Giant Piezoelectric and Dielectric Relaxations in Statistical Mixtures

2006 ◽  
Vol 115 ◽  
pp. 209-214
Author(s):  
A.I. Chernobabov ◽  
A.V. Turik ◽  
G.S. Radchenko ◽  
S.A. Turik
Keyword(s):  
Dielectric Permittivity ◽  
Aspect Ratio ◽  
Heterogeneous Systems ◽  
Dielectric Constants ◽  
Dielectric Spectra ◽  
Physical Mechanisms ◽  
Dielectric Relaxations ◽  
First Time

The effective complex piezoelectric and dielectric constants of disordered heterogeneous systems of the type of statistical mixtures with the components in the form of spheroid-shaped particles equally oriented but randomly arranged in space were studied. It has been found for the first time that in such systems there appears a giant piezoelectric enhancement accompanied by a giant relaxation of piezoelectric coefficients and the dielectric permittivity. Piezoelectric and dielectric spectra differ significantly from the Debye ones and are of Davidson-Cole type. The influence of the aspect ratio of spheroids on the effects under consideration was studied. The physical mechanisms responsible for the anomalies in the behavior of piezoelectric coefficients and the dielectric permittivity were considered.

scholarly journals Dielectric Function of a Quantum-Confined Thin Film with a Modified Pöschel–Teller Potential

2018 ◽  
Vol 63 (12) ◽  
pp. 1109 ◽  
Author(s):  
Kh. A. Gasanov ◽  
J. I. Guseinov ◽  
I. I. Abbasov ◽  
F. I. Mamedov ◽  
D. J. Askerov
Keyword(s):  
Dielectric Permittivity ◽  
Electron Gas ◽  
Two Dimensional ◽  
Quantum Nanostructures ◽  
Carrier Scattering ◽  
Scattering Potential ◽  
Quantum Confined ◽  
Charge Carrier Scattering ◽  
First Time ◽  
Analytical Expressions

The spatial and time dispersions of the dielectric permittivity of an electron gas in quasi-two-dimensional quantum nanostructures are studied. The screening of the charge-carrier scattering potential in a quantum-confined film with a modified P¨oschel–Teller potential is considered for the first time. Analytical expressions for the dielectric permittivity are obtained.

scholarly journals Sunspot Seismology Theory

1990 ◽  
Vol 142 ◽  
pp. 149-157
Author(s):  
Joseph M. Davila
Keyword(s):  
Current Knowledge ◽  
Active Regions ◽  
Wavelength Dependence ◽  
Wave Power ◽  
Subsurface Structure ◽  
Scattering Process ◽  
Mode Wave ◽  
Physical Mechanisms ◽  
First Time

Recent observations have demonstrated that sunspots can absorb significant p-mode wave power, and that this absorption has a well defined wavelength dependence. These observations open, for the first time, the potential to deduce semi-empirically the subsurface structure of sunspots and active regions. Several physical mechanisms have been proposed to explain the absorption. In this paper, the proposed mechanisms are reviewed and their viability in view of the current knowledge of the scattering process is discussed.

Lattice Vibration Spectra XXIV*. Far-Infrared Reflection Spectra, Optical and Dielectric Constants, and Effective Charges of the Pyrite Type Compounds FeS2, MnS2, MnSe2, and MnTe2

1981 ◽  
Vol 36 (2) ◽  
pp. 184-190 ◽  
Author(s):  
H. D. Lutz ◽  
G. Kliche ◽  
H. Haeuseler
Keyword(s):  
Lattice Vibration ◽  
Far Infrared ◽  
Dielectric Constants ◽  
Reflection Spectra ◽  
Classical Oscillator ◽  
Infrared Reflection ◽  
Effective Charges ◽  
First Time ◽  
Born Effective Charge

AbstractFrom the far-infrared reflection spectra of the pyrite type compounds FeS2, MnS2, MnSe2, and MnTe2 we determined the TO and LO phonon frequencies at wave vector | q | ≈ 0 by both Kramers-Kronig analysis and classical oscillator fit method. In the case of MnSe2 and MnTe2 we found for the first time all five group-theoretically allowed reststrahlen bands. The phonon frequencies obtained from both single crystal and pressed pellet reflection measurements do not show any significant differences. The calculated optical and dielectric constants however are strongly affected by the surface quality of the sample. Effective ionic charges (Born effective charge, Szigeti charge) were calculated from the experimentally determined TO/LO splittings. They demonstrate an increasing ionicity in the order FeS2<MnTe2<MnSe2<MnS2.

