Search

We demonstrate a method for broadband tunable continuous frequency electric field measurement based on the DC Stark effect in Rydberg atoms. In our experiment, we place a pair of parallel electrode plates inside the atomic vapor cell, utilizing the DC Stark effect to induce splitting and shifting of the Rydberg energy levels, thereby altering the resonance frequency of the Stark subpeaks. By employing the 52D5/2 Rydberg state, we achieve electric field measurements in the frequency range of 5.083–14.470 GHz. At an EDC of 3.45 V/cm and a resonant microwave frequency of 14.470 GHz, using heterodyne technology, the microwave electric field sensitivity is 538.89 μV/cm/√Hz, with a linear dynamic range of 23 dB. In comparison, a Rydberg heterodyne receiver with an EDC of 0 V/cm and a resonant microwave frequency of 5.083 GHz has a sensitivity of 5.43 μV/cm/√Hz and a linear dynamic range of 51 dB. This work will promote the study of atomic microwave receivers in continuous microwave frequency measurement. [ABSTRACT FROM AUTHOR]

Momentum resolved 4D-STEM, also called center of mass (CoM) analysis, has been used to measure the long range built-in electric field of a silicon p–n junction. The effect of different STEM modes and the trade-off between spatial resolution and electric field sensitivity are studied. Two acquisition modes are compared: nanobeam and low magnification (LM) modes. A thermal noise free Medipix3 direct electron detector with high speed acquisition has been used to study the influence of low electron beam current and millisecond dwell times on the measured electric field and standard deviation. It is shown that LM conditions can underestimate the electric field values due to a bigger probe size used but provide an improvement of almost one order of magnitude on the signal-to-noise ratio, leading to a detection limit of 0.011 MV cm − 1. It is observed that the CoM results do not vary with acquisition time or electron dose as low as 24 e−/A2, showing that the electron beam does not influence the built-in electric field and that this method can be robust for studying beam sensitive materials, where a low dose is needed. [ABSTRACT FROM AUTHOR]

This paper reports on electric field measurements, using the electric field-induced second harmonic (E-FISH) method, sampling the spatial structure and temporal development of DC-driven positive streamer coronas in atmospheric-pressure air at relevant timescales to examine the self-pulsating behavior of the discharge. The discharge is triggered from a point-to-plate geometry and consists of transient coronas, which bridge the inter-electrode gap and pulsate at about 3 kHz, superimposed with a persisting glow corona. The measurements presented challenge the phenomenological explanation for the pulsations based on field recovery at the anode driven by the evacuation of positive ions by electric drift effects and hint at a propagating wave-like feature from the plate-cathode to the tip-anode. [ABSTRACT FROM AUTHOR]

We demonstrate a continuously tunable electric field measurement based on the far off-resonant AC stark effect in a Rydberg atomic vapor cell. In this configuration, a strong far off-resonant field, denoted as a local oscillator (LO) field, acts as a gain to shift the Rydberg level to a high sensitivity region. An incident weak signal field with a few hundreds of kHz difference from the LO field is mixed with the LO field in the Rydberg system to generate an intermediate frequency signal, which is read out by Rydberg electromagnetically induced transparency (Rydberg-EIT) spectroscopy. Not like resonant EIT-Autler–Townes spectra, we realize the electric field measurement of the signal frequency from 2 to 5 GHz using a single Rydberg state. The detectable field strength is down to 2.25 μV/cm with sensitivity of the electrometry 712 nV cm−1 Hz−1/2, and a linear dynamic range is over 65 dB. The detectable field strength is comparable with a resonant microwave-dressed Rydberg heterodyne receiver using the same system, which is 0.96 μV/cm with sensitivity of 304 nV cm–1 Hz−1/2. We also show the system has an inherent polarization selectivity feature. Our method can provide high sensitivity of electric field measurement and be extended to arbitrary frequency measurements. [ABSTRACT FROM AUTHOR]

We characterized the electric field distribution of GaN-on-GaN p–n diodes with partially compensated ion-implanted edge termination (ET) using an electric field induced second harmonic generation technique (EFISHG). The distributed electric field from the anode to the outer edge of the ET demonstrates the effectiveness of the ET structure. However, EFISHG also shows that its effectiveness is strongly dependent on the acceptor charge distribution in the ET's partially compensated layer (PC). A generally lower amount of acceptor charge can be inferred from the measured electric field distribution resulting from excessive ion implantation energy or dose during ET fabrication and causing lower than optimal breakdown voltage. Localized field crowding can be observed when the remaining acceptors uncompensated by the implant in the PC layer are nonuniformly distributed around the periphery of the devices. Important information can be obtained from these direct electric field measurements and used for optimizing the device design and fabrication process. [ABSTRACT FROM AUTHOR]

