Wide Range Of Electric Fields Research Articles

Collection of nanoparticles by electrostatic precipitation operating over a wide range of electric fields

ABSTRACT In the electrostatic precipitation of microparticles, it is common to evaluate the voltages between the corona onset voltage and the breakdown point. However, the charging of particles in the nanoscale size range mainly occurs by diffusion, suggesting the possibility of its occurrence, even at low values. This paper investigates the implications of a wide range of electric fields applied in the collection of nanoparticles (6.15–241.4 nm). Two electrostatic precipitators (P.I. and P.II.), both with plates 10 cm high and 30 cm long, but with different plate spacings (4 and 6.5 cm), were tested using three air velocities (1.9, 2.9, and 3.9 cm/s) and 36 electric fields (0.0 − 5.0 kV/cm). Under the highest electric fields, both precipitators showed efficiencies above 99.9%. Furthermore, nanoparticles were collected before the corona onset voltage, with efficiencies of around 28% (P.I.) and 35% (P.II.). Even though no current was detected by the high voltage source, charges on the particles were measured in electric fields lower than 3.0 kV/cm. The higher the applied voltage, the higher the residual charge of the particles at the precipitator outlet. It is expected that the findings of this work should contribute to the technological development of electrostatic processes for air treatment.

Lateral ambipolar drift of the excess charge carriers in the GaAs-based heterostructures with quantum wells and impurity δ-layers in the adjacent barriers

The low-temperature ambipolar photoconduction in the InGaAs/GaAs and GaAs/AlGaAs heterostructures containing the compositional quantum well (QW) tunnel-coupled with the impurity δ-well have been studied under a wide electric field range. The “stretched” bipolar drift length in the InGaAs/GaAs structure is shown to achieve a few mm at the fields of ∼70 V/cm and exceed that in the GaAs/AlGaAs structure at the comparable field strength by half an order of magnitude. The photoconductivity decay is up to several tens μs long and its behavior is fitted by the single- and “stretched-" exponent functions. The obtained results are shown to be caused by spatial separation of the non-equilibrium charge carriers in the potential profile engineered by such QW configuration and the dispersion law of holes in them.

Two- and three-body attachment, electron transport and ionisation in water-air mixtures

Three-body electron attachment in the mixtures of H2O and dry air have been measured over a wide range of the density-reduced electric field, E/N, from 3–130 Td and gas pressures, for mixture combinations ranging from 1% to 50% of H2O. We have measured the regions of three-body attachment (3–30 Td) and two-body dissociative attachment (40–130 Td). Besides, the increasing amount of H2O in the mixture causes an increase in the three-body reaction rates of up to two orders of magnitude in comparison with that measured for dry air. On the other hand, the three-body attachment coefficients exceed the two-body ones (dissociative attachment) at high pressures. Good agreement has been found with previous measurements of H2O-dry air mixtures with H2O concentrations of up to 2%. We know of no previous work for higher H2O concentrations. Values of the effective ionisation coefficients and longitudinal diffusion coefficients derived from the same measurements are also presented.

Very low excess noise Al0.75Ga0.25As0.56Sb0.44 avalanche photodiode.

AlxGa1-xAsySb1-y grown lattice-matched to InP has attracted significant research interest as a material for low noise, high sensitivity avalanche photodiodes (APDs) due to its very dissimilar electron and hole ionization coefficients, especially at low electric fields. All work reported to date has been on Al concentrations of x = 0.85 or higher. This work demonstrates that much lower excess noise (F = 2.4) at a very high multiplication of 90 can be obtained in thick Al0.75Ga0.25As0.56Sb0.44 grown on InP substrates. This is the lowest excess noise that has been reported in any III-V APD operating at room temperature. The impact ionization coefficients for both electrons and holes are determined over a wide electric field range (up to 650 kV/cm) from avalanche multiplication measurements undertaken on complementary p-i-n and n-i-p diode structures. While these ionization coefficients can fit the experimental multiplication over three orders of magnitude, the measured excess noise is significantly lower than that expected from the β/α ratio and the conventional local McIntyre noise theory. These results are of importance not just for the design of APDs but other high field devices, such as transistors using this material.

