Leakage Current Measurements Research Articles

Low temperature and magnetic field dependent ferroelectric behaviour of four-layered Aurivillius Bi5FeTi3O15 film prepared by spin coating

Thin films of four–layered Aurivillius Bi5FeTi3O15 compound were prepared using spin coating method. Phase purity of the sample is confirmed via X–ray diffraction and Raman spectroscopy measurements. Ferroelectricity in the prepared film is established from polarization versus electric field (P–E) loop measurements. The remnant and saturation polarization obtained from low temperature P–E measurements reveal a peculiar temperature dependence viz., decreasing on lowering the temperature. Apart from this, a development of an internal field in the system is observed towards lower temperatures which is reflected as biasing in the loops. Further, temperature dependent leakage current measurements have been performed and the analysis into conduction mechanisms shed light into the possible defect related mechanisms responsible for the aforementioned peculiar low temperature ferroelectric behavior. Also, the possibility of multiferroicity in the prepared film is explored with external magnetic field dependent P–E measurements and the results show very weak coupling between polarization and magnetic field.

Utilization of nanoporous biosilica of diatoms as a potential source material for fabrication of nanoelectronic device and their characterization

Biosilica obtained from frustules of diatoms have very delicate nanostructures similar to many micro- and nanofluidic devices. In the present investigation, a cheaper and ecofriendly metal-oxide-semiconductor (MOS) tool has been fabricated exploiting frustules of the diatom Halamphora subturgida. The structural, optical, and chemical characterizations of the cleaned frustules of cultured diatom were investigated through various techniques. Electron microscopic images revealed intricate morphology of the nanostructured silica with very minute pores making the frustules very hard but light material. UV-Vis spectroscopy showed maximum absorbance at 223 nm. The absorption maximum for photoluminescence was centered at 462 nm and that of cathodoluminescence was at 439.9 nm and 466.6 nm. Bulk of extracted silicon dioxide (SiO2) nano-powder from diatom frustules was used as a source material for preparing a high-quality crystalline film on P-type silicon (p-Si) by vapor-liquid-solid (VLS) method. The crystalline quality of the film was tested by X-ray diffraction (XRD) and the crystalline size obtained was 62 ± 2.4 nm. From scanning electron microscopic (SEM) investigation, the growth of a continuous film from diatom biosilica on p-Si substrate was revealed. The thickness of the as-grown SiO2 film was 22.2 ± 1.6 nm, obtained from spectroscopic ellipsometry (SE) study. The performances of fabricated Al/SiO2/Si metal-oxide-semiconductor capacitor were tested by measuring leakage current (~ 43 ± 8 × 10−11 A μm−2 at +2 V), capacitance-voltage, constant current (0.1 μA), and voltage stress (at − 2 V) for reliable gate dielectrics applications in MOS devices. Overall, the process was cost-effective and provides an alternative technique to design high-quality diatom-derived “Bio-SiO2 films” on p-Si substrate.

Electrical Characterization of Sputter Deposited AlxSc1-XN Thin Films

Ferroelectric materials have been utilized for non-volatile memory applications [1]. Beside extensive works on ferroelectric HfO2 thin film [2, 3], recent works on nitride-based materials have proven that AlxSc1-xN (ASN) also shows ferroelectricity with a box-like characteristic [4]. Commonly Pt electrodes with a large Schottky barrier are utilized to overcome the small bandgap of ASN. However, a high remnant polarization of over 100 µC/cm2 is attractive for future non-volatile memory applications. The purpose of this study is to measure the basic electrical properties of ASN films deposited by sputtering with W electrodes.50-, 75-, and 100-nm-thick ASN films were deposited by DC reactive sputtering with an Al0.57Sc0.43 target in Ar and N2 ambient at a substrate temperature of 400oC. Both top and bottom electrodes were deposited at room temperature.Leakage current characteristics of the fabricated metal-insulator-metal (MIM) capacitors indicate a breakdown field of 3 MV/cm. Temperature-dependent leakage current measurement has indicated a Schottky barrier height of 1.0 eV at W/ASN interface, which is rather small for memory application and needs to be engineered. Hysteresis in the polarization-voltage measurements can be hardly observed due to excess leakage current. However, ferroelectric hysteresis curves were obtained from capacitance-voltage (CV) measurements at 100 kHz for all the samples with different thicknesses. The coercive field taken from the hump in the CV curves was 0.9 MV/cm for 50-nm-thick sample and 1.4 MV/cm for 75 and 100 nm-thick samples, which are lower than the reported thick ASN samples [4], implying thickness-dependent properties of ASN films.In conclusion, JV and CV characteristics of sputter-deposited ASN films on W electrode were performed. Relatively low energy offset at metal/ASN interface was extracted. Ferroelectric hysteresis was obtained from CV measurement even for a film as thin as 50 nm.

