Concentric Electrodes Research Articles

Plasma potential shaping using end-electrodes in the Large Plasma Device

We perform experiments in the Large Plasma Device at the University of California, Los Angeles, studying how different end-electrode biasing schemes modify the radial potential profile in the machine. We impose biasing profiles of different polarities and gradient signs on a set of five concentric electrodes placed 12 m downstream from the plasma source. We find that imposing concave-down profiles (negative potential radial gradient) on the electrodes creates radial potential profiles halfway up the plasma column that are comparable to those imposed on the electrodes and a few electron temperature in height, regardless of the biasing polarity. On the other hand, imposing concave-up profiles (positive potential radial gradient) leads to non-monotonic radial potential profiles. This observation can be explained by the current drawn through the electrodes and the parallel plasma resistivity, highlighting their important role in controlling the rotation of plasma. Concave-down plasma potential profiles, obtained by drawing electrons on the axis, are predicted to drive azimuthal drift velocities that can approach significant fractions of the ion sound speed in the central region of the plasma column.

Flow Characteristics and Heat Transfer Enhancement of Electro-Thermo-Convection in Dielectric Liquids With Residual Conductivity

Abstract The flow features and heat transfer enhancement of electro-thermo-convection (ETC) in dielectric liquids with residual conductivity between concentric electrodes are numerically studied based on an injection–conduction model. The strongly coupled flow field, electric field, and positive/negative charge density of the ETC system are solved numerically based on the finite volume framework of OpenFOAM®. The total variation-diminishing algorithm is adopted to handle the complex nonlinearity of the positive/negative charge transport equations. The bifurcation of plentiful flow states that are characterized by variable plumes and vortex pairs in the ETC system is investigated. It is discovered that the residual conductivity postpones the beginning of ETC flow, inhibits the convection intensity, and also diminishes heat transfer of the ETC system. In addition, the transition sequences of ETC flow are also influenced by residual conductivity. A higher residual conductivity suppresses the occurrence of different intermediate steady-states. Three different transition sequences of steady ETC states at different Rayleigh numbers (Ra) are identified. The critical point where the ETC flow bifurcates to S8 is postponed at higher Ra. And the ETC system is more prone to chaos in a system of higher Ra. The periodicity of the ETC system is analyzed and found that Ra has little influence on the periodicity.

Scalp surface Laplacian potential monitoring system based on novel hydrogel active tri-polar concentric ring electrodes

Electroencephalography is valued in brain research for its high temporal resolution and user-friendly nature. However, limitations in spatial resolution and susceptibility to biological artifacts restrict its broader application. The surface Laplacian potential obtained through tri-polar concentric ring electrodes offers a solution by mitigating biological artifact interference and enhancing spatial resolution while preserving essential information. In this study, an active tri-polar concentric ring electrode based on conductive hydrogel and a 3-lead surface Laplacian potential monitoring system designed for use with the electrode were proposed. The part of the electrode that came into contact with the human body was the hydrogel with high electrical conductivity. The contact surface curvature was designed based on the real forehead curvature of 22 subjects, resulting in a normalized electrode-skin contact impedance of 30.95±16.76KΩ*cm2 at 10 Hz, which was lower than commercial disposable wet electrodes and remained stable over a 10-hour period of long-term wear. And the electrode still exhibited excellent performance after being left for 20 days. Additionally, the internal noise of the system was about 1.9μV, which was comparable to that of the FDA-approved equipment. The signal analysis results demonstrated that the surface Laplacian potential collected by the proposed electrode and system had better signal-to-noise ratio and spatial resolution, and had a good suppression effect on biological artifacts.

