Showing papers on "Electric field published in 2016"
TL;DR: The spin-plane double probe instrument (SDP) is part of the FIELDS instrument suite of the Magnetospheric Multiscale mission (MMS).
Abstract: The Spin-plane double probe instrument (SDP) is part of the FIELDS instrument suite of the Magnetospheric Multiscale mission (MMS). Together with the Axial double probe instrument (ADP) and the Electron Drift Instrument (EDI), SDP will measure the 3-D electric field with an accuracy of 0.5 mV/m over the frequency range from DC to 100 kHz. SDP consists of 4 biased spherical probes extended on 60 m long wire booms 90∘ apart in the spin plane, giving a 120 m baseline for each of the two spin-plane electric field components. The mechanical and electrical design of SDP is described, together with results from ground tests and calibration of the instrument.
591 citations
TL;DR: Experimental evidence is provided that the formation of carbon–carbon bonds is accelerated by an electric field, and a fivefold increase in the frequency of formation of single-molecule junctions is found.
Abstract: It is often thought that the ability to control reaction rates with an applied electrical potential gradient is unique to redox systems. However, recent theoretical studies suggest that oriented electric fields could affect the outcomes of a range of chemical reactions, regardless of whether a redox system is involved. This possibility arises because many formally covalent species can be stabilized via minor charge-separated resonance contributors. When an applied electric field is aligned in such a way as to electrostatically stabilize one of these minor forms, the degree of resonance increases, resulting in the overall stabilization of the molecule or transition state. This means that it should be possible to manipulate the kinetics and thermodynamics of non-redox processes using an external electric field, as long as the orientation of the approaching reactants with respect to the field stimulus can be controlled. Here, we provide experimental evidence that the formation of carbon-carbon bonds is accelerated by an electric field. We have designed a surface model system to probe the Diels-Alder reaction, and coupled it with a scanning tunnelling microscopy break-junction approach. This technique, performed at the single-molecule level, is perfectly suited to deliver an electric-field stimulus across approaching reactants. We find a fivefold increase in the frequency of formation of single-molecule junctions, resulting from the reaction that occurs when the electric field is present and aligned so as to favour electron flow from the dienophile to the diene. Our results are qualitatively consistent with those predicted by quantum-chemical calculations in a theoretical model of this system, and herald a new approach to chemical catalysis.
541 citations
TL;DR: In this paper, most of the significant phenomena that cause heating during microwave-material interaction and heat transfer during microwave energy absorption in materials are discussed. But, the mechanisms associated with the processing are less understood; popular mechanisms such as dipolar heating and conduction heating have been mostly explored.
Abstract: Efforts to use microwaves in material processing are gradually increasing. However, the phenomena associated with the processing are less understood; popular mechanisms such as dipolar heating and conduction heating have been mostly explored. The current paper reviews most of the significant phenomena that cause heating during microwave–material interaction and heat transfer during microwave energy absorption in materials. Mechanisms involved during interaction of microwave with characteristically different materials – metals, non-metals and composites (metal matrix composites, ceramic matrix composites and polymer matrix composites) have been discussed using suitable illustrations. It was observed that while microwave heating of metal based materials is due to the magnetic field based loss effects, dipolar loss and conduction loss are the phenomena associated with the electric field effects in microwave heating of non-metals. Challenges in processing of advanced materials, particularly composites have been identified from the available literature; further research directions with possible benefits have been highlighted.
502 citations
TL;DR: The generated C-doped Bi3 O4 Cl has a noble-metal- and electron-scavenger-free water-oxidation ability under visible light, which is difficult to achieve with most existing photocatalysts.
Abstract: Incorporating carbon into Bi3 O4 Cl enhances its internal electric field by 126 times, which induces a bulk charge separation efficiency (ηbulk ) of 80%. This ultrahigh ηbulk value presents a state-of-the-art result in tuning the bulk charge separation. The generated C-doped Bi3 O4 Cl has a noble-metal- and electron-scavenger-free water-oxidation ability under visible light, which is difficult to achieve with most existing photocatalysts.
