Showing papers on "Insulator (electricity) published in 2003"

Low-k Insulators as the Choice of Dielectrics in Organic Field-Effect Transistors

Abstract: In this paper, we present a new effect influencing the operation of organic field-effect transistors resulting from the choice of gate insulator material. In a series of studies it was found that the interaction between the insulator and the semiconductor materials plays an important role in carrier transport. The insulator is not only capable of affecting the morphology of the semiconductor layer, but can also change the density of states by local polarization effects. Carrier localization is enhanced by insulators with large permittivities, due to the random dipole field present at the interface. We have investigated this effect on a number of disordered organic semiconductor materials, and show here that significant benefits are achievable by the use of low-k dielectrics as opposed to the existing trend of increasing the permittivity for low operational voltage. We also discuss fundamental differences in the case of field-effect transistors with band-like semiconductors.

High resolution measurements of surface charge densities on insulator surfaces

Abstract: The uses and limitations of the electrostatic probe for the measurement of charge densities on insulating surfaces are discussed. A development of the technique is described in which two important limitations have together been overcome: (i) The effects on the probe signal of charges on all points of the surface have been taken into account by means of a matrix inversion procedure; (ii) A robotic control system has been developed which enables the probe to follow and scan a wide range of axi-symmetric insulator profiles. The degree of resolution achieved enables the probe system to display and measure charge densities in individual streamer channels of a corona discharge on a polytetrafluoroethylene (PTFE) surface. An example is given and comparison made with a dust figure of the same event.

HfO2-based insulating stacks on 4H–SiC(0001)

Abstract: Depositing HfO2 layers on ultrathin thermally grown SiO2 on 4H–SiC(0001) is demonstrated to yield an insulator with good properties. The stack combines the high quality of the ultrathin SiO2/SiC interface and associated high energy barriers for electron and hole injection from SiC with the high dielectric permittivity of HfO2 (≈20). The latter allows application of high electric fields to the SiC surface (up to 3 MV/cm), while keeping the strength of the field in the insulator at a moderate level.

Organic Thin-Film Transistors on a Plastic Substrate with Anodically Oxidized High-Dielectric-Constant Insulators

Abstract: Organic thin-film transistors (OTFTs) which use Ta2O5 as the gate insulators were fabricated on plastic substrates. The gate insulators were synthesized by anodizing the gate electrodes fabricated as stacked structures of aluminum (Al) and tantalum (Ta) at room temperature. The stacked structure suppressed the stress at the interface between the substrate and metal electrodes so that cracks on Ta could be avoided. The organic semiconductor pentacene was used as the active layer on the gate insulator. The OTFTs showed the best performance at an operating voltage of 5 V and a good field-effect mobility of 0.36 cm2/Vs on plastic substrates. The structural order of the pentacene in the film and the temperature dependence of the leakage current in the insulator were also studied to improve the device characteristics.

Impact of corona on the long-term performance of nonceramic insulators

Abstract: A majority of nonceramic insulator (NCI) application is under relatively clean conditions where leakage current may be nonexistent. Occurrence of corona for long periods of time on NCI operating under relatively clean conditions is possible due to localized high electric field (E-field) brought about by design and manufacturing deficiencies. Therefore, resistance to corona-induced degradation of NCI housing materials is an important factor that impacts NCI long-term reliability, and is the focal point of this paper. Two sources of corona have been investigated: corona from a metal electrode, and corona from water droplets. Field inspections were performed on 230 and 500 kV insulators to demonstrate the existence of corona even under relatively clean and dry conditions. Three commonly used NCI housing materials, namely high temperature vulcanized (HTV) silicone rubber (SIR), ethylene propylene diene monomer (EPDM) and a blend of EPDM and silicone polymer were evaluated in the laboratory. In addition, housing materials from several insulators removed from the field were analyzed. Data gathered from electrical and physicochemical analyses show that corona induced degradation is dominantly due to a combination of electro-chemical reactions rather than thermal effects.

