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Relative permittivity

About: Relative permittivity is a research topic. Over the lifetime, 9426 publications have been published within this topic receiving 139883 citations. The topic is also known as: dielectric constant.


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Journal ArticleDOI
TL;DR: In this article, whispering gallery modes were used for very accurate permittivity and dielectric loss measurements of ultralow loss isotropic and uniaxially anisotropic single crystals.
Abstract: Whispering gallery modes were used for very accurate permittivity and dielectric loss measurements of ultralow loss isotropic and uniaxially anisotropic single crystals. Several materials including sapphire, YAG, quartz, and SrLaAlO4 were measured. The total absolute uncertainty in the real part of permittivity tensor components was estimated to be ±0.1%, limited principally by the uncertainty in sample dimensions. Imaginary parts of permittivities were measured with uncertainties of about 10%, limited by the accuracy of Q-factor measurements of whispering gallery modes. It has been observed that, for most crystals, dielectric losses can be approximated by a power function of absolute temperature only in limited temperature ranges. At temperatures between 4-50 K, losses are often affected by impurities, which are always present in real crystals.

319 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of snow density, impurities, stress, crystal size, and orientation on the permittivity and loss tangent of naturally occurring ice and snow are considered.
Abstract: The permittivity and loss tangent of naturally occurring ice and snow are considered. The direct-current conductivity is considered only when it is of importance to the alternating-current and radio-frequency properties. Laboratory measurements on pure ice, and deliberately contaminated ice, are included to help in explaining and extrapolating the behaviour of natural ice and snow. The lower band of frequencies from 10 c./sec. to 1 Mc./sec. is occupied by a relaxation spectrum in which the relative permittivity falls from approximately 100 to 3. The loss tangent reaches a maximum at a frequency which varies from 50 c./sec. to 50 kc./sec. as the temperature increases from −60°C. to 0°C. We are interested in the effect of snow density, impurities, stress, crystal size, and orientation. For frequencies much greater than 1 Mc./sec., the relative permittivity is 3.17±0.07. The loss tangent reaches a minimum value at approximately 1,000 Mc./sec. beyond which the dominant influence is infrared absorption. The minimum is 10−3 at 0°C or 2×10−5 at −60°C. These values are greatly increased by impurities or free water. Some possible applications to glaciological field measurements are mentioned.

302 citations

Journal ArticleDOI
TL;DR: In this paper, the authors derived a new scale length for two-dimensional effects in MOSFETs and discussed its significance, and showed that the utility of higher dielectric constant gate insulators decreases for /spl epsiv/expexp/exp/spl/exp eps/exp v/expv//sub 0/>-20 and that in no event should the insulator be thicker than the Si depletion depth.
Abstract: We derive a new scale length for two-dimensional (2-D) effects in MOSFETs and discuss its significance. This derivation properly takes into account the difference in permittivity between the Si channel and the gate insulator, and thus permits an accurate understanding of the effects of using insufficiently scaled oxide or thicker higher permittivity gate insulators. The theory shows that the utility of higher dielectric constant insulators decreases for /spl epsiv///spl epsiv//sub 0/>-20, and that in no event should the insulator be thicker than the Si depletion depth. The approach is also applied to double-gated FET structures, resulting in a new more general scale length formula for them, too.

301 citations

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the effective permittivity, breakdown strength, and electric energy density of dielectric nanocomposites using an effective medium approximation, modeling the nanocompositionite as a three-phase material by the double-inclusion method.
Abstract: Dielectric materials with large electric energy density are actively pursued for many applications. The authors analyze the effective permittivity, breakdown strength, and electric energy density of dielectric nanocomposites using an effective medium approximation, modeling the nanocomposite as a three-phase material by the double-inclusion method. The addition of nanoparticles enhances the permittivity but reduces the breakdown strength, making the potential gain in electric energy density small. In addition, the interfacial interaction shifts the “percolation” threshold toward lower volume fraction of nanoparticles. The analysis suggests that the microstructure of nanocomposites must be carefully controlled to maintain high dielectric strength and therefore realize enhanced electric energy density.

289 citations

Journal ArticleDOI
TL;DR: In this paper, optical and electrical measurements reveal uniform films over the thickness range 200-1000 A. They obtain optical absorption coefficients having values between those of Si and Ge and a relative permittivity having a value close to that of amorphous SiO2.
Abstract: Thermal sublimation of pure C60 and C70 has been used for depositing well‐characterized fullerene films on a variety of substrates. Film purity is determined by infrared absorption spectra and the extent of crystallinity of the face‐centered cubic structure by x rays. Thickness‐dependent optical and electrical measurements reveal uniform films over the thickness range 200–1000 A. We obtain optical absorption coefficients having values between those of Si and Ge and a relative permittivity having a value close to that of amorphous SiO2.

287 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023101
2022214
2021268
2020266
2019346
2018345