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The discovery of nanoscale ferroelectricity in hafnia (HfO2) has paved the way for next generation high‐density, non‐volatile devices. Although the surface conditions of nanoscale HfO2 present one of the fundamental mechanism origins, the impact of external environment on HfO2 ferroelectricity remains unknown. In this study, the deleterious effect of ambient moisture is examined on the stability of ferroelectricity using Hf0.5Zr0.5O2 (HZO) films as a model system. It is found that the development of an intrinsic electric field due to the adsorption of atmospheric water molecules onto the film's surface significantly impairs the properties of domain retention and polarization stability. Nonetheless, vacuum heating efficiently counteracts the adverse effects of water adsorption, which restores the symmetric electrical characteristics and polarization stability. This work furnishes a novel perspective on previous extensive studies, demonstrating significant impact of surface water on HfO2‐based ferroelectrics, and establishes the design paradigm for the future evolution of HfO2‐based multifunctional electronic devices. [ABSTRACT FROM AUTHOR]

This study employs a data‐driven machine learning approach to investigate specific ferroelectric properties of Al1−xScxN thin films, targeting their application in next‐generation nonvolatile memory (NVM) devices. This approach analyzes a vast design space, encompassing over a million data points, to predict a wide range of coercive field values that are crucial for optimizing Al1−xScxN‐based NVM devices. We evaluated seven machine learning models to predict the coercive field across a range of conditions, identifying the random forest algorithm as the most accurate, with a test R2 value of 0.88. The model utilized five key features: film thickness, measurement frequency, operating temperature, scandium concentration, and growth temperature to predict the design space. Our analysis spans 13 distinct scandium concentrations and 13 growth temperatures, encompassing thicknesses from 9–1000 nm, frequencies from 1 to 100 kHz, and operating temperatures from 273 to 700 K. The predictions revealed dominant coercive field values between 3.0 and 4.5 MV/cm, offering valuable insights for the precise engineering of Al1−xScxN‐based NVM devices. This work underscores the potential of machine learning in guiding the development of advanced ferroelectric materials with tailored properties for enhanced device performance. [ABSTRACT FROM AUTHOR]

Extending ferroelectric materials to two-dimensional limit provides versatile applications for the development of next-generation nonvolatile devices. Conventional ferroelectricity requires materials consisting of at least two constituent elements associated with polar crystalline structures. Monolayer graphene as an elementary two-dimensional material unlikely exhibits ferroelectric order due to its highly centrosymmetric hexagonal lattices. Here, we report the observations of electronic ferroelectricity in monolayer graphene by introducing asymmetric moiré superlattice at the graphene/h-BN interface, in which the electric polarization stems from electron-hole dipoles. The polarization switching is probed through the measurements of itinerant Hall carrier density up to room temperature, manifesting as standard polarization-electric field hysteresis loops. We find ferroelectricity in graphene moiré systems exhibits generally similar characteristics in monolayer, bilayer, and trilayer graphene, which indicates layer polarization is not essential to observe the ferroelectricity. Furthermore, we demonstrate the applications of this ferroelectric moiré structures in multi-state nonvolatile data storage with high retention and the emulation of versatile synaptic behaviors. Our work not only provides insights into the fundamental understanding of ferroelectricity, but also demonstrates the potential of graphene for high-speed and multi-state nonvolatile memory applications. Monolayer graphene, with its highly centrosymmetric hexagonal lattice, is typically not considered ferroelectric. Here, the authors observe ferroelectricity in monolayer graphene by introducing asymmetric moiré superlattices, where polarization arises from electron-hole dipoles. [ABSTRACT FROM AUTHOR]

Integrating free‐standing complex oxides with two‐dimensional (2D) materials has recently attracted great interest, due to the rich physics evolving from such structures. Enhancing and tuning the opto–electronic properties of these systems is of high importance for a multitude of applications, such as sensors, memory devices or optical communications. The electrostatic control of photoluminescence of monolayer MoS2 at room temperature via integration of free‐standing BaTiO3 (BTO), a ferroelectric perovskite oxide is presented. It is shown that the use of BTO leads to highly tunable exciton emission of MoS2 in a minimal range of gate voltages. Due to BTO's ferroelectric polarization‐induced doping, large peak emission shifts as well as a large and tunable A trion binding energy in the range of 40–100 meV are observed. These measurements are compared with those carried out when the BTO is replaced by a hexagonal boron nitride (hBN) dielectric layer, confirming BTO's superior gating properties and thus lower power consumption. Additionally, advantage of the ferroelectric switching of BTO is taken by fabricating devices where the BTO layer is decoupled from the gate electrode with a SiO2 layer. Choosing to isolate the BTO allows to induce large remanent behavior of MoS2's excitonic features. [ABSTRACT FROM AUTHOR]

Miniaturizing van der Waals (vdW) ferroelectric materials to atomic scales is essential for modern devices like nonvolatile memory and sensors. To unlock their full potential, their growth mechanisms, interface effects, and stabilization are preferably investigated, particularly for ultrathin 2D nanosheets with single‐unit cell thickness. This study focuses on Bi2TeO5 (BTO) and utilizes precise control over growth kinetics at the nucleation temperature to create specific interfacial reconfiguration layers. Ultrathin BTO nanosheets with planar ferroelectricity at a single‐unit cell thickness are successfully grown. Atomic‐scale characterization reveals a disordered distribution of elements in the interfacial layer, which buffers strain from lattice mismatch. The theoretical calculations support these observations. Furthermore, this strategy also can be extended to the growth of a variety of 2D ternary oxide nanosheets. This work contributes to a better understanding of growth and stability mechanisms in 2D ultrathin nanosheets. [ABSTRACT FROM AUTHOR]

The development of ultrathin (≤5 nm) hafnia‐based ferroelectric (FE) films is essential for achieving low operating voltages, facilitating their integration into advanced process nodes for low‐power and non‐volatile memory applications. However, challenges in ultrathin FE films arise from the depolarization field and interface‐related issues, leading to an antiferroelectric‐like (AFE‐like) polarization switching behavior and more significant wake‐up effects, causing operational inconvenience and reliability concerns. Here, interface‐modulated ferroelectricity is reported in 4 nm Hf0.5Zr0.5O2 (HZO) thin films, demonstrating excellent properties with low operating voltage, enhanced switching speed, and high reliability. Electrical and structural characterizations reveal that adjusting interface asymmetry may introduce a substantial built‐in field (Ebi) and an AFE‐like switching behavior can exhibit a robust FE‐like characteristic. This AFE‐to‐FE‐like transition is driven by switching kinetics rather than commonly proposed phase transitions. Furthermore, a comprehensive model is developed to elucidate the intricate physics of the modulation mechanism by asymmetric interfaces, emphasizing the critical roles of depolarizing effects and Ebi on ferroelectricity. This work underscores the importance of interfaces in engineering ferroelectricity for advanced electronic applications. [ABSTRACT FROM AUTHOR]

Hybrid improper ferroelectrics (HIFs), characterized by ferroelectric polarization arising from the rotation of two symmetry inequivalent antiferrodistortive modes, exhibit exotic properties such as T-independent dielectric constants and robustness against depolarizing field. Here, using first-principles simulations, we report a new P 2 1 phase in a Si-compatible CeO2/HfO2 superlattice that exhibits remarkably robust hybrid improper ferroelectricity, induced by the in-plane oxygen rotations of two antiferrodistortive distortion modes. These non-polar distortions are coupled with a polar distortion through a trilinear coupling in the superlattice, stabilizing ferroelectricity as the competing ground state with the assistance of epitaxial strain. The estimated out-of-plane polarization ( P = 30.3 μ C / c m 2 ) is switchable with a remarkably small energy barrier of 8.5 meV/atom and relatively smaller coercive field relative to bulk HfO2, expected to reduce the operational voltage of ferroelectric devices. Our discovery may offer unexpected opportunities for innovating high-performance, low-voltage devices, and promising advancements in next-generation CMOS compatible oxide-based electronics. [ABSTRACT FROM AUTHOR]

