Charge Evolution Research Articles

Impact of Program/Erase Cycling Interval on the Transconductance Distribution of NAND Flash Memory Devices

This study comprehensively investigates the impact of the time interval (t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wait</sub> ) between program/erase (P/E) cycles on the oxide quality of NAND Flash memory devices. It is observed that, at room temperature, P/E cycles with a shorter t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wait</sub> yield a better oxide quality than those with a longer t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wait</sub> . The oxide charge (Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ) evolution by distributed P/E cycles can be well described by an analytical equation through the extension of our previous statistical transconductance reduction (G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m,max</sub> ) method. This equation is characterized by a power of the number of P/E cycles multiplied by an exponential decay term of t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wait</sub> . The former term is related to the Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> generation, whereas the latter is related to the Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> emission during t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wait</sub> between cycles. This model allows to evaluate the activation energy for both Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> generation (E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A,G</sub> ) and recovery (E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A,R</sub> ). E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A,G</sub> is revealed to be a function of the logarithmic scale of t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wait</sub> , decreasing from 100 to 85 meV for t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wait</sub> varying from 0.1 to 4 s. Moreover, E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A,R</sub> is approximately 0.4 eV, which is consistent with the value of electron thermal emission from traps in SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> .

Phase-field model of topological charge interaction force in nematic liquid crystals

ABSTRACT Nematic liquid crystals (LCs) normally contain both integer and half-integer topological charges. In this work, we investigate topological charge evolution dynamics in nematic LCs by the phase-field model. We observe the annihilation of the topological charge, and the total number of charges decreases to two cores with time evolution in a disk. A significant decrease in charges is observed during the initial evolution. The positive topological charge and negative topological charge annihilate depending on the distance between two charges, which can be treated as the interaction force. The form of interaction force is similar to Coulomb’s law, but the force is inversely the distance of defects instead of the square of the distance in Coulomb’s law. Therefore, the present study contributes to the understanding of topological charge evolution dynamics and provides guidance for experiments to design in nematic LCs.

Manipulating light radiation from a topological perspective

Manipulating radiation is important for a variety of optoelectronic applications, such as on-chip lasers, energy-efficient grating couplers, and antennas for light detection and ranging. Although designing and optimizing those optoelectronic devices are usually believed to be an engineering-oriented task, recent research reveals that the principles underlying radiation manipulation are closely connected to the concept of topology—the study of properties that are invariant under continuous deformations. In this review, we summarize a series of advances of the physics, phenomena, and applications related to radiation manipulation, in which topological concepts were adopted. Radiation could carry energy escaping from the system, breaking the energy conservation. The non-Hermiticity of such systems brings quite different physical consequences when comparing with the Hermitian counterparts and, hence, also results in the emergence of many interesting and extraordinary phenomena. In particular, it is found that the perfect trapping of light can still be realized in such non-Hermitian systems because of the photonic realization of bound states in the continuum. The fundamental nature of bound states in the continuum has been identified to be topological: they are essentially topological defects of the polarization vector field in momentum space, depicted by a kind of topological invariant named topological charges. Therefore, manipulation of radiation channels can be realized by controlling the topological charge evolution in momentum space. It is also demonstrated that the photonic states accompanied with different topological charges generate vortex beams with unique far-field radiation patterns, and ultra-fast switching of such vortex beams is demonstrated according to this principle. The progresses of topological photonics upon light radiation show that the topology is not just mathematical convenience for depicting photonic systems, but has brought realistic consequences in manipulating light and will boost the applications of photonics and optoelectronics in many aspects.

Visualizing topological transport

We present a mathematically simple procedure for explaining and visualizing the dynamics of quantized transport in topological insulators. The procedure serves to illustrate and clarify the dynamics of topological transport in general, but for the sake of concreteness, it is phrased here in terms of electron transport in a charge-ordered chain, which may be mapped exactly onto transport between edge channels in the Integer Quantum Hall Effect. This approach has the advantage that it allows a direct visualization of the real-space and real-time evolution of the electronic charges throughout the topological pumping cycle, thus demystifying how charge flows between remote edges separated by an insulating bulk, why the amount of transported charge is given by a topological invariant, and how continuous driving yields a discrete, quantized amount of transported charge.

