Leakage Current Characteristics Research Articles

Circuit modelling of aged‐polluted polymer insulators based on measured leakage current characteristics

A new equivalent circuit model for aged-polluted polymer outdoor insulators is proposed here. The structure of the model is constructed as such that it can be applied in investigating the effect of insulator aging and dry band discharge intensity on leakage current (LC) characteristics. To implement the capability of modelling aged insulators, the measured leakage currents from laboratory tests on field aged MV insulators with different level of aging and hydrophobicity were examined. Furthermore, the samples were artificially polluted and the corresponding measured leakage currents from laboratory tests were employed as references. The proposed circuit model can consider the effect of pollution by its topology and represents the aging phenomenon of insulator by the changes in the values of its elements. High similarity between test results and model outputs has confirmed model ability to represent aging effect on LC characteristics. Finally, mathematical equations for model parameters in terms of aging level are extracted using curve fitting, in order to predict the age and life-time of polymer insulator.

Investigation of electrical and magnetic properties of rare-earth based double perovskite: Dy2CoMnO6

In this report, the detailed studies of structural, dielectric, impedance, conductivity, electrical modulus, and leakage-current characteristics of the oxide method synthesized -double perovskite Dy2CoMnO6 ceramic have been provided. From the Rietveld analysis, the structure of the compound is found to be monoclinic. The frequency-temperature dependence of the dielectric properties is discussed by using the Maxwell-Wagner model. The analysis of the Nyquist plot suggests the occurrence of grain and grain boundary effect in the compound. The frequency response of conductivity analysis was explained by Jonscher’s power law. The conduction mechanism follows the space charge limited conduction (SCLC) process which is obtained from leakage current analysis.

Polymeric Insulator Conditions Estimation by Using Leakage Current Characteristics Based on Simulation and Experimental Investigation.

The current work contributes an estimate of the time-frequency characteristics of a leakage current in assessing the health condition of a polluted polymeric insulator. A 33 kV polymer insulator string was subjected to a series of laboratory tests under a range of environmental conditions, including pollution, wetting rate (WR), non-soluble deposit density (NSDD), and non-uniform distribution pollution (FT/B). The temporal and frequency features of the leakage current were then extracted and used as assessment indicators for insulator conditions based on laboratory test findings. Two indices were generated from the leakage current waveform in the time domain: the curve slope index (F1), which is determined by measuring the inclination of the curve between two successive time peaks of the leakage current, and the crest factor indicator (F2). The frequency domain of the leakage current signal was used to calculate the other two indices. These are the odd harmonic indicators derived from the odd frequency harmonics of the leakage current up to the 9th component (F3) and the 5th to 3rd harmonics ratio (F4). The findings showed that the suggested indicators were capable of evaluating insulator conditions. Finally, the confusion matrix for the experimental and prediction results obtained with the proposed indices was used to assess which indicator performed the best. Therefore, the analysis suggests an alternative and effective method for estimating the health condition of a polluted insulator through leakage current characteristics obtained in the time and frequency domains.

Structural, dielectric and electrical characteristics of Bi3.9Sm0.1Ti3O12 ferroelectrics

In this article, detailed investigations on structural, dielectric, impedance, and leakage current characteristics of samarium modified bismuth titanate of chemical formula (Bi3.9Sm0.1Ti3O12), prepared by cost-effective solid-state reaction technique (with 850 °C calcination and 900 °C sintering temperatures), have been discussed. The X-ray structural study has shown that the compound crystallizes in orthorhombic symmetry with the B2ab space group. SEM micrograph at room temperature displays the grains are uniformly distributed on the surface with a very small amount of voids. The electrical measurements of the compound were carried out by a phase-sensitive (LCR) meter over broad temperature (25 °C–400 °C) and frequency (1 kHz-1 MHz) ranges. The hysteresis loops between polarization (P) and electric field (E) at different temperatures show the existence of ferro-electricity in the compound. All the electrical characteristics have shown significant modification on even a small substitution (i.e., 10%) of trivalent rare earth element (i.e., samarium) in the bismuth site. The leakage current study at various temperatures shows the existence of Ohmic conduction in the compound. The value of leakage current makes the sample preferable for electronic devices.