Multiferroic BaTiO 3 exhibiting ferroelectric and ferromagnetic behavior was synthesized via the high-energy ball milling of pure BaTiO 3 (BTO) powders for durations ranging from 15 to 60 min, followed by pressing and sintering at 1200 °C X-ray diffraction patterns of all synthesized samples predominantly revealed a BTO phase with a tetragonal structure and a secondary Ba 12 Fe 28 Ti 15 O 84 (BFTO) phase. The BFTO phase was formed after milling for more than 30 min because of chemical interactions between the BTO powder and milling media. Vibrating sample magnetometry confirmed the ferromagnetic nature of the sintered pellets. The specific magnetization increased with increasing milling duration, reaching a maximum value of 1.15 emu/g after 60 min of milling. This increase can be attributed to the distortion of the crystal structure and presence of a secondary phase, as confirmed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Additionally, electrical characterization revealed the dielectric nature of the materials, with relative permittivity ranging from 500 to 1800, maximum spontaneous polarization from 9.77 to 11.31 μC/cm2, coercive field from 3.86 to 11.12 kV/cm, and AC conductivity from 1 × 10−6 to 1 × 10−3 S/cm. The method described in this study is a simple and cost-effective approach to produce multiferroic materials with ferroelectric and relaxor ferroelectric behavior at room temperature, broadening their potential for technological applications. [ABSTRACT FROM AUTHOR]

CeO 2 -HfO 2 solid solution thin films (Hf 1-x Ce x O 2) were deposited on Pt(111)/TiO 2 /SiO 2 /Si(100) substrates using the chemical solution deposition method. This study investigates the influence of CeO 2 content and annealing temperature on the structure and ferroelectric properties of Hf 1-x Ce x O 2 films. Ferroelectric behavior is demonstrated in polycrystalline Hf 0.80 Ce 0.20 O 2 films with thicknesses ranging from 163 to 524 nm. And the structure of the films is analyzed using glancing incidence X-ray diffraction. The comprehensive results indicate that Hf 0.80 Ce 0.20 O 2 films annealed at 850 °C exhibit excellent ferroelectricity. Square hysteresis loops associated with the ferroelectric orthorhombic phase are observed, even in the 524-nm-thick film. The remnant polarization (P r) and coercive field (E c) range from 16 to 18 μC/cm2 and 1100–1250 kV/cm, respectively, under a maximum applied electric field of 2 MV/cm for all Hf 0.80 Ce 0.20 O 2 films. Furthermore, the film presents thickness-insensitive characteristic. The current work paves the new way to design high-performance thick HfO 2 -based ferroelectric films. [ABSTRACT FROM AUTHOR]

Multiferroic materials that exhibit interacting and coexisting properties, like ferroelectricity and ferromagnetism, possess significant potential in the development of novel technologies that can be controlled through the application of external fields. They also exhibit varying regions of polarity, known as domains, with the interfaces that separate the domains referred to as domain walls. In this study, using three-dimensional (3D) bragg coherent diffractive imaging (BCDI), we investigate the dynamics of multiferroic domain walls in a single hexagonal dysprosium manganite (h-DyMnO 3 ) nanocrystal under varying applied electric field. Our analysis reveals that domain wall motion is influenced by the pinning effects, and a threshold voltage of +3 V is required to overcome them. Using circular mean analysis and phase gradient mapping, we identified localised phase realignment and high-gradient regions corresponding to domain walls, providing insights into the behaviour of multiferroic systems under external stimuli. [ABSTRACT FROM AUTHOR]

Noncollinear ferroic materials are sought after as testbeds to explore the intimate connections between topology and symmetry, which result in electronic, optical, and magnetic functionalities not observed in collinear ferroic materials. For example, ferroaxial materials have rotational structural distortions that break mirror symmetry and induce chirality. When ferroaxial order is coupled with ferroelectricity arising from a broken inversion symmetry, it offers the prospect of electric‐field‐control of the ferroaxial distortions and opens up new tunable functionalities. However, chiral multiferroics, especially ones stable at room temperature, are rare. A strain‐stabilized, room‐temperature chiral multiferroic phase in single crystals of BaTiS3 is reported here. Using first‐principles calculations, the stabilization of this multiferroic phase having P63 space group for biaxial tensile strains exceeding 1.5% applied on the basal ab‐plane of the room temperature P63cm phase of BaTiS3 is predicted. The chiral multiferroic phase is characterized by rotational distortions of TiS6 octahedra around the long c‐axis and polar displacement of Ti atoms along the c‐axis. The ferroaxial and ferroelectric distortions and their domains in P63‐BaTiS3 are directly resolved using atomic resolution scanning transmission electron microscopy. Landau‐based phenomenological modeling predicts a strong coupling between the ferroelectric and the ferroaxial order making P63‐BaTiS3 an attractive test bed for achieving electric‐field‐control of chirality. [ABSTRACT FROM AUTHOR]

A synergistic realization of high electrocaloric effect (ECE) and excellent temperature stability in ferroelectrics are foundation for practical applications, which is, however, a major challenge in ferroelectric cooling community thus far. In confront with this long‐standing issue, an emergent monomorphic ferrodistortion strategy in NaNbO3‐based relaxor is proposed with flexible tetragonal polar nanoregions immersing in short‐range oxygen octahedral tilt. This not only contributes to large quantities of polar entities to increase entropy change but also produces highly robust oxygen octahedral tilt to persist ferroelectricity and obstruct thermal agitations. Therefore, a high ΔT of 0.96 K and an ultrawide temperature span ΔTspan of 110 K with a record‐high figure of merit of 4.74 is achieved in Ta‐doped NaNbO3‐BaTiO3 ceramics and these superior EC performances present a remarkable breakthrough in ferroelectric bulks cooling. This work thus provides an innovative way of utilizing ferrodistortive relaxor feature with polar nanoregions immersing in oxygen octahedral tilt to simultaneously boost EC value and temperature stability and thus monomorphic ferrodistortion is proposed as an effective strategy to develop high‐performance entropy‐change materials. [ABSTRACT FROM AUTHOR]

The pursuit of extreme device miniaturization and the exploration of associated physical phenomena has spurred significant interest in crystallographic phase control and ferroelectric switching in reduced dimensions. The recently discovered wurtzite ferroelectrics offer intriguing piezoelectric and ferroelectric properties, CMOS compatibility, and seamless integration with mainstream semiconductor technology. In this study, we present a comprehensive investigation of the crystallographic phase transition of ScAlN nanowires across the full Sc compositional range. While a gradual transition from wurtzite to cubic phase was observed with increasing Sc composition, we further demonstrate that a highly ordered wurtzite phase ScAlN can be confined at the ScAlN/GaN interface for Sc contents surpassing what is possible in conventional films. We provide the first evidence of ferroelectric switching in ScAlN nanowires, a result that holds significant implications for future device miniaturization. Our demonstration of tunable ferroelectric ScAlN nanowires opens new possibilities for nanoscale, domain, alloy, strain, and quantum engineering of wurtzite ferroelectrics, representing a significant stride toward the development of next-generation, miniaturized devices based on wurtzite ferroelectrics. [ABSTRACT FROM AUTHOR]