Ta-doped HfO2 thin films grown on Pt/Ti/SiO2/Si by reactive sputtering possess strong ferroelectric properties, as detected by corresponding polarization vs electric field measurement and mesoscopic piezoresponse force microscopy. Capacitance/current-electric field curves are used to reveal the substances with ferroelectric properties in the thin films. The ferroelectricity of Ta-doped HfO2 is influenced by Ta contents. The remanent polarization Pr can reach ∼53 μC/cm2 by optimizing the Ta percentage. X-ray diffraction and Raman scattering analyses indicate only the presence of monoclinic phase peaks in undoped HfO2 thin films, while Ta doping promotes the formation of the ferroelectric phase (orthorhombic Pca21). X-ray photoelectron spectroscopy demonstrates that the incorporation of Ta5+ within the HfO2 lattice boosts the ferroelectric properties. A polydomain structure is observed on the bare surface of 16% Ta-doped HfO2. Moreover, the switching behavior of the domain is explored by applying an external voltage, demonstrating the potential for storage device applications. [ABSTRACT FROM AUTHOR]

We report a series of measurements of the effect of an electric field on the frequency of the ultranarrow linewidth F 7 0 → D 5 0 optical transition of Eu 3 + ions in an Y 2 SiO 5 matrix at cryogenic temperatures. We provide linear Stark coefficients along two dielectric axes and for the two different substitution sites of the Eu 3 + ions, with an unprecedented accuracy and an upper limit for the quadratic Stark shift. The measurements, which indicate that the electric field sensitivity is a factor of seven larger for site 1 relative to site 2 for a particular direction of the electric field, are of direct interest in the context of both quantum information processing and laser frequency stabilization with rare-earth doped crystals, in which electric fields can be used to engineer experimental protocols by tuning transition frequencies. [ABSTRACT FROM AUTHOR]

The eXciton Franz–Keldysh (XFK) effect is observed in GaN p–n junction diodes via the spectral variation of photocurrent responsivity data that redshift and broaden with increasing reverse bias. Photocurrent spectra are quantitatively fit over a broad photon energy range to an XFK model using only a single fit parameter that determines the line shape and the local bias ( V l ), uniquely determining the local electric field maximum and depletion widths. As expected, the spectrally determined values of V l vary linearly with the applied bias (V) and reveal a large reduction in the local electric field due to electrostatic non-uniformity. The built-in bias ( V b i ) is estimated by extrapolating V l at V = 0 , which, when compared with independent C-V measurements, indicates an overall ±0.31 V accuracy of V l . This demonstrates sub-bandgap photocurrent spectroscopy as a local probe of electric field in wide bandgap diodes that can be used to map out regions of device breakdown (hot spots) for improving electrostatic design of high-voltage devices. [ABSTRACT FROM AUTHOR]

NbO2 is a promising candidate for resistive switching devices due to an insulator-metal transition above room temperature, which is related to a phase transition from a distorted rutile structure to an undistorted one. However, the electrical resistivity of the NbO2 thin films produced so far has been too low to achieve high on-off switching ratios. Here, we report on the structural, electrical, and optical characterization of single-crystalline NbO2 (001) thin films grown by pulsed laser deposition on MgF2 (001) substrates. An annealing step reduced the full width at half maximum of the NbO2 (004) x-ray Bragg reflection by one order of magnitude, while the electrical resistivity of the films increased by two orders of magnitude to about 1 kΩcm at room temperature. Temperature-dependent resistivity measurements of an annealed sample revealed that below 650 K, two deep-level defects with activation energies of 0.25 eV and 0.37 eV dominate the conduction, while above 650 K, intrinsic conduction prevails. Optical characterization by spectroscopic ellipsometry and by absorption measurements with the electric field vector of the incident light perpendicular to the c-axis of the distorted rutile structure indicates the onset of fundamental absorption at about 0.76 eV at room temperature, while at 4 K, the onset shifts to 0.85 eV. These optical transitions are interpreted to take place across the theoretically predicted indirect bandgap of distorted rutile NbO2. [ABSTRACT FROM AUTHOR]

Electric field distribution is critically important for quantitative insights into the physics of nonequilibrium plasma like corona. To analyze the electric field as well as the ion flow (space charge) distribution under DC corona discharges, the ion flow model has been widely adopted; Kaptzov's assumption, which states that the steady state electric field at the conductor surface remains at the corona onset value, serves as a boundary condition. In this Letter, we investigate the electric field distribution under DC corona discharges between coaxial cylindrical electrodes in ambient air by electric field induced second harmonic generation with nanosecond pulse laser beams. The electric field distribution (with or without the corona discharge) is obtained. By comparing the measurements with the results predicted by the ion flow model for the negative corona discharge, it is found that the electric field at the conductor surface is proportional to the current density of the corona discharge with a negative constant of proportionality. Therefore, for negative corona discharges, Kaptzov's assumption is valid only when the discharge current approaches zero or is small. [ABSTRACT FROM AUTHOR]

Sensing electric fields with high sensitivity, high spatial resolution, and at radio frequencies can be challenging to realize. Recently, point defects in silicon carbide have shown their ability to measure local electric fields by optical conversion of their charge state. Here, we report the combination of heterodyne detection with charge-based electric field sensing, solving many of the previous limitations of this technique. Owing to the nonlinear response of the charge conversion to electric fields, the application of a separate "pump" electric field results in a detection sensitivity as low as 1.1 (V / cm) / H z , with a near-diffraction limited spatial resolution and tunable control of the sensor dynamic range. In addition, we show both incoherent and coherent heterodyne detection, allowing measurements of either unknown random fields or synchronized fields with higher sensitivities. Finally, we demonstrate in-plane vector measurements of the electric field by combining orthogonal pump electric fields. Overall, this work establishes charge-based measurements as highly relevant for solid-state defect sensing. [ABSTRACT FROM AUTHOR]

