Junction Resistance Research Articles

A novel magnetic tunnel junction fabricated by robust intrinsic van der Waals half-metals

Two-dimensional magnetic van der Waals materials (vdW) have attracted considerable attentions in recent years due to their emerging physical properties and great potential application to the spintronics devices. Magnetic tunnel junction (MTJ) is one of the most important devices in spintronics. However, many unknown mechanisms governing its critical performance remain to be elucidated. Here, based on first-principles calculations, vdW materials VBr3 and VCl3 are shown to be the robust intrinsic half-metals with spin down electron's energy gap about 3.3 eV, and the Fermi level is almost located at the center of the spin down electron's energy gap. Based on this, we predict that application of VBr3 to the magnetic electrodes of MTJ would greatly improve the off/on ratio of junction resistance. Moreover, the coercivity of magnetic electrodes used by vdW material VBr3 can be tuned by the number of layers, and an antiferromagnetic layer pinning the ferromagnetic electrode can be omission. This provides a reliable way to study and design the MTJ devices in the future.

Enhanced Performance of Monolithic Chalcogenide Thermoelectric Modules for Energy Harvesting via Co-optimization of Experiment and Simulation.

With the development of application of wireless sensor nodes (WSNs), the need for energy harvesting is rapidly increasing. In this study, we designed and fabricated a robust monolithic thermoelectric generator (TEG) using a simple, low-energy, and low-cost device fabrication process. Our monolithic device consists of Ag2S0.2Se0.8 and Bi0.5Sb1.5Te3 as n-type and p-type legs, respectively, while the empty space between the legs was filled with highly dense, flexible, and thin Ag2S that serves as both an insulating spacer and a shock absorber, which potentially augments the robustness of preventing from damage from an external mechanical force. From the optimization of the device structure via finite element method (FEM) simulations, a three-pair device with dimensions of 12 mm × 10 mm × 10 mm was found to have a theoretical maximum power density of 8.2 mW cm-2 at a ΔT of 50 K. For considering this inevitable contact resistance, experimental measurement and FEM simulation were combined for quantifying the junction resistance; a power density of 2.1 mW cm-2 was established with the consideration of the contact resistance at the p-n junctions. Using these optimized structural parameters, a device was fabricated and was found to have a maximum power density of 2.02 mW cm-2 at a ΔT of 50 K, which is in good agreement with our simulations. The results from our monolithic TEG show that despite the simple, low-energy, and low-cost device fabrication process, the power generation is still comparable to other reported TEGs. It is worth mentioning that our design could be extended to other chalcogenide materials of appropriate temperature regions and/or better zT. Besides, the quantification of contact resistance also exhibited reference value for the enhancement of thermoelectric conversion application. These results provide a convenient, economic, and efficient strategy for waste energy harvesting close to room temperature, which can broaden the applications of waste heat harvesting.

Nuclease resistance and protein recognition properties of DNA and hybrid PNA-DNA four-way junctions

Nucleic acids possess unique biochemical features that make them ideal candidates to inhibit “difficult to target” proteins. The limited stability of nucleic acids in vivo presents a major obstacle to their development as drugs. Here, immobile four-way junctions (4WJs) are used to target the DNA-binding cytokine, High Mobility Group B1. Hybrid 4WJs composed of DNA and peptide nucleic acids (PNA) are investigated. PNA possess enhanced nuclease stability vs. DNA. 4WJs are incubated with Exonuclease III and DNase I. The nuclease assays show that 4WJs containing multiple PNAs possess significantly higher stability. Circular dichroism assays are used to probe the groove topology of 4WJs with the minor groove binder, DAPI. The CD data indicates that multi-PNA 4WJs possess altered minor groove dimensions that reduces DAPI binding affinity. Logic suggests that the minor groove of multi-PNA hybrids possess significant perturbations to the topology and local electrostatic environment that prevents proper binding/recognition by nucleases and thus enhances stability.

Lactobacillus reuteri 1 Enhances Intestinal Epithelial Barrier Function and Alleviates the Inflammatory Response Induced by Enterotoxigenic Escherichia coli K88 via Suppressing the MLCK Signaling Pathway in IPEC-J2 Cells.