486 citations
TL;DR: A general strategy to reconfigure active particles into various collective states by introducing imbalanced interactions is presented, and this strategy of asymmetry-driven active self-organization should generalize rationally to other active 2D and three-dimensional materials.
Abstract: Metal–dielectric Janus colloids subjected to perpendicular a.c. electric fields can self-organize into swarms, chains, clusters and isotropic gases, depending on the frequency of the field.
443 citations
TL;DR: The observation of NMR in Cd3As2 microribbons in parallel magnetic fields up to 66% at 50 K and visible at room temperatures is reported, demonstrating the chiral anomaly, a long-sought high-energy-physics effect, in solid-state systems.
Abstract: A large negative magnetoresistance (NMR) is anticipated in topological semimetals in parallel magnetic fields, demonstrating the chiral anomaly, a long-sought high-energy-physics effect, in solid-state systems. Recent experiments reveal that the Dirac semimetal Cd3As2 has the record-high mobility and positive linear magnetoresistance in perpendicular magnetic fields. However, the NMR has not yet been unveiled. Here we report the observation of NMR in Cd3As2 microribbons in parallel magnetic fields up to 66% at 50 K and visible at room temperatures. The NMR is sensitive to the angle between magnetic and electrical fields, robust against temperature and dependent on the carrier density. The large NMR results from low carrier densities in our Cd3As2 samples, ranging from 3.0 × 10(17) cm(-3) at 300 K to 2.2 × 10(16) cm(-3) below 50 K. We therefore attribute the observed NMR to the chiral anomaly. In perpendicular magnetic fields, a positive linear magnetoresistance up to 1,670% at 14 T and 2 K is also observed.
398 citations
TL;DR: A pedagogical review of various properties of the electromagnetic fields, the anomalous transport phenomena, and their experimental signatures in heavy-ion collisions is given.
Abstract: The hot and dense matter generated in heavy-ion collisions may contain domains which are not invariant under P and CP transformations. Moreover, heavy-ion collisions can generate extremely strong magnetic fields as well as electric fields. The interplay between the electromagnetic field and triangle anomaly leads to a number of macroscopic quantum phenomena in these P- and CP-odd domains known as anomalous transports. The purpose of this article is to give a pedagogical review of various properties of the electromagnetic fields, the anomalous transport phenomena, and their experimental signatures in heavy-ion collisions.
275 citations
TL;DR: By performing systematic magneto-transport studies on thin films of a predicted material candidate WTe2, this work observes notable negative longitudinal magnetoresistance, which can be attributed to the chiral anomaly in WSM and demonstrates that the Fermi energy can be in-situ tuned through the Weyl points via the electric field effect.
Abstract: The progress in exploiting new electronic materials has been a major driving force in solid-state physics. As a new state of matter, a Weyl semimetal (WSM), in particular a type-II WSM, hosts Weyl fermions as emergent quasiparticles and may harbour novel electrical transport properties. Nevertheless, such a type-II WSM material has not been experimentally observed. In this work, by performing systematic magneto-transport studies on thin films of a predicted material candidate WTe2, we observe notable negative longitudinal magnetoresistance, which can be attributed to the chiral anomaly in WSM. This phenomenon also exhibits strong planar orientation dependence with the absence along the tungsten chains, consistent with the distinctive feature of a type-II WSM. By applying a gate voltage, we demonstrate that the Fermi energy can be in-situ tuned through the Weyl points via the electric field effect. Our results may open opportunities for implementing new electronic applications, such as field-effect chiral devices.
254 citations
TL;DR: In this article, the average unit cell volume is seen to increase with increasing DC field and has been interpreted in terms of increasing levels of structural disorder in the system, where the structure becomes ferroelectric with high polarization.