On the Machinability and Formation of Gas Film Thickness in ECDM of Silica based Pyrex Glass

Electrochemical discharge machining (ECDM) stands out as a preferred method for microfluidic channel fabrication due to its ability to produce required shapes with the least thermal damage along with close tolerances and dimensional accuracy. Recently, there has been significant progress made in the domain of ECDM for parametric analysis, focusing on discharge regime characteristics, but precise control of the hydrodynamic regime remains a challenge. With this view, the present study has been targeted on analyzing the effect of various auxiliary electrodes on the formation of gas film thickness and discharge energy during the fabrication of microchannels using ECDM on silica-based Pyrex glass under varying conditions. Experiments were conducted on an ECDM setup to achieve near damage-free edges of microchannels on the surface silica-based Pyrex glass. Results show the effect of various auxiliary electrodes, applied voltage, and electrolyte concentration on gas film thickness, spark energy, rate of material removal (MRR), and width of overcut (WOC). The optimum parametric level of applied voltage, electrolyte concentration, and auxiliary electrode were 68 V, 35 wt%, and A2 auxiliary electrode, respectively and the best response values were 0.4134 mg min−1, and 40 μm, respectively, for MRR and WOC. In addition, tool wear rate, heat affected zone, and surface morphology of fabricated microchannels was examined using scanning electron microscopy, optical microscope, and energy-dispersive X-ray spectroscopy.

The effect of the electrodes shape in water electrolysis on the production of hydrogen

This article presents a comparative study of the production of hydrogen by the electrolysis of water using two forms of electrodes; cylindrical and flat. The objective of this comparison is to select the best type of electrolyzer to produce hydrogen for the same volume of water and the same operating voltage. An analytical study and experimental tests were carried out on a cylindrical electrolyser consisting of two concentric cylindrical electrodes separated by a variable thickness e (3.5 mm, 4 mm, 5.5 mm, 8.5 mm and 9 mm), then a flat electrolyser consisting of two flat electrodes spaced by a distance d (2 mm, 4 mm, 6 mm, 10 mm and 15 mm). For each cylindrical electrolyser there corresponds a single electrolyser with flat electrodes. The preliminary study revealed that the production of hydrogen in an electrolyzer is significantly affected by the distance separating the two electrodes and their shapes. Indeed, the comparative electrolysis results show that in each case the electrolyzer with cylindrical electrodes clearly prevails over its counterpart with flat electrodes for the same operating conditions and for the same quantity of water injected into the electrolysis.

Пьезоэлектрический дисковый актюатор кручения с дискретно-спиральными электродами

A mathematical model of a disk (ring) torsion actuator with curvilinear interdigital electrodes – «villi» of a spiral form, which are characterized by a constant value of the orientation angle of an arbitrary section of the villus to the circumferential direction of the disk, has been developed. Bases of electrode-villi interacting with each other through local areas of piezoelectric layer are connected with periodic alternation to central or peripheral concentric circular base electrodes, to outputs of which control voltages are connected. As a result of numerical modeling of the «twisting bimorph» graphs of the dependence of the twist angle and the blocking torque on the ratio of the inner and outer radii and the values of the control voltage at the outputs of the base electrodes of the annular two-layer actuator with symmetrical (relative to the radial line) directions of the spiral orientations of the electrode-villi and, as a result, the spiral polarization lines of the piezoelectric layers working for tension/compression.

Posttraumatic headache: pain related evoked potentials (PREP) and conditioned pain modulation (CPM) to assess the pain modulatory function

Posttraumatic headache (PTH) is common following traumatic brain injury and impacts quality of life. We investigated descending pain modulation as one possible mechanism for PTH and correlated it to clinical measures. Pain-related evoked potentials (PREP) were recorded in 26 PTH-patients and 20 controls after electrical stimulation at the right hand and forehead with concentric surface electrodes. Conditioned pain modulation (CPM) was assessed using painful cutaneous electric stimulation (PCES) on the right hand as test stimulus and immersion of the left hand into 10 °C-cold water bath as conditioning stimulus based on changes in pain intensity and in amplitudes of PCES-evoked potentials. All participants completed questionnaires assessing depression, anxiety, and pain catastrophising. PTH-patients reported significantly higher pain ratings during PREP-recording in both areas despite similar stimulus intensity at pain threshold. N1P1-amplitudes during PREP and CPM-assessment were lower in patients in both areas, but statistically significant only on the hand. Both, PREP-N1-latencies and CPM-effects (based on the N1P1-amplitudes and pain ratings) were similar in both groups. Patients showed significantly higher ratings for anxiety and depression, which did not correlate with the CPM-effect. Our results indicate generalized hyperalgesia for electrical stimuli in both hand and face in PTH. The lacking correlation between pain ratings and EEG parameters indicates different mechanisms of pain perception and nociception.