We have measured the ultrafast anisotropic optical response of highly doped graphene to an intense single cycle terahertz pulse. The time profile of the terahertz-induced anisotropy signal at 800 nm has minima and maxima repeating those of the pump terahertz electric field modulus. It grows with increasing carrier density and demonstrates a specific nonlinear dependence on the electric field strength. To describe the signal, we have developed a theoretical model that is based on the energy and momentum balance equations and takes into account optical phonons of graphene and the substrate. According to the theory, the anisotropic response is caused by the displacement of the electronic momentum distribution from zero momentum induced by the pump electric field in combination with polarization dependence of the matrix elements of interband optical transitions. [ABSTRACT FROM AUTHOR]

Electric field sensors based on LiNbO3 are attractive for use in high-intensity transient electric field measurements. However, the working bias of such sensors is easily influenced by temperature variations. Many researchers have worked to improve the thermal stability of the bias of these sensors, mostly in terms of waveguide direction selection and suppression of the pyroelectric effect. In this letter, we present an analysis of the steady-state temperature stability of an x-cut, z-propagation, straight waveguide common-path interferometer-based sensor and show that the difference between the thermo-optic coefficients of no and ne caused by the anisotropy of the LiNbO3 crystal is the main factor that affects the steady-state working bias of the electric field sensor at different working temperatures. The experimental results for the changes in the sensor bias with temperature in the steady states are in good agreement with the theoretical analysis. [ABSTRACT FROM AUTHOR]

X-ray standing waves generated above flat surfaces will modulate local electric field intensity distributions and in turn alter surface scattering patterns. Such an effect is uncovered in the grazing-incidence small-angle x-ray scattering study of the two-dimensional (2D) colloidal superlattices deposited on Si substrates. There are appreciable differences between the scattering patterns of a single particle simulated by the conventional and multislice distorted-wave Born approximation methods. The single-particle scattering effect is much amplified by the periodic arrangement of the 2D hexagonal superlattice, rendering it experimentally detectable. Numerical simulations incorporating the x-ray standing wave modulated surface scattering effect show remarkable agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Rydberg atoms have been shown to be very useful in performing absolute measurements of the magnitude of a radio frequency (RF) field using electromagnetically induced transparency. However, there has been less success in using Rydberg atoms for the measurement of the phase of an RF field. Measuring the phase of a RF field is a necessary component for many important applications, including antenna metrology, communications, and radar. We demonstrate a scheme for measuring the phase of an RF field by using Rydberg atoms as a mixer to down-convert an RF field at 20 GHz to an intermediate frequency on the order of kHz. The phase of the intermediate frequency corresponds directly to the phase of the RF field. We use this approach to measure the phase shift on an electromagnetic wave from a horn antenna as the antenna is placed at different distances from the Rydberg atom sensor. The atom-based RF phase measurements allow us to measure the propagation constant of the RF wave to within 0.1% of the theoretical value. [ABSTRACT FROM AUTHOR]

InAs/InP quantum dots are excellent sources of telecom single-photon emission and are among the most promising candidates for scalable quantum photonic circuits. However, geometric differences in each quantum dot lead to slightly different emission wavelengths and hinder the possibility of generating multiple identical quantum emitters on the same chip. Stark tuning is an efficient technique to overcome this issue as it can control the emission energy of individual quantum dots through the quantum-confined Stark effect. Realizing this technique in InAs/InP quantum dots has previously been limited to shifts of less than 0.8 meV due to jumps in the emission energy because of additional charges at high electric field intensities. We demonstrate up to 5.1 meV of Stark tuning in the emission wavelength of InAs/InP quantum dots. To eliminate undesirable jumps to the charged state, we use a thin oxide insulator to prevent carrier injection from the contacts, thereby significantly improving the tuning range of the Stark effect. Moreover, the single-photon nature and narrow linewidth of the quantum dot emission are preserved under a wide range of applied electric fields. Using photoluminescence intensity measurements and time-resolved lifetime spectroscopy, we confirmed that this Stark tuning range is limited by carrier tunneling at high electric fields. This result is an important step toward integrating multiple identical quantum emitters at telecom wavelengths on a chip, which is crucial for realizing complex quantum photonic circuits for quantum information processing. [ABSTRACT FROM AUTHOR]

An epitaxial lead free ferroelectric 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) thin film is fabricated on a (001)Nb:SrTiO3 single crystalline substrate by the pulsed laser deposition method. The 2.3% lattice mismatch between the BZT-BCT and substrate suggests that the film is grown under a compressively strained state by leaving a large strain gradient near the interface. Polarization versus electric field measurement reveals that the film exhibits a ferroelectric hysteresis character with a large imprint effect indicating the existence of an internal electric field. The origin of the internal electric field is correlated with the strain gradient induced flexoelectric effect and the interfacial built-in field. Consequently, the resultant internal electric field could lead to a self-polarized non-switchable layer at the interface. The evidence for the envisaged self-polarization effect is indeed shown by the piezo force microscopic measurements. Importantly, photovoltaic studies performed on the film display an open circuit voltage of 1.1 V, which is higher than the values reported for many ferroelectric films. The observed photovoltaic response is correlated with the depolarization field and the self-polarization effect. The demonstrated large photo-response illustrates the application potential of the BZT-BCT system in photovoltaic devices. [ABSTRACT FROM AUTHOR]