Leakage Current Characteristics of Polycrystalline Bifeo3 Thin Films Affected by Thickness-Dependent Domain Wall Currents

Leakage Current Characteristics of Polycrystalline Bifeo3 Thin Films Affected by Thickness-Dependent Domain Wall Currents

Fatigue and leakage current characteristics of lead free bilayer thin film structures

Multilayer thin films of (Ba0.50Sr0.50)TiO3 (BST) and Ba(Zr0.15Ti0.85)O3 (BZT) were deposited on Pt(111)/SiO2/Si(111) substrates using Pulsed LASER Deposition (PLD) technique. This manuscript reports on the role of a paraelectric layer in the stack of multilayers on certain key aspects related to crystallographic orientation, interface morphology, tunability, and energy storage properties. The incorporation of paraelectric layer is found to strongly influence the electrical properties of a ferroelectric layer whose composition is at the morphotropic phase boundary. A possible methodology to obtain enhanced electrical properties in multilayer structures based on electric field distribution across different layers in the stack is demonstrated. Incorporation of a paraelectric layer results in restricting the migration of oxygen vacancies due to the presence of the internal bias field. Retention of remanent polarization when driven by 109 bipolar switching cycles and other fatigue properties are reported. Leakage current characteristics were evaluated and the fitting of the experimental data with various conduction mechanisms indicate that different mechanisms are responsible for leakage current conduction as a function of bias voltage. A relatively high power density of >12 MW/cm3 with an energy storage density efficiency of >70%, tunability values comparable with multilayer thin films grown on single crystal substrates are some of the attributes of the multilayer structure.

Research on Leakage Current Waveform Spectrum Characteristics of Artificial Pollution Porcelain Insulator

The surface discharge development processes of polluted porcelain insulators for power transmission lines are tightly related with the development of leakage current (LC), the characteristics of LC, the insulating condition, and discharge intensity of the insulator surface have an important significance for revealing the contamination discharge state of insulators. In order to analyze the LC characteristics of porcelain insulators in the process of pollution flashover, artificial pollution flashover tests on porcelain insulators were conducted in the artificial fog cabinet, and the characteristics of LC waveforms in time-domain and frequency-domain were simultaneously measured and analyzed during the tests. The results indicated that the amplitude of LC, fundamental harmonic, the third harmonic, and fifth harmonic had a strong correlation, the maximum of LC(Im), the rate of total harmonics (THD), and the phase difference of fundamental harmonic (θ) were used for the representation of the characteristics of the LC waveform. The LC has the characteristics of high amplitude, low proportion harmonic, and small phase difference between the fundamental harmonic and voltage before the flashover occurrence. The test results provide effective reference for porcelain insulators in pollution flashover forecasting.

Analysis and simulation of reddish overshoot in active matrix organic light-emitting diode display with varying p-doped hole transport layer concentrations

A typical organic light-emitting diode (OLED) display has common organic layers between adjacent pixels, which ensure ease of manufacturing process and efficiency in operation. The p-doped hole transport layer (p-HTL) has low electrical resistivity, which results in a high efficiency OLED. However, the low resistivity results in various side effects, including color crosstalk and overshoot, mainly due to lateral leakage current flowing through this layer. Furthermore, virtual reality and augmented reality devices that require extremely high pixels per inch (PPI) and superior image quality are very sensitive to lateral leakage current. In this study, we propose a passive driving panel based on RGB top emission to efficiently measure and model the lateral leakage current characteristics according to the p-HTL concentration. In addition, we constructed a 1.5-inch active matrix organic light-emitting diode panel based on the n-type low-temperature polycrystalline silicon 4T2C pixel circuit. Subsequently, we quantitatively analyzed the reddish overshoot phenomenon during the black to white image transition. This effect was reduced at p-HTL concentrations under 1%. Finally, we analyzed the overshoot mechanism through SPICE simulations and realized the optimal lateral resistance value of the common organic layer for each PPI. • Passive driving OLED and AMOLED display with varying p-HTL concentration. • Effect of the lateral leakage current on the AMOLED display. • Analysis of reddish overshoot mechanism through SPICE simulations and accurate OLED modeling. • An optimal lateral resistance value for the common organic layer is proposed for each PPI.

