Capacitance Characteristics Research Articles

Characterization of newly developed large area SiC sensors for the NUMEN experiment

First prototypes of large area, p–n junction, silicon carbide (SiC) detectors have been produced as part of an ongoing programme to develop a new particle identification wall for the focal plane detector of the MAGNEX magnetic spectrometer, in preparation for future NUMEN experimental campaigns. First characterizations of sensors from two wafers obtained with epitaxial silicon carbide growth and with different doping concentration are presented. Current (I–V) and capacitance (C–V) characteristics are investigated in order to determine the full depletion voltage and the doping profile. Radioactive α-sources are used to measure the energy resolution and estimate the depletion depth.

Enhanced Crystallinity of SrTiO3 Films on a Silicon Carbide Substrate: Structural and Microwave Characterization

Thin films of strontium titanate, which reveal high structure quality and tunable properties prospective for microwave applications at room temperature, were grown on a semi-insulating silicon carbide substrate using magnetron sputtering for the first time. The films’ growth mechanisms were studied using medium-energy ion scattering, and the films’ structures were investigated using X-ray diffraction. The electrical characteristics of planar capacitors based on strontium titanate films were measured at a frequency of 2 GHz using a high-precision resonance technique. It is shown that the tendency to improve the crystalline structure of strontium titanate film with an increase in the substrate temperature is most pronounced for films deposited at elevated working gas pressure under low supersaturation conditions. Planar capacitors formed on the basis of oriented SrTiO3 films on silicon carbide showed tunability n = 36%, with a loss tangent of 0.008–0.009 at a level of slow relaxation of capacitance, which is significantly lower than the data published currently regarding planar tunable ferroelectric elements. This is the first successful attempt to realize a planar SrTiO3 capacitor on a silicon carbide substrate, which exhibits a commutation quality factor more than 2500 at microwaves.

Improved photocatalytic activity triggered by UV light, as well as electrochemical sensing characteristics of MgO nanoparticles

ABSTRACT The current study’s objective was to investigate the potential applications of synthesised magnesium oxide nanoparticles (MgO NPs) as green fuel through solution combustion with leaves of tulsi (holy basil). The end product was further calcined for 3 h at 800°C to produce a well-crystalline nanomaterial. Transmission electron microscopy (TEM) examinations indicated a typical crystallite size of approximately 52 nm, determined by applying Scherer’s formula. The results from the scanning electron microscope (SEM) revealed a morphology that is clumped, puffy, and porous. The energy band gap (Eg) values for MgO NPs were determined to be 4.31 eV using DRS data, verifying the semiconductor behaviour of the NPs. Degradation experiments were conducted on two dyes, Fast Blue (FB) and Fast Orange (FO), exposed to UV light for 90 minutes. Under UV light, the photocatalytic degradation of FO (80.35%) and FB (80.5%) reached their maximum. A graphite paste electrode was used for cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and sensor investigations. The cyclic CVs of the MgO NPs-modified graphite paste electrode in 0.1 M NaOH were scanned at 10 to 50 mV/s to determine the specific capacitance values of 250.3 Fg−1. Based on the acquired EIS data, the MgO NPs used as the electrode displayed pseudocapacitive capacitor characteristics. Further, the proposed sensor was employed to determine the Pb2+ and Li+ ions in water and showed sensitivity in the order of 0.005 and 0.006 A. Therefore, MgO NPs synthesised via green solution combustion may have excellent applications as photocatalysts and electrochemical sensors.

Impact of voltage and frequency on electrical characteristics of MIS capacitors with triphenylamine layer

This study examines the effect of triphenylamine (TPA) interlayers on the electrical properties of Al/TPA/p-Si metal-interlayer/insulator material-semiconductor (MIS) capacitors. Using Gaussian software, TPA molecular structure was optimized, and HOMO-LUMO energy levels were simulated. Capacitance-conductance-voltage (C-G-V) measurements were performed at room temperature over −4 V to +4 V and 50 kHz–700 kHz. AFM and SEM analysis showed TPA films were smooth with a uniform thickness of about 178 nm. The C-V characteristics revealed a frequency-dependent decrease in capacitance, indicating a continuous distribution of interface states. Barrier height (ΦB) increased from 0.305 eV at 50 kHz to 0.655 eV at 700 kHz, while the active interface trap density (Dit) decreased from 6.73 × 1012 eV−1 cm−2 to 3.23 × 1011 eV−1 cm−2. Additionally, the accumulating region exhibited low series resistance values (between 6.88 and 8.44 Ω). These results suggest that TPA thin films are effective for MIS capacitors.