Abstract: Solid-state dielectric energy storage is the most attractive and feasible way to store and release high power energy compared to chemical batteries and electrochemical super-capacitors. However, the low energy density (ca. 1 J cm−3) of commercial dielectric capacitors has limited their development. Dielectric materials showing field induced reversible phase transitions have great potential to break the energy storage density bottleneck. In this work, dense AgNbO3 ceramic samples were prepared successfully using solid state methods. Ferroelectric measurements at different temperatures reveal evidence of two kinds of polar regions. One of these is stable up to 70 °C, while the other remains stable up to 170 °C. The associated transition temperatures are supported by second harmonic generation measurements on poled samples and are correlated with the occurrence of two sharp dielectric responses. The average unit cell volume is seen to increase with increasing DC field and has been interpreted in terms of increasing levels of structural disorder in the system. At a high electric field the structure becomes ferroelectric with high polarization. This field induced transition exhibits a recoverable energy density of 2.1 J cm−3, which represents one of the highest known values for lead-free bulk ceramics.
240 citations
TL;DR: The electronic properties of monolayer MoTe2 on top of EuO(111) are studied by first-principles calculations to find out how the direction of the Hall current as well as the valley and spin polarizations can be tuned by an external magnetic field.
Abstract: The electronic properties of monolayer MoTe2 on top of EuO(111) are studied by first-principles calculations. Strong spin polarization is induced in MoTe2 , which results in a large valley polarization. In a longitudinal electric field this will result in a valley and spin-polarized charge Hall effect. The direction of the Hall current as well as the valley and spin polarizations can be tuned by an external magnetic field.
238 citations
TL;DR: Wang et al. as mentioned in this paper proposed a method to solve the problem of low-power semiconductors in the context of particle physics and showed that it is possible to achieve high energy efficiency.
Abstract: 1. SKLSM, Institute of Semiconductors, CAS, P. O. Box 912, Beijing 100083, China 2. Department of Physics, School of Sciences, Beijing Technology and Business University, Beijing 100048, China 3. School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom † These authors contributed equally to this work. * Correspondence and requests for materials should be addressed to K. W. (e-mail: kywang@semi.ac.cn).
TL;DR: This review summarizes a variety of beam damage phenomena relating to oxides in (scanning) transmission electron microscopes, and underlines the shortcomings of currently popular mechanisms.
Abstract: This review summarizes a variety of beam damage phenomena relating to oxides in (scanning) transmission electron microscopes, and underlines the shortcomings of currently popular mechanisms. These phenomena include mass loss, valence state reduction, phase decomposition, precipitation, gas bubble formation, phase transformation, amorphization and crystallization. Moreover, beam damage is also dependent on specimen thickness, specimen orientation, beam voltage, beam current density and beam size. This article incorporates all of these damage phenomena and experimental dependences into a general description, interpreted by a unified mechanism of damage by induced electric field. The induced electric field is produced by positive charges, which are generated from excitation and ionization. The distribution of the induced electric fields inside a specimen is beam-illumination- and specimen-shape- dependent, and associated with the experimental dependence of beam damage. Broadly speaking, the mechanism operates differently in two types of material. In type I, damage increases the resistivity of the irradiated materials, and is thus divergent, resulting in phase separation. In type II, damage reduces the resistivity of the irradiated materials, and is thus convergent, resulting in phase transformation. Damage by this mechanism is dependent on electron-beam current density. The two experimental thresholds are current density and irradiation time. The mechanism comes into effect when these thresholds are exceeded, below which the conventional mechanisms of knock-on and radiolysis still dominate.
TL;DR: The effective electric-field control of SOT and the giant spin-torque efficiency in Cr-doped TI may lead to the development of energy-efficient gate-controlled spin-Torque devices compatible with modern field-effect semiconductor technologies.
Abstract: Electric-field manipulation of magnetic order has proved of both fundamental and technological importance in spintronic devices. So far, electric-field control of ferromagnetism, magnetization and magnetic anisotropy has been explored in various magnetic materials, but the efficient electric-field control of spin-orbit torque (SOT) still remains elusive. Here, we report the effective electric-field control of a giant SOT in a Cr-doped topological insulator (TI) thin film using a top-gate field-effect transistor structure. The SOT strength can be modulated by a factor of four within the accessible gate voltage range, and it shows strong correlation with the spin-polarized surface current in the film. Furthermore, we demonstrate the magnetization switching by scanning gate voltage with constant current and in-plane magnetic field applied in the film. The effective electric-field control of SOT and the giant spin-torque efficiency in Cr-doped TI may lead to the development of energy-efficient gate-controlled spin-torque devices compatible with modern field-effect semiconductor technologies.
