Leakage Current Properties Research Articles

Effect of Zinc Oxide Nanofiller on the Dielectric Thermal and Optical Properties of Polypropylene

In the field of electrical engineering, polymer nano-composites have been alluring owing to their excellent dielectric properties. At contrasting loading concentration, they are embodied with nano-fillers for boosting their dielectric properties. This paper aims to investigate the dielectric properties, thermal properties, surface hydrophobicity, surface leakage current and optical properties of polypropylene (PP) when reinforced with Zinc Oxide (ZnO) nano-fillers to find its suitability as a dielectric material. With the introduction of ZnO fillers in PP, improvements of dielectric properties have been observed. Thermal stability is observed to be more or less the same in terms of decomposition temperature, temperature corresponding to maximum rate of decomposition, endothermic and exothermic peak. Better surface hydrophobicity and leakage current of lower magnitude are observed even with ZnO filler loading. UV absorption has been found to have increased after ZnO nano-filler loading.

Direct magnetoelectric and magnetodielectric studies of electrospun Ba2Ni2Fe12O22–Pb(Zr0.52Ti0.48)O3 core–shell nanofibers

This article reports the synthesis of barium nickel hexaferrite-lead zirconium titanate (Ba2Ni2Fe12O22-Pb(Zr0.52Ti0.48)O3) core-shell nanofibers through sol-gel electrospinning method. Direct magnetoelectric and magnetodielectric coupling studies were performed on the synthesized electrospun core-shell nanofibers. The structure, functional, morphological, magnetic, dielectric, leakage current, and ferroelectric properties were also analyzed. X-ray diffraction studies revealed the hexagonal crystal structure of the core and the tetragonal structure of the shell. The Fourier transform infrared spectroscopy analysis showed the fundamental functional groups present in the nanofibers. Scanning electron microscopy studies showed that the diameter of the nanofibers was 404 nm, and elemental analysis by energy-dispersive X-ray spectroscopy showed the stoichiometric formation of Ba2Ni2Fe12O22 and Pb(Zr0.52Ti0.48)O3 in the composite. Microstructure studies using a transmission electron microscope revealed the formation of core-shell nanofibers with a clear interface between the magnetic Ba2Ni2Fe12O22 (BNFO) core and the ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) shell. Selected-area electron diffraction analysis showed the Ba2Ni2Fe12O22 and Pb(Zr0.52Ti0.48)O3 phases to be highly crystalline. At room temperature, the synthesized nanofibers exhibited well-defined ferroelectric and magnetic hysteresis loops. Dielectric and leakage current studies were performed. Direct magnetoelectric and magnetodielectric studies were also performed to study the cross-coupling between the ferroic orders of the nanofiber. Moreover, using Landau’s energy expression, the type of magnetoelectric coupling was proved to be biquadratic. The enhanced magnetoelectric behavior of the Ba2Ni2Fe12O22–Pb(Zr0.52Ti0.48)O3 core–shell nanofiber confirms that the nanofiber is a potential candidate for high-performing magnetic field sensors, magnetically tuned capacitors, multimedia transducers, and spintronic devices.

Role of molybdenum doping in reducing leakage current density of BiFeO3 based thin film devices

Leakage current properties of pure and Mo-doped BiFeO` (BFO) thin films have been studied in order to identify the cause of high leakage currents. Interestingly, it was observed that the leakage current density reduced by more than two orders of magnitude upon Mo doping at Fe site of BFO. According to J-V characteristics, the leakage current density decreased from 1.101 × 10-6 A/cm2 to 9.4 × 10-8 A/cm2 at an applied bias voltage of 2.75 V with Mo substitution. These findings suggest that oxygen vacancies, rather than Fe2+ ions, are the primary cause of BFO's high conductivity.

