Electrode Region Research Articles

Electrophoresis and Quartz Crystal Microbalance Instrumentation to Sense Nanoplastics in Water.

We report a Technical Note on detecting nanoplastics in water samples through electrophoresis and quartz crystal microbalance (QCM) instrumentation. We conducted electrophoresis experiments by immersing a QCM in a sample of ultrapure water containing polyethylene (PE) nanoplastics. It was interesting to observe that nanoplastics were attracted toward the QCM and adhered to one side of the QCM electrode. The attached particles introduced mass loading to the QCM and were characterized by a decrease in resonance frequency of the crystal. Furthermore, when a small region around the center of electrode was alone exposed for direct contact in water and the rest of the electrode was masked using photoresist, the nanoplastics were concentrated only in the exposed electrode region, significantly enhancing detection sensitivity. To further investigate the applicability for real-life water samples, we experimented with the technique with readily available bottled drinking water and mineral water, where we spiked these water samples with nanoplastics. It was observed that the resonance frequency shifts were significantly larger for samples with nanoplastics compared to samples without nanoplastics. In addition, Raman spectroscopy and microscopy imaging were used to further confirm the presence and locations of nanoplastics on the electrode surface. This study highlights the combination of electrophoresis and QCM effectiveness in detecting nanoplastics across different water types and their potential for broader applications in environmental monitoring.

Flexible Strain Sensors with Ultra-High Sensitivity and Wide Range Enabled by Crack-Modulated Electrical Pathways

HighlightsA method is proposed for the modulation of electrical pathways in the cracks of stretchable electrodes using liquid metals, based on which ultra-high sensitivity (> 108) and large-range (> 100%) strain sensors are realised.A secondary modulation of the response (or performance) of the sensor is proposed, allowing not only electrical modulation by liquid metal patterning during fabrication, but also mechanical modulation by pre-stretching at the time of use.The air permeability and stability of the patterned liquid metal electrode region is optimised to enable air permeability similar to that of conventional fabrics and cycle durability in excess of 2000 cycles.

Iodine migration in lead halide perovskite solar cells investigated by X-ray photoelectron spectroscopy

Abstract We investigate iodine migration in lead halide perovskite solar cells using X-ray photoelectron spectroscopy. We observe iodine migration to the surface direction at both the solar cell’s electrode and non-electrode regions. Our findings suggest that diffusion can drive iodine migration even without an electric field. We also detected iodine accumulation near the Ag electrode, probably related to increased series resistance and reduced efficiency. Present results highlight the need for a dense interfacial layer to suppress iodine migration.

The effect of non-perpendicular incidence angles on discharge characteristics in an argon atmospheric plasma jet impinging on metal, water and glass substrates

The spatial–temporal discharge behavior of an AC argon plasma jet tilted at non-perpendicular incidence angles (60°, 45°, and 30°) interacting with an ungrounded metal, water, and glass plate placed on the jet propagation track was studied by the fast-imaging technique. The conductivity of surface and incidence angles plays an essential role in the discharge current and dynamic process of the plasma jet. The nearly consistent time delay between subsequent breakdowns occurred four times for metal and two times for glass treatments. The mean luminous intensity of the plasma in one discharge cycle at the discharge area between ground electrode and target surface region for the water and glass case decreased by 39.5% and 20.5% when the incidence angle decreased from 60° to 30°, respectively. In particular, the incidence angle and gas flow rate notably impacted the spatial extension behavior created on the glass surface but had no significant difference in discharge characteristic of plasma jet with metal case. In addition, two equivalent circuit models were developed based on the simulation of the micro-discharges and the geometry of the “plasma jet–substrate” system, respectively. These results will obtain further insight into the underlying mechanisms of plasma-target interaction and facilitate the designing of appropriate jet for environmental and biomedical applications.

