Electrode Edge Research Articles

Two-dimensional fluid simulation of spatial distribution of dust particles in a capacitively coupled silane plasma

In this work, we develop a two-dimensional fluid model to study the spatial density distributions of dust particles in a radio frequency capacitively coupled silane plasma. Unlike those scenarios based on the one-dimensional fluid model, in this work, the nonuniformity of the radial density distributions of dust particles is attributed mainly to the radial components of the electric field force and the ion drag force acting on the dust particles, leading to the two local density peaks near the electrode edges. It seems that dust particles tend to overcome the support of the electric field force and move much closer to the electrodes, as one of the density peaks indicates. Moreover, with the decrease of the radii of the discharge electrodes or the distance between them, the radial component of the ion drag force is enhanced, resulting in more dust particles gathering near the electrode edge region, and forming a ring-shaped particle density distribution. In the case of the discharge electrodes wrapped with dielectric materials, the uniformity of the radial density distributions of dust particles between the two electrodes is improved. Finally, the vortex motion of a single dust particle near the electrode edge region is also simulated in this work.

Study on Mechanical Properties and Failure Mechanism of Medium Manganese TRIP Steel / DP590 Dissimilar Steel Resistance Spot Welding Joint

This paper presents the resistance spot welding process test and numerical simulation analysis of medium manganese steel TRIP steel (7MnSteel) and DP590 steel plate. The results show that the failure mode is PF-TT failure, and IF and PF-TT are investigated. At the same time, based on the numerical simulation under the typical welding parameters, the welding plate has the stress concentration at the electrode edge at the beginning of the welding. Along with the welding, there is the stress concentration in the heat-affected zone of the medium manganese TRIP steel, which may also be the reason for the failure of the joint here. The current density is concentrated at the contact surface between the electrode and the weld plate, and the error in the diameter of the nugget measured by simulation and experiment is within 7%, which verifies the accuracy and reliability of the model.

N-Type Printed Organic Source-Gated Transistors with High Intrinsic Gain.

Source-gated transistors (SGTs) are emerging devices enabling high-gain single-stage amplifiers with low complexity. To date, the p-type printed organic SGT (OSGT) has been developed and showed high gain and low power consumption. However, complementary OSGT circuits remained impossible because of the lack of n-type OSGTs. Here, we show the first n-type OSGTs, which are printed and have a high intrinsic gain over 40. A Schottky source contact is intentionally formed between an n-type organic semiconductor, poly{[N,N'-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (N2200), and the silver electrode. In addition, a blocking layer at the edge of the source electrode plays an important role to improve the saturation characteristics and increase the intrinsic gain. Such n-type printed OSGTs and complementary circuits based on them are promising for flexible and wearable electronic devices such as for physiological and biochemical health monitoring.

High Breakdown Electric Field Diamond Schottky Barrier Diode With SnO2 Field Plate

Diamond is desirable for the application in power device due to its extremely high theoretical breakdown electric field (>10 MV/cm). However, because of electric field crowding, relatively low experimental results of breakdown electric field were attained. The vertical diamond with SnO2 field plate (FP) exhibiting excellent performance was fabricated. SnO2 deposited by electron beam evaporation with high dielectric constant of 17 possesses the potential to alleviate crowding field at the edge of Schottky electrodes. The SnO2 FP SBD shows high breakdown electric field of 4.04 MV/cm and high breakdown voltage of 185 V, which is 69.7% higher than diamond SBD without FP. The suppression of leakage current can also be observed in SBD with SnO2 FP. The edge electric field crowding of Schottky contact has been mitigated effectively by FP structure. Meanwhile, the FP SBD can still maintain low differential resistance of 1.31 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}\Omega \cdot \text {cm}^{{2}}$ </tex-math></inline-formula> , high forward current of 4740 A/cm2, unchanged Schottky barrier height, and ideality factor. It is suggested that SnO2 FP structure is a good method to improve reverse characteristics without compromising the forward performance of SBD, and this FP enables diamond SBD potential for power electronic devices.