Investigation of Structural and Electrical Properties of Al2O3/Al Composites Prepared by Aerosol Co-Deposition

As the microelectronic industry develops, components that can perform several different tasks receive increasingly more attention, resulting in multifunctional materials being highly sought after. Al2O3 is widely present in electronic applications as a protective coating or as an electrical and thermal insulator due to its mechanical and thermal stabilities and chemical inertness. Al2O3 is also an important dielectric material, with high resistivity and stable permittivity over a wide range of temperatures and electric fields, but its modest permittivity necessitates large effective areas or extremely thin layers when a large capacitance is desired. Composites consisting of discrete conducting phases within an insulating matrix can produce large capacitance via Maxwell–Wagner polarization. In this work, Al2O3/Al composite thick films with different volume ratios of Al were prepared using the aerosol deposition method. A relative dielectric permittivity (εr′) of 800 at 1 MHz was achieved at 27 vol% of Al, a sixty-sevenfold enhancement compared to Al2O3. On the other hand, dielectric losses, tan(δ), at 1 MHz increased from 0.01 for Al2O3 up to 0.58 for the composite with 27 vol% of Al. A finite-element model of the composites was implemented, supporting the nonlinear electrical behavior of the composites as function of vol% of Al. Our results show novel possibilities for the applications of Al2O3-based materials in the microelectronic industry, especially for temperature-sensitive applications, for which the integration strengths of aerosol deposition are valuable.

Thermo-electro-mechanical aging and degradation of conductive 3D printed PLA/CB composite

Conductive polymeric composites consist of a polymeric matrix filled with conductive particles, providing electrical properties to a naturally insulating material. Their use in material extrusion printers provides great flexibility to geometrical design functional components. However, the degradation of their mechanical behavior during and after the application of electric currents is still absent in the literature. The flow of electric currents induces material heating affecting the strength, and mechanical deformation alters the electric properties leading to bilateral dependences. These processes evolve during the application of electric fields and may degrade the material behavior permanently. In this work, we address these questions taking as baseline material a 3D printed conductive Polylactic Acid (PLA)/ Carbon Black (CB) composite. We performed multi-physical characterizations on samples with different printing orientations and lengths evaluating: i) electric behavior under direct current (DC) regime and a wideband analysis by a Frequency Response Analysis; ii) thermo-electrical behavior studying the temperature field evolution under applied electric fields; iii) thermo-mechanical behavior under uniaxial tension for different testing temperatures; iv) thermo-electrical aging/degradation effects on the mechanical behavior. The study considers a wide range of electric fields (from 180 V/m to 600 V/m) and temperatures (from 25° to 130 °C). The results show enhanced electrical conductivity and mechanical stiffness when using a printing orientation parallel to the electro-mechanical loading. This coupled response is highly influenced by thermal effects due to Joule heating, especially when surpassing the glass transition and cold crystallization temperatures of the composite. The occurrence of such phase transitions governs the material degradation by promoting the growth of mesostructural pores during heating cycles arising from the application of electric fields. The obtained results are essential to unravel changes in mechanical properties when standing for continuous electric conduction and provide an experimental background for the lifetime expectance for the devices and possible thermo-electro-mechanical failure.

Short-range order and charge transport in silicon-rich pyrolytic silicon oxynitride

Amorphous SiOxNy films were grown by pyrolysis in a reduced pressure reactor at T = 800 °C for different SiH2Cl2/NH3 ratios from 1/5 to 1/1. The resulting analysis for the photoelectron spectra showed that, in addition to silicon and nitrogen, the samples composition includes oxygen, apparently, due to the presence of residual traces of oxygen and/or water. The red shift of the fundamental absorption edge indicates the presence of Si-Si bonds in SiOxNy. In a wide range of electric fields and temperatures, the charge transport mechanisms in SiOxNy are experimentally studied. The experimental results are compared with the calculation based on different trap ionization models. The best agreement between the experiment and calculation was obtained using the model of phonon-assisted tunneling between neighboring traps. The increase in the SiOxNy leakage current, when changing the SiH2Cl2/NH3 ratio from 1/5 to 1/1, is explained by the trap concentration increase.