RTV-SiR based composites aged in a multi-stressed environment under AC and bipolar DC voltages

Silicone rubber-based polymers are gradually replacing traditional insulators in outdoor applications due to their numerous advantages, in particular high hydrophobicity that is important for suppressing leakage current and hence surface flashover. However, the main problem with polymeric composites is their aging when exposed to environmental stresses causing loss of their desired properties and expected lifetime. In this work, aging behavior of three types of room temperature vulcanized silicon rubber (RTV-SiR) loaded with nano-silica and micro-ATH is studied. Samples of the materials with different specifications were fabricated and exposed to various environmental stresses in two specially designed weather chambers under both AC and bipolar DC voltages for a time period of 9000 hours. Thereafter, diagnosis was performed for identifying the degree of deterioration using several techniques. These include hydrophobicity classification, measurements of leakage current and mechanical properties, Fourier transform infrared spectroscopy, and Thermogravimetric analysis. Results of the conducted experiments indicated stronger degradation of the desired properties under positive DC stress as compared to the AC and negative DC voltages. Moreover, silicone rubber doped with nano-sized particles of silica filler demonstrated better anti-aging performance as compared to its micro-ATH filled counterpart.

Enhanced electrocaloric response and energy storage performance of Li‐substituted BaTiO3 ceramics

AbstractRecently, ferroelectric and antiferroelectric ceramic materials have gained a lot of interest for the development of environment‐friendly highly‐efficient electrocaloric refrigeration and energy‐storage devices. In this work, lead‐free Ba1−xLixTiO3 ceramics with x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05 were synthesized by the conventional solid‐state reaction method, and the effect of Li doping on dielectric, leakage current, ferroelectric, electrocaloric, and energy storage properties of BaTiO3 ceramics was systematically investigated. The XRD and Raman studies confirmed that the structure of Ba1−xLixTiO3 remains tetragonal as for BaTiO3. The Li substitution shifted the phase transition (TC) of BaTiO3 slightly towards the lower temperature side. Significant drop in leakage current was observed with an addition of Li content. The maximum values of the electrocaloric effect (ΔT), electrocaloric responsivity, and coefficient of performance were found to be 1.44 K, 0.24 × 10−6 K m/V, and 5.75, respectively, for x = 0.04 at an applied field of 60 kV/cm near the Curie temperature. The maximal value of energy storage density was found to be 0.42 J/cm3 with an energy storage efficiency of 60% for x = 0.05. Our results suggested that lead‐free Ba1−xLixTiO3 ceramic material is a promising candidate for potential applications in solid‐state refrigeration technology and high‐efficiency energy storage devices.

Achieving High Dielectric Constants in Tetragonal Single‐Phase ZrHfO2 Thin Films through the Atomic Layer Deposition Process Using a Mixed Precursor

Herein, the deposition of homogeneous ZrxHf(1−x)O2 (x < 1) thin films for dynamic random‐access memory (DRAM) capacitor dielectric layers by atomic layer deposition (ALD) using a mixed precursor mixture of two precursors is investigated. ZrO2‐ and HfO2‐based thin films are widely used as capacitor dielectric layers because of their high dielectric constant (k) values and low leakage current properties. Herein, particularly, films with mixed structures of ZrO2/HfO2 are investigated because ZrO2 supports the growth of HfO2 in the tetragonal phase. However, the mixed structures deposited by ALD remain inhomogeneous even after the annealing process. The inhomogeneity results in part of the HfO2 remaining in the monoclinic phase, which reduces the k value. Herein, the formation of homogeneous tetragonal‐phase ZrxHf1−xO2 using a mixed precursor consisting of CpZr and CpHf precursors is investigated. The formation of the tetragonal phase in the ZrxHf(1−x)O2 thin films is determined through chemical and structural analysis. The variation of the electrical properties with the Zr/Hf concentration ratio is investigated. The electrical properties are enhanced compared to laminated ZrO2/HfO2 and single thin films.

