Direction Of External Electric Field Research Articles

Influence of external electric field on molecular microscopic descriptors of non-polar insulating gases

Molecular microscopic descriptors without external electric field are commonly used for the prediction of insulating strength in gaseous medium. However, insulating gases are subjected to external electric field in electrical equipment, and the molecular microscopic descriptors are affected. Therefore, it is necessary to investigate the influence of external electric field on molecular microscopic descriptors. The Gaussian 16 software is employed to calculate the global parameter with the M06-2X functional and the 6–311++G (d, p) basis set. The wavefunction analysis software Multiwfn is used to obtain electrostatic potential parameter. In this paper, three directions of external electric field with magnitude ranging from 0 to 0.03 a.u. have been set to 10 non-polar insulating gas molecules. According to the type of molecular point group, the effect of direction and magnitude of external electric field on the molecular microscopic descriptors has been analyzed. The results indicate that the molecular microscopic descriptors are affected by the direction and magnitude of external electric field. The change rate of microscopic descriptors increases with the increase of external electric field magnitude. And the influence of the direction of external electric field is associated with the molecular symmetry. In conclusion, the effect of direction and magnitude of external electric field is needed to be considered when analyzing the effect of external electric field on molecular microscopic descriptors.

Polarization properties of E-FISH signals and optimization of simultaneous measurement of electric field vectors

Electric field measurements based on the electric field induced second harmonic (E-FISH) method have been employed in a wide range of studies. Most studies typically measure two components of the electric field separately. Although there have been proposals for the simultaneous measurement of electric field vectors, the imbalance of the two corresponding E-FISH signals has limited its application. Furthermore, the relationship between the polarization of the E-FISH signal and the direction of external electric field remains unclear. In this paper, the general expressions for the polarization and power of both components of E-FISH signals are derived, assuming arbitrary probe beam polarization and external electric field direction. The theoretical results indicate that the polarization of E-FISH signals varies along the interaction length. The final signal’s polarization is elliptically polarized for arbitrary electric field distribution and is correlated with the polarization of the probe beam, which deviates from what is commonly assumed to be consistent with the external electric field. If the polarization of the probe beam is not parallel to the axes, the power of each signal component is determined by both components of the external electric field, which lays the foundation for the simultaneous measurement of electric field vectors. This theoretical prediction is subsequently validated by experimental results. Finally, the power maps suggest that the optimal polarization angle of the probe beam is 45° or 135° to achieve a balanced signal power when measuring an unknown electric field vector. Both components of the electric field can be simultaneously obtained according to the theoretical relationship.

How Do Adsorbent Orientation and Direction of External Electric Field Affect the Charge-Transfer Surface-Enhanced Raman Spectra?

Surface-enhanced Raman spectroscopy is a highly sensitive phenomenon and a powerful fingerprint detection tool that reflects the small changes in polarizability on the pattern and intensity of Rama...

Synergistic Effects of External Electric Field and Solvent Vapor Annealing with Different Polarities to Enhance β-Phase and Carrier Mobility of the Poly(9,9-dioctylfluorene) Films

In this work, the synergistic effects of external electric field(EEF) and solvent vapor annealing to enhance β-phase and carrier mobility of poly(9,9-dioctylfluorene)(PFO) films were investigated. It is found that EEF can promote the PFO β-phase conformation transition and orientate the PFO chains along the EEF direction with the assistance of polar solvent vapor annealing. PFO chain orderness is closely related to the solvent polarity. In particular, the β-phase content in the annealed film of strong polar chloroform vapor increases from 18.7% to 34.9% after EEF treatment. Meanwhile a characteristic needle-like crystal is formed in the film, as a result, the hole mobility is enhanced by an order of magnitude. The mechanism can be attributed to the fast polarization of solvent dipole under the action of EEF, thus forming a driving force that greatly facilitates the orientation of PFO dipole unit. Research also reveals that EEF driving of the PFO chains does not occur with an insoluble solvent vapor since the solvent molecules cannot swell the film, thus there is insufficient free volume for PFO chains to adjust their conformation. This research enriches the understanding of the relationship between solvent vapor annealing and EEF in orientation polymers, and this method is simple and controlled, and capable of integrating into large-area thin film process, which provides new insights to manufacture low-cost and highly ordered polymer films, and is of great significance to enhance carrier mobility and efficiency of photoelectric devices based on polymer condensed matter physics.

