Contact Resistance Research Articles

Inkjet-Printed, High-Performance MoS2 Transistors and Unipolar Logic Electronics.

Two-dimensional (2D) semiconductor field-effect film transistors combine large carrier mobility with mechanical flexibility and therefore can be ideally suitable for wearable electronics or at the sensor interfaces of smart sensor systems. However, such applications require large-area solution processing as opposed to single-flake devices, where the critical challenge to overcome is the high interflake resistance values. In this report, using a narrow-channel, near-vertical transport device architecture, we have fabricated inkjet-printed sub-20 nm channel electrolyte-gated transistors with predominantly intraflake carrier transport. Therefore, the electronics transport in these transistors is not dominated by the high interflake resistance, and the intraflake material properties including doping density, defect concentration, contact resistance, and threshold voltage modulation can be examined and optimized independently to achieve a current density as high as 280 μA·μm-1. In addition, through the passivation of the sulfur vacancies with a tailored surface treatment, we demonstrate an impressive On-Off current ratio exceeding 1 × 107, complemented by a low subthreshold swing of 100 mV·decade-1. Next, exploiting these high-performance transistors, unipolar depletion-load-type inverters have been fabricated that show a maximum gain of 31. Furthermore, we have realized NAND, NOR, and OR gates, demonstrating their seamless operation at a frequency of 1 kHz. Therefore, this work represents an important step forward to realize electronic circuits based on printed 2D thin film transistors.

Solution process of graphene-induced ohmic contact between the metal and AlGaN/GaN for hemts application

This work demonstrates an AlGaN/GaN high electron mobility transistor (HEMT) with Cr/Graphene ohmic contacts constructed without heat treatment. The Cr/Graphene ohmic contact was fabricated using a spray-coated graphene nanoflakes solution and electron-beam-evaporated Cr. This method does not require a high-temperature annealing step in conventional Ti/Al/Ni/Au ohmic contact. It is suggested that the Cr/graphene combination acts similarly to a doped n-type semiconductor in contact with AlGaN/GaN heterostructures, enabling carrier transport to the AlGaN layer. The investigated Au/Cr/ Graphene/AlGaN/GaN HEMT device exhibits ohmic drain characteristics in the range of -4 V to 4 V of drain-source voltage with a calculated contact resistance density of 2.5 mΩcm2. Our results have important implications for the fabrication and manufacturing of AlGaN/GaN-based microelectronic and optoelectronic devices/sensors of the future.

A numerical study on heat transfer for serpentine-type cooling channels in a PEM fuel cell stack

The aim of this work is to analyse numerically the heat transfer for serpentine-type cooling channels in a PEM fuel cell stack. The effect of the coolant type, the flow rate, the inlet temperature, the presence of the thermal contact resistance and the gas diffusion layer, the bipolar plate material and the cooling channels design was studied with CFD simulations in a 100 cm2 active area cell with serpentine cooling channels to analyse the refrigeration capability of a PEMFC stack. A novel correlation for the Nusselt number is presented. The originality of the proposed correlation lies in the fact that it can be used for a comprehensive range of operating conditions, coolant fluids and bipolar plate materials, assessing the influence of those variables on the temperature distributions within the cell. Results of this study determined that mass flow and the bipolar plate thermal conductivity presented a higher effect on the refrigeration capability of a PEMFC stack. Results obtained in terms of the Uniform Temperature Index showed that values above 3.65 % lead to temperature differences in the membrane higher than 5 K, which could cause degradation problems.

Flexible hexagonal boron nitride@liquid metal/polydimethylsiloxane composites with excellent thermal conductivity and superior mechanical properties