Intestinal epithelial barrier injury disrupts immune homeostasis and leads to many intestinal disorders. Lactobacillus reuteri (L. reuteri) strains can influence immune system development and intestinal function. However, the underlying mechanisms of L. reuteri LR1 that regulate inflammatory response and intestinal integrity are still unknown. The present study aimed to determine the effects of LR1 on the ETEC K88-induced intestinal epithelial injury on the inflammatory response, intestinal epithelial barrier function, and the MLCK signal pathway and its underlying mechanism. Here, we showed that the 1 × 109 cfu/ml LR1 treatment for 4 h dramatically decreased interleukin-8 (IL-8) and IL-6 expression. Then, the data indicated that the 1 × 108 cfu/ml ETEC K88 treatment for 4 h dramatically enhanced IL-8, IL-6, and tumor necrosis factor-α (TNF-α) expression. Furthermore, scanning electron microscope (SEM) data indicated that pretreatment with LR1 inhibited the ETEC K88 that adhered on IPEC-J2 and alleviated the scratch injury of IPEC J2 cells. Moreover, LR1 pretreatment significantly reversed the declined transepithelial electrical resistance (TER) and tight junction protein level, and enhanced the induction by ETEC K88 treatment. Additionally, LR1 pretreatment dramatically declined IL-8, IL-17A, IL-6, and TNF-α levels compared with the ETEC K88 group. Then, ETEC K88-treated IPEC-J2 cells had a higher level of myosin light-chain kinase (MLCK), higher MLC levels, and a lower Rho-associated kinase (ROCK) level than the control group, while LR1 pretreatment significantly declined the MLCK and MLC expression and enhanced ROCK level in the ETEC K88-challenged IPEC-J2 cells. Mechanistically, depletion of MLCK significantly declined MLC expression in IPEC-J2 challenged with ETEC K88 compared to the si NC+ETEC K88 group. On the other hand, the TER of the si MLCK+ETEC K88 group was higher and the FD4 flux in the si MLCK+ETEC K88 group was lower compared with the si NC+ETEC K88 group. In addition, depletion of MLCK significantly enhanced Claudin-1 level and declined IL-8 and TNF-α levels in IPEC-J2 pretreated with LR1 followed by challenging with ETEC K88. In conclusion, our work indicated that L. reuteri LR1 can decline inflammatory response and improve intestinal epithelial barrier function through suppressing the MLCK signal pathway in the ETEC K88-challenged IPEC-J2.

Influence of device non-uniformities on the accuracy of Coulomb blockade thermometry

We investigate temperature uncertainty of Coulomb blockade thermometer (CBT) arising from inevitable non-uniformities in tunnel junction arrays. The corrections are proportional to the junction resistance variance in the linear operation regime and this result holds approximately also beyond this originally studied high temperature range. We present both analytical and numerical results, and discuss briefly their implications on achievable uniformity based on state-of-the-art fabrication of sensors.

Data acquisition system for a neutron spectrometer with a remote diamond detector

The article presents the design and first test results of the neutron spectrometer with count rate up to 7 × 106 events per second with remote detector based on artificial diamond, intended for use on burning plasma experiments. The spectrometer consists of the broadband low-noise amplifier and the data acquisition and processing unit. The design of the amplifier with characteristic impedance matching of the cable line by the dynamic resistance of the transistor base-emitter junction is considered. The data acquisition and processing unit is realized using a real-time event-processing algorithm based on harmonic data analysis. This algorithm includes effective techniques for detecting and excluding overlaps and suppression of fluctuations in the baseline level corresponding to zero signal.

Highly‐Packed Proximity‐Coupled DC‐Josephson Junction Arrays by a Direct‐Write Approach

AbstractFocused ion beam induced deposition (FIBID) is a direct‐write technique enabling the growth of individual nanostructures of any shape and dimension with high lateral resolution. Moreover, the fast and reliable writing of periodically arranged nanostructures can be used to fabricate devices for the investigation of collective phenomena and to design novel functional metamaterials. Here, FIBID is employed to prepare dc‐Josephson junction arrays (dc‐JJA) consisting of superconducting NbC dots coupled through the proximity effect via a granular metal layer. The fabrication is straightforward and allows the preparation of dc‐JJA within a few seconds. Microstructure and composition of the arrays are investigated by transmission electron microscopy and energy dispersive X‐ray spectroscopy. The superconductor‐to‐metal transition of the prepared dc‐JJA is studied in a direct way, by tuning the Josephson junction resistance in 70 nm‐spaced superconducting NbC dots. The observed magnetoresistance oscillations with a period determined by the flux quantum give evidence for the coherent charge transport by paired electrons. Moreover, the measured resistance minima correspond to two fundamental matching configurations of fluxons in the dc‐JJA, caused by magnetic frustration. The robust properties of the prepared dc‐JJA demonstrate the opportunities for a fast preparation of complex device configurations using direct‐write approaches.