Electrical Characterization of Sputter Deposited AlxSc1-XN Thin Films

Nitride-based materials including AlxSc1-xN (ASN) films have also been proven to show a ferroelectricity with a box-like characteristic recently. In this paper, ASN thin films were deposited by RF sputtering with different metal electrode materials, Al, W, TiN and Ni. Leakage current measurements hardly showed difference among the electrode materials. A Schottky barrier height (SBH) at metal/ASN interface was as small as 0.86 eV, irrespective to the electrode material, suggesting a strong Fermi level pinning (FLP). Capacitance-voltage (CV) measurements revealed ferroelectric-like hysteresis behavior for all the electrode materials.

Investigation of charge multiplication in irradiated p-type silicon strip sensors designed for the ATLAS phase II tracking detector

Future particle accelerator experiments, for example the High Luminosity-LHC (HL-LHC) in 2025, will demand a much higher radiation hardness of silicon strip sensors due to high fluences and long operation times. New p-type strip sensors have been developed and their charge collection behavior as well as their electrical performance have been investigated. Additionally the long-term behavior under operation has to be investigated and understood. In previous studies of the annealing behavior, the phenomenon of charge multiplication appeared in highly irradiated and/or long-term annealed sensors. This phenomenon is now thoroughly investigated within this study for ATLAS12 strip sensors irradiated to fluences ranging from 5⋅1014neq∕cm2 to 2⋅1015neq∕cm2. Therefore systematic charge collection, leakage current and electric field measurements have been carried out at several annealing temperatures between 23°C and 80°C to investigate the dependence on temperature and fluence. The stability, temperature effects and the maximum amount of multiplication reachable were investigated. Severe changes in the signal pulses in time were observed with increasing amount of annealing. The pulse duration started to increase for enhanced charge multiplication, exceeding the readout shaping time of the ALIBAVA system.

Monitoring Deep Dielectric Charging Effects in Space

A deep dielectric charging effects monitor was proposed for providing in situ measurements of deep dielectric charging effects on satellites via measurements of the surface leakage currents and the internal charging potential of the dielectric. The detailed design and the first flight results onboard a medium Earth orbit (MEO) navigation satellite were discussed. Large temporal variations of the leakage currents were observed in the outer zone. The first flight data showed that the maximum charging electric field of the FR4 dielectric was less than 1.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> V/m, the incident internal flux was less than 100 pA/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and no charging risk was determined in this period. The calculated conductivity of the FR4 dielectric was about 1.4-3.7 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-15</sup> S/m. These results showed that conductivity obtained by the traditional method overestimated the true value, whereas that obtained by the charge decay method underestimated the true value.

Concepção de um sistema de automação e monitoramento para equipamento utilizado em ensaios de trilhamento elétrico e erosão

