐selective artificial visual platform. [ABSTRACT FROM AUTHOR]

Van der Waals ferroelectric semiconductors, which encompass both ferroelectricity and semiconductivity, have garnered intensive research interests for developing novel non‐volatile functional devices. Previous studies focus on ferroelectricity characterization and device demonstration, with little attention paid to the fundamental electronic properties of these materials and their functional structures, which are essential for both device design and optimization. In this study, scanning microwave impedance microscopy (sMIM) is utilized to investigate the ferroelectric semiconductor of α‐phase indium selenide (α‐In2Se3) and its synaptic field effect transistors. α‐In2Se3 nanoflakes of varying thicknesses are visualized through capacitive signal detection, whose responses are consistent with finite element simulations manifesting dependence on both flake thickness and its semiconductor property. sMIM spectroscopy performed on α‐In2Se3‐based metal‐oxide‐semiconductor (MOS) structures reveals typical MOS capacitance‐voltage characteristics, with additional hysteresis arising from the ferroelectric switching of α‐In2Se3. The local conductance state changes of synaptic α‐In2Se3 ferroelectric semiconductor transistors (FeSFET) in response to gate voltage stimuli are effectively detected by in situ sMIM, in good agreement with electrical device transport properties. This work deepens the understanding of ferroelectric semiconductor physics toward their practical device application. [ABSTRACT FROM AUTHOR]

The vast energy storage potential of polymer composite dielectrics in high pulse power sources stands in stark contrast to the unbalanced improvements in discharge energy density (Ud), charge–discharge efficiency (η), and dielectric strength (Eb) as reported currently. Herein, a multistage coupled interface engineering design is proposed: a novel gradient alternating dielectric buffer layer (G‐A‐DBL) is constructed, which consists of inorganic low‐k nanoclay aluminosilicate layer and high‐k ferroelectric layer assembled in a highly oriented alternation as a basic unit and gradient distribution in polymer matrix. This design achieves electric field confinement from the nanoscale to the macroscopic level and achieves an ultra‐balanced enhancement effect, resulting in a Ud of 28.5 J cm−3, an η of 80%, and an Eb of 676 kV mm−1. The universal charge retention ability of charge traps from aluminosilicate heterogeneous skeletons is demonstrated by combining density functional theory calculations and scanning probe measurements. The G‐A‐DBL design integrates traditional charge trapping, heterostructure formation, and gradient modulation, effectively suppressing the entire process of carrier excitation, transport, and before capture. This work advances the basic understanding of charge confinement within inorganic interface charge traps, demonstrating the most well‐balanced enhancement effect and potential for broad application across dielectric polymer nanocomposites. [ABSTRACT FROM AUTHOR]

The dielectric properties of synclinic (ferroelectric SmC*) and anticlinic (antiferroelectric SmCA*) smectic liquid crystals composed of molecules of one chiral version (S) are presented and compared with properties of racemic mixture (R, S), showing SmC and SmCA phases. The racemic mixture completely loses its ferroelectric and antiferroelectric properties. Surprisingly, only one dielectric mode observed in the antiferroelectric SmCA* phase disappeared in the dielectric response of the racemic SmCA phase. Additionally, we observed that in the SmC phase, seen in the racemic mixture, the weak dielectric mode (named the X mode) is detected, which seems to be the continuation of the PL mode existing in the racemic SmCA. Moreover, this mode in the racemic SmC has nothing to do with the Goldstone mode, typical for the SmC* phase. This paper describes in detail the real and imaginary parts of dielectric permittivity in smectic phases for the enantiomer and racemate with and without a DC field, compares the properties of the X and PL modes, and discusses the full scheme of dielectric modes in enantiomer and racemate. [ABSTRACT FROM AUTHOR]

