137,765 results on '"ELECTRIC fields"'
Search Results
2. A 1 kV sub-nanosecond electrical pulse generated by a linear GaAs photoconductive semiconductor switch and its characterization.
- Author
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Wang, Hongqi, Shi, Wei, Ma, Cheng, Wu, Meilin, Tao, Jiang, and Chen, Kaipeng
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GALLIUM arsenide semiconductors , *INERTIAL confinement fusion , *PULSED lasers , *GALLIUM arsenide , *ELECTRIC fields , *LASER pulses - Abstract
The generation of high-voltage ultrafast electrical pulses has significant potential for application in ultrawideband microwave sources, terahertz technology, and inertial confinement fusion. However, there is still a lack of the generation of high-voltage ultrafast electrical pulses with greater peak amplitudes and faster pulse widths and ultrafast characteristics. In this paper, a linear low-temperature gallium arsenide photoconductive semiconductor switch (LT-GaAs PCSS) is developed using the ps-scale carrier lifetime of low-temperature gallium arsenide (LT-GaAs). The generation of ultrafast electrical pulses with a pulse width of 0.5 ns and a voltage amplitude of 1 kV is achieved by triggering a pulsed laser with a wavelength of 1064 nm, a single pulse energy of 70 μJ, and a pulse width of 30 ps. The impact of parameters, such as bias electric field, laser pulse energy, and transmission line length, on the ultrafast characteristics of the output electric pulse of the LT-GaAs PCSS is investigated through a synthesis of experimental and simulation approaches. The results show that (1) in linear conditions, the output pulse amplitude is mainly determined by the bias voltage and laser pulse energy, and the output pulse amplitude is also affected by conductor and dielectric attenuation in the transmission line; (2) the falling edge is determined by the carrier lifetime. Because of the absorption depth at 1064 nm and the carrier lifetime of semi-insulating gallium arsenide material, the output electrical pulse has a trailing edge; (3) the bias voltage and laser pulse energy can improve voltage transmission efficiency, and the saturation of voltage transmission efficiency is caused by the saturation of photon absorption in LT-GaAs material. [ABSTRACT FROM AUTHOR]
- Published
- 2025
- Full Text
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3. Application of the Skanavi model to CaCu3Ti4O12 materials.
- Author
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Luo, Hao, Geng, Kejia, Qin, Xinrui, Kong, Cuncun, Liu, Xin, Su, Xueyan, Su, Yaoheng, Lu, Dingze, and Cheng, Pengfei
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ELECTRIC fields , *FERROELECTRICITY , *PERMITTIVITY , *OCTAHEDRA , *EQUATIONS - Abstract
In this paper, the optical and static permittivities of CaCu3Ti4O12 supercells are calculated based on the Skanavi model by decomposing the electric field of molecules into the electric field of ions. The results show that the Skanavi model's theoretical predictions are significantly more accurate than those of the Clausius–Mossotti equation and Born model and are in good agreement with the experimental data. In addition, the absence of ferroelectricity in CaCu3Ti4O12 is also revealed by investigating the changes in the structural coefficients of the effective electric field caused by the displacement of Ti4+ along the z-axis. Finally, by analyzing the contribution of TiO6 octahedra or CuO4 planar squares to the static permittivity, the main polarization unit in the structure of CaCu3Ti4O12 has been discovered. This study not only makes up for the insufficient research on the polarization mechanism of CaCu3Ti4O12 but also provides a new tool to explore the polarization mechanism of other materials. [ABSTRACT FROM AUTHOR]
- Published
- 2025
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4. Experimental discrimination of domain switching behaviors within interfacial and bulk layers in the LiNbO3 domain-wall memory.
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Zhang, Wen Di and Jiang, An Quan
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RATE of nucleation , *DISCONTINUOUS precipitation , *FERROELECTRIC devices , *HYSTERESIS loop , *ELECTRIC fields - Abstract
Multilevel resistance states with respect to the volume of the reversed domains in ferroelectric tunneling junctions and erasable conducting domain walls in an insulating ferroelectric matrix enable high-speed and energy-efficient ferroelectric synapses, memories, and transistors. According to the domain nucleation model, the operation speeds of these devices are assumedly limited by domain nucleation time while the subsequent domain growth time is neglected. Unfortunately, these two times cannot be separated from the experiment yet. Here, we observed independent switching behaviors of domain nucleation and growth at two discrete coercive fields for a mesa-like memory cell formed at the surface of a LiNbO3 single crystal. After the application of an in-plane electric field to two side electrodes, we observed the on currents upon antiparallel domain reversals via the creation of conducting domain walls between them. Once the applied electric field is removed, the domains within the interfacial layers between the two side electrodes and the cell are volatile and switch back into their initial orientations automatically, unlike the nonvolatile bulk domain encoding digital information. In consideration of volatile and nonvolatile natures of the two domains, we separately observed their switching behaviors from the measurements of frequency-dependent domain switching hysteresis loops after programing various write and read pulses. It is found that all coercive fields with the involvement of domain nucleation at the interfaces are always frequency-dependent, unlike domain forward growth within the bulk layer that is frequency-independent. This provides the direct evidence that the operation speed of the low-dimensional ferroelectric device is limited by the domain nucleation rate at the interface. [ABSTRACT FROM AUTHOR]
- Published
- 2025
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5. Evaluation of arc quenching ability for SF6 replacements based on time-dependent Elenbaas–Heller and Boltzmann equations.
- Author
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Ren, He and Zhong, Linlin
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BOLTZMANN'S equation , *GAS mixtures , *DIELECTRIC strength , *SULFUR hexafluoride , *ELECTRIC fields - Abstract
Sulfur hexafluoride (SF6), a widely used arc quenching medium in the power industry, has been designated as a greenhouse gas, necessitating its reduction and replacement. Identifying eco-friendly alternatives to SF6 is a complex and expensive process, particularly since these alternatives often consist of gas mixtures that may function at varying pressures. In this work, we propose an efficient method for evaluating the arc quenching performance of gases or gas mixtures using the time-dependent Elenbaas–Heller and Boltzmann equations, which circumvents the computational costs associated with traditional 2D or 3D magnetohydrodynamic arc models. We segment the arc quenching process into four distinct stages: the thermal recovery stage, pre-dielectric recovery stage, post-dielectric recovery stage, and residual-gas cooling stage. To quantitatively assess arc quenching performance, we introduce two key parameters: recovery rate and recovery strength. The recovery rate is defined as the harmonic mean of thermal, pre-dielectric, and post-dielectric recovery rates. The recovery strength is characterized by the harmonic mean of the average recovery voltage, maximum critical electric field strength, and room-temperature dielectric strength. Our method is validated using several SF6 alternatives, including SF6 mixtures, C4F8, C4F7N, C5F10O, and their mixtures with CO2, N2, and O2. The results demonstrate that the coupling of the time-dependent Elenbaas–Heller and Boltzmann equations well describes the arc decaying process. Moreover, the proposed recovery rate and recovery strength metrics effectively quantify the arc quenching ability, enabling a systematic and efficient evaluation of various gas mixtures for arc interruption performance. [ABSTRACT FROM AUTHOR]
- Published
- 2025
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6. Dielectric profile at the Pt(111)/water interface.
- Author
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Zhu, Jia-Xin, Cheng, Jun, and Doblhoff-Dier, Katharina
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PERMITTIVITY , *ELECTRIC fields , *MOLECULAR dynamics , *DIELECTRICS , *ELECTRIC capacity - Abstract
The dielectric constant, although a simplified concept when considering atomic scales, enters many mean-field, electrochemical interface models and constant potential models as an important parameter. Here, we use ab initio and machine-learned molecular dynamics to scrutinize the behavior of the electronic contribution to ɛr(z) as a function of distance z from a Pt(111) surface. We show that the resulting dielectric profile can largely be explained as a sum of the metallic response and the density-scaled water response at the interface. A slight enhancement of the dielectric response close to the surface can be explained by elongated, strongly polarizable orbitals induced by metal/water bonding. In spite of this enhancement, our results suggest the presence of a region with a very low dielectric constant close to the surface (where the orientational dielectric response does not kick in yet), even for water in contact with hydrophilic metallic interfaces. This region will restrict the double layer capacitance to relatively low values even at potentials where dielectric saturation does not play a role yet. This finding has implications on possible interpretations of double layer capacitances, the dependence of surface electric fields on the ion size, and on electrochemical kinetics. [ABSTRACT FROM AUTHOR]
- Published
- 2025
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7. Electric dipole moment of excited octupolar molecules: Potential qubit implementation.
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Ivanov, Anatoly I.
