Electric Fields Of Order Research Articles

Ultrafast single electron spin manipulation in 2D semiconductor quantum dots with optimally controlled time-dependent electric fields through spin-orbit coupling

We have studied theoretically the possibility of ultra-fast manipulation of a single electron spin in 2D semiconductor quantum dots, by means of high-frequency time-dependent electric fields. The electron spin degree of freedom is excited through spin-orbit coupling, and the procedure may be enhanced by the presence of a static magnetic field. We use quantum optimal control theory to tailor the temporal profile of the electric field in order to achieve the most effective manipulation. The scheme predicts significant control over spin operations in times of the order of picoseconds – an ultrafast time scale that permits to avoid the effects of decoherence if this scheme is to be used as a tool for quantum information processing.

Integral Equation Analysis of EM Scattering from Multilayered Metallic Photonic Crystal Accelerated with Adaptive Cross Approximation

A space-domain integral equation method accelerated with adaptive cross approximation (ACA) is presented for the fast and accurate analysis of electromagnetic (EM) scattering from multilayered metallic photonic crystal (MPC). The method directly solves for the electric field in order to easily enable the periodic boundary condition (PBC) in the spatial domain. The ACA is a purely algebraic method allowing the compression of fully populated matrices; hence, its formulation and implementation are independent of integral equation kernel (Green’s function). Therefore, the ACA is very well suited for accelerating integral equation analysis of periodic structure with the integral kernel of the periodic Green’s function (PGF). The computation of the spatial-domain periodic Green’s function (PGF) is accelerated by the modified Ewald transformation, such that the multilayered periodic structure can be analyzed efficiently and accurately. An effective interpolation method is also proposed to fast compute the periodic Green’s function, which can greatly reduce the time of matrix filling. Numerical examples show that the proposed method can greatly save the frequency sweep time for multilayered periodic structure.

Hyperfine Stark effect of shallow donors in silicon

We present a complete theoretical treatment of Stark effects in doped silicon, whose predictions are supported by experimental measurements. A multi-valley effective mass theory, dealing non-perturbatively with valley-orbit interactions induced by a donor-dependent central cell potential, allows us to obtain a very reliable picture of the donor wave function within a relatively simple framework. Variational optimization of the 1s donor binding energies calculated with a new trial wave function, in a pseudopotential with two fitting parameters, allows an accurate match of the experimentally determined donor energy levels, while the correct limiting behavior for the electronic density, both close to and far from each impurity nucleus, is captured by fitting the measured contact hyperfine coupling between the donor nuclear and electron spin. We go on to include an external uniform electric field in order to model Stark physics: With no extra ad hoc parameters, variational minimization of the complete donor ground energy allows a quantitative description of the field-induced reduction of electronic density at each impurity nucleus. Detailed comparisons with experimental values for the shifts of the contact hyperfine coupling reveal very close agreement for all the donors measured (P, As, Sb and Bi). Finally, we estimate field ionization thresholds for the donor ground states, thus setting upper limits to the gate manipulation times for single qubit operations in Kane-like architectures: the Si:Bi system is shown to allow for A gates as fast as around 10 MHz.

Self-sustained pulsations in a quantum-dot laser.

We analyze a delay differential equation for the amplitude of the electrical field in order to understand recent experimental observations of low-frequency oscillations in a QD laser. The laser contains no saturable absorber section and exhibits no relaxation oscillations. We investigate the problem both analytically and numerically. We show that there exists a homoclinic bifurcation from a cavity mode that is responsible for the generation of low-frequency pulsating oscillations. We discuss the role of optothermal effects in the formation of the pulsed dynamics.

Effect of Joule heating on isoelectric focusing of proteins in a microchannel.