A novel 3D MnNi2O4@MnNi2S4 core-shell nano array for ultra-high capacity electrode material for supercapacitors

In this work, a novel 3D MnNi2O4@MnNi2S4 core-shell nano array was successfully grown on nickel foam (NF) via in-situ growth method, which omitted the addition of binder and conductive additive and the complicated electrode preparation process. The MnNi2O4@MnNi2S4 possesses a unique nanorod@nanosheet core-shell structure, which can provide abundant active sites near the electrode interface for rapid electrochemical reaction, so the MnNi2O4@MnNi2S4 electrode materials exhibit high specific capacitance and excellent electrochemical properties. It is worth noting that the specific capacitance of the MnNi2O4@MnNi2S4 reaches 3578.57 F g−1 at the current density of 1 A g−1, and 1009.52 F g−1 at the current density of 20 A g−1. When the current density is 15 A g−1, the specific capacitance retention rate reaches 93.1% after 5000 cycles, showing good cycling performance. Moreover, the MnNi2O4@MnNi2S4//AC asymmetric device also exihibits low leakage current and excellent self-discharge characteristics. So, the MnNi2O4@MnNi2S4 is an excellent electrode material for supercapacitors.

Improved dielectric constant and leakage current characteristics of BaTiO3 thin film on SrRuO3 seed layer

The fabrication of high-k BaTiO3 (BTO) films for applications such as multilayer ceramic capacitors or dynamic random access memory has been achieved via the ex-situ crystallization of amorphous BTO into perovskite structure through post-deposition annealing (PDA). However, high-temperature PDA at temperatures exceeding 700 °C results in the severe degradation of BTO properties. In other words, ex-situ crystallization via PDA results in an increased dielectric constant but is accompanied by inferior leakage current characteristics caused by rough surface morphologies and defects such as voids and cracks. In this study, we demonstrate the in-situ crystallization of BTO films by introducing a high-quality SrRuO3 (SRO) film as a seed layer. The SRO film is deposited using rf magnetron sputtering at 270–350 °C, and stoichiometric SRO films are obtained on SiO2, Al2O3, and TiN substrates by controlling the growth temperature; subsequently, rapid thermal annealing at 700 °C is conducted to crystallize the SRO film. The polycrystalline SRO film on the TiN substrate exhibits excellent morphology with uniform grains as well as a continuous and smooth surface, whereas the SRO films on the SiO2 and Al2O3 substrates exhibit rough and discontinuous surfaces. The SRO seed layer on TiN permits the in-situ growth of crystalline BTO films at a relatively low temperature of 500 °C featuring a high dielectric constant of 160 and a low leakage current density of 9.5 × 10−7 A/cm2 at 0.8 V, which are 2.2 and 3.4 × 107 times improved compared with those of the ex-situ crystallized BTO film on bare TiN, respectively.

Hexagonal Boron Nitride Passivation Layer for Improving the Performance and Reliability of InGaN/GaN Light-Emitting Diodes

We introduce a low temperature process for coating InGaN/GaN light-emitting diodes (LEDs) with h-BN as a passivation layer. The effect of h-BN on device performance and reliability is investigated. At −5 V, the leakage current of the h-BN passivated LED was −1.15 × 10−9 A, which was one order lower than the reference LED’s leakage current of −1.09 × 10−8 A. The h-BN layer minimizes the leakage current characteristics and operating temperature by acting as a passivation and heat dispersion layer. With a reduced working temperature of 33 from 45 °C, the LED lifetime was extended 2.5 times following h-BN passivation. According to our findings, h-BN passivation significantly improves LED reliability.