TL;DR: In this article, the stability of solitary traveling wave solutions of the modified Korteweg-de Vries-Zakharov-Kuznetsov (mKdV-ZK) equation to three-dimensional longwavelength perturbations is investigated.
Abstract: The nonlinear three-dimensional modified Korteweg–de Vries–Zakharov–Kuznetsov (mKdV–ZK) equation governs the behavior of weakly nonlinear ion-acoustic waves in magnetized electron–positron plasma which consists of equal hot and cool components of each species. By using the reductive perturbation procedure leads to a mKdV–ZK equation governing the oblique propagation of nonlinear electrostatic modes. The stability of solitary traveling wave solutions of the mKdV–ZK equation to three-dimensional long-wavelength perturbations is investigated. We found the electrostatic field potential and electric field in form traveling wave solutions for three-dimensional mKdV–ZK equation. The solutions for the mKdV–ZK equation are obtained precisely and efficiency of the method can be demonstrated.
TL;DR: The authors' measurements reveal contrasting trends in the NRET rate from the quantum dot to the van der Waals material as a function of thickness, which increases significantly with increasing layer thickness of graphene, but decreases with increasing thickness of MoS2 layers.
Abstract: We report efficient nonradiative energy transfer (NRET) from core–shell, semiconducting quantum dots to adjacent two-dimensional sheets of graphene and MoS2 of single- and few-layer thickness. We observe quenching of the photoluminescence (PL) from individual quantum dots and enhanced PL decay rates in time-resolved PL, corresponding to energy transfer rates of 1–10 ns–1. Our measurements reveal contrasting trends in the NRET rate from the quantum dot to the van der Waals material as a function of thickness. The rate increases significantly with increasing layer thickness of graphene, but decreases with increasing thickness of MoS2 layers. A classical electromagnetic theory accounts for both the trends and absolute rates observed for the NRET. The countervailing trends arise from the competition between screening and absorption of the electric field of the quantum dot dipole inside the acceptor layers. We extend our analysis to predict the type of NRET behavior for the near-field coupling of a chromophore...
TL;DR: In this article, the effect of the electric field on nanofluid viscosity is taken into account and the numerical results show that the voltage used can change the flow shape.
Abstract: Natural convection heat transfer of a nanofluid in the presence of an electric field is investigated. The control volume finite element method (CVFEM) is utilized to simulate this problem. A Fe3O4–ethylene glycol nanofluid is used as the working fluid. The effect of the electric field on nanofluid viscosity is taken into account. Numerical investigation is conducted for several values of Rayleigh number, nanoparticle volume fraction, and the voltage supplied. The numerical results show that the voltage used can change the flow shape. The Coulomb force causes the isotherms to become denser near the bottom wall. Heat transfer rises with increase in the voltage supplied and Rayleigh number. The effect of electric field on heat transfer is more pronounced at low Rayleigh numbers due to the predomination of the conduction mechanism.
TL;DR: It is demonstrated that perovskite solar cells are stable under an electric field up to the operating voltage, and Ion migration is confirmed using the temperature-dependent dark current decay.
Abstract: Perovskite solar cells have great potential for high efficiency generation but are subject to the impact of external environmental conditions such as humidity, UV and sun light, temperature, and electric fields. The long-term stability of perovskite solar cells is an important issue for their commercialization. Various studies on the stability of perovskite solar cells are currently being performed; however, the stability related to electric fields is rarely discussed. Here the electrical stability of perovskite solar cells is studied. Ion migration is confirmed using the temperature-dependent dark current decay. Changes in the power conversion efficiency according to the amount of the external bias are measured in the dark, and a significant drop is observed only at an applied voltage greater than 0.8 V. We demonstrate that perovskite solar cells are stable under an electric field up to the operating voltage.
TL;DR: In this paper, an all-metal plasmonic absorber with an absorption bandwidth less than 8 nm and polarization insensitive absorptivity exceeding 99% was proposed, which can be operated as a refractive index sensor with a sensitivity of 885 nm/RIU.