Electric field-driven separation and purification techniques, such as isoelectric focusing (IEF) and isotachophoresis, generate heat in the system that can affect the performance of the separation process. In this study, a new mathematical model is presented for IEF that considers the temperature rise due to Joule heating. We used the model to study focusing phenomena and separation performance in a microchannel. A finite volume-based numerical technique is developed to study temperature-dependent IEF. Numerical simulation for narrow range IEF (6 < pH < 10) is performed in a straight microchannel for 100 ampholytes and two model proteins: staphylococcal nuclease and pancreatic ribonuclease. Separation results of the two proteins are obtained with and without considering the temperature rise due to Joule heating in the system for a nominal electric field of 100 V/cm. For the no Joule heating case, constant properties are used, while for the Joule heating case, temperature-dependent titration curves and thermo-physical properties are used. Our numerical results show that the temperature change due to Joule heating has a significant impact on the final focusing points of proteins, which can lower the separation performance considerably. In the absence of advection and any active cooling mechanism, the temperature increase is the highest at the mid-section of a microchannel. We also found that the maximum temperature in the system is a strong function of the [Formula: see text] value of the carrier ampholytes. Simulation results are also obtained for different values of applied electric fields in order to find the optimum working range considering the simulation time and buffer temperature. Moreover, the model is extended to study IEF in a straight microchip where pH is formed by supplying H(+) and OH(-), and the thermal analysis shows that the heat generation is negligible in ion supplied IEF.

분극 전계에 따른 압전 페인트 센서 감도 측정

ABSTRACT: In this study, the experimental study has been performed by varying the polarization of the electric fieldand impact force to check the piezoelectric characteristics of piezoelectric paint sensor. Piezoelectric paint sensor usedin this study is composed of epoxy resin with a hardener and PNN-PZT powder in 1:1 weight ratio. The dimensionsof the paint sensor specimen are 40 × 40 × 1 mm 3 and regular specimens were made using a mold. The voids areremoved from the specimen in the vacuum desiccator. Both upper side and bottom side of the paint sensor werecoated with silver paste for making an electrode and then dried at room temperature for a day. The poling treatmenthas been carried out under controlled conditions of the electric field in order to check the effect of piezoelectricsensitivities, while the poling temperature was fixed at room temperature and the poling time was set to 30 min. Thepiezoelectric sensitivities have been measured by comparing output voltage from paint sensor with output force fromimpact hammer when the impact hammer hits the paint sensor. In result, the effect of the electric field has beenevaluated for the sensitivity and describe the result.초록

Phenomenological characterization of fabrication of aligned pristine-SWNT and COOH-SWNT nanocomposites via dielectrophoresis under AC electric field

Dielectrophoresis under the application of AC electric fields is one of the primary fabrication techniques (DEPFT) for obtaining aligned carbon nanotube (CNT)–polymer nanocomposites, and is used here to generate data sets from which DEPFT fabrication models in terms of CNT dispersion and orientation distribution can be developed. While the general understanding of how CNTs form aligned filaments under the influence of dielectrophoretic forces and moments is well established, detailed multi-CNT-filament formation predictions of microstructure evolution from a random dispersion into a more ordered structure remain intractable. As such, effort here is focused towards the development of phenomenological fabrication models for controlling local CNT dispersion and orientation as a function of applied electric field magnitude, frequency, and exposure time. In this study, 0.03 wt% single-wall nanotubes (SWNTs) and acid treated functionalized SWNTs (COOH-SWNTs) were dispersed in a photopolymerizable monomer blend (urethane dimethacrylate (UDMA) and 1,6-hexanediol dimethacrylate (HDDMA)). Ultrasonication techniques were used to obtain the two different acrylate solutions i.e., 0.03% SWNTs/ UDMA/ HDDMA(9/1) solution and a 0.03% COOH-SWNTs/UDMA/HDDMA(9/1) solution, consisting of randomly oriented, well dispersed SWNTs. Pristine SWNTs and acid treated SWNTs solutions were then subjected to controlled AC electric fields in order to explore the formation of aligned SWNT-filaments. To assess key morphological features of the as-produced SWNT-acrylate and SWNT-COOH-acrylate nanocomposite samples, such as SWNT distribution and filament thicknesses, transmission optical microscopy has been used to observe the SWNT alignment and filament formation obtained by digitally mapping individual overlapping images. The acquisition of a large field of view with high magnification allows statistically meaningful distribution functions for morphological features to be constructed. Measurements of the as-produced nanocomposite electrical properties in the SWNT alignment direction and transverse to it were used as a macroscale measure to confirm alignment and contiguity of the SWNT-filament structure, with polarized Raman spectroscopy used to assess the degree of SWNT alignment at the local microscale level. It is observed that a combination of exposure time to AC electric field, and its frequency, is the key driver of filament thickness and spacing and that in general, the COOH-SWNTs align to a greater extent than the pristine SWNTs, though they do not form filaments that are as thick and contiguous for the exposure times studied. POLYM. COMPOS., 36:1266–1279, 2015. © 2014 Society of Plastics Engineers