Effect of External Electric Field on Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(bithiophene)] Chain Orderness, Morphology, and Carrier Mobility in Different Condensation Processes

Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(bithiophene)] (F8T2) is a kind of crystal and liquid-crystal conjugated polymer (CP). In this research, the effect of external electric field (EEF) on F8T2 chain orderness, morphology, and carrier mobility in different condensation processes of annealing at 130 °C (above glass-transition temperature), 200 °C (crystallization temperature), and 280 °C (liquid-crystal temperature) was investigated by UV–vis absorption spectroscopy, photoluminescence spectroscopy, X-ray diffraction, atomic force microscopy, polarizing optical microscopy, transmission electron microscopy (TEM), and current density–voltage (C–V) curves. It was found that EEF could enhance F8T2 chain orderness and manipulate F8T2 chain self-assembly in all the above three types of annealed films. However, the responses of F8T2 chains to EEF were different. After applying EEF, a preferred arrangement along the EEF direction with needle-like crystals was presented in 130 °C annealed films, and ordered n...

Stimulating intra- and intermolecular charge transfer and nonlinear optical response for biphenalenyl biradicaloid dimer under an external electric field.

An interesting biphenalenyl biradicaloid (IDPL) dimer consisting of both-middle superimposed phenalenyls and both-end nonsuperimposed phenalenyls has been synthesized, and has attracted intensive research interest due to its intra- and intermolecular interactions and semiconductive characteristics. It is significant that under regulation of the external electric field the directional charge transfer (CT) can produce attractive properties. In the present work, the structure and electronic properties of the IDPL dimer under an external electric field (along the horizontal Fx or the vertical Fz directions) are explored, and the following properties determined: (i) as the horizontal Fx increases, the intramolecular CT becomes larger, which induces the intermolecular CT of the IDPL dimer. (ii) In contrast, as the vertical Fz increases, the large intermolecular CT gives rise to the intramolecular CT of the IDPL dimer. (iii) More importantly, the external electric field effectively regulates and controls the first hyperpolarizability (βtot) of the IDPL dimer. Compared with the vertical Fz, the horizontal Fx induces a larger first hyperpolarizability (βtot = 5.48 × 105 a.u.). Furthermore, the application of a uniform external electric field (Fx,y,z) to the IDPL dimer was investigated to define the external electric field direction of the material application. The βtot values were increased with increasing of the uniform Fx,y,z. Our study provides an effective strategy for developing high-performance NLO materials by tuning the external electric field, and could be of significance for application in switch devices.

New Ferroelectric Phase in Atomic-Thick Phosphorene Nanoribbons: Existence of in-Plane Electric Polarization

Ferroelectrics have many significant applications in electric devices, such as capacitor or random-access memory, tuning the efficiency of solar cell. Although atomic-thick ferroelectrics are the necessary components for high-density electric devices or nanoscale devices, the development of such materials still faces a big challenge because of the limitation of intrinsic mechanism. Here, we reported that in-plane atomic-thick ferroelectricity can be induced by vertical electric field in phosphorene nanoribbons (PNRs). Through symmetry arguments, we predicted that ferroelectric direction is perpendicular to the direction of external electric field and lies in the plane. Further confirmed by the comprehensive first-principles calculations, we showed that such ferroelectricity is induced by the electron-polarization, which is different from the structural distortion in traditional ferroelectrics and the recent experimental discovery of in-plane atomic-thick ferroelectrics (Science 2016, 353, 274). Moreover, we found that the value of electronic polarization in bilayer is much larger than that in monolayer. Our results show that electron-polarization ferroelectricity maybe the most promising candidate for atomic-thick ferroelectrics.

