Showing papers on "Insulator (electricity) published in 2005"

Coaxial cable-connector termination

Abstract: A high frequency coaxial cable having a foil ( 7 a ) between the cable insulator ( 5 ) and cable braid ( 7 b ), is terminated to a coaxial connector ( 40 ) in a manner that allows fast and easy cable preparation and results in a termination with minimal axial electric field lines that cause a high insertion loss and a high VSWR (voltage standing wave ratio). A bore ( 46 ) at the rear portion of the connector outer conductor, receives the cable insulator with foil around the cable insulator. The bore has a front part ( 54 ) that forms an interference fit around the foil, to avoid an axially-extending gap which might contain axially-extending field lines. The front of cable insulator and foil are flush and both abut the insulation ( 25 ) of the connector.

Ground-state decay rate for the Zener breakdown in band and Mott insulators

Abstract: Nonlinear transport of electrons in strong electric fields, as typified by dielectric breakdown, is reformulated in terms of the ground-state decay rate originally studied by Schwinger in nonlinear QED. We discuss the effect of electron interaction on Zener tunneling by comparing the dielectric breakdown of the band insulator and the Mott insulator, where the latter is studied by the time-dependent density-matrix renormalization group. The relation with the Berry's phase theory of polarization is also established.

Electric Field Effect in Diluted Magnetic Insulator Anatase Co: TiO~2

Abstract: An external electric field induced reversible modulation of a room temperature magnetic moment and coercive field is achieved in an epitaxial and insulating thin film of dilutely cobalt-doped anatase TiO 2 . This first demonstration of an electric field effect in any oxide-based diluted ferromagnet is realized in a high quality epitaxial heterostructure of PbZr 0.2 Ti 0.8 O 3 /Co: TiO 2 /SrRuO 3 grown on (001) LaAlO 3 . The observed effect, which is about 15% in strength in a given heterostructure, can be modulated over several cycles. Possible mechanisms for electric field induced modulation of insulating ferromagnetism are discussed.

Integrated antenna type circuit apparatus

Abstract: An integrated antenna type circuit apparatus which provides excellent circuit characteristics while suppressing an increase in packaging area. The integrated antenna type circuit apparatus includes an insulating base, a semiconductor circuit device, chip parts, a molding resin, an antenna conductor, a ground conductor, and external lead electrodes. The plurality of chip parts are mounted on the insulating base, and are soldered to electrodes of wiring conductors on the top of the insulating base for electric and physical connection. The insulating base has a multilayer structure, being formed by laminating a plurality of insulator layers. The antenna conductor is formed on the bottom of the insulating base. A wiring conductor adjacent to the antenna conductor is provided with the ground conductor so that it overlaps with the antenna conductor.

Design optimization of high breakdown voltage AlGaN-GaN power HEMT on an insulating substrate for R/sub ON/A-V/sub B/ tradeoff characteristics

Abstract: High breakdown voltage AlGaN-GaN power high-electron mobility transistors (HEMTs) on an insulating substrate were designed for the power electronics application. The field plate structure was employed for high breakdown voltage. The field plate length, the insulator thickness and AlGaN layer doping concentration were design parameters for the breakdown voltage. The optimization of the contact length and contact resistivity reduction were effective to reduce the specific on-resistance. The tradeoff characteristics between the on-resistance and the breakdown voltage can be improved by the optimization of the above design parameters, and the on-resistance can be estimated to be about 0.6 m/spl Omega//spl middot/cm/sup 2/ for the breakdown voltage of 600 V. This on-resistance is almost the same as that for the device on a conductive substrate.