Volume integral equation for analysis of three-dimensional scattering from dielectric frequency-selective structures

The space-domain volume integral equation method is presented for the analysis of three-dimension scattering from dielectric frequency-selective structures involving homogeneous and inhomogeneous lossy materials. The method directly solves for the electric field in order to easily enable the periodic boundary conditions in the spatial domain. The special basis and test functions are introduced to deal with the current continuity in periodic boundaries. The computation of the spatial domain periodic Green’s function (PGF) is accelerated by the modified Ewald transformation, so that a very thick periodic structure can also be analyzed efficiently and accurately. The PGF mentioned above is of free-space type and very smooth and amenable to interpolation. Thus, optimized interpolation procedures for the PGFs can be applied, resulting in a considerable reduction of matrix-filling time without any significant influence on the accuracy. A study of the scattering parameters of a multilayered dielectric periodic structure is accomplished by imposing the boundary conditions in terms of the multimode scattering matrix. Numerical examples show the reliability and accuracy of the proposed method.

Linear Assembly of Oxidized Surface Treated Nanodiamonds in Polymer-Based Nanohybrids by Electric Field Inducement

Linear assembly of densely packed oxidized nanodiamonds (OxNDs) was achieved in polyepoxide-based nanohybrid films. A homogeneous suspension of pre-polymer of polyepoxide and OxNDs was cast onto a polyamide-spacer and subjected to an electric field in order to induce relocation and stretched-assembles of the fillers before the mixture became cross-linked. The OxNDs suspended readily, forming linear assemblies of OxNDs (LAOxNDs) of varying thicknesses, and aligned vertical to the film surfaces. Nanohybrid films with assemblies of LAOxNDs led to a significant enhancement in thermal conductivity while maintained the electrical insulation property of the polyepoxide. Mechanisms for the formation and structural variation of LAOxNDs in the matrix are elaborated regarding the improvement in physical properties. The present ambient-oxidation process and field-induced application are simple, but effective in enhancing the thermal properties of the polymer-based hybrids, and hence, promising for applications in the semiconductor industry, such as thermal interface materials.

Oxidation of nanodiamonds and modulation of their assembly in polymer-based nanohybrids by field-inducement

Linear assembly of densely packed oxidized nanodiamonds (OxNDs) was performed in polymer-based nanohybrid films. A homogeneous suspension of the pre-polymer polyepoxide and OxNDs was placed onto a polyamide spacer and subjected to an electric field in order to induce the relocation and assembly of the fillers before the mixture became cross-linked. The OxNDs suspended readily, forming linear assemblies of OxNDs (LAOxNDs) of varying thicknesses, aligned perpendicular to the film surfaces. Nanohybrid films with linear assemblies of LAOxNDs exhibited a moderate increase in thermal conductivity while maintaining the electrical insulation properties of the polyepoxide. Mechanisms for the field-induced fabrication and the structural variation of LAOxNDs in the pre-polymer matrix are elucidated in relation to the variations in physical properties. The present air oxidation process and field-induced application are simple but effective in enhancing the physical properties of polymer-based hybrids, and hence, has the potential for applying in the fabrication and modulation of nanocomposite materials.

Electric axon guidance in embryonic retina: Galvanotropism revisited

In addition to well-known mechanisms of chemical guidance, growing axons in the nervous system are directed by an extracellular electric field in a process known as galvanotropism. The galvanotropic behavior of nerve cells in vitro was first demonstrated as long ago as 1920. However, it remains unknown whether embryonic nerve tissues generate a similar electric field in order to guide growing axons. The present study reveals that an extracellular voltage gradient exists in the embryonic retina and that this gradient guides the axons of newborn retinal ganglion cells towards their targets. These findings indicate an important role for galvanotropism in the initial orientation of axons that extend over long distances, and provide insight into the mechanisms underlying the proper extension of developing axons in the embryonic brain.

