Electric Polarization Research Articles

Periodic quantum well mediated oriented charge separation in Cd0.3Zn0.7S twin crystal towards optimized photocatalytic hydrogen evolution

Interface engineering is vital for promoting charge separation in photocatalysis. Herein, a twin crystal interface in Cd0.3Zn0.7S is engineered, which leads to a variation of the electric polarization along the interface and the formation of a periodic quantum well along z axis. The periodic quantum well could effectively facilitate the oriented charge separation and significantly reduce the diffusion distance simultaneously. Density functional theory (DFT) calculations confirm that Cd0.3Zn0.7S twin crystal possesses a relative low work function and an appropriate hydrogen adsorption Gibbs free energy (ΔGH*), making each step of the cascaded hydrogen evolution reactions optimized. As a result, the resultant twin crystal exhibits an excellent visible light photocatalytic hydrogen evolution rate (13148.98 μmol·g−1·h−1), which is almost 10 and 30 times higher than those of CdS and ZnS. Importantly, it also shows a good stability because of the formation of twin crystal interface. In addition, the introduction of S vacancy defect results in narrowing the band gap and extending the photo-response to long wavelength region. Such a twin crystal interface engineering strategy provides a basic guideline for designing high-efficient photocatalysts with tunable electric polarization.

Two-dimensional Janus MXTe (M = Hf, Zr; X = S, Se) piezoelectrocatalysts: a comprehensive investigation of its electronic, synthesis feasibility, electric polarization, and hydrogen evolution reaction activity

Abstract We computationally investigated potential piezoelectrocatalysts, two-dimensional (2D) Janus MXTe (M = Hf, Zr; X = S, Se). The structural and electronic properties, synthesis feasibility, piezoelectric properties, and hydrogen evolution reaction were calculated. Our results showed that these 2D Janus MXTe are narrow-gap semiconductors, indicating great conductivity for electrocatalysis. The feasibility of synthesis was comparable to the already synthesized Janus materials. To exhibit a piezoelectrocatalytic effect, the material has to be piezoelectric and catalytically effective simultaneously. As the Janus structure breaks the centrosymmetry, the considered MXTe are intrinsically piezoelectric. We therefore calculated the dipole moments and the variation of out-of-plane polarization upon strain. The computed piezoelectric coefficient e 31 is within the same order of magnitude as that of other Janus 2D materials. Finally, although pristine 2D Janus MXTe were inert to hydrogen evolution reaction, incorporation of single-atom defects was found to boost hydrogen adsorption significantly. The catalytic efficacy can be further tuned by biaxial tensile strain, effectively controlling the Gibbs free energy of adsorption to be close to the thermoneutral value that is indicative of an excellent hydrogen evolution reaction activity, at least for ZrSTe Janus monolayer. In summary, this work proposed and comprehensively investigated a new class of possible piezoelectrocatalysts, 2D Janus materials, which is feasible to be synthesized, catalytically effective, and has great conductivity.

Periodic Domain Inversion in Single Crystal Barium Titanate‐on‐Insulator Thin Film

AbstractExperimentally achieving the first‐ever electric field periodic poling of single crystal barium titanate oxide (BTO, or BaTiO3) thin film on‐insulator is reported. Owing to the outstanding optical nonlinearities of BTO, this result is a key step toward achieving quasi‐phase‐matching (QPM). First, the BTO thin film is grown on a dysprosium scandate substrate using pulsed laser deposition with a thin layer of strontium ruthenate later serving as the bottom electrode for poling. The characterization of the BTO thin film using x‐ray diffraction (XRD) and piezo‐response force microscopy to demonstrate single crystal, single domain growth of the film that enables the desired periodic poling, are presented. To investigate the poling quality, both non‐destructive piezo force response microscopy and destructive etching‐assisted scanning electron microscopy (SEM) are applied, and it is shown that high quality, uniform, and intransient poling with 50% duty cycle and periods ranging from 2 µm to 10 µm is achieved. The successful realization of periodic poling in BTO thin film unlocks the potential for highly efficient nonlinear processes under QPM that seemed far‐fetched with prior polycrystalline BTO thin films which predominantly relied on efficiency‐limited random or non‐phase matching conditions and is a key step toward integration of BTO photonic devices.