AbstractHexagonal boron nitride (h‐BN) has a layered lattice structure, high intrinsic thermal conductivity, and good chemical stability, and it has a promising applications in thermal management materials. However, poor interfacial compatibility and dispersion of BN flakes in the polymer matrix cause thermal contact resistance and gaps, directly impairing the performance of the composites and limiting their thermal conduction applications. Herein, the P‐BN@LM/PDMS thermally conductive composites with superior mechanical properties were fabricated by incorporating dopamine and liquid metal (LM) into BN flakes. The dopamine self‐polymerizes to form polydopamine (PDA) on the BN surface, denoted as P‐BN, which effectively improves interface compatibility and dispersion. The LM attaches to the functionalized P‐BN surface by mechanical grinding, acting as a bridge between adjacent BN flakes to enhance the integrity of the thermal conductive network within the composites. The coordination between P‐BN and LM increases interface strength, effectively improving mechanical performance. Hence, the P‐BN@LM/PDMS composites exhibit excellent thermal conductivity (4.0 W/mK) and an enhancement factor of 1373%, which is 2.22 times that of BN/PDMS composites with the same 30 wt% loading. Additionally, the composite shows superior tensile strength (2.11 MPa) and elongation at break (121%), representing 441% and 203% improvements compared with pure polydimethylsiloxane (PDMS). The P‐BN@LM/PDMS composites, with significant advantages in thermal conductivity and mechanical properties, are promising for future applications as flexible thermal interface materials in thermal management.Highlights The P‐BN@LM/PDMS composites exhibit excellent thermal conductivity (4.0 W/mK) and an enhancement factor of 1373%, making them promising for future applications as flexible thermal interface materials in thermal management. The P‐BN@LM/PDMS composites present a superior tensile strength (2.11 MPa) and elongation at break (121%). PDA formed by the self‐polymerization of dopamine on the BN surface effectively enhances interfacial compatibility and dispersion. LM attaches to the functionalized BN surface through mechanical grinding, acting as a bridge between adjacent BN flakes, thus enhancing the integrity of the thermal conductive network within the composites.

Dual conductive network enables mechanically robust polymer composites with highly electrical and thermal conductivities

Thermally and electrically conductive polymer composites (CPCs) have been widely used in smart and flexible electronics; however, huge challenges remain in simultaneously improving the electrical and thermal conductivity of CPCs while maintaining the satisfactory mechanical properties including sufficient strength and toughness. In this study, we propose an effective interfacial regulation approach to fabricate CPCs with a dual conductive network through decoration of Ag nanoparticles (AgNPs) onto the polyurethane (PU) nanofibers containing graphite nanoplatelets (GNPs), followed by hot-pressing. Rigid GNPs expand the PU nanofiber network, facilitating Ag precursor adsorption, while subsequent hot-pressing eliminates the big channels and pores inside nanofiber composite membranes and hence greatly enhance their mechanical properties. After hot-pressing, the synergistic dual conductive network with greatly reduced thermal and electrical contact resistance leads to significant improvements in both thermal and electrical conductivity (up to 27.71 W (m K)−1 and 1.87 × 106 S/m, respectively). Moreover, the mechanically robust CPCs with exceptional durability possess superior Joule heating performance at low voltages and heat dissipation capability. This study provides inspiration for designing highly thermally and electrically conductive CPCs with potential applications as flexible thermal interface materials.

Effect of the contact load and rotation speed on the formation of rolling current-carrying arc and the corresponding material damage

The current-carrying arc is a critical factor that affects the electrical contact performance and material damage of contact pairs. In this study, a copper disk–copper disk pair was used to simulate the rolling electrical joint in a conductive rotating joint. Under operating conditions with a current of 2 A, rotation speeds from 4 to 600 r/min, and loads from 40 to 180 N, the dynamic behavior of the current-carrying arc and the surface damage mechanism were investigated. The movement characteristics of the arc at the friction interface were observed, and the arc generation difficulty and intensity were statistically analyzed based on the arc burning rate and arc energy. With increasing load and rotation speed, the generation of current-carrying tribological arcs became easier, and both the arc burning rate and arc energy increased. After the arc was generated, the arc root position was randomly distributed at the contact interface, exhibiting dynamic phenomena such as splitting and merging. Following the generation of the arc, the dominant damage mechanism at the current-carrying friction interface transitioned from mechanical damage to electrical damage. The manifestations of electrical damage included burning, oxidation, and roughening, with the degree of electrical damage positively correlated with the arc burning rate and arc energy. Surface oxidation could reduce the adhesion between metal contact pairs, contributing to a decrease in the current-carrying friction coefficient. Simultaneously, the film resistance caused by oxidation and the contraction resistance caused by roughening could lead to an increase in the average contact resistance.