Effects of the Interlayer Interaction and Electric Field on the Band Gap of Polar Bilayers: A Case Study of Sc2CO2

The two-dimensional Sc2CO2 monolayer has net dipole moments as compared with other functional transition metal carbides. This unique feature may provide potential routes to tune its electronic properties. Herein, the band gap engineering of Sc2CO2 bilayers is investigated by the density functional calculation. We found that the band gap of Sc2CO2 bilayers is not only dependent on the relative stacking position and distance but also on the magnitude and direction of external electric field. The competition between the interlayer van der Waals and electrostatic interactions has been revealed as the dominant mechanism for the band gap modulation of polar bilayers. This works demonstrate that polar bilayers exhibit richer electronic properties than the nonpolar one. The interlayer electric field may be utilized to fabricate novel electronic and optoelectronic devices.

Molecular structure and properties of sulfur dioxide under the external electric field

SO2 is not only an important resource but also a notorious air pollutant, so it has attracted increasing attention nowadays. This paper focuses on the influence of external electric field on SO2. In order to obtain more reliable results, the density functional theory B3P86 method is chosen to calculate the values mentioned below. The ground states of SO2 molecule under different strong electric fields ranging from -0.04 a.u. to 0.04 a.u. are optimized by density functional theory B3P86 method with 6-311++g(3d,p) basis sets. The geometric parameters, charge distributions, total energies, dipole moments, the highest occupied molecular orbital (HOMO) energies, the lowest unoccupied molecular orbital (LUMO) energies, energy gaps of SO2 under different external electric fields are obtained, respectively. On the basis of optimized configuration, the excitation energy, transition wavelength and oscillator strength in the same intense external electric field are calculated by the time dependent density functional theory (TD-B3P86) method.#br#The calculated values for geometric parameters of SO2 without external electric field agree well with the available experimental data and other theoretical results. The geometric parameters and charge distribution of SO2 strongly depend on the intensity and direction of external electric field. The total energy of SO2 in the considered range of external electric field first increases and then decreases. On the contrary, the dipole moments of SO2 in different external electric fields ranging from -0.04 a.u. to 0.04 a.u. first decrease and then increase. When the external electric field is -0.04 a.u., the total energy and symmetry of SO2 both reach the maximum values. With the change of external electric field, the LUMO energy first increases and then decreases. The HOMO energy is found to decrease through the variation of the external field. The energy gaps of SO2 are proved to first increase, and then decrease with the variation of external electric field. Through studying the energy gaps of SO2, it is found that the external electric field can affect the chemical reactivity of SO2. The excitation energies, transition wavelengths and oscillator strengths are very complicated with the change of the external electric field. The excitation properties of SO2 molecule are seriously affected by the external electric field.

Bipolar Janus particle assembly in microdevice.

In recent years, there are significant interests in the manipulation of bipolar Janus particles. In this article, we investigate the transient behavior of the electro-orientation process and particle-particle interaction of ellipsoidal bipolar Janus particles in the presence and absence of a DC electric field. The bipolar particle dynamics is modeled with a body force term in the fluid flow equations based on the Maxwell stress tensor. This force is due to presence of bipolar surface charges on the particles as well as their interactions with an imposed field. An interface resolved numerical scheme that consider the finite size of the particle is adopted for computation of the electric and flow fields. Our numerical results show that in the absence of an electric field, particles can undergo self-orientation to reach an equilibrium position. The time taken to reach a stable orientation depends on the initial configuration and inter-particle separation distance. Bipolar particles experience forces only on their polar ends, a phenomena that is difficult to capture with noninterface resolved methods. When bipolar particles are exposed to an external electric field, they rotate to align along the external electric field direction. Depending upon the initial configuration, particles orient via clockwise or counter clockwise rotations to form head to tail chains. The time required to form particle assembly strongly depends on particle size and bipolar charge density. The present numerical algorithm can be applied to a wider class of dual-faced Janus particles.