Area-selective growth for patterning and separation of molecules at allocated sites: Designed kinetic Monte Carlo simulation for anisotropic molecules

Micro-patterning of organic thin films plays a crucial role for organic electronics. Due to the high resolution over large areas, several photo-lithography compatible techniques for the patterning of organic films were developed. As a promising candidate, area-selective growth (ASG), i.e., the growth of molecules on patterned surface for nucleation control, has been proposed. Experimentally, two typical molecules, categorized into non-planar and planar molecular configuration, exhibit different growth behavior, which is mechanistically attributed to binding energy difference and step-edge induction on patterned surface. Benefiting from the diffusion and nucleation sites control of the different configuration molecules, patterning and separation of multi-species molecules at micro-scale were demonstrated. For the ASG of non-planar molecules, the molecular dynamics has been well explored using the kinetic Monte Carlo (KMC) simulations. However, little attention is paid to the step-edge induced ASG for anisotropic molecules. Here, we introduce a coarse-grained anisotropic interaction model in the KMC algorithm to simulate the step-edge induced ASG. Our results reveal that the edges of electrode (Au) patterns become preferential nucleation sites at initial stage, followed by the lateral growth of subsequent particles due to the strong π-π interactions. In combination with the KMC simulation for binding energy difference mechanism, separation of different particles on designed locations are theoretically demonstrated to mimic the molecular separation that experimentally observed. Our results also validate the KMC simulation as a powerful means for the ASG process of anisotropic molecules in a microscopic view, in addition to the ASG process of isotropic molecules. We believe that the KMC method will provide a deeper insight of the ASG method for organic molecules with different molecular architectures.

Characterization of peripheries of n-GaN Schottky contacts using scanning internal photoemission microscopy

We applied scanning internal photoemission microscopy (SIPM) to clarify the electrical characteristics on the electrode periphery of Ni/n-GaN Schottky contacts. Two types of Schottky contacts with different electrode formation methods were prepared. For the samples in which the Ni contacts were evaporated through a metal shadow mask, in the scanning electron microscopes (SEM) observation, the electrode edges were tailed and the tail was divided into two contrasts, a bright region with a width of 15.5 μm from the electrode edge followed by a dark region with a width of 32 μm. The SIPM signal was obtained from the first 16 μm tailing region, and corresponded with the SEM images. For the photolithography sample, a sharp edge less than 1 μm wide was obtained and no increase in SIPM signal was detected on the edge. These results indicate SIPM is able to characterize the electrical properties of electrode periphery in conjunction with the structural characteristics.

Elevated cerebrospinal fluid protein levels associated with poor short-term outcomes after spinal cord stimulation in patients with disorders of consciousness.

Spinal cord stimulation (SCS) is a promising treatment for patients with disorders of consciousness (DoC); however, the laboratory examinations and different electrodes (permanent #39286 vs. temporary percutaneous #3777, Medtronic, USA) that are associated with postoperative outcomes are unclear. The study aims to study the association between the change in postoperative cerebrospinal fluid (CSF) protein level and improvement in consciousness after SCS in DoC patients and to explore whether different electrodes were associated with elevated CSF protein levels. A total of 66 DoC patients who received SCS treatment from December 2019 to December 2021 were retrospectively analyzed. Patients were grouped according to their elevated CSF protein level. The clinical characteristics of the patients and SCS stimulation parameters were compared. The preoperative sagittal diameter of the spinal canal is the distance from the midpoint of the posterior border of the vertebral body to the midpoint of the posterior wall of the spinal canal at the level of the superior border of C3. The postoperative sagittal diameter of the spinal canal is the distance from the midpoint of the posterior edge of the vertebral body to the anterior edge of the stimulation electrode. Patients with improved postoperative CRS-R scores greater than 3 or who progressed to the MCS + /eMCS were classified as the improved group and otherwise regarded as poor outcome. We found that more DoC patients had elevated CSF protein levels among those receiving SCS treatment with permanent electrodes than temporary percutaneous electrodes (P = 0.001), and elevated CSF protein levels were significantly associated with a reduced sagittal diameter (P = 0.044). In DoC patients receiving SCS treatment, we found that elevated CSF protein levels (P = 0.022) and preoperative diagnosis (P = 0.003) were significantly associated with poor outcomes at 3 months. Logistic regression analysis showed that elevated CSF protein levels were significantly associated with poor outcomes (OR 1.008, 95% CI 1.001-1.016, P = 0.032). The results suggest that reducing the effect of electrode pads on anatomical changes may help improve the outcomes of DoC patients receiving SCS treatment. CSF protein levels are associated with poor postoperative outcomes and whether they are potential biomarkers in DoC patients receiving SCS treatment remain further exploration.