Effect of the deposition sequence of Ti and W on the Ni-based Ohmic contacts to n-type 4H-SiC

The paper investigated the deposition sequence-dependent behavior of Ni (50 nm)/Ti (60 nm)/W (60 nm) and Ni (50 nm)/W (60 nm)/Ti (60 nm) Ohmic contacts on n-type 4H-SiC after annealing at 1050 °C for 3 min in Ar atmosphere by in-depth electrical and physical characterization. The contact resistivity of the Ni/Ti/W structure (∼ 8.43 × 10−6 Ω·cm2) was found to be lower than that of the Ni/W/Ti structure (∼ 21.9 × 10−6 Ω·cm2). For the Ni/W/Ti structure, the W layer closer to the contact interface led to an increase in the preferred orientation degree of the δ-Ni2Si (220) plane at the interface, favoring a lower contact resistivity according to previous studies. However, the content and interfacial coverage of δ-Ni2Si is reduced by the WxNiyC phase and the interfacial strain/stress is greatly increased by the WxNiyC phase as well, which ultimately leads to an increase in the contact resistivity. The larger interfacial strain/stress in the Ni/W/Ti structure also results in a rough surface morphology with more microcracks and a large area of delamination. In addition, the shearing strength of Al wire bonding points on the Ni/W/Ti surface is slightly weaker than that on the Ni/Ti/W surface due to the higher surface roughness. The above experimental findings can provide a guideline for further structural optimization of the 4H-SiC Ohmic contacts.

Ensuring durability and reliability of contact rings of current collection devices when working in elastic-plastic state

The reliability of ring current-collecting devices during a given service life plays a decisive role in the opera- tion of power supply systems of various equipment and largely depends on the strength and reliability of all its components, in particular, contact rings. One of the most important characteristics of ring current collectors is the contact resistance, which is reduced by using non-ferrous and precious materials with low resistance, while increasing the downforce between the rings of the current collector. With an increase in the compression force F of the contact ring, the resistance of the contacts decreases to a certain minimum value and practically does not decrease with further growth of the force. The dependence of the contact resistance on the compression force has the form of a power function, the coefficients of which are determined experimentally. However, the operability of the contact rings in such severe conditions can be ensured in the case of low speeds and a small number of loading cycles by using the low-cycle fatigue area on the Weller curve. Having determined the coefficients of the equation of the inclined section on the Weller curve in the area of low-cycle fatigue, it is possible to determine the number of permissible loading cycles at a given stress level or solve the inverse problem of determining the permissible stress level if the number of loading cycles is known. To substantiate the correctness of the selected compressive force and the corresponding stresses, methods for calculating the fatigue margin coefficient, as well as a method for calculating the reliability of the ring material, are proposed. Reliability is estimated by the Gauss curve and is numerically expressed in the form of the probability of failure-free operation and the probability of failure, for which the corre- sponding theoretical dependencies are obtained. According to the proposed methods, calculations of the rings of the current-collection device used in EX- PRESS-type spacecraft were performed, which showed the operability of the methods and allowed to ensure the required service life of the contact rings and their reliability. A very simple analytical formulation of the methods allows us to solve both verification and design calculations of rings, depending on the task at hand.

Unlocking High-Performance, Ultra-Low Power van der Waals Photo-Transistors: Toward Back-End-of-Line in-Sensor Machine Vision Applications.

Recent reports on machine learning and machine vision (MV) devices have demonstrated the potential of two-dimensional (2D) materials and devices. Yet, scalable 2D devices are being challenged by contact resistance and Fermi level pinning (FLP), power consumption, and low-cost CMOS compatible lithography processes. To enable CMOS + 2D, it is essential to find a proper lithography strategy that can fulfill these requirements. Here, we explored a modified van der Waals (vdW) deposition lithography and demonstrated a relatively new class of van der Waals field effect transistors (vdW-FETs) based on 2D materials. This lithography strategy enabled us to unlock high-performance devices evident by high current on-off ratio (Ion/Ioff), high turn-on current density (Ion), and weak FLP. We utilized this approach to demonstrate a gate-tunable near-ideal diode using a MoS2/WSe2 heterojunction with an ideality factor of ∼1.65 and current rectification of 102. We finally demonstrated a highly sensitive, scalable, and ultralow power phototransistor using a MoS2/WSe2 vdW-FET for back-end-of-line integration. Our phototransistor exhibited the highest gate-tunable photoresponsivity achieved to date for white light detection with ultralow power dissipation, enabling ultrasensitive optoelectronic applications such as in-sensor MV. Our approach showed the great potential of modified vdW deposition lithography for back-end-of-line CMOS + 2D applications.