Continuous and fast magneto-ionic control of magnetism in Ta/Co/BiFeO3/SrRuO3 multiferroic heterostructure

Room temperature electric field controlled magnetism is extremely promising for the next-generation high-performance spintronic devices. Here, based on the ferroelectric switching driven oxygen ion migration in the Ta/Co/BiFeO3/SrRuO3 heterostructures, the magnetic moment, magnetic coercive field, exchange bias field, and junction resistance are reversibly manipulated by tuning the ferroelectric polarization of the BiFeO3 layer. All these phenomena are consistently explained by the oxygen ion migration induced CoOx/Co redox effect, which is evidenced by the synchrotron X-ray absorption spectroscopy measurements. Interestingly, owing to the controllable ferroelectric switching dynamics of the BiFeO3 thin film, the magnetic coercive field of the Co thin film can be continuously and precisely tuned by controlling the ferroelectric polarization of the BiFeO3 thin film, and the manipulating speed of the voltage control of magnetism can be fast to 100 ns. This nonvolatile, stable, reversible, fast, and reproducible voltage control of magnetism shows great potential for designing low-power and high-speed spintronics.

Electrochemical Redox In-Situ Welding of Silver Nanowire Films with High Transparency and Conductivity

Silver nanowire (AgNW) networks with high transparency and conductivity are crucial to developing transparent conductive films (TCFs) for flexible optoelectronic devices. However, AgNW-based TCFs still suffer from the high contact resistance of AgNW junctions with both the in-plane and out-of-plane charge transport barrier. Herein, we report a rapid and green electrochemical redox strategy to in-situ weld AgNW networks for the enhanced conductivity and mechanical durability of TCFs with constant transparency. The welded TCFs show a marked decrease of the sheet resistance (reduced to 45.5% of initial values on average) with high transmittance of 97.02% at 550 nm (deducting the background of substrates). The electrochemical welding treatment enables the removal of the residual polyvinylpyrrolidone layer and the in-situ formation of Ag solder in the oxidation and reduction processes, respectively. Furthermore, local conductivity studies confirm the improvement of both the in-plane and the out-of-plane charge transport by conductive atomic force microscopy. This proposed electrochemical redox method provides new insights on the welding of AgNW-based TCFs with high transparency and low resistance for the development of next-generation flexible optoelectronic devices. Furthermore, such conductive films based on the interconnected AgNW networks can be acted as an ideal supporter to construct heterogeneous structures with other functional materials for wide applications in photocatalysis and electrocatalysis.

P‐97: Activegrid Advanced Materials Enabling Next‐Generation Designs

C3Nano has developed the highest performing (solution coated) flexible conductor (Activegrid™); Activegrid™, a patented technology, employs “Nanoglue™” a proprietary chemical sintering agent that fuses nanowires (NWs) into a nanoscale metallic grid upon coating and drying. The fusing is achieved by the selective nucleation of the conductive Nanoglue™ at the junctions between NWs. Due to their concavity and nanoscale roughness, junctions promote the deposition the Nanoglue™. Nucleation at the junctions are both kinetically and thermodynamically favorable. The junctions lower the overall barrier to nucleation (kinetics) and deposition leads to a reduced overall free energy (thermodynamics). The ability to deliver the minimal amount of metal (due to fusing at the high resistance junctions) and still achieve low resistances engenders ultra‐low haze transparent conductors which are being integrated into a variety of touch sensors and displays. The nanoscale nature of the Activegrid™ material allows for outstanding flexibility and robustness. Novel other technologies being developed at C3Nano including manipulating the color of transparent conductors will also be described.