Leakage current characteristics and ageing assessment technology of roof arrester under ultra harmonics overvoltage

The large leakage current of the roof arrester caused by the high-frequency resonant overvoltage on the high-speed train occurs intermittently, which will cause the arrester to overheat locally. In this work, the overheating issue of the arrester under Ultra Harmonics Overvoltage is studied. Then, the relationship between the active power and the voltage (including amplitude and frequency) of the arrester is investigated, and the impact mechanism of the harmonic voltage on the overheating fault of the arrester is analysed based on experiments in this work. It is found that the total leakage current of the arrester is proportional to the amplitude and frequency of the applied voltage. The internal resistance of the arrester is independent of the amplitude of the voltage, but it will decrease with the increase of the frequency. The main reason that leads to thermal breakdown of the arrester valve under high-frequency harmonic voltage is the heating power elevation of the arrester valve. The research study can provide theoretical basis and data support for the design, type selection and monitoring of the high-speed train roof arrester.

Enhancement of Energy-Storage Density in PZT/PZO-Based Multilayer Ferroelectric Thin Films.

PbZr0.35Ti0.65O3 (PZT), PbZrO3 (PZO), and PZT/PZO ferroelectric/antiferroelectric multilayer films were prepared on a Pt/Ti/SiO2/Si substrate using the sol–gel method. Microstructures and physical properties such as the polarization behaviors, leakage current, dielectric features, and energy-storage characteristics of the three films were systematically explored. All electric field-dependent phase transitions, from sharp to diffused, can be tuned by layer structure, indicated by the polarization, shift current, and dielectric properties. The leakage current behaviors suggested that the layer structure could modulate the current mechanism, including space-charge-limited bulk conduction for single layer films and Schottky emission for multilayer thin films. The electric breakdown strength of a PZT/PZO multilayer structure can be further enhanced to 1760 kV/cm, which is higher than PZT (1162 kV/cm) and PZO (1373 kV/cm) films. A recoverable energy-storage density of 21.1 J/cm3 was received in PZT/PZO multilayers due to its high electric breakdown strength. Our results demonstrate that a multilayer structure is an effective method for enhancing energy-storage capacitors.

Leakage Current Characteristics of Atomic Layer Deposited Al-Doped TiO2 Thin Film for Dielectric in DRAM Capacitor

We researched the reduction of leakage current by Al doping in TiO2 thin film. During the TiO2 thin film deposition process, Al2O3 thin film deposition was used for Al doping. XPS analysis showed that the greater the amount of Al doping in TiO2 thin film, the fewer oxygen vacancies were found. The n-type characteristic of TiO2 thin films is reduced as oxygen vacancies are reduced. An anatase (211) peak was detected by GIXRD analysis, and crystallinity was reduced with greater Al doping; the full width half maximum showed the crystalline size was reduced. UV-visible analysis showed the energy bandgap increased as the crystalline size became smaller, and I-V measurements showed the current density decreased to 3 × 10−4 A cm−2 (As-dep TiO2: 10−1 A cm−2) with Al doping. The dielectric constant remained above 20 even when doped with Al, confirming the superior properties of Al-doping TiO2 thin film over conventional TiO2 thin films.

P‐16.12: Development of High Performance In‐cell Touch Panel based on Oxide TFT

In‐cell touch panel based on oxide TFT possesses excellent display performance, high SNR and supports LPWG function with lowest power consumption. However, due to the discrete electrode VCOM and low leakage current characteristics of oxide TFT, it is easy to cause static electricity and charge residual. In view of above problems, this paper fully introduces the product design and process of targeted optimization.

Accurate Modeling Methodology of Laterally Diffused Metal-Oxide Semiconductor Leakage Current for Electro-Static Discharge Protection Circuit Design.

A modeling method using juncap2 physical compact model with SRH (Shockley-Read-Hall), TAT (Trap-Assisted-Tunneling), BBT (Band-to-Band Tunneling) effects is presented for the leakage current in a laterally diffused metal-oxide semiconductor (LDMOS). The juncap2 model is successfully combined with BSIM4 model and it is validated with measurement data. The model accurately predicts the leakage current characteristics for the entire bias region and temperature.