Optimizing phosphorus-doped polysilicon in TOPCon structures using silicon oxide layers to improve silicon solar cell performance

Tunnel Oxide Passivated Contact (TOPCon) technology is one of the most influential and industrially viable solar cell technologies available today. Improving the quality of passivation contact has become a central focus of current research. Although the conventional monolayer polycrystalline silicon method is highly effective in TOPCon solar cells, it is limited by doping inhomogeneity, which impairs the passivation and electrical properties, and the cell's photovoltaic conversion efficiency remains suboptimal. To address this issue, this study investigates the deposition of two layers of silicon oxide and two layers of in-situ doped phosphorus amorphous silicon, termed double poly-Si/SiOx structures, on n-type silicon wafers using plasma-enhanced chemical vapor deposition (PECVD). The effectiveness of the structure was confirmed through various characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Key findings indicate that the double-polysilicon structure significantly enhances the uniformity of phosphorus doping, improving the carrier lifetime of the cell and reducing the contact resistance. As a result, the average efficiency in the final production stage has a conversion efficiency gain of 0.23 % over the baseline group. This study underscores the potential of this PECVD methodology to advance the fabrication of high-efficiency solar cells by providing significant improvements in passivation, doping uniformity, and overall cell performance.

Enhancing reaction interface with modified microporous layers for high-efficiency hydrogen production in PEM water electrolysis

Improving the reaction interface is imperative for increasing catalyst utilization and enhancing overall cell performance in proton exchange membrane electrolyzer cells (PEMECs). Herein, a thin Nafion-carbon-mixed microporous layer coated carbon paper (Nafion-C MPL/CP) is first developed as an efficient cathode liquid/gas diffusion layer for PEMECs. With the Nafion-C MPL/CP, low cell voltages of 1.64, 1.74 and 1.84 V are delivered, which are 50, 80 and 140 mV lower than those of the conventional bare carbon paper at 2, 4 and 6 A/cm2, respectively, achieving about 3-fold higher catalyst utilization. Meanwhile, superior performance is also demonstrated compared to the commercial PTFE-C MPL/CP. The remarkable performance of the Nafion-C MPL/CP should be attributed to the enhanced reaction interface, which not only provides rich active sites with abundant electron and proton transport pathways for the electrochemical reaction but also reduces the interfacial contact resistance and mass transport losses. Moreover, excellent stability of the Nafion-C MPL/CP is demonstrated at a current density of 1.8 A/cm2 with no performance degradation during over 100-h operation. Due to the enhanced reaction interface with significantly improved catalyst utilization, the developed Nafion-C MPL/CP shows great potential to reduce the hydrogen production cost and accelerate PEMEC commercialization.

Fabrication of Flexible Transparent Conductive Films via an Energy-Efficient In Situ Chemical Welding and Reinforcement Strategy.

Recently, flexible transparent conductive films composed of metal nanowires have received significant interest, particularly for flexible electronics. However, the high contact resistance among metal nanowires and the weak bonding effect between metal nanowires and substrates often result in films whose conductivity, adhesion, and flexibility fall short of the stringent requirements demanded by real-world uses. We developed a simple method to fabricate high-performance flexible transparent conductive films via successively spin-coating silver nanowires (AgNWs) and acidic silica sol onto the surface of the substrate. Under the capillary force of ethanol and the etching effect of hydrochloric acid, the adjacent AgNWs are induced to chemically weld in situ to form a stable network. The resulting composite film exhibits a sheet resistance of only 8.5 Ω/sq, marking an impressive 80% decrease compared with the pristine AgNW film. Meanwhile, the silica sol acts as a filler, improving light transmittance while further reinforcing the network structure and firmly bonding it to the substrate. Thus, the delamination of the nanowires under bending motion is effectively inhibited, and the resulting film was endowed with resistance remaining below 15 Ω/sq after 3000 bending and 200 tape peeling. The energy-efficient in situ chemical welding and reinforcement method for nanowires provides an innovative strategy for the batch preparation of flexible transparent conductive films.

Large-area and few-layered 1T′-MoTe2 thin films grown by cold-wall chemical vapor deposition

This study employs cold-wall chemical vapor deposition to achieve the growth of MoTe2 thin films on 4-inch sapphire substrates. A two-step growth process is utilized, incorporating MoO3 and Te powder sources under low-pressure conditions to synthesize MoTe2. The resultant MoTe2 thin films exhibit a dominant 1T′ phase, as evidenced by a prominent Raman peak at 161 cm−1. This preferential 1T′ phase formation is attributed to controlled manipulation of the second-step growth temperature, essentially the reaction stage between Te vapor and the pre-deposited MoO x layer. Under these optimized growth conditions, the thickness of the continuous 1T′-MoTe2 films can be precisely tailored within the range of 3.5–5.7 nm (equivalent to 5–8 layers), as determined by atomic force microscopy depth profiling. Hall-effect measurements unveil a typical hole concentration and mobility of 0.2 cm2 Vs−1 and 7.9 × 1021 cm−3, respectively, for the synthesized few-layered 1T′-MoTe2 films. Furthermore, Ti/Al bilayer metal contacts deposited on the few-layered 1T′-MoTe2 films exhibit low specific contact resistances of approximately 1.0 × 10−4 Ω cm2 estimated by the transfer length model. This finding suggests a viable approach for achieving low ohmic contact resistance using the 1T′-MoTe2 intermediate layer between metallic electrodes and two-dimensional semiconductors.