&lt;p&gt;This paper aimed at the design and development of a data acquisition and control system using the Arduino open-source platform to automate equipment responsible for the IEC 60587 electrical tracking and erosion test. The developed system allows the selection of protection resistors specified by the standard from the voltage value informed by the operator, monitoring of the leakage current flowing over five samples simultaneously tested and automatically interrupts the samples if the leakage current exceeds 60 mA for more than two seconds. The leakage current values are measured indirectly from the voltage drop across 50 Ω shunt resistors installed in series with each sample. The voltage values on the shunt resistors are conditioned by a measuring circuit that allows the voltage level to be adjusted to the analog inputs of the microcontroller, ie, between 0 V and 5 V. The microcontroller treatment performs the voltage signal obtained by the measuring circuit, the calculation of the RMS value of the current and stop criterion monitoring the leakage current. The calibration of the leakage current measurement circuit was performed by comparing voltage values measured by a digital oscilloscope for four different alternate waveforms and values up to 5 Vrms, corresponding to currents up to 100 mA. The results showed that the circuit provided measurements close to the values measured by the oscilloscope, with errors below 11%. For current values between 30 mA and 80 mA, the errors were less than 6%.&lt;/p&gt;

A Novel Leakage-Current-Based Online Insulation Monitoring Strategy for Converter Transformers Using Common-Mode and Differential-Mode Harmonics in VSC System

Online insulation monitoring techniques for power transformers have been widely studied. However, challenges rise when they are applied to the converter-connected transformers which are operated under high electrical stress conditions. This article proposes a nonintrusive leakage-current-based insulation monitoring strategy for converter transformers, using inherent characteristic harmonics in voltage source converter system. Analytic relation between common-mode and differential-mode harmonics and insulation capacitances is first presented. Then, a combined strategy is proposed based on the differential measurement of leakage current, which enables online prognosis of not only overall ageing degree but also ageing localization of the phase-to-ground insulation. Experiments are conducted on a 15-kVA transformer driven by an industrial inverter. The proposed combined strategy shows robust performance over effective characteristic frequency spectrums. Several considerations for field implementation are further discussed. The major features of the proposed strategy are as follows: 1) easy implementation and nonintrusive measurement; 2) little impact on system operation and immunity to system interferences; and 3) lower requirements of data processing.

Investigation of interfacial dead layers parameters in Au/Ba0.85Sr0.15TiO3/Pt capacitor devices

New ferroelectric Ba0.85Sr0.15TiO3 (BST) thin films are deposited with different thicknesses (50,100, 200,280 and 400 nm) on silicon platinized substrates using spin coater machine and their morphological and structural properties are investigated. The results show that the films are well crystallized and that the perovskite phase is identified. The influence of BST film thickness on the dielectric characteristics of Au/Ba0.85Sr0.15TiO3/Pt capacitors are investigated and shows that the dielectric permittivity of the capacitors decreases with decreasing BST film thickness indicating the existence of a dead layer in the interfaces. Based on a series capacitor model, the dielectric permittivity and leakage current measurements, the thicknesses and dielectric permittivity of the dead layers on the Au/BST and BST/Pt interfaces are well investigated.

Long-term aging characteristics of co-filled nano-silica and micro-ATH in HTV silicone rubber composite insulators

Multiple environmental stresses produce complex phenomena of aging in polymeric insulators. The main aim of this research is to investigate the improved aging characteristics of silica (SiO2)/alumina trihydrate (ATH) hybrid samples (HSs) in high-temperature vulcanized rubber. For this purpose, three HSs comprising 20% micro-ATH with 2% nano-SiO2 (S2), 4% nano-SiO2 (S4), 6% nano-SiO2 (S6) along with sample-virgin (SV) are subjected to long-term accelerated aging of 9000 h. A special aging chamber is fabricated for the aging process of samples. The aging characteristics of these samples are investigated by measuring leakage current (LC) and hydrophobicity classification (HC) after every weathering cycle. Similarly, Fourier transform infrared (FTIR) spectroscopy is performed to observe the important structural changes over the entire aging time. The dielectric strength of AC is also performed after every 1000 h of aging. Tracking and erosion resistance and mechanical properties are also investigated before and after aging. From the critical investigation, it is observed that HSs possess improved results in all the conducted tests. S2 has the lowest LC and HC values throughout the aging time. Similarly, S6 described the highest breakdown strength at the end of the accelerated aging. In the case of FTIR, it is analyzed that the important wave numbers remain intact for all the HSs in the accelerated aging environment. The loss percentage in the wave number for SV is higher, compared to the HSs. After performing the tracking and erosion resistance test, HSs have superior performance. For some of the mechanical properties, HSs showed improved values. Thus, from the experimental analysis, it is deducted that the sample S2 offers the highest resistance to the aging conditions, compared to the SV and other HSs.