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ELECTRIC dipole moments , *DIPOLE moments , *ELECTRIC fields , *PAULI matrices , *MOLECULAR magnetic moments - Abstract
The first excited state of conjugated donor–acceptor molecules of C3 symmetry (octupolar molecules) is doubly degenerate. Such a doublet is known to be isomorphic to a spin 1/2. It is shown that a large electric dipole moment is associated with this spin. Since the mean value of the electric dipole moment of an octupolar molecule is a measure of the symmetry breaking charge transfer, a dimensionless dipole moment called the dissymmetry vector is introduced. The dissymmetry vector operator is constructed. A linear tensor connection between this operator and the Pauli matrices is found. The tensor character is due to the two-dimensionality of the dipole moment. The dipole moment can rotate freely in the plane of the molecule as long as the C3 symmetry is maintained. The rotation is associated only with the rearrangement of the electronic subsystem of the molecule and does not affect the spatial position of the nuclei. This opens up the possibility of changing the dipole moment state on a subpicosecond time scale. The Jahn–Teller effect on the dissymmetry vector is considered in detail. It is shown that the dissymmetry vector can be controlled using electric fields in the same way as three-dimensional spin if both static and alternating electric fields are in the plane of the molecule. The conducted studies indicate that the dipole moment of excited octupolar molecules is a promising candidate for the physical implementation of a qubit. [ABSTRACT FROM AUTHOR]
- Published
- 2025
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8. Collective behavior in intrinsic polarization switching of PbTiO3 and Pb(Zr,Ti)O3.
- Author
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Park, Suehyun, Kim, Raseong, and Young, Ian A.
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POLARIZATION (Electricity) , *FERROELECTRIC materials , *COLLECTIVE behavior , *ELECTRIC fields , *MOLECULAR dynamics - Abstract
Ferroelectric materials play a pivotal role in various industrial and scientific applications due to their ability to exhibit spontaneous electric polarization above a critical temperature. The application of a sufficiently high external electric field can induce the switching of the spontaneous polarization, with the specific mechanism varying across different materials. Understanding the intrinsic switching mechanism is paramount for regulating polarization domains, thereby unlocking potential applications in nanoelectronic devices. Different types of switching mechanisms have been experimentally reported and various models have been developed, among them the nucleation-limited-switching (NLS) model, which is distinguished by nucleation and limited propagation. We investigate the intrinsic polarization switching mechanisms in PbTiO 3 and Pb(Zr,Ti)O 3 using molecular dynamics simulations. We found that both PbTiO 3 and Pb(Zr,Ti)O 3 exhibit the change of switching mechanisms as the field increases. At high electric field, they both follow homogeneous switching mechanism without the nucleation of domains. At weak electric fields, the NLS model effectively described the switching behavior of both PbTiO 3 and Pb(Zr,Ti)O 3 , although the atomistic details of their respective switching mechanisms diverge. We demonstrate that, for PbTiO 3 , the switching mechanism at weak fields involves the collective behavior near nuclei such as the formation of vortices, which is characterized by the hypertoroidal moment. We also report the substantial in-plane dipolar pattern of Pb(Zr,Ti)O 3 at low fields, independent of switching. This work contributes to a comprehensive understanding of ferroelectric switching and, thus, results in better prediction of designing new nanoelectronic devices. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
9. 2D materials for infrared sensing and hyperspectral imaging.
- Author
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Kandegedara, R. M. E. B., Krishnamurthy, Srini, Yu, Zhi-Gang, Grein, Christoph, and Sivananthan, Sivalingam
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ABSORPTION coefficients , *ELECTRIC fields , *SUBSTRATES (Materials science) , *BILAYERS (Solid state physics) , *ARSENIDES - Abstract
2D materials for sensing applications offer several advantages—high absorption in thin layers, the lack of surface dangling bonds or major defects, ease of materials synthesis and device fabrication, and relaxed substrate lattice-matching requirements. We theoretically explore two 2D materials, hexagonal boron phosphide and hexagonal boron arsenide, for possible infrared sensing and hyperspectral applications. Using first principles, we calculate the total energy of formation, band structures, and absorption coefficient of monolayer and bilayer materials. We evaluate the bandgap and absorption coefficient of bilayers as a function of layer stacking, number of layers, and applied field across the layers. We find that with a choice of stacking order, number of layers, and applied field, the material can be chosen appropriately for sensing of short-, mid-, or long-wavelength infrared radiation. Furthermore, the absorption is increased in these materials with applied electric fields. With the ability to dynamically change the bandgap with an external electric field, this class of materials is ideally suited for continuous hyperspectral sensing in the infrared. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
10. Collective behavior in intrinsic polarization switching of PbTiO3 and Pb(Zr,Ti)O3.
- Author
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Park, Suehyun, Kim, Raseong, and Young, Ian A.
- Subjects
POLARIZATION (Electricity) ,FERROELECTRIC materials ,COLLECTIVE behavior ,ELECTRIC fields ,MOLECULAR dynamics - Abstract
Ferroelectric materials play a pivotal role in various industrial and scientific applications due to their ability to exhibit spontaneous electric polarization above a critical temperature. The application of a sufficiently high external electric field can induce the switching of the spontaneous polarization, with the specific mechanism varying across different materials. Understanding the intrinsic switching mechanism is paramount for regulating polarization domains, thereby unlocking potential applications in nanoelectronic devices. Different types of switching mechanisms have been experimentally reported and various models have been developed, among them the nucleation-limited-switching (NLS) model, which is distinguished by nucleation and limited propagation. We investigate the intrinsic polarization switching mechanisms in PbTiO 3 and Pb(Zr,Ti)O 3 using molecular dynamics simulations. We found that both PbTiO 3 and Pb(Zr,Ti)O 3 exhibit the change of switching mechanisms as the field increases. At high electric field, they both follow homogeneous switching mechanism without the nucleation of domains. At weak electric fields, the NLS model effectively described the switching behavior of both PbTiO 3 and Pb(Zr,Ti)O 3 , although the atomistic details of their respective switching mechanisms diverge. We demonstrate that, for PbTiO 3 , the switching mechanism at weak fields involves the collective behavior near nuclei such as the formation of vortices, which is characterized by the hypertoroidal moment. We also report the substantial in-plane dipolar pattern of Pb(Zr,Ti)O 3 at low fields, independent of switching. This work contributes to a comprehensive understanding of ferroelectric switching and, thus, results in better prediction of designing new nanoelectronic devices. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
11. Liquid, liquid crystal, and crystal states of different shaped colloids in nonuniform fields via osmotic force balance.
- Author
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Zhang, Lechuan, Pellicciotti, Alec J., Sandag, Michelle, and Bevan, Michael A.
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OSMOTIC pressure , *MONTE Carlo method , *COMPRESSIVE force , *MICROSCOPY , *ELECTRIC fields - Abstract
We report a model to predict equilibrium density profiles for different shaped colloids in two-dimensional liquid, nematic, and crystal states in nonuniform external fields. The model predictions are validated against Monte Carlo simulations and optical microscopy experiments for circular, square, elliptical, and rectangular colloidal particles in AC electric fields between parallel electrodes. The model to predict the densities of all states of different shaped particles is based on a balance of the local quasi-2D osmotic pressure against a compressive force due to induced dipole-field interactions. The osmotic force balance employs equations of state for hard ellipse liquid, nematic, and crystal state osmotic pressures, which are extended to additional particle shapes. The resulting simple analytical model is shown to accurately predict particle densities within liquid, liquid crystal, and crystal states for a broad range of particle shapes, system sizes, and field conditions. These findings provide a basis for quantitative design and control of fields to assemble and reconfigure colloidal particles in interfacial materials and devices. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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12. Unveiling frequency dependence of electrical treeing degradation in epoxy resin under bipolar square wave voltage.
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Zhang, Chuang, Xiang, Jiao, Ruan, Yang, Cui, Huize, Wang, Shihang, Li, Jianying, and Li, Shengtao
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ELECTRIC breakdown , *ELECTRIC fields , *EPOXY resins , *POWER electronics , *TREES (Electricity) , *LUMINESCENCE - Abstract
The epoxy insulation used in high frequency transformers encountered breakdown easily due to bipolar square wave voltage with steep rising/falling edge and high frequency. An insight into the frequency dependence of electrical tree development in epoxy resin under bipolar square wave voltage was elucidated in this paper. It was found that luminescence existed in all treeing channels, where the intensity of luminescence at the electrical tree tip under a high frequency (>4 kHz) was stronger than that at a low frequency (<4 kHz), indicating an electric field delivery from the needle tip to the channel tip at high frequency. Correspondingly, the fluorescent material deposited on the wall of the tree channel evolved from discontinuous at a low frequency to continuous at a high frequency with aggravated degradation. In addition, the frequency dependence of electrical tree breakdown related to field delivery was revealed. By combining the field delivery along treeing channels and the frequency dependence of the mechanical properties of epoxy resin, the growing model of an electrical tree under bipolar square wave voltage was illustrated elaborately. It was proposed that the dominant factors that drove electrical tree propagation were electric field force at a low frequency and partial discharge at a high frequency, respectively. This work can boost the advancement of polymers, electrical equipment, and power electronics at a high frequency. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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13. First-principles study of nonlinear magnetoelectric effects in improper LuFeO3 multiferroics.