One‐Step‐Sintered GeTe‐Bi2Te3 Segmented Thermoelectric Legs with Robust Interface‐Connection Performance

AbstractSegmented thermoelectric (TE) legs are promising for improving heat‐electricity conversion efficiency, but their practical applications are still limited by the lack of cost‐effective interface‐connection technology. Here, an interface‐connection method for one‐step sintering of GeTe‐Bi2Te3 segmented TE legs is developed using mixtures of Al0.88Si0.12 and Ni (ASN) as diffusion barrier materials. Although the interface‐connection performance using Ni or Al0.88Si0.12 alone is poor, their mixtures can realize a compromise optimization of interface‐connection properties, simultaneously achieving a matched coefficient of thermal expansion, low contact resistivity, high shear strength, and high reliability. These robust interface‐connection properties can be attributed to the activation of the eutectic‐alloy Al0.88Si0.12 and the formation of appropriate reaction‐diffusion layers between ASN and GeTe/Bi2Te3 and between Al0.88Si0.12 and Ni in ASN. Finally, a remarkable energy conversion efficiency of ≈15.5% at a temperature difference of 449 K can be obtained in this segmented TE leg. Moreover, ASN can also be applied in fabricating n‐type PbTe‐Bi2Te3 segmented legs and multi‐pair TE devices, demonstrating the universality of this methodology. This work accelerates the development of robust, low‐cost, one‐step‐sintered segmented TE legs and promotes the use of eutectic alloys as “alloy glues” for advancing TE‐device connection technology.

Quantization Conductance of InSb Quantum-Well Two-Dimensional Electron Gas Using Novel Spilt Gate Structures

Electron transport behaviour in InSb semiconductor significantly changes when the conduction is restricted to two-dimensions. Semiconductor materials are an effective tools to characterize the electron transport in this aspect because the energy separation between transverse modes in a low-dimensional semiconductor device are always inversely proportional to the effective mass, in the same way as for sub-bands in a parabolic potential. Therefore, in this article, a range of novel device geometries were designed, fabricated and characterized to investigate ballistic transport of electrons in low-dimensional InSb structures using surface gated devices to restrict the degrees of freedom (dimensionality) of the active conducting channel. In this framework, designs of gates (i.e., line, loop and solid discussed later) have been used over a range of gate dimensions. Consistent measurement of quantised conductance would be promising for both low power electronics and low temperature transport physics where split gates are typically used for charge sensing. This article presents an experimental results of quantization conductance obtained for the range geometries of novel gates, and some model consideration of the implications of the material choice. Furthermore, the etching techniques (wet and dry) exhibited a significant decrease of ohmic contact resistance from around 35kΩ to only roughly 250Ω at room temperature. Interestingly a possible 0.7 anomaly conduction was observed with a loop gate structure. This work showed perfectly that the two-dimensional electron gases can be formed in narrow gap InSb QWs which makes this configuration device promising candidate for topological quantum computing and next generation integrated circuit applications. Keywords: Quantization conductance, InSb QW, 2DEG, spilt gate structure, ballistic transport.

Quench protection for high-temperature superconductor cables using active control of current distribution

Superconducting magnets of future fusion reactors are expected to rely on composite high-temperature superconductor (HTS) cable conductors. In presently used HTS cables, current sharing between components is limited due to poorly defined contact resistances between superconducting tapes or by design. The interplay between contact and termination resistances is the defining factor for power dissipation in these cables and ultimately defines their safe operational margins. However, the current distribution between components along the composite conductor and inside its terminations is a priori unknown, and presently, no means are available to actively tune current flow distribution in real-time to improve margins of quench protection. Also, the lack of ability to electrically probe individual components makes it impossible to identify conductor damage locations within the cable. In this work, we address both problems by introducing active current control of current distribution between components using cryogenically operated metal-oxide-semiconductor-field-effect transistors (MOSFETs). We demonstrate through simulation and experiments how real-time current controls can help to drastically reduce heat dissipation in a developing hot spot in a two-conductor model system and help identify critical current degradation of individual cable components. Prospects of other potential uses of MOSFET devices for improved voltage detection, AC loss-driven active quench protection, and remnant magnetization reduction in HTS magnets are also discussed.