Wet Clean Induce Pattern Collapse Mechanism Study

2012 ◽  
Vol 187 ◽  
pp. 253-256 ◽  
Author(s):  
C.C. Yang ◽  
C.C. Ko ◽  
H. Ou Yang ◽  
K.F. Chen ◽  
Y.Y. Peng ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Surfactant Solution ◽  
Future Generation ◽  
Collapse Mechanism ◽  
Mechanism Study ◽  
Induce Pattern ◽  
Dry Etch ◽  
First Time ◽  
Low K

Pattern collapse phenomenon was first time observed in BEOL application with the integration of ultra low-k film scheme. With the dimension and pitch shrinkage, the pattern collapse defects are getting worse during wet clean process. In this study, the line collapse defects can be significantly reduced by adding surfactant solution to the rinse liquid. Moreover, higher aspect ratio (>4) will also deteriorate the collapse window. In addition, the kink or bowing trench profile will induce localized stress at the interface. Accordingly, optimization of both wet clean and dry etch process are the successful keys to solve line collapse issue toward future generation and beyond.

Optical Response of Mixed Molybdenum Dichalcogenides for Solar Cell Applications Using the Modified Becke–Johnson Potential

2016 ◽  
Vol 71 (3) ◽  
pp. 213-223 ◽  
Author(s):  
Ushma Ahuja ◽  
Ritu Joshi ◽  
D.C. Kothari ◽  
Harpal Tiwari ◽  
K. Venugopalan
Keyword(s):  
Solar Cell ◽  
Dielectric Constants ◽  
Full Potential ◽  
Energy Bands ◽  
Absorption Coefficients ◽  
Augmented Plane Wave ◽  
Wave Technique ◽  
Degree Of Anisotropy ◽  
Dependent Absorption ◽  
First Time

AbstractEnergy bands and density of states (DOS) of mixed molybdenum dichalcogenides like MoS2, MoSeS, MoSe2, MoTe2, MoTeS, and MoTe0.5S1.5 are reported for the first time using the Tran–Blaha modified Becke–Johnson potential within full potential-linearised augmented plane wave technique. From the partial DOS, a strong hybridisation between the Mo-d and chalcogen-p states is observed below the Fermi energy EF. In addition, the dielectric constants, absorption coefficients, and refractivity spectra of these compounds have also been deduced. The integrated absorption coefficients derived from the frequency-dependent absorption spectra within the energy range of 0–4.5 eV show a possibility of using molybdenum dichalcogenides, particularly MoTe0.5S1.5, in solar cell applications. Birefringence and degree of anisotropy are also discussed using the data on refractivity and imaginary components of the dielectric constant.

Gas-Solid Interaction

1967 ◽  
Vol 22 (3) ◽  
pp. 355-358
Author(s):  
Manlio Sanesi ◽  
Vittoriano Wagner
Keyword(s):  
Heterogeneous Systems ◽  
Dielectric Constants ◽  
Electric Capacity

The adsorption of vapours of C6H6, CCl4 and cyclo-C6H12 respectively on γ-Al2O3 is followed by means of electric capacity measurements, and the dielectric isotherms are drawn for the three heterogeneous systems. The shape of the isotherms is discussed, and equations are proposed for calculating the apparent dielectric constants of the adsorbates from the slopes of the isotherms.

scholarly journals Free charge localization and effective dielectric permittivity in oxides

2016 ◽  
Vol 06 (02) ◽  
pp. 1630006 ◽  
Author(s):  
Mario Maglione
Keyword(s):  
Dielectric Permittivity ◽  
Ferroelectric Materials ◽  
Free Charge ◽  
Dielectric Spectra ◽  
Charge Localization ◽  
Giant Dielectric ◽  
Effective Dielectric Permittivity ◽  
Electronic Configurations ◽  
High Dielectric ◽  
Residual Impurities