Conductive Hydrogel Tapes for Tripolar EEG: A Promising Solution to Paste-Related Challenges.

Electroencephalography (EEG) remains pivotal in neuroscience for its non-invasive exploration of brain activity, yet traditional electrodes are plagued with artifacts and the application of conductive paste poses practical challenges. Tripolar concentric ring electrode (TCRE) sensors used for EEG (tEEG) attenuate artifacts automatically, improving the signal quality. Hydrogel tapes offer a promising alternative to conductive paste, providing mess-free application and reliable electrode-skin contact in locations without hair. Since the electrodes of the TCRE sensors are only 1.0 mm apart, the impedance of the skin-to-electrode impedance-matching medium is critical. This study evaluates four hydrogel tapes' efficacies in EEG electrode application, comparing impedance and alpha wave characteristics. Healthy adult participants underwent tEEG recordings using different tapes. The results highlight varying impedances and successful alpha wave detection despite increased tape-induced impedance. MATLAB's EEGLab facilitated signal processing. This study underscores hydrogel tapes' potential as a convenient and effective alternative to traditional paste, enriching tEEG research methodologies. Two of the conductive hydrogel tapes had significantly higher alpha wave power than the other tapes, but were never significantly lower.

Conductive block copolymer elastomers and psychophysical thresholding for accurate haptic effects.

Electrotactile stimulus is a form of sensory substitution in which an electrical signal is perceived as a mechanical sensation. The electrotactile effect could, in principle, recapitulate a range of tactile experience by selective activation of nerve endings. However, the method has been plagued by inconsistency, galvanic reactions, pain and desensitization, and unwanted stimulation of nontactile nerves. Here, we describe how a soft conductive block copolymer, a stretchable layout, and concentric electrodes, along with psychophysical thresholding, can circumvent these shortcomings. These purpose-designed materials, device layouts, and calibration techniques make it possible to generate accurate and reproducible sensations across a cohort of 10 human participants and to do so at ultralow currents (≥6 microamperes) without pain or desensitization. This material, form factor, and psychophysical approach could be useful for haptic devices and as a tool for activation of the peripheral nervous system.

First operation of a multi-channel Q-Pix prototype: measuring transverse electron diffusion in a gas time projection chamber

We report measurements of the transverse diffusion of electrons in P-10 gas (90% Ar, 10% CH4) in a laboratory-scale time projection chamber (TPC) utilizing a novel pixelated signal capture and digitization technique known as Q-Pix. The Q-Pix method incorporates a precision switched integrating transimpedance amplifier whose output is compared to a threshold voltage. Upon reaching the threshold, a comparator sends a 'reset' signal, initiating a discharge of the integrating capacitor. The time difference between successive resets is inversely proportional to the average current at the pixel in that time interval, and the number of resets is directly proportional to the total collected charge. We developed a 16-channel Q-Pix prototype fabricated from commercial off-the-shelf components and coupled them to 16 concentric annular anode electrodes to measure the spatial extent of the electron swarm that reaches the anode after drifting through the uniform field of the TPC. The swarm is produced at a gold photocathode using pulsed UV light. The measured transverse diffusion agrees with simulations in PyBoltz across a range of operating pressures (200–1500 Torr). These results demonstrate that a Q-Pix readout can successfully reconstruct the ionization topology in a TPC.