High-Sensitive Refractive Index Sensing Enabled by Topological Charge Evolution

A high-sensitive refractive index sensor is proposed and demonstrated by utilizing merging bound states in the continuum, namely a set of integer topological charges in the momentum space. Through varying cladding refractive index nc, the topological charges continuously depart from the merging state, and result in the robust and considerable high-Q factors (above 7 × 10 4 ) in a large detection range of 0.456. In such a range, sensing sensitivity of ~36 nm/RIU and figure-of-merit from ~5990 (air) to 1607 (n c = 1.456) are achieved. Meanwhile, the detection limit on the order of 10 -5 RIU is clearly distinguishable from the measured spectrum under tiny variation of cladding refractive index. Our work paves the way for promising integrated high-sensitive sensors in many biological and chemical applications.

Investigating the flow induced corrosion of copper in chloride-containing solution at the atomistic scale

Metal aqueous corrosion is a common electrochemical phenomenon. Nonetheless, the metal corrosion simulations at the atomistic scale have not been well-established yet. In this study, several copper corrosion cases in aqueous solution with chloride ions are studied with molecular dynamics, especially the flow induced corrosion is studied for the first time to the best of our knowledge. The copper corrosion in two kinds of solutions, which are HCl and chloride ions solutions, are simulated with pre-developed reactive force field (ReaxFF) method. Here, particles diffusion, bonding among elements, and charge evolution are analyzed to understand the mechanisms of the cases. It is found that the electrolyte flowing and initial Cu surface can accelerate the corrosion process, illustrated by higher mean-squared displacement (MSD) and Cu average charge. Moreover, the initial rough surface has different effects for different electrolyte concentrations. This work may provide important references for fundamental understanding the mechanisms of copper corrosion in chloride-containing solutions at nanosized scale.

Tumor microenvironment-activated self-charge-generable metallosupramolecular polymer nanocapsules for photoacoustic imaging-guided targeted synergistic photothermal-chemotherapy

An integrated nanosystem of target, visualization, high circulation stability, and multi-therapy effects represents the leading direction of next generation anti-cancer strategy. Nevertheless, this normally requires elegant multi-component and hierarchical structure design of nanomaterials, or even a complicated post-treatment procedure, to combine different functions together. Herein, we show that hollow metallosupramolecular polymer nanoparticles (HMPNs) derived from a selective-etching approach based on Kirkendall effect have combined capabilities of (i) facile in-situ guest cargo encapsulation, (ii) reversible surface charge evolution, (iii) excellent photoacoustic property and (vi) highly synergistic photothermal-chemo therapeutic effect. Using DOX as a model drug, we can easily fabricate DOX-HMPNs because the etching process is accompanied with effective matter exchange between outer environment and inner particle, while significantly avoiding the premature drug leakage. Notably, synergistic effect between reversible phenolic hydroxyl ionization and dynamic catechol-FeIII coordination endows DOX-HMPNs with dramatic self-charge generation ability, thus achieving weakly acidic tumor microenvironment-activated reversible surface charge evolution. We have found that DOX-HMPNs with this self-charge generation feature can effectively achieve prolonged circulation and tumor recognition. Moreover, the cleavage of imine bond can induce the disassembly of hollow particles in strongly acidic lysosomes, and thus accelerate the release of DOX. This chemotherapy, in combination with the cascade-responsive behavior and photothermal/photoacoustic properties of HMPNs, makes our DOX-HMPNs exhibit synergistic antitumor efficiency and provide promising potential for cancer theranostic application.

Airport charges and marginal costs for Spanish airports before the process of partial privatization

Airport pricing is considered as one of the most relevant issues for policymakers. According transport policy, pricing schemes should be at least partially based on marginal costs. This article aims at comparing the most relevant aeronautical airport charges with their corresponding marginal costs for the Spanish airports in the period before the partial privatization process. To that end, we have built very detailed airport charge variables, and then, have estimated a flexible short-run variable cost function system using a panel of thirty-five airports over a 6-year period. The results show that the evolution of aeronautical airport charges does not follow the trend of marginal costs. Moreover, these charges are set above the short-run marginal costs with the exception of the smallest and insular airports. Finally, we find the existence of non-neutral technological change and excess of capacity for the Spanish airports.