Bioactive Ion-Confined Ultracapacitive Memristors with Neuromorphic Functions.

The field of bioinspired iontronics, bridging electronic devices and ionic systems, has multiple biological applications. Carbon-based ultracapacitive devices hold promise for controlling bioactive ions via electric double layers due to their high-surface-area and biocompatible porous carbon electrodes. However, the interplay between complex bioactive ions and porous carbons remains unclear due to the variety of structures of bioactive ions present in biological systems. Herein, we investigate the adsorption behavior of a series of bioactive ammonium-based cations with varying alkyl chain lengths in nanoporous carbons. We find that strong physisorption results from the synergistic hydrophobic interaction and electrostatic attraction between porous carbons (with a negative zeta potential) and bioactive cations. Bioactive cations with varying alkyl chain lengths can be irreversibly physically adsorbed and confined within nanoporous carbons resulting in anion enrichment and depletion during electric polarization. This situation, in turn, results in a characteristic memristive behavior in all-carbon capacitive ionic memristor devices. Our findings highlight the relationship between the resistance state of the memristor and ion adsorption mechanisms in all-carbon capacitive devices, which hold potential for future transmitter delivery, biointerfacing, and neuromorphic devices.

Bioactive Ion‐Confined Ultracapacitive Memristors with Neuromorphic Functions

The field of bioinspired iontronics, bridging electronic devices and ionic systems, has multiple biological applications. Carbon‐based ultracapacitive devices hold promise for controlling bioactive ions via electric double layers due to their high‐surface‐area and biocompatible porous carbon electrodes. However, the interplay between complex bioactive ions and porous carbons remains unclear due to the variety of structures of bioactive ions present in biological systems. Herein, we investigate the adsorption behavior of a series of bioactive ammonium‐based cations with varying alkyl chain lengths in nanoporous carbons. We find that strong physisorption results from the synergistic hydrophobic interaction and electrostatic attraction between porous carbons (with a negative zeta potential) and bioactive cations. Bioactive cations with varying alkyl chain lengths can be irreversibly physically adsorbed and confined within nanoporous carbons resulting in anion enrichment and depletion during electric polarization. This situation, in turn, results in a characteristic memristive behavior in all‐carbon capacitive ionic memristor devices. Our findings highlight the relationship between the resistance state of the memristor and ion adsorption mechanisms in all‐carbon capacitive devices, which hold potential for future transmitter delivery, biointerfacing, and neuromorphic devices.

Polarization-independent and high-efficiency 2D dielectric transmission grating under Littrow incidence

In this paper, a transmission two-dimensional (2D) all-dielectric grating with cuboid arrays is proposed, which has high diffraction efficiency and good polarization independence under Littrow mounting conditions at an incident wavelength of 780 nm. The optimization results indicate that when the incident wavelength is 780 nm, the diffraction efficiency of the (−1, 0) order of transverse electric (TE) and transverse magnetic (TM) polarizations can reach 98.62% and 98.23%, respectively, with the polarization-dependent loss (PDL) of 0.017 dB. To the best of our knowledge, high-efficiency polarization-independent 2D transmission grating with a simpler and more effective structure is proposed for the first time, which demonstrates significant enhancements in bandwidth and manufacturing tolerances while maintaining high diffraction efficiency. The results suggest that the grating has great potential for applications in high-precision displacement measurements such as grating interferometers.