Current opinion on laryngeal electromyography

PurposeThis study evaluates expert opinion on laryngeal electromyography (LEMG). MethodsA cross-sectional design was used to conduct an online survey of LEMG experts in 2021. They were questioned about the number LEMG performed annually, type of electrodes used, sector worked in, pain during the test, placement of the needle electrodes, interpretation of electrical muscle parameters, diagnosis of neuromuscular injury, prognostic sensitivity in vocal fold paralysis (VFP), laryngeal dystonia, tremor and synkinesis and quantifying LEMG. ResultsThirty-seven professionals answered (23 Spanish and 14 from other countries), with a response rate of 21.56%. All physicians used LEMG. 91.9% had one- or two-years’ experience and 56.8% performed 10–40 LEMG per year. 70.3% were otolaryngologists and 27%, neurologists. In 89.1% of cases, a team of electrodiagnostic physician and otolaryngologist performed LEMG. 91.3% of Spanish respondents worked in Public Health, 7.14% of other nationalities; 37.8% in a university department. Bipolar concentric needles electrodes were used by 45.9% and monopolar concentric by 40.5%. 57% professionals considered good patients’ tolerance to the test. LEMG sensitivity was regarded as strong, median and interquartile range were 80.0 [60.0;90.0] to diagnose peripheral nerve injuries, less for other levels of lesions, and strong to evaluate prognosis, 70.0 [50.0;80.0]. Respondents believe locate the thyroarytenoid and the cricothyroid muscles with the needle, 80.0 [70.0;90.0], as opposed to 20.0 [0.00;60.0] the posterior cricoarytenoid. The interpretation of the electrical parts of the LEMG was strong, 80.0 [60.0;90.0]. LEMG identify movements disorders, 60.0 [20.0;80.0], and synkinesis, 70.0 [30.0;80.0]. The professionals prefer quantitative LEMG, 90.0 [60.0;90.0]. ConclusionsThe experts surveyed consider LEMG that is well tolerated by patients. The insertional and spontaneous activity, recruitment and waveform morphology can be assessed easily. LEMG is mainly useful in the study of peripheral nerve injuries, and its value in VFP prognosis is considered strong.

Regulation of Inflammation, Without Impacting Heart Rate, via Electrical Stimulation of the Dorsal Motor Nucleus of the Vagus

The vagus nerve plays an important role in neuroimmune interactions and in the regulation of inflammation. Recently, using optogenetics it has been demonstrated that the brainstem’s dorsal motor nucleus of the vagus (DMN) is a significant source of efferent vagus nerve fibers that control inflammation. In contrast to optogenetics, electrical neuronal stimulation is an approved therapeutic approach. However, the anti-inflammatory effectiveness of electrical stimulation of the DMN (eDMNS) and the possible heart rate (HR) alterations associated with this approach have not been investigated. Here, we examined the effects of eDMNS on the HR and cytokine levels in murine endotoxemia as well as the cecal ligation and puncture (CLP) model of sepsis. C57BL/6 mice (8-10 weeks old), under anesthesia and secured in a stereotaxic frame, received eDMNS via a concentric bipolar electrode in the left or right DMN, or sham treatment. eDMNS (50, 250 or 500 μA and 30 Hz, for 1 min) was performed and HR recorded. In endotoxemia experiments, mice underwent sham or 5-minute eDMNS (250 μA or 50 μA) followed by LPS (0.5 mg/kg) i.p. injection. eDMNS was also studied on mice with cervical unilateral vagotomy or sham surgery. In CLP experiments sham or left eDMNS was performed immediately post CLP. Cytokines and corticosterone were measured 90 mins after LPS administration or 24h after CLP. CLP survival was monitored for 14 days. Both left and right eDMNS at 250 μA and 500 μA significantly reduced HR, compared with pre- and post-stimulation, while 50 μA did not. Left-side eDMNS at 50 μA decreased serum and splenic TNF levels, and increased serum IL-10 during endotoxemia. The anti-inflammatory effect of eDMNS was abrogated in mice with ipsilateral unilateral vagotomy, which was also not associated with serum corticosterone alterations. Right-side eDMNS lowered serum TNF levels and increased IL-10 but had no impact on splenic cytokines. In CLP, left eDMNS decreased serum TNF and IL-6 levels, lowered splenic IL-6 and increased splenic IL-10, and improved survival in mice. For the first time, we demonstrate that an eDMNS regimen, which does not cause bradycardia, mitigates LPS-induced inflammation. These effects are dependent on an intact vagus nerve and are unrelated to corticosteroid alterations. Additionally, eDMNS reduces inflammation and enhances survival in a polymicrobial sepsis model. These findings hold promise for further research into bioelectronic anti-inflammatory strategies aimed at the brainstem DMN. This work was partially funded by NIGMS. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Electrical stimulation of the dorsal motor nucleus of the vagus in male mice can regulate inflammation without affecting the heart rate