Visualizing and Quantifying Electronic Accessibility in Composite Battery Electrodes using Electrochemical Fluorescent Microscopy

Electronic connections between active material particles and the conductive carbon binder domain govern high-energy commercial Li-ion batteries' rate capability and lifetime (LIB). This work develops an in situ electrochemical fluorescent microscopy (EFM) technique that maps fluorescence intensity to these local electronic connections. Specifically, rapid redox kinetics of an electrofluorophore translates to reaction distributions limited by the electronic accessibility of battery electrode regions and individual active material particles. This technique can visualize hot spots, dead zones, and isolated particles on the electrode surface. EFM characterization of a series of LiNi0.33Mn0.33Co0.33O2 electrodes across processing parameters finds a significant negative correlation between the number of disconnected active particles and the rate capability. This low-cost technique provides quantitative mesoscale characterization of commercial LIB electrodes with fast throughput (<60 s) to facilitate rapid research and development and provide manufacturing quality control.

Giant tunneling resistance and robust switching behavior in ferroelectric tunnel junctions of WS2/Ga2O3 heterostructures: The influence of metal–semiconductor contacts

The ferroelectric tunneling junctions (FTJs) are widely recognized as one of the non-volatile memories with significant potential. Ferroelectricity usually fades away as materials are thinned down below a critical value, and this problem is particularly acute in the case of shrinking device sizes, thus attracting attention to two-dimensional ferroelectric materials (2DFEMs). In this work, we designed 2D ferroelectric Ga2O3-based FTJs with out-of-plane polarization, and the influence of metal–semiconductor contact in the electrode region on the system is considered. Here, using density functional theory combined with the non-equilibrium Green's function approach to quantum transport calculations, we demonstrate robust ferroelectric polarization-controlled switching behavior between metallic and semiconducting states in Ga2O3/WS2 ferroelectric heterostructures. The potential barrier of the metal–semiconductor contact in the electrode region is lower than that of the intrinsic material, thereby resulting in an increased probability of electron tunneling. Our results reveal the crucial role of 2DFEMs in the construction of FTJs and highlight the significant impact of electrode contact types on performance. This provides a promising approach for developing high-density ferroelectric memories based on 2D ferroelectric semiconductor heterostructures.

High-Throughput Combinatorial Analysis of the Spatiotemporal Dynamics of Nanoscale Lithium Metal Plating.

The development of Li metal batteries requires a detailed understanding of complex nucleation and growth processes during electrodeposition. In situ techniques offer a framework to study these phenomena by visualizing structural dynamics that can inform the design of uniform plating morphologies. Herein, we combine scanning electrochemical cell microscopy (SECCM) with in situ interference reflection microscopy (IRM) for a comprehensive investigation of Li nucleation and growth on lithiophilic thin-film gold electrodes. This multimicroscopy approach enables nanoscale spatiotemporal monitoring of Li plating and stripping, along with high-throughput capabilities for screening experimental conditions. We reveal the accumulation of inactive Li nanoparticles in specific electrode regions, yet these regions remain functional in subsequent plating cycles, suggesting that growth does not preferentially occur from particle tips. Optical-electrochemical correlations enabled nanoscale mapping of Coulombic Efficiency (CE), showing that regions prone to inactive Li accumulation require more cycles to achieve higher CE. We demonstrate that electrochemical nucleation time (tnuc) is a lagging indicator of nucleation and introduce an optical method to determine tnuc at earlier stages with nanoscale resolution. Plating at higher current densities yielded smaller Li nanoparticles and increased areal density, and was not affected by heterogeneous topographical features, being potentially beneficial to achieve a more uniform plating at longer time scales. These results enhance the understanding of Li plating on lithiophilic surfaces and offer promising strategies for uniform nucleation and growth. Our multimicroscopy approach has broad applicability to study nanoscale metal plating and stripping phenomena, with relevance in the battery and electroplating fields.