Chiral magnetic effect in isobar collisions from stochastic hydrodynamics * * Supported by International Program for Ph.D Candidates, Sun Yat-Sen University, the National Science Foundation (PHY-1913729), the National Natural Science Foundation of China (11675274, 11735007), the Shang- hai Pujiang Program (19PJ1401400)

We studied the chiral magnetic effect in AuAu, RuRu, and ZrZr collisions at . The axial charge evolution was modeled with stochastic hydrodynamics, and geometrical quantities were calculated with the Monte Carlo Glauber model. By adjusting the relaxation time of the magnetic field, we found our results are in good agreement with background subtracted data for AuAu collisions at the same energy. We also made predictions for RuRu and ZrZr collisions. We found a weak centrality dependence on initial chiral imbalance, which implies that the centrality dependence of chiral magnetic effect signals results mainly from the effects of the magnetic field and volume factor. Furthermore, our results show an unexpected dependence on system size. While the AuAu system has larger chiral imbalance and magnetic field, it was observed to have a smaller signal for the chiral magnetic effect due to the larger volume suppression factor.

Probing Heterogeneous Charge Distributions at the α-Al2O3(0001)/H2O Interface.

Unlike metal or semiconductor electrodes, the surface charge resulting from the protonation or deprotonation of insulating mineral oxides is highly localized and heterogeneous in nature. In this work the Stark active C≡N stretch of potassium thiocyanate is used as a molecular probe of the heterogeneity of the interfacial electrostatic potential at the α-Al2O3(0001)/H2O interface. Vibrational sum frequency generation (vSFG) measurements performed in the OH stretching region suggest that thiocyanate species organize interfacial water similarly to halide ions. Changes in the electrostatic potential are then tracked via Stark shifts of the vibrational frequency of the thiocyanate stretch. Our vSFG measurements show that we can simultaneously measure the vSFG response of SCN- ions experiencing charged and neutral surface sites. We assign local potentials of +308 and -154 mV to positively and negatively charged aluminol groups that are present at pH = 4 and pH = 10, respectively. Thiocyanate anions at positively charged surface sites and negatively charged surface sites and those participating in contact ion pairing adopt similar orientations and are oppositely oriented relative to thiocyanate ions near neutral surface sites. All four species followed Langmuir adsorption isotherms. Density functional theory-molecular dynamics (DFT-MD) simulations of SCN- near the neutral α-Al2O3(0001)/H2O interface show that the vSFG response in the C≡N stretch region originates from a SCN-H-O-Al complex, suggesting the surface site specificity of these experiments. To our knowledge this is the first spectroscopic measurement of local potentials associated with a heterogeneously charged surface. The ability to probe the evolution of local charges in situ could provide vital insight into many industrial, electrochemical, and geochemically relevant interfaces.

Effects of charged interfaces on electrolyte decomposition at the lithium metal anode

Lithium–Sulfur batteries are promising candidates to substitute conventional Li-ion batteries due to their higher energy density and reduced cost. However, several challenges related to the reactivity of the lithium metal anode have prevented this technology from becoming broadly commercialized. Lithium's high reactive nature leads to the continuous decomposition of the electrolyte and the formation of the solid-electrolyte interphase (SEI) layer. Thus, a comprehensive understanding of how the SEI film is formed is crucial to help elucidate improvements for this battery technology. In this work, we use density functional theory (DFT) based computational methods to investigate the effect of charged interfaces on the electrolyte degradation at the lithium anode. Several electrolyte mixtures were considered including 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) as solvents, and lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as salts. It is found that the extent of salt decomposition is higher when the interface is charged. In addition, two types of solvent reduction mechanisms are identified: C–O bond cleavage and radical attacks. Charge transfer and evolution analysis are characterized in detail. Finally, solvent decomposition reactions are found to become more thermodynamically favorable and their activation barriers to be diminished under the effect of constant potentials and electric fields.

Understanding the Long-Term Evolution of Electric Taxi Networks

Due to the ever-growing concerns over air pollution and energy security, more and more cities have started to replace their conventional taxi fleets with electric ones. Even though environmentally friendly, the rapid promotion of electric taxis raises problems to both taxi drivers and governments, e.g., prolonged waiting/charging time, unbalanced utilization of charging infrastructures, and inadequate taxi supply due to the long charging time. In this article, we conduct the first longitudinal measurement study to understand the long-term evolution of mobility and charging patterns by utilizing 5-year data from one of the largest electric taxi networks in the world, i.e., the Shenzhen electric taxi network in China. In particular, (1) we first perform an electric taxi contextualization about their operation and charging activities; (2) then we design a generic charging event extraction algorithm based on GPS data and charging station data, and (3) based on the contextualization and extracted charging activities, we perform a comprehensive measurement study called ePat to explore the evolution of the electric taxi network from the mobility and charging perspectives. Our ePat is based on 4.8 TB taxi GPS data, 240 GB taxi transaction data, and metadata from 117 charging stations, during an evolution process from 427 electric taxis in 2013 to 13,178 in 2018. Moreover, ePat also explores the impacts of various contexts and benefits during the evolution process. Our ePat as a comprehensive measurement of the electric taxi network mobility and charging evolution has the potential to advance the understanding of the evolution patterns of electric taxi networks and pave the way for analyzing future shared autonomous vehicles.