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Ke, Da and Zhang, Yubo
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POLARIZATION (Electricity) , *MAGNETOELECTRIC effect , *ELECTRIC fields , *LANDAU theory , *ATOMIC interactions - Abstract
Hexagonal LuFeO3 is known as an improper multiferroic material because of its ferroelectric structural distortion, measured by the Γ 2 − polar mode, and is driven by a trimerization structural distortion represented by the K3 non-polar mode [Fennie and Rabe, Phys. Rev. B 72, 100103(R) (2005)]. The K3 mode is also the primary structural origin of net weak ferromagnetism, associated with the ferromagnetic coupling between the in-plane geometrically frustrated spins. Here, we study the magnetoelectric coupling in LuFeO3 using first-principles calculations and applied external electric fields. We find that the weak ferromagnetism responds to the electric field polarization through the K3– Γ 2 − coupling, which is an intrinsic characteristic of improper multiferroics. Interestingly, the magnetoelectric coupling exhibits strong asymmetry under positive and negative electric fields. This nonlinearity is due to the competition between the K3 and the Γ 2 − modes according to Landau's theory and is related to asymmetrical interatomic interactions at the atomic level. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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14. Electrothermal enhancement of β-(AlxGa1−x)2O3/Ga2O3 heterostructure field-effect transistors via back-end-of-line sputter-deposited AlN layer.
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Lundh, James Spencer, Cress, Cory, Jacobs, Alan G., Cheng, Zhe, Masten, Hannah N., Spencer, Joseph A., Sasaki, Kohei, Gallagher, James, Koehler, Andrew D., Konishi, Keita, Graham, Samuel, Kuramata, Akito, Anderson, Travis J., Tadjer, Marko J., Hobart, Karl D., and Mastro, Michael A.
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SPUTTER deposition , *FIELD-effect transistors , *THERMAL conductivity , *REACTIVE sputtering , *ELECTRIC fields - Abstract
The electrothermal device performance of β-(Al0.21Ga0.79)2O3/Ga2O3 heterostructure field-effect transistors (HFETs) was enhanced by incorporating a 400 nm thick AlN capping layer via back-end-of-line room-temperature reactive sputter deposition. The AlN-capped HFETs demonstrated DC power densities >5 W/mm, higher than any previous report on lateral β-Ga2O3 transistors on native substrates. The breakdown voltage (VB) of the uncapped HFETs was 569 ± 250 V with a maximum VB of 947 V. For the AlN-capped HFETs, VB increased to 1210 ± 351 V with a maximum VB of 1868 V. The AlN-capped HFETs demonstrated a 27% reduction in device-level thermal resistance (RTH) as measured from the gate electrode. The combined use of electrical and thermal simulation helped elucidate the coupled electrothermal contributions to the measured reduction in the temperature rise for the AlN-capped HFETs. Although the measured AlN film thermal conductivity (13.3 ± 1.3 W/mK) was comparable to that of bulk β-Ga2O3, the capping layer still reduced the simulated peak channel temperature rise by ∼4% due to heat spreading only. Electrical simulation revealed that electric field spreading was an additional mechanism that contributed to the majority of the simulated 18% reduction in the peak channel temperature rise through delocalization and redistribution of the heat generation in the channel. Thermal modeling was used to evaluate further improvements in thermal performance that can be realized by optimizing the sputter deposition process to achieve thicker and higher thermal conductivity AlN. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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15. Dielectric nonlinearity analysis of BNT–ST–BT relaxor ferroelectric thin films with different film thicknesses.
- Author
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Zhao, Jinyan, Wang, Zhe, Li, Yizhuo, Zheng, Kun, Zhang, Jie, Meng, Haoyan, Zhang, Nan, Zhao, Yulong, Niu, Gang, and Ren, Wei
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DIELECTRIC properties , *ELECTRIC fields , *THIN films , *DIELECTRICS , *PERMITTIVITY , *FERROELECTRIC thin films - Abstract
Thickness-dependent dielectric nonlinear properties of 0.78Bi0.5Na0.5TiO3–0.2SrTiO3–0.02BaTiO3 thin films in a thickness range of 0.62–1.62 μm were investigated in this work. It was demonstrated that the dielectric properties decreased with the decrease in thickness due to the substrate clamping inducing the degeneration of intrinsic contribution and the reduced domain wall mobility. A low DC electric field promoted domain switching and reversible domain wall motion. The domain mobility was suppressed by a high DC electric field, which resulted in reduced dielectric permittivity combined with the tunability of intrinsic dielectric response. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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16. Emergent local negative electrostriction induced by oxygen vacancy in BaHfO3: Defect engineering.
- Author
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Ikeda, Yoshitaka, Minami, Susumu, and Shimada, Takahiro
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OXYGEN vacancy , *FINITE fields , *ELECTRONIC structure , *ELECTRIC fields , *ELECTROSTRICTION - Abstract
Realization of ultrasmall scale electromechanical materials has been promising for advanced functional devices. Recently, single-atom devices have been proposed as the ultimate miniaturization of functional devices beyond the nanoscale; however, achieving an atomic-scale local electromechanical response is still challenging due to physical size limitation of electromechanical properties as well as technical difficulties in fabricating the functional materials in a single atom precision. Here, we demonstrate a non-trivial negative electromechanical response at an oxygen vacancy in paraelectric BaHfO3 using first-principles finite electric field calculations. We find an electrostrictive response at the vacancy site in the same order of magnitude in well-known oxide materials. Surprisingly, we also discover an unusual "negative" sign of electrostriction in the oxygen vacancy. The detailed electronic structure analysis demonstrates that a unique electric field response of a localized defect electronic structure is the origin of this negative electrostriction of vacancy. The present results provide an important implication for the design of ultra-small electromechanical functions at an atomic scale. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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17. Enhancing optical absorbance and accelerating rotational speed in molecular motors through oriented external electric fields.
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Wu, Liang-Ting, Nachimuthu, Santhanamoorthi, Kaleta, Jiří, and Jiang, Jyh-Chiang
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MOLECULAR magnetic moments , *ELECTRONIC excitation , *ELECTRIC fields , *DENSITY functional theory , *LIGHT absorption , *MOLECULAR motor proteins - Abstract
Accelerating the rotational speed of light-driven molecular motors is among the foremost concerns in molecular machine research, as this speed directly influences the performance of a motor. Controlling the motor's rotation is crucial for practical applications, and using an oriented external electric field (OEEF) represents a feasible method to achieve this objective. We have investigated the impact of an OEEF on the optical and kinetic properties of a novel π-donor/acceptor di-substituted molecular motor, R2,3-(NH2, CHO). We employed density functional theory (DFT) and time-dependent DFT methods to analyze the electronic excitation and thermal isomerization behavior. Our results demonstrate that the absorption wavelength, absorption efficiency of the motor, and rate constant of the thermal isomerization reaction can be adjusted by applying OEEFs, which are predictable based on the dipole moment and polarizability of the molecules under consideration. In particular, we observed a shift in the absorption wavelength toward longer ranges, an enhancement in light absorption intensity, and an acceleration in the rotation rate when applying a weak positive directional external electric field to the R2,3-(NH2, CHO) motor. In summary, this theoretical study highlights the potential of OEEFs for improving the performance of molecular motors. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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18. The influence of water polarization on slip friction at charged interfaces.
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Kunhunni, Amith, Varghese, Sleeba, Kannam, Sridhar Kumar, Sathian, Sarith P., Daivis, Peter J., and Todd, B. D.