A self-growing “Polysulfide-Phobic” interface constructed by in-situ gelation of organic bentonite interlayer to suppress shuttle effect in lithium-sulfur batteries

The shuttle effect of polysulfides hinders the long-term operation of lithium-sulfur batteries (LSBs). As the secondary current collector, the conductive interlayer can achieve induced fixation of polysulfide within a certain range, but the mechanism of action is limited by bearing saturation of the interlayer on polysulfide. In this work, the limited gelation of organic bentonite (OB) in the electrolyte is utilized to construct an in-situ gel-type physical barrier. During the initial discharge activation stage, the gel layer gradually evolves into a "Polysulfide-Phobic" repulsive layer by trapping free Lithium-polysulfides (LiPSs). Due to the strong repulsion between the "Polysulfide-Phobic" layer and free polysulfide anions, the spatial distribution of LiPSs in the positive electrode region is changed. In addition, the physical barrier effect of the gel interlayer and the chemisorbed action on LiPSs ensure the stability of the "Polysulfide-Phobic" layer during the discharge stage, while the low electronic conductivity avoids the risk of oxidation decomposition of the interface during the charging stage, which is verified by in-situ Raman. The Cells with OB interlayers show excellent cycle stability (515.5 mAh g−1 after 300 cycles) under high loading conditions (5 mg cm−2, E/S ≈ 7.5 μL mg−1). This strategy of sacrificing initial efficiency to build an electrostatic repulsion layer in exchange for long-term stability is profitable, providing a new approach to addressing the shuttle effect.

Influence of laser power and beam path under nonuniform AC electric fields on 3D microvortex flow

This paper describes the effect of optical light on the generation and manipulation of microvortex flow named ‘twin opposing microvortex’ (TOMV) flow. This opto-electrohydrodynamic (OEHD) technique combines optical light, i.e. infrared (IR) laser (1064 nm), with non-uniform AC electric fields generated from a pair of indium tin oxide (ITO) electrodes. When the IR laser beam passes through the electric fields, a rapid and three-dimensional (3D) vortex flow is generated in a microchamber. When the laser beam passes through the electric fields, especially the exposed ITO electrode, the direction of the TOMV flow as well as its strength are controlled. With an AC signal of 107 kHz and various voltages below a peak-to-peak voltage of 10 V, laser power is varied up to 1.5 W and the path of a laser beam relative to the electrode (300 μm long and 16 μm wide) is manipulated. The maximum in-plane velocity outside the electrode region was obtained by micron-resolution particle image velocimetry (μPIV). When the laser beam passes through the left or right side of the lower electrode, the TOMV flow field rotates counterclockwise or clockwise, respectively. Applying optical light on an ITO electrode creates in situ and on-demand microvortex flow, which increases the feasibility of OEHD technique in various biological and chemical applications (e.g., mixing and delivering nanofluids in microfluidic devices).

Deconvolution of Cyclic Voltammograms in the Hydrogen Region of the Platinum-Black Electrodes with the Asymmetric Double Sigmoid Function

Deconvolution of Cyclic Voltammograms in the Hydrogen Region of the Platinum-Black Electrodes with the Asymmetric Double Sigmoid Function

Eulerian-Eulerian-VOF multifluid modelling of liquid–gas reacting flow for hydrogen generation in an alkaline water electrolyser

Alkaline water electrolysis is a promising technology for hydrogen production. However, its efficiency drops considerably at high current densities due to the mass transfer limitation and the increase in electrical resistivity arising from the complexity of the liquid–gas reacting flow behaviour within the electrolyser cell. In this work, a computational fluid dynamics (CFD) model is developed to describe the liquid–gas reactive flow behaviour. The model integrates the Eulerian-Eulerian two-fluid model and the multifluid Volume of Fluid (VOF) model, allowing the mathematical model to capture the electrochemical reaction effect on hydrogen gas formation and bulk flow bubble behaviour. The model is validated against prior experimental results. The simulation results suggest that, at higher current densities, the electrical performances and the mass transfer rates are highly influenced by the formation of gas bubbles, which may block the active sites for the electrochemical reaction to occur. Quantitatively, at 4000 A/m2, the mass transfer rate is reduced by 50% at regions above the cathode compared to electrode region, while electrical conductivity near the flow channel wall, drops by 17% compared to the bulk liquid electrical conductivity. The predicted electrical conductivity is comparable to the Bruggemann correlation with an average relative error of less than 2%, confirming the model’s validity in predicting the reacting flow behaviour and performance of the electrolyser. The numerical model offers a cost-effective tool for insightful understanding and refining the design and operation of hydrogen generation systems.