The influence of the insulator surface properties on the hydrogen response of field-effect gas sensors

Abstract: The hydrogen response of gas-sensitive field-effect devices is mainly due to trapping of atomic hydrogen on the insulator side of the metal-insulator interface of the metal-insulator-semiconductor (MIS) structure. Therefore an influence of the choice of insulator on the hydrogen response properties is expected. We have investigated this influence by producing MIS capacitors with four different insulators; SiO2, Al2O3, Si3N4, and Ta2O5. The results show that the choice of insulator influences the detection limit, the saturation concentration, and the saturation response. Furthermore, there is a strong correlation between the observed saturation response and the oxygen concentration of the insulator surface, as measured by Auger electron spectroscopy, which indicates that the trapping of hydrogen at the interface occurs at the oxygen atoms of the insulator surface. Finally, if the metal film is porous a catalytic oxidation of the insulator surface appears to be facilitated, which can increase the hydrogen r...

Conductive lines buried in insulating areas

Abstract: An integrated circuit comprising a semiconductor substrate in which active areas surround or are surrounded by hollowings filled with an insulator, and in which a conductive region is embedded in the insulator of at least one hollowing, the conductive region being connected to a reference voltage and being connected at least one neighboring element of the circuit.

Quantification of corona discharges on nonceramic insulators

Abstract: This paper attempts to establish a correlation of the visual images of corona obtained from a camera with discharge magnitude measured with conventional partial discharge equipment. A linear relationship is shown between the transformed image parameters and the discharge magnitude, thereby providing a means for quantifying corona observations made during routine maintenance inspections, of insulators from ground. Different insulator designs using silicone rubber (SIR) and ethylene propylene diene monomer (EPDM) housings were examined. The effect of fog has been examined by performing experiments inside a fog chamber. It is shown that this information can be used along with the corona degradation characteristics of housing materials to identify discharge patterns that can pose problems to the integrity of the insulator.

Yttria insulator ring for use inside a plasma chamber

Abstract: A yttria insulator ring for use in a plasma processing apparatus is provided to minimize arcing between the apparatus and a ground extension, while also increasing a mean time between cleanings (MTBC). The yttria insulator ring may be located between a ground extension and a plasma generation zone, or gap, of the chamber of the apparatus, as well as between an edge ring and the ground extension. Compared to a quartz ring, the yttria insulator ring can also provide improved semiconductor substrate uniformity because of improved RF coupling as a result of decreased reactivity and increased dielectric constant.

Three-dimensional modeling of potential and electric-field distributions along an EHV ceramic post insulator covered with ice - Part I: Simulations of a melting period

Abstract: The main objective of this paper is to determine the potential and electric-field distributions along a typical ceramic extremely-high-voltage post insulator covered with atmospheric ice during a melting period. Commercial software, Coulomb 3D, based on the boundary element method (BEM), was used for all of the three-dimensional modeling and simulations. It was demonstrated that the BEM is well suited for evaluating the effect of ice shedding on the potential and electric-field distributions along an ice-covered insulator during a melting period. The results obtained show that the length and number of ice free zones, also called air gaps, are the major parameters that affect the applied voltage distribution along an ice-covered insulator. The mean electric field per arcing distance, affected mainly by the air-gap lengths, can provide a good indication of the presence of partial arcing along the different air gaps.

Computer modeling of interaction of gas discharge plasma with solid dielectric barriers

Abstract: A computer model describing charge transfer in a system consisting of two parallel-plate metallic electrodes covered with solid dielectric barriers immersed in gas medium is proposed. The material of the barriers is supposed to be a non-ideal insulator whose properties correspond to polyethylene and air is considered as a gas phase. The model is based on continuity equations for fluxes of charge carriers and accounts for their drift and diffusion and also for different sources of their generation and losses in different media. The continuity equations are coupled with Poisson's equation for computing electric fields affected by temporal and spatial variations of space charges in the system. Results of the computer simulations are obtained for the case when the applied field in the gas exceeds its breakdown threshold, i.e. charge transfer in the gas phase takes place in the form of an electrical discharge (electron avalanche and streamer). Evolution of generated discharge plasma is analyzed taking into account conditions on gas-solid interfaces and in the bulk of the solid dielectric barriers.