We report the effect of the epitaxial strain and deliberate incorporation of anionic/cationic defects on the ferroelectric-like response of CaTiO3 thin films. The role of the defect concentration and TiO6 octahedral rotation in the suppression or promotion of a ferroelectric phase is discussed. We demonstrate that a local electric field and/or mechanical force induce the local accumulation/depletion of oxygen vacancies, which change the surface potential and local volume similar to ferroelectric polarization. Our results demonstrate that reversible bi-stable states can be produced in CaTiO3 by electrical or mechanical means, opening interesting possibilities for ionic-based devices. [ABSTRACT FROM AUTHOR]

Band alignment and dipole formation at the hetero-interface still remain fascinating and, hence, are being intensively investigated. In this study, we experimentally investigate the dipole formation by employing a dielectric/dielectric (Al2O3/GeO2) interface. We investigate the dipole dependence on various post-deposition annealing (PDA) ambiences from the viewpoints of electrical extraction and the X-ray photoelectron spectroscopy measurement. The core level shift at the Al2O3/GeO2 interface is consistent with the dipole changes in various PDA ambiences. We discover that the dipole formation can be well explained by the interface gap state and charge neutrality level theory. These results further confirm the feasibility of gap state theory in explaining the band alignment at hetero-junctions. This study can be a booster to enhance the comprehension of dipole origin at hetero-junction interfaces. [ABSTRACT FROM AUTHOR]

Comment on "Electric field measurements under DC corona discharges in ambient air by electric field induced second harmonic generation" [Appl. Phys. Equation (1) is an approximate relation obtained from the ion transport equation coupled with the Poisson equation, and in order to analyze its validity, one should resort to a more accurate theoretical model, comprising these and other relevant equations. It follows that Eq. (1) with the negative ion mobility does not describe correctly the electric field distribution in the region I r i >= 0.2 cm. The latter is indeed the case, as shown in Fig. [Extracted from the article]

Resistive random access memory (RRAM) has attracted significant interest for next-generation nonvolatile memory applications. However, it is somehow difficult to design a high speed RRAM device with enhanced data reliability. This paper deals with the improvement of high speed durable switching in nanocrystals based RRAM (NC-RRAM) devices. The high performance RRAM devices were prepared by incorporating the NCs into the HfOx oxide layer. As compared to the without (w/o) NC devices, the NC-RRAM devices are capable to execute uniform switching with higher set speed of 100 ns and reset speed of 150 ns, longer retention time and higher endurance of 108 cycles at 85 °C. The possible switching mechanism is due to the formation and rupture of the conductive filaments (CFs) inside the oxide film. The improvement of the NC-RRAM devices is due to the enhanced electric field intensity on the surface of the NCs, which can effectively facilitate the formation and rupture of the CFs. [ABSTRACT FROM AUTHOR]

Optical nanoantennas are studied to manipulate light and enhance light matter interactions. Here, we experimentally demonstrate the optical Helmholtz resonance in a metallic slit-box structure, which is predicted to be harmonic and to enhance the electric field intensity by several orders of magnitude. It is fabricated thanks to a two step electron beam lithography process, between which the box was filled with benzocyclobutene (BCB). Up to 80% of the light is absorbed at a λ = 2.84 μm wavelength under a beam focused by a Cassegrain objective (NA = 0.4), even if the dimensions of this resonator are deeply subwavelength for both the slit (width λ/55 and height λ/77) and the box (width λ/7 and height λ/37). As expected from the inductance nature of the box, the optical properties of the BCB filling the box have no influence on the resonance behavior. [ABSTRACT FROM AUTHOR]

We demonstrate theoretically and experimentally a plasmonic metasurface operating as a broadband polarization converter with adequate efficiency which can transform linearly polarized light into its orthogonal polarization in the near-infrared region. The unit cell of the specifically designed metasurfaces is composed of an asymmetric split-ring resonator (SRR) within a square metallic hole. The adequate polarization conversion rate arises from the enhancement of the cross-polarized electric field and the decrease in the co-polarized electric field induced by the symmetry breaking of the SRR. Furthermore, a broad operating frequency range results from the overlap of multiple polarization rotation responses, which are generated in the combined symmetry-breaking SRRs and square metallic holes. This ultrathin single-layer metasurface avoids the complicated fabrication process of multilayered and tridimensional polarization converters and offers more intriguing possibilities to design high-performance plasmonic metasurfaces for polarization modulation. [ABSTRACT FROM AUTHOR]

We examine aluminum-nanodisc-induced collective lattice resonances as a means to enhance the efficiency of organic light emitting diodes. Thus, nanodisc arrays were embedded in the hole transporting layer of a solution-processed phosphorescent organic blue-light emitting diode. Through extinction spectroscopy, we confirm the emergence of array-induced collective lattice resonances within the organic light emitting diode. Through finite-difference time domain simulations, we show that the collective lattice resonances yield an enhancement of the electric field intensity within the emissive layer. The effectiveness for improving the light generation and light outcoupling is demonstrated by electro-optical characterization, realizing a gain in a current efficiency of 35%. [ABSTRACT FROM AUTHOR]