Surface crystallization effects on tellurium oxide thin films for low-power complementary logic circuit applications

Van-der-Waals-structured tellurium (IV) has demonstrated its potential as a promising building block for complementary logic device due to its superior electrical and optoelectronic features. Here, we demonstrated the novel approach for developing high-performance tellurium oxide (TeOX) thin film through TeOX formation and surface crystallization (SC). The crystalline structures and chemical bindings of the TeOX surfaces were carefully engineered by time- and temperature-dependent UV-ozone treatment and ALD-grown-Al2O3-assisted crystallization. The huge enhancement of device performance was achieved in the optimized SC-TeOX transistor, especially high on–off current ratio of 2.19 × 106, which can be ascribed to the synergistic effects of TeOX formation and SC process resulting in the enlarged bandgap, strong valence band edge localization, and the improved crystallinity. The performance enhancement mechanism was systematically studied by constructing SC-TeOX transistor with different TeOX region, where the TeOX creation in both Te channel and source/drain electrode regions dramatically improved performance owing to the decreased contact resistance and enhanced charge transport. Consequently, we achieved the high-performance low-power complementary logic circuits with SC-TeOX transistors, even reaching the maximum gain of 67.9 and low static power of 0.5 nW. Thus, this work demonstrates the great potentials of SC-TeOX transistor for developing advanced low-power complementary logic circuits.

High Efficiency Flat-Type GaN-Based Light-Emitting Diodes with Multiple Local Breakdown Conductive Channels.

We investigated a flat-type p*-p LED composed of a p*-electrode with a local breakdown conductive channel (LBCC) formed in the p-type electrode region by applying reverse bias. By locally connecting the p*-electrode to the n-type layer via an LBCC, a flat-type LED structure is applied that can replace the n-type electrode without a mesa-etching process. Flat-type p*-p LEDs, devoid of the mesa process, demonstrate outstanding characteristics, boasting comparable light output power to conventional mesa-type n-p LEDs at the same injection current. However, they incur higher operating voltages, attributed to the smaller size of the p* region used as the n-type electrode compared to conventional n-p LEDs. Therefore, despite having comparable external quantum efficiency stemming from similar light output, flat-type p*-p LEDs exhibit diminished wall-plug efficiency (WPE) and voltage efficiency (VE) owing to elevated operating voltages. To address this, our study aimed to mitigate the series resistance of flat-type p*-p LEDs by augmenting the number of LBCCs to enhance the contact area, thereby reducing overall resistance. This structure holds promise for elevating WPE and VE by aligning the operating voltage more closely with that of mesa-type n-p LEDs. Consequently, rectifying the issue of high operating voltages in planar p*-p LEDs enables the creation of efficient LEDs devoid of crystal defects resulting from mesa-etching processes.

Responsivity Surge in MAPbI3:PC61BM/Au/ZnO Sandwich‐Structured Photodetector

AbstractThe low gain in the presence of a single transverse external electric field limits the application of metal‐semiconductor‐metal (MSM) photodetectors. Here, a longitudinal built‐in electric field by spin‐coating CH3NH3PbI3:PC61BM on the electrode region of an Au/ZnO MSM photodetector, which constitutes a vertically crossed composite electric field with a transverse external electric field, is constructed. In this case, the transverse electric field collects the electrons, and the longitudinal electric field separates them. Based on this novel electric field structure, carrier multiplication at lower voltage conditions is achieved. Compared to the low voltage, there is a significant amplification effect when the voltage reaches 7 V. The responsivity is increased ≈270 times for UV–vis wavelengths, escalating from ≈0.02 to ≈5.4 A W−1. This study provides a novel carrier transport control scheme for high‐gain perovskite‐based photodetectors.