Tunability in electronic and optical properties of GaS/PbS vdW heterostructure

A promising novel class of heterostructures has recently emerged, combining a semiconducting GaS monolayer with other 2D materials for energy-related applications. In this study, we considered the layered PbS to form the van der Waals heterostructure with GaS and investigated its properties using density functional theory. The GaS/PbS heterostructure exhibits a type-II heterostructure with an indirect bandgap of 1.65 eV, displaying enhanced light absorption across the visible spectrum. Moreover, the heterostructure's energy band gap shows tunability with an applied transverse electric field attributed to the spontaneous electric polarization within the lattice. Subsequently, it contributes to increased optical absorbance and light harvesting efficiency under ±0.2 V/Å electric field. The applied electric field also offers tunable band alignments (transition type-II and type-I), making it a potential candidate for solar cells that can optimize their efficiency based on varying light conditions.

Circular-ring tied arc loaded excellent metamaterial absorber for EMI shielding of Wi-Fi signal and impurity sensing of cooking oil

This paper demonstrates a unique symmetric structure excellent metamaterial absorber (MMA) loaded with circular-ring tied arcs. The FR4 substrate-based MMA can accomplish 98.88 % and 99.81 % absorption maximums at the Wi-Fi and 5G frequencies of 2.4 GHz and 5.0 GHz respectively. The unit cell dimension of 0.16λ0×0.16λ0×0.0128λ0 is considered where the wavelength, λ0 is calculated at 2.4 GHz. The performance of the absorber is analyzed through the electric field, magnetic field, surface current, and effective parameters. The dimensions are optimized through the parametric analysis of the developed model in CST software. The model exhibits stability up to 60° for Transverse electric and magnetic polarizations. During electromagnetic interference (EMI) shielding demonstration, it can achieve a high shielding effectiveness (SE) of 54.34 dB at 2.4 GHz and 77.96 dB at 5.0 GHz. For sensing operation, it can attain a quality factor (Q-factor) of 25.61, a sensitivity of 3.30 %, and a figure of merit (FoM) of 84.51. The prototype measurements of the MMA for EMI shielding and impurity sensing of oil samples have a strong correlation with the simulation performance. Because of the high SE, Q-factor, sensitivity, and FoM, the developed MMA can be a competitive candidate in EMI shielding and oil impurity sensing applications.

Сегнетоэлектрические материалы в современных вычислениях

Background: Ferroelectric materials, known for their spontaneous electric polarization, are reshaping the landscape of modern computing. These materials have unique qualities, such as non-volatility, high-speed operation, and energy efficiency, which are critical for advancing modern computer technology. Objective: This study intends to investigate integrating ferroelectric materials into current computer systems, emphasizing to improve memory devices and processors and solve the accompanying technological obstacles and possibilities. Methods: A thorough analysis of existing literature and experimental data was carried out to determine the capabilities and limitations of ferroelectric materials in computing applications. Key performance indicators examined include polarization retention, energy consumption, scalability, and integration with existing semiconductor technology. Results: The results show that ferroelectric materials considerably increase memory device performance and efficiency by allowing quicker write/read operations and lowering power use. However, concerns such as material deterioration, data retention, and integration complexity with silicon-based technology remain. Conclusion: Ferroelectric materials provide exciting prospects for the next generation of computer technology. While they provide significant gains in memory and processing power, addressing the technological obstacles is critical to their effective adoption into mainstream computer applications. Further research and development are needed to solve these issues and fully realize the promise of ferroelectric materials in improving computer performance.

Nonlinear Optics Through the Field Tensor Formalism

AbstractThe “field tensor” is the tensor product of the electric fields of the interacting waves during a sum‐ or difference‐frequency generation nonlinear optical interaction. It is therefore a tensor describing light interacting with matter, the latter being characterized by the “electric susceptibility tensor.” The contracted product of these two tensors of equal rank gives the light‐matter interaction energy, whether or not propagation occurs. This notion having been explicitly or implicitly present from the early pioneering studies in nonlinear optics, its practical use has led to original developments in many highly topical theoretical or experimental situations, at the microscopic as well macroscopic level throughout a variety of coherent or non‐coherent processes. The aim of this review article is to rigorously explain the field tensor formalism in the context of tensor algebra and nonlinear optics in terms of a general time‐space multi‐convolutional development, using spherical tensors, with components expressed in the frame of a common basis set of irreducible tensors, or Cartesian tensors. A wide variety of media are considered, including biological tissues and their imaging, artificially engineered by various combinations of optical and static electric fields, with the two extremes of all‐optical and purely electric poling, and also bulk single crystals.