Improved energy storage density and energy efficiency of Samarium modified PMNT electroceramic

We report the improved energy storage density and efficiency after 2.5% of Samarium substitution in ferroelectric Pb[(Mg1/3Nb2/3)0.80Ti0.20]O3 (PMNT) electroceramic. The microstructure and surface morphology were analyzed and correlated with various functional properties. The energy storage density, leakage current density, ferroelectric and dielectric properties were investigated thoroughly, indicating that Samarium's substitution significantly modified the microstructure, the dielectric strength, breakdown electric field, and turned ferroelectric PMNT to relaxor ferroelectrics. Due to the relaxor nature, the gap between remanent polarization and maximum polarization increases with the substitution of Samarium in PMNT matrix, which further increases the recoverable energy storage density and energy efficiency. A nearly 100% increase in recoverable energy density and efficiency was obtained at an electric field strength of 35 kV/cm at room temperature (∼296 K). The electroceramic shows maximum energy density near the ferroelectric phase transition temperature (325 K–345 K) region and provides a moderate energy storage density for possible applications in power microelectronics.

Tunable dielectric and energy storage properties in nonstoichiometric NaNbO3 thin films

Defect engineering is an essential strategy to achieve the tunable functionalities in perovskite oxides containing volatile elements. In this work, we reported the influence of sodium deviation on the structural and electrical properties of sol-gel-derived NaNbO3 (NNO) thin films. Sodium deviation in NNO thin films was controlled by the level of x = Na/Nb ratio (x = 0.90, 1.00, 1.10, and 1.20) in the precursor solution. It is found that sodium deviation in NNO thin films has little influence on the crystalline structure, but the dielectric, leakage current, and energy-storage properties are closely related to the sodium deviation. Although excess sodium (i.e., x = 1.10) in the precursor solution could improve the leakage current and dielectric loss, the large polarization and superior energy storage density are observed in sodium-deficient (i.e., x = 0.90) NNO thin film. These results indicate sodium deviation as a valuable tool to balance the targeted properties of sodium-based perovskite oxides for potential applications.

Optimization of Self-Heating Driven Leakage Current Properties of Gate-All-Around Field-Effect Transistors Using Neural Network Modeling and Genetic Algorithm

As the technology nodes of semiconductor devices have become finer and more complex, progressive scaling down has been implemented to achieve higher densities for electronic devices. Thus, three-dimensional (3D) channel field-effect transistors (FETs), such as fin-shaped FETs (FinFETs) and gate-all-around FETs (GAAFETs), have become popular as they have increased effective surface areas for the channels (Weff), owing to the scaling down strategy. These 3D channel FETs, which have completely covered channel structures with gate oxide and metal, are prone to the self-heating effect (SHE). The SHE is generally known to degrade the on-state drain current; however, when AC pulsed inputs are applied to these devices, the SHE also degrades the off-state leakage current during the off-phase of the pulse. In this study, an optimization methodology to minimize leakage current generation by the SHE is examined.

The Hidden Potential of Polysilsesquioxane for High‐k: Analysis of the Origin of its Dielectric Nature and Practical Low‐Voltage‐Operating Applications beyond the Unit Device

AbstractLow‐voltage‐operating high‐performance organic field‐effect transistors (OFETs) are regarded as the building blocks of analog and digital integrated circuits for next‐generation electronics. To fulfill this, such an OFET must have high‐dielectric constant (k) characteristics for increasing the capacitance values to make enough of a field‐effect charge, a hydrophobic surface that does not cause charge trapping, and a low leakage current property to guarantee operating stability. This study demonstrates a new strategy to induce high‐k characteristics (>8) with durable polysilsesquioxane (PSQ)‐based dielectrics. This strategy involves realizing a dipolar side‐chain reorientation under an electric field and its applications to low‐voltage‐driving OFETs showing high field‐effect mobility levels as high as 27 cm2 V–1 s–1. Different PSQs are characterized, and the differences in their characteristics lead to distinct polarization phenomena, resulting in different hysteresis behaviors during device operation. The printed unit devices can also be fabricated on flexible platforms and integrated devices through these materials and show robust switching or memory performances under low‐voltage‐operation conditions. Therefore, this facile but powerful synthesis strategy for high‐k PSQ dielectrics can pave a new path for the production of practical printable high‐k dielectrics for organic electronics and hence realize next‐generation integrated electronics.