A novel two-stage continuous capacitive deionization system with connected flow electrode and freestanding electrode

The desalination of seawater/wastewater utilizing flow-electrode capacitive deionization (FCDI) has received significant interest. However, challenges like the low electrical conductivity of flow electrode and excessive energy consumption have prevented the scaling up of desalination operations. To overcome these issues, this study introduces a new FCDI system termed the two-stage FCDI (TS-FCDI) system, in which desalination modules are equipped with freestanding and flow electrode. The TS-FCDI system offers a graded desalination module design that produces an average salt removal rate (ASRR) of 113 µg cm2·min−1. However, the TS-FCDI system requires substantially reduced infrastructure investment, device size, and energy expenses. Notably, the design allows for the simultaneous operation of freestanding and flow electrode and enables the transport of ions and charges in the electrode region. Experimental evidence from multiple device configurations (CDI, FCDI, and TS-FCDI) supports this claim. Notably, the TS-FCDI system shows about twice the desalination performance over FCDI, with approximately 50 h of single-cycle (SC) operation. This enhancement links the freestanding electrode with the flow electrode, enabling the device to be well-suited for practical applications. The continuous flow of electrode particles in contact with the freestanding electrode initiates secondary ion transport, merging two different types of electrodes to enhance the active space of the electrode, effectively improving ion adsorption performance. In summary, the results of this study indicate the potential of the TS-FCDI system as a suitable desalination technology for scaling up applications.

Improvement of AlGaN/ GaN based HEMT with high performance rate for integrated circuit design for wide range of applications

In the current research work, we focused on the design and analysis of a semiconductor device called High-Elec-tron-Mobility Transistor (HEMT) based on the AlGaN/GaN material system. An Aluminum Nitride spacer,Layer of Nucle-ation along with cap as a AlGaN and barrier of GaN with the channel of AlGaN are incorporated to enhance HEMT device performance.The electrical characteristics of the proposed HEMT are an-alyzed. The Drain Current is found to be 0.18A/mm, indicating the device's ability to handle high current levels. The Electron Concentration is observed to have a maximum value of -96.12electrons/cm3 and varying based on the position in the channel for GaN Barrier thickness is 0.15mm. In the analysis of AC such as Gain of the Maximum Unilateral Power is deter-mined to be 83.41dB, indicating the ability of the device to am-plify signals. The Y-parameters, which characterize the de-vice's behavior at various frequencies of operation, are also de-termined. The capacitance between the electrode region Gate-Source (CGSMIN) is found to be 1.70×10^-11 F/mm, and alike The Capacitance between the electrode region the Gate-Drain Ca-pacitance (CGDMIN) is determined to be 4.7×10^-12 F/mm. Fur-thermore, an Electric Field of 96.51×10^3 V/mm is observed, in-dicating the strength of the electric field across the device. For HEMT device the simulation,The TCAD Silvaco software is be-ing practiced.

Thermal runaway and induced electrical failure of epoxy resin in high‐frequency transformers: Insulation design reference

AbstractSolid‐state transformers (SSTs) have applications in medium‐voltage direct current (MVDC) grids and compact power systems. High‐frequency transformer (HFT) is the core component of SSTs. High levels of high frequency high dv/dt voltage stresses challenged the integrity of the galvanic insulation of HFTs. However, dielectric thermal runaway and resultant electrical failure mechanisms in epoxy resin (EP) cast insulation remain unclear. Dielectric heating of EP across varying voltages, frequencies, rising edges, duty cycles and DC biases were measured and corroborated by simulation. The thermal runaway threshold mainly depends on the tangency point of the loss generation and heat dissipation curves below the glass transition temperature. Observations reveal that thermal runaway does not directly cause breakdown; instead, thermal decomposition above 200°C triggers discharge and eventual failure. Simulations demonstrate that temperature rise mainly depends on the average field within the electrode region and inter‐segment and inter‐layer distances within the HFT winding definitively impact insulation thermal runaway. By applying different criteria for MV and high‐voltage (HV) transformers, the reference electric fields for insulation design with unfilled and filled EP were obtained. For instance, limiting dielectric heating below 5 K at 50 kHz necessitates an RMS average field less than 0.44 V/mm, which is much lower than dry‐type transformer conventions. The authors prove the necessity of re‐evaluating the permissible field strength in HFT insulation design.

