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Insulator (electricity)

About: Insulator (electricity) is a research topic. Over the lifetime, 15941 publications have been published within this topic receiving 108950 citations. The topic is also known as: electrical insulator.


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Journal ArticleDOI
TL;DR: In this paper, the authors used scanning probe microscopy/spectroscopy (STM/STS) and angle-resolved photoelectron spectroscopy to show that TDS Na3Bi is 2D topological insulators with bulk bandgaps >400 meV in the absence of electric field.
Abstract: The electric field induced quantum phase transition from topological to conventional insulator has been proposed as the basis of a topological field effect transistor [1-4]. In this scheme an electric field can switch 'on' the ballistic flow of charge and spin along dissipationless edges of the two-dimensional (2D) quantum spin Hall insulator [5-9], and when 'off' is a conventional insulator with no conductive channels. Such as topological transistor is promising for low-energy logic circuits [4], which would necessitate electric field-switched materials with conventional and topological bandgaps much greater than room temperature, significantly greater than proposed to date [6-8]. Topological Dirac semimetals(TDS) are promising systems in which to look for topological field-effect switching, as they lie at the boundary between conventional and topological phases [3,10-16]. Here we use scanning probe microscopy/spectroscopy (STM/STS) and angle-resolved photoelectron spectroscopy (ARPES) to show that mono- and bilayer films of TDS Na3Bi [3,17] are 2D topological insulators with bulk bandgaps >400 meV in the absence of electric field. Upon application of electric field by doping with potassium or by close approach of the STM tip, the bandgap can be completely closed then re-opened with conventional gap greater than 100 meV. The large bandgaps in both the conventional and quantum spin Hall phases, much greater than the thermal energy kT = 25 meV at room temperature, suggest that ultrathin Na3Bi is suitable for room temperature topological transistor operation.

89 citations

Journal ArticleDOI
TL;DR: The uses and limitations of the electrostatic probe for the measurement of charge densities on insulating surfaces are discussed in this article, where 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; and (ii) a robotic control system has been developed which enables the probe to follow and scan a wide range of axi-symmetric insulator profiles.
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.

89 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the characteristics of an insulator string covered with snow or ice and the application of these results to the insulation design and maintenance of a transmission line in a heavy snow area.
Abstract: The authors describe the results of an investigation into the withstand voltage characteristics of an insulator string covered with snow or ice and the application of these results to the insulation design and maintenance of a transmission line in a heavy snow area. It was found that the characteristics of withstand voltage were affected by the specific gravity of snow, the conductivity of water melted from snow, the height of snow, and the ratio of snow-covered length. The lightning impulse flashover voltage of insulator string covered with snow is much lower than that of nonsnow-covered insulator, indicating that the efficiency of lightning protection greatly decreases under snowing conditions. When transmission lines pass through a heavy snow area, an extension of the transmission system fault is feared in 54 and 275 kV transmission lines because the existing insulator string length does not have sufficient dielectric strength for temporary AC overvoltage and switching surge. >

88 citations

Journal ArticleDOI
TL;DR: Experimental results verify that the transmission power can meet power supply requirements and the designed charging system can be operated stably under the high-voltage condition.
Abstract: A novel high-voltage operation featured wireless power transfer system for monitoring equipment charging on a 110-kV high-voltage transmission line based on magnetic resonant coupling is studied and designed in this paper. With consideration of operation environment on transmission line and electrical transmission tower, an overall scheme is proposed through installation position, coupling structure, and driving topology design. In order to improve the system's suitability in high-voltage environment, related optimization methods including constraining power flow path, improving quality factor, and coupling have been adopted. Since the coupling coils are fixed at both ends of an insulator string, a barrel-shaped high-permeability material layer is added to constrain the magnetic field distribution. Moreover, cross impacts between transmission line and the charging system are analyzed. The influence of a power frequency magnetic field on the charging system is calculated and electric distribution of the insulator string with the charging system is simulated. Analysis results indicate that cross impacts can be negligible. Experimental results verify that the transmission power can meet power supply requirements and the designed charging system can be operated stably under the high-voltage condition.

87 citations

Journal Article
TL;DR: In this paper, the authors studied the band alignment at the semiconductor/insulator interface using density functional theory and found that the valence band offset increases near linearly with the interfacial oxygen coordination.
Abstract: While the physics of the Schottky barrier is relatively well understood, much less is known about the band alignment at the insulator/insulator interface. As a model problem we study theoretically the band alignment at the technologically important $\\mathrm{Si}{\\mathrm{O}}_{2}∕\\mathrm{Hf}{\\mathrm{O}}_{2}$ interface using density functional theory. We report several different atomic level models of this interface along with their energies and electronic properties. We find that the valence band offset increases near linearly with the interfacial oxygen coordination, changing from $\\ensuremath{-}2.0\\phantom{\\rule{0.3em}{0ex}}\\mathrm{eV}\\phantom{\\rule{0.3em}{0ex}}\\text{to}\\phantom{\\rule{0.3em}{0ex}}1.0\\phantom{\\rule{0.3em}{0ex}}\\mathrm{eV}$. For the fully oxidized interface the Schottky limit is reached. We propose a simple model, which relates the screening properties of the interfacial layer to the band offset. Our results may explain a somewhat confusing picture provided by recent experiments.

87 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023368
2022892
2021224
2020478
2019561
2018629