Pb-based perovskites play pivotal roles in ferroelectric research. In the search for new Pb-based ferroelectrics, we investigated the ferroelectric properties of Dion–Jacobson type CsPb2Nb3O10 and exfoliated 2D nanosheets. Ferroelectricity in CsPb2Nb3O10 was demonstrated for the first time. CsPb2Nb3O10 adopted a polar tetragonal structure with a modest TC = 260 °C and polarization PS = 7.93 μC cm−2; the polarization mainly arose from the out-of-plane displacements of Nb5+ ions and nearby oxygens. CsPb2Nb3O10 layered perovskite offers additional advantages for tailoring ferroelectric nanomaterials, as exfoliated 2D nanosheets provide novel platforms for investigating ferroelectric properties down to the 2D limit. Piezoresponse force microscopy confirmed stable ferroelectricity even in exfoliated 2D Pb2Nb3O10 nanosheets. [ABSTRACT FROM AUTHOR]

2D materials have been interested in recent years due to their unique properties and enormous potential in various fields. In particular, 2D ferroionics with both ferroelectricity and ionic conductivity shed light on new possibilities for van der Waals nanoelectronics. Here, supported by theoretical calculations and electrical characterizations, the reconfigurable van der Waals ferroionic barristor that can be used in multifunctional electronics including resistive devices and steep‐slope transistors is reported. Large modulation on the device properties is achieved by electrically driven migration and redistribution of mobile ions. The memory device shows an unprecedented long‐term stability with a switching ratio of ≈1010. Utilizing this ferroionic nature, 2D transistors able to beat the Boltzmann tyranny, with different gate configurations, are designed. The subthreshold swing (SS) exhibits sub‐60 mV per decade values over five decades of the drain current with a minimum of 12.1 mV per decade. This work paves the way for investigating the symbiotic relationship of ferroelectricity and ionic activities in van der Waals ferroionics and highlights their applications in advanced nanoelectronics. [ABSTRACT FROM AUTHOR]

Developing efficient photo‐piezocatalytic systems to achieve the conversion of renewable energy to chemical energy emerges enormous potential. However, poor catalytic efficiency remains a significant obstacle to future practical applications. Herein, a series of unique Au@BaTiO3 (Au@BT) yolk‐shell nanostructure photo‐piezocatalyst is constructed with single Au nanoparticle (Au NP) embedded in different positions within ferroelectric BaTiO3 hollow nanosphere (BT‐HNS). This special structure showcases excellent mechanical force sensitivity and provides ample plasmon‐induced interfacial charge‐transfer pathways. In addition, the powerful piezoelectric polarization electric field induced by the enhanced ferroelectric polarization electric field via corona poling treatment in BT‐HNS further promotes charge separation, CO2 adsorption and key intermediate conversion. Notably, BT with single Au NP encapsulated into hollow nanosphere shell with reinforced polarization (Au@BT‐1‐P) shows synergistically improved photo‐piezocatalytic CO2 reduction activity for producing CO with a high production rate of 31.29 µmol g−1 h−1 under visible light irradiation and ultrasonic vibration. This work highlights a generic tactic for optimized design of high‐performance and multifunctional nanostructured photo‐piezocatalyst. Meanwhile, these yolk‐in‐shell nanostructures with single Au nanoparticle as an ideal model may hold great promise to inspire in‐depth exploration of carrier dynamics and mechanistic understanding of the catalytic reaction. [ABSTRACT FROM AUTHOR]

Ferroelectric (FE)‐antiferromagnetic (AFM) multiferroic materials have sparked growing interest due to their huge possibilities in energy‐saving, photoelectric devices, nonvolatile storage, and switches. However, realizing FE‐AFM properties in a hybrid molecular material is difficult because ferroelectric and magnetic orders are commonly mutually exclusive. Here, we report an FE‐AFM multiferroic semiconductor [NH4(18‐crown‐6)]2[Mn(SCN)4] (NCMS) by supramolecular assembly approach via molecular rotor synthon [NH4(18‐crown‐6)] and inorganic magnetic module [Mn(SCN)4]. Interestingly, NCMS shows good ferroelectricity with a spontaneous polarization (Ps) of 5.94 μC cm−2 higher than most crown‐ether‐based ferroelectrics. Especially, the realization of antiferromagnetism is for the first time in the crown ether hybrid perovskite ferroic systems. Additionally, semiconductor NCMS displays an X‐ray radiation detection response with a large photo/dark current on‐off ratio (197). Our study not only gives a deep insight into understanding multiferroic properties but also provides a novel and efficient approach to realizing high‐performance hybrid multiferroic materials. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) ferroelectrics and multiferroics have attracted considerable scientific and technological interest in recent years due to the increasing demands for miniaturization and low energy consumption of electronic devices. At present, the research on 2D ferroelectrics and multiferroics is still focused on van der Waals materials, while the known bulk ferroelectric and multiferroic materials are mostly found in perovskite systems. The ability to prepare and transfer 2D perovskite oxides has provided unprecedented opportunities for developing ferroelectrics and multiferroics based on 2D perovskites. In this Perspective, we review the research progress on 2D ferroelectrics and multiferroics in inorganic perovskites in terms of different ferroelectric and magnetoelectric coupling mechanisms. The improper ferroelectricity and novel magnetoelectric coupling mechanisms discovered in 2D perovskites are emphasized, and then, the main challenges and future development direction are put forward. [ABSTRACT FROM AUTHOR]

In this study, in situ piezoelectricity was incorporated into the photoactive region to prepare a self-powered deep-ultraviolet photodetector based on a mixture of polyvinylidene fluoride (PVDF)@Ga2O3 and polyethyleneimine (PEI)/carbon quantum dots (CQDs). A ferroelectric composite layer was prepared using β-Ga2O3 as a filler, and the β-phase of PVDF was used as the polymer matrix. The strong piezoelectricity of β-PVDF can facilitate the separation and transport of photogenerated carriers in the depletion region and significantly reduce the dark current when the device is biased with an external bias, resulting in a high on/off ratio and high detection capability. The self-powered PD exhibited specific detectivity (D* = 3.5 × 1010 Jones), an on/off ratio of 2.7, and a response speed of 0.11/0.33 s. Furthermore, the prepared PD exhibits excellent photoresponse stability under continuous UV light, with the photocurrent retaining 83% of its initial value after about 500 s of irradiation. Our findings suggest a new approach for developing cost-effective UV PDs for optoelectronic applications in related fields. [ABSTRACT FROM AUTHOR]

Doped Hf 0.5 Zr 0.5 O 2 materials have drawn increasing attention due to the excellent ferroelectric properties, but the relevant research is just in the preliminary stage and the reported doped systems are rare. In this work, Ca doped Hf 0.5 Zr 0.5 O 2 (Ca:HZO) ferroelectric films were successfully fabricated via chemical solution deposition and investigated for the first time. It is observed that Ca doping induces a phase transformation from monoclinic to orthorhombic/tetragonal and then to monoclinic/tetragonal. The highest orthorhombic phase fraction is achieved in 2.5 mol% Ca doped HZO film, contributing to the optimum ferroelectric property with the largest remnant polarization of 14.00 μC/cm2 after 105 cycles. Additionally, the leakage current density is observed to decrease with increasing Ca content, which is mainly associated with the changes of grain size and surface roughness. As a result, the endurance is significantly improved in the Ca doped films, and an excellent endurance of 1010 cycles is achieved in the 2.5 mol% Ca doped film. These results suggest that Ca doping can enhance the ferroelectric and endurance properties of HZO films by optimizing the phase and morphological structure. [ABSTRACT FROM AUTHOR]

