Charge Measurement Technique Research Articles

Quantitative determination of fractional topological charge based on the rotational Doppler effect

The utilization of fractional-order vortex beams extends the diversity of optical field manipulation, permits for more flexible control over beam propagation, and provides novel applications in optical communications, edge enhancement imaging, and particle manipulation. However, compared with the integer-order vortex beams, the topological charge measurement techniques for fractional-order vortex beams are not well developed, impeding the further exploration of its applications. In this paper, the frequency signal of rotational Doppler effect and corresponding broadening behavior under the fractional-order vortex beam illumination were analyzed. When the fractional topological charge approaches a half integer, the broadening is minimized. Leveraging this relationship, we designed a phase-compensated scheme coupled with signal-to-noise ratio detection to realize the real-time fractional topological charge measurement. The single pixel photodetector was used and eliminated the need for two-dimensional image acquisition and analysis, ensuring efficient acquisition and quantitative analysis. Both theoretical and experimental results confirm the feasibility of this method, thereby advancing the comprehension of the optical Doppler effect and potentially paving the way for future investigations into fractional vortex beams.

Space charge measurements for multilayer heterogeneous composite films by thermal pulse method

Multilayer composite films are suitable for high-temperature and high-electric-field insulation, but the accumulation of space charge may lead to the degradation of their insulating properties. However, few studies have been reported on space charge distribution in multilayer composite thin films due to the limitations of space charge measurement techniques. In this study, using Al2O3/PI and BOPP/PI composite structural samples as numerical examples, we proposed a method for calibrating electric fields in multilayer heterogeneous structures and combined it with the Tikhonov regularization algorithm, and successfully reconstructed the electric field distribution inside the samples. Based on this, the experimental results show that the reconstruction of the overall electric field in the BOPP/PI composite samples is consistent with the combined electric field reconstructed after the individual measurements of each layer, which further confirms the feasibility and validity of the use of thermal pulse to measure the charge distribution in multilayer heterogeneous composite films.

Space Charge Behavior in Epoxy‐Based Dielectrics: Progress and Perspective

AbstractEpoxy‐based dielectrics are extensively used in grid‐connected energy systems and modern microelectronics as electrical insulation, adhesive, and packaging components. However, space charge accumulation in epoxy‐based dielectrics is a foremost factor threatening device stability and lifespan, especially under conditions of high voltage direct current and high temperatures during long‐term operation, and thus are investigated systematically. This article reviews the state‐of‐the‐art progress in understanding and regulating the space charge behavior of epoxy‐based dielectric materials. The development of space charge measurement techniques is first introduced. Then, experimental observations of macroscopic space charge characteristics in epoxy dielectrics under different conditions, along with the advancement of nanofiller‐doping strategies for improving space charge suppression capabilities, are discussed and emphasized. Afterward, simulation progress based on the bipolar charge transport models and quantum chemistry calculations are summarized to provide some insight from a microscopic perspective. It is concluded by providing a brief summary and highlighting future research opportunities in inhibiting space charge accumulation of epoxy‐based dielectrics for practical applications in power equipment and electronic devices.

Progress in Gas/Solid Interface Charging Phenomena

Surface charge accumulation in the spacer modifies local electric fields, which restricts the industrialization of high voltage direct current (HVDC) gas-insulated transmission lines (GILs). In this paper, the state of art in gas/solid interface charging physics and models, covering areas of charge measurement techniques, charge transport mechanisms, charge related DC surface flashover models, and charge control methods, is reviewed and discussed. Key issues that should be considered in future studies are summarized and proposed. The purpose of this work is to provide a brief update on the most important and latest progress in this research area, and to educate readers as to the current state of the gas-solid interface charging phenomenon, which has seen great progress in the past few years.

Gas–solid interface charge characterisation techniques for HVDC GIS/GIL insulators

Surface charge accumulation on the spacers is one of the key issues restraining the development of HVDC GIS/GIL. The precise measurement of surface charge properties provides the basis for further study of the surface charge transport mechanism as well as the charge-induced flashover mechanism under DC voltage. In this study, the authors discuss their perspective on the current status, development needs and potential developing orientation of surface charge characterisation techniques. Different surface potential measurement methods and charge inversion algorithms are reviewed regarding the previous studies and future research needs. Drawbacks and outlooks of surface charge measurement techniques are also discussed with the background of laboratory experiment results and on-site measurements. It is hopefully that this study can serve as a useful guide reference for researchers within the same research field. More importantly, it is authors’ hope that this study can inspire some novel ideas for readers into developing of more accurate and scientific interface charge characterisation techniques.