Study on the effect of room temperature/low temperature environment on the electrical contact plug/pulling wear performance of different copper-based coated conductive connection terminals

This paper explores the wear and tribology performance of three types of terminals, each coated with a different metallic surface (gold, silver, tin), in an environment of fluctuating temperatures. As integral elements of electronic connectors, these terminals are essential for maintaining stable contact resistance, which is crucial to the safety of the entire electrical system. The study reveals that the friction coefficients of the coated terminals are lower at low temperatures compared to ambient temperature. Furthermore, the cooler conditions help maintain more consistent contact resistance. Specifically, the terminals with gold coating mainly experience adhesive and abrasive wear during initial low plug/pull tests, with adhesive wear becoming more dominant in later stages. In contrast, terminals with silver coating primarily suffer from abrasive wear, while those coated with tin tend to show predominantly adhesive wear during initial plug/pull cycles.

Improvement of electrical and optoelectronic properties of ZnO thin films by plasma nitridation treatment

Understanding and controlling the effects of trap sites in ZnO semiconductors are crucial for optimizing device performance and enabling various technological applications. To passivate the trap sites, the N atoms are incorporated into polycrystalline ZnO thin films via a plasma nitridation (PN) process using NH3 gas. The results show that the contact resistivity, sheet resistance, and transfer length of the ZnO photodetector are improved after the PN treatment. The photo-to-dark current ratio (PDCR) and responsivity values increase from 42.52 to 103.19 and from 344.36 A/W to 5727.63 A/W, respectively, after the PN treatment. This improvement in photodetector properties is attributed to the introduced N atoms, which effectively reduce the trap sites in the ZnO thin film. This PN treatment technology has the potential to improve device performance in both electronic and optoelectronic applications.

Effect of temperature on the stability and performance of III-nitride HEMT magnetic field sensors

The study aimed to investigate the underlying physics limiting the temperature stability and performance of non-surface passivated Al0.34Ga0.66N/GaN Hall effect sensors, including contacts, under atmospheric conditions. The results obtained from analyzing the microstructural evolution in the Al0.34Ga0.66N/GaN Hall sensor heterostructure were found to correlate with the electrical performance of the Hall effect sensor. High-resolution x-ray photoelectron spectroscopy studies revealed the signature of surface oxidation in the GaN cap layer, as well as a slight out-diffusion of “Al” from the AlGaN barrier layer. To prevent the formation of a bumpy surface morphology at the Ohmic contact, we investigated the impact of “Pt” top Ohmic contacts. The application of a top “Pt” contact stack resulted in a smooth Ohmic contact surface and provided evidence that the bumpy surface morphology in Au-based Ohmic contacts is due to the formation of an Al-Au viscous alloy during rapid thermal annealing. In the early stages of thermal aging, the small drop in contact resistivity stabilized with subsequent thermal aging past the initial 550 h at 200 °C. The outcome is that the Al0.34Ga0.66N/GaN Hall effect sensors, even without surface passivation, exhibited a stable response to applied magnetic fields with no sign of significant degradation after 2800 h of thermal aging at 200 °C under atmospheric conditions. This observed stability in the Hall sensor without surface passivation can be attributed to a self-imposed surface oxidation of the cap layer during the early stages of aging, which serves as a protective layer for the device during subsequent extended periods of thermal aging at 200 °C.

Study of high-frequency impedance of zinc-rich coatings

In this paper, three types of impedance spectra were investigated, i.e., impedance spectra of two zinc powders (new and old) and five coatings (two different thicknesses of epoxy zinc-rich coatings (EZRCs), an ethyl silicate zinc-rich coating, an epoxy coating and an autodeposition coating) in 3.5 wt.% NaCl solution, dry film impedance spectra of two coatings (the thicker EZRC and autodeposition coating) and their impedance spectra in a 0.003 M LiCl–methanol solution. The results show that the resistive part of the high-frequency impedance of the ZRCs at the early stage of immersion is the contact resistance ( Rm) between the zinc powders, and the capacitive part is the parallel connection of the contact capacitance ( Cm) and the film capacitance ( Cc) of the binder. The coupling of the two capacitors results in a deviation of the measured Pm from the true Pm, where Pm is the Cm-dependent dispersion coefficient