Electric field analysis of water drop corona

Abstract: Water drops on surface of polymer insulation materials may cause corona because they can enhance the electric field nearby. Water drop corona plays an important negative role in the long-term performance of composite insulators. In this paper, based on a model with two parallel electrodes water drop corona is studied. The relationship between initial corona voltage and different sets of water drops is obtained from experiments. Then several factors, which may affect the electric field analysis of water drop corona, are studied by numerical calculation on computer. Calculation is mainly on a 2-D model. However, a 3-D model is also used to study the effect of water drops distributed in space.

Effect of insulator shape on surface discharges and flashover under polluted conditions

Abstract: Despite the extensive investigations carried out on the pollution performance of outdoor insulators, the flashover characteristic and its interaction with insulator shape is still not very well understood. In this paper, we present findings of experiments which allow quantifying the effects of insulator geometry on the flashover voltage. Two main parameters were considered: the flashover current (maximum magnitude of leakage current just before flashover) and the flashover voltage. Known difficulties related to accurate measurement of these parameters which are due to parallel partial arcs on some insulators, have been quantified using control insulators and simple modelling approaches. Furthermore, the effect of insulator shape on arc length has been quantified using nonuniform pollution techniques.

Piezoresistance behavior of silicone–graphite composites in the proximity of the electric percolation threshold

Abstract: Composites of a silicone matrix charged with graphite powder of micrometric size in volume fractions around the electric percolation threshold (25–35%) have been investigated with regard to their piezoresistance properties. The elastic modulus changes with graphite content, reaching a maximum at 30 vol.%. From measurements of electric resistivity, the percolation threshold was determined as 31 vol.% at a compressive strain of 2%. The threshold value was found to be dependent on the applied compressive strain so that an insulator in the unstrained condition may become a conductor when subjected to a small pressure. The property can be exploited for contact sensors. Further, the electric resistance of a composite, charged a little beyond the percolation threshold, is also strain dependent, according to an equation of the type R = R0exp(βɛ), where β was found to be about 51.5. This value of β corresponds to a very high electric sensitivity of the material to an applied strain and makes it a candidate for application as a logarithmic strain transducer. Owing to the visco-elastic behavior of the elastomer matrix, there is a retardation of the electric response on unloading of about 2 s. The electric response to an applied stress follows an exponential law on loading and undergoes a corresponding retardation on unloading.

Insulator coating and method for forming same

Abstract: The present invention is a method of applying Lotus Effect materials as a (superhydrophobicity) protective coating for external electrical insulation system applications, as well as the method of fabricating/preparing Lotus Effect coatings. Selected inorganic or polymeric materials are applied on the insulating material surface, and stable superhydrophobic coatings can be fabricated. Various UV stabilizers and UV absorbers can be incorporated into the coating system to enhance the coating's UV stability.

Atomic-layer-deposited Al2O3–HfO2–Al2O3 dielectrics for metal-insulator-metal capacitor applications

Abstract: Atomic-layer-deposited Al2O3–HfO2–Al2O3 dielectrics have been investigated to replace conventional silicon oxide and nitride for radio frequency and analog metal-insulator-metal capacitors applications. In the case of 1‐nm‐Al2O3, sufficiently good electrical performances are achieved, including a high dielectric constant of ∼17, a small dissipation factor of 0.018 at 100kHz, an extremely low leakage current of 7.8×10−9A∕cm2 at 1MV∕cm and 125°C, perfect voltage coefficients of capacitance (74ppm∕V2 and 10ppm∕V). The quadratic voltage coefficient of capacitance decreases with the applied frequency due to the change of relaxation time with different carrier mobility in insulator, and correlates with the dielectric composition and thickness, which is of intrinsic property owing to electric field polarization. Furthermore, the conduction mechanism of the AHA dielectrics is also discussed, indicating the Schottky emission dominated at room temperature.