Variation of Junction Resistance Near Phase Transition of NdBa2Cu3O7-δ Superconductor in Ambegaokar–Baratoff and de Gennes Theories

Variation of Junction Resistance Near Phase Transition of NdBa2Cu3O7-δ Superconductor in Ambegaokar–Baratoff and de Gennes Theories

Non-typeable Haemophilus influenzae biofilm formation on primary human airway epithelia cultured at air-liquid interface

Introduction Primary ciliary dyskinesia (PCD) is an inherited heterogeneous disorder associated with defective motile cilia on airway epithelia, resulting in impaired mucociliary function and ultimately, bronchiectasis. Non-typeable Haemophilus influenzae (NTHi) is frequently isolated from PCD airways where it resides in biofilms. It is unclear if biological pathways in response to NTHi infection differ in PCD, contributing to increased susceptibility to biofilm-associated infection. Aim The development of a biologically representative co-culture model to investigate the interactions between PCD airway epithelia and NTHi biofilms. Methods Air-liquid interface (ALI)-cultured non-PCD primary nasal cells were grown in transwells. Barrier properties were assessed by trans-epithelial electrical resistance (TEER), FITC-dextran passage and tight junction staining. Ciliary function was assessed by high-speed video microscopy at 37°C. ALI cultures were infected with a PCD NTHi isolate at multiplicity of infections (MOIs) 10, 50 or 100 and co-cultured to form biofilms over 3 days. TEER was measured pre- and post-infection, NTHi recoverability assessed by conventional culture, and biofilm formation confirmed by scanning electron microscopy (SEM). Results Epithelial culture at ALI was successful, with tight barriers being formed and normal ciliary beat pattern and frequency recorded (mean 14Hz). Following co-culture, TEER increased relative to pre-infection at all MOIs but maximum NTHi recoverability was at MOI 50 (median colony forming units, 6.8x106per cm2). SEM confirmed NTHi biofilm formation at MOI 50. Conclusions A successful NTHi biofilm co-culture model on human primary epithelia was established. This will be used with PCD epithelia to investigate host-pathogen interactions during NTHi biofilm colonisation.

Facile Surface Modification of Ultrathin Gold Nanowires Film with Hydrogen Sulfide for Improvement of Stability

Ultrathin gold nanowires (AuNWs) have an important role and promising applications in areas of wearable sensors, matter detection, and flexible transparent electronic materials. But oleylamine (OAm) ligand on the ultrathin AuNWs surface leads to high junction resistance and the inherent Rayleigh instability leads to decomposition into gold spheres within a few days. To eliminate these two disadvantages, herein, the implementation of one facile H2S gas treatment method to improve the conductivity and stability of ultrathin AuNWs is tried. The conductivity of AuNWs on the interdigital electrode can be improved by 4 × 107 times because the AuNWs became bent and cross‐linked, due to the H2S exchange of the ligand OAm. In addition, the conductivity of the three‐layer ultrathin AuNW film on polyethylene terephthalate (PET) can be improved by at least 2000 times. The ultrafine structure of AuNWs can be maintained for more than 1 week at room temperature, which attributes to H2S that can protect the surface structure of AuNWs. The findings highlight a new method of the ultrathin AuNWs for exceeding improvement in electronic conduction and stability.

Tunneling Magnetoresistance in Noncollinear Antiferromagnetic Tunnel Junctions.

Antiferromagnetic (AFM) spintronics has emerged as a subfield of spintronics driven by the advantages of antiferromagnets producing no stray fields and exhibiting ultrafast magnetization dynamics. The efficient method to detect an AFM order parameter, known as the Néel vector, by electric means is critical to realize concepts of AFM spintronics. Here, we demonstrate that noncollinear AFM metals, such as Mn_{3}Sn, exhibit a momentum dependent spin polarization which can be exploited in AFM tunnel junctions to detect the Néel vector. Using first-principles calculations, we predict a tunneling magnetoresistance (TMR) effect as high as 300% in AFM tunnel junctions with Mn_{3}Sn electrodes, where the junction resistance depends on the relative orientation of their Néel vectors and exhibits four nonvolatile resistance states. We argue that the spin-split band structure and the related TMR effect can also be realized in other noncollinear AFM metals like Mn_{3}Ge, Mn_{3}Ga, Mn_{3}Pt, and Mn_{3}GaN. Our work provides a robust method for detecting the Néel vector in noncollinear antiferromagnets via the TMR effect, which may be useful for their application in AFM spintronic devices.