Application of ion modification for alteration of anode materials based on ZnO/CoZn nanostructures

During the conducted studies, it was established that the use of ion modification by irradiation with O+ and Ar+ ions makes it possible to elevate the degradation resistance of anode materials due to the effect of vacancy defect creation, the density of which varies with the irradiation fluence. At the same time, the analysis of changes in the band gap and the optical density value, expressing changes in structural distortions, revealed that ion irradiation leads to a rise in the stability of the preservation of electronic properties during long-term resource tests, which are inextricably linked with the degradation of ZnO/CoZn nanostructures due to oxidation processes as a result of lithiation. During assessment of changes in the parameters of the band gap and optical density of the samples after resource tests, it was found that the observed growth in these indicators is due to oxidation processes and partial amorphization due to the formation of oxide inclusions in the structure of nanowires, the presence of which is due to the interaction of nanostructures with the electrolyte over a long period of time during charging/discharging, which results in near-surface layer degradation due to the introduction of oxygen, and in the case of a long service life, to the formation of oxide inclusions that elevate the density of defects and vacancies in the structure. According to tests of synthesized ZnO/CoZn nanostructures as anode materials, it was found that the use of O+ and Ar+ ions not only leads to a growth in the degradation resistance of capacitive characteristics during long-term tests, but also to the stability maintenance of indicators with a reversible decrease in the charging rate at charging rate variation.

Effect of Carbon Nanotubes Functionalization on the Chemical Composition and Electrochemical Characteristics of Composites with Layered Potassium Manganese Oxide

The influence of pretreatment of multiwalled carbon nanotubes (MWCNTs) in oxidizers (solutions of H2O2 and HNO3) on the structure and electrochemical properties of composites with layered potassium-manganese oxide (KxMnO2) was studied. Composites were obtained by soaking carbon nanotubes in an aqueous solution of KMnO4 at 60 °C. The electrochemical performance of the composites was evaluated by cyclic voltammetry and galvanostatic charge‒discharge methods. It has been established that stronger oxidation of the MWCNTs surface at the functionalization stage leads to a noticeable increase in the reaction rate as well as the optimal potassium content in the KxMnO2 composition, which provides higher capacitive characteristics of the composite (a maximum specific capacitance of 150 F g−1 and a rate capability of 43% with increasing density current from 0.1 to 2.0 A g−1). The resulting composites are promising active components for increasing the capacitive characteristics of conductive carbon black (CB). Compared with an electrode based only on CB, electrodes based on a combination of the composite and CB at a mass ratio of 1:1 showed specific capacitance values approximately 1.5 to 3 times greater, as well as a twofold increase in rate capability (from 35 to 70%) in the range of discharge current density 0.1 to 2.0 A g−1.

Direct Measurement of the Differential Capacitance of Deep Eutectic Solvents on Platinum and Glassy Carbon Electrodes.

Differential capacitance is a crucial parameter that connects the experimental observation of electrical double-layer behavior with theoretical models. However, the current number of reported differential capacitance values for deep eutectic solvents remains limited, making it challenging to verify or refute existing models. In this study, we systematically investigate the differential capacitance in deep eutectic solvents using chronoamperometry. By comparing metal and glassy carbon electrodes across various liquid combinations and ion concentrations, we observed a range of distinct capacitance characteristics. While some findings align with the existing mean-field model for ionic liquids, others clearly reflect the influence of electrode materials, with certain cases resisting full explanation by current theoretical models. These results underscore the importance of selecting appropriate electrode materials in experimental studies of such electrolytes and highlight the need for further theoretical advancements in understanding this complex liquid system.