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AQUEOUS electrolytes , *ELECTRIC field effects , *ELECTROSTATIC fields , *MOLECULAR dynamics , *ELECTRIC fields - Abstract
The present study employs equilibrium molecular dynamics simulations to explore the potential mechanism for controlling friction by applying electrostatic fields in nanoconfined aqueous electrolytes. The slip friction coefficient demonstrates a gradual increase corresponding to the surface charge density for pure water and aqueous electrolytes, exhibiting a similar trend across both nanochannel walls. An expression is formulated to rationalize the observed slip friction behavior, describing the effect of the electric field on the slip friction coefficient. According to this formulation, the slip friction coefficient increases proportionally to the square of the uniform electric field emanating from the charged electrode. This increase in slip friction results from the energy change due to the orientation polarization of interfacial water dipoles. The minimal variations in the empirically determined proportionality constant for pure water and aqueous electrolytes indicate that water polarization primarily governs slip friction at charged interfaces. These findings offer insights into the electrical effects on nanoscale lubrication of aqueous electrolytes, highlighting the significant role of water polarization in determining slip. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
19. Streamer evolution in nanosecond pulsed sliding surface dielectric barrier discharge: 2D numerical modelling.
- Author
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Zhang, Bin, Zhang, Xiaobing, and Wu, Shuqun
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ELECTRIC discharges , *ELECTRIC fields , *SURFACE charging , *CHARGE transfer , *DIELECTRICS - Abstract
The sliding surface dielectric barrier discharge (SDBD) plasma actuator enables a large interaction region between the discharge and the incoming flow, facilitating active flow control. A 2D model of the sliding discharge, initiated within a three-electrode configuration, is developed. The high-voltage (HV) electrode is connected to a positive nanosecond pulse with an amplitude of 7 kV, and a positive/negative DC voltage is applied to the third electrode, with a 10 mm inter-electrode gap. To account for the dielectric surface charging process, the DC voltage discharge is simulated for a sufficient duration to reach a steady state before the initiation of the nanosecond pulse. This study aims to understand the discharge characteristics of sliding SDBD and to investigate the effects of different polarities and amplitudes of the DC voltage on surface charge distribution, surface ionization wave propagation, electric field evolution, and hydrodynamic perturbations. With the application of negative DC voltage, the deposited surface charge on the dielectric surface neutralizes positive charges at the streamer head, enhancing the electric field at the discharge front, which extends the plasma length up to the third electrode. In contrast, a positive DC voltage impedes net charge transfer, thereby inhibiting the formation of a sliding discharge. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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20. Technology for monitoring the surface emission inhomogeneity in plasma electronics devices.
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Mustafaev, A. S., Grabovskiy, A. Y., Sukhomlinov, V. S., and Shtoda, E. V.
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SECONDARY electron emission , *POTENTIAL barrier , *REFLECTANCE , *SINGLE crystals , *ELECTRIC fields - Abstract
The article discusses a theoretical and experimental investigation of the reflection of slow electrons from the surfaces of single-crystal and polycrystalline tungsten thermionic cathodes. The findings challenge traditional ideas as they confirm that the effective reflection coefficient, reff, can reach values close to unity contrary to prior belief. The reason for this occurrence has been established, which is the additional reflection of slow electrons from a potential barrier near polycrystalline surfaces. A method has been developed to separately measure electron reflection coefficients at the surfaces of thermionic cathodes and at the potential barrier of electrode spot fields with different work functions. The study reveals that the maximum values of reff are achieved on polycrystalline surfaces. Additionally, the work functions and reflection coefficients rhkl have been determined for the faces of single crystals of (110), (112), (100), (111), and (116) oriented tungsten. The proposed method enables control over cathode emission inhomogeneity and makes it possible to mitigate the negative effects of secondary electron emission by suppressing electric fields near the cathode surface. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
21. Electric-field-induced polarization anisotropy of interband photoluminescence in GaAs.
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Shalygin, V. A., Makhov, I. S., Adamov, R. B., Vinnichenko, M. Ya., Khvostikov, V. P., and Firsov, D. A.
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DISTRIBUTION (Probability theory) , *MOMENTUM space , *OPTICAL elements , *ELECTRON distribution , *ELECTRIC fields - Abstract
Near-infrared photoluminescence spectra of the n-doped gallium arsenide epilayer under heating lateral electric field conditions are studied. The field dependences of hot electron and hole temperatures are determined from photoluminescence spectra and from solving the power balance equation using current–voltage characteristic. Polarization anisotropy of the photoluminescence radiation arising due to the anisotropy of hot electron distribution function and angular dependence of the interband optical matrix element in the momentum space is observed and investigated. The obtained experimental data are in satisfactory agreement with the theoretical model. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
22. Domain switching and shear-mode piezoelectric response induced by cross-poling in polycrystalline ferroelectrics.
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Hall, D. A., Daniel, L., Watson, M., Condie, A., Comyn, T. P., Kleppe, A. K., and Withers, P. J.
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LEAD zirconate titanate , *PIEZOELECTRIC ceramics , *ELECTRIC fields , *STRAIN tensors , *X-ray diffraction , *ELECTROMECHANICAL effects , *SHEAR strain - Abstract
The mechanisms contributing to the electromechanical response of piezoelectric ceramics in the shear mode have been investigated using high-energy synchrotron x-ray diffraction. Soft lead zirconate titanate ceramic specimens were subjected to an electric field in the range 0.2–3.0 MV m−1, perpendicular to that of the initial poling direction, while XRD patterns were recorded in transmission. At low electric field levels, the axial strains remained close to zero, but a significant shear strain occurred due to the reversible shear-mode piezoelectric coefficient. Both the axial and shear strains increased substantially at higher field levels due to irreversible ferroelectric domain switching. Eventually, the shear strain decreased again as the average remanent polarization became oriented toward the electric field direction. The lattice strain and domain orientation distributions follow the form of the total strain tensor, enabling the domain switching processes to be monitored by the rotation of the principal strain axis. Reorientation of this axis toward the electric field direction occurred progressively above 0.6 MV m−1, while the angle of rotation increased from 0° to approximately 80° at the maximum field of 3.0 MV m−1. A strong correlation was established between the effective strains associated with different crystallographic directions, which was attributed to the effects of elastic coupling between grains in the polycrystal. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
23. Pulse electroosmotic flow of Newtonian fluids in parallel plate microchannels under triangular and half-sinusoidal pulse electric fields.
- Author
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Li, Dongsheng, Li, Haibin, and Liu, Jiaofei
- Subjects
- *
ALTERNATING currents , *NEWTONIAN fluids , *MICROCHANNEL plates , *ELECTRIC fields , *MICROFLUIDIC devices - Abstract
Unlike the conventional electroosmotic flow (EOF) driven by direct current and alternating current electric fields, this study investigates the pulse EOF of Newtonian fluids through a parallel plate microchannel actuated by pulse electric fields. Specifically, the pulses considered encompass triangular and half-sinusoidal pulse waves. By applying the Laplace transform method and the residual theorem, the analytical solutions for the velocity and volumetric flow rate of the pulse EOF associated with these two pulse waves are derived, respectively. The influence of pulse width a ¯ and electrokinetic width K on velocity is further considered, while the volumetric flow rate as a function of time t ¯ and electrokinetic width K is examined separately. A comparison of the volumetric flow rates related to these two pulse waves under varying parameters is also conducted. The research findings indicate that irrespective of the pulse wave, a broader pulse width results in a prolonged period and increased amplitude of the velocity profile. Elevating the electrokinetic width yields higher near-wall velocities, with negligible effect on near-center velocities. It is noteworthy that regardless of the electrokinetic width, the near-wall velocity exceeds that of the near-center during the first half-cycle, while the situation reverses during the second half-cycle. The volumetric flow rate varies periodically with time, initially surging rapidly with electrokinetic width before gradually stabilizing at a constant level. More interestingly, independent of pulse width and electrokinetic width, the volumetric flow rates linked to the half-sinusoidal pulse wave consistently surpass those of the triangular pulse wave. For any pulse width, the volumetric flow rates corresponding to the two pulse waves grow with higher electrokinetic widths, especially prominent at alternating intervals of the two half-cycles within a complete cycle. These findings have important implications for improving the design and optimization of microfluidic devices in engineering and biomedical applications utilizing pulse EOF. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
24. Phosphorene junctions as a platform for spin-selective quantum dots in next-generation devices.
- Author
-
Mahdavifar, Maryam, Khoeini, Farhad, and Peeters, François M.
- Subjects
- *
QUANTUM dot devices , *ENERGY levels (Quantum mechanics) , *QUANTUM computing , *CRYSTAL orientation , *ELECTRIC fields , *QUANTUM dots - Abstract
The impact of vacancies on spin-resolved electronic properties of quantum dots (QDs) in phosphorene-based junctions is investigated numerically. Regardless of the crystal orientation, a phosphorene nanoribbon containing a monovacancy is found to exhibit a topological quasi-flatband that emerges within the bandgap. The electronic properties of QDs, including spatial confinement and energy level distribution, can be strongly tuned by controlling the topological structure of the QDs and by applying electric fields. Additionally, these QDs exhibit remarkable spin-selective properties under a ferromagnetic exchange field, enabling the manipulation of QD features. This opens up the potential for novel applications such as quantum computing, magnetic sensing, spin-based light emission. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
25. Interplay of c- and a-domains on the anomalous electrocaloric effect in BaTiO3 (001) single crystals.
- Author
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Chatterjee, Subhashree, Yadav, Kusampal, Barman, Shubhankar, Hasina, Dilruba, and Mukherjee, Devajyoti
- Subjects
- *
PYROELECTRICITY , *ADIABATIC temperature , *SINGLE crystals , *FERROELECTRIC materials , *ELECTRIC fields - Abstract
Electrocaloric effects of adiabatic temperature change via the application of external electric fields are explored for energy-efficient solid-state refrigeration. These effects are typically estimated from the thermodynamic analyses of polarization and field in electrocaloric materials, which implies that higher field application gives larger temperature changes. However, this may not be always true. Here, using both indirect and direct methods, we report an anomalous effect where larger thermal changes occur by applications of lower fields in a multi-domain BaTiO3 (001) single crystal. A large temperature change of 1.9 K under a low field change of 8 kV/cm at 404 K is observed in a multi-domain BaTiO3 (001) single crystal in comparison to that of 1.4 K at a high field change of 30 kV/cm. We attribute this counterintuitive effect to the interplay of the c- and a-domains in the BaTiO3 (001) single crystal under the influence of temperature and field changes. This work provides a fundamental understanding of the complex role of domains in governing the electrocaloric response of ferroelectric materials which is often overlooked but critical for their practical applications. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
26. Kinetically blocked self-assembly of colloidal strings with tunable interactions in magnetic fields.
- Author
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Yakovlev, Egor V., Simkin, Ivan V., Shirokova, Anastasia A., Kohanovskaya, Alexandra V., Gursky, Konstantin D., Dragun, Maksim A., Nasyrov, Artur D., Yurchenko, Stanislav O., and Kryuchkov, Nikita P.