Novel Transparent TiO2/AgNW-Si(NH2)/PET Hybrid Films for Flexible Smart Windows.

The application of flexible indium tin oxide (ITO)-free electrochromic devices (FCDs) has always been a research hotspot in flexible electronics. Recently, a silver nanowire (AgNW)-based transparent conductive film has raised great interest as an ITO-free substrate for FCDs. However, several challenges, such as the weak binding of AgNWs to the substrate, high junction resistance, and oxidation of AgNWs, remain. In this paper, a novel method for surface modification of AgNWs with N-aminoethyl-γ-aminopropyltrimethoxysilane [Si(NH2)] solution is proposed to enhance the bonding with the flexible substrates and the active materials, thereby inhibiting the delamination of AgNWs from the substrate and reducing the high junction resistance between nanowires. The TiO2/AgNW-Si(NH2)/poly(ethylene terephthalate) (PET) films show outstanding mechanical properties, of which the resistance remains almost unchanged after mechanical bending of 5000 cycles (ΔR/R0 ≈ 3.6%) and repeated peeling off cycles with 3M tape 100 times (ΔR/R0 ≈ 6.0%). In addition, we found that the oxygen-containing groups on the TiO2/AgNW-Si(NH2)/PET surface form hydrogen bonds with the TiO2 sol, resulting in tight contact between the TiO2 sol and the AgNWs, which prevents the AgNWs from oxidation. As a result, the TiO2/AgNW-Si(NH2)/PET film exhibited long-time aging (ΔR/R0 ≈ 4.9% in the air for 100 days) stability. A FCD was constructed with the TiO2/AgNW-Si(NH2)/PET film, which showed excellent electrochromic performance (94% retention) after 5000 bending cycles, indicating high stability and mechanical flexibility. These results present a promising solution to the transparent conductive films for flexible energy devices.

Astrocytic responses to high glucose impair barrier formation in cerebral microvessel endothelial cells.

Hyperglycemic conditions are prodromal to blood-brain barrier (BBB) impairment. The BBB comprises cerebral microvessel endothelial cells (CMECs) that are surrounded by astrocytic foot processes. Astrocytes express high levels of gap junction connexin 43 (Cx43), which play an important role in autocrine and paracrine signaling interactions that mediate gliovascular cross talk through secreted products. One of the key factors of the astrocytic "secretome" is vascular endothelial growth factor (VEGF), a potent angiogenic factor that can disrupt BBB integrity. We hypothesize that high-glucose conditions change the astrocytic expression of Cx43 and increase VEGF secretion leading to impairment of CMEC barrier properties in vitro and in vivo. Using coculture of neonatal rat astrocytes and CMEC, we mimic hyperglycemic conditions using high-glucose (HG) feeding media and show a significant decrease in Cx43 expression and the corresponding increase in secreted VEGF. This result was confirmed by the analyses of Cx43 and VEGF protein levels in the brain cortex samples from the type 2 diabetic rat (T2DN). To further characterize inducible changes in BBB, we measured transendothelial cell electrical resistance (TEER) and tight junction protein levels in cocultured conditioned astrocytes with isolated rat CMEC. The coculture monolayer's integrity and permeability were significantly compromised by HG media exposure, which was indicated by decreased TEER without a change in tight junction protein levels in CMEC. Our study provides insight into gliovascular adaptations to increased glucose levels resulting in impaired cellular cross talk between astrocytes and CMEC, which could be one explanation for cerebral BBB disruption in diabetic conditions.

Noise behaviors of SWIR InxGa1-xAs/InP focal plane arrays as a function of lattice-mismatch degree