Tracking S4 Movements by Metal-Ion Bridges

Electrical signalling in excitable cells depends on voltage-gated ion channels which open and close in response to changes in membrane potential. The voltage-gated ion channel consists of a central ion-conducting pore domain surrounded by four voltage-sensor domains (VSDs). The VSDs sense changes in membrane potential and confer this information to the pore domain. The fourth segment (S4) of each VSD carries several positively charged residues which gives the VSD its gating ability. S4 must traverse outwards through the membrane electric field in order for the channel to open. The open-state structures of both K and Na channels are known at atomic level through x-ray crystallography. In a previous investigation (Henrion et al., 2012, PNAS 109:8552-8557) we described four closed molecular configurations of a VSD based on 20 engineered metal-ion bridges, Rosetta modelling and molecular dynamics. A subset of these interactions was used to generate a detailed model of the intermediate conformations during VSD gating. Our results suggested that S4 slides >12 A along its axis during gating. Whether or not S4 continues to move after channel opening and during inactivation is not clear. Therefore, in the present study, we used the same technique, with double cysteine mutations and Cd ions, to explored molecular rearrangements in the activated state. Mutated Shaker K channels were expressed in Xenopus oocytes and studied by the two-electrode voltage-clamp technique. We found several new metal ion bridges suggesting possible S4 movements in the activated state.

Method of Moments (MoM) for the Analysis of Dielectric Double Periodic Structures

The space-domain volume integral equation (VIE) method is presented for the analysis of three-dimension (3-D) scattering from dielectric frequency selective structures (DFSS) involved homogeneous and inhomogeneous lossy material. The method solves directly for the electric field in order to easily enable periodic boundary conditions in the spatial domain. The computation of the spatial domain periodic Green’s function (PGF) is accelerated by the modified Ewald transformation. Optimized interpolation procedures for the PGFs can be applied, resulting in a considerable reduction of matrix-filling time without any significant effect on the accuracy.

Approach to a stationary state in a driven Hubbard model coupled to a thermostat

We investigate the dynamics of the Hubbard model in a static electric field in order to identify the conditions necessary to reach a nonequilibrium stationary state. We show that, for a generic electric field, the convergence to a stationary state requires coupling to a thermostatting bath that absorbs the work done by the external field. Following the real-time dynamics of the system, we show that a nonequilibrium stationary state is reached for essentially any value of the coupling to the bath. We characterize the properties of such nonequilibrium stationary states by studying suitable physical observables, pointing out the existence of an analog of the Pomeranchuk effect as a function of the electric field. We map out a phase diagram in terms of dissipation and electric field strengths and identify the dissipation values at which the steady current is largest for a given field.

Electrospray deposition of a graphene-oxide thin film, its characterization and investigation of its resistive switching performance

A novel route to thin-film fabrication of graphene oxide (GO) is presented using a well-known technique, i.e., electrospray deposition. For deposition of the graphene-oxide thin film, grapheneoxide ink containing 0.025 wt% graphene oxide flowing through a metal capillary was subjected to a static electric field in order to generate atomized droplets, thereby depositing a uniform thin film of graphene oxide on an indium-tin-oxide coated polyethylene terephthalate substrate. The quality of the layer was characterized by analyzing the surface morphology and the thickness, and the electrical measurements on the single film were performed. In order to study the resistive switching behavior of GO, a prototype GO-based resistive switching device having an active area of 0.026 mm2 was developed and was analyzed by current voltage measurements. The IV characteristics of the device successfully showed a typical non-volatile resistive switching behavior for a GO layer having the retention times of ∼103 s, thus highlighting the electrospray deposition technology as a reliable candidate for the fabrication of GO layers.

Non-Volatile Memory Behaviour of MFIS Structure with Ba0.7Sr0.3TiO3 Films for Memory Capacitor Application

The growth of strontium doped barium titanate (BST) powder is performed by solid-state reaction. Microstructural characterization by SEM technique confirms the BST film is successfully formed on p-Si (100) substrate by spin coating technique. Dielectric properties of MFIS (Metal/ Ferroelectric/ Insulator/ Semiconductor) designs are measured by impedance analyzer (LCR meter, QuadTech :1730). P-E (polarization-electric field) hysteresis loops are also measured by applying the same triangular wave electric field in order to allow their application in NVFeRAM (Non-Volatile Ferroelectric Random Access Memory). The maximum remanent polarization density (Pr=38.6µC/cm2) is found at BST film 600°C. The film exhibits the potential to be a future promising memory. The results obtained from this research are quite interesting, acceptable, credible and applicable in use for NVFeRAM.