Geometrical and electrical optimization of NS-SDBD streamwise plasma heat knife for aircraft anti-icing

Ice accretion on aircraft encountering supercooled water droplets in clouds poses great risks to flight performance and safety. With the aim of optimizing the newly developed streamwise plasma heat knife method for anti-icing, a parametric investigation is carried out in this work. The influence of the detailed voltage profile on the heating effects of a Surface Dielectric Barrier Discharge driven by Nanosecond Pulses (NS-SDBD) is investigated, and a comparison of the anti-icing performance among different configurations of streamwise plasma heat knife is made. The results show that columnar high-temperature regions produced by a multi-streamer discharge appear at small pulse rise time, but become diffuse as the pulse rise time increases. An optimal pulse rise time exists to provide a wide range and high value of temperature, which is found to be 150 ns for the setup in the present study. The influence of the pulse fall time is much weaker than that of the rise time. The range and value of the temperature decrease with increasing pulse fall time. A greater pulse width is found to improve the heating effect by increasing the discharge power. When a spanwise electrode is placed connecting the streamwise electrodes of the streamwise plasma heat knife at the airfoil leading edge, the anti-icing performance becomes poorer, whereas good performance is achieved when the spanwise electrode is at the edge of the streamwise electrodes. Based on this, a three-level configuration of the plasma heat knife is proposed, and its anti-icing performance is found to be much better than that of the original configuration.

Helium Metastable Distributions and Their Effect on the Uniformity of Hydrogenated Amorphous Silicon Depositions in He/SiH4 Capacitively Coupled Plasmas

This study investigates, numerically, the spatial distribution of metastable helium (He*) in He/SiH4 capacitively coupled plasma (CCP) for the purpose of optimizing plasma density distributions. As a first step, we presented the results of a two-dimensional fluid model of He discharges, followed by those of He/SiH4 discharges to deposit hydrogenated amorphous silicon films, to investigate which factor dominates the coating uniformity. We retained our CCPs in the 300 mm wafer reactor used by the semiconductor industry in the recent past. Selected parameters, such as a sidewall gap (radial distance between the electrode edge and the sidewall), electrical condition of the sidewall, and position of the powered electrode, were considered. In addition, by increasing the gas pressure while varying the sidewall condition, we observed modification of the plasma distributions and, thus, the deposition rate profiles. According to the results, the shift in He* distributions was mainly due to the reduction in the electron mean free path under conditions of gas pressure higher than 100 Pa, as well as local perturbations in the ambipolar electric field due to the finite electrode structure. Small additions of SiH4 largely changed the He* density profile in the midplane of the discharge due to He* quenching. Furthermore, we found that the wide sidewall gap did not improve deposition uniformity against the expectation. This was because the excitation and ionization rate profiles were enhanced and localized only near the bottom electrode edge.

High-performance thin-film transistor device architecture for flexible and printed electronics

A device design paradigm for thin-film transistors (TFTs) suitable for fabrication using methods available for flexible and printed electronics devices and circuits is described. The TFT architecture utilizes an array of nanospike-shaped electrodes as the source and drain electrodes. This results in improved carrier injection, greater gate control of the drain current, and lower threshold and operating voltage. The on-currents are also higher in comparison with standard flat edge electrode TFTs with equivalent channel dimensions. Importantly, the design is very tolerant of thick gate insulators. The proposed architecture requires one level of relatively high resolution patterning of the source and drain contacts, which can be potentially realized with methods that have been previously employed in flexible electronics such as nanoimprint lithography or roll-to-roll photolithography. The experimental data presented in this paper were obtained from TFTs fabricated using conventional fabrication methods, as the emphasis in this paper is on the device design and in demonstrating the advantageous features of the new architecture in future flexible systems.

Field analyses of thickness shear bulk acoustic resonators with different electrode edge ratio using full three dimensional finite element method simulation

This paper is aimed at revealing origins of spurious resonances and Q deterioration of thickness shear bulk acoustic resonators (TSBARs) with the edge ratio W x /W y of rectangular electrodes by a field analyses. Here, W x and W y are distances between side edges giving the broadband and standard piston designs, respectively. The field distribution is calculated by applying traceback technique to the full three dimensional finite element method based on hierarchical cascading technique, its variation with the edge ratio is studied in detail, with assistance of the wavenumber domain analysis. The result indicates that the mode conversion and the leakage occur at the bump region causing Q reduction, and generated hybrid modes causing spurious resonances. The former is significant when W x /W y is large and the latter becomes obvious when W x /W y is small.