A quantitatively investigation on the dark noise behaviors of In0.53Ga0.47As/InP, In0.75Ga0.25As/In0.75Al0.25As/InP and In0.83Ga0.17As/In0.83Al0.17As/InP short-wavelength infrared (SWIR) focal plane arrays (FPAs) with cutoff wavelengths (λc) of 1.7, 2.2 and 2.5 μm, respectively, is presented. Theoretical FPA noise model consisting of the diode thermal noise, the dark current shot noise, the operational transimpedance amplifier (OTA) thermal noise, the 1/f noise, the sample and hold noise of the circuit, and etc. were fully taken into consideration. The results show that the dark noises are mainly composed of the OTA thermal noise of the readout circuit under short integration times (Tint) for all three FPAs. Under long Tint, the thermal noises from the photodiode arrays at 300 K is acting as the primary source for the dark noise of the lattice-matched In0.53Ga0.17As FPA, whereas noises of the lattice-mismatched 2.2 and 2.5 μm FPAs are identified to be mainly comes from the diode thermal noise, the dark current shot noise, and the 1/f noise at 150 and 180 K. In addition, an overall trend that the contribution of the 1/f noise increases significantly even if the junction impedance increases and the dark current decreases by cooling down for the extended wavelength detector, which is related to the existence of high density misfit dislocation defect-related trap states in the materials. These results suggest that lowering the junction capacitance and increasing the junction resistance are effective routes to suppress the total readout noise of the InGaAs FPAs, which essentially relies on the improvements on the material epitaxial growth and photodiode array processing recipes.Index Terms: readout noise, lattice-mismatch, focal plane array, InGaAs, noise model.

Dead Time Optimization in a GaN-Based Buck Converter

A gallium nitride (GaN) field effect transistor can provide superior performance over a Si- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> due to its low <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -state resistance and low junction capacitances. However, a GaN-based converter exhibits higher dead time loss during reverse conduction. Thus, to improve the efficiency, dead time optimization is required. This article proposes simple models for dead time optimization in a GaN-based buck converter under different load conditions. The proposed models are analytical in nature compared to the conventional models available for Si-based converters. A buck converter prototype is designed using a 100 V GaN device (GS61008P from GaN Systems) and the proposed analytical model-based dead time optimization techniques are validated experimentally. The proposed modeling techniques can be extended for other GaN-based dc–dc converters.

Progress and Challenges for Memtransistors in Neuromorphic Circuits and Systems.

Due to the increasing importance of artificial intelligence (AI), significant recent effort has been devoted to the development of neuromorphic circuits that seek to emulate the energy-efficient information processing of the brain. While non-volatile memory (NVM) based on resistive switches, phase-change memory, and magnetic tunnel junctions has shown potential for implementing neural networks, additional multi-terminal device concepts are required for more sophisticated bio-realistic functions. Of particular interest are memtransistors based on low-dimensional nanomaterials, which are capable of electrostatically tuning memory and learning behavior at the device level. Herein, a conceptual overview of the memtransistor is provided in the context of neuromorphic circuits. Recent progress is surveyed for memtransistors and related multi-terminal NVM devices including dual-gated floating-gate memories, dual-gated ferroelectric transistors, and dual-gated van der Waals heterojunctions. The different materials systems and device architectures are classified based on the degree of control and relative tunability of synaptic behavior, with an emphasis on device concepts that harness the reduced dimensionality, weak electrostatic screening, and phase-changes properties of nanomaterials. Finally, strategies for achieving wafer-scale integration of memtransistors and multi-terminal NVM devices are delineated, with specific attention given to the materials challenges for practical neuromorphic circuits.

Closely Following Equivalent Circuit Changes during Operation of Graphene Dot Light‐Emitting Electrochemical Cells

AbstractLight‐emitting electrochemical cells (LECs) have presented themselves as an alternative to light emitting diodes (LEDs) because of the simple device design which is accompanied by a lower driving power. LECs operate by rearranging ion and electron transfers that create a p‐n junction at a sufficient voltage, permitting LEC emissions. However, this rearrangement is not well understood. Therefore, the ion and electron transfer processes of the device during ion rearrangement, operation and at excessive overpotentials must be characterized for LEC devices. This paper reports on investigation of these LEC processes using electrochemical impedance spectroscopy (EIS). All processes were successfully characterized with simple equivalent circuits. To the best of our knowledge, an inductive low frequency loop was observed in an LEC for the first time. We propose that this inductivity was due to the p‐n junction resistance to low frequency potential changes. Consistent observations and inverse proportionality between overpotential and inductance provided additional evidence for our proposal. This p‐n junction at low frequency opposition combined with LEC operational stability data can provide a basis for judging the chemical resistance to deterioration and charge storage capacity of p‐n junctions in the future. Furthermore, the techniques and equivalent circuits presented here will help to identify failure mechanisms and increase LEC operational lifetimes.