Multilayer La-modified PbTiO3 capacitors via RF magnetron sputtering

In this study, multilayer ceramics (MLCs) composed of La-modified PbTiO3 layers with internal Pt electrodes were fabricated by radio frequency (RF) magnetron sputtering. Multiple (Pb0.9,La0.1)Ti0.975O3 (PLT) layers with thicknesses of approximately 500 nm were deposited on Pt/Ti-coated Si substrates through a square movable shadow mask. The isolated internal Pt electrodes were prepared by sliding the movable shadow mask. The MLCs composed of one, three, and five PLT layers were fabricated by alternate sputtering deposition of Pt electrodes and PLT ferroelectric layers with the movable shadow mask. The MLCs had a smooth and crack-free surface, and dense PLT layers could be prepared between the internal Pt electrodes. The MLCs exhibited excellent dielectric properties and their capacitances increased with the number of PLT layers, while the dielectric losses were lower than 3.5 %. The P–E hysteresis loops of MLCs showed symmetric loops because of the alternating direction of external electric field on the ferroelectric PLT layers.

Analysis of Electric Field Distribution in Capacitors’ Dielectric with Cavities

Cavities in dielectric greatly impair the performance of capacitors, especially the life and so further affect the primary power systems in fusion energy systems. Thus, the electric field distribution in dielectric of capacitors with cavities was studied. A simplified elliptical cavity model in dielectric was built in this paper and finite element analysis was utilized to solve the electric field distribution problem. Simulation results show that the electric field near the cavities will be enhanced with a factor of k. The enhance factor k will rise with the increase of the relative permittivity of capacitors’ dielectric. The influence of the cavities’ shape on enhancement mainly results from the curvature. When the cavities possess higher curvature, the enhancement will be strengthen. Also, the orientation of the cavities affects the electric field significantly. The enhance factor k decreases with the decreasing of the angle between the major axis of ellipse and the external electric field direction.

Effect of Internal Electric Field in Well Layer of InGaN/GaN Multiple Quantum Well Light-Emitting Diodes on Efficiency Droop

We investigate the effect of internal electric field in InGaN well layer of InGaN/GaN multiple quantum well light-emitting diodes (LEDs) on efficiency droop behavior. The simulation results show that the internal electric field in InGaN well layers of Ga-polar LEDs is same as the direction of external electric field by forward bias voltage, resulting in a strong efficiency droop. However, N-polar LEDs show that the efficiency droop is drastically improved due to an increase of internal quantum efficiency and carrier injection efficiency by weakening the internal electric field with increasing the forward bias voltage and decrease of electron overflow.

Orientation-dependent electromagnetic properties of basalt fibre/nickel core–shell heterostructures

The influence of orientation on electromagnetic properties of basalt fibre/nickel core–shell heterostructures prepared by a simple electroless plating method is investigated. For comparison, the same investigation is also performed on naked basalt fibres. For electromagnetic measurement, the directions of basalt fibre/nickel and naked basalt fibres are parallel, random and perpendicular to the direction of external electric field, termed E|| sample, random sample and E⊥ sample, respectively. Electromagnetic anisotropy can be clearly observed in the basalt fibre/nickel core–shell heterostructures, while electromagnetic properties of naked basalt fibres are unrelated to the orientation. The E⊥ basalt fibre/nickel shows the highest dielectric loss but the lowest magnetic loss, and E|| basalt fibre/nickel exhibits the highest magnetic loss but the lowest dielectric loss. The dielectric loss of E⊥ basalt fibre/nickel is several times as large as that of E|| basalt fibre/nickel, which could be attributed to the increase of polarization relaxation time as a consequence of the nanosize-confinement effect. The magnetic loss of E|| basalt fibre/nickel is even one order of magnitude higher than that of E⊥ basalt fibre/nickel, which originates mainly from the natural magnetic resonance of basalt fibre/nickel core–shell heterostructures.

Model of hopping dc conductivity via nearest neighbor boron atoms in moderately compensated diamond crystals