Materials with high dielectric constant exhibit excellent charge storage capacity, making them favorable solutions for next-generation dielectric capacitors. The glass system with the composition of 20BaTiO3-60V2O5-20Bi2O3 was prepared by conventional melt quenching technique. The glassy nature of the sample was confirmed by using DSC and XRD measurement while the existence of nano polar cluster inside the glass matrix was confirmed using HRTEM. The real permittivity (ε\) value shows two peaks in which the dielectric constant gradually increases up to a maximum value (εm) with the increase in temperature, and then it smoothly decreases, suggesting two phase transitions around 180 and 280 ◦ C. The measurements of the P–E hysteresis loop illustrated energy storage density of 124 mJ/cm3 and energy storage efficiency about 84% at room temperature. The glass sample shows superparaelectric behavior confirmed by the dielectric and P-E loop measurements. For high-energy storage applications, dipolar glasses have more outstanding potential than conventional ceramic dielectrics. Eventually, the glass matrix maintains high breakdown strength and can effectively stabilize nanocluster phases. So, we consider the present glass sample to be a good candidate for capacitive energy storage applications. [ABSTRACT FROM AUTHOR]

The recent discovery of sliding ferroelectricity opens up the field of 2D ferroelectricity. However, the limitation to switching the polarization due to the topological protection of the domain walls limits the potential of these heterostructures. Here, the switching of sliding ferroelectric bulk misfit layer compound (PbS)1.11VS2 crystals is studied using switching spectroscopy piezoresponse force microscopy. A large number of measured hysteresis loops can be efficiently analyzed using unsupervised machine‐learning tools. Different switching behavior of the domains is observed on different types of domain structures, and it is shown that full domain switching can be observed for the right type of dislocation structure in the PbS layer. [ABSTRACT FROM AUTHOR]

Magnetoelectric nanoparticles (NPs) present an important class of nanomaterials with a wide interest in piezocatalytic and biomedical applications. Herein, the results of magnetoelectric and magnetization measurements performed on core–shell NPs having magnetic core (MnFe2O4, MFO) and ferroelectric shell (Ba0.85Ca0.15Ti0.5Zr0.5O3, BCZT) synthesized by the microwave hydrothermal method are reported. Magnetic results are compared with the measurements on reference MFO NPs prepared under identical conditions. Detailed SQUID magnetometer measurements of the magnetization hysteresis loops M(H) down to 2 K reveal the existence of a clear exchange bias effect in pure MFO NPs attributed to the coexistence of ferromagnetic and antiferromagnetic short‐range interactions. When the magnetic core is covered by the thin ferroelectric BCZT shell, it is observed that 1) the shell suppresses the apparent bias effect and 2) induces an "extra" ferromagnetic magnetization at T < 20 K. The results indicate that this "extra" ferromagnetism has a 2D character and it is most likely related to the interface interactions between the MFO core and BCZT shell. Ferroelectric properties and strong magnetoelectric effect in core–shell NPs are revealed via piezoresponse force microscopy under magnetic field. The mechanisms of the observed effects are discussed. [ABSTRACT FROM AUTHOR]

Since the study of short‐wave ultraviolet nonlinear optical crystals based on the quasi‐phase‐matching principle will effectively expand the development field of nonlinear optical materials, it is urgent to achieve their directional design. Here, it is proposed and implemented on account of the hexagonal wurtzite structure. Thus, the LiRbSeO4 crystal is obtained with [SeO4] groups as the main tetrahedra and [LiO4] as the separation. It exhibits a wide transparency window (0.22–5.57 µm) and an excellent nonlinear optical effect (≈1.7 × KH2PO4), which originates from the synergy of distorted tetrahedral groups and their uniform arrangement. More importantly, the LiRbSeO4 crystal is confirmed to be a ferroelectric with a typical polarization‐electric field hysteresis loop (a coercive field of 27.71 kV cm−1, a remanent polarization of 8.60 µC cm−2 at 373 K). Its ferroelectricity is further identified by the domain engineering studies, involving piezoelectricity and the chirality. Besides, ferroelectricity is attributed to the ordered arrangement of tetrahedra with the polarization reversal involving atomic displacements. Therefore, the LiRbSeO4 crystal is a promising short‐wave ultraviolet nonlinear optical candidate based on the quasi‐phase‐matching principle. This work also provides a new horizon for the design of nonlinear optical crystals. [ABSTRACT FROM AUTHOR]

Barium strontium titanate (BST) is a perovskite material, which is used directly in various applications including thermistors, electromechanical actuators, sensors and ceramic capacitors. Here, we have investigated the impact of dopant (Mn and Co) on synthesized BST nanoparticles and its morphological, structural, vibrational and optical properties have been investigated through scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), FTIR and Raman spectroscopies. SEM image showed the nearly spherical grain for pure BST and doped (Mn and Co) BST samples. The estimated particles were strongly influenced by different dopants, in addition, Mn-doped BST showed maximum grain growth for pure and Co-doped BST samples. XRD patterns have been employed to investigate the microstructural parameters (phase, lattice, crystallite size, strain, dislocation density, etc.). The crystallite sizes have been estimated using the Scherrer formula, showing maximum crystallite size for Mn-doped BST ceramics. Recorded FTIR spectra showed the transmission peak, which is centred at wavenumber of 470 cm−1 (pure BST), was shifted to 1250 cm−1 with Mn-doped BST. Raman spectra exhibited the increased number of modes from pure BST to Mn-doped BST sample. PL showed the emissions bands, which were observed at 602–659 nm. Here, the peak shifted towards higher wavelength from pure BST to Mn-doped BST (red shifting from pure to Mn-doped BST). It revealed that the prepared samples can be employed as suitable photoluminar material. [ABSTRACT FROM AUTHOR]

The common feature of non‐ergodic systems is an internal timescale that greatly exceeds the external observational timescale tobs${t}_{obs}$. This kinetic state of broken ergodicity occurs in many systems, with profound thermodynamic implications. In this work, we present a review of non‐ergodic physical systems focused on the common origins of non‐ergodic behavior across diverse material systems. We begin with a theoretical discussion of energy landscapes and two treatments of thermodynamics in broken ergodic systems. We then discuss several characteristic material classes that exhibit non‐ergodic behavior, describing the process of ergodic breakdown and its signatures for each. The disordered nature and frustration of different energetic interactions in the example systems are discussed as the possible origin of non‐ergodic dynamics. We conclude with several considerations that can assist in the identification of non‐ergodic behavior. This review intends to unify the behavior of a diverse group of physical systems with a common description to aid future discussions between these fields of study. [ABSTRACT FROM AUTHOR]

Hybrid organic-inorganic metal halides (HOMHs) have attracted tremendous interest in the past decades due to their diverse functional properties, such as ferroelectricity and luminescence. However, although a large number of ferroelectric HOMHs and luminescent HOMHs have been reported, the HOMH ferroelectrics with white-light emission remain very sparse. Here, for the first time, by using the Z/E isomeric organic cation, we designed a cadmium-based HOMH ferroelectric [EE-PMU]CdCl4 (EE-PMU = pyridin-2-ylmethanamide muconate) with broadband white-light emission. In contrast to the [ZZ-PMU]CdCl4 with centrosymmetric crystal structure at room temperature, [EE-PMU]CdCl4 adopts the polar crystal symmetry, which shows piezoelectricity with a piezoelectric coefficient of d33 up to 19 pC/N and ferroelectricity with the saturated polarization of 1.52 µC/cm2. Moreover, [EE-PMU]CdCl4 exhibits a broadband white-light emission with an ultra-high color rendering index of 91 under UV excitation, which is related to the severely distorted [CdCl4]2− tetrahedron in the structure. To our knowledge, [EE-PMU]CdCl4 is the first example of Z/E isomeric cation-designed HOMH ferroelectric and the first cadmium halide white-light emissive ferroelectric. This finding paves a new way for the design of organic-inorganic molecular ferroelectrics with white-light emission. [ABSTRACT FROM AUTHOR]

