Range Of Electric Fields Research Articles

Enhanced the dielectric and energy storage properties of BaZr1-xTixO3 lead-free ceramics

Ferroelectric BaZr1-xTixO3 (0 ≤ x ≤ 8) ceramic composition was synthesized by using solid state reaction method. The material was calcined at 1250 °C in air. In this work we have examined that the ferroelectric, energy storage and microwave dielectric properties of BaZr1-xTixO3 at room temperature. The XRD patterns showed that BaZr1-xTixO3 composition is of perovskite structure with a space group of Pm-3m. SEM morphology shows that increase in number of grain boundaries result in increase of polarisation. The energy storage properties were calculated from (P-E) loops by varying the electric field (range) and composition of the ceramic material. It has observed that the relative permittivity increases along with temperature. The storage energy density (Wrec) has been reported 0.043 J/cm3 , whereas efficiency (ɳ) was 57% at room temperature and 40 kv/cm at contents (x=0.06).The Barium zirconium titanate (BZT) will be an excellent candidate material for storage energy devices.

Trampoline-Shaped Micro Electric-Field Sensor for AC/DC High Electric Field Measurement

The measurement of high electric field is widely used in applications such as power grid, electrical equipment, space launch, petroleum industry, and meteorological monitoring. Traditional electric field measurement methods, such as field mills, are bulky and cause electric field distortion. In this article, we presented a trampoline-shaped microelectric field sensor (E-sensor) based on microelectromechanical system (MEMS). The micro E-sensor uses the effect of electrostatic induction, which generates force that drives the vibration of a piezoresistive film and converts the electric field into a differential voltage signal. The presented E-sensor can measure both ac and dc high electric fields with relatively high resolution and wide range. Through experimental measurement, the device exhibits an ac resolution of 172 V/m/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> and a linear measurable electric field range of 312 V/m to over 700 kV/m. The presented E-sensor has good performance with mm-level size and low cost, which could be mass produced for broad applications.

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.

Determination of impact ionization parameters for low gain avalanche detectors produced by HPK

A set of unirradiated Low Gain Avalanche Detectors from Hamamatsu Photonics from the HGTD prototype 2 run for the upgrade of experiments at the High Luminosity Large Hadron Collider were used to determine the impact ionization parameters for silicon, particularly in the electric field range of ∼30 V/μm which is of interest for LGADs. The parameters' dependence on temperature was also determined. Their validity on irradiated sensors up to 2.5·1015 cm-2 was also tested and found to be acceptable at low biases but further work should be done to determine the dependence on fluence.

Constructing an Overall Static Negative Capacitance Effect via Energy Landscape Designing

AbstractThe negative capacitance (NC) effect in ferroelectrics and antiferroelectrics is promising to reduce power dissipation and enable energy storage applications. However, the limited electric field scale and hysteresis properties of NC effect in ferroelectrics and antiferroelectrics seriously limit its application in transistors and energy‐storage supercapacitors. Here, an overall (non‐local) static (hysteresis‐free) NC effect is developed via energy landscape designing. The ferroelectric structure is introduced into the traditional antiferroelectric PbZrO3 film, thus the single‐well energy landscape is tuned to an upper convex function. This anomalous energy landscape generates a hysteresis‐free and single‐valued polarization‐electric field behavior (P–E) curve with a negative slope (dP/dE &lt; 0), which guarantees the NC effect is static and available over the entire electric field range. Such an NC effect in PbZrO3 film is stabilized by connecting a dielectric Al2O3 layer in series. This finding advances the practical application of the NC effect, especially in transistors and supercapacitors.

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.

A Bridge-Shaped Vibration Energy Harvester with Resonance Frequency Tunability under DC Bias Electric Field.

A vibration piezoelectric energy harvester (PEH) is usually designed with a resonance frequency at the external excitation frequency for higher energy conversion efficiency. Here, we proposed a bridge-shaped PEH capable of tuning its resonance frequency by applying a direct current (DC) electric field on piezoelectric elements. A theoretical model of the relationship between the resonance frequency and DC electric field was first established. Then, a verification experiment was carried out and the results revealed that the resonance frequency of the PEH can be tuned by applying a DC electric field to it. In the absence of an axial preload, the resonance frequency of the PEH can be changed by about 18.7 Hz under the DC electric field range from −0.25 kV/mm to 0.25 kV/mm. With an axial preload of 5 N and 10 N, the resonance frequency bandwidth of the PEH can be tuned to about 13.4 Hz and 11.2 Hz, respectively. Further experimental results indicate that the output power and charging response of the PEH can also be significantly enhanced under a DC electric field when the excitation frequency deviates from the resonance frequency.