Dynamic Characteristics of Transverse-Magnetic-Field Induced Arc for Plasma-Jet-Triggered Protective Gas Switch in Hybrid UHVDC System

A plasma jet-triggered gas switch (PJT-GS) has been developed as an important piece of equipment to operate in an ±800 kV ultra-high voltage direct current transmission system (UHV DC) to achieve grid system protection and control. The crucial factors that would affect its operational performance, such as the current level the PJT-GS could withstand and the gas gap distance between the two rotating electrodes, are comparatively studied in the present work by analysing the arc dynamic characteristics. The rotating electrode used in the PJT-GS is designed with a helical-slotted structure, and the arc can be rotated circularly driven by the produced transverse magnetic field (TMF) along the electrode edge. The objective of such research is to provide a thorough study of the arc dynamic behaviour during the current flowing process of the PJT-GS and also to characterise the physical mechanism that affects the arc rotation and the PJT-GS operation performance. The magnetohydrodynamic-based (MHD) approach is applied by establishing a 3D arc model. Following such a study, the variation of arc characteristics under different operation conditions could be thoroughly determined and it also could provide the guidance for the PJT-GS optimum design reasonably to support its corresponding engineering applications.

Anode passivation mitigation by homogenizing current density distribution in electrocoagulation

Electrode passivation is the most challenging technical problem in electrocoagulation (EC) water treatment process, but research on understanding and mitigating passivation evolution are still lacking. Herein, homogenization of current density (CD) distribution was found to be a critical factor in alleviating the anode passivation during EC process. Decreasing electrode area decelerated the growth of passivation layer on anode through homogenizing CD distribution, which was quantified by the ratios of CD distributed at the electrode edges and centers. When aluminum anode area decreased from 8 cm2 to 2 cm2 with a constant CD, the homogenization degree increased by 24.0%, and passivation was reduced by 24.3%. The depth profiles of passivated anodes confirmed the inhomogeneity of the anode passivation. Thicker passivation layers were observed at edges due to high CD distributions, which originated from the “edge effect” of electric field distribution between parallel plate electrodes. A facile strategy to homogenize CD distribution by splitting electrodes into smaller electrodes is then proposed for passivation mitigation, which can save energy consumption by 21.8% with unchanged removal efficiency. This study provides a unique insight into anode passivation mitigation and a feasible electrode design in EC.

Effect of electric bias on trapping and release of excitons in GaN/(Al,Ga)N quantum wells

A giant built-in electric field in the growth direction makes excitons in wide GaN/(Al, Ga)N quantum wells spatially indirect even in the absence of any external bias. Significant densities of indirect excitons can accumulate in electrostatic traps imprinted in the quantum well plane by a thin metal layer deposited on top of the heterostructure. By jointly measuring spatially resolved photoluminescence and photo-induced current, we demonstrate that exciton density in the trap can be controlled via an external electric bias, which is capable of altering the trap depth. Application of a negative bias deepens the trapping potential, but does not lead to any additional accumulation of excitons in the trap. This is due to exciton dissociation instigated by the lateral electric field at the electrode edges. The resulting carrier losses are detected as an increased photocurrent and reduced photoluminescence intensity. By contrast, application of a positive bias washes out the electrode-induced trapping potential. Thus, excitons get released from the trap and recover free propagation in the plane that we reveal by spatially resolved photoluminescence.

High-Performance Electro-Optical Mach–Zehnder Modulators in a Silicon Nitride–Lithium Niobate Thin-Film Hybrid Platform

We analyzed a Mach–Zehnder electro-optical modulator based on a silicon nitride strip–loaded waveguide on 0.5 μm thick x-cut lithium niobate thin film. The optical and radio frequency parameters for two different modulator structures (Type I: packaged with 2 μm thick SiO2 and Type II: unpackaged) were simulated, calculated, and optimized. The Optical parameters included the single-mode conditions, effective indices, the separation distance between the electrode edge and the Si3N4-strip-loaded edge, optical power distribution, bending loss, optical field distribution, and half-wave voltage. The radio frequency parameters included the characteristic impedance, attenuation constant, radio frequency effective index, and −3 dB modulation bandwidth. According to the numerical simulation and theoretical analysis, the half-wave voltage product and the −3 dB modulation bandwidth were, respectively, 2.85 V·cm and 0.4 THz for Type I modulator, and 2.33 V·cm and 1.26 THz for Type II modulator, with a device length of 3 mm.

Switchable 2D/3D display based on a liquid crystal lens array and the rotating specimen shooting method.

A liquid crystal (LC) lenticular lens array with auxiliary electrodes is proposed. The introduction of the auxiliary electrodes helps to obtain an LC lens array (LCLA) with relatively large aperture without complex structures. When the LCLA is in the focusing state, the voltage of auxiliary electrodes is less than that of edge electrodes, and the generated electric field in the LCLA can penetrate into the LC layer. Therefore, the ideal phase profile is obtained with a relatively thin LC layer thickness. Experimental results show that the LCLA has the characteristics of high optical power and low operation voltage. Based on the proposed LCLA, a multi-view 2D/3D switchable display is realized. In the experiment, a series of parallax images is obtained by rotating the sample to replace the convergence shooting method for 3D imaging. Compared with other 2D/3D switchable display devices, the multi-view 2D/3D switchable display based on the LCLA is characterized by being thin and compact, and displaying no moiré pattern.