Three-dimensional modeling of potential and electric-field distributions along an EHV ceramic post insulator covered with ice-Part II: effect of air gaps and partial arcs

Abstract: The main objective of this paper is to investigate the effect of air-gap position, length, and number on the phenomena preceding flashover along a typical 735-kV porcelain station post insulator unit under heavy ice accretion. Under these conditions, this type of insulator seems to be the most likely subject to flashover. The numerical simulations were performed using Coulomb 3D, a commercial software based on the boundary element method (BEM). Computer simulations were performed during a melting period. Special attention was paid to the presence of a conductive water film at the ice surface and to a partial arc along an air gap. The results obtained showed that the number of air gaps, with or without the presence of a partial arc along them, has a direct effect on the distribution of potential along the iced insulator. Moreover, for the same total arcing distance, the number of air gaps and their position did not affect the average electric field per arcing distance that was used to determine the partial arc presence. Based on these results, suggestions for improving station insulator geometry for icing conditions were proposed.

Electrical tracking performance of LLDPE-natural rubber blends by employing combination of leakage current level and rate of carbon track propagation

Abstract: Electrical tracking develops from surface discharge activity associated with the flow of leakage current on insulator surface under wet and contaminated conditions. Arcs created from this surface discharge phenomenon burn the polymer insulator material and create carbonized tracks in the long run. This paper reports on electrical tracking performance through the observation of leakage current and carbon track development of blends of linear low-density polyethylene with natural rubber (LLDPE/NR) either filled with or without alumina trihydrate. An electrical tracking and erosion test using the inclined-plane tracking method is conducted to study the overall performance of surface tracking properties. The combined effect of leakage current level and carbon track propagation rate is used as a new technique for describing the level of electrical tracking performance based on the proposed normalized degradation index. Morphological analysis is also carried out to investigate the surface microstructure before and after the tracking test. The experimental results show that different material compositions affect the leakage current and carbon track development. In addition, the calculated normalized degradation index has shown some correlation with the degree of surface deterioration.

Field emission at 10Vcm−1 with surface emission cathodes on negative-electron-affinity insulators

Abstract: Surface emission cathodes reported here consist of two electrodes separated by ∼10μm on a negative-electron-affinity glass, Cs2Si4O9. The electrodes consist of a W film suspended over the insulator by a gap of 0–70 nm. When electron emission is initiated with a bias of 0–300 V, between the electrodes, the cathodes continue to emit after the bias is removed and for anode voltages as low as 20 V, electric fields <10Vcm−1. The emission is modeled by the electrons tunneling from the electrode onto the glass surface and from there they are emitted into vacuum. Emission without bias is the result of positive charge in the insulator, which replaces the need for a bias voltage.

Nonvolatile memory using Al2O3 film with an embedded Al-rich layer

Abstract: This letter describes the capacitance-voltage (C-V) characteristics of a new nonvolatile Al2O3 memory with nanoscale thin film deposited by electron-cyclotron-resonance sputtering. Al-rich Al2O3 was fabricated at a reduced oxygen gas flow rate and used as a charge storage layer of the Al2O3 memory, which is located between the tunnel insulator and blocking insulator. C-V characteristics show a large hysteresis window due to the Al-rich structure, but there is no hysteresis window in the case of stoichiometric Al2O3 structure. This memory will stay nonvolatile for several years or more. The number of electrons injected into the insulator in the case of nanoscale memory cell length is discussed. A discussion of the statistical Gaussian distribution indicates that about 50 localization sites are necessary in Al2O3 memory with 10nm cell length for realizing a 1.8V change of the threshold voltage, which corresponds to the control of ten electrons in the insulator. This structure is easily achieved by the propo...