Abstract: Plasmonics offer an exciting way to mediate the interaction between light and matter, allowing strong field enhancement and confinement, large absorption and scattering at resonance. However, simultaneous realization of ultra-narrow band perfect absorption and electromagnetic field enhancement is challenging due to the intrinsic high optical losses and radiative damping in metals. Here, we propose an all-metal plasmonic absorber with an absorption bandwidth less than 8 nm and polarization insensitive absorptivity exceeding 99%. Unlike traditional Metal-Dielectric-Metal configurations, we demonstrate that the narrowband perfect absorption and field enhancement are ascribed to the vertical gap plasmonic mode in the deep subwavelength scale, which has a high quality factor of 120 and mode volume of about 10(-4) × (λres/n)(3). Based on the coupled mode theory, we verify that the diluted field enhancement is proportional to the absorption, and thus perfect absorption is critical to maximum field enhancement. In addition, the proposed perfect absorber can be operated as a refractive index sensor with a sensitivity of 885 nm/RIU and figure of merit as high as 110. It provides a new design strategy for narrow band perfect absorption and local field enhancement, and has potential applications in biosensors, filters and nonlinear optics.
TL;DR: A toroidal dipole in metasurfaces provides an alternate approach for the excitation of high-Q resonances by exploiting tightly confined loops of oscillating magnetic field that curl around the fictitious arrow of the toroid dipole vector.
Abstract: A toroidal dipole in metasurfaces provides an alternate approach for the excitation of high-Q resonances. In contrast to conventional multipoles, the toroidal dipole interaction strength depends on the time derivative of the surrounding electric field. A characteristic feature of toroidal dipoles is tightly confined loops of oscillating magnetic field that curl around the fictitious arrow of the toroidal dipole vector.
TL;DR: In this paper, an electric field effect on nanofluid forced convective heat transfer in an enclosure with sinusoidal wall is presented, where the Control Volume based Finite Element Method (CVFEM) is utilized to simulate this problem.
TL;DR: In this paper, the phase diagram of lead-free BaHf x Ti 1−x O 3 (BHT) ferroelectric ceramics was established, and the electrocaloric efficiency (ΔT/ΔE ǫ = 0.35°C under 10kV/cm) was reported.
TL;DR: It is shown that oxidation and reduction of organometallic compounds containing either Fe, Ru or Mo centres can solely be triggered by the electric field applied to a two-terminal molecular junction, triggering a transient charging effect in the entire molecule with a strong hysteresis and large high-to-low current ratios.
Abstract: Charge transport through single molecules can be influenced by the charge and spin states of redox-active metal centres placed in the transport pathway. These intrinsic properties are usually manipulated by varying the molecule's electrochemical and magnetic environment, a procedure that requires complex setups with multiple terminals. Here we show that oxidation and reduction of organometallic compounds containing either Fe, Ru or Mo centres can solely be triggered by the electric field applied to a two-terminal molecular junction. Whereas all compounds exhibit bias-dependent hysteresis, the Mo-containing compound additionally shows an abrupt voltage-induced conductance switching, yielding high-to-low current ratios exceeding 1,000 at bias voltages of less than 1.0 V. Density functional theory calculations identify a localized, redox-active molecular orbital that is weakly coupled to the electrodes and closely aligned with the Fermi energy of the leads because of the spin-polarized ground state unique to the Mo centre. This situation provides an additional slow and incoherent hopping channel for transport, triggering a transient charging effect in the entire molecule with a strong hysteresis and large high-to-low current ratios.
TL;DR: In this paper, the breakdown characteristics of Fluoronitriles CO2 gas mixtures in different experimental conditions were investigated, and it was shown that 3.7 % Fluorinitristantriles / 96.3% CO2 mixture constitutes a good compromise and an appropriate gas mixture for high voltage apparatus insulation in point of view of pressure and low ambient temperature application (-30°C).