Al1−xScxSbyN1−y: An opportunity for ferroelectric semiconductor field effect transistor

For the in-memory computation architecture, a ferroelectric semiconductor field-effect transistor (FeSFET) incorporates ferroelectric material into the FET channel to realize logic and memory in a single device. The emerging group III nitride material Al1−xScxN provides an excellent platform to explore FeSFET, as this material has significant electric polarization, ferroelectric switching, and high carrier mobility. However, steps need to be taken to reduce the large band gap of ∼5 eV of Al1−xScxN to improve its transport property for in-memory logic applications. By state-of-the-art first principles analysis, here we predict that alloying a relatively small amount (less than ∼5%) of Sb impurities into Al1−xScxN very effectively reduces the band gap while maintaining excellent ferroelectricity. We show that the co-doped Sb and Sc act cooperatively to give a significant band bowing leading to a small band gap of ∼1.76 eV and a large polarization parameter ∼0.87 C/m2, in the quaternary Al1−xScxSbyN1−y compounds. The Sb impurity states become more continuous as a result of interactions with Sc and can be used for impurity-mediated transport. Based on the Landau-Khalatnikov model, the Landau parameters and the corresponding ferroelectric hysteresis loops are obtained for the quaternary compounds. These findings indicate that Al1−xScxSbyN1−y is an excellent candidate as the channel material of FeSFET.

Optimizing the polar phase transformation in PVDF-HFP/BaTiO3-activated carbon composite films with the mixture design of experiments

ABSTRACT A salient bottleneck to driving the wider use of polyvinylidene fluoride (PVDF) and its copolymers in smart applications is the requirement for a high-voltage poling process required to activate their β -phase crystal structure before the realisation of the piezoelectricity response. In pursuit of enhancing the β-phase content of PVDF-based films, various approaches have been employed in recent years. Yet, a perfect solution to the challenge remains elusive. Here, we report a preliminary investigation into the production of unpoled poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) films reinforced with barium titanate (BaTiO3) and activated carbon (AC) to improve the piezoelectric property. Employing the mixture design of experiments (MDOE) method, various formulations of the composite’s constituents weight fractions were determined. Afterwards, series of composite films were produced via a toxic-free solution casting method and characterised by Fourier Transform Infrared Spectrum (FTIR) to determine the β-phase content. A non-linear polynomial regression model was established from the experimental FTIR data, and the adequacy of the model was confirmed using ANOVA. Subsequently, an MDOE-enabled optimisation was undertaken, generating a formulation of the composite to obtain the highest β-phase content to be 15 wt.% BaTiO3 and 0.74 wt.% AC. This combination produces a theoretically predicted β-phase content of 72.7 %. A further experimental test employing the optimal formulation produced a β-phase content of 71.90 %, achieved with neither mechanical stretching, thermal annealing, nor electrical poling.

Magnetic and dielectric properties of low‐loss MnZn ferrites with wide temperature stability

AbstractTo meet the needs for higher energy efficiency and a wide operating temperature range of electric vehicles, the low‐loss MnZn ferrites in a wide temperature range have been developed by optimizing the Fe content and the oxygen partial pressure (PO2) during the sintering process in this work. For the optimal sample, power loss at 300 kHz/100mT is 204 kW/m3 at 25°C and remains below 290 kW/m3 in the wide temperature range from ‐10 to 120°C. The loss separation method was employed to clarify the effects of the Fe content and PO2 on power loss. The equivalent circuit model has been employed to fit the complex impedance and it is found that the increase of PO2 enhances both the grain resistance Rg and the grain boundary resistance Rgb. The enhancement of Rgb is mainly responsible for the reduction of eddy current loss and consequently power loss. Dielectric permittivity is as large as about 15000 in this series of samples due to the electric polarization at the rich grain boundaries. Dielectric loss is very low between ‐50 and 150°C and has little contribution to the energy loss.