(001)‐oriented BiFeO3 films integrated on Si with enhanced electrical performances

AbstractHighly (001)‐oriented pure‐phase BFO films were prepared on traditional Si substrates via radio frequency magnetron sputtering (RFMS). The crystallinity of the films is found to be increased, that is, higher degree of (001) texture, larger grain size, less grain boundary, denser surface morphology, and better thickness uniformity, with increased film thickness. These factors have significant influences on the electrical properties of BFO films, that is, dielectric response, as well as ferroelectric polarization and leakage current characteristics. The 240‐nm‐thick film exhibits relatively poor electrical properties compared with other three thicker films, which is mainly due to its small grain, the enhancement of the clamping effect of neighboring grains, and the absence of domain walls. The essential roles of the evolution and distribution of grains/domains and defect charges in leakage mechanism and ferroelectric switching polarization were also investigated systematically. It was found that 600‐nm‐thick BFO film has the lowest leakage current density (as low as 1.8 × 10−6 A / cm2 @ 90 kV/cm) and followed a mixed SE or SCLC conduction behavior, while the leakage behavior in other films is dominated by SE and P‐F currents. All (001)‐BFO films have a giant electrical polarization which is solely originated from the contribution of ferroelectric domain switching, and it has lower switching voltage and faster switching rate in thicker films.

Investigation on the leakage current characteristics of large size GaN diodes

The leakage mechanism of large size GaN p–i–n diodes is studied, and the possible reasons are analyzed. It is found that (i) the leakage current of most diode chips is not proportional to their area, and the leakage problem deteriorates seriously when the size of the device increases; (ii) the open circuit voltage of the photovoltaic device decreases with the increasing leakage current of GaN diodes; and (iii) low density nanotubes are detected in larger size GaN diodes, which is one of the important reasons for the large leakage of large size GaN diodes.

Damage Effect of ALD-Al2O3 Based Metal-Oxide-Semiconductor Structures under Gamma-Ray Irradiation.

The radiation response of Al2O3 on silicon substrate under gamma-rays is studied in this article. The atomic layer deposited Al2O3 based metal-oxide-semiconductor structures were irradiated under gamma-ray with the total dose of 1.2 Mrad(Si)/2.5 Mrad(Si)/4 Mrad(Si). The generation, transportation and trapping characteristics of radiation induced charges were studied by using electronic, physical and chemical methods. Firstly, the radiation induced trapped charge density in Al2O3 is up to 1012 cm−2, with the effective trapping efficiency of 7–20% under irradiation. Secondly, the leakage current through Al2O3 changes little with the increase of radiation total dose. Thirdly, oxygen vacancy in Al2O3 and O dangling bonds and Al-Si metallic bonds at Al2O3/Si interface are dominant radiation induced defects in Al2O3/Si system, and the valence band offset between Al2O3 and Si is found to decrease after irradiation. From the results we can see that Al2O3 is radiation resistant from the aspect of leakage current and crystallization characteristics, but the radiation induced charge trapping and new defects in Al2O3/Si structure cannot be ignored. This paper provides a reference for the space application of Al2O3 based MOS devices.

Reliability Analysis on TiN Gated NMOS Transistors

Compared to poly Si gate, metal gate has no gate depletions and experiences inversion capacitance gain, which makes an advantage for devices scaling. In this paper, we investigated the gate oxide leakage current and Time Dependent Dielectric Breakdown (TDDB) characteristics of TiN and poly Si electrodes with a 3.5 to 5 nm SiO2 dielectric thickness range. According to the Transmission Electron Microscope (TEM) analysis there is difference in oxide thickness. The SiO2 thickness of TiN gate electrode has been reduced by ~0.25 nm, considerably because of a scavenging effect. We normalized the reduced SiO2 thickness with an electrical oxide field, and there were no differences between the two electrodes in gate leakage current, accumulation breakdown voltage (BV), and accumulation TDDB lifetime. Therefore, we found the scavenging effect of TiN electrodes seems to affect little the leakage current and TDDB reliability of SiO2 dielectric. On the other hand, the BV and TDDB lifetime of TiN electrode in the inversion region are little bit better than that of the poly electrode. We think this differences are originated from the difference between TiN/SiO2 and poly Si/SiO2 interfaces.