High-quality spatially resolved measurements of electric fields are critical to understanding charge injection, charge transport, and charge trapping in semiconducting materials. Here, we report a variation of frequency-modulated Kelvin probe force microscopy that enables spatially resolved measurements of the electric field. We measure electric field components along multiple directions simultaneously by employing position modulation and lock-in detection in addition to numeric differentiation of the surface potential. We demonstrate the technique by recording linescans of the in-plane electric field vector in the vicinity of a patch of trapped charge in a 2,7-diphenyl[1]benzothieno[ 3,2-b][1]benzothiophene (DPh-BTBT) organic field-effect transistor. This technique is simple to implement and should be especially useful for studying electric fields in spatially inhomogeneous samples like organic transistors and photovoltaic blends. [ABSTRACT FROM AUTHOR]

In this study, the electrocaloric effect (ECE) of Bi0.5Na0.5TiO3-0.06BaTiO3 (BNT-0.06BT) ceramic has been directly measured using a home-made adiabatic calorimeter. The maximum adiabatic temperature change (ΔT) approaches 0.86K under an electric field of 5 kV/mm at 110 ²C, which provides experimental evidence for optimizing the ECE near the type-I pseudo-first-order phase transition (PFOPT). Most importantly, a considerable ΔT value can be maintained over a wide temperature range well above the temperature of the PFOPT under a high electric field. In addition, ΔT is closely related to the structural transition and electric field strength. This work provides a guideline to investigate the high ECE in BNT-based ferroelectric ceramics for applications in cooling technologies. [ABSTRACT FROM AUTHOR]

To investigate the effects of defects and field enhancement in diamond power devices, a biased Schottky barrier diode was characterized by electron-beam-induced current (EBIC) analysis. The nonuniform distribution of the electrical field was revealed by bright spots on the laterally expanded depletion layer of the EBIC intensity map when the applied electrical field exceeded 0.95 MV/cm. The nonuniformity is partly due to a structural effect: the roughness at the edge of the Schottky electrode, induced by lithography and lift-off processes. A second family of spots was shown to increase the leakage current of the device. The time constant associated with this second spot family was 0.98 ms, which is three orders of magnitude shorter than that for defects previously characterized by deep-level transient spectroscopy. [ABSTRACT FROM AUTHOR]

Aqueous and nanoparticle-based solutions have been reported to heat when exposed to an alternating radiofrequency (RF) electric-field. Although the theoretical models have been developed to accurately model such a behavior given the solution composition as well as the geometrical constraints of the sample holder, these models have not been investigated across a wide-range of solutions where the dielectric properties differ, especially with regard to the real permittivity. In this work, we investigate the RF heating properties of non-aqueous solutions composed of ethanol, propylene glycol, and glycine betaine with and without varying amounts of NaCl and LiCl. This allowed us to modulate the real permittivity across the range 25-132, as well as the imaginary permittivity across the range 37-177. Our results are in excellent agreement with the previously developed theoretical models. We have shown that different materials generate unique RF heating curves that differ from the standard aqueous heating curves. The theoretical model previously described is robust and accounts for the RF heating behavior of materials with a variety of dielectric properties, which may provide applications in non-invasive RF cancer hyperthermia. [ABSTRACT FROM AUTHOR]

We investigated the tunneling electroresistance (TER) in metal/wurtzite-MgZnO/metal junctions for applications in nonvolatile random-access memories. A resistive switching was detected utilizing an electric-field cooling at ±1V and exhibited a TER ratio of 360%-490% at 2K. The extracted change in the average barrier height between the two resistance states gave an estimation of the MgZnO electric polarization at 2.5μC/cm2 for the low-temperature limit. In addition, the temperature-dependent TER ratio and the shift of the localized states energies at the barrier interface supported the ferroelectric behavior of the MgZnO tunnel-barrier. From the first-principles calculations, we found a similar effect of the barrier height change coming from the reversal of ZnO electric polarization. The possibility of using metal electrodes and lower growth temperatures, in addition to the ferroelectric property, make the ZnO-based memory devices suitable for CMOS integration. [ABSTRACT FROM AUTHOR]

In this letter, we report the photoinduced effect modulated by different electric fields in the Pr0.65 (Ca0.75Sr0.25)0.35MnO3/0.7PbMg1/3Nb2/3O3-0.3PbTiO3 heterostructure. The film exhibits a decrease in the resistance up to five orders of magnitude by enhancing applied electric fields, combined with an electric-field-induced insulator-to-metal transition. More interestingly, a reversible bistability arises in the photoinduced change in resistance at T<80K as the voltages are increased. The results can be attributed to the phase separation in manganites, which provides a prototype of photoelectric conversion for electric-field modulation of all-oxide heterostructures. [ABSTRACT FROM AUTHOR]

We synthesized zirconium oxynitride from yttria-stabilized zirconia (YSZ) in air by applying DC electric fields that produced a controlled electric current in the specimen. When YSZ was heated under an applied DC electric field, the electric current of the specimen steeply increased at a critical temperature, called a flash event, during flash sintering. By keeping the electric current of the specimen constant during the flash event and then holding the specimen at the critical temperature, YSZ was transformed into zirconium oxynitride under the optimal conditions of 50 V/cm, 500 mA, and 1000 °C. We confirmed that zirconium oxynitride formed using high-resolution transmission electron microscopy, electron energy-loss spectroscopy, and energy-dispersive spectrometry. To convert oxides to nitrides, reducing conditions are necessary to form excess oxygen vacancies. Our technique produced the strong reducing conditions necessary to form nitrides from the oxides by delivering a controlled electric current to the specimen. [ABSTRACT FROM AUTHOR]