Effect of strain gradient and interface engineering on the high-temperature energy storage capacitors

The miniaturization and high integration of electronic devices pose new requirements for the energy storage density and high-temperature performance of dielectric capacitors. For thin film materials, internal stress and the interface layer often show a significant impact on their energy storage performance. Therefore, the capacitors with different stress gradient sequences and different periods were designed by BaHf0.17Ti0.83O3 (BHTO17), BaHf0.25Ti0.75O3 (BHTO25), and BaHf0.32Ti0.68O3 (BHTO32) to investigate the effect of stress gradient and interface engineering on the energy storage characteristics. Dielectric thin film structures with upward gradient, downward gradient, and periodic upward gradient (4N) were constructed. The study found that the upward gradient structure had higher breakdown field strength than the downward gradient structure. This is because the upward gradient structure can effectively extend the ending electric field of the Ohmic conduction mechanism and delay the activation electric field of the F–N tunneling mechanism. The 4N structure had a slightly higher breakdown field strength (reaching 9.22 MV/cm) compared to the pure upward gradient structure. The 4N structure thin film also exhibited higher energy storage density (115.44 J/cm3) and wide temperature (−100 to 400 °C) characteristics. These findings provide important guidance and application value for improving the energy storage characteristics of dielectric capacitors at high temperatures through structural design.

Carbonized porous zeolitic imidazolate framework as promising electrode for electrochemical supercapacitors

In order to manufacture effective supercapacitors with improved electrochemical performance, it is imperative to investigate greater surface area electrode materials. This work describes the development of a cost-effective method for the carbonization of porous zeolitic imidazole framework (ZIF8) to utilize as electrode of electrochemical supercapacitors. The electrode materials were prepared by synthesizing highly porous ZIF8-P followed by pyrolysis at 500 °C (ZIF8-P-500). The pyrolysis of ZIF-8 significantly strengthened the porous behavior by maintaining their hexagonal particles and obtaining high surface to volume ratio. The measurements using constant current charge/discharge (GCD) and cyclic voltammetry (CV) were used to evaluate the electrochemical capacitance characteristics of the synthesized ZIF8-P based electrode. The supercapacitor assembly using the optimized ZIF8-P electrode exhibited a high specific capacitance of ∼423.9 Fg–1 with exceptional cycle stability by maintaining capacitance of ∼86.7 % from its initial capacitance after 5000 cycles. Thus, the results indicate that the ZIF8-P based supercapacitor offers a compelling path for creating porous carbon electrodes from MOFs using low cost pyrolysis for advancing supercapacitor technology.

Coaxial direct writing of ultra-strong supercapacitors with braided continuous carbon fiber based electrodes

Supercapacitors produced based on 3D printing technology greatly expand the range of materials and geometric complexity. However, the production of fiber-based supercapacitors typicallyrequires subsequent steps. For the first time, we report a coaxial direct writing technique that enables the one-step fabrication of braided flexible solid-state supercapacitors. Continuous carbon fiber is used as a flexible substrate. α-manganese dioxide nanowires and activated carbon are used as active materials. The entire electrode assembly is coated with solid-state electrolyte and then braided. Through coaxial direct writing technology, the braided electrodes and sealings can be extruded by a coaxial nozzle to continuously print free-form ultra-strong supercapacitors with a tensile strength of the braided electrodes up to 636 MPa. Electrochemical measurement results show that the printed capacitor exhibits an excellent specific capacitance, and it still maintains a capacitance retention of 90.1% after 1000 cycles. The supercapacitor exhibits nearly identical electrochemical capacitive characteristics at various bent angles. This work paves the way for integrating enhanced durability and adaptability into next-generation wearable and portable electronic systems.