Composite structures, such as coated wiring assemblies, having integral fiber optic-based condition detectors and systems which employ the same

Abstract: Integral fiber optic-based condition sensors detect conditions of a composite structure, e.g., a coated wire assembly so as to detect damage or conditions that may damage the same. Preferably, at least one optical fiber sensor having a plurality of Bragg gratings written into the fiber at spaced-apart locations along its axial length is integrated into the electrical insulator coating of a wire, wire bundle or wiring harness. The fiber optic sensor may thus be employed to measure the environmental loads on the electrical wiring including stresses from bending, axial loading, pinch points, high temperature excursions and chemical damage. The system is capable of detecting and locating transient conditions that might cause damage to a wiring system or permanent changes in state associated with damage events. The residual stress in the electrical insulator coating of a wire, wire bundle, or wiring harness are used to monitor the evolution of damage by wear or chaffing processes. Detected stress relief on one or more Bragg gratings will thus be indicative of damage to the insulator coating on the conductor. As such, the magnitude of such stress relief may be detected and used as an alert that the wire insulation is damaged to an unsafe extent.

Mold growth on nonceramic insulators and its impact on electrical performance

Abstract: This paper describes the identification of a common mold (i.e., fungus) growing on nonceramic insulators (NCIs) in service, and analyzes its impact on the electrical performance. The insulators evaluated were line posts removed from a 138-kV transmission line serving the interior (away from the coast) regions in Florida. The insulators had housings made from different types of silicone rubber (SR) and ethylene propylene rubber (EPR) polymer families. Electrical tests performed include surface resistance measurements and determination of contamination withstand capability (CWC) using the clean-fog procedure. Changes in the CWC were correlated to material changes by using micro-Fourier transform infrared (FTIR) analysis and surface resistance measurements. It was concluded that the mold growth is dependent on material formulation and outdoor environment. On SR insulators that exhibited mold growth, there was a reduction in the CWC when compared to the same insulator without the mold; however, even the reduced level of CWC was superior to that obtained on similarly rated EPR and porcelain insulators without any visible mold growth. Lastly, simple methods to remove the mold from the insulators are listed.

Silicon-on-insulator structures and methods

Abstract: Silicon-on-insulator (SOI) structures are provided by forming a single-crystal insulator over a substrate, followed by heteroepitaxy of a semiconductor layer thereover. Atomic layer deposition (ALD) is preferably used to form an amorphous insulator, followed by solid phase epitaxy to convert the layer into a single-crystal structure. Advantageously, the crystalline insulator has a lattice structure and lattice constant closely matching that of the semiconductor formed over it, and a ternary insulating material facilitates matching properties of the layers. Strained silicon can be formed without need for a buffer layer. An amorphous SiO2 layer can optionally be grown underneath the insulator. In addition, a buffer layer can be grown, either between the substrate and the insulator or between the insulator and the semiconductor layer, to produce desired strain in the active semiconductor layer.

Corona propagation and charge deposition on a PTFE surface

Abstract: A description is given of some properties of the corona discharge when propagating over a cylindrical polytetrafluoroethylene insulator surface placed along the axis of a rod-plane electrode arrangement. A scanning electrostatic probe has been used to measure the density of charge deposited on the surface; it is shown that the total net deposited charge is small compared with the total charge injected into the gap. The velocity of propagation has been measured. Effects of preceding coronas on succeeding ones and the nature of deposited charge after breakdown are described. Discussion is given in terms of electron lifetimes and attachment and photoemission processes.

Simulation of voltage distribution calculation methods over a string of suspension insulators

Abstract: Insulators for overhead lines are considered to be of basic importance to the transmission system, through their ability to insulate the power lines as well as their function in carrying the weight of the line conductor. For higher voltages, a string of suspension insulators is used. The number of insulator units used depends on the voltages of the lines. The voltage is not equally shared between the units in a suspension insulator string. The capacitances between each cap/pin junction and the tower and between the cap and pin of each unit determine the voltage distribution. Calculation of the voltage distribution can be made by different methods. In this study, these calculation methods and a formulation for each method are studied theoretically through computer programs in case of clean-dry condition. String efficiency comparison for each method is presented, and studying the equalizing voltage drops across insulators is also covered.