We report on the temperature dependence of the magnetic anisotropy in Co/Pd/MgO system, in which magnetic moment in Pd is induced by the magnetic proximity effect. We demonstrate that the magnetic anisotropy is modulated by applying an electric field to the Pd surface. At temperatures below 100K, we find the nonlinear electric-field dependence of the anisotropy with the sign reversal. We obtain a huge anisotropy modulation efficiency of ∼1600 fJ/V m at 10K. [ABSTRACT FROM AUTHOR]

This paper offers a theoretical explanation of the temperature and temporal dependencies of transient dark count rates (DCRs) measured for a linear-mode silicon avalanche photodiode (APD) and the dependencies of afterpulsing that were measured in Geiger-mode Si and InGaAs/InP APDs. The temporal dependencies exhibit power-law behavior, at least to some extent. For the transient DCR, the value of the DCR for a given time period increases with decreases in temperature, while the power-law behavior remains unchanged. The transient DCR is attributed to electron emissions from traps in the multiplication layer of the APD with a high electric field, and its temporal dependence is explained by a continuous change in the electron emission rate as a function of the electric field strength. The electron emission rate is calculated using a quantum model for phonon-assisted tunnel emission. We applied the theory to the temporal dependence of afterpulsing that was measured for Si and InGaAs/InP APDs. The power-law temporal dependence is attributed to the power-law function of the electron emission rate from the traps as a function of their position across the p-n junction of the APD. Deviations from the power-law temporal dependence can be derived from the upper and lower limits of the electric field strength. [ABSTRACT FROM AUTHOR]

A general modelling methodology has been developed to evaluate the effects of chemical interdiffusion and misfit dislocations on the performance of heterojunction solar cells made from highly mismatched materials. Results for the exemplar materials system CdS-CdTe are contrary to the widely held belief that such interdiffusion is beneficial to photovoltaic performance. In the model, recombination is presumed to take place at the cores of misfit dislocations, with the distribution of these dislocations in the interdiffused layer being calculated so as to minimise the total energy (an incidental result shows that the total number of dislocations is independent of the diffusion profile). The model takes calculated chemical profiles, optical absorption, and dislocation distributions from which the photovoltaic performance and recombination losses are evaluated. It was shown that for the realistic case in which the interdiffused region does not extend beyond the space charge region, the photovoltage losses dominate over any photocurrent gains. Methods to engineer mixed junctions that may increase solar conversion efficiency are discussed. [ABSTRACT FROM AUTHOR]

The control of magnetic Skyrmions confined in a nanometer scale disk using electric field pulses is studied by micromagnetic simulation. A stable Skyrmion can be created and annihilated by an electric field pulse depending on the polarity of the electric field. Moreover, the core direction of the Skyrmion can be switched using the same electric field pulses. Such creation and annihilation of Skyrmions, and its core switching do not require any magnetic field and precise control of the pulse length. This unconventional manipulation of magnetic texture using electric field pulses allows a robust way of controlling magnetic Skyrmions in nanodiscs, a path toward building ultralow power memory devices. [ABSTRACT FROM AUTHOR]

The epitaxial growth of FeSi film on (001) 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (PMN-0.32PT) was fabricated by sputtering and confirmed by high-resolution transmission electron microscopy. A fourfold symmetric angular remanent magnetization curve of as-deposited FeSi thin film is well fitted theoretically by considering the cubic magnetocrystalline anisotropy. We found that the fourfold anisotropy decreases slightly when an electric field (E) is applied on the Pt/PMN-0.32PT/FeSi/Ta heterostructures with Pt layer as the positive electrode. However, a magnetic anisotropy transition from fourfold anisotropy to twofold anisotropy occurs under negative E. The strain-electric field curve suggests that the observed different variation trend of magnetic anisotropy results from the asymmetric strain response on the polarity of E. Moreover, once the transition happens, it was irreversible unless the heterostructures are heated above the phase transition temperature of PMN-0.32PT. [ABSTRACT FROM AUTHOR]

The electrical properties of chemical vapour deposited p-type epitaxial diamond layers are studied in high electric field conditions. The quasi-static current-voltage characteristics have been measured using transmission-line pulse method with 100 ns pulses. Reproducible impurity impact ionization avalanche breakdown occurs at a critical electrical field in the range of 100-200 kV cm-1 depending on the acceptor concentration and temperature, leading to complete ionisation of neutral impurities. The current-voltage characteristics exhibit an S-shape with the bi-stable conduction characteristic of impurity impact ionisation. [ABSTRACT FROM AUTHOR]

We report on electronic transport measurements through a silicon double quantum dot consisting of a donor and a quantum dot. Transport spectra show resonant tunneling peaks involving different valley states, which illustrate the valley splitting in a quantum dot on a Si/SiO2 interface. The detailed gate bias dependence of double dot transport allows a first direct observation of the valley splitting in the quantum dot, which is controllable between 160 and 240 μeV with an electric field dependence 1.2 ± 0.2 meV/(MV/m). A large valley splitting is an essential requirement for implementing a physical electron spin qubit in a silicon quantum dot. [ABSTRACT FROM AUTHOR]