Cluster-assembled materials have long been pursued as they can create some unprecedented and desirable properties. Herein, we assemble a class of one-dimensional (1D) ReNX4 (X = F, Cl, Br and I) and MF5 (M = V, Nb and Ta) nanowires by covalently linking their superatomic clusters. These assembled 1D nanowires exhibit outstanding energetic and dynamic stabilities, and hold sizable spontaneous polarization, low ferroelectric switching barriers and high critical temperature. Their superior ferroelectricity is originated from d0-configuration transition metal ions generated by the hybridization of empty d orbitals of metal atoms and p orbitals of non-metal atoms. These critical insights pave a new avenue to fabricate 1D ferroelectrics toward the development of miniaturized and high-density electronic devices using building blocks as cluster with precise structures and functionalities. [ABSTRACT FROM AUTHOR]

In this study, a passive control strategy of inductive power transfer (IPT) using ferroelectric multilayer ceramic chip capacitors (MLCCs) is presented. The required system parameters, i.e., ferroelectric hysteresis, frequency of the IPT, and voltage range across the MLCCs are reported. The receiver circuit consists only of a parallel resonant circuit, a halfwave rectifier and a load; the passive control of the IPT is achieved exclusively by the nonlinear properties of the ferroelectric MLCCs. The stabilization of the secondary output voltage ULoad at constant load is experimentally evaluated for an inductive coupling factor k between 10 % and 30 % for three nonlinear MLCCs #1, #2 and #3. With our proposed passive control strategy ULoad is maintained at -1.2 % and +0.6 % around a median value of 17.3 V (17.1 - 17.4 V) for k ∈ [20 %, 30 %] using MLCC #1, ±0.9 % around a median value of 11.2 V (11.1 - 11.3 V) for k ∈ [10 %, 18 %] using MLCC #2, and -1.6% and +2.6 % around a median value of 5.03 V (4.95 - 5.16 V) for k ∈ [16 %, 30 %] using MLCC #3. The proposed control principle is particularly advantageous for highly miniaturized microimplants, as it allows IPT control without additional semiconductors, sensors and vulnerable communication channels. [ABSTRACT FROM AUTHOR]

This work presents dynamic state writing by combining ferroelectric (FE) polarization together with charge injection (CI) on Si-based ferroelectric MOSFETs as a novel approach for non-volatile memory design. FE capacitors are non-destructively integrated in the Back-End-of-Line (BEOL) with Si MOSFETs to create FE-Metal-FETs (FeMFETs). We explore the FE/MOS area ratio (AR) as a critical design parameter, particularly in the context of dynamic writing processes, where various voltage pulse trains are applied for analog potentiation and depression of the memory state. AR significantly influences both the electric field distribution over the FE and the extent of CI from the top electrode. Constant-pulse writing schemes enable analog threshold voltage modulation by considering the AR, with reduced voltages and faster operation for smaller ARs. Retention of intermittent states written by FE polarization combined with CI is demonstrated, illustrating the stability and effectiveness of FeMFET devices and AR optimization for memory applications.

κ-Ga2O3 has been predicted to be a potential ferroelectric material. In this work, undoped Ga2O3 films were grown by either plasma-enhanced atomic layer deposition (PEALD) or metal organic chemical vapor deposition (MOCVD) on platinized sapphire substrates. 50 nm thick PEALD films with a mixture of κ-Ga2O3 and β-Ga2O3 had a relative permittivity of ∼27, a loss tangent below 2%, and high electrical resistivity up to ∼1.5 MV/cm. 700 nm thick MOCVD films with predominantly the κ-Ga2O3 phase had relative permittivities of ∼18 and a loss tangent of 1% at 10 kHz. Neither film showed compelling evidence for ferroelectricity measured at fields up to 1.5 MV/cm, even after hundreds of cycles. Piezoresponse force microscopy measurements on bare κ-Ga2O3 showed a finite piezoelectric response that could not be reoriented for electric fields up to 1.33 MV/cm. [ABSTRACT FROM AUTHOR]

We conducted a comprehensive investigation on the influence of TiN thickness and stress on the ferroelectric properties of Hf 0.5 Zr 0.5 O 2 thin films. TiN top electrode layers with varying thicknesses of 2, 5, 10, 30, 50, 75, and 100 nm were deposited and analyzed. It was observed that the in-plane tensile stress in TiN films increased with the thickness of the TiN top electrode. This is expected to elevate the tensile stress in the Hf 0.5 Zr 0.5 O 2 film, consequently leading to an enhancement in ferroelectric polarization. However, the effect of stress on the ferroelectric behavior of Hf 0.5 Zr 0.5 O 2 films exhibited distinct stages: improvement, saturation, and degradation. Our study presents novel findings revealing a saturation and degradation phenomenon of in-plane tensile stress on the ferroelectric properties of polycrystalline Hf 0.5 Zr 0.5 O 2 films, thereby partially resolving the discrepancies between experimental observations and theoretical predictions. The observed phase transformation induced by tensile stress in Hf 0.5 Zr 0.5 O 2 films played a crucial role in these effects. Furthermore, we found that the impact of the TiN top electrode thickness on other factors influencing ferroelectricity, such as grain size and oxygen vacancies, was negligible. These comprehensive results offer valuable insights into the influence of stress and TiN top electrode thickness on the ferroelectric behavior of Hf 0.5 Zr 0.5 O 2 films. [ABSTRACT FROM AUTHOR]

Ferroelectric (FE) electrocaloric materials research has been blossoming worldwide for solid-state refrigeration and potential cooling systems replacing thermoelectric Peltier coolers in microelectronics. In this work, we report the outcomes from a systematic study of combined phase transition (thermodynamics) based on the phenomenological Landau theory and distributed electric field (electrostatics of thin film interfaces) in FE bilayer films. Specifically, the compositional variation of ferroelectric bilayers results in broken spatial inversion symmetry leading to asymmetric thermodynamic potentials due to a combination of normal (first- and second-order phase transition) and relaxor (dispersive dielectric constant) ferroelectric behaviors devised for efficient electrocaloric cooling effects. Extensive theoretical analyses conducted for bilayers consisting of insulating materials highlight modified phase transition temperature behavior and self-poling by effective electric field amplification arising due to bilayers' electrostatic coupling yielding significant changes in isothermal entropy (ΔS) and adiabatic temperature (ΔT). The theoretical calculation insights supported with experimental results signify, through case studies for a combination of materials experimental parameters, that amplification of the local electric field and materials engineering maximize the number of coexisting phases at or away from the morphotropic phase boundary of constituent layers in bilayer thin film architectures, which can be applicable toward other classes of materials and multilayer systems. These are effective ways for efficient cooling, in general, and for microelectronics thermal management either directly or by developing a thermal switch with phase change materials integrated with thermoelectric coolers for residual heat dissipation, both at the system and on-chip levels. [ABSTRACT FROM AUTHOR]