Study of barium titanate/nickel-zinc ferrite based composites: Electrical and magnetic properties and humidity sensitivity

Composites based on barium titanate and nickel zinc ferrite doped with cooper and samarium were prepared by a mixing method. The formation of barium titanate tetragonal crystal structure and nickel zinc ferrite cubic spinel structure was identified. Polygonal grains were formed in all three types of ceramics. Due to the very high conductivity of ferrite phase in the materials the ferroelectric hysteresis loops were roundish and not typical for classical ferroelectric material. The break down field was found to be similar for all compositions. Leakage current measurements have shown the existence of different types of conductivity mechanisms in each material. The impedance analysis suggested a bit stronger impact of grain boundaries on total conductivity of the composites and the mechanism of polaronic conduction of two types. The magnetization of the composites is lower than for the pure ferrite phase and corresponds to the weight fraction of the ferrite phase. The soft magnetic nature of these composites might be very useful for development of multifunctional devices which will be able to switch the magnetization with small external magnetic field. Humidity sensing properties of the prepared ceramics were also investigated.

Analytical Analysis and Design of an Advanced Differential-Mode Current Sensor for Insulation Monitoring for Industrial Electrical Assets

Some industrial incidents are attributed to insulation degradation of electrical assets. The leakage current can be a crucial indicator for online insulation monitoring of asset. To realize per-phase monitoring, the measurement accuracy of milliampere-level leakage current is limited by the strong load current noises. This article proposes an advanced current sensor with a dual-core topology based on differential-mode (DM) measurement. An analytical model of magnetic field of the dual-core sensor is originally presented. It helps clarify the significances of the inner core in filtering noises and reducing the influence of system operation and cable positioning. Then, a comprehensive design procedure is fully investigated by selecting the optimal position and approach for magnetic field detection, and a high-speed and low-noise signal conditioning circuit is presented. The proposed current sensor is tested in the laboratory. Experimental results indicate that measurement errors can remain within 0.1mA in the testing scope, where the load current is up to 100A and the DM current varies from 0-7mA. The proposed sensor is further validated with superior performance compared with two commercial industrial sensors. The contribution of this article lies in providing the analytical analysis and design of a novel DM current sensor for leakage current measurement, which achieves online per-phase insulation monitoring for industrial electrical assets.

Análise de desempenho e ciclo de vida de isoladores do sistema de distribuição de energia em ambientes de elevada agressividade

Neste estudo, foi avaliado o sistema de distribuição de energia frente ao desempenho em durabilidade de materiais e seus aspectos ambientais, com relação às análises do ciclo de vida (ACV) de isoladores elétricos de diferentes tecnologias, avaliando ensaios de desempenho individual e os principais impactos gerados sob a perspectiva “de berço ao túmulo”. Inicialmente, para o estudo de desempenho, foram considerados nove isoladores distintos, os quais foram submetidos aos ensaios de névoas limpa (48 h) e salina (360 h), com medidas de hidrofobicidade e de corrente de fuga, além da aplicação de poluentes artificiais. Após a realização dos testes, foram selecionados quatro destes isoladores com os melhores desempenhos, para então realizar os estudos de ACV por meio do software SimaPro 8.3. Pelos resultados de desempenho pode-se inferir que os isoladores que possuíam revestimentos de silicone e obtiveram os menores valores de corrente de fuga durante os ensaios de névoa limpa e salina, indicaram melhores atuações em ambientes agressivos. Já, por intermédio da ACV foram verificados os impactos ambientais dos isoladores de características equivalentes, uma vez que três desses possuíam a porcelana como material principal constituinte. O isolador híbrido de núcleo de resina com fibra de vidro revestido com silicone indicou os menores impactos ambientais devido à sua baixa quantidade de massa em relação aos outros, porém não foi possível verificar a qualidade dos dados implementados nos ICVs.Palavras-chave: Isoladores, rede de distribuição de energia, estudo de desempenho, análise do ciclo de vida, impactos ambientais.