We systematically investigate the spatial/temporal photocurrent in photodetectors and electronic transport in transistors/Hall-bar devices based on monolayer MoS2 grown by chemical vapor deposition (CVD). We found that the maximum photocurrent occurs when the laser spot is close to the metal/MoS2 contact and is tunable by the applied drain voltage, which can be explained by the modulation of the local electric field at the Schottky barrier, consistent with predictions from our quantum transport simulation. We observed that the maximum photocurrent at drain contact is much larger than the one at the source contact, and the DC currents show rectifying behavior. These phenomena can be explained by the different Schottky barrier heights at the two contacts. By measuring Hall-bar structure at various temperatures from 100K to 400 K, we extracted the barrier heights at the source and drain contacts, separately. We found that the barrier height at drain contact is about 50mV larger than the one at the source contact, consistent with the photocurrent and DC current observations. We measured the photocurrent at various powers, and a photoresponsivity of 3.07mA/W was extracted at low powers. When the power increases above 20 µW, the photocurrent starts to saturate. Temporal response of the photocurrent is also dependent on the laser power. At high laser powers, photocurrent overshoot was observed. The photocurrent saturation at high powers and the overshoot in temporal photocurrent are likely due to the same mechanism: an accumulation of electrons in the channel, flattening out the band structure, since the laser spot is located near the drain contact in these measurements. These studies of photocurrents and electronic transport in CVD MoS2 highlight the importance of the contacts in the electronic/optoelectronic devices and reveal the physical mechanism of the photocurrent/electronic transport in these devices. [ABSTRACT FROM AUTHOR]

The electrocaloric effect has been investigated in antiferroelectric (Pb, La)(Zr, Sn, Ti)O3 (PLZST) single crystals grown by the flux method. The measurements of polarization versus electric field loops on unpoled crystals revealed that at room temperature, a critical electric field of 1.8 kV/mm is needed to induce a ferroelectric phase from an antiferroelectric phase. The dielectric properties demonstrated that the induced ferroelectric phase recovers to antiferroelectric phase when temperature is above the depolarization temperature (70 °C–100 °C). Coexistence of the negative and positive electrocaloric effect has been achieved in 〈001〉-oriented PLZST single crystals. Multiple electrocaloric response values of –0.054 °C at room temperature, 0.17 °C near the depolarization temperature, –0.14 °C at 125 °C, and 0.75 °C around Curie temperature have been observed under an electric field of 3 kV/mm. The coexistence of multiple negative and positive electrocaloric effects in one material provides a possibility to design solid-state refrigerator technologies to enhance the electrocaloric efficiency. [ABSTRACT FROM AUTHOR]

First principles calculations are used to explore the structural and electronic properties of black phosphorus/blue phosphorus (black-p/blue-p) van der Waals (vdW) p-n heterostructure. An intrinsic type-II band alignment with a direct band gap at Γ point is demonstrated. The spatial separation of the lowest energy electron-hole pairs can be realized and make black-p/blue-p heterostructure a good candidate for applications in optoelectronics. Black-p/blue-p heterostructure exhibits modulation of its band gap and band edges by applied perpendicular electric field (E⊥). This system undergoes a transition from semiconductor to metal when subjected to a strong external E⊥. The variation of band edges and quasi-Fermi level as a function of E⊥ provides further insight to the linear variation of the band gap. Our calculation results pave the way for experimental research and indicate the great application potential of black-p/blue-p vdW heterostructure in future optoelectronics. [ABSTRACT FROM AUTHOR]

Accurate three dimensional reconstructions of atomic positions and full quantification of the information contained in atom probe microscopy data rely on understanding the physical processes taking place during field evaporation of atoms from needle-shaped specimens. However, the modeling framework for atom probe microscopy has only limited quantitative justification. Building on the continuum field models previously developed, we introduce a more physical approach with the selection of evaporation events based on density functional theory calculations. This model reproduces key features observed experimentally in terms of sequence of evaporation, evaporation maps, and depth resolution, and provides insights into the physical limit for spatial resolution. [ABSTRACT FROM AUTHOR]

Transient atomic displacements during a resonant thickness-shear vibration of AT-cut α-quartz are revealed by time-resolved X-ray diffraction under an alternating electric field. The lattice strain resonantly amplified by the alternating electric field is ~104 times larger than that induced by a static electric field. The resonantly amplified lattice strain is achieved by fast displacements of oxygen anions and collateral resilient deformation of Si-O-Si angles bridging rigid SiO4 tetrahedra, which efficiently transduce electric energy into elastic energy. [ABSTRACT FROM AUTHOR]

Surface plasmon resonances (SPRs) on ZnO:Ga layer surfaces (ZnO-SPR) enhanced absorptionbands related to molecular-vibrations (OH and CH3 modes) in the near-infrared range by controllinglayer thickness. These behaviors were due to the interaction between SPR excitations andmolecular vibrations. Further investigation revealed that the high detection sensitivity of SPRson ZnO:Ga layer surfaces was 6837 nm/RIU using water and methanol mixtures. The detectionregion of ZnO-SPR was limited within several hundred nanometers from the layer surfaces, which is discussed relative to theoretical analysis of field distributions and spatial coherence ofSPRs on ZnO:Ga layer surfaces. [ABSTRACT FROM AUTHOR]