BackgroundThe vagus nerve plays an important role in neuroimmune interactions and in the regulation of inflammation. A major source of efferent vagus nerve fibers that contribute to the regulation of inflammation is the brainstem dorsal motor nucleus of the vagus (DMN), as recently shown using optogenetics. In contrast to optogenetics, electrical neuromodulation has broad therapeutic implications. However, the anti-inflammatory effectiveness of electrical stimulation of the DMN (eDMNS) and the possible heart rate (HR) alterations associated with this approach have not been investigated. Here, we examined the effects of eDMNS on HR and cytokine levels in mice administered with lipopolysaccharide (LPS, endotoxin) and in mice subjected to cecal ligation and puncture (CLP) sepsis. MethodsAnesthetized male 8–10-week-old C57BL/6 mice on a stereotaxic frame were subjected to eDMNS using a concentric bipolar electrode inserted into the left or right DMN or sham stimulation. eDMNS (500, 250 or 50 μA at 30 Hz, for 1 min) was performed and HR recorded. In endotoxemia experiments, sham or eDMNS utilizing 250 μA or 50 μA was performed for 5 mins and was followed by LPS (0.5 mg/kg) i.p. administration. eDMNS was also applied in mice with cervical unilateral vagotomy or sham operation. In CLP experiments sham or left eDMNS was performed immediately post CLP. Cytokines and corticosterone were analyzed 90 mins after LPS administration or 24 h after CLP. CLP survival was monitored for 14 days. ResultsEither left or right eDMNS at 500 μA and 250 μA decreased HR, compared with baseline pre-stimulation. This effect was not observed at 50 μA. Left side eDMNS at 50 μA, compared with sham stimulation, significantly decreased serum and splenic levels of the pro-inflammatory cytokine TNF and increased serum levels of the anti-inflammatory cytokine IL-10 during endotoxemia. The anti-inflammatory effect of eDMNS was abrogated in mice with unilateral vagotomy and was not associated with serum corticosterone alterations. Right side eDMNS in endotoxemic mice suppressed serum TNF and increased serum IL-10 levels but had no effects on splenic cytokines. In mice with CLP, left side eDMNS suppressed serum IL-6, as well as splenic IL-6 and increased splenic IL-10 and significantly improved the survival rate of CLP mice. ConclusionsFor the first time we show that a regimen of eDMNS which does not cause bradycardia alleviates LPS-induced inflammation. These eDMNS anti-inflammatory effects require an intact vagus nerve and are not associated with corticosteroid alterations. eDMNS also decreases inflammation and improves survival in a model of polymicrobial sepsis. These findings are of interest for further studies exploring bioelectronic anti-inflammatory approaches targeting the brainstem DMN.