Coupling numerical simulation of plasma arc channel evolution and particle dispersion process

Arc discharge plasma (ADP) technology can be applied to disperse easily aggregated materials, such as the carbon nanotubes and Fe3O4. To investigate the evolution of the plasma arc channel and particle dispersion effect during the ADP process, a coupled electrode–plasma channel–workpiece (Fe3O4 clusters) and particle dispersion heat transfer model was established. The simulation results exhibited that the plasma arc formed at 0.05 s acted on the workpiece surface, forming a conical bottle-shaped structure with a wide arc column near the workpiece region and a narrow arc column near the electrode region due to the plasma column–workpiece interaction. With the continuous discharge, a discharge crater was formed on the workpiece surface due to the thermal-pressing effect of the plasma arc, and the dynamic pressure exerted by the arc column on the workpiece center increased continuously, driving the dispersion of the particles. In addition, ADP dispersion experiments were carried out on Fe3O4 to verify the simulation results. The experimental results showed that the morphologies of plasma arc channel evolution and discharge crater agreed with the simulation results. Moreover, the Fe3O4 particles dispersed by the ADP showed good dispersion morphology, which will further promote the spread of ADP technology in the dispersion and application of materials.

Somatic Mosaicism in PIK3CA Variant Correlates With Stereoelectroencephalography-Derived Electrophysiology.

Brain-limited pathogenic somatic variants are associated with focal pediatric epilepsy, but reliance on resected brain tissue samples has limited our ability to correlate epileptiform activity with abnormal molecular pathology. We aimed to identify the pathogenic variant and map variant allele fractions (VAFs) across an abnormal region of epileptogenic brain in a patient who underwent stereoelectroencephalography (sEEG) and subsequent motor-sparing left frontal disconnection. We extracted genomic DNA from peripheral blood, brain tissue resected from peri-sEEG electrode regions, and microbulk brain tissue adherent to sEEG electrodes. Samples were mapped based on an anatomic relationship with the presumed seizure onset zone (SOZ). We performed deep panel sequencing of amplified and unamplified DNA to identify pathogenic variants with subsequent orthogonal validation. We detect a pathogenic somatic PIK3CA variant, c.1624G>A (p.E542K), in the brain tissue samples, with VAF inversely correlated with distance from the SOZ. In addition, we identify this variant in amplified electrode-derived samples, albeit with lower VAFs. We demonstrate regional mosaicism across epileptogenic tissue, suggesting a correlation between variant burden and SOZ. We also validate a pathogenic variant from individual amplified sEEG electrode-derived brain specimens, although further optimization of techniques is required.

A 2.8 kV Breakdown Voltage α-Ga2O3 MOSFET with Hybrid Schottky Drain Contact.

Among various polymorphic phases of gallium oxide (Ga2O3), α-phase Ga2O3 has clear advantages such as its heteroepitaxial growth as well as wide bandgap, which is promising for use in power devices. In this work, we demonstrate α-Ga2O3 MOSFETs with hybrid Schottky drain (HSD) contact, comprising both Ohmic and Schottky electrode regions. In comparison with conventional Ohmic drain (OD) contact, a lower on-resistance (Ron) of 2.1 kΩ mm is achieved for variable channel lengths. Physics-based TCAD simulation is performed to validate the turn-on characteristics of the Schottky electrode region and the improved Ron. Electric-field analysis in the off-state is conducted for both the OD and HSD devices. Furthermore, a record breakdown voltage (BV) of 2.8 kV is achieved, which is superior to the 1.7 kV of the compared OD device. Our results show that the proposed HSD contact with a further optimized design can be a promising drain electrode scheme for α-Ga2O3 power MOSFETs.