An investigation of moisture and leakage currents in GRP composite hollow cylinders

Abstract: The applicability of using flat composite plates and hollow core composite cylinders for moisture absorption testing of unidirectional glass/polymer composites used in high voltage composite (non-ceramic) insulators was examined. Two main issues were addressed in this work. First, the effect of specimen geometry (cylinders vs. plates) on moisture absorption by the composites was investigated both numerically and experimentally. Both classical Fickian and non-Fickian diffusions were considered. Subsequently, hollow core cylinders made up of ECR (low seed)-glass fibers and epoxy resin were tested for their high voltage properties under controlled moisture diffusion conditions. The specimens were exposed to warm, moist air and their high voltage properties were ascertained using a modified version of the ANSI test (standard C29.11 Section 7.4.2) for water diffusion electrical testing. It was found that the behavior of the hollow core cylinder and flat plate composite specimens subjected to moisture compared reasonably well experimentally and very well numerically. From the high voltage tests, a direct correlation was found between the amount of moisture that had been absorbed by the specimens and the amount of leakage current that was detected. It was shown that using the thin walled composite cylinders leakage currents could be predicted based on the amount of absorbed moisture in the insulator composites. The predictions can be made based on relatively short term moisture data even if the diffusion process in the composites is anomalous in nature with long times required for full saturation. After additional verifications, considering other composite systems, the hollow core cylinder testing under controlled moisture and high voltage conditions could become a screening test for selecting suitable glass/polymer composites for insulator applications.

MgO insulating films prepared by sol–gel route for SiC substrate

Abstract: Silicon carbide (SiC) is a wide bandgap semiconductor suitable for high-voltage, high-power, and high-temperature devices from dc to microwave frequencies. However, the commercialization of advanced SiC power devices remains limited due to performance limitation of the SiO2 dielectric among other issues. Indeed, SiO2 has a dielectric constant 2.5 times lower than that of SiC, which means that at critical field for breakdown in SiC, the electric field in the adjoining SiO2 becomes too high for reliable operation. This removes the main advantage of using SiC power devices if the ten times higher breakdown field for SiC in comparison to Si cannot be exploited. Therefore, alternative dielectrics having a dielectric constant higher than or of the same order as that of SiC (ɛr ≈ 10) should be used to reduce the electrical field in the insulator. Among alternative dielectrics to silicon dioxide (SiO2), magnesium oxide (MgO) seems to be a good candidate regarding its bulk properties: large bandgap, high thermal conductivity and stability, and a suitable dielectric constant (ɛr ≈ 10). In order to evaluate such promising candidate, the sol–gel process appears to be a convenient route to elaborate this kind of coatings. By selecting appropriate precursor solution and optimizing the curing conditions of the films, MgO films could be obtained under various crystallization states: non-oriented and preferred 〈1 1 1〉 orientation. MIM structures have been used to investigate the insulating potentialities of the sol–gel MgO films. The dielectric strength of the films was found to be microstructure dependent, and reached 5–8 MV/cm at room temperature. Leakage currents were measured from 25 °C up to 250 °C.

Intense electron beam propagation through insulators: Ionization front structure and stability

Abstract: The structure and stability of the ionization front, which occurs as a high intensity electron beam propagates through an insulator, are considered. It is found that, due to the electric field ionization, the velocity of the front, Vf, has a nonmonotonic dependence on the beam density, nb, and in some particular beam density range Vf increases with increasing nb. Two instabilities of the ionization front associated with the electric field ionization process of the insulator are found: a long wavelength (⪞fewμ) and relatively slow (∼1013s−1) corrugation instability and a short wavelength (∼subμ) and relatively fast (∼few×1013s−1) electric field ionization instability.

Dual damascene with via liner

Abstract: A dual damascene structure with improved profiles and reduced defects and method of forming the same, the method including forming a first dielectric over a conductive area; forming a first dielectric insulator over the first dielectric; forming a first opening in the first dielectric insulator; lining the opening with a second dielectric; forming a second dielectric insulator over the first dielectric insulator; forming a second opening in the second dielectric insulator overlying and communicating with the first opening; and, filling the first and second openings with a conductive material to electrically communicate with the conductive area.