Three-Dimensional Electrode-Enhanced Ozone Catalytic Oxidation for Thiamethoxam Wastewater Treatment: Performance, Kinetics, and Pathway

Thiamethoxam is a second-generation neonicotinoid pesticide that is used worldwide. In this study, a three-dimensional electrode-enhanced ozone catalytic oxidation system (3DE-GAC-O3) was constructed to pretreat thiamethoxam wastewater, with granular active carbon as the particle electrode. The effects of catalytic oxidation time, current density, ozone concentration, initial thiamethoxam concentration, pH, and particle electrode dosage on thiamethoxam degradation were investigated. A response surface method based on the Box–Behnken design was employed to optimize the 3DE-GAC-O3 process. The results revealed that the 3DE-GAC-O3 system exhibited higher efficiency compared with the 3D electrode method, ozone catalytic oxidation, or 2DE-O3. The optimal operating conditions included a particle electrode dosage, ozone concentration, current density, solution pH, catalytic oxidation time, and initial thiamethoxam concentration of 18 g/dm3, 12 g/h, 25 A/m2, 7, 300 min, and 500 mg/dm3, respectively. The corresponding chemical oxygen demand removal rate reached 93.86 ± 0.95%. Thiamethoxam degradation followed a second-order reaction kinetics equation, and the rate constant decreased with increasing the initial thiamethoxam concentration. Free-radical quenching experiments indicated that both O2∙− and ∙OH were present within the 3DE-GAC-O3 system, with ∙OH being the predominant species. A GC-MS analysis revealed the formation of several intermediate products, which were characterized based on the mass fragmentation pattern. Additionally, a probable degradation pathway for thiamethoxam was proposed. Therefore, 3DE-GAC-O3 is an efficient method for the pretreatment of thiamethoxam wastewater.

Tripolar concentric ring electrodes for capturing localised electroencephalography signals during sleep.

By design, tripolar concentric ring electrodes (TCRE) provide more focal brain activity signals than conventional electroencephalography (EEG) electrodes placed further apart. This study compared spectral characteristics and rates of data loss to noisy epochs with TCRE versus conventional EEG signals recorded during sleep. A total of 20 healthy sleepers (12 females; mean [standard deviation] age 27.8 [9.6] years) underwent a 9-h sleep study. Participants were set up for polysomnography recording with TCRE to assess brain activity from 18 sites and conventional electrodes for EEG, eyes, and muscle movement. A fast Fourier transform using multitaper-based estimation was applied in 5-s epochs to scored sleep. Odds ratios with Bonferroni-adjusted 95% confidence intervals were calculated to determine the proportional differences in the number of noisy epochs between electrode types. Relative power was compared in frequency bands throughout sleep. Linear mixed models showed significant main effects of signal type (p < 0.001) and sleep stage (p < 0.001) on relative spectral power in each power band, with lower relative spectral power across all stages in TCRE versus EEG in alpha, beta, sigma, and theta activity, and greater delta power in all stages. Scalp topography plots showed distinct beta activation in the right parietal lobe with TCRE versus EEG. EEG showed higher rates of noisy epochs compared to TCRE (1.3% versus 0.8%, p < 0.001). TCRE signals showed marked differences in brain activity compared to EEG, consistent with more focal measurements and region-specific differences during sleep. TCRE may be useful for evaluating regional differences in brain activity with reduced muscle artefact compared to conventional EEG.

Ground Resistance Estimation for a DC Converter Station: Theory versus Experiment

This paper is aimed at proposing a calculation model for the ground resistance of a grounding scheme servicing a high-voltage direct-current converter station. The method is based on the equivalence of current conduction and electric field from the grounding scheme through the surrounding medium. The grounding scheme is composed of three concentric ring electrodes supported by two horizontal conductors and eight vertical rods. The calculated ground resistance is 4.8 Ω against the experimental value of 5 Ω with an error of 4.2%. The calculated ground resistance value agrees reasonably well with that of 4.7 Ω as obtained using CYMGRD software (version 7.0). The calculated surface-potential values over the ground surface agreed reasonably well with those measured experimentally, with an average deviation not exceeding 6.5%. This study is designed to investigate how ground resistance is decreased by the increase in the scheme parameters, including the rods’ diameter and length, as well as the radius of the inner and outer rings. The dependency of the ground resistance on the soil type is also investigated.