While the influence of various fabrication parameters during deposition on the ferroelectricity of hafnium oxide has been extensively studied, the effect of different atmospheres on the actual switching process has not yet been investigated. In this work, we characterized the ferroelectric properties of undoped hafnium oxide prepared by reactive sputtering under three different atmospheres: dry oxygen/nitrogen, wet nitrogen, and vacuum conditions. We found a significant correlation between dry and wet atmospheres and resulting polarization. Specifically, we observed a direct effect on ferroelectric switching when the film was exposed to dry atmospheres and vacuum, resulting in a higher electric field necessary to initialize the wake-up effect due to an initial imprint effect. Increasing the amount of wet nitrogen during switching decreased the imprint and lowered the necessary voltage required for the wake up. We present a simple model that explains and discusses the incorporation of moisture and its resulting consequences on the ferroelectric properties of hafnium oxide. Additionally, kinetic Monte Carlo simulations showed that the addition of protons to the oxide thin film leads to a lowering of the potential and to a redistribution of protons and oxygen vacancies, which reduces the initial imprint. [ABSTRACT FROM AUTHOR]

Hf0.5Zr0.5O2 (HZO) is a promising candidate for low-power non-volatile memory due to its nanoscale ferroelectricity and compatibility with silicon-based technologies. Stress and oxygen vacancy (VO) are key factors that impact the ferroelectricity of HZO. However, their combined effects have not been extensively studied. In this study, we investigated the impact of the VO content on HZO thin films' ferroelectricity under different electrode stresses by using TiN and tungsten (W) top electrodes and controlling ozone dose time during HZO deposition. The HZO thin films with W top electrodes exhibit elevated stress levels and a greater abundance of orthorhombic/tetragonal phases, and the HZO thin films with TiN top electrode shows an increase in the monoclinic phase with increasing ozone dose time. The residual polarization (Pr) of the capacitors with TiN and W top electrodes displayed different or even opposing trends with increasing ozone dose time, and the VO content decreases with increasing ozone dose time for both sets of capacitor samples. We propose a model to explain these observations, considering the combined influence of electrode stresses and VO on the free and formation energy of the crystalline phase. Increasing the VO content promotes the transformation of the tetragonal phase to the orthorhombic phase in HZO films with TiN top electrodes, and with W top electrodes, a higher VO content prevents the tetragonal phase from transforming into the orthorhombic/monoclinic phase. Additionally, an alternative explanation is proposed solely from the perspective of stress. These findings provide valuable insights into the regulation of ferroelectricity in HZO thin films. [ABSTRACT FROM AUTHOR]

Complex-oxide superlattices provide a pathway to numerous emergent phenomena because of the juxtaposition of disparate properties and the strong interfacial interactions in these unit-cell-precise structures. This is particularly true in superlattices of ferroelectric and dielectric materials, wherein new forms of ferroelectricity, exotic dipolar textures, and distinctive domain structures can be produced. Here, relaxor-like behavior, typically associated with the chemical inhomogeneity and complexity of solid solutions, is observed in (BaTiO3 )n /(SrTiO3 )n (n = 4-20 unit cells) superlattices. Dielectric studies and subsequent Vogel-Fulcher analysis show significant frequency dispersion of the dielectric maximum across a range of periodicities, with enhanced dielectric constant and more robust relaxor behavior for smaller period n. Bond-valence molecular-dynamics simulations predict the relaxor-like behavior observed experimentally, and interpretations of the polar patterns via 2D discrete-wavelet transforms in shorter-period superlattices suggest that the relaxor behavior arises from shape variations of the dipolar configurations, in contrast to frozen antipolar stripe domains in longer-period superlattices (n = 16). Moreover, the size and shape of the dipolar configurations are tuned by superlattice periodicity, thus providing a definitive design strategy to use superlattice layering to create relaxor-like behavior which may expand the ability to control desired properties in these complex systems.

Hybrid organic–inorganic formate perovskites, AB(HCOO)3, are a large family of compounds that exhibit a variety of phase transitions and diverse properties, such as (anti)ferroelectricity, ferroelasticity, (anti)ferromagnetism, and multiferroism. While many properties of these materials have already been characterized, we are not aware of any study that focuses on the comprehensive property assessment of a large number of formate perovskites. A comparison of the properties of materials within the family is challenging due to systematic errors attributed to different techniques or the lack of data. For example, complete piezoelectric, dielectric, and elastic tensors are not available. In this work, we utilize first-principles density functional theory based simulations to overcome these challenges and to report structural, mechanical, dielectric, piezoelectric, and ferroelectric properties of 29 formate perovskites. We find that these materials exhibit elastic stiffness in the range 0.5–127.0 GPa; highly anisotropic linear compressibility, including zero and even negative values; dielectric constants in the range 0.1–102.1; highly anisotropic piezoelectric response with the longitudinal values in the range 1.18–21.12 pC/N; and spontaneous polarizations in the range 0.2–7.8 μC/cm2. Furthermore, we propose and computationally characterize a few formate perovskites that have not been reported yet. [ABSTRACT FROM AUTHOR]

Tailoring the specific properties to practical applications by structural modification is of vital importance for the envisioned development of two-dimensional ferroelectric materials. Herein, a comprehensive investigation on the effects of single doping on the ferroelectric properties and electronic transport in a monolayer of α-In2Se3 was carried out via the combination of first-principles density functional theory calculations and electron–phonon coupling simulations. Our results show that single-doping in In2Se3 can reduce effective mass of carriers and thereby enhance the high carrier mobility potential of the material. Moreover, the ferroelectric phonon mode in single-doped In2Se2X features a lower scattering rate, associating with the single-doping atom, and indicates reduced hindrance to carrier transport during ferroelectric switching. Compared to pristine In2Se3, the obtained smaller ferroelectric barriers (<1 eV) of single-doped ones promote more promising ferroelectricity from the analysis of the ferroelectric soft mode. Interestingly, the observed variations in ferroelectric behaviors resulting from doping of different elements highlight the significance of single-doping in modifying the ferroelectric properties of monolayers. Furthermore, strain engineering results reveal that single doping obviously affects the dependence of gap on strains: linear relationship for doping ones and nonlinearity for pristine one. Our study provides valuable insights into achieving higher carrier mobility in these critical materials. [ABSTRACT FROM AUTHOR]

This paper presents the experimental evidence of reversible insulator–metal transition (IMT) in thin-film amorphous molybdenum trioxide (MoO3) induced by electric fields of just a few volts. The presence of oxygen vacancies in MoO3 is considered to play a significant role in the reported reversible IMT. The oxygen vacancies not only impact MoO3 stoichiometry but also the optical bandgap. The subthreshold slope for IMT in 10 nm-thick MoO3-based devices is 48.3 mV/decade, which represents a transition from an insulator to a metallic state, and the electric field threshold for such a transition was found to be equal to 0.034 V/Å. Following the IMT in MoO3, there are six orders of magnitude differences between the resistivity of the insulator state (27.5 M Ω at −9 V) and the metallic state (80 Ω between +5 and +9 V). In addition, we reported stabilization of a nanocrystalline hexagonal MoO3 (h-MoO3) phase in thicker MoO3 (150 nm-thick) in the presence of oxygen vacancies that behave as a wide bandgap (3.1 eV) ferroelectric semiconductor with a coercive field of about 50 kV/cm, a saturation polarization of about 30 μC/cm2, and a remanent polarization of about 10 μC/cm2. This ferroelectricity in nanocrystalline h-MoO3 (150 nm-thick) remains stable even after 8 months of storage of the sample in ambient conditions, with remanent polarization increasing up to 20 μC/cm2. These are unexpected results from MoO3. [ABSTRACT FROM AUTHOR]