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.

Optical refraction and absorption spectra in perturbed monolayer PbBiI

We investigate the optical properties of a noncentrosymmetric quantum spin Hall insulator in the presence of electric and magnetic fields. We employ the Kubo formula to engineer the optical redshift and blueshift phenomena through the interplay between the bulk gap, the Rashba-like gap, and the external fields. Intriguingly, for a range of electric (magnetic) fields, the refracted and absorbed lights exhibit direct (indirect) interband optical transitions. Accordingly, for a critical electric field, optical refraction and absorption spectrum decreases gradually and becomes constant, respectively. While for a critical magnetic field, step-like jumps appear in the optical coefficients. All these findings are discussed in the context of symmetry breaking.

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.

Plasma enhanced atomic layer deposition of textured aluminum nitride on platinized substrates for MEMS

We demonstrate an N2 plasma-enhanced process for inducing (0001)-oriented ALD-grown AlN on planar substrates. We evaluate the impact of {111}-textured Pt as a growth template, precursor chemistry, dose time, stress-engineered substrates, inductively coupled plasma conditions for film bombardment during growth, and ALD equipment configurations. The thin film transverse piezoelectric coefficient e31,f determined from measurements on microelectromechanical system cantilevers coated by PEALD AlN is reported to be −0.53 ± 0.03 C/m2. An analysis of the Pt-AlN interface properties based primarily on depth-profile x-ray photoemission spectroscopy and transmission electron microscopy-energy dispersive spectra is presented. Other than the c axis wurtzite (0001) diffraction peak, no other AlN peaks were observed above the detection limits for XRD measurements. The XRD rocking-curve full-width half-maximum of the 0001 peaks was 2.9° omega, which was achieved on {111}-textured Pt. The relative dielectric constant was measured to be 8.1 &amp;lt; K &amp;lt; 8.6, and an average dielectric loss of &amp;lt; 0.01 was observed within the applied electric field range of ±3350 kV/cm at 10 kHz. The leakage current of the textured AlN was quite low at 1.5 × 10−6 A/cm2 over the applied field range of ±1820 kV/cm.

Negative Capacitance in HfO2 Gate Stack Structures With and Without Metal Interlayer

In this work, we experimentally explore and compare FET gate stacks with and without an inner metal plane between a linear dielectric (SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) and a ferroelectric layer (Si-doped HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) operating in the negative capacitance (NC) regime. The use of nanosecond-range pulses enables us to observe hysteresis-free NC and reconstruct the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula> -shaped polarization-voltage curves. The devices with the inner metal plate show a higher equivalent NC value, which offers the potential for a higher differential amplification in a NC-FET. However, such a NC region is observed over a smaller range of electric field and polarization, which leads to hysteresis. Moreover, the presence of a metal layer in between the ferroelectric and the insulator favors domain formation resulting in destabilization of the NC effect. For the gate structure where the ferroelectric and the insulator are in contact, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula> -shaped polarization-voltage curve shows a better agreement with Landau–Ginzburg–Devonshire formalism for the monodomain state. The uniform polarization closely mimicking the monodomain state is possible due to the polarization imprint occurring due to the structural asymmetry. By nanometer resolution polarization mapping via off-resonance piezoelectric force microscopy (PFM), we corroborate the presence of imprint, which can intrinsically stabilize one ferroelectric state. Overall, the article provides an experimental demonstration that the absence of the inner metal plane in the gate structures stabilizes the NC regime favorable for hysteresis-free NC-FET.

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.

High Energy Storage Density in Nanocomposites of P(VDF-TrFE-CFE) Terpolymer and BaZr0.2Ti0.8O3 Nanoparticles.

Polymer materials are actively used in dielectric capacitors, in particular for energy storage applications. An enhancement of the stored energy density can be achieved in composites of electroactive polymers and dielectric inorganic fillers with a high dielectric permittivity. In this article, we report on the energy storage characteristics of composites of relaxor terpolymer P(VDF-TrFE-CFE) and BaZr0.2Ti0.8O3 (BZT) nanoparticles. The choice of materials was dictated by their large dielectric permittivity in the vicinity of room temperature. Free-standing composite films, with BZT contents up to 5 vol.%, were prepared by solution casting. The dielectric properties of the composites were investigated over a wide range of frequencies and temperatures. It was shown that the addition of the BZT nanoparticles does not affect the relaxor behavior of the polymer matrix, but significantly increases the dielectric permittivity. The energy storage parameters were estimated from the analysis of the unipolar polarization hysteresis loops. The addition of the BZT filler resulted in the increasing discharge energy density. The best results were achieved for composites with 1.25–2.5 vol.% of BZT. In the range of electric fields to 150 MV/m, the obtained materials demonstrate a superior energy storage density compared to other P(VDF-TFE-CFE) based composites reported in the literature.