Abstract: This paper is aimed at the breakdown characteristics of Fluoronitriles – CO2 gas mixtures in different experimental conditions; these mixtures constitute promising substitutes to SF6 gas in high voltage applications especially gas insulating switchgear (GIS). Fluoronitriles chemical gas compound based on 3M NOVEC 4710 have a high dielectric strength, more than 2 times that of SF6 and a low Global Warming Potential (GWP). Mixed with CO2 as gas carrier, the obtained mixtures offer interesting dielectric properties and the possibility to be used for low temperature applications. The experiments are conducted with different electrodes geometries namely plane-to-plane, sphere-to-sphere, sphere-to-plane and rod-to-plane (i.e. in homogeneous, quasi-homogeneous and inhomogeneous electric field distribution) and different field utilization factors, under AC and lightning impulse voltages. The same experiments are reproduced for pure SF6 for the comparison. The comparison of breakdown voltages results of mixtures with different concentrations of Fluoronitriles in CO2 in sphere-to-sphere electrodes arrangement shows that the 3.7 % Fluoronitriles / 96.3% CO2 mixture constitutes a good compromise and an appropriate gas mixture for high voltage apparatus insulation in point of view of pressure and low ambient temperature application (-30°C).
Helmholtz-Zentrum Dresden-Rossendorf1, Savitribai Phule Pune University2, European XFEL3, Dresden University of Technology4, Free University of Berlin5, Karlsruhe Institute of Technology6, University of Groningen7, Max Planck Society8, University of Stuttgart9, Eötvös Loránd University10, Helmholtz-Zentrum Berlin11, Fritz Haber Institute of the Max Planck Society12, Gwangju Institute of Science and Technology13, German National Metrology Institute14, SLAC National Accelerator Laboratory15
TL;DR: This work presents a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that will revolutionize experiments in this field and demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude.
Abstract: Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution.
Abstract: Polymer nanocomposite dielectrics are of critical importance for a number of electrical and electronic applications. It is highly desirable to achieve high energy density at a low electric field. In this contribution, PVDF-based (or PVDF–TrFE–CFE based) nanocomposite films filled with BaTiO3@TiO2 nanofibers are cast from solutions. Topological-structure modulated polymer nanocomposites are assembled layer-by-layer with the as-cast films via a hot-pressing process. Modulation of the topological-structure induces substantial redistribution of the local electric field among the constituent layers, giving rise to enhanced electric polarization at a low electric field and increased breakdown strength. These synergistic effects lead to an ultrahigh energy density of ∼12.5 J cm−3 and a high discharge efficiency of ∼70% at 350 kV mm−1. High energy density at a low electric field is thus achieved by modulating the topological structure of polymer dielectric nanocomposites, which is of critical significance to make dielectric nanocomposites viable energy storage devices.
TL;DR: In this paper, a combined 2D numerical and experimental study of the influence of N 2 admixture on the dynamics of a He-N 2 discharge in the 10 cm long dielectric tube of a plasma gun setup is carried out.
Abstract: This paper presents a combined 2D numerical and experimental study of the influence of N 2 admixture on the dynamics of a He–N 2 discharge in the 10 cm long dielectric tube of a plasma gun setup. First, the comparison between experiments and simulations is carried out on the ionization front propagation velocity in the tube. The importance of taking into account a detailed kinetic scheme for the He–N 2 mixture in the simulations to obtain a good agreement with the experiments is put forward. For the μs driven plasma gun, the two-and three-body Penning reactions occurring in the plasma column behind the ionization front, are shown to play a key role on the discharge dynamics. In the experiments and simulations, the significant influence of the amplitude of the applied voltage on the ionization front propagation velocity is observed. As the amount of N 2 varies, simulation results show that the ionization front velocity, depends on a complex coupling between the kinetics of the discharge, the photoionization and the 2D structure of the discharge in the tube. Finally, the time evolution of axial and radial components of the electric field measured by an electro-optic probe set outside the tube are compared with simulation results. A good agreement is obtained on both components of the electric field. In the tube, simulations show that the magnitude of the axial electric field on the discharge axis depends weakly on the amount of N 2 conversely to the magnitude of the off-axis peak electric field. Both, simulations and first measurements in the tube or within the plasma plume show peak electric fields of the order of 45 kV·cm −1 .
TL;DR: In this paper, surface traps with different trap levels are introduced by different surface modification methods which include dielectric barrier discharges plasma, direct fluorination, and Cr2O3 coating.