Expressions for dependences of the pre-exponential factor σ 3 and the thermal activation energy ε 3 of hopping electric conductivity of holes via boron atoms on the boron atom concentration N and the compensation ratio K are obtained in the quasiclassical approximation. It is assumed that the acceptors (boron atoms) in charge states (0) and (−1) and the donors that compensate them in the charge state ( + 1 ) form a nonstoichiometric simple cubic lattice with translational period R h = [ ( 1 + K ) N ] − 1 / 3 within the crystalline matrix. A hopping event occurs only over the distance R h at a thermally activated accidental coincidence of the acceptor levels in charge states (0) and (−1). Donors block the fraction K / ( 1 − K ) of impurity lattice sites. The hole hopping conductivity is averaged over all possible orientations of the lattice with respect to the external electric field direction. It is supposed that an acceptor band is formed by Gaussian fluctuations of the potential energy of boron atoms in charge state (−1) due to Coulomb interaction only between the ions at distance R h . The shift of the acceptor band towards the top of the valence band with increasing N due to screening (in the Debye–Hückel approximation) of the impurity ions by holes hopping via acceptor states was taken into account. The calculated values of σ 3 ( N ) and ε 3 ( N ) for K ≈ 0.25 agree well with known experimental data at the insulator side of the insulator–metal phase transition. The calculation is carried out at a temperature two times lower than the transition temperature from hole transport in v -band of diamond to hopping conductance via boron atoms.

Electrokinetic Transport in Microchannels with Random Roughness

We present a numerical framework to model the electrokinetic transport in microchannels with random roughness. The three-dimensional microstructure of the rough channel is generated by a random generation-growth method with three statistical parameters to control the number density, the total volume fraction, and the anisotropy characteristics of roughness elements. The governing equations for the electrokinetic transport are solved by a high-efficiency lattice Poisson-Boltzmann method in complex geometries. The effects from the geometric characteristics of roughness on the electrokinetic transport in microchannels are therefore modeled and analyzed. For a given total roughness volume fraction, a higher number density leads to a lower fluctuation because of the random factors. The electroosmotic flow rate increases with the roughness number density nearly logarithmically for a given volume fraction of roughness but decreases with the volume fraction for a given roughness number density. When both the volume fraction and the number density of roughness are given, the electroosmotic flow rate is enhanced by the increase of the characteristic length along the external electric field direction but is reduced by that in the direction across the channel. For a given microstructure of the rough microchannel, the electroosmotic flow rate decreases with the Debye length. It is found that the shape resistance of roughness is responsible for the flow rate reduction in the rough channel compared to the smooth channel even for very thin double layers, and hence plays an important role in microchannel electroosmotic flows.

Mechanism of Carbon Nanotubes Aligning along Applied Electric Field

The mechanism of single-walled carbon nanotubes (SWCNTs) aligning in the direction of external electric field is studied by quantum mechanics calculations. The rotational torque on the carbon nanotubes is proportional to the difference between the longitudinal and transverse polarizabilities and varies with the angle of SWCNTs to the external electric field. The longitudinal polarizability increases with second power of length, while the transverse polarizability increases linearly with length. A zigzag SWCNT has larger longitudinal and transverse polarizabilities than an armchair SWCNT with the same diameter and the discrepancy becomes larger for longer tubes.

Electric-field measurement near a ring antenna by a new field sensor using piezoelectric resonance

It is demonstrated that the pulse spectroscopy in combination with piezoelectric resonance makes an ideal nondisturbing tool for the measurement of electric field near an antenna. The dependence of the picked up resonance signal on the amplitude and direction of external electric field was quantitatively evaluated. This new field sensing technique was used to investigate the field of a ring antenna the near field of which is widely used.

THE EFFECT OF ELECTRIC FIELD DIRECTION ON THE-SHEAR STRESS OF ER FLUIDS

The effect of the direction of external electric field on the shear stress of an ER fluid has been studied by molecular-dynamics simulation. Due to the formation of inclined chains, the shear stress strongly depends on the direction of the field, and it may be very large under some special field direction. And theoretical model of ideal microstructure of ER fluids has proved this result. Thus the ER effect may be greatly enhanced just by choosing an optimum direction for the field without any additional requirement, suggesting a promising way to the practical application of ER fluids.

Observation of the electric-field-inducedE1 transition between 5s4d 1 D 2 and 5s 2 1 S 0 levels in Sr I

The angular distribution of the electric-field-inducedE1 radiation is asymmetric with respect to the external electric field direction. Measurement of this asymmetry for the 5s4d1D2 → 5s21S0 transition in strontium permits the experimental determination of the 5s5p1P1 → 5s4d1D2 decay rate. The result is:A(1P1 →1D2)=(4.37±0.93±0.66) × 103s−1.