Low-voltage organic field-effect transistors by using solution-processable high-κ inorganic-polymer hybrid dielectrics

Organic field-effect transistors (OFETs) incorporating hybrid high-κ inorganic Al2O3 and polymer dielectrics, including polyvinyl alcohol (PVA), polystyrene (PS), or polymethyl methacrylate (PMMA), through solution-processing techniques were fabricated. The analyses revealed that the high surface energy and hydrophilicity property of Al2O3 and PVA, and the relatively hydrophobic property of PS surface, hindered the performance of corresponding OFETs. The Al2O3/PMMA-based OFET achieved the optimized performance, with a threshold voltage of −2.7 V, a hole carrier mobility of 0.056 cm2/Vs, and a current on/off ratio of 1.0 × 104 at a low operating voltage of −5 V. Through analyzing the characteristics of leakage current, capacitance, contact resistance, and trap density of OFETs, we found that the PMMA-engaged films possessed the optimized electrical properties. The introduction of PMMA eliminated the interfacial trapping, thereby lowering the threshold voltage and enhancing the performance of the device. The COMSOL Multiphysics simulation was conducted to confirm the physical mechanism. The strategy of utilizing Al2O3/PMMA hybrid dielectric could simultaneously ensure the low operating voltage and good performance of OFET, while guaranteeing the low leakage current by the thick PMMA.

Ta-ions doping impact on structural modifications and bandgap tuning of NiCo2O4 hexagonal nanosheets for high rated pseudocapacitor electrodes

Getting higher activity, lower cost and especially better stability at the same time is still one of the biggest problems in the supercapacitors research. Morphology tailoring and crystal imperfections induce d due to doping based defects in ternary transition metal oxides at the nano-scale level is crucial for enhancing the performance of supercapacitors. This research investigates of the utilization of Ta-doped NiCo2O4 (Ta-NCO) hexagonal nano-sheets for supercapacitor electrodes. The structural and morphological study of pristine and Ta-doped samples has been determined using XRD, SEM, TEM and HRTEM. The enhanced inherent conductivity and diffusion at the interface are also confirmed using electrochemical measurements study. The NCO-5 material exhibits a notable enhancement in capacitance and cycling retention. The NCO-5 electrode demonstrates a high specific capacitance (Cs) of 2445.7 F/g at 1 A/g. The pseudocapacitive behavior by power law (b = 0.67) and an increase in capacitive contribution with the scan rate reaching a value of 47.2 % at 100 mV/s by Dunn method exhibits it suitability of pseudocapacitors. The low Rct value signifies it improved capacitive performance as deduced from EIS measurements. Crucially, it maintains around 95.3 % of its capacitance after undergoing 10,000 GCD cycles. The high specific capacitance, remarkable capacitive characteristics and high stability of NCO-5 make it an excellent contestant for supercapacitor applications. The fabricated asymmetric supercapacitor (NCO-5//AC) shows exceptional energy density (ED) of 96.35 Wh/kg with power density (PD) of 825.03 W/kg.

Conjugated Matrix Nanocomposites with Nanodiamond Nanoadditives—Fundamentals and Forefronts

Nanodiamonds have been researched as sphere-shaped carbon nano-entities having countless surface/structural properties, facile fabrication and mammoth technological value. An important utilization of nanodiamonds has been observed as nano-reinforcing agents for nanocompositing purposes. Semiconducting polymers (conjugated polymers) having π electron delocalization have been documented for worthy electrochemical/optical/thermal/mechanical features, in addition to the electron transfer through their backbone. Doping of carbonaceous nanoparticles, like nanodiamonds, with conjugated polymers have been found to further improve the valuable physical characteristics in their final nanocomposite form. Correspondingly, this overview describes the impact of nanodiamond nano-reinforcement on the specialized aspects of polyaniline/nanodiamond, polypyrrole/nanodiamond and polythiophene/nanodiamond nanocomposites. According to literature reports, these groupings of conjugated polymer/nanodiamond hybrids revealed noteworthy microstructural, conductive, optical, electrochemical, microwave absorption, specific capacitance, photovoltaic and actuation characteristics. Subsequently, several significant applications of polymer/nanodiamond nanomaterials have been explored including the solar cells, supercapacitors and actuators.

Operator-Based Triboelectric Nanogenerator Power Management and Output Voltage Control.