Analytical model for homocharge accumulation in LDPE — role of conduction, injection and diffusion

Homocharge, particularly, positive charge near anode has been observed inside low-density polyethylene (LDPE) by many researchers. However, the phenomenon is yet to be understood theoretically and mathematical analysis is pending, although, simulations have been reported. Simulation of evolution of space charge in LDPE, with time and space, using bipolar charge transport model considered only drift component of charge carriers inside the dielectric. The experimental results suggest significant concentration gradient in space charge distribution. The authors derived a comprehensive drift and diffusion based analytical models, for the time/space evolution of space charge and electric field in dielectrics using Maxwell's equations, current continuity equation, conduction and injection mechanisms. The proposed analytic models of electric field and space charge distribution entwines charge injection at electrodes and charge transport inside the medium, which seem to have not been reported until now. Remarkable, believed to be unprecedented, agreement between the analytical and experimental results has been observed. Using the model, the role of conduction, injection, diffusion on homocharge accumulation has been investigated. Pulsed electroacoustic method is used for the measurements of the space charge dynamics.

Oxide charge evolution under crystallization of amorphous Li–Nb–O films

Li–Nb–O amorphous films were deposited onto Si substrates by the radio-frequency magnetron sputtering method in an Ar environment and an Ar(60%)+O 2 (40%) gas mixture. A positive effective fixed oxide charge Q eff having negative, -Q eff , and positive, +Q eff , components, exists in the as-grown heterostructures. -Q eff is located near the substrate/film interface, whereas + Q eff is determined by a deficit of Li and O (vacancies) in the bulk of Li–Nb–O films. As-grown films crystallized under thermal annealing (TA) at temperatures up to 600 °C and revealed the formation of polycrystalline LiNbO 3 . TA at about 520 °C resulted in the formation of the second phase LiNb 3 O 8 , increasing + Q eff , and compensating -Q eff entirely. The dielectric constants of the as-grown films exhibit two peaks at the annealing temperatures of 450 °C and 550 °C, which are attributed to the total crystallization and recrystallization of the LN films under TA, respectively.

Multi-particle momentum correlations extracted using covariance methods on multiple-ionization of diiodomethane molecules by soft-X-ray free-electron laser pulses.

Momenta of ions from diiodomethane molecules after multiple ionization by soft-X-ray free-electron-laser pulses are measured. Correlations between the ion momenta are extracted by covariance methods formulated for the use in multiparticle momentum-resolved ion time-of-flight spectroscopy. Femtosecond dynamics of the dissociating multiply charged diiodomethane cations is discussed and interpreted by using simulations based on a classical Coulomb explosion model including charge evolution.

Charge injection into the Ni-phyllosilicate nanoscrolls with reduced Ni nanoparticles using Kelvin force probe microscopy

The evolution of the electrical charge injected into Ni-doped phyllosilicate nanoscrolls composites deposited on a conductive substrate was studied by Kelvin probe force microscopy. The nanoscrolls were synthesized by hydrothermal method and then annealed in H2/Ar flow at 400-900°C in order to reduce Ni up to metal. A typical agglomerate of the Ni3Si2O5(OH)4 nanoscrolls accumulated the charge on one nanoscroll followed by a subsequent partial destruction of the agglomerate. For the Ni2MgSi2O5(OH)4 nanoscrolls, the whole agglomerate could be charged, and the injected charge was retained for hours. The shortest charge relaxation time was revealed for the nanoscrolls annealed at the highest temperature, when Ni was completely reduced.