Apparatus and method for shaping high voltage potentials on an insulator

Abstract: An apparatus and method for reducing the incidence of electric field stress on portions of insulating structures within high voltage devices is disclosed. Each of the embodiments disclosed herein modifies the conductive properties of the insulating structure surface in a non-uniform manner such that the distribution of voltage potential along the surface thereof is more fully equalized during operation of the high voltage device. This, in turn, reduces the per unit stress on the insulating structure caused by the electric field of the high voltage device. Through embodiments of the present invention are preferably directed to utilization in x-ray tube devices, a variety of high voltage devices may benefit from application of the disclosed matter.

Metal-enclosed switchgear

Abstract: A tank filled with an insulating gas accommodates insulator tubes incorporating vacuum-valve breakers for individual phases One end of each insulator tube is fixed to the inside of the tank Each vacuum-valve breaker is installed generally on a common longitudinal axis with the relevant insulator tube in such a manner that its movable electrode rod is directed toward the fixed end of the insulator tube The insulator tube has as its integral part a bus line fixing portion projecting in a direction intersecting the longitudinal axis of the insulator tube from the proximity of its end opposite to the fixed end to support a bus-side conductor in an insulated fashion

Vacuum heat insulator, hot insulating device using vacuum heat insulator, and electric water heater

Abstract: In this vacuum heat insulator, an excellent heat insulating performance is obtained even at high temperature, and this excellent heat insulating performance is maintained for a long period. The hot insulating device and electric water heater using this vacuum heat insulator exhibit an excellent hot insulating performance, and are decreased in the power consumption for hot insulation. The vacuum heat insulator includes a laminate bag, and an insulating core placed in the laminate bag, and the inside of the laminate bag is evacuated in a vacuum state. The laminate bag is made of a laminate film. The laminate film includes a support layer, a deposition layer evaporated on the surface of the support layer, a protective layer placed at the surface side of the deposition layer, and a seal layer placed at the back side of the deposition layer. The deposition layer is formed of at least one material of metal and metal oxide. In this laminate film, (i) the support layer has a plastic film having a glass transition point of 87° C. or higher, (ii) the protective layer has a plastic film having a glass transition point of 87° C. or higher, (iii) the deposition layer has a property of transmitting high frequency magnetic field, or (iv) the laminate bag has a seal portion formed by junction of the seal layer, and the laminate film further as a metal foil placed at a position excluding the seal portion.

Characterization of the metal–insulator interface of field-effect chemical sensors

Abstract: The metal-insulator interface of hydrogen-sensitive metal-insulator-semiconductor capacitors, with SiO2 as the insulator and Pt as the metal contact, was discussed. It was found that the difference ...

Spark plug for motor vehicles thermal engine, has anode disposed in central position and insulated from cathode by insulator, where insulator and end of cathode are separated by space

Abstract: The plug has a cathode (103) screwed in a recess formed in a cylinder head of an internal combustion engine and opening into the interior of a combustion chamber. An anode (106) is disposed in a central position and insulated from the cathode by an insulator (100). The insulator and an end of the cathode are separated by a space, where the insulator is made of material having relative permittivity greater than 3. An independent claim is also included for a plasma generation system comprising a spark plug.

Electrostatic precipitator with internal power supply

Abstract: An electrostatic precipitator, including for a diesel engine electrostatic crankcase ventilation system for blowby gas, includes a corona discharge electrode assembly in a housing, an insulator extending along an internal surface of a wall of the housing, a power supply in the housing on the opposite side of the insulator from the housing wall such that the insulator is between the housing wall and the power supply, and a low voltage lead extending through the housing wall and through the insulator to the power supply, eliminating pass-through of a high voltage lead through the housing wall and through the insulator. The power supply is preferably provided in the hollow interior of the corona discharge electrode assembly.

System and method to delay closure of a normally closed electrical circuit

Abstract: A system and method are provided to delay closure of an electrical circuit of a battery-powered electrical device, intended to operate remotely in an environment in which the pH value changes from one value to another. Two electrical contacts of an electrical circuit are separated by an insulator that holds the circuit open until the device is exposed to an environment having a predetermined pH value. Exposure of the insulator to an environment having that pH value causes the insulator to dissolve and the circuit to close, energizing the device. Alternatively, A Hall effect transistor or a reed switch may be used as the switch. It is held open by the presence of a magnetic field held in place by material that is dissolvable at a predetermined pH level. When a region having that pH level is reached, the material dissolves and the circuit closes.