Sulfur is a promising anion dopant for exploring exotic physical phenomena in complex perovskite oxides. However, sulfurization to the epitaxial single-crystal oxide thin films with high crystallinity is experimentally challenging due to the volatility of sulfur element; thus, sulfurization effects on the associated properties have been scarcely studied. Here, we demonstrate an enhancement of ferroelectric polarization of epitaxial BaTiO3 thin films by sulfur doping. Initially, the epitaxial BaTiO3 thin films with high crystallinity were grown by pulsed laser deposition (PLD). Then, sulfurization to epitaxial BaTiO3 films was performed using a precursor of thiourea (CH4N2S) solution via a spin-coating technique. The crystalline structure of sulfurized BaTiO3 films was identified by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). The structural distortion with the elongated out-of-plane lattice constant was observed in the sulfurized BaTiO3 films. Atomic force microscopy (AFM) analyses also confirmed the surface morphology of films after sulfurization. Interestingly, we found an enhanced ferroelectric polarization in sulfur-doped BaTiO3 films accompanying the improved tetragonality in the crystal structure after sulfurization. The increments in the remnant (~34.8%) and saturated (~30.6%) polarizations of sulfurized BaTiO3 films were obtained in comparison with pure BaTiO3 films. Our work could be a primary study for a thorough understanding of the sulfur doping effect in perovskite oxides, opening up the potential of oxysulfide materials.

Understanding surface collective dynamics in quantum materials is crucial for advancing quantum technologies. For example, surface phonon modes in quantum paraelectrics are thought to be essential in facilitating interfacial superconductivity. However, detecting these modes, especially below 1 terahertz, is challenging because of limited sampling volumes and the need for high spectroscopic resolution. Here, we report surface soft transverse optical (TO1) phonon dynamics in KTaO3 and SrTiO3 by surface-sensitive spintronic terahertz spectroscopy that can sense the collective modes only a few nanometers deep from the surface. In KTaO3, the TO1 mode softens and sharpens with decreasing temperature, leveling off at 0.7 terahertz. In contrast, this mode in SrTiO3 broadens substantially below the quantum paraelectric crossover and coincides with the hardening of a sub-milli-electron volt phonon mode related to the antiferrodistortive transition. These observations that deviate from their bulk properties may have implications for interfacial superconductivity and ferroelectricity. The developed technique opens opportunities for sensing low-energy surface collective excitations. [ABSTRACT FROM AUTHOR]

Tunable ferroelectric film capacitors play an important role in tunable microwave devices and filter systems due to their high dielectric constant, low loss, and high dielectric tunability. However, there is a trade-off between low loss and high tunability, which limits further enhancement of dielectric performance. Here, we propose an ultra-tunable capacitor by designing a Ba0.7Sr0.3TiO3 (BST)–semiconductor heterostructure. In the tunable capacitor, the BST film is fabricated directly on p-type silicon substrates by magnetron sputtering, and a heterostructure layer is constructed. The coupling effects between the semiconductor depletion layer capacitance and the BST capacitance produce higher capacitance tunability than a traditional sandwich BST capacitor. Based on the coupling effects, a metal–ferroelectric–semiconductor–ferroelectric–metal capacitor is developed, which enables the capacitor to operate under both negative and positive biases, which has an n value (n = C max / C min ) of 90 with 40 V bias voltage and a maximum Q of 1000. The results offer a potential approach to designing high-performance tunable capacitors on silicon with BST film that could build tunable filters for information processing in communication systems. [ABSTRACT FROM AUTHOR]

CuInP2S6 (CIPS) is an emerging 2D ferroelectric material known for disrupting spatial inversion symmetry due to Cu(I) position switching. Its ferroelectricity strongly relies on the Cu(I) atom/ion occupation ordering and dynamics. Nevertheless, the accurate Cu(I) occupations and correlated migration dynamics under the externally applied energy, which are key to unlocking ferroelectric properties, remain controversial and unresolved. Herein, an atomic-level direct imaging through aberration-corrected scanning transmission electron microscopy is performed to precisely trace the Cu(I) dynamic behaviours under electron-beam irradiation along (100)-CIPS. It clearly demonstrates that Cu(I) possesses multiple occupations, and Cu(I) could migrate to the lattice, vacancy, interstitial and interlayer sites between the InS6 octahedral skeletons of CIPS to form local CuxInP2S6 (x = 2-4) structure. Cu(I) multi-occupations induced lattice stress results in a layer sliding along the b-axis direction generating a sliding size of 1/6 b lattice constant. The CuxInP2S6 (x = 2-4) exists in a type of dynamic structure, only metastable with electron dose over 50 e− Å−2, thus generating a dynamic process of C u x In P 2 S 6 (x = 2 − 4) ⇌ CuIn P 2 S 6 , a completely unreported phenomenon. These findings shed light on the unveiled mechanism underlying Cu(I) migration in CIPS, providing crucial insights into the fundamental processes that govern its ferroelectric properties. The authors demonstrate that Cu(I) possesses multiple occupations, and Cu(I) migrate to the lattice, vacancy, interstitial and interlayer sites between the InS6 octahedral skeletons of CuInP2S6 to form local CuxInP2S6 (x = 2-4) structure. [ABSTRACT FROM AUTHOR]

Ferroelectricity, band topology, and superconductivity are respectively local, global, and macroscopic properties of quantum materials, and understanding their mutual couplings offers unique opportunities for exploring rich physics and enhanced functionalities. In this mini‐review, the attempt is to highlight some of the latest advances in this vibrant area, focusing in particular on ferroelectricity‐tuned superconductivity and band topology in 2D materials and related heterostructures. First, results from predictive studies of the delicate couplings between ferroelectricity and topology or superconductivity based on first‐principles calculations and phenomenological modeling are presented, with ferroelectricity‐enabled topological superconductivity as an appealing objective. Next, the latest advances on experimental studies of ferroelectricity‐tuned superconductivity based on different 2D materials or van der Waals heterostructures are covered. Finally, as perspectives, schemes are outlined that may allow to materialize new types of 2D systems that simultaneously harbor ferroelectricity and superconductivity, or that may lead to enhanced ferroelectric superconductivity, ferroelectric topological superconductivity, and new types of superconducting devices such as superconducting diodes. [ABSTRACT FROM AUTHOR]

In this paper, the calcium-doped nickel-zinc nano-ferrites [Ni 0.5 Zn 0.5 Ca x Fe 2-x O 4 ; x = 0.00, 0.10, and 0.30] were prepared using the chemical co-precipitation synthesis route and studied for switching field high-frequency device applications. The structural analysis has been completed by analyzing X-ray diffraction (XRD) patterns. The Rietveld refined XRD patterns confirmed the formation of cubic spinel structure of Ca2+ substituted nickel-zinc ferrites. The detection of metal-oxygen bonds present at A and B lattice sites has been unveiled by Fourier transform infrared (FTIR) spectroscopy. The morphological studies obtained through FESEM (Field emission scanning electron microscopy) analysis showed a reduction in the particle size from 70 nm to 53 nm when the concentration of Ca2+ ions in Ni-Zn ferrites was increased. Energy dispersive spectra (EDS) confirmed the presence of elements present in the prepared composition. The structure of a cubic spinel-shaped unit cell has been verified from three active prominent Raman modes (A 1g , A 2g , and T 2g). Diffuse-reflectance spectroscopy (DRS) exhibits the increment in the bandgap values (from 1.55 eV to 1.63 eV) which helps fabricate highly efficient photovoltaic devices. The ferroelectric measurements yielded a rise in polarization values from 1.461 μC/cm2 to 18.228 μC/cm2 for 10 % Ca2+ ion substitution. The tangent loss values declined from 24 to 3 in Ni-Zn ferrites upon substituting Ca2+ ions. The Vibrating sample Magnetometer (VSM) technique found the increment in the saturation magnetization (M s) values from 34.724 emu/g to 54.662 emu/g on substituting up to 30 % Ca2+ ions in Ni-Zn ferrites. These obtained results support the material in switching field distribution for high-frequency applications. The results exhibited that the prepared samples can be applicable for switching devices, filters, and microwave absorption devices. The results revealed the maximum frequency between 12 and 18 GHz which is useful for Ku band absorption. [ABSTRACT FROM AUTHOR]