Space-charge domains in n-type GaN epilayers under pulsed electric field

Formation and drift of space-charge domains with velocity of sound were experimentally observed in charge current traces of a high-quality lightly doped GaN semiconductor under pulsed electric fields at room and liquid nitrogen temperatures. A GaN epilayer was developed on an Ammono GaN substrate to achieve the electron density and low-field mobility values of 1.06 × 1016 cm−3 and 1021 cm2/V s (at 300 K) and 0.21 × 1016 cm−3 and 2652 cm2/V s (at 77 K), respectively. The formation of moving space-charge domains was observed only in samples with the lengths of 1 mm and longer arising at the critical electric fields starting from ∼0.4 and ∼0.8 kV/cm at 77 and 300 K, respectively. Basic electron transport parameters were found investigating short samples with the lengths of 65 μm and shorter in a wide range of electric fields up to 150 kV/cm, at which the thermal material breakdown occurred. The critical length of a sample for space-charge domain formation was estimated considering the acoustoelectric effects in analysis of pulsed current–voltage characteristics, thus defining the constraints for the design of GaN-based power electronic devices.

The Schottky emission effect: A critical examination of a century-old model

Using a quantum mechanical calculation, we investigate the fundamental limitations of the Schottky emission (SE) model for its applications to electron injection into dielectrics from a metal or semiconductor electrode. This work covers a wide range of electric fields from 0.01 to 10 MV/cm and a large temperature span with many barrier height values (ΦB). We conclude that the SE model is only applicable for a very small class of dielectrics under 0.1 MV/cm and at high temperatures over ∼330 K. For many defective dielectrics with large barrier heights (ΦB ≥ ∼1.5 eV) in back-of-line/middle-of-line/metal–insulator–metal capacitor applications, the corresponding electric fields for the measurable currents far exceed 0.1 MV/cm, and up to 10 MV/cm, the application of the SE model is likely invalid so that the extracted ΦB values may not be correct. We provide a quantitative guide to avoid future misapplications of the SE model.

Spectroscopy characteristics and decay properties of plasma-embedded atoms in external electric and magnetic fields

This paper describes a computational approach within the framework of relativity theory for explaining the spectral and decay properties of atoms and ions embedded in a plasma and also in the presence of applied external electric and magnetic fields. It uses the configuration interaction approximation and the analytical potential derived from general ion-sphere theory to represent the atomic interactions within the plasma. In the model, the Dirac–Coulomb–Hamiltonian is reconstructed and the effects of the weak electric and magnetic field are treated as small perturbations. The eigenvalues for the orbitals and (radial) wave functions are obtained through the Dirac equations. A diagonalization is performed to include these plasma, electric, and magnetic terms. As an example, an environment with a hot-dense plasma and weak electric and magnetic fields is considered, where the interaction is much weaker than the Coulomb interaction, yet much stronger than the spin–orbit interaction. The atomic structures and spectra of a selected hydrogen atom are presented for a wide range of electron densities, temperatures, and electric and magnetic fields. The behavior of the energy and radiative transitions with respect to these interactions is analyzed in detail. The results obtained from the proposed approach are critically compared with other available results. The present study not only advances our understanding of the electronic structures and radiation characteristics of atomic systems in external fields but may also be relevant for astrophysics and laboratory experiments, especially on the solar corona, laser-produced plasmas, and so on.

A Simple Analytical Model of a GaN MODFET to Study its DC and RF Performance

This work presents a theoretical study of a GaN MODFET considering accurate velocity field relation of GaN for a wide range of electric field. The analytical expression of different DC parameters such as drain current, mutual conductance and drain conductance of the device has been derived and their variation over different field regions has been investigated. This work has also been extended to study the RF parameters like cut-off frequency and maximum operating frequency of the device. The threshold voltage of the device is also derived and studied in terms of the thickness of the doped AlGaN layer and mole fraction of AlGaN. The mathematical model presented here is calibrated with the experimentally available results reported earlier and a good agreement has been observed.

Electric field dependence of terahertz wave emission in temperature-controlled GaAs epitaxial films

We have investigated the dependence of terahertz wave emissions on the internal electric field in undoped GaAs/n-type GaAs epitaxial structures irradiated by ultrashort laser pulses. The undoped layer has an electric field, the strength of which was controlled by the temperature in addition to the undoped layer thickness. We observed the electric field dependence of the terahertz waveform, and the results were explained by the calculation of the transient dynamics of electrons and phonons under electric fields. Furthermore, we indicated that the terahertz amplitude can be linearly controlled by the electric field strength in a wide electric field range.