Study of structural, electrical and hyperfine properties of Dy doped YFeO3

Investigations on effect of Dysprosium (Dy) on structural and electrical properties of polycrystalline Yttrium Iron Oxide (YFeO3) are presented in this paper. Y1xDyxFeO3(x = 0,0.2,0.4,0.6,0.8) samples are prepared through sol-gel process. Rietveld refined XRD plots confirms formation of mono phase orthorhombic structures. From the Rietveld data, lattice parameter values are found to increase with increase in Dy concentration. Raman spectroscopic study enables us to understand the subtle changes occurring in crystal structure due to Dy doping and also confirms the pure phase of samples. When Dy+3 is doped in place of Y+3, Raman bands are seen to be shifted to lower frequencies, which indicates an increase in lattice constants in the samples. SEM morphology investigations demonstrate that grains are not homogeneous in size and are irregular in shape. Up to x = 0.4, J-E graphs indicate a rise in leakage current density but however on further substitution of Dy, leakage current is found to decrease. From ln J vs ln E plots, it is observed that Ohmic conduction dominates the whole electric field range. Room temperature 57Fe Mössbauer studies dismiss any existence of magnetic impurities and confirm that samples have magnetic ordering.

Oriented external electric fields act as a “switch” of Pt-M/BC3N2 diatomic catalysts activate pristine ammonia borane dehydrogenation: A DFT study

In this paper, the Pt-M/BC3N2 (M= Ag, Al, Au, Co, Cr, Cu, Fe, Ir, Mn, Mo, Nb, Ni, Pd, Pt, Re, Rh, Ru, Se, Ta, Ti, V, W, Zn, La, Ce, Zr, Hf, Cd, Hg and Y) diatomic catalyst structure was constructed and used to activate Ammonia Borane (AB) under external axial electric field by the First-principles calculation method. By changing the size of applied electric field, we found that the activation of N-H bond in AB can be realized only on Pt-M/BC3N2 (M=Al, Zn, Hf, Y) diatomic catalyst, and the effective electric field range is different. Further calculation showed that Pt-Y/BC3N2 diatomic catalyst could not achieve the break of B-H bond. So, for Pt-M/BC3N2 (M=Al, Zn, Hf) diatomic catalyst, further, sequentially by applying an applied electric field, we achieve the break of the B-H bond in AB and the formation of 1 mol H2. This suggests that the electric field can act as a “switch” for activation of AB molecules.

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.

A versatile technique for micro and nano structuring of conductive thin metal layers using electric field assisted dissolution

A simple, versatile technique for structuring conductive thin metal films is proposed. Over the last years, glass poling and electric field assisted dissolution of metal nanoparticles and films have been the basis of new approaches for fabrication of micro and nanostructures on glass. Here we demonstrate how the sequential combination of glass poling and electric field assisted dissolution can be used to circumvent the necessity of glass as supporting substrate. In short, a patterned electrode is applied to selectively modify by glass poling an auxiliary glass substrate that is later used to induce indirect electric field assisted dissolution of a metal layer deposited on an arbitrary substrate. The proposed method is verified by microstructuring conductive thin metal layers (Ag and Cu) deposited on silicon wafers. This technique enables transferring the pattern from a primary electrode onto conductive thin metal film using inexpensive equipment and the process duration is independent on the pattern area. The primary electrode can be used many times to fabricate selectively modified auxiliary glass substrates and the only limitation on the substrate supporting the final metal microstructure is to be able to sustain moderately elevated temperature and electric field for couple of hours. This method turns out to reproduce the original pattern better than other approaches based on glass poling. Overall, the proposed method significantly expands the application range of glass poling and electric field assisted dissolution as competitive structuring techniques.

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.

All field emission models are wrong, … but are any of them useful?

Field emission data are often represented on a Fowler–Nordheim plot but a new empirical equation has been recently proposed to better analyze experiments. Such an equation is based on approximations of the Murphy and Good model and predicts that a constant parameter κ, depending only on the work function of the emitter, can be extracted from the data. We compared this empirical equation with simulations of the Murphy and Good model in order to determine the range of validity of the approximations and the robustness of the relationship between κ and the work function. We found that κ is constant only over a limited range of electric fields and so depends significantly on the field enhancement factor. This result calls into question the usefulness of the new empirical equation.