Numerical simulation of the space charge accumulation inside solid insulation subjected to special polarization conditions

The insulation of high-power electronic equipment faces special electrical stresses such as square and pulse waves, but the numerical research on space charge inside the insulation under such conditions is still in the blank at present. Based on the traditional bipolar charge transport model, it is indicated that the polarization conditions with changing polarities require that the solving algorithms of the model should be selected according to the electric field direction inside the sample grid. The charge phenomena under different sample parameters and polarization conditions in the power frequency range are further simulated. It is concluded that both the total charge amounts under unipolar and bipolar conditions are affected by the polarization power, and the charge migration depth is within 20 μm. For the sample parameters, it is found that the accumulated charge amount under two types of polar polarization conditions is obviously reduced as the value of injection barrier or extraction coefficient increases. And the trapping and detrapping parameters have a greater influence under unipolar conditions. Therefore, it is necessary to select appropriate modified parameters according to the actual operating conditions when controlling the insulating performance. As for the polarization condition, it is found that the charge amount at high frequencies is unaffected by the frequency value, and a phenomenon that positive and negative charges simultaneously accumulate can be found under all the bipolar conditions with a frequency of 0.01 Hz. In addition, the simulation also indicates that the charge measurement technique needs to have a sufficiently high spatial resolution under these conditions, and the required time to measure the steady charge is relatively shorter under bipolar conditions.

The charge of wettable illite-smectite surfaces measured with the O-D method

Abstract The aim of the present study was to test the applicability of the O-D method, a newly developed spectroscopic layer charge measurement technique, to measure the charge present on wettable surfaces of mixed-layer illite-smectite (I-S). The O-D method employs the exact position of the sharp, high frequency O-D stretching band of adsorbed D2O at 2685–2700 cm−1, which was found to correlate linearly with the layer charge for dioctahedral smectites. The O-D method has therefore potential to measure the charge present on the wettable surfaces of I-S crystallites, i.e. surfaces of smectite monolayers and external surfaces of illite fundamental particles. The O-D method was found to be applicable to mixed-layer I-S. The I-S' surface charge was measured for 41 well-documented I-S samples coming from bentonites and hydrothermal deposits, and representing smectite contents between 8 and 100%. The measured charge averaged 0.47 ± 0.03 e− per formula unit and was very narrowly distributed irrespectively of smectite content or sample origin. Such a result is close to earlier estimates based on chemical analyses. It was concluded that the O-D method measures only the surface charge of fundamental particles, without the influence of the illitic charge from the K-occupied interlayer. No difference in the surface charge among samples with and without smectite monolayers was observed, which is in agreement with the polar model of illite fundamental particles and confirms the smectitic nature of their basal surfaces. On the other hand, a systematic increase of surface charge upon decreasing fraction size was noticed for ultrafine fractions. This trend suggests a low polarity of illite fundamental particles at the initial stages of nucleation.

Novel Concept of Gas Sensitivity Characterization of Materials Suited for Implementation in FET-Based Gas Sensors.

We propose a novel technique to investigate the gas sensitivity of materials for implementation in field-effect transistor-based gas sensors. Our technique is based on the measurement of the surface charge induced by gas species adsorption, using an electrometer. Platinum sensitivity to hydrogen diluted in synthetic air has been evaluated with the proposed charge measurement technique in the operation temperature range from 80 to 190 °C at constant H2 concentration of 4 % and for different concentrations ranging from 0.5 to 4 % at 130 °C.

Quantifying the intrinsic surface charge density and charge-transfer resistance of the graphene-solution interface through bias-free low-level charge measurement

Liquid-based bio-applications of graphene require a quantitative understanding of the graphene-liquid interface, with the surface charge density of adsorbed ions, the interfacial charge transfer resistance, and the interfacial charge noise being of particular importance. We quantified these properties through measurements of the zero-bias Faradaic charge-transfer between graphene electrodes and aqueous solutions of varying ionic strength using a reproducible, low-noise, minimally perturbative charge measurement technique. The measurements indicated that the adsorbed ions had a negative surface charge density of approximately −32.8 mC m−2 and that the specific charge transfer resistance was 6.5 ± 0.3 MΩ cm2. The normalized current noise power spectral density for all ionic concentrations tested collapsed onto a 1/fα characteristic with α = 1.1 ± 0.2. All the results are in excellent agreement with predictions of the theory for the graphene-solution interface. This minimally perturbative method for monitoring charge-transfer at the sub-pC scale exhibits low noise and ultra-low power consumption (∼fW), making it suitable for use in low-level bioelectronics in liquid environments.