- Subjects
- *
METASTABLE states , *MAGNETIC fields , *POTENTIAL barrier , *SUBSTRATES (Materials science) , *ELECTRIC fields - Abstract
Tunable self-assembly driven by external electric or magnetic fields is of significant interest in modern soft matter physics. While extensively studied in two-dimensional systems, it remains insufficiently explored in three-dimensional systems. In this study, we investigated the formation of vertical strings from an initial monolayer system of particles deposited on a horizontal substrate under the influence of an external magnetic field using experiments, computer simulations, and theoretical frameworks. We demonstrated that the main mechanism of string self-assembly is merging, driven by the interplay between gravity and induced tunable interparticle interactions. During this process, the system has to overcome a saddle point on the energy landscape, whose height increases with the string height. At a certain point, further self-assembly becomes kinetically blocked in a metastable state, far from equilibrium. This contrasts sharply with the typical scenario for tunable self-assembly in two dimensions, where the resulting structures usually correspond to the equilibrium state. Therefore, this finding opens up opportunities for more detailed control of three-dimensional tunable self-assembly by designing and tuning various potential barriers along the kinetic pathways. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
27. Nonlinear conductivity of aqueous electrolytes: Beyond the first Wien effect.
- Author
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Berthoumieux, Hélène, Démery, Vincent, and Maggs, Anthony C.
- Subjects
- *
CONDUCTIVITY of electrolytes , *AQUEOUS electrolytes , *MOLECULAR dynamics , *ELECTRIC fields , *COMPUTER simulation - Abstract
The conductivity of strong electrolytes increases under high electric fields, a nonlinear response known as the first Wien effect. Here, using molecular dynamics simulations, we show that this increase is almost suppressed in moderately concentrated aqueous electrolytes due to the alignment of the water molecules by the electric field. As a consequence of this alignment, the permittivity of water decreases and becomes anisotropic, an effect that can be measured in simulations and reproduced by a model of water molecules as dipoles. We incorporate the resulting anisotropic interactions between the ions into a stochastic density field theory and calculate ionic correlations as well as corrections to the Nernst–Einstein conductivity, which are in qualitative agreement with the numerical simulations. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
28. Role of cavity strong coupling on single electron transfer reaction rate at electrode–electrolyte interface.
- Author
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Hayashi, Takahiro, Fukushima, Tomohiro, and Murakoshi, Kei
- Subjects
- *
ELECTRIC fields , *ENERGY conversion , *POLARITONS , *PHOTONS , *MOLECULES - Abstract
The physicochemical properties of molecules can be modulated through polariton formation under strong electromagnetic confinement. Here, we discuss the possibility of exploiting this phenomenon to increase the electron transfer rate at an electrode–electrolyte interface. Electron transfer theory under strong electromagnetic confinement can be extended to the electrode–electrolyte interface, and single-electron transfer reactions can be simulated using Gerischer's theory. Although single electron transfer in free space is well described using Marcus theory, the vacuum electric field can facilitate an additional electron transfer pathway via virtual photon excitation under cavity strong coupling conditions. Therefore, this binary reaction pathway for single electron transfer can yield a quasi-two-particle electron transfer process. This quantum behavior can dominate when the mode volume is small and when there are a large number of molecules in the vacuum electric field. Exploitation of polaritons in single electron transfer reactions can lead to enhanced electrochemical energy conversion systems. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
29. Improving the polarization switching properties of wurtzite AlN by introducing IV–IV/AlN superlattice and P-doping.
- Author
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Huang, Mingyue, Duan, Tianpeng, Jiang, Jie, and Yang, Qiong
- Subjects
- *
SWITCHING costs , *ACTIVATION energy , *DENSITY functional theory , *WURTZITE , *ELECTRIC fields - Abstract
The large coercive electric field is the main obstacle for the application of wurtzite ferroelectrics in the memory devices. To explore the effective methods to reduce the coercive electric field of wurtzite ferroelectrics, in this work, after screening a series of possible candidates, (MC)1/(AlN)n (M = Ti, Zr) superlattices and anion P-doping are both chosen to regulate the switching energy barrier of wurtzite AlN based on the density functional theory calculations. It is found that the polarization switching energy barriers of wurtzite AlN gradually decrease by increasing the ratio of the MC (M = Ti, Zr) layer. When the ratio of the MC layer is up to 33%, the polarization switching energy barriers of (TiC)1/(AlN)n and (ZrC)1/(AlN)n are decreased by 68% and 55%, respectively, compared with that of pure wurtzite AlN. The anionic P-doping in AlN results in a 48% lower energy barrier. Also, the ferroelectric polarization in the designed superlattices and P-doped AlN is well maintained compared to pure AlN. Thus, the results show that the (MC)1/(AlN)n (M = Ti, Zr) superlattices and anion P-doping approaches are effective in improving the polarization switching properties of wurtzite AlN. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
30. Effects of A-site configuration entropy on the dielectric properties in tetragonal tungsten bronze ceramics.
- Author
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Ou, Yi Bang, Song, Jia Wen, Wu, Shu Ya, Liu, Xiao Qiang, Zhu, Xiao Li, and Chen, Xiang Ming
- Subjects
- *
PERMITTIVITY , *DIELECTRIC properties , *TUNGSTEN bronze , *DIELECTRIC polarization , *ELECTRIC fields , *RARE earth metals - Abstract
A series of Sr4.5Ca0.5MTi3Nb7O30 [M = La0.5Nd0.5 (LN), La1/3Nd1/3Sm1/3 (LNS) and La0.25Nd0.25Sm0.25Eu0.25 (LNSE)] ceramics with different A-site configuration entropy were prepared, and the effects of the A-site configuration entropy on the dielectric and ferroelectric properties were investigated. Due to the combined effect of high entropy and solid solution, the best dielectric performance was achieved in the LNS composition, where the dielectric constant remained around 650 in the temperature range of 269–515 K with a change rate of less than 15%. Under the DC high voltage field up to 67 kV/cm, each component's polarization characteristics and dielectric constants obtained good electric field stability and temperature stability under a high electric field. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
31. Extraordinary terahertz transmission and field enhancement via hybrid surface plasmon coupling in rhombic and bow-tie composite aperture metasurface.
- Author
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Yan, Shuzhan, Zhang, Xue, Chen, Shuyuan, and Zeng, Jiahao
- Subjects
- *
SURFACE plasmons , *COUPLINGS (Gearing) , *ELECTRIC fields , *BIOSENSORS , *BANDWIDTHS - Abstract
Metasurface that achieves extraordinary terahertz transmission (ETT) and local electric field enhancement (FE) holds significant potential for terahertz studies involving extremely low concentrations of target materials. In this study, we explore a composite aperture metasurface capable of both ETT and local FE. By inserting bow-tie apertures in the "minimum-resonance" zone between four adjacent rhombic lattices, a local FE factor is achieved. Notably, adjusting the configuration of the bow-tie aperture enhances the coupling between surface plasmons, thereby expanding the transmission bandwidth. Through parameter optimization, the metasurface achieves a peak transmission exceeding 95% and a transmittance above 80% in the frequency range of 2.44–3.65 THz, while simultaneously exhibiting a maximum local FE factor of 1005 at 3.45 THz. This approach offers a promising avenue for the design of metasurfaces for spectroscopy and biosensor applications. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