Influence of HfO2 and SiO2 interfacial layers on the characteristics of n-GaN/HfSiOx capacitors using plasma-enhanced atomic layer deposition

We investigated the growth per cycle (GPC) for SiO2 and HfO2 on n-GaN/native oxide and p-Si/SiO2 substrates by plasma-enhanced atomic layer deposition using tris(dimethylamino)silane and tetrakis(dimethylamino)hafnium precursors, respectively, and O2 plasma gases. On the basis of the estimated GPC, we also examined the characteristics of n-GaN/Hf0.57Si0.43Ox/Pt capacitors with an inserted interfacial layer (IL) such as subnanometer-thick HfO2 and SiO2. We found that the GPC for SiO2 on n-GaN/native oxide was slightly smaller than that on p-Si/SiO2, whereas the GPC for HfO2 was the same on both substrates. The GPC for ALD-SiO2 could be reasonably plotted on the basis of the relationship between the GPC and the difference in electronegativity between the metal and oxygen in the metal-O underlayers including native oxide (Ga2O3) on GaN. On the basis of the GPC on n-GaN, Hf0.57Si0.43Ox (23 nm) capacitors were fabricated without and with a HfO2-IL (0.3 and 0.5 nm) or SiO2-IL (0.3 and 0.6 nm). These capacitors exhibited similar leakage current properties and a high breakdown electric field greater than 8.3 MV cm−1. No frequency dispersion and a flatband voltage (Vfb) hysteresis smaller than 50 mV were observed for all of the capacitors. Compared with the SiO2-IL [Si-rich HfSiOx (Si: > 0.43)] capacitors, the HfO2-IL [Hf-rich HfSiOx (Hf: > 0.57)] capacitors showed a smaller interface state density [(1.2–1.7) × 1011 cm−2 eV−1 at −0.4 eV from the conduction band] and a smaller negative Vfb shift. Therefore, the Hf-rich HfSiOx (Hf: > 0.57) grown using a HfO2-IL at the n-GaN/HfSiOx interface plays a substantial role in improving the electrical properties of n-GaN/HfSiOx capacitors.

Organic–inorganic hybrid gate dielectric using bifunctional polyhedral oligomeric silsesquioxane for low‐voltage organic thin‐film transistors

AbstractHerein, we report the facile fabrication of rationally designed, high‐performance organic–inorganic hybrid dielectric films constructed by combining a one‐step solution processing and ultraviolet (UV) irradiation under ambient conditions. For the exceptional dielectric properties and facile fabrication process, we use bifunctional polyhedral oligomeric silsesquioxane (POSS) with UV cross‐linking and hydrophobic properties to prepare precursor solutions for the hybrid dielectric films. The bifunctional POSS enables the fabrication of a dense network of hybrid films with UV curing at under ambient conditions. The prepared hybrid gate dielectrics exhibit high capacitance (~300 nF/cm2), exceptional surface smoothness (root‐mean‐square roughness <0.4 nm), and excellent leakage current properties (10−6 A/cm2 at 2 MV/cm). In addition, the hydrophobic function of bifunctional POSS enables the low surface energy of fabricated hybrid gate dielectrics without further treatment. Pentacene‐based organic thin‐film transistors, fabricated with a hybrid dielectric, function well at low voltage with excellent thin‐film transistor performances.

Temperature dependence of ferroelectric property and leakage mechanism in Mn-doped Pb(Zr0.3Ti0.7)O3 films

High-quality ferroelectric films of Mn-doped Pb(Zr0.3Ti0.7)O3 (PMZT) were prepared using the sol-gel method, and the temperature dependence of ferroelectric, dielectric, and leakage current properties (J–E) were explored in detail using the top electrode/ferroelectric films/bottom electrode capacitor heterostructure. The enhancement of polarization and dielectric properties by element doping is clearly observed by 3% Mn-doping. Such enhancement is beneficial for the application of these films in ferroelectric random-access memory. In addition, the analysis of leakage current reveals symmetric behavior with 3% Mn-doping and the leakage current density gradually increases with increasing temperature, which may be due to the movement of domain wall and oxygen vacancy. The dominant leakage current conduction mechanism is bulk-limited ohmic or interface-limited Schottky emission conduction within a wide temperature range. The results might be meaningful for further work on ferroelectric electrical devices with improved ferroelectric and dielectric properties.