Method for fabricating semiconductor devices

Abstract: According to the present invention, an oxide film with the film quality almost equivalent to that of the thermal oxide can be formed by the low-temperature treatment. After removing an insulator on the active region of the substrate which constitutes a semiconductor wafer, an insulator made of, for example, silicon oxide is deposited on the main surface of the semiconductor wafer by the low pressure CVD method. This insulator is a film to form a gate insulator of MISFET in a later step. Subsequently, a plasma treatment is performed in an atmosphere containing oxygen (oxygen plasma treatment) to the insulator in the manner as schematically shown by the arrows. By so doing, the film quality of the insulator formed by the CVD method can be improved to the extent almost equivalent to that of the insulator formed of the thermal oxide.

Electron Emission Properties of Insulator Materials Pertinent to the International Space Station

Abstract: We present the results of our measurements of the electron emission properties of selected insulating and conducting materials used on the International Space Station (ISS) Utah State University (USU) has performed measurements of the electron-, ion-, and photon-induced electron emission properties of conductors for a few years, and has recently extended our capabilities to measure electron yields of insulators, allowing us to significantly expand current spacecraft material charging databases These ISS materials data are used here to illustrate our various insulator measurement techniques that include: i) Studies of electron-induced secondary and backscattered electron yield curves using pulsed, low current electron beams to minimize deleterious affects of insulator charging ii) Comparison of several methods used to determine the insulator 1st and 2nd crossover energies These incident electron energies induce unity total yield at the transition between yields greater than and less than one with either negative or positive charging, respectively The crossover energies are very important in determining both the polarity and magnitude of spacecraft surface potentials iii) Evolution of electron emission energy spectra as a function of insulator charging used to determine the surface potential of insulators iv) Surface potential evolution as a function of pulsed-electron fluence to determine how quickly insulators charge, and how this can affect subsequent electron yields v) Critical incident electron energies resulting in electrical breakdown of insulator materials and the effect of breakdown on subsequent emission, charging and conduction vi) Charge-neutralization techniques such as low-energy electron flooding and UV light irradiation to dissipate both positive and negative surface potentials during yield measurements Specific ISS materials being tested at USU include chromic and sulfuric anodized aluminum, RTV-silicone solar array adhesives, solar cell cover glasses, Kapton, and gold Further details of the USU testing facilities, the instrumentation used for insulator measurements, and the NASA/SEE Charge Collector materials database are provided in other Spacecraft Charging Conference presentations (Dennison, 2003b) The work presented was supported in part by the NASA Space Environments and Effects (SEE) Program, the Boeing Corporation, and a NASA Graduate Fellowship Samples were supplied by Boeing, the Environmental Effects Group at Marshall Space Flight Center, and Sheldahl, Inc

Comparison of Classical and Charge Storage Methods for Determining Conductivity of Thin Film Insulators

Abstract: Conductivity of insulating materials is a key parameter to determine how accumulated charge will distribute across the spacecraft and how rapidly charge imbalance will dissipate. Classical ASTM and IEC methods to measure thin film insulator conductivity apply a constant voltage to two electrodes around the sample and measure the resulting current for tens of minutes. However, conductivity is more appropriately measured for spacecraft charging applications as the "decay" of charge deposited on the surface of an insulator. Charge decay methods expose one side of the insulator in vacuum to sequences of charged particles, light, and plasma, with a metal electrode attached to the other side of the insulator. Data are obtained by capacitive coupling to measure both the resulting voltage on the open surface and emission of electrons from the exposed surface, as well monitoring currents to the electrode. Instrumentation for both classical and charge storage decay methods has been developed and tested at Jet Propulsion Laboratory (JPL) and at Utah State University (USU). Details of the apparatus, test methods and data analysis are given here. The JPL charge storage decay chamber is a first-generation instrument, designed to make detailed measurements on only three to five samples at a time. Because samples must typically be tested for over a month, a second-generation high sample throughput charge storage decay chamber was developed at USU with the capability of testing up to 32 samples simultaneously. Details are provided about the instrumentation to measure surface charge and current; for charge deposition apparatus and control; the sample holders to properly isolate the mounted samples; the sample carousel to rotate samples into place; the control of the sample environment including sample vacuum, ambient gas, and sample temperature; and the computer control and data acquisition systems. Measurements are compared here for a number of thin film insulators using both methods at both facilities. We have found that conductivity determined from charge storage decay methods is 102 to 104 larger than values obtained from classical methods. Another Spacecraft Charging Conference presentation describes more extensive measurements made with these apparatus. This work is supported through funding from the NASA Space Environments and Effects Program and the USU Space Dynamics Laboratory Enabling Technologies Program.