The presence of core–shell nanowire diminishes the distribution distortion of local electric field and also obstructs the flow of charge carriers. Polymer composite with fibrous structure demonstrates the improved polarization, and this work sheds a light on the energy loss related to the interface of polymer film for application of next-generation dielectric capacitor. [Display omitted] The development of polymer film with large electrical displacement is essential for the applications of lightweight and compact energy storage. The dielectric diversity at interface of polymer composite should be addressed to realize the film capacitor with high energy density and dielectric reliability. In this work, poly(vinylidene fluoride- co -chlorotrifluoroethylene) (P(VDF-CTFE)) nanocomposite was incorporated by core–shell nanowire with covalent organic framework (COF) outer coating to alleviate the dielectric mismatch at interface. After the preparation of Ag nanowire through polyol reduction, polyaniline (PANI) and COF layers were sequentially deposited to construct core–shell Ag@polyaniline@covalent organic framework (Ag@PANI@COF) nanowire. According to the unique core–shell architecture, the COF framework is utilized to suppress the remanent polarization while high electrical displacement is preserved by the center Ag nanowire. The maximum energy density of 25.0 J/cm3 at 425 MV/m is obtained in 0.1 wt% stretched Ag@PANI@COF/P(VDF-CTFE) nanocomposite. The presence of core–shell nanowire depresses the distribution distortion of electric field and the diffusion of charge carriers under high field. This work demonstrates an effective method to develop the polymer film with large electrical displacement, and sheds a light on insightful exploration of interfacial polarized mechanism in polymer dielectric composite. [ABSTRACT FROM AUTHOR]

The local interaction within poly(vinylidene fluoride)/poly(3,4‐ethyelenedioxythiophene):poly(styrelenesulfonate) (PVDF/PEDOT:PSS) composite films has been explored in this study. Vibrational and impedance spectroscopy were used extensively to investigate the potential interactions within the moieties of PVDF and PEDOT:PSS in the composite. The increased concentration of PEDOT:PSS used as additives enhanced the dielectric constant of the composite films significantly. Both the AC conductivity and the estimated mobility also increased in the composite films with increasing additives. X‐ray absorption spectroscopy gave an insight into the local chain interactions within the polymer composite films. A shift in the C K‐edge toward higher energy confirmed the local interaction of the polymer moieties, suggesting a change in the polymer chain structure due to the possible association of moieties. [ABSTRACT FROM AUTHOR]

Ferroelectric tunnel junctions (FTJs) have been the subject of ongoing research interest due to its fast operation based on the spontaneous polarization direction of ultrathin ferroelectrics and its simple two-terminal structure. Due to the advantages of FTJs, such as non-destructive readout, fast operation speed, low energy consumption, and high-density integration, they have recently been considered a promising candidate for non-volatile next-generation memory. These characteristics are essential to meet the increasing demand for high-performance memory in modern computing systems. In this review, we explore the basic principles and structures of FTJs and clarify the elements necessary for the successful fabrication and operation of FTJs. Then, we focus on the recent progress in perovskite oxide, fluorite, 2-dimensional van der Waals, and polymer-based FTJs and discuss ferroelectric materials expected to be available for FTJs use in the future. We highlight various functional device applications, including non-volatile memories, crossbar arrays, and synapses, utilizing the advantageous properties of ferroelectrics. Lastly, we address the challenges that FTJ devices currently face and propose a direction for moving forward. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectric polymers exhibiting a giant electrocaloric effect (ECE) can potentially be used to create next‐generation solid‐state coolers. Under an electric field, poly(vinylidene fluoride‐trifluoroethylene‐chlorofluoroethylene) terpolymer goes through a large dipolar entropy change producing a high adiabatic temperature change (ΔTECE). This work resolves the molecular origins of the large entropy change behind the electric field‐induced dipole switching. A Fourier transform infrared spectroscopy equipped with a high voltage source is used to operandoly observe the characteristic molecular vibrational modes. A short‐range trans (T) conformation of the CF2‐CH2 dyads interrupted by a gauche (G) conformation, e.g., TTTG in the terpolymer chain, undergoes a dynamic transformation that leads to a corresponding ΔTECE whenever an electric field is applied. The molecular dynamics simulation also proves that the energy barrier that the transformation from TTTGs into a long T sequence overcomes is smaller than that for all other conformations. A mixed solvent system is used to obtain T3G‐enriched terpolymer films exhibiting a 4.02 K ΔTECE at 60 MV m−1 and these films are employed to manufacture a 2‐layer‐cascaded cooling device that achieves a 6.7 K temperature lift, the highest reported value for a 2‐layer cascaded device made of fluoropolymers. [ABSTRACT FROM AUTHOR]