Hybridization of electrostrictive polymers and electrets for mechanical energy harvesting

The topic of this paper is to propose new means for harvesting energy using electrostrictive polymers and electrets. Recent trends in energy conversion mechanisms have demonstrated the abilities of electrostrictive polymers for converting mechanical vibration into electricity. However, these types of generators need a static electric field in order to function, which render the realization of autonomous systems difficult. The goal of the present research consists in determining the possibility of using electrets in order to produce the static field necessary for harvesting energy through electrostrictive polymers. The contribution of this study resides in the design and validation of hybridization between electrostrictive polymers and electrets for the development of μ-generators. Theoretical analysis supported by experimental investigations shows that it was possible to induce a static field in an electrostrictive polymer using an electret, and the energy-harvesting module conversion enabled scavenging power up to 6.05nWcm−3 (mm−1)2 with a static electric field of 8000V/m at 2Hz.

Radial Electric Fields and Transport Barriers

The importance of radial (i.e. perpendicular to the magnetic surface) electric fields was already recognised early in the research on controlled thermonuclear fusion. An initial description of electric field effects in toroidal confinement was given by Budker. Such a configuration with combined magnetic and electric confinement (“magnetoelectric confinement”, where the electric field provides a toroidal equilibrium configuration without rotational transform) was studied by Stix, who suggested that a reactor-grade plasma under magnetoelectric confinement (electric fields of order 1 MV/cm) may reach a quasi-steady-state with ambipolar loss of electrons and some suprathermal ions (e.g. 3.5 MeV α-particles). Experiments such as on the Electric Field Bumpy Torus EFBT provided quite favourable scaling for particle confinement. The possible importance of radial electric fields for transport was in the past repeatedly established. Since the early days the plasma potential has been measured in tokamaks such as ST, TM-4 and ISX-B, but because no significant effects of the radial electric field Er on plasma transport were observed under the machine conditions at that time, no further research was conducted in tokamaks.

Effect of Voltage Pattern on Intensity of Electromagnetic Emission during Electric Flame-Off Process of Ball Bonding Machine

Electromagnetic interference (EMI) can degrade device performance, particularly a sensitive device such as magnetic recording heads. A high applied voltage generates a high electric field in order to break the electrical air gap during a gold ball bonding process. This work, for the first time, investigates the influence of high voltage pattern of a gold ball bond machine on both electric field and magnetic field as an electromagnetic wave by monitoring an intensity of electromagnetic interference. The investigation was carried out by simulation of a live gold ball bond machine operation by using a finite integral technique. The simulation results reveal that the voltage pattern plays an important role in the intensity of electromagnetic radiation (EMR). In conclusion, an ideal voltage pulse of 2 kV and 4 kV generates the highest EMR detected by a monopole antenna. The induced voltage occuring at the antenna reflecting the intensity of EMI blasting was as high as 33.39 V and 71.36 V, respectively. Smoothening the voltage pattern by incrasing the rise time of voltage to 100 ns only, the induced voltage at the antenna was reduced down to 99.90% and 99.92% compairing with the case of an ideal voltage pulse for the peak EFO voltage of 2 kV and 4kV respectively. This concludes the importance of the voltage pattern during a free air ball forming process; hence lowering the risk of the highly sensitive deivce to be damaged by EMI blasting.

Effect of trapped space charge on mechanical deformation induced by electric field

An organic insulating film of polyethylene naphthalene 2,6-dicarboxylate (PEN) was characterized by two complementary techniques: the mechanical deformation of the sample surface, induced by the application of an electric field, was obtained by an image correlation technique named DIC (Digital Image Correlation) and the space charge distributions in the thickness direction were measured by FLIMM (Focused Laser Intensity Modulation Method). The validation of the DIC method, which consists of a following of the successive positions of the surface patterns of the sample, is presented. To validate the algorithms and evaluate the performance of the technique, it was applied to computer-simulated speckle images. In a second step, the experimental system was applied to measure the mechanical deformations of a PEN film previously charged by an electric field in order to have space charge accumulation. This space charge accumulation was quantified by FLIMM. The results show that the mechanical behavior of the sample is modified by the presence of space charge.