Atomic force microscopy developments for probing space charge at sub-micrometer scale in thin dielectric films

Charge injection and accumulation in dielectrics are phenomena at the origin of different kind of failure of devices. To improve the understanding of involved mechanisms, space charge measurement techniques have been successfully developed. However, their spatial resolution is incompatible with thin films or interfaces studies. In this paper, the contribution of techniques derived from Atomic Force Microscopy (AFM) to space charge measurement is investigated. First of all, localized charges injection is studied using classical Kelvin Force Microscopy (KFM). Secondly, we propose a new method called EFDC (Electrostatic Force Distance Curve) which allows direct measurement of electrostatic force induced by trapped charges. EFDC sensitivity to lateral localization of charges is demonstrated. Finally, comparing the results obtained by EFDC and KFM highlights the relative merit of each technique.

Implementation of Faraday cup electrostatic charge measurement technique in high-pressure gas–solid fluidized beds at pilot-scale

Elevation of operating pressure in gas–solid fluidized beds affects the bed hydrodynamics, which in turn could affect the extent of bed electrification and reactor wall coating due to electrostatic charge generation. In this work, a pilot plant high-pressure gas–solid fluidization system housing the Faraday cup electrostatic charge measurement technique is introduced in order to study the underlying mechanism of electrostatic charge generation causing fluidized bed wall fouling at pressures up to 25barg. A previously developed on-line electrostatic charge measurement technique containing two Faraday cups was successfully implemented in the high-pressure system. The effect of operating pressure on gas–solid fluidized bed electrification was examined under operating pressures of 0 and 25bar (gauge) by fluidizing polyethylene resin directly received from a commercial reactor. Experimental results showed that the magnitude of reactor wall coating increased with the increase of operating pressure. The wall coating contained positively as well as negatively charged particles indicating the occurrence of bipolar charging within the fluidized bed. Finally, based on the experimental results obtained in this work the mechanism of fluidized bed column wall coating formation was discussed.

Impact of Addition of a Catalyst or Its Support on Reactor Wall Coating Due to Electrostatic Charging during Fluidization of Polyethylene

In this work the degree of fluidized bed electrification and reactor wall coating were investigated where a metallocene catalyst and its silica support were added to a bed of polyethylene resin and fluidized in a carbon steel reactor, 0.1 m in diameter and operating under ambient conditions. Tests were conducted to simulate industrial polyethylene reactors where both polyethylene and catalyst particles are present during the fluidization process. Since majority of the catalyst surface area is occupied by its support, the influence of the support was also examined. The electrostatic charge measurement technique used was similar to that described by Sowinski et al.1 Results demonstrated that both the catalyst and the silica support augmented the fluidized bed reactor wall coating due to their inherent large specific charge, which was partly gained during their passage through the injection tube. This finding demonstrates the possibility that in commercial gas-phase polyethylene fluidized bed reactors the ca...

(Invited) Defect Generation Mechanism and Its Impact on Reliability Properties in MONOS Devices

The interface-state generation mechanism and its impact on reliability properties, such as endurance and data retention, in MONOS devices have been studied. The charge measurement technique we developed has demonstrated that holes injected during erasing are the main cause of interface-state generation. From carrier separation measurement for MONOS devices, we have found the data retention degradation after P/E stress is owing to the increased hole injection from Si substrate via the generated interface states. We also discuss the physical origin of the interface states in MONOS devices and report on MONOS-specific interface-state generation/recovery phenomena, and their significant impact on endurance and retention properties.