Diamond-like carbon as gate dielectric for metal–insulator–semiconductor applications

Diamond-like carbon (DLC) has been studied as a dielectric material for future metal–insulator–semiconductor (MIS) technology. In this paper, ultrathin DLC films were deposited on silicon substrates by using the dc magnetron sputtering technique at various deposition voltages. The current–voltage characteristics indicated that the leakage currents of the MIS devices decreased with an increase in deposition voltages, and that a low leakage current ([Formula: see text] A/cm2) was achieved at −2 V bias voltage. The deposition voltage effects on the structures of films were investigated through Raman spectroscopy, which indicated that the sp3 bonding fraction decreased with an increase in the deposition voltage. The ramp-voltage breakdown test revealed high effective breakdown electric field ([Formula: see text]85 MV/cm) for the MIS device with the DLC film deposited at 1100-V deposition. Stress-induced leakage current measurement indicated that the DLC film exhibited excellent reliability.

Significantly improved breakdown strength and energy density of tri-layered polymer nanocomposites with optimized graphene oxide

Advanced electrostatic capacitors with great energy densities are urgently needed for practical applications in high-performance energy storage devices. Herein, poly (methyl methacrylate) (PMMA) is employed as two outer layers to provide excellent insulation characteristic, while ferroelectric copolymer poly (vinylidene fluoride-co-hexafluoropropene) P(VDF-HFP) with dispersed graphene oxide (GO) as the inter layer to enhance dielectric constant (K) and electrical displacement (D). The resulting trilayered nanocomposites exhibit highest electrical displacement difference (Dmax-Drem) value of 7.17 μC cm−2 at a low filler loading of 2 wt% GO under an electrical field of 300 MV m−1. The breakdown strength (Eb) of the designed trilayered nanocomposites are prominently improved at least one order of magnitude in comparison to other configuration films such as single-layered and reversed trilayer structures, as verified by the leakage current measurements and the finite element simulations with 3D models. The trilayered nanocomposites deliver an ultrahigh energy density of 10 J cm−3 and a discharged efficiency of 77% at an applied electrical field of 300 MV m−1, which is among the best energy storage performance under the identical electric field reported so far. The potential applications of the trilayered nanocomposites for energy storage have been further demonstrated by stable performance over a 40,000 charge-discharge cycling.

Humidity Robustness of Plasma-Coated PCBs

The reliability of printed circuit boards (PCB) is at risk due to continuous miniaturization. As a result, PCBs are more susceptible to external factors such as humidity, temperature, contamination, etc., which affect their general performance, leading to failure of electronic devices. Therefore, protection of the devices against these factors is gaining greatly in importance. Plasma polymerization is used as a method to form a protective barrier by applying plasma polymer films on PCBs. However, the humidity robustness of such plasma coatings on the PCB surface is unknown. In this work, several methods were used to characterize two types of plasma-coated PCBs based on 1H,1H,2H-perfluorodecyl acrylate precursor (single-layer and stacked coatings) upon exposure to humidity, temperature, and bias voltage. Modulated-temperature differential scanning calorimetry enabled thermal analysis of the plasma coatings. Electrochemical impedance spectroscopy in combination with the gravimetric moisture vapor sorption technique were used to study the interaction of these coatings with moisture and quantify the water uptake. The results revealed an only 2% increase of the capacitance of the coatings due to water uptake. Direct-current (DC) leakage current measurements were used to study the influence of a bias voltage applied between the electrodes on the coated PCBs upon exposure to cyclic climatic conditions. Electrical DC testing revealed the protective character of the stacked coating, which did not fail under the given stress conditions, in contrast to the single-layer plasma coatings.