32. One- and two-photon excitation dynamics using semiclassical electron force field model.
- Author
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Yamada, Atsushi
- Subjects
- *
ELECTRONIC excitation , *QUANTUM theory , *CRYSTALS , *CONDENSED matter , *ELECTRIC fields - Abstract
We have extended the semiclassical-based electron force-field simulation by introducing field–electron interaction to enable us to describe linear and nonlinear electronic excitation dynamics of a condensed matter system with low computational cost. To verify the simulation method, as a first step, numerical examples of interaction dynamics of simple systems (H atom, SiH4 molecule, and Si crystalline solid) with applied short electric field pulse as well as the obtained absorbed energies by the one- and two-photon excitations have been reported along with comparison with quantum dynamics calculations as reference. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
33. Electric-field-induced enhancement of exciton binding energy in one-dimensional phosphorene atomic chain.
- Author
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Huang, Wenzhuo, Zhong, Jun, and Sheng, Weidong
- Subjects
- *
BINDING energy , *ELECTRIC fields , *PHOSPHORENE , *EXCITON theory , *ELECTRONS - Abstract
An electric field normally increases the separation between the electron and hole in an exciton without intrinsic polarization and suppresses their Coulombic interaction, resulting in the reduction of its binding energy. Our study of one-dimensional (1D) excitons in phosphorene atomic chains, by using the exact diagonalization method, however, reveals that an electric field applied along the chain axis actually increases the exciton binding energies. Further analysis shows that the electric field tends to enhance the long-range interaction between the electron and hole while suppressing their short-range interaction by inducing an alternating charge distribution along the atomic chain. The zigzag symmetry is believed to account for this unique excitonic phenomenon in the 1D system. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
34. Achieving high piezoelectric performance in Pb(Mg1/3Nb2/3)O3–PbTiO3 ferroelectric single crystals through pulse poling technique.
- Author
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Chen, Shuli, Gai, Xuezhou, Xiong, Ruibin, Liang, Min, Wang, Zujian, Su, Bin, Su, Rongbing, Liu, Jianqun, Liu, Ying, and He, Chao
- Subjects
- *
FERROELECTRIC crystals , *SINGLE crystals , *PERMITTIVITY , *DIELECTRIC properties , *ELECTRIC fields - Abstract
To maximize the piezoelectric performance of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystals, a pulse poling (PP) method is proposed in this study. This study investigates the effects of pulse poling on the piezoelectric and dielectric properties of these PMN–PT single crystals and explores the polarization rotation mechanisms. Our findings indicate a significant improvement in the piezoelectric properties postpulse poling. The optimal PP conditions are identified as 30 pulse numbers at a pulsed electric field of 5 kV/cm. The dielectric constant ɛT33/ɛ0 and piezoelectric coefficient d33 of PMN–0.28PT post PP are 7000–7700 and 2200–2530 pC/N, respectively, representing increases of 49% and 66% compared with those of postdirect current poling (DCP). Additionally, the domain structures of the PMN–0.28PT single crystals after various DCP and PP treatments are examined and compared using piezoelectric force microscopy. The enhanced piezoelectric properties are attributed to the finer domain structures, as well as increased domain wall density achieved through PP. This research introduces a novel domain engineering approach to improve the electromechanical properties of relaxor ferroelectric single crystals. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
35. Faraday rotation method improves the upper limit of the electron electric–dipole–moment sensitivity.
- Author
-
Xiao, Huagang, Zhang, Ruijie, and Gao, Tao
- Subjects
- *
FARADAY effect , *QUADRUPOLE moments , *MAGNETIC moments , *EXCITED states , *ELECTRIC fields - Abstract
The electron electric–dipole–moment (eEDM) is a powerful tool for exploring new particles. The candidates for eEDM search are heavy atoms and their molecules, which are well known for the obvious relativistic effect. Lead atom is considered to be the most ideal relativistic atom [Park et al., Nat. Commun. 11(1), 815 (2020)]. PbH molecule is an important representative of the Pb compound and is considered a cold candidate molecule due to the high diagonal Franck–Condon factors. We systematically investigated the (eEDM) searches of PbH using a two-component approach. The parity- and time-reversal symmetry violation constants of ground and excited states, including internal effective electric field Eeff, electron–nucleon scalar–pseudoscalar interaction constant WP,T, and nuclear magnetic quadrupole moment, were obtained and compared to other molecules. In addition, we designed two experimental methods to measure the sensitivity of the eEDM, indicating that the Faraday rotation method could greatly improve its sensitivity. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
36. Immersed boundary method for dynamic simulation of polarizable colloids of arbitrary shape in explicit ion electrolytes.
- Author
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Krucker-Velasquez, Emily, Swan, James W., and Sherman, Zachary
- Subjects
- *
ELECTRIC fields , *ELECTROSTATIC interaction , *GRAPHICS processing units , *ELECTROSTATICS , *TORQUE - Abstract
We develop a computational method for modeling electrostatic interactions of arbitrarily shaped, polarizable objects on colloidal length scales, including colloids/nanoparticles, polymers, and surfactants, dispersed in explicit ion electrolytes and nonionic solvents. Our method computes the nonuniform polarization charge distribution induced in a colloidal particle by both externally applied electric fields and local electric fields arising from other charged objects in the dispersion. This leads to expressions for electrostatic energies, forces, and torques that enable efficient molecular dynamics and Brownian dynamics simulations of colloidal dispersions in electrolytes, which can be harnessed to accurately predict structural and transport properties. We describe an implementation in which colloidal particles are modeled as rigid composites of small spherical beads that tessellate the surface of the particle. The electrostatics calculations are accelerated using a spectrally accurate particle-mesh-Ewald technique implemented on a graphics processing unit and regularized such that the electrostatic calculations are well-defined even for overlapping bodies. We illustrate the effectiveness of this approach with a comprehensive set of calculations: the induced dipole moments and forces for individual, paired, and lattice configurations of spherical colloids in an electric field; the induced dipole moment and torque for anisotropic particles subjected to an electric field; the equilibrium ion distribution in the double layer surrounding charged colloids; the dynamics of charged colloids; and the behavior of ions in the double layer of a polarizable colloid under the influence of an electric field. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
37. A scattering matrix approach to the effective mass dependence of tunneling current through heterojunctions.
- Author
-
Hernandez, Nathaniel, Cahay, Marc, O'Mara, Jonathan, Ludwick, Jonathan, Walker Jr., Dennis E., Back, Tyson, and Hall, Harris
- Subjects
- *
S-matrix theory , *FIELD emission , *RESONANT tunneling , *ELECTRIC fields , *NUMERICAL calculations - Abstract
A scattering matrix technique is used to calculate the longitudinal and transverse energy dependence of the transmission probability through various heterostructures using both the BenDaniel–Duke (BD) and the lesser known Zhu–Kroemer (ZK) boundary conditions to take into account the spatial dependence of the effective mass. We first illustrate the large difference in the transmission probabilities calculated using both boundary conditions for the simple problems of tunneling through a potential step, a single rectangular barrier, and a resonant tunneling device. Then, we present numerical calculations of the external electric field dependence of the field emission (FE) current from a n-doped GaAs semiconductor/vacuum interface using both boundary conditions, showing that the BD boundary conditions underestimate the FE current for large values of the applied external electrostatic field. A comparison of calculated FE characteristics with FE data may be a way to determine the appropriate boundary conditions to solve tunneling problems through heterostructures with spatially varying effective mass. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
38. Microscopic view on the polarization-resolved S-SHG intensity of the vapor/liquid interface of pure water.
- Author
-
Le Breton, G., Loison, C., Vynck, K., Benichou, E., and Bonhomme, O.
- Subjects
- *
SECOND harmonic generation , *MOLECULAR orientation , *MOLECULAR probes , *MOLECULAR structure , *ELECTRIC fields - Abstract
Second harmonic generation (SHG) is a nonlinear optical phenomenon where two photons at the frequency ω combine to form a single photon at the second-harmonic frequency 2ω. Since that second-order process is very weak in bulk isotropic media, optical SHG responses of interfaces provide a powerful and versatile technique to probe the molecular structure and dynamics of liquid interfaces. Both local dipole contributions and non-local quadrupole contributions can be interesting to investigate different properties of the interface, such as the molecular orientation or the charge density. However, a major difficulty is to comprehend the link between the S-SHG intensity and molecular details. This article reports a numerical approach to model the polarization-resolved SHG intensities of a model vapor/liquid interface of pure water. The influence of the interfacial local environment on the hyperpolarizability is taken into account using quantum mechanical/molecular mechanics calculations. The numerical predictions are in very good agreement with experiments. We detail the hypotheses made during the modeling steps and discuss the impact of various factors on the modeled SHG intensities, including the description of the exciting field in the interfacial layer, the effect of neighboring molecules on the second-harmonic polarization, and the presence of an additional static electric field at the interface. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
39. Dynamic permittivity of confined water under a static background field.
- Author
-
Bratko, D. and Mulpuri, N.