Defect Generation Mechanism and Its Impact on Reliability Properties in MONOS Devices

Introduction Metal-oxide-nitride-oxide-semiconductor (MONOS) device attracts much attention owing to its potential as future nonvolatile memory devices. For the use of MONOS devices, it is important to understand accurately the mechanism of reliability degradation induced by electrical stress such as programming and erasing. In this paper, we discuss the defects-generation mechanisms by using evaluation technique that we developed. We also show how the defects generation influences to reliability properties of the MONOS devices. Interface-State Generation by Program/Erase Cycling Program/Erase (P/E) cycle stress generates defects in MONOS devices and degrades their performance and reliability. Since it has been recognized for the MONOS devices that the degradation is mainly due to interface-state generation, we examined the mechanism of interface-state generation in the MONOS devices under P/E stress by using a charge measurement technique we developed. The amount of interface states (ΔNit) is found to have a strong correlation with charges flowing during erasing, irrespective of pulse voltage, pulse width and number of P/E cycles. It is further demonstrated that the ΔNit increases as hole current dominates in erasing, suggesting that hole injection from Si substrate during erasing is the main cause for the ΔNit. Data Retention Degradation Caused by Stress Induced Hole Current Data retention measurements after P/E cycle stress were carried out with applying gate voltage to control the direction of electron leakage during retention. As a result, higher charge loss was observed when applying negative gate voltage during retention, indicating that P/E stress-induced leakage current (SILC) across the tunnel oxide layer degrades the data retention.To detect the SILC directly, we performed carrier separation I-V measurement for p-channel MONOS devices. The tail of electron detrapping current at low voltage (electron SILC) was, however, observed only for the MONOS with highly Si-rich SiN charge trapping layer. Thus, a mechanism other than the electron SILC must be involved in the data retention degradation for the MONOS devices. The carrier separation measurements further demonstrated that hole current injected into the MONOS devices is increased after P/E cycle stress, indicating the existence of “hole SILC”. The hole SILC is found to be determined by the ΔNit regardless of MONOS structure, suggesting that the hole SILC is attributable to the generated interface states. These results suggest a mechanism for the data retention degradation caused by P/E cycle stress: The P/E cycle stress damages tunnel oxide layer and generates the ΔNit. The hole SILC is injected via the ΔNit, degrading data retention through hole trapping and possible subsequent recombination with stored electrons. Impact of Interface-State Recovery on Reliability Properties It is well known, in the research field of MOS reliability, that accumulated holes attack Si-H bonds at the Si/SiO2 interface and induce negative bias temperature instability (NBTI). Since the ΔNit in the MONOS devices is generated by holes accumulated in Si substrate, it is speculated that physical origin of the ΔNit is similar to that in MOS devices, that is, Si-H bond dissociation. The Reaction-Diffusion (R-D) model, which explains well the NBTI mechanism, suggests that hydrogen released by the Si-H dissociation diffuses back to the interface and passivates the generated interface states after removal of electrical stress. It was observed for the MONOS devices that the ΔNit was found to be decreased after 200ºC 1h baking, demonstrating that the ΔNit is due to dissociation of Si-H bonds. Since the recovery accompanies the threshold voltage shift, suppression of the ΔNit is important for data retention property as well as for endurance property. Conclusions We have investigated the mechanisms for interface-state generation by P/E cycle stress, and demonstrated that holes injected from Si substrate is the main cause for the ΔNit. It is also found that the hole SILC is injected via the ΔNit, degrading data retention property through hole trapping and possible subsequent recombination with stored electrons. Since the physical origin of the ΔNit is Si-H bond breakage, a part of released hydrogen diffuses back to the interface and passivates the ΔNit, leading to the degradation of data retention property.

Interface State in Metal–Oxide–Nitride–Silicon Memories Induced by Hole Injection during Program/Erase Cycle Stress

The mechanism of interface-state generation in metal–oxide–nitride–silicon (MONOS) memories by program/erase (P/E) cycling was experimentally examined, using the charge measurement technique we developed that allows direct measurement of the amount of charges flowing during P/E operation. The amount of interface state was found to have a strong correlation with the amount of charges flowing during erase operation, irrespective of pulse voltage, pulse width and number of P/E cycles. It was also found that the amount of interface states generated by P/E cycling increases as hole fluence dominates erase operation. These findings suggest that hole injection from Si substrate, rather than electron detrapping from SiN layer or impact-ionized hot hole, is the main cause of the interface-state generation.

Interface State in Metal–Oxide–Nitride–Silicon Memories Induced by Hole Injection during Program/Erase Cycle Stress

The mechanism of interface-state generation in metal–oxide–nitride–silicon (MONOS) memories by program/erase (P/E) cycling was experimentally examined, using the charge measurement technique we developed that allows direct measurement of the amount of charges flowing during P/E operation. The amount of interface state was found to have a strong correlation with the amount of charges flowing during erase operation, irrespective of pulse voltage, pulse width and number of P/E cycles. It was also found that the amount of interface states generated by P/E cycling increases as hole fluence dominates erase operation. These findings suggest that hole injection from Si substrate, rather than electron detrapping from SiN layer or impact-ionized hot hole, is the main cause of the interface-state generation.