Analysis of in-service composite insulators used in overhead railway traction

Polymeric based Composite insulators are extensively used for overhead rail electric traction system; these insulators play an important role in the traction electrification which supply power to the locomotives of train. Traction insulators are subjected to a variety of stresses, like mechanical, electrical, environmental, etc., these stresses act in unison, degradation and subsequent failure of traction insulator influences the safety of traction power supply system. To understand the phenomena of degradation and in-service aging, experimental investigations are conducted on in service traction insulators to identify and analyze the structural changes occurred in the field for a specified time, the insulators are of composite silicone polymeric materials rated for 25 kV. The electrical performance on the insulator samples is investigated using leakage current analysis and surface resistance measurements under normal and fog/moisture conditions using a specifically designed fog test chamber. The structural changes are studied by using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDAX), Fourier Transform Infra-Red (FTIR) and wettability measurements. The study highlights the in-depth analysis conducted on the performance of service insulators compares with the fresh, also suggests mitigation methods to overcome the probable failures in the field. Some interesting results obtained from the study are analyzed and presented.

Quantification of the Charge Consuming Phenomena under High‐Voltage Hold of Carbon/Carbon Supercapacitors by Coupling Operando and Post‐Mortem Analyses

AbstractEnhancing the operating voltage of supercapacitors (SCs), hence their specific energy, is important. However, long‐term hold at high voltage entails loss of capacitance, increase of resistance and internal pressure. Such detrimental effects could be reduced by obtaining quantitative information on the relative impact of the various mechanisms leading to the worsening of the SCs performance. Now, for a carbon/carbon supercapacitor in aqueous Li2SO4, a self‐consistent approach is used to assign leaking charge during high voltage hold to the charge: 1) distributed throughout the electrochemical cell (steady‐state leakage current measurements), 2) spent at each electrode for gases production (operando electrochemical mass spectrometry (EMS) analysis and pressure records), 3) utilized to oxidize the electrodes surface (from post‐mortem surface functionality determination by temperature programmed desorption (TPD)), and 4) used for other parasitic reactions.

Quantification of the Charge Consuming Phenomena under High-Voltage Hold of Carbon/Carbon Supercapacitors by Coupling Operando and Post-Mortem Analyses.

Enhancing the operating voltage of supercapacitors (SCs), hence their specific energy, is important. However, long-term hold at high voltage entails loss of capacitance, increase of resistance and internal pressure. Such detrimental effects could be reduced by obtaining quantitative information on the relative impact of the various mechanisms leading to the worsening of the SCs performance. Now, for a carbon/carbon supercapacitor in aqueous Li2 SO4 , a self-consistent approach is used to assign leaking charge during high voltage hold to the charge: 1) distributed throughout the electrochemical cell (steady-state leakage current measurements), 2) spent at each electrode for gases production (operando electrochemical mass spectrometry (EMS) analysis and pressure records), 3) utilized to oxidize the electrodes surface (from post-mortem surface functionality determination by temperature programmed desorption (TPD)), and 4) used for other parasitic reactions.

The Correlation between the Particle Morphology and the Electrochemical Stability for High-Ni Cathode and Understanding of the Mechanism of Parasitic Reaction.

Understanding the correlation between physical and electrochemical/chemical properties are significantly crucial for the development of electrode materials for lithium ion batteries. Among the cathode materials, high-Ni cathode with high energy density has a degradation issue of electrochemical performance due to the parasitic reaction at the cathode electrolyte interface. The core-shell or full concentration gradient materials consisting of a high-Ni core and a relatively high-Mn outer layer might be a potential candidate providing the improved electrochemical stability as well as cycle life performance. In this respect, the porosity of the final sintered particle is the key to affect the electrochemical stability indicating the side reaction with organic liquid electrolyte. The strategy tuning the particle porosity and density is applied to synthesize different particle size of transition metal precursor during co-precipitation. The structural characteristics are compared for the materials with different physical properties by utilizing ex-situ or in-situ X-ray diffraction, electron microscopy, electrochemical performances, and particle size distribution. The interfacial kinetic reaction between the Ni-rich cathode and a nonaqueous electrolyte at different SOCs is investigated by our home-built high-precision leakage current measurement system. This study can give us a clear sight for understanding the mechanism of parasitic reaction as well as providing a solution for the safety issue of the high-Ni cathode in lithium ion battery.