In this paper, an operator-based voltage control method for TENGs is investigated, achieving output voltage tracking without compensators and uncertainty suppression using robust right coprime factorization. Initially, a comprehensive simulation-capable circuit model for TENGs is developed, integrating their open-circuit voltage and variable capacitance characteristics. This model is implemented to simulate the behavior of TENGs with a rectifier bridge and capacitive load. To address the high-voltage, low-current pulsating nature of TENG outputs, a storage capacitor switching model is designed to effectively transfer the pulsating energy. This switching model is directly connected to a buck converter and operates under a unified control strategy. A complete TENG power management system was established based on this model, incorporating an operator theory-based control strategy. This strategy ensures steady output voltage under varying load conditions without using compensators, thereby reducing disturbances. Simulation results validate the feasibility of the proposed TENG system and the efficacy of the control strategy, providing a robust framework for optimizing TENG energy harvesting and management systems with significant potential for practical applications.

Simulation of synaptic properties of ferroelectric memory capacitors and neural network applications

In this work, the electrical properties and synaptic characteristics of hafnium oxide-based ferroelectric memory capacitor with metal - ferroelectric layer - metal (MFM) structure were simulated using TCAD (technology computer aided design) software. Based on the synaptic potentiation/depression characteristics of the simulated memory capacitor, a multilayer perceptron (MLP) network was constructed, and the recognition accuracy and convergence speed of the MLP network in the MNIST recognition task were simulated, and the feasibility of the ferroelectric memory capacitor synaptic device for real neural network operation was analyzed. The results show that the recognition accuracy of the MLP network reaches 93% and stabilizes after 50 iterations of training, and the recognition accuracy of the MLP network is already at a high usable level after a smaller number of training times of 20, which suggests that the synaptic plasticity of the ferroelectric memory capacitor has a good potential for the practical application of the weight updating of the MLP network.

Frequency-dependent capacitance and conductance characteristics and current transport mechanisms of Schottky diodes with TPA-IFA organic interfacial layer

In this study, a Schottky barrier diode with an Al/TPA-IFA/p-Si structure was fabricated using spin coating and thermal evaporation methods. Using forward and reverse bias I–V measurement, we examined the key electrical characteristics of the Al/TPA-IFA/p-Si diode, including Φb, n, Rs, and Nss; we also estimated VD, NA, EF, ∆Φb, WD, Φb and Nss using C–V measurements under the different frequencies (10, 50, 100, 500 kHz, and 1 MHz) at room temperature. Using I–V data and the Thermionic Emission (TE) theory, basic electrical parameters such as ideality factor ( n ), and barrier height ( Φb ) values were computed as 3.01 and 0.716 eV. The fundamental diode parameters are highly frequency-dependent. It was also found that the series Resistance ( Rs ) values reduced with increasing frequency, but the barrier height ( Φb ) and the width of the depletion layer ( WD ) increased. It was found that when frequency increased, the diode capacitance reduced for our new Schottky-type diode. The diode’s potential conduction mechanisms were examined through the utilization of reverse lnI−V0.5 and forward lnI−V graphs. The transport properties of Al/TPA-IFA/p-Si diode are primarily governed by ohmic conduction, Space Charge Limited Current (SCLC), and Trap Charge Limited Current (TCLC) mechanisms at low, moderate, and high voltages, respectively. It was concluded that the Poole–Frenkel Emission (PFE) mechanism was dominant for the Al/TPA-IFA/p-Si diode. Ultimately, the findings confirmed that the TPA-IFA-based diode could be obtained for the electronic application.