The concept of ferroelectric polarons is proposed to partially explain the exceptional optoelectronic properties observed in lead halide perovskites (LHPs). It is intriguing but unclear how this proposal, which involves local or transient polarizations, applies in general to 2D LHPs with long‐range ferroelectricity. Here, this work presents a pioneering time‐domain experimental investigation of polarons in ferroelectric (IA)2(MA)2Pb3Br10 (IMPB; IA is isoamylammonium and MA is methylammonium) using transient absorption spectroscopy. Compared to non‐ferroelectric LHPs, IMPB exhibits several distinct polaronic properties closely associated with macroscopic polarizations of ferroelectricity, including a prolonged polaron formation time (≈1.1 ps), a Stark splitting of the bleaching (≈63 meV), and a giant polaron Mott density (≈7.6 × 1018 cm−3). These findings broaden the realm of 2D polaron systems and reveal the decisive role of static/unidirectional polarizations on polaron physics in 2D LHPs. [ABSTRACT FROM AUTHOR]

In this work, the transverse size effect of the new-generation relaxor ferroelectric Pb(In 1/2 Nb 1/2)O 3 -Pb(Mg 1/3 Nb 2/3)O 3 -PbTiO 3 (PIMNT) thin film was studied by finite element method, aiming to revealing the lateral size and shape dependence of the piezoelectric, dielectric, and pyroelectric behavior for guiding one- and two-dimensional integrated array sensor applications. The results indicated that as the aspect ratio (width to thickness ratio) decreased from 100 to 0.01, for both one-dimensional rectangular and two-dimensional square PIMNT array elements, a sharp increase in piezoelectric and dielectric constants could be observed for the PIMNT with <001> direction while a slight increase could be found for those along <111> orientation, exhibiting a strong orientation dependence. In comparison, the PIMNT with <110> direction exhibited strong shape dependence. The piezoelectric and dielectric constants of <110>-oriented square element increased more remarkably than those of the rectangular one. The pyroelectric coefficients of PIMNT exhibited weak shape dependence, decreasing from 8.5 × 10−4 C/(m2·K) to about 8.0 × 10−4 C/(m2·K) for both element shapes with transverse size decreasing. These findings give insight into the transverse size and shape effect on the new-generation PIMNT thin film and provide a guide for its design in one- and two-dimensional piezoelectric and pyroelectric array sensor applications. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) ferroelectricity has attracted great interest for its potential to develop various flexible and stretchable ultra-thin smart devices. The ultra-thin nature of 2D materials makes domain control very challenging, as an external electric field inevitably leads to leakage currents and even material breakdown. Therefore, it is highly desirable to explore more practical and feasible methods to control ferroelectric (FE) domains. In this work, based on the coupling between the ferroelasticity and ferroelectricity in 2D multiferroic materials, we propose a strategy to control the FE polarization direction and domain through the strain engineering. Taking β′-In2Se3 as an example, we revealed the regulation mechanism of the uniaxial strain and shear strain on the ferroelasticity and ferroelectricity. We found that the polarization direction of FE β′-In2Se3 is tunable by manipulating the strain, which demonstrates the feasibility to tailor the FE single domain as well as domain wall (DW) patterns. In addition, we also found that the angle between the stretching direction and the DW plays a crucial role in regulating the DW type, which provides an important reference for controlling DW. Therefore, the strain engineering not only provides an alternative solution for forming large-sized single domain FE materials, but also enable customized FE domain structures for DW electronics by ingeniously designing strain patterns. [ABSTRACT FROM AUTHOR]

Scandium‐doped aluminium nitride (ScxAl1‐xN)has made extensive progress in its applicationfor non‐volatile ferroelectric field effect transistors (FeFETs). However, ScAlN FeFET studies have mainly focused on memory devices based on n‐ and p‐type channel. Photodetectors based on ScAlN ferroelectric gatehave rarely been reported. Here, a FeFET device consisting of a metallic channel material, SnSe, and a ferroelectric gate material, Sc0.25Al0.75N is presented. Due to the different energy levels of Sc0.25Al0.75N and SnSe, a potential barrier is formed at the interface between them, which regulates the dark current and photoresponsivity of the heterostructure; meanwhile, the interfacial potential barrier is changed under three polarization states of Sc0.25Al0.75N. As a result, dark current of the device with Sc0.25Al0.75N gate is reduced by 104, on/off ratio is increased by 40 times, and the photoresponsivity is enhanced to 1 × 104 A W−1 compared with that of SiO2 gate; Moreover, on/off ratio of the devicesunder the positively polarized state is increased by nearly 103 underillumination; under the negatively polarized state, photoresponsivity reaches 5.4 × 105 and 3.1 × 104 A W−1 under illumination. This work demonstrates the feasibility of Sc0.25Al0.75N applied in FeFET photodetectors and opens up the possibility of developing ScAlN‐based optoelectronic devices. [ABSTRACT FROM AUTHOR]

New xYFeO 3 – (1-x) BiFeO 3 (0.0 ≤ x ≤ 1.0) multiferroic composites were prepared successfully via the chemical co-precipitation followed by high energy mechanical blending. For the structural analysis, assessment of phase purity, and characterization of oxidation states, XRD, FTIR and XPS methods were utilized, respectively. Furthermore, morphological investigations and elemental distribution within the composite samples were elucidated through FESEM and TEM imaging techniques. The VSM results indicated that the values of M s and M r increase alternately from 0.553emu/g and 0.049emu/g to 1.210emu/g and 0.166emu/g, respectively, with an increase in the YFO content from 20 % to 80 %. These values of M s do not follow a linear combination of the base phases, and the magnetization of each composite sample is accompanied by an additional value. This additional value may arise from the residual strain and interfacial magnetic and electrical interactions between the parent phases. The measurements of dielectric properties disclosed that the behavior of the samples follows the Maxwell-Wagner polarization. Moreover, the values of ε′ at the frequency of 200 Hz increased from 149 to 303 as the BFO content rose from 20 % to 80 %. In addition, the lowest recorded tanδ value was 0.56 for the 6Y4B sample at 200 Hz. Furthermore, the conductivity measurements showed that the behavior of all samples follows Johnscher's power law. • The phase-pure YFeO 3 /BiFeO 3 nanocomposites with well-dispersed particles were synthesized using the reverse co-precipitation. • The magnetostriction effect in BFO and the ferroelectric properties of YFO altered the overall magnetization in the system. • The significant enhancement of the coercive field relative to the original phases was emphasized in all composite samples. • The rise in the YFO content in the composite specimens led to a drop in the dielectric constant. [ABSTRACT FROM AUTHOR]