- Subjects
- *
POROUS materials , *MOLECULAR dynamics , *ELECTRIC fields , *INTERFACIAL bonding , *PERMITTIVITY , *SURFACE charges - Abstract
Molecular and collective reorientations in interfacial water are by-and-large decelerated near surfaces subjected to outgoing electric fields (pointing from surface to liquid, i.e., when the surface carries positive charge). In incoming fields at negatively charged surfaces, these rates show a nonmonotonic dependence on field strength where fastest reorientations are observed when the field alignment barely offsets the polarizing effects due to interfacial hydrogen bonding. This extremum coincides with a peak of local static permittivity. We use molecular dynamics simulations to explore the impact of background static field on high frequency AC permittivity in hydration water under an electric field mimicking the conditions inside a capacitor where one of the confinement walls is subject to an outgoing field and the other one to an incoming field. At strong static fields, the absorption peak undergoes a monotonic blue shift upon increasing field strength in both hydration layers. At intermediate fields, however, the hydration region at the wall under an incoming field (the negative capacitor plate) features a red shift coinciding with maximal static-permittivity and reorientation-rate. The shift is mostly determined by the variation of the inverse static dielectric constant as proposed for mono-exponentially decaying polarization correlations. Conversely, hydration water at the opposite (positively charged) surface features a monotonic blue shift consistent with conventional saturation. The sensitivity of absorption peaks on the field suggests that surface charge densities could be deduced from sub-THz dielectric spectroscopy experiments in porous materials when interfaces accommodate a major fraction of water contained in the system. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
40. Water compression induced ionic negative differential resistance in nanopores.
- Author
-
Tan, Haojing, He, Zhi, Zhou, Ruhong, and Feng, Jiandong
- Subjects
- *
MOLECULAR dynamics , *FLUID dynamics , *ION transport (Biology) , *INDUCTIVE effect , *ELECTRIC fields - Abstract
The mass transport behavior through nanoscale channels, greatly influenced by the structures and dynamics of nanoconfined water, plays an essential role in many biophysical processes. However, the dynamics of nanoconfined water under an external field and its effects are still not fully understood. Here, on the basis of molecular dynamics simulations, we theoretically show that the ionic current of [Bmim][PF6] through narrow pores in graphene membrane exhibits an ionic negative differential resistance effect—the ionic current decreases as the voltage increases over a certain threshold. This effect arises from the violation of traditional fluid dynamics as the assumption of continuity and homogeneity of fluids is no longer effective in ultrathin nanopores. The gradient of electric field around the atomic-thin layer produces a strong gradient force on the polarized water inside the nanopore. This dielectrophoretically compressed water leads to a hydrostatic force that repels ions from entering the nanopore. Our findings may advance the understanding of hydrostatic mechanism, which governs ion transport through nanopores. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
41. FMO-LC-TDDFTB method for excited states of large molecular assemblies in the strong light-matter coupling regime.
- Author
-
Einsele, Richard, Philipp, Luca Nils, and Mitrić, Roland
- Subjects
- *
POLARIZATION (Electricity) , *EXCITED states , *MOLECULAR orbitals , *ELECTRIC fields , *MOLECULAR dynamics - Abstract
We present a new methodology to calculate the strong light-matter coupling between photonic modes in microcavities and large molecular aggregates that consist of hundreds of molecular fragments. To this end, we combine our fragment molecular orbital long-range corrected time-dependent density functional tight-binding methodology with a generalized Tavis–Cummings Hamiltonian. We employ an excitonic Hamiltonian, which is built from a quasi-diabatic basis that is constructed from locally excited and charge-transfer states of all molecular fragments. To calculate polaritonic states, we extend our quasi-diabatic basis to include photonic states of a microcavity and derive and implement the couplings between the locally excited states and the cavity states and built a Tavis–Cummings Hamiltonian that incorporates the intermolecular excitonic couplings. Subsequently, we demonstrate the capability of our methodology by simulating the influence of the electric field polarization on the polaritonic spectra for a tetracene aggregate of 125 monomers. Furthermore, we investigate the dependence of the splitting of the upper and lower polaritonic branches on the system size by comparing the spectra of five different tetracene clusters. In addition, we investigate the polariton dispersion of a large tetracene aggregate for electric field polarizations in the x, y, and z directions. Our new methodology can facilitate the future study of exciton dynamics in complex molecular systems, which consist of up to hundreds of molecules that are influenced by strong light–matter coupling to microcavities. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
42. Cavity Born–Oppenheimer approximation for molecules and materials via electric field response.
- Author
-
Bonini, John, Ahmadabadi, Iman, and Flick, Johannes
- Subjects
- *
ELECTRIC fields , *OPTICAL resonators , *MOLECULAR crystals , *DEGREES of freedom , *DENSITY functional theory , *POLARITONS - Abstract
We present an ab initio method for computing vibro-polariton and phonon-polariton spectra of molecules and solids coupled to the photon modes of optical cavities. We demonstrate that if interactions of cavity photon modes with both nuclear and electronic degrees of freedom are treated on the level of the cavity Born–Oppenheimer approximation, spectra can be expressed in terms of the matter response to electric fields and nuclear displacements, which are readily available in standard density functional perturbation theory implementations. In this framework, results over a range of cavity parameters can be obtained without the need for additional electronic structure calculations, enabling efficient calculations on a wide range of parameters. Furthermore, this approach enables results to be more readily interpreted in terms of the more familiar cavity-independent molecular electric field response properties, such as polarizability and Born effective charges, which enter into the vibro-polariton calculation. Using corresponding electric field response properties of bulk insulating systems, we are also able to obtain the Γ point phonon-polariton spectra of two dimensional (2D) insulators. Results for a selection of cavity-coupled molecular and 2D crystal systems are presented to demonstrate the method. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
43. Identification and classification of clusters of dipolar colloids in an external field.
- Author
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Skipper, Katherine, Moore, Fergus J., and Royall, C. Patrick
- Subjects
- *
COLLOIDS , *CLUSTERING of particles , *SEARCH algorithms , *ELECTRIC fields , *COMPUTER simulation - Abstract
Colloids can acquire a dipolar interaction in the presence of an external AC electric field. At high field strength, the particles form strings in the field direction. However, at weaker field strength, competition with isotropic interactions is expected. One means to investigate this interplay between dipolar and isotropic interactions is to consider clusters of such particles. Therefore, we have identified, using the GMIN basin-hopping tool, a rich library of lowest energy clusters of a dipolar colloidal system, where the dipole orientation is fixed to lie along the z axis and the dipole strength is varied for m-membered clusters of 7 ≤ m ≤ 13. In the regime where the isotropic and dipolar interactions are comparable, we find elongated polytetrahedral, octahedral, and spiral clusters as well as a set of non-rigid clusters, which emerge close to the transition to strings. We further implement a search algorithm that identifies these minimum energy clusters in bulk systems using the topological cluster classification [J. Chem. Phys. 139 234506 (2013)]. We demonstrate this methodology with computer simulations, which show instances of these clusters as a function of dipole strength. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
44. Circuits for the spectroscopic readout of bits from molecular quantum-dot cellular automata.
- Author
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Cong, Peizhong, Rocque, Alexander, and Blair, Enrique P.
- Subjects
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CELLULAR automata , *SIGNAL-to-noise ratio , *ELECTRIC fields , *TRANSISTORS , *INFORMATION processing - Abstract
Molecular quantum-dot cellular automata (QCA) may provide high speed, low-power, classical information processing in the post-CMOS era. The readout of molecular QCA bits is challenging because the molecules may be much smaller than transistors and even single-electron transistors. This paper builds on a recent proposal for the spectroscopic readout of bits from asymmetric QCA molecules. Here, we propose circuits for fanning out a bit onto a large QCA circuit to increase the spectroscopic signal-to-noise ratio. As the number of molecules in a fanout circuit grows, the internal bias of each asymmetric cell accumulates, and the circuit may become stuck, tolerating only a very small internal bias. We also propose the use of an applied electric field to compensate for a candidate molecule's internal bias, thereby restoring switchability, even when the internal bias is significant. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
45. Low driving voltage and high reliability 1.54 μm electroluminescence from SnO2:Er/p-Si heterostructured devices via energy transfer effect.
- Author
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Wu, Yunfeng, Pang, Houwei, Wang, Yuan, Lin, Sichen, Wang, Lei, Yang, Deren, and Li, Dongsheng
- Subjects
- *
LIGHT sources , *ELECTRIC fields , *OPTICAL rotation , *ENERGY transfer , *ION emission - Abstract
Erbium-doped SnO2 films and devices are fabricated on silicon substrates, and the 1.54 μm emission of erbium ions is realized via energy transfer from the SnO2 host. It is found that the luminescence intensity for SnO2:Er film can be enhanced, by increasing the optical activity and transition probability of Er3+ ions with fluorine codoping. Moreover, the device prepared by the fluorine codoped SnO2 film presents a low turn-on voltage of 1.6 V and an onset electric field of 0.18 MV/cm. The unpackaged device operated for 1028h in the atmosphere, then continued to function at 40 °C/30% RH during 1003 h, with less than 10% optical power attenuation. Through further optimizing the preparation process, the optimal device exhibits an optical power density of 38.5 μW/cm2 at 1.55 μm, due to the improved crystalline quality together with the number of sensitizers. This work demonstrates the practical application potential in silicon-based light sources from erbium-doped SnO2 devices. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
46. Mechanically activated and deactivated ion transport across nanopores with heterogeneous surface charge distributions.