Tripolar concentric ring electrodes for capturing localised electroencephalography signals during sleep

Tripolar concentric ring electrodes for capturing localised electroencephalography signals during sleep

A systematic approach to the modelling and comparison of the geometries of spherical electrodes in inertial electrostatic confinement fusion devices

Inertial electrostatic confinement fusion (IECF) devices often use two concentric spherical electrodes to converge ions in a plasma electrostatically. Using a highly transparent inner cathode, the ions can move through the cathode and collide at the center to undergo fusion reactions. This is a simple method to build a neutron source. Past research has focused chiefly on cathode “grids” manufactured by joining metal wire loops or disc-shaped elements via spot welding. There are two common geometries: “Globe” grids with a distinct latitude-longitude structure and “symmetric” grids with even-sized triangular-shaped apertures. Recent advances in additive manufacturing have opened the way to manufacturing a third class of grids in which the apertures are evenly distributed over the grid surface and have either circular or polygonal shaped apertures - here called “regular” grids. These three types are analyzed and compared based on a set of metrics, including transparency, homogeneity of aperture size, and the regularity of aperture distribution. It is shown that every type of grid comes with different advantages and disadvantages. The analysis focuses on grid geometries with 6 to 120 apertures.

Numerical Evaluation of the Frequency-Dependent Impedance of Hemispherical Ground Electrodes through Finite Element Analysis

Metallic electrodes are widely used in many applications, the analysis of their frequency-domain behavior is an important subject, particularly in applications related to earthing/grounding systems, from dc up into the MHz range. In this paper, a numerical evaluation of the frequency-dependent complex impedance of the hemispherical ground electrode is implemented. A closed-form solution for non-zero frequencies is still a difficult task to achieve as evidenced in a previous paper dedicated to the subject and, therefore, numerical approaches should be an alternative option. The aim of this article is to present a solution based on a numerical method using finite element analysis. In typical commercial FE tools, electric currents exhibit azimuthal orientation and, as such, the magnetic field has a null azimuthal component but non-null axial and radial components. On the contrary, a dual problem is considered in this work, with a purely azimuthal magnetic field. To overcome the difficulty of directly using a commercial FE tool, a novel formulation is developed. An innovative 2D formulation, the ι-form, is developed as a modification of the H-formulation applied to axisymmetric magnetic field problems. The results are validated using a classical 3D H-formulation; comparisons showed very good agreement. The electrode complex impedance is analyzed considering two different cases. Firstly, the grounding system is constituted by a hemispherical electrode surrounded by a remote concentric electrode; in the second case, the grounding system is constituted by two identical thin hemispherical electrodes. Computed results are presented and discussed, showing how the grounding impedance depends on the frequency and, also, on the radius of the remote concentric electrode (first case) or on the distance between the two hemispherical electrodes (second case).

Effects of Al doping concentration and top electrode on the ferroelectricity of Al-doped HfO2 thin films

Al-doped HfO2 (HAO) is regarded as one of the potential HfO2 ferroelectric materials owing to its compatibility with the front end of the line process in integration circuits. In this work, atomic layer deposited (ALD) HAO thin films with different Al-doping concentrations and the corresponding devices with Ti or W top electrodes have been explored. It is found that the HAO film properties and corresponding ferroelectric device performances depend greatly on the doping concentration. In the concentration range of 3.0%–5.0%, 4.5% is the most proper doping concentration to induce the ferroelectricity of the thin film. It is revealed by x-ray diffraction and photoelectron spectroscopy that the oxygen vacancies can be modulated by doping, thereby contributing to the formation of the ferroelectric orthorhombic phase. A high remnant polarization (2Pr) of 36.8 ± 0.7 μC/cm2 under 5 mV/cm sweeping is observed through electrical measurement in the device with a 4.5% HAO and W top electrode. In addition, it was found that the choice of W or Ti top electrodes would affect the leakage and breakdown characteristics of the device. This work reveals the mechanism of Al doping and electrode modulation of HfO2 device performance and promotes the development of HAO ferroelectric thin film devices.