Electrical behavior of contaminated distribution insulators exposed to natural wetting

Abstract: Working insulators begin failing as airborne contaminants and moisture from natural wetting combine on insulator surfaces to cause a drop in surface resistivity. This enables current to conduct across the insulators, thereby changing the electrical activity exhibited by the insulators when clean. If the drop in surface resistivity is severe enough, then the leakage current may escalate into a service interrupting flashover that degrades power quality. To help improve power quality, Texas A&M University developed an experimental methodology to investigate the electrical activity of contaminated insulators exposed to natural wetting. Leakage current and weather data obtained during experimentation showed that humidity and rain cause a deviation in the electrical activity of contaminated insulators from that of clean insulators. Analysis of leakage current data showed that this electrical activity was characterized by transient arcing behavior. Further, this nonsteady state activity is small, intermittent, and broad band in nature.

Semiconductor integrated circuit and method of fabricating same

Abstract: A semiconductor integrated circuit comprising thin-film transistors in each of which the second wiring is prevented from breaking at steps. A silicon nitride film is formed on gate electrodes and on gate wiring extending from the gate electrodes. Substantially triangular regions are formed out of an insulator over side surfaces of the gate electrodes and of the gate wiring. The presence of these substantially triangular side walls make milder the steps at which the second wiring goes over the gate wiring. This suppresses breakage of the second wiring.

Charge Storage, Conductivity and Charge Profiles of Insulators as Related to Spacecraft Charging

Abstract: Dissipation of charges built up near the surface of insulators due to space environment interaction is central to understanding spacecraft charging Conductivity of insulating materials is key to determine how accumulated charge will distribute across the spacecraft and how rapidly charge imbalance will dissipate To understand these processes requires knowledge of how charge is deposited within the insulator, the mechanisms for charge trapping and charge transport within the insulator, and how the profile of trapped charge affects the transport and emission of charges from insulators One must consider generation of mobile electrons and holes, their trapping, thermal de-trapping, mobility and recombination Conductivity is more appropriately measured for spacecraft charging applications as the "decay" of charge deposited on the surface of an insulator, rather than by flow of current across two electrodes around the sample We have found that conductivity determined from charge storage decay methods is 102 to 104 smaller than values obtained from classical ASTM and IEC methods for a variety of thin film insulating samples For typical spacecraft charging conditions, classical conductivity predicts decay times on the order of minutes to hours (less than typical orbit periods); however, the higher charge storage conductivities predict decay times on the order of weeks to months leading to accumulation of charge with subsequent orbits We found experimental evidence that penetration profiles of radiation and light are exceedingly important, and that internal electric fields due to charge profiles and high-field conduction by trapped electrons must be considered for space applications We have also studied whether the decay constants depend on incident voltage and flux or on internal charge distributions and electric fields; light-activated discharge of surface charge to distinguish among differing charge trapping centers; and radiation-induced conductivity Our experiments also show that "Malter" electron emission occurs for hours after turning off the electron beam This Malter emission similar to emission due to negative electron affinity in semiconductors is a result of the prior radiation or optical excitations of valence electrons and their slow drift among traps towards the surface where they are subsequently emitted This work is supported through funding from the NASA Space Environments and Effects Program

Electronic structure and the field emission mechanism of MgO-coated carbon nanotubes

Abstract: In an attempt to improve the field emission (FE) characteristics of carbon nanotubes (CNTs), we have performed a first-principles study on MgO-coated CNTs. A MgO slab covering a CNT tip under a strong electric field shows dielectric screening behaviours with applied electric fields up to 0.3 V A−1 and the effective dielectric constant approaches the bulk value within a few MgO layers. It is also found that the surface conduction band state of the MgO slab shifts down to the Fermi level as the applied electric field increases, indicating a FE mechanism different to that for CNTs without insulator coating. Electron emission via the surface conduction band of the insulator at the Fermi level is expected to enhance the FE current significantly, in agreement with a recent experiment.