- Author
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Paul, Arghyadeep and Aluru, N. R.
- Subjects
- *
VOLTAGE , *ION transport (Biology) , *ELECTRIC fields , *ION channels , *NANOPORES - Abstract
To mimic the intricate and adaptive functionalities of biological ion channels, electrohydrodynamic ion transport has been studied extensively, albeit mostly, across uniformly charged nanochannels. Here, we analyze the ion transport under coupled electric field and pressure across heterogeneously charged nanopores with oppositely charged sections on their lateral surface. We only consider such pores with symmetric hourglass-like and cylindrical shapes to focus on the effects of the non-uniform surface charge distribution. Finite-element simulations of a continuum model demonstrate that a pressure applied in either direction of the pore-axis equally suppresses or amplifies the ionic conductance, depending on the electric field polarity, by distorting the quasi-static distribution of ions in the pore. The resulting anomalous mechanical deactivation and activation of ionic current under opposite voltage biases exhibit the functional modularity of our setup, while their intensities are highly tunable, substantially greater than those of analogous behaviors in other nanochannels, and fundamentally correlated to ionic current rectification (ICR) in our pores. A detailed study of ICR subsequently reveals its counterintuitive non-monotonous variations, in the pores, with the magnitude of applied voltage and the pore length, that can help optimize their diode-like behavior. We further illustrate that while the hourglass-shaped nanopores yield the more efficient mechanical suppressors of ion transport, their cylindrical analogs are the superior rectifiers and mechanical amplifiers of ion conduction. Therefore, this article provides a blueprint for the strategic design of nanofluidic circuits to attain a robust, modular, and tunable control of ion transport under external electrical and mechanical stimuli. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
47. Piezo-photocatalysis synergy in γ-GeSe for highly efficient oxygen evolution reaction.
- Author
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Zhang, Tianqi, Zhou, Long, Chen, Guobo, Wei, Songrui, Sun, Rong, Li, Yunping, Meng, Lijian, Zhang, Guanglong, Xia, Shuwei, Wang, Zhongchang, and Qiu, Meng
- Subjects
- *
PIEZOELECTRICITY , *OXYGEN evolution reactions , *ENERGY conversion , *PIEZOELECTRIC materials , *ELECTRIC fields - Abstract
Solar-driven semiconductor photocatalysts are highly appealing in applications of environmental remediation and energy conversion. However, photocatalytic reactions, particularly oxygen evolution reaction (OER), are often constrained by the swift recombination of electron–hole pairs, thereby resulting in low reaction efficiency. Although it is effective to separate charge carriers by constructing heterojunctions to form built-in electric field, the lattice mismatch and inefficient interlayer charge transfer of heterojunctions in the photocatalysts limit their further development. Here, we propose a new strategy by constructing an internal electric field for OER through an individual piezoelectric two-dimensional material. The results indicate that the piezoelectric effect regulates the electronic structure, reduces bandgap, improves light absorption efficiency, and that the displacement of positive and negative charge centers is the key factor in the enhanced OER. This research indicates the feasibility of combining piezoelectric properties of two-dimensional materials with OER (1.19 eV), providing new insights and guidance for applying the piezoelectric effect in the OER and opening up a way to promote efficient separation of charge carriers. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
48. Multicaloric response tuned by electric field in cylindrical MnAs/PZT magnetoelectric composite.
- Author
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Amirov, Abdulkarim A., Koliushenkov, Maksim A., Mukhuchev, Abdula A., Yusupov, Dibir M., Govorina, Valeriya V., Neznakhin, Dmitriy S., Govor, Gennady A., and Aliev, Akhmed M.
- Subjects
- *
PIEZOELECTRICITY , *VOLTAGE , *STRAINS & stresses (Mechanics) , *ELECTRIC fields , *PHASE transitions , *PIEZOELECTRIC composites , *MAGNETOCALORIC effects - Abstract
The possibility observation of the electric field controlled multicaloric response through quasi-isostatic compression as a result of the converse piezoelectric effect was demonstrated on the cylindrical type magnetoelectric composite MnAs/PZT. It was shown that an electric voltage of 100 V corresponding to an electric field of E ∼0.3 kV/mm applied to the walls of the piezoelectric component PZT of the MnAs/PZT composite contributes to an increase in the maximum adiabatic temperature change by 0.2 K in the temperature range of the magnetostructural phase transition of MnAs ∼317 K at a magnetic field change of 1.8 T. Numerical analysis using the finite element method has shown that an electric field voltage of 100 V is capable of creating a quasi-isostatic mechanical stress in the region inside a cylindrical PZT tube of ∼3 MPa. Moreover, in the region of weak pressures up to 10 MPa, the contribution to the total adiabatic temperature change from piezo-mechanical compression linearly depends on the electrical voltage that can be used for control by magnetic and caloric properties of multicaloric materials. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
49. Edge sites regulation, strain and electric field effect on MoS2/CoS2 heterojunction catalysts for hydrogen evolution reaction.
- Author
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Zhang, Jiahao, Kang, Chen, Ren, Junfeng, Chen, Meina, and Lin, Zijing
- Subjects
- *
ELECTRIC field effects , *CATALYSIS , *HYDROGEN evolution reactions , *CATALYTIC activity , *ELECTRIC fields , *HETEROJUNCTIONS - Abstract
Heterojunction catalysts in the field of hydrogen evolution reaction (HER) from electrocatalytic water splitting have recently become a hot research topic. In this paper, we systematically calculated the HER catalytic performance of a MoS2/CoS2 heterojunction for the first time, considering the effect of edge sites regulation, strain and electric field. The results indicate that the MoS2/CoS2 heterojunction exhibits synergistic catalytic performance compared to MoS2 and CoS2, the HER catalytic activity of which can be improved by exposing more edge sites or regulating the S content on the edges, with an optimized ratio of 25%. Surprisingly, applying strain has a slight effect on the catalytic activity of the edge, however, an obvious effect on the basal plane. For example, applying 2% tensile strain on the MoS2/CoS2 heterojunction can improve the edge catalytic performance by 13%, and for the basal plane, this value can reach 92%. In this case, the catalytic performance of the basal plane is better than that of the edge with 2% and without strain. Since the basal plane accounts for the majority of the two-dimensional catalysts, the catalytic performance of the basal plane is generally much lower than that of the edge. This discovery is of great significance, which means by adjusting strain, the catalytic performance of the heterojunction catalyst is likely to be improved by orders of magnitude. Moreover, considering the actual experimental process, we also calculated the effect of the electric field and found that 0.7 V/Å electric field can enhance the HER catalytic activity of the MoS2/CoS2 heterojunction by 23%. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
50. Permittivity enhancement of Al2O3/ZrO2 dielectrics with the incorporation of Pt nanoparticles.
- Author
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Zhu, Bao, Shang, Ze, Wang, Chenyan, Wu, Xiaohan, and Zhang, David Wei
- Subjects
- *
ELECTRIC breakdown , *ELECTRIC currents , *ATOMIC layer deposition , *DIELECTRIC breakdown , *ELECTRIC fields - Abstract
Al2O3/ZrO2 (A/Z) layers with embedded Pt nanoparticles (Pt-nps) at the interface of A/Z have been used to create a dielectric film with an enhanced permittivity. The Pt-nps and dielectrics are both grown by the atomic layer deposition process, which is complementary metal–oxide–semiconductor compatible. In order to control the thickness ratio of Pt-nps in the overall dielectrics more easily, the thickness of the ZrO2 layer is changed from 12 to 30 nm with a fixed thickness of 12 nm for Al2O3 and constant growth cycles of 70 for Pt-nps. The results show that the introduction of Pt-nps is beneficial to the enhancement of the dielectric permittivity. As the thickness of ZrO2 is 30 nm, the capacitance density increases from 2.5 to 5.1 fF/μm2 with the addition of Pt-nps, i.e., a doubling of the capacitance density achieved. Additionally, the leakage current at 2 V increases from 1.1 × 10−8 to 1.5 × 10−7 A/cm2. Furthermore, the dielectric breakdown field decreases from 5.4 to 2.7 MV/cm. The electric field distribution simulation and charging–discharging test imply that interfacial polarization is built at the interface of Pt-nps and the dielectric films, which contributes to the dielectric permittivity enhancement, and local electric field increasing in the affinity of Pt-nps gives rise to the deterioration of the leakage current and breakdown electric field. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
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