We report the simultaneous excitation of the odd and the even eigenmode resonances in a periodic array of square split-ring resonators, with four resonators per unit cell. When the electric field is parallel to their gaps, only the two well-studied odd eigenmodes are excited. As the resonators are rotated relative to one another, we observe the emergence and excitation of an extremely sharp even eigenmode. In uncoupled split-ring resonators, this even eigenmode is typically radiative in nature with a broad resonance linewidth and low Q-factor. However, in our coupled system, for specific range of rotation angles, our simulations revealed a remarkably high quality factor (Q ~ 100) for this eigenmode, which has sub-radiant characteristics. This type of quad-supercell metamaterial offers the advantage of enabling access to all the three distinct resonance features of the split-ring resonator, which consists of two odd eigenmodes in addition to the high-Q even eigenmode, which could be exploited for high performance multiband filters and absorbers. The high Q even eigenmode could find applications in designing label free bio-sensors and for studying the enhanced light matter interaction effects. [ABSTRACT FROM AUTHOR]

The electrical field-induced changes of the yeast Saccharomyces cerevisiae cells permeabilization to tetraphenylphosphonium (TPP+) ions were studied using square-shaped, nanosecond duration high power electrical pulses. It was obtained that pulses having durations ranging from 10 ns to 60 ns, and generating electric field strengths up to 190 kV/cm significantly (up to 65 times) increase the absorption rate of TPP+ ions without any detectible influence on the yeast cell viability. The modelling of the TPP+ absorption process using a second order rate equation demonstrates that depending on the duration of the pulses, yeast cell clusters of different sizes are homogeniously permeabilized. It was concluded, that nanosecond pulse-induced permeabilization can be applied to increase the operational speed of whole cell biosensors. [ABSTRACT FROM AUTHOR]

A numerical investigation on the third-order nonlinear optical properties of a plasmonic system composed by metal film-coupled nanowires is reported. The linear and nonlinear optical characteristics are studied by finite-difference time-domain (FDTD) method. To substantially improve the nonlinear effect, the geometric parameters of the system are carefully engineered to excite strong plasmon gap resonance with dramatically enhanced electric field intensity at the gap between the nanowires and the film. The third-harmonic generation (THG) property is examined by nonlinear FDTD simulation. It shows that the THG efficiency estimated from the nonlinear optical absorption can be ~1X10-5 under an incident power density of 5.2GW/cm². Plasmonic resonance is necessary to achieve highly efficient THG since the system on resonance shows the THG intensity 4 orders of magnitude higher than that of an off-resonance system. [ABSTRACT FROM AUTHOR]

We present a technique for measuring radio-frequency (RF) electric field strengths with sub-wavelength resolution. We use Rydberg states of rubidium atoms to probe the RF field. The RF field causes an energy splitting of the Rydberg states via the Autler-Townes effect, and we detect the splitting via electromagnetically induced transparency (EIT). We use this technique to measure the electric field distribution inside a glass cylinder with applied RF fields at 17.04 GHz and 104.77 GHz. We achieve a spatial resolution of ≈100 μm, limited by the widths of the laser beams utilized for the EIT spectroscopy. We numerically simulate the fields in the glass cylinder and find good agreement with the measured fields. Our results suggest that this technique could be applied to image fields on a small spatial scale over a large range of frequencies, up into the sub-terahertz regime. [ABSTRACT FROM AUTHOR]

In order to develop wide-band noise absorbers with a focused design for low frequency performance, this study investigates hybrid absorbers that are composed of conductive indium-tin-oxide (ITO) thin film and magnetic composite sheets. The ITO films prepared via reactive sputtering exhibit a typical value of electrical resistivity of ...10-4 ... m. Rubber composites with flaky Fe-Si-Al particles are used as the magnetic sheet with a high permeability and high permittivity. For the ITO film with a low surface resistance and covered by the magnetic sheet, approximately 90% power absorption can be obtained at 1GHz, which is significantly higher than that of the original magnetic sheet or ITO film. The high power absorption of the hybrid absorber is attributed to the enhanced ohmic loss of the ITO film through increased electric field strength bounded by the upper magnetic composite sheet. However, for the reverse layering sequence of the ITO film, the electric field experienced by ITO film is very weak due to the electromagnetic shielding by the under layer of magnetic sheet, which does not result in enhanced power absorption. [ABSTRACT FROM AUTHOR]

This paper describes design and simulations of dielectric laser electron accelerators that achieve Gigavolt-per-meter (GV/m) accelerating gradients and wide electron channels (>1 μm). The accelerator design is based on a silicon buried grating structure that enables flexible phase synchronization, large electron channel fields, and low standing-wave ratio in the material. This design increases the accelerating gradients to more than double those of reported quartz grating accelerators, thereby reducing the input laser fluence by 60% for the same accelerating gradient. With a 100 fs pulsed laser, our silicon buried gratings can achieve a maximum gradient of 1.1 GV/m, indicating that these accelerators have potential for numerous electron-accelerator applications. [ABSTRACT FROM AUTHOR]