Diffusive Representation and Sliding Mode Control of Charge Trapping in Al$_2$O$_3$ MOS Capacitors

The objective of this paper is to introduce a modeling strategy to characterize the dynamics of the charge trapped in the dielectric of MOS capacitors, using diffusive representation. Experimental corroboration is presented with MOS capacitors made of Alumina in three different scenarios. First, the model predictions are compared with the trapped charge evolution due to arbitrary voltage excitations. Second, the predictions are compared with the measurements of a device in which a sigma-delta control of trapped charge is implemented. Finally, the time evolution when the device is simultaneously controlled and irradiated with X-rays is compared with the predictions. In all cases, a good matching between the models and the measurements is obtained.

Thermal response properties and surface insulation failure mechanism of epoxy resin under arc ablation

Arc ablation during the operation of HVDC circuit breakers can cause irreversible damage to the epoxy resin (EP) insulation pull rod. This is one of the critical factors that affect the reliability and lifetime of a HVDC circuit breaker. In this work, we built an arc ablation experimental platform and studied the thermal response properties of EP insulation under arc ablation. The surface charge evolution characteristics and the dielectric properties were analyzed to reveal the underlying surface insulation failure mechanism of EP after arc ablation. The results indicate that arc ablation can cause severe carbonization to EP insulation. With increasing arc duration, the EP gradually transforms into carbide and pore products. Arc ablation can decrease the molecular moment orientation polarizability and the relative dielectric constant of EP insulation, and thereby increasing the current density formed by Schottky injection. Therefore, when the external electric field is applied, the charge on EP insulation surface migrates from high voltage electrode to the ablating area, causing the regional accumulation of surface charge and the formation of local failure area. This can decrease the surface electrical performance of EP insulation and lead to insulation failure finally.

Internal Charging Issues Met During Electric Orbit Raising and in GPS-Like MEO Environment

This paper was dedicated to the experimental characterization and numerical assessment of the possible risk of charging during the electric orbit raising (EOR). Different elements [printed circuit board (PCB), ethylene tetrafluoroethylene wires (ETFE)] considered at risk in representative electron environment have been tested to assess their charging behavior and any risks of electrostatic discharges in this environment. This task has been performed in the GEODUR irradiation test facility installed at Office National d’Etudes et de Recherches Aerospatiales (Toulouse, France) and equipped with a 2.5-MeV electron accelerator. The samples have been irradiated with an electron spectrum representative of the maximum spectrum (in regard of electron flux) met during the EOR behind 1-mm shielding. This experimental study revealed high charging kinetics on the different elements over successive cycles that led to the initiation of several electrostatic discharges on PCB, located on metallic floating parts. This paper demonstrated the risk of high charging and electrostatic discharge (ESD) risks during EOR on sensitive components. These discharges could affect the electronics operation and damage the insulators. The final step of this paper was to perform numerical simulation for internal charging assessment in global positioning system (GPS)-type orbit on different space used materials with a dedicated tool that takes into account the temporal evolution of high energy electron fluxes. Then we demonstrated a strong evolution of internal charging with the radiation environment, which has been ascribed to the influence of radiation-induced conductivity (RIC). Strong discrepancies from one material to the other have been observed later on the temporal evolution of the surface potential.

Transient Characteristics of Charging Effects due to E-Beam Irradiation: A Method of SEY-Based Charging Balance Mode

Charging effects of dielectric due to space electron beam irradiation have a huge impact on spacecraft. To understand charging equilibrium characteristics of dielectric under electron beam irradiation, in this paper, we present a novel numerical simulation method for analyzing the secondary electron yield (SEY) based on a charging balance mode. We used the Mott scattering model and the Penn dielectric function (PDF) model to calculate the collisions between incident electrons and material the atoms of material. For internal charge transport, we considered the processes of drift, diffusion, trapping, and neutralization. These were calculated with a finite-difference time-domain (FDTD) method. Based on mechanisms of import–export dynamic charge evolution, charging balance can be categorized into three modes: SE mode, leakage (LE) mode, and cooperation (CO) mode (a combination of the two). In most situations, the SE mode corresponds to the surface charging state, while the LE mode always corresponds to deep charging states. Shortening the distance of free charge transport, a thinner sample is more likely to present as LE mode. Although the surface potential can be enhanced by monotonously increasing the thickness, the total internal charge quantity approaches a local maximum with thickness because of a charging balance mode transformation. In addition, with a larger average density of carriers in the LE mode, the material conductivity is enhanced and the dielectric loss tends to be larger at low frequencies (<103 Hz). The charging balance mode method in this study can also be appropriate to the analyses of altering irradiation parameters and materials intrinsic parameters.