Multiphonon trap ionization mechanism in amorphous SiNx

The charge transport mechanism in amorphous silicon nitride (a-SiNx) is experimentally analyzed in a wide range of electric fields and temperatures. The Frenkel effect with thermally assisted tunneling (TAT) and the multiphonon mechanism were used to describe the trap ionization. It is shown that the widespread Frenkel effect with TAT formally describes the experiment, but the agreement with the experiment is obtained if a small frequency factor (109 s−1) and a large tunneling effective mass (m*=3m0) are used. Thus, the Frenkel effect does not describe the charge transport in a-SiNx. The charge transport in a-SiNx is satisfactorily described by the multiphonon trap ionization mechanism with the following parameters: m* = 0.6m0, thermal and optical energies - WT = 1.6 eV and WOPT = 3.2 eV, respectively.

Introducing the potency of new boron-based heterocyclic anion receptor additives to regulate the solvation and transport properties of Li-ions in ethylene carbonate electrolyte of Li-Ion battery: An atomistic molecular dynamics study

Development of new solvent/additive electrolyte is emerging field of research towards the improvement of ion transport and solid-electrolyte-interface formation in Li-ion battery (LIB). We perform extensive atomistic molecular dynamics simulations with LiPF6 in ethylene carbonate (EC) in presence of a new class of boron (B) based heterocyclic anion receptor additives; C2HBNO(NO2)2, and C2HBNS(NO2)2 and their trimers B[C2HBNO(NO2)2]3, and B[C2HBNS(NO2)2]3 to investigate the efficacy of this class of additives in regulating the solvation and transport properties of Li+ ions as compared to the reference LiPF6/EC solution that contained TPFPB, a commonly used B-based additive. Our designed additives in several aspects show their efficacy. Among all, C2HBNS(NO2)2 is found to be the most efficient PF6- trapper that reduces ion pair formation. It promotes diffusion of Li+ and EC, improves the transference number, and reduces viscosity of solution, as compared to TPFPB. Further, it improves the ionic conductivity and drift velocity under a wide range of temperatures and external electric fields, respectively. Some of the computed properties are in agreement with the available experimental results. Our study would facilitate the design and synthesis of this class of additives to open up new possibilities of accelerating the LIB power sources for portable appliances.

Cold sintering of the ceramic potassium sodium niobate, (K0.5Na0.5)NbO3, and influences on piezoelectric properties

Cold Sintering was applied to densify a Potassium-Sodium Niobate solid solution composition, 0.5KNbO3-0.5NaNbO3 (KNN); the process uses a transient chemical sintering aid, moderate pressure (400 MPa), and temperatures between 230–300 °C to obtain ceramics of ∼92 to 96 % theoretical density. Typically, sintering temperatures between ∼1000−1050 °C are required to density KNN using conventional methods. In this paper, the densification was investigated during heating, particularly the shrinkage in the first 60 min of the cold sintering process. The low-field dielectric and electrical properties of the resulting ceramics were found to be comparable to conventionally sintered KNN. Electric fields up to 80 kV/cm could be applied, however the ceramics showed pinched hysteresis loops, even after poling over a wide range of temperatures and electric fields. A Rayleigh analysis was used to investigate domain dynamics and high reversible permittivity. The irreversible behavior was an order of magnitude lower than in conventionally sintered KNN, likely associated with defect pinning of ferroelectric domains. A Transmission Electron Microscopy (TEM) study revealed a high density of line defects in most grains; dislocations in the grains limit poling and domain wall movement, thus suppressing both the piezoelectric properties and the hysteresis. Furthermore, TEM observations indicated crystalline grain boundaries that were faceted with terrace kink ledges. These observations point to the importance of the initial powder optimization and grain boundary diffusion when using cold sintering to prepare ceramics that are intended to show bulk cooperative properties such as ferroelectricity. The impact of limited high temperature homogenization of bulk diffusional processes is discussed.

Combined Arrhenius-Merz Law Describing Domain Relaxation in Type-II Multiferroics.