Optimal polarization and susceptibility profiles of a half-filled open magnetoelectric Fermi-Hubbard optical dimer

Magnetoelectric materials, such as thin films and magnetoelectric antennae, exhibit tunable magnetic polarization using external electric field and electric polarization using external magnetic field at room temperature by introducing strain, for instance. A more straightforward method to optimize magnetoelectric effect is by adjusting the applied electromagnetic fields in systems modeled by the Fermi-Hubbard dimer. In this study, direct and converse magnetoelectric effects are theoretically observed in an open Fermi-Hubbard dimer by tuning the external electromagnetic fields. Results show that an external magnetic field can enhance the electric polarization and susceptibility of the dimer particles without the necessity of mechanical strain. Conversely, gradients in an external electric field modulate the magnetic polarization and susceptibility. This striking behavior in the Fermi-Hubbard dimer can serve as a physical model for developing quantum control of complex materials such as in biosensors, biomedical processes, and energy harvesting.

Intrinsic dipole Hall effect in twisted MoTe2: magnetoelectricity and contact-free signatures of topological transitions

We discover an intrinsic dipole Hall effect in a variety of magnetic insulating states at integer fillings of twisted MoTe2 moiré superlattice, including topologically trivial and nontrivial ferro-, antiferro-, and ferri-magnetic configurations. The dipole Hall current, in linear response to in-plane electric field, generates an in-plane orbital magnetization M∥ along the field, through which an AC field can drive magnetization oscillation up to THz range. Upon the continuous topological phase transitions from trivial to quantum anomalous Hall states in both ferromagnetic and antiferromagnetic configurations, the dipole Hall current and M∥ have an abrupt sign change, enabling contact-free detection of the transitions through the magnetic stray field. In configurations where the linear response is forbidden by symmetry, the dipole Hall current and M∥ appear as a crossed nonlinear response to both in-plane and out-of-plane electric fields. These magnetoelectric phenomena showcase fascinating functionalities of insulators from the interplay between magnetism, topology, and electrical polarization.

Full field crack solutions in anti-plane flexoelectricity

In flexoelectric materials, strain gradients can induce electrical polarization. However, internal defects such as cracks profoundly affect the electromechanical coupling properties of flexoelectric solids. In particular, anti-plane cracks involve less physical fields, which are easier to study. In this study, we present a comprehensive and innovative investigation of the anti-plane crack problems in flexoelectric materials, including semi-infinite and finite-length anti-plane cracks. For the first time, we formulate a full-field solution for semi-infinite anti-plane cracks in flexoelectric media by applying the Wiener–Hopf technique. Furthermore, the collocation method and the Chebyshev polynomial expansion are used for the first time to derive the full-field hypersingular integral equation solution for finite-length anti-plane cracks in flexoelectric solids. In addition, a comparative analysis between the full-field and asymptotic solutions for semi-infinite cracks is performed, shedding light on the discrepancies in the representation of the electromechanical coupling behavior near the crack tip. The mixed finite element method is used to compare with the full-field solutions of finite-length cracks. The agreement between the numerical results and the full-field solutions demonstrates the rigor of our study. This research advances the knowledge of defects in flexoelectricity and provides significant insight into relevant failure mechanisms.