Increasing of efficiency of hydrogen energy storage system by the use of high-pressure electrolyser with metal hydride electrode

The article describes the electrochemical process of hydrogen and oxygen generation by a membrane-less electrolyser having a passive electrode made of Ni and a gas absorption electrode made of metal hydride (LaNi5Hx). Such composition of the electrode stack materials (Ni - LaNi5Hx) makes it possible to generate hydrogen and oxygen during the half-cycles separately in time while maintaining the time intervals of the corresponding half-cycles. The last one indicates the stable capacitive characteristics of the LaNi5Hx metal hydride electrode. During the oxygen half-cycle, hydrogen is absorbed in the metal hydride electrode while oxygen is released at the nickel electrode and then removed into the oxygen storage system. During the subsequent half-cycle, the hydrogen absorbed by the metal hydride electrode is removed into the hydrogen storage system. We have studied the above electrolysis process with help of the laboratory experimental membrane-less electrolyser giving the possibility for generating, storing and compressing hydrogen in it. The use of a chemically active LaNi5Hx electrode will make it possible to implement a hydrogen energy storage system (electrolyser-storage system-consumer) and accordingly to increase the efficiency of the power plant by ≈ 8–10 %. It would be effective to use such high-pressure membrane-less electrolyser as an energy storage system element of an energy complex that receives electricity from the renewable energy sources (sun, wind).

Impact of Oxide Charges on The Minority Carrier Response in MOS(p) Devices With Al2O3/SiO2 Gate Stacks under Strong Inversion Condition

Admittance measurement, including capacitance and conductance, is very useful to analyze the electrical characteristics of metal-oxide-semiconductor (MOS) systems. These techniques offer insights into various device properties, including interface trap density and minority carrier lifetime in the substrate. It is essential to note that, apart from the gate area, the oxide region beyond the device could significantly influence measurement results [1]-[2]. In this work, a compact model proposed in [3] was used to clarify an unusual minority carrier response time observed in experimental data. The results proved the heightened sensitivity of device alternating current (AC) characteristics to oxide charges in the outer region. Additionally, the dependencies of oxide thickness and quality on the transition frequency (ωm) of devices were explored.The MOS (Al/AlOx/SiO2/p-Si) structure illustrated in Fig. 1 was employed in this study. Aluminum oxide region is under the gate electrode, while silicon oxide (SiO2) covers the entire wafer. Table 1 summarizes samples (S1 to S5) with consistent aluminum oxide thickness but diverse SiO2 thickness. Fig 2. shows the process flow and the anodic oxidation (ANO) system. By tilting the wafer at a specific angle during ANO, a high-quality SiO2 layer with different thicknesses on a single wafer could be obtained. Fig 3(a) to (d) illustrate the capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics of devices with varying SiO2 thicknesses. All devices exhibit low-frequency capacitance characteristics in strong inversion regions with thickness-dependent minority carrier response, particularly at 10kHz. Additionally, devices show different thicknesses depending on G-V characteristics at 1MHz and 10kHz. Fig 4(a) and (b) illustrate the Cinv/Cox ratio for varied oxide thicknesses and Gm/ω characteristics under strong inversion bias (VG = +3V). Gm means the measurement conductance. Following established research [3], peak Gm/ω magnitudes would occur at ωm. Table 2 reveals microsecond-range response times (τR) at ωm, considerably faster than conventional silicon minority carrier lifetimes (usually 1 ms to 100 ms). Moreover, decreasing oxide thickness shifts the ωm toward lower values.To explain this observed phenomenon, the environment outside the devices should be taken into consideration. Fig 5(a) and (b) show the schematic diagram and AC signal model proposed in [1] and [2]. Oxide charges in the outer region would deplete majority carriers and invert the p-type silicon surface to an n-type inversion layer. As a result, the lateral depletion region (Cd, out) and conductive channel (Rs) are formed outside the device, which are functions of substrate doping concentration and the effective oxide charges. The detailed model derivation is discussed in [2]. For this reason, an AC signal applied on the gate would extend outside the device for about a millimeter to a micrometer, affecting measuring results. Based on the model, the effective charges in the SiO2 could be extracted by measuring results. The thicker oxide has more oxide charges, as shown in Fig 6(a). Fig 6(b) and (c) show the modeling results of the Cinv/Cox ratio versus different oxide thicknesses and the Gm/ω-ω plot, which are very close to the experimental results. By simplifying the conductance formula (Gm), Gm reveals an inverse proportional to lateral effective conductance (GLeff) at low frequency (e.g., 10 kHz) and a direct proportional at high frequency (e.g., 1 MHz). Thicker SiO2 devices possess more oxide charges, leading to a greater lateral coupling effect, resulting in a greater GLeff compared to thinner devices. This elucidates the observed variations in Gm-V characteristics at 1 MHz and 10 kHz. Figures 7(a) and (b) display TCAD-simulated C-V and ωm for devices with varying oxide charge densities, confirming that minor changes in oxide charges result in noticeable differences in minority carrier responses in the strong inversion region. Fig 8(a) and (b) show the TCAD simulated results for devices with low doping substrate. For low doping substrates, oxide charges play a much more important role under AC operation.In summary, the study established a correlation between oxide charge densities and thicknesses. The origin of the faster minority carrier response and the peak shift in Gm/ω- ω plot were thoroughly explained and validated by TCAD simulation. Oxide charges were found to play a crucial role, especially in low-doping substrates, offering insights for advanced IC fabrication.[1] E. H. Nicollian and A. Goetzberger, IEEE Transactions on Electron Devices, vol. 12, no. 3, pp. 108-117, 1965.[2] K. C. Chen, K. W. Lin, S. W. Huang, J. Y. Lin, and J. G. Hwu, IEEE Journal of the Electron Devices Society, vol. 10, pp. 960-969, 2022.[3] S. Monaghan et al., IEEE Transactions on Electron Devices, vol. 61, no. 12, pp. 4176-4185, 2014. Figure 1