The growth condition for ferroelectric domains of a subcritical size

Growth conditions for repolarization nuclei in Pb(Zr1-xTix)O3 polycrystalline ferroelectric films with frequency dependence of coercive field of ln(ν/ν0)∼1/Ec 2 are studied. The main contribution to polarization switching is provided by the formation of nuclei of a critical size by means of thermal fluctuations. However, near electrode edges the growth of nuclei of a subcritical size is shown to be possible. Free energy release accompanying the growth of a nucleus does not depend on its size. This enables rapid growth of nuclei near electrode edges and explains experimentally observed dependence of the limiting frequency for polarization switching on the electrode geometry.

Evaluation of dielectric breakdown of BaTiO3 by novel indentation method

Succinct evaluation of dielectric breakdown strength of dielectric materials has been hampered by extrinsic parameters like size/thickness dependence, electrode configuration, and defect concentration which all mask the materials’ intrinsic value. A novel indentation method to prepare arch-shaped indents on the surface of BaTiO3 green stacks has been developed to overcome this problem. Utilizing this method enables simple and reliable sample preparation for investigation of dielectric breakdown behavior. Theoretical and experimental investigations reveal vanishing electrode edge effects governed by the improved distribution of electric field due to the arch-shaped indents. Thus, the novel indentation method bears advantages compared to measuring DBS of disk-shaped samples and allows for narrowing influences of extrinsic parameters. By obtaining breakdown channels close to the center of the indent, this technique additionally features the possibility of localizing the breakdown event.

Excellent Stability of Perovskite Solar Cells Encapsulated With Paraffin/Ethylene-Vinyl Acetate/Paraffin Composite Layer

Superior encapsulation technology is important for PSCs to prolong their lifetime and realize their commercial application. Paraffin/EVA/paraffin composite encapsulated layers were fabricated with the ambient environment under the thermal temperature of 80°C, which has advantages for simple procedures and low cost. PSCs encapsulated with paraffin/EVA/paraffin and pure EVA layers maintained 95 and 45% of the initial power conversion efficiency (PCE) aged for 1000 h at RH 75%, respectively. Paraffin/EVA/paraffin-encapsulated PSCs were immersed in water for 5 h, which remained 98% of the original PCE, which is far superior to EVA-encapsulated PSCs. High melting point paraffin at 68°C shows better encapsulation than low melting point (60 and 55°C) paraffin, indicating that the high molecular weight of paraffin helps improve the encapsulation performance of PSCs. PSCs encapsulated with paraffin/EVA/paraffin showed better stability of Voc than pure EVA layer because paraffin can inhibit defects, voids, and edges of metal electrodes that quickly expand, and decay. Therefore, paraffin/EVA/paraffin combination encapsulation is an effective strategy, which can form continuous and dense hydrophobic composite encapsulation films with a friendly metal electrode.

Numerical simulation of coaxial–coplanar dielectric-barrier discharge in atmospheric helium

A self-consistent two-dimensional fluid model is employed to investigate the coaxial–coplanar dielectric-barrier discharge (DBD) excited by the sinusoidal voltage in atmospheric helium. Simulation results show that there are two current pulses in the positive half cycle, but only one in the negative half cycle. The discharge is transformed from the Townsend-like mode, through the glow-like mode, and back to the Townsend-like mode in both the positive and negative half cycles, during which the electric field line exhibits an arc-shape profile due to the configuration of coaxial–coplanar electrodes. In the glow-like mode, the cathode fall is located near the inner edge of the ground electrode at the first positive current peak, but close to the outer edge of the ground electrode at the second positive current peak. At the negative current peak, the cathode fall is distributed near the outer edge of the high voltage electrode. Since the instantaneous anode and the instantaneous cathode are on the same side of the discharge space, the dielectric layer is simultaneously covered by positive and negative surface charges due to the movement of charged particles. It is also found that the surface charge density changes significantly on the dielectric layer facing the electrodes. A further study reveals that a stronger discharge always occurs in the central circular area and an alternately complementary discharge takes place in the periphery ring area in the positive half cycle due to the activator–inhibitor effect. This feature is helpful for producing uniform plasma in a whole cycle of DBD.