This review will deal with several types of free charge localization in oxides and their consequences on the effective dielectric spectra of such materials. The first one is the polaronic localization at the unit cell scale on residual impurities in ferroelectric networks. The second one is the collective localization of free charge at macroscopic interfaces like surfaces, electrodes and grain boundaries in ceramics. Polarons have been observed in many oxide perovskites mostly when cations having several stable electronic configurations are present. In manganites, the density of such polarons is so high as to drive a net lattice of interacting polarons. On the other hand, in ferroelectric materials like BaTiO3 and LiNbO3, the density of polarons is usually very small but they can influence strongly the macroscopic conductivity. The contribution of such polarons to the dielectric spectra of ferroelectric materials is described. Even residual impurities as for example Iron can induce well-defined anomalies at very low temperatures. This is mostly resulting from the interaction between localized polarons and the highly polarizable ferroelectric network in which they are embedded. The case of such residual polarons in SrTiO3 will be described in more detail, emphasizing the quantum polaron state at liquid helium temperatures. Recently, several nonferroelectric oxides have been shown to display giant effective dielectric permittivity. It is first shown that the frequency/temperature behavior of such parameters is very similar in very different compounds (donor-doped BaTiO3, CaCu3Ti4O12, LuFe2O4, Li-doped NiO, etc.). This similarity calls for a common origin of the giant dielectric permittivity in these compounds. A space charge localization at macroscopic interfaces can be the key for such extremely high dielectric permittivity.

Basic models in dielectric spectroscopy of heterogeneous materials with semiconductor inclusions

2017 ◽  
Vol 13 (1) ◽  
pp. 36-57 ◽  
Author(s):  
A.S. Tonkoshkur ◽  
A.B. Glot ◽  
A.V. Ivanchenko
Keyword(s):  
Dielectric Permittivity ◽  
Dielectric Spectroscopy ◽  
Heterogeneous Systems ◽  
Heterogeneous Materials ◽  
Frequency Dispersion ◽  
Charge Carriers ◽  
Free Charge ◽  
Content Type ◽  
Dispersion Region ◽  
Semiconductor Particles

Purpose The purpose of this paper is to develop the models of the dielectric permittivity dispersion of heterogeneous systems based on semiconductors to a level that would allow to apply effectively the method of broadband dielectric spectroscopy for the study of electronic processes in ceramic and composite materials. Design/methodology/approach The new approach for determining the complex dielectric permittivity of heterogeneous systems with semiconductor particles is used. It includes finding the analytical expression of the effective dielectric permittivity of the separate semiconductor particle of spherical shape. This approach takes into account the polarization of the free charge carriers in this particle, including capturing to localized electron states. This enabled the authors to use the known equations for complex dielectric permittivity of two-component matrix systems and statistical mixtures. Findings The presented dispersion equations establish the relationship between the parameters of the dielectric spectrum and electronic processes in the structures like semiconductor particles in a dielectric matrix in a wide frequency range. Conditions of manifestation and location of the different dispersion regions of the complex dielectric heterogeneous systems based on semiconductors in the frequency axis and their features are established. The most high-frequency dispersion region corresponds to the separation of free charge carriers at polarization. After this region in the direction of reducing of the frequency, the dispersion regions caused by recharge bulk and/or surface localized states follow. The most low-frequency dispersion region is caused by recharging electron traps in the boundary layer of the dielectric matrix. Originality/value Dielectric dispersion models are developed that are associated with: electronic processes of separation of free charge carriers in the semiconductor component, recapture of free charge carriers in the localized electronic states in bulk and on the surface of the semiconductor and also boundary layers of the dielectric at the polarization. The authors have analyzed to situations that correspond applicable and promising materials: varistor ceramics and composite structure with conductive and semiconductor fillers. The modelling results correspond to the existing level of understanding of the electron phenomena in matrix systems and statistical mixtures based on semiconductors. It allows to raise efficiency of research and control properties of heterogeneous materials by dielectric spectroscopy.

Dielectric spectra in molecular single crystals

Open Physics ◽  
2009 ◽  
Vol 7 (1) ◽  
Author(s):  
Ferid Bashirov ◽  
Nail Gaisin
Keyword(s):  
Dielectric Permittivity ◽  
Single Crystals ◽  
Three Dimensional ◽  
Local Symmetry ◽  
Theoretical Description ◽  
Practical Application ◽  
Dielectric Spectra ◽  
Jump Model ◽  
Relaxation Polarization ◽  
Polarization Mechanism

AbstractA theoretical description of the frequency-dependent, complex dielectric permittivity of molecular single crystals is given within the framework of the relaxation polarization mechanism. The extended angular jump model, accounting for the local symmetry distortion, simulates the hindered molecular motion. Both the real and imaginary parts of dielectric permittivity are anisotropic in all cases of point symmetry groups of molecule motion, except for those of the cubic crystallographic system. The three-dimensional graphs of dielectric spectra, which can be helpful in practical application, illustrate the predicted spectra.

Sign in / Sign up

Export Citation Format

Share Document