Electric probe measurements of high-voltage sheath collapse in cathodic arc plasmas due to surface charging of insulators

Abstract: High-voltage sheath dynamics near a negatively biased substrate in cathodic arc plasmas are investigated using a biased electrical probe. Since the sheath is devoid of electrons, the sheath boundary can be inferred from the position where a positively biased probe draws no electron current. The extent of the sheath is primarily dependent on the plasma density, the ion velocity and the applied voltage. Using insulating substrates, the sheath boundary eventually retracts due to a dynamic reduction in the applied voltage. This reduction is caused by positive charge accumulation on the insulator surface. The collapse time of the sheath is dependent on the plasma density and the substrate characteristics. We believe this to be the first direct observation of the reduction in the width of the high-voltage sheath when implanting an electrical insulator using plasma-based ion implantation (PBII). This information is important when determining the optimal parameters for plasma-based ion implantation of insulators. Our measurements are compared with theoretical predictions based on the Child-Langmuir equations for high-voltage sheaths. By choosing appropriate values for the secondary electron coefficient the theory could be made to fit the experimental data. A discussion of the validity of the choice of secondary electron coefficients is presented.

Electrostatic chuck, plasma processing apparatus, and plasma processing method

Abstract: PROBLEM TO BE SOLVED: To provide an electrostatic chuck for stably and surely chucking and supporting an insulator substrate without causing abnormal discharge and dielectric breakdown. SOLUTION: In a placing stand 10 on which the insulator substrate G is placed; a rectangular block shaped susceptor 14 made of a conductor such as aluminum, and a rectangular frame shaped focus ring 16 made of an insulator such as quartz for surrounding around the susceptor 14, are provided on a base member 12. An electrostatic chucking part 24 comprises a three-layer structure of a lower dielectric layer 18, an electrode layer 20, and an upper dielectric layer 22 each formed on a principal face (upper face) of the susceptor 14 respectively by the thermal spraying method. The lower dielectric layer 18 and the upper dielectric layer 22 are made of ceramics of at least alumina (Al 2 O 3 ) or zirconia (ZrO 2 ) whose volume resistivity is 1×10 14 Ω cm or over. An output terminal of a DC power supply 34 is electrically connected to the electrode layer 20. COPYRIGHT: (C)2005,JPO&NCIPI

High accuracy foamed coaxial cable and method for manufacturing the same

Abstract: A foamed coaxial cable with high precision according to the present invention comprises: an internal conductor twisted with a plurality of electrically conductive wires; a foamed insulator with its low dielectric constant made of a porous tape body formed on the outer periphery of this internal conductor; an external conductor made of a number of electrically conductive thin wires braided on the outer periphery of this foamed insulator; and an outer sheath made of a resin having heat resistance formed on the outer periphery of this external insulator, wherein the precision of external diameter of the internal conductor is 4/1000 mm or less, the precision of external diameter size of the foamed insulator is ±0.02 mm, the insulator is formed in a completely circular shape, the precision of external diameter size of the external conductor is ±2%, the external conductor is formed in a completely circular shape, and the precision of characteristic impedance value between the internal conductor and the external conductor having the foamed insulator interposed therebetween is ±1 Ω.

Dynamo electric machine

Abstract: PROBLEM TO BE SOLVED: To provide a dynamo electric machine capable of fully assuring insulation performance of a slot insulator sticking to the bottom of a rotor slot, even if the excitation electric power rises. SOLUTION: A slot insulator 20 of the dynamo electric machine is molded into a U-shape, and a sheet 26 for a slot bottom surface of which is formed to be thicker than sheets 27a and 27b for a slot side surface. COPYRIGHT: (C)2003,JPO