Impact of electrode materials on microstructure, leakage current and dielectric tunable properties of lead-free BSZT thin films

Lead-free ferroelectric sol-gel thin films derived from barium strontium titanate (Ba0.85Sr0.15Zr0.1Ti0.9O3, BSZT) were deposited onto two types of electrode: (i) noble metallic Pt- and (ii) conductive oxides LaNiO3- and SrRuO3-coated silicon substrates. The present studies demonstrate that electrode materials impact significantly on morphology, crystallographic orientation, lattice mismatch-induced microstrains and electrical properties of BSZT thin films. Highly (100)-textured BSZT thin films with the highest crystallinity and lowest microstrain were found on conductive oxide electrodes, whereas Pt electrodes showed polycrystalline. Capacitors with oxide LaNiO3 electrode display predominated Schottky emission with a rather low leakage current density ~4.68 × 10−8 A/cm2, while Pt electrode capacitors indicate space-charge limited conduction. Dielectric characterizations in the frequency range of 103–5 × 106 Hz and the dc electric field up to ±800 kV/cm show that the permittivity, loss tangent, and tunability of BSZT films also strongly depend on the electrode materials used. The optimal dielectric tunability with a large figure of merit (FOM ≈ 22.53) and low dielectric loss (tanδ ≈ 2.9%), was found to be 66% for BSZT thin films on the conductive LaNiO3 electrode, suggesting that the as-deposited ferroelectric films are promising candidates for applications in tunable microwave elements and related electronic devices.

Effects of Mn-doping on anti-fatigue and anti-leakage current characteristics in KNN single crystals

In this work, we illuminate the influences of Mn doping on the domain structure, ferroelectric properties, and piezoelectric properties of K0.4Na0.46NbO3 (KNN) lead-free single crystals. We simultaneously obtained a low leakage current and high anti-fatigue properties in Mn:KNN single crystals. The valence state of the Mn ion changes after annealing from trivalent to bivalent. The micro-domain structure images show that the domain structure of Mn-doped KNN single crystals is more complex with a smaller size. In addition, the occupying mechanism of Mn in KNN is discussed. Moreover, ion doping is of great significance to the further study of low leakage resistance and good anti-fatigue properties for KNN-based ferroelectric materials.

Energy storage and thermodynamics of PNZST thick films with coexisting antiferroelectric and ferroelectric phases

AbstractPb0.99Nb0.02(Zr0.85Sn0.13Ti0.02)O3 (PNZST) antiferroelectric (AFE) thick films are successfully deposited on silicon‐based Pt and LaNiO3 electrodes by a sol‐gel method. The coexistence of ferroelectric (FE) and AFE phases are revealed in PNZST films by XRD, electric‐induced hysteresis loops, dielectric, and leakage current properties. Comparing with PNZST/Pt film, larger recoverable energy density and efficiency are obtained in PNZST/LaNiO3 film due to the lower FE phase proportion. It is analyzed and demonstrated by a thermodynamic model of AFE and FE coexistence system. In addition, the fatigue behaviors of both AFE films are also affected by the proportion of the coexisting FE phase. PNZST/LaNiO3 film exhibits good fatigue resistance on energy storage even after 1010 switching cycles, which is attractive to pulsed power applications.

Composition-dependent structural, electrical, magnetic and magnetoelectric properties of (1 − x)BaTiO3−xCoFe2O4 particulate composites

Multiferroic composite with the general formula (1 − x)BaTiO3−xCoFe2O4 (x = 0.05, 0.15, 0.25, 0.35 and 0.45) has been synthesized by a standard solid-state reaction route. Powder X-ray diffraction analysis confirms the existence of ferrite (spinel CoFe2O4) and ferroelectric (tetragonal BaTiO3) biphase without any impurity phases in the sintered composites. Microstructure of the composite displays two different grain sizes and shapes studied from SEM analysis. The composites show both ferroelectric and ferromagnetic ordering: the saturation magnetization (Ms) and retentivity (Mr) of the composite are improved with the increase in ferrite phase, while leakage current, ferroelectric and dielectric properties of the composites show a drop. Existence of coupling between ferroelectric and ferromagnetic ordering measured through magnetodielectric (MD) and magnetoelectric (ME) studies reveal an increase in % MD and ME coefficients with an increase in ferrite content. An enhanced ME coupling coefficient of 17 mV cm−1 Oe−1 has been realized at a dc magnetic field of 5 kOe with a ac frequency of 50 Hz in (1 − x)BaTiO3−xCoFe2O4 (x = 0.45) composite.