Effect of fluidizing particle size on electrostatic charge generation and reactor wall fouling in gas–solid fluidized beds

Electrostatic charge generation from particle–particle and particle–wall contacts in gas–solid fluidized beds is virtually unavoidable and generally undesired. Charged particles are known to cause problems including particle agglomeration and particle–reactor wall adhesion. The polymerization industry has been plagued by reactor wall fouling for many years, but the actual mechanism behind this problem is not well understood. The wide particle size distribution present in polyolefin fluidized bed reactors is believed to play an important role. This work studied the effect of particle size of a polyethylene resin received directly from industrial reactors on electrostatic charge generation and reactor wall fouling. The resin was sieved into five different narrowed particle size fractions and fluidized at two different gas velocities; 1.5 and 4 times the minimum fluidization velocity (umf) representing the bubbling and the slugging flow regimes. The fluidization was performed in a 0.1m carbon steel fluidization column with the charge measurement technique described by Sowinski et al. (2010). In the bubbling flow regime significant particle wall adhesion was found for particles sizes up to 600μm, after which very little reactor wall fouling was observed. In the slugging flow regime, there was significant particle wall adhesion for all particle size fractions tested with the exception of the 600–710μm range, which at times resulted in significant particle–wall adhesion and in other times none was obtained. Overall, it was found that the smaller particles had a higher charge and resulted in more reactor wall fouling. With the non-sieved resin, the particles that adhered to the column wall were approximately of the same size as the smallest size fraction tested (300–425μm). This study found that the measurement of the net charge-to-mass ratio inside a fluidized bed is not an indication of the amount of reactor wall fouling.

Decoherence-free spin entanglement generation and purification in nanowire double quantum dots

We propose a deterministic generation and purification of decoherence-free spin entangled states with singlet-triplet spins in nanowire double quantum dots via resonator-assisted charge manipulation and measurement techniques. Each spin qubit corresponds to two electrons in a double quantum dot in the nanowire, with the singlet and one of the triplets as the decoherence-free qubit states. The logical qubits are immunized against the dominant source of decoherence-dephasing—while the influences of additional errors are shown by numerical simulations. We analyse the performance and stability of all required operations and emphasize that all techniques are feasible in current experimental conditions.

New experimental system for the study of the effect of temperature and liquid to solid transition on streamers in dielectric liquids: application to cyclohexane

An experimental setup for dielectric testing of insulating liquids in the temperature range from -60 °C to +250 °C has been built. The system uses point-plane geometry, a sensitive differential charge measurement technique, a computer controlled temperature regulator, a photomultiplier and a pulse generator with a fast rise time. This paper presents a detailed overview of the functionality of the system and results obtained in cyclohexane under positive and negative polarity below and above freezing point. Pre-inception current, inception probabilities, streamer charge and emitted light from streamers are reported. The results found in cyclohexane at room temperature compares well to results obtained in other similar setups. A temperature dependence on the injected streamer charge for liquid cyclohexane under positive polarity was observed. No polarity differences were observed for any of the measured quantities in frozen cyclohexane.

Effects of Electron-attaching and eEectron-releasing Additives on Streamers in Liquid Cyclohexane

The effects of electron-attaching and electron-releasing additives in cyclohexane on the initiation and propagation of positive and negative streamers have been studied quantitatively. Fast impulses (<20 ns, <40 kV) were applied on a 10 mm point-to-plane gap and studied by shadowgraphic imaging and a differential charge measurement technique. The properties of both positive and negative streamers depend on the specific electronic characteristic of the additives. Electron-attaching additives facilitate the propagation of negative streamers, whereas the most effective electron-releasing additives reduce initiation voltages and facilitate the propagation of positive streamers. Depending on the reactivity and concentration of the additives, streamer filaments become thinner and fewer while propagating faster and further. The Townsend-Meek theory for streamer inception in gases has been adapted to a solution and applied to analyze the voltage dependence of the positive streamer propagation. Results show a quantitative dependency on the ionization potential and concentration in agreement with experimental trends.