Oxygen diffusion coefficients in the metastable ferroelectric phase of polycrystalline hafnium zirconium oxide (HZO) thin films have been quantified using 18O tracers and time-of-flight secondary ion mass spectrometry. 11.5 nm thick HZO films containing 16O were deposited by plasma-enhanced atomic layer deposition followed by post-metallization annealing to crystallize into the ferroelectric phase. A 1.2 nm thick HZO layer containing 18O was then deposited using thermal atomic layer deposition with H218O as a reactant. Thermal anneals were conducted at 300, 350, and 400 °C and the ferroelectric phase confirmed after the anneals by x-ray diffraction, infrared spectroscopy, and electrical property measurements. 18O depth profiles were measured and fit with a thin film diffusion equation to determine the oxygen diffusion coefficients. Oxygen diffusion coefficients ranged from approximately 2 × 10−18 cm2/s at 300 °C to 5 × 10−17 cm2/s at 400 °C with an activation energy of 1.02 ± 0.24 eV. [ABSTRACT FROM AUTHOR]

A large depolarization field in single‐domain PbTiO3 is anticipated to drive the spatial separation of photogenerated charge carriers and enable potential active sites for photocatalytic overall water splitting reaction. However, the negatively polarized surface usually cannot provide sufficient active sites for water oxidation to oxygen because of lacking oxygen vacancies, inevitably hindering photocatalytic water splitting reaction. Here, the ferroelectric polarization screening is reconstructed by a heteroepitaxial SrTiO3 film on the positively polarized surface of PbTiO3 nanoplates to generate abundant oxygen vacancies on the negatively polarized surface as active sites for water oxidation. Moreover, it is experimentally and theoretically revealed that the epitaxial SrTiO3 layer on the positively polarized surface is also beneficial for good dispersion of cocatalyst and the formation of low Schottky barrier height at the interface between the heterostructure and the cocatalyst for efficient electron transfer. Compared with pristine PbTiO3, the obtained PbTiO3/SrTiO3 heteroepitaxial structure with the simultaneous regulation of positively and negatively polarized surfaces delivered a greatly enhanced photocatalytic overall water splitting with stoichiometric ratio (2:1) of hydrogen and oxygen evolution by a factor of 15 times. These findings might open up a new avenue for the design of ferroelectric photocatalysts with excellent activity. [ABSTRACT FROM AUTHOR]

Copolymers based on vinylidene fluoride are potential materials for ferroelectric memory elements. The trend in studies showing that a decrease in the degree of crystallinity can lead to an unexpected increase in the electric breakdown field is noted. An analysis of the literature data reveals that in fluorine-containing ferroelectric polymers, when using a bipolar triangular field, the hysteresis loop has an unclosed shape, with each subsequent loop being accompanied by a decrease in the dielectric response. In this work, the effect of the structure of self-polarized films of copolymers of vinylidene fluoride with tetrafluoroethylene and hexafluoropropylene on breakdown processes was studied. The structure of the polymer films was monitored using infrared spectroscopy (IR) and X-ray diffraction. Kelvin probe force microscopy (KPFM) was applied to characterize the local electrical properties of the polymers. For the films of the first copolymer, which crystallize in the polar β-phase, asymmetry in the dielectric response was observed at fields greater than the coercive field. For the films of the copolymers of vinylidene fluoride with hexafluoropropylene, which crystallize predominantly in the nonpolar α-phase, polarization switching processes have also been observed, but at lower electric fields. The noted phenomena will help to identify the influence of the structure of ferroelectric polymers on their electrical properties. [ABSTRACT FROM AUTHOR]