Corrosion and Interfacial Contact Resistance of NiTi Alloy as a Promising Bipolar Plate for PEMFC.

Titanium (Ti) is generally considered as an ideal bipolar plate (BPP) material because of its excellent corrosion resistance, good machinability and lightweight nature. However, the easy-passivation property, which leads to increased interfacial contact resistance (ICR) and subsequently decreased cell performance, limits its large-scale commercial application in proton exchange membrane fuel cells (PEMFCs). In this paper, we proposed a NiTi alloy prepared by suction casting as a promising bipolar plate for PEMFCs. This NiTi alloy exhibits significantly decreased ICR values (16.8 mΩ cm2 at 1.4 MPa) compared with pure Ti (88.6 mΩ cm2 at 1.4 MPa), along with enhanced corrosion resistance compared with pure nickel (Ni). The superior corrosion resistance of NiTi alloy is accredited to the nobler open circuit potential and corrosion potential, coupled with low corrosion current densities and passive current densities. The improved ICR can be interpreted by the existence of high-proportioned metallic Ni in the passive film, which contributes to the reduced capacitance characteristic of the passive film (compared with Ti) and enhances charge conduction. This work provides a feasible option to ameliorate BPP material that may have desirable corrosion resistance and ICR.

WSe2 Negative Capacitance Field-Effect Transistor for Biosensing Applications.

Field-effect transistor (FET) biosensors based on two-dimensional (2D) materials are highly sought after for their high sensitivity, label-free detection, fast response, and ease of on-chip integration. However, the subthreshold swing (SS) of FETs is constrained by the Boltzmann limit and cannot fall below 60 mV/dec, hindering sensor sensitivity enhancement. Additionally, the gate-leakage current of 2D material biosensors in liquid environments significantly increases, adversely affecting the detection accuracy and stability. Based on the principle of negative capacitance, this paper presents for the first time a two-dimensional material WSe2 negative capacitance field-effect transistor (NCFET) with a minimum subthreshold swing of 56 mV/dec in aqueous solution. The NCFET shows a significantly improved biosensor function. The pH detection sensitivity of the NCFET biosensor reaches 994 pH-1, nearly an order of magnitude higher than that of the traditional two-dimensional WSe2 FET biosensor. The Al2O3/HfZrO (HZO) bilayer dielectric in the NCFET not only contributes to negative capacitance characteristics in solution but also significantly reduces the leakage in solution. Utilizing an enzyme catalysis method, the WSe2 NCFET biosensor demonstrates a specific detection of glucose molecules, achieving a high sensitivity of 4800 A/A in a 5 mM glucose solution and a low detection limit (10-9 M). Further experiments also exhibit the ability of the biosensor to detect glucose in sweat.