Hollow polymeric microsphere-filled silicone-modified epoxy as an internally insulated material for composite cross-arm applications

Composite cross-arms have been developed to take place of the steel cross-arm in the power system. In order to suit the environmental impact factors in the long-term operation, superior comprehensive properties of the internally insulated materials for composite cross-arm are required. In the present study, a syntactic foam based on hollow polymer microsphere (HPM)-filled siliconized epoxy resin (SER) was prepared for satisfying these requirements. First, the SER was synthesized using poly (methylphenylsiloxane) and an epoxy resin via a graft reaction. The as-synthesized SER was characterized via Fourier transform infrared, 1H nuclear magnetic resonance (NMR), and 13C NMR spectroscopies. Subsequently, a series of SER-based syntactic foams were fabricated using HPM with five different mass fractions. According to the thermogravimetric analysis results, the thermal stability of the composites considerably improved because of the introduction of the siloxane bond. The dielectric constant and dielectric loss of the composites simultaneously decreased with increasing HPM content. The dielectric strength of the composites remained 10.08–21.31 kV/mm after hydrothermal treatment, indicating excellent electrical insulation reliability. Notably, after water diffusion pre-stressing, the leakage current properties of the composites only slightly differed as the HPM content increased. These results further support their application as an internally insulated material for a composite cross-arm.

Microstructure and Electrical Properties of Low-temperature Solution-processed Sol-gel KNN Thin Films

We report on an environmentally friendly and versatile chemical solution deposition route to K0.5Na0.5NbO3 (KNN) thin films. The excess amounts of K and Na in KNN precursor solutions was found to be strong influence on perovskite KNN single-phase thin films. It was revealed from Raman spectroscopic analysis data that a change in scattering mode was observed for the KNN thin films fabricated under various processing conditions. This change was due to the chemical composition fluctuation of K and Na in the KNN thin films during heat treatment. The leakage current and ferroelectric properties of the thin films were strongly affected by the excess amounts of K and Na as well. KNN thin films with 20 mol% excess K and Na exhibited a leaky ferroelectric polarization–electric field (P–E) hysteresis. Leakage current density of the film was 3.85´10-8 A/cm2 at applied field of -60 kV/cm.

Ferroelectric and Electrical Properties Optimization of Mg-doped BiFeO3 Flexible Multiferroic Films

Bi1-xMgxFeO3 (BMFO, x = 0, 0.02, 0.04, 0.06 and 0.08) multiferroic films were directly synthesized on flexible stainless steel (FSS), save the bottom electrode process, by means of sol–gel spin-coating technology. The effects of different bending conditions on ferroelectric, dielectric and leakage-current properties of BMFO films were investigated. The leakage-current densities of BiFeO3 (BFO, x = 0) and BMFO (x = 0.06) films were 5.86 × 10−4 and 3.73 × 10−7 A/cm2, which shows that the BMFO (x = 0.06) has more than three orders of magnitude lower than that of BFO film. The residual polarization (2 Pr) can be enhanced from 120 to 140 μC/cm2. The proper doping of Mg in BiFeO3 film could provide an effective method for reducing the leakage-current values as well as boosting the ferroelectric properties. In this study, the leakage-current mechanism of low electric field and high electric field of BMFO film is analyzed and established. In addition, the flexible BMFO film maintains practical ferroelectric and leakage-current properties at retention time of 106 s under different symmetry bending conditions. These results indicate that the BFMO film will be very practical in opto-electronic and storage device applications.