A dual-band polarization independent dielectric metasurface-based absorber for sensing application in the visible light regime

We present a dual-band, polarization-independent dielectric terahertz absorber exhibiting near-perfect absorption and minimal reflection at frequencies of f 1 = 419 THz and f 2 = 528 THz. Using electromagnetic theory, we modeled the structure to derive the surface electric admittance and magnetic impedance of the metasurface, elucidating the conditions required for perfect absorption in terms of inverse electric and magnetic polarizabilities. The absorber features a tunable symmetrical design, facilitating precise frequency adjustment by modifying structural parameters and ensuring polarization independence for perpendicularly incident electromagnetic waves. This scalable and versatile absorber, constructed from readily available materials, is optimally suited for applications in resource detection, imaging, sensing, and medical diagnostics, attributed to its simplicity, cost-effectiveness, and high performance.

An efficient and miniaturized ultra-thin tunable UWB graphene metasurface absorber for terahertz gap regime

This work introduces an ultra-thin tunable ultra-wideband (UWB) metasurface absorber (MSA) for the terahertz (THz) gap. The polarization-insensitive MSA provides an absorptivity (A(f)) ≥ 90% from 0.1 to 11.5 THz, corresponding to 196.6% fractional bandwidth. The usage of resonant slots engraved on top patterned graphene sheet (Gpat) and strong plasmonic coupling in the Fabry-Perot cavity formed between top Gpat and bottom continuous graphene (Gcont) in bilayer stack configuration ensures absorptivity over a UWB THz spectrum. An equivalent circuit model (ECM) closely follows the A(f) response of the proposed MSA. The proposed DC-biasing mechanism can regulate the chemical potential (μc) of the connected Gcont efficiently. A DC bias voltage of 0 to 6.1 V is adequate to vary μc of Gcont from 0 to 0.6 eV for achieving tunable A(f). The structure maintains its ultra-thin nature and has a thickness of only λ0/1500, where λ0 is the free space wavelength calculated at 0.1 THz. In addition, the periodicity is only λ0/300. The MSA also provides stable absorption response from 0.1 to 11.5 THz with A(f) ≥ 80% for incidence angle (θ) up to 60∘ under both transverse magnetic (TM) and transverse electric (TE) polarization.

Nonsymmetrical thermal conductivity along the director field in ferroelectric nematic liquid crystals.

The synthesis of ferroelectric nematic liquid crystals (FNLCs) concludes the long wait for their existence and potential usage in multiple liquid crystal based applications. In FNLCs, electric polarization in the nematic phase significantly decreases the switching time of in-on display pixels. In this article, we report the occurrence of translation symmetry breaking for heat propagation along the director field n[over ̂] in the ferroelectric nematic phase. Due to the C_{∞V} symmetry of such a phase and close similarity to the bent-core polar liquid crystal phase, a rank-3 tensor describes its scalar order parameter and algebraic deductions. The finite element simulations show the occurrence of the nonsymmetrical thermal conductivity along n[over ̂]. The preferential heat transport in FNLCs can allow them to work as an all-thermal monophase non-nanostructured single-material thermal rectifier. We expect that this study will contribute towards the FNLCs application as functional layers and inks.

Polarization-Switchable Electrochemistry of 2D Layered Bi2O2Se Bifunctional Microreactors by Ferroelectric Modulation.

Ferroelectric catalysts are known for altering surface catalytic activities by changing the direction of their electric polarizations. This study demonstrates polarization-switchable electrochemistry using layered bismuth oxyselenide (L-Bi2O2Se) bifunctional microreactors through ferroelectric modulation. A selective-area ionic liquid gating is developed with precise control over the spatial distribution of the dipole orientation of L-Bi2O2Se. On-chip microreactors with upward polarization favor the oxygen evolution reaction, whereas those with downward polarization prefer the hydrogen evolution reaction. The microscopic origin behind polarization-switchable electrochemistry primarily stems from enhanced surface adsorption and reduced energy barriers for reactions, as examined by nanoscale scanning electrochemical cell microscopy. Integrating a pair of L-Bi2O2Se microreactors consisting of upward or downward polarizations demonstrates overall water splitting in a full-cell configuration based on a bifunctional catalyst. The ability to modulate surface polarizations on a single catalyst via ferroelectric polarization switching offers a pathway for designing catalysts for water splitting.