Abstract: To investigate the role surface traps play in the charge injection and transfer behavior of alumina-filled epoxy composites, surface traps with different trap levels are introduced by different surface modification methods which include dielectric barrier discharges plasma, direct fluorination, and Cr2O3 coating. The resulting surface physicochemical characteristics of experimental samples were observed using atomic force microscopy, scanning electron microscopy and fourier transform infrared spectroscopy. The surface potential under dc voltage was detected and the trap level distribution was measured. The results suggest that the surface morphology of the experimental samples differs dramatically after treatment with different surface modification methods. Different surface trap distributions directly determine the charge injection and transfer property along the surface. Shallow traps with trap level of 1.03–1.11 eV and 1.06–1.13 eV introduced by plasma and fluorination modifications are conducive for charge transport along the insulating surface, and the surface potential can be modified, producing a smoother potential curve. The Cr2O3 coating can introduce a large number of deep traps with energy levels ranging from 1.09 to 1.15 eV. These can prevent charge injection through the reversed electric field formed by intensive trapped charges in the Cr2O3 coatings.
TL;DR: An electric field tuning of the thermopower in ultrathin WSe2 single crystals over a wide range of carrier concentration by using electric double-layer (EDL) technique is reported.
Abstract: We report an electric field tuning of the thermopower in ultrathin WSe2 single crystals over a wide range of carrier concentration by using electric double-layer (EDL) technique. We succeeded in the optimization of power factor not only in the hole but also in the electron side, which has never been chemically accessed. The maximized values of power factor are one-order larger than that obtained by changing chemical composition, reflecting the clean nature of electrostatic doping.
TL;DR: In this paper, a core-shell structured barium titanate-titanium dioxide nanofiber (BTO@TO-nf) was designed based on interfacial engineering and prepared using coaxial electrospinning to increase the electric displacement in high breakdown strength nanocomposites with low loading nanofillers.
Abstract: High energy density polymer nanocomposites are quite promising for film capacitors and many other electronic devices. In this study, the promising strategy is to increase the electric displacement in high breakdown strength nanocomposites with low loading nanofillers. The core–shell structured barium titanate@titanium dioxide nanofiber (BTO@TO-nf) reported herein is designed based on interfacial engineering and prepared using coaxial electrospinning. In the PVDF nanocomposites containing the core–shell nanofibers, the dielectric permittivity as well as the electric displacement increase significantly, due to the additional polarization induced by the charge shifting in the interfacial zone between BTO on the inside and TO on the outside, which contributes significantly to the electric displacement. In addition, the breakdown strength of the nanocomposite is maintained through the charge shifting being limited to the interfacial zone so it cannot form a percolation path in the matrix. A large discharged energy density of ca. 10.94 J cm−3 is achieved at a field of 360 kV mm−1 for the nanocomposite film with 3% volume fraction of BTO@TO-nf, which is higher than those of the referenced PVDF nanocomposites under the same electric field. The present study demonstrates the advantages of the core–shell structured nanofibers in improving the dielectric properties and provides a new way to enhance the energy density of polymer nanocomposites.
TL;DR: In this article, a careful review of the literature is combined with the development of new methods to treat experimental APT data, the modelling of ion trajectories, and the application of density functional theory (DFT) simulations to derive molecular ion energetics.
Abstract: The cold emission of particles from surfaces under intense electric fields is a process which underpins a variety of applications including atom probe tomography (APT), an analytical microscopy technique with near-atomic spatial resolution. Increasingly relying on fast laser pulsing to trigger the emission, APT experiments often incorporate the detection of molecular ions emitted from the specimen, in particular from covalently or ionically bonded materials. Notably, it has been proposed that neutral molecules can also be emitted during this process. However, this remains a contentious issue. To investigate the validity of this hypothesis, a careful review of the literature is combined with the development of new methods to treat experimental APT data, the modelling of ion trajectories, and the application of density-functional theory (DFT) simulations to derive molecular ion energetics. It is shown that the direct thermal emission of neutral molecules is extremely unlikely. However, neutrals can still be formed in the course of an APT experiment by dissociation of metastable molecular ions.