Electric fields were applied to multiferroic TbMnO_{3} single crystals to control the chiral domains, and the domain relaxation was studied over 8decades in time by means of polarized neutron scattering. A surprisingly simple combination of an activation law and the Merz law describes the relaxation times in a wide range of electric field and temperature with just two parameters, an activation-field constant and a characteristic time representing the fastest possible inversion. Over the large part of field and temperature values corresponding to almost 6 orders of magnitude in time, multiferroic domain inversion is thus dominated by a single process, the domain wall motion. Only when approaching the multiferroic transition other mechanisms yield an accelerated inversion.

Electrical control of crossed Andreev reflection and spin-valley switch in antiferromagnet/superconductor junctions

We study the subgap transport through the antiferromagnet/superconductor (AF/S) and antiferromagnet/superconductor/antiferromagnet (AF/S/AF) junctions controlled by electric field in a generic buckled honeycomb system, such as silicene, germanene, and stanene. In the presence of electric field and antiferromagnetic exchange field, the spin-valley polarized half-metallic phase can be achieved in the honeycomb system due to the spin-orbit coupling, which affords an opportunity to generate the pure crossed Andreev reflection (CAR). It is found that the pure CAR can be generated without local Andreev reflection (AR) and elastic cotunneling (EC) over a wide range of electric field. A spin-valley switch effect can be realized between the pure CAR and the pure EC by adjusting the electric field. The properties of AR process and CAR process strongly depend on the spin-valley polarized states. Our results suggest that the device can implement an electrical measurement of the CAR process and spin-valley switch.

Field-insensitive giant dynamic piezoelectric response and its structural origin in (Ba,Ca)(Ti,Zr)O3 tetragonal-orthorhombic phase-boundary ceramics

BaTiO3 (BT)-based ceramics usually exhibit superior quasi-static piezoelectric response but relatively low electrostrain, which limits their actuator applications. In this study, lead-free (Ba0.835+xCa0.165-x)(Ti0.91Zr0.09)O3 (x = 0–0.06) (BaxCTZ) ceramics with the compositions close to the tetragonal (T)-rich side of orthorhombic (O)-T polymorphic phase boundary (PPB) were reported to exhibit a field insensitive giant dynamic piezoelectric response (d33* >1050 pm/V) over a wide electric field range up to 2 kV/mm, resulting in the large strain value of ∼0.21 %. Detailed structural investigations combined with various electrical properties measurements reveal that the superior dynamic piezoelectric response is attributed to the combination of piezoelectric effect and domain switching behavior due to the chemical modulated O-T PPB, and the field induced partially irreversible T-O phase transition. The results demonstrate that the studied compositions have great potential for applications of lead-free actuator piezoceramics.

In situ TEM measurement of electrical properties of individual BaTiO3 nanocubes

We report on the measurement of the electrical properties of individual pristine and doped BaTiO3 nanocubes by using in situ transmission electron microscopy with a two-electrode configuration. The dimensions of the nanocubes tested are between 10 and 20 nm, which rendered their in situ electrical characterization challenging. We characterized 4%Cr and 5%La (atomic percentage) doped BaTiO3 nanocubes and compared them with the properties of pristine BaTiO3 nanocubes synthesized by the same solvothermal method. We found that the resistance of all three types of nanocubes when displayed in log-scale shows a nearly linear dependence on the applied electric field (R2 ≥ 0.95) over a wide range of electric fields (50–900 kV/cm). Compared with pristine BaTiO3 nanocubes, the resistance of both 4%Cr and 5%La doped nanocubes showed reduced variation rates with respect to the electric field, with 5%La doping, demonstrating a better reduction in the variation rate. By developing techniques capable of evaluating the properties of individual BaTiO3 nanocubes, we expect that our work to open the door to the use of BaTiO3 nanomaterials in the design of future multilayer ceramic capacitors with improved volumetric efficiency and ferroelectrics-enabled nanodevices with advanced functionality.

Characteristics of current injection in the narrow-band p-CuTlS single crystal

The volt-amperage characteristics (VAC) and electrical conductivity of p-CuTlS single crystal have been investigated in a wide range of electric fields at 100 ÷ 300 K temperature range. It has been determined that in a narrow-band (Eg = 0.32 eV) CuTlS crystal, the current in an electric field of 10   40 V/cm, an increase in current is observed in consequence of ionization of local levels.