Effective Conductivity Modelling of Polycrystalline ZnO Thin Films

1995 ◽  
Vol 403 ◽  
Author(s):  
M. Robles ◽  
J. Tagüeña-Martínez ◽  
J. A. Del Río
Keyword(s):  
Thin Films ◽  
Effective Conductivity ◽  
Structural Information ◽  
Low Cost ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Geometrical Parameters ◽  
Layer Adsorption ◽  
Conductivity Modelling

AbstractChemically deposited thin films have multiple applications, in particular for low cost solar cells production. However, due to their inhomogeneous structure, it is very difficult to predict their physical properties. In this work we present a mean field approximation to model the effective electrical conductivity of the polycrystalline ZnO chemical deposited thin films. Our model considers elliptical inclusions randomly distributed in a matrix. We compare with the experimental results of two different deposition methods: spray pyrolysis [1] and successive ion layer adsorption and reaction (SILAR) [2]. Supported by the structural information of these samples, we select the elliptical geometrical parameters. We obtain a good fit of the experimental measurements with our calculation.

scholarly journals Optical bistability in two-dimensional nonlinear composites of coated cylinders with nonlinear core and graded shell

2020 ◽  
Vol 7 ◽  
pp. 6
Author(s):  
Ya M. Wu ◽  
Guo Q. Chen ◽  
Wen C. Wu ◽  
Yi X. Wang ◽  
Yang Huang
Keyword(s):  
Optical Bistability ◽  
Near Field ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Geometrical Parameters ◽  
Core Radius ◽  
The Core ◽  
Nonlinear Composite ◽  
Incident Frequency

The intrinsic optical bistability of the nonlinear composite consisting of coated cylinders with nonlinear core and graded Drude shell is investigated with self-consistent mean-field approximation. We derive the nonlinear equation of near field for such graded composite in the quasistatic limit. We demonstrate that the bistability threshold and the bistable width are highly dependent on the core radius, the incident frequency, and the graded coefficient of the coated cylinder inclusion. It is found that the optical bistability appears only when the core radius and the incident frequency satisfy some specific conditions. Therefore, the optical bistability for nonlinear composite materials may be optimized by the suitable adjustment of the physical and geometrical parameters. Our results may be helpful for the design of the nonlinear device with appropriate bistability.

POLARIZATION PROPERTIES OF FERROELECTRIC THIN FILMS UNDER DIFFERENT BOUNDARY CONDITIONS

2009 ◽  
Vol 16 (04) ◽  
pp. 507-512 ◽  
Author(s):  
HUI CHEN ◽  
TAIMIN CHENG ◽  
SIQUN CHEN ◽  
TIECHEN GANG
Keyword(s):  
Thin Films ◽  
Boundary Condition ◽  
Boundary Conditions ◽  
Mean Field ◽  
Film Surface ◽  
Transverse Field ◽  
Field Approximation ◽  
Ferroelectric Thin Films ◽  
Mean Field Approximation ◽  
Structure Variation

By taking into account two types of boundary conditions (BC), free boundary condition (FBC) and zero boundary condition (ZBC), an improved transverse Ising model with the consideration of surface transition layers (STL) is used to describe the polarization properties of ferroelectric thin films in the framework of the mean field approximation. Functions representing the intra-layer and inter-layer couplings are introduced to characterize the BC and STL, which reflect the structure variation of film surface. Comparing the results obtained by employing FBC and ZBC, some effects of BC are derived in the model, which demonstrated that the BC play important roles on the properties of ferroelectric thin films. It is shown that the effect of ZBC can extend to deeper film than that of FBC. When different BC are adopted, competition between the fields (depolarization field and transverse field) and BC induces some different and interesting phenomena. Some theoretical results in this paper are found to be in reasonable accordance with experimental data and have some application importance.

The Determination of the Magnetoelectric Coupling Coefficient in Ferroelectric–Ferromagnetic Composite Based on PZT–Ferrite

2013 ◽  
Vol 58 (4) ◽  
pp. 1401-1403 ◽  
Author(s):  
J.A. Bartkowska ◽  
R. Zachariasz ◽  
D. Bochenek ◽  
J. Ilczuk
Keyword(s):  
Dielectric Permittivity ◽  
Coupling Coefficient ◽  
Mean Field ◽  
Field Approximation ◽  
Theoretical Description ◽  
Magnetoelectric Coupling ◽  
Mean Field Approximation ◽  
Dielectric Measurements ◽  
Temperature Dependences ◽  
Multiferroic Composite

Abstract In the present work, the magnetoelectric coupling coefficient, from the temperature dependences of the dielectric permittivity for the multiferroic composite was determined. The research material was ferroelectric-ferromagnetic composite on the based PZT and ferrite. We investigated the temperature dependences of the dielectric permittivity (") for the different frequency of measurement’s field. From the dielectric measurements we determined the temperature of phase transition from ferroelectric to paraelectric phase. For the theoretical description of the temperature dependence of the dielectric constant, the Hamiltonian of Alcantara, Gehring and Janssen was used. To investigate the dielectric properties of the multiferroic composite this Hamiltonian was expressed under the mean-field approximation. Based on dielectric measurements and theoretical considerations, the values of the magnetoelectric coupling coefficient were specified.

scholarly journals Hexagonal-Shaped Spin Crossover Nanoparticles Studied by Ising-Like Model Solved by Local Mean Field Approximation

2021 ◽  
Vol 7 (5) ◽  
pp. 69
Author(s):  
Catherine Cazelles ◽  
Jorge Linares ◽  
Mamadou Ndiaye ◽  
Pierre-Richard Dahoo ◽  
Kamel Boukheddaden
Keyword(s):  
Spin Crossover ◽  
Hexagonal Lattice ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Ligand Field ◽  
Order And Disorder ◽  
The Matrix ◽  
Local Mean ◽  
Parameter Values

The properties of spin crossover (SCO) nanoparticles were studied for five 2D hexagonal lattice structures of increasing sizes embedded in a matrix, thus affecting the thermal properties of the SCO region. These effects were modeled using the Ising-like model in the framework of local mean field approximation (LMFA). The systematic combined effect of the different types of couplings, consisting of (i) bulk short- and long-range interactions and (ii) edge and corner interactions at the surface mediated by the matrix environment, were investigated by using parameter values typical of SCO complexes. Gradual two and three hysteretic transition curves from the LS to HS states were obtained. The results were interpreted in terms of the competition between the structure-dependent order and disorder temperatures (TO.D.) of internal coupling origin and the ligand field-dependent equilibrium temperatures (Teq) of external origin.

Geometrical and Transport Properties of Disordered Fibre Networks: Analytical Results

1997 ◽  
Vol 11 (20) ◽  
pp. 867-875 ◽  
Author(s):  
A. A. Rodríaguez ◽  
E. Medina
Keyword(s):  
Probability Distribution ◽  
Transport Properties ◽  
Geometrical Structure ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Fracture Networks ◽  
Simplified Models ◽  
Fibre Density ◽  
Line Network

We study novel geometrical and transport properties of a 2D model of disordered fibre networks. To assess the geometrical structure we determine, analytically, the probability distribution for the number of fibre intersections and resulting segment sizes in the network as a function of fibre density and length. We also determine, numerically, the probability distribution of pore perimeters and areas. We find a non-monotonous behavior of the perimeter distribution whose main features can be explained by solving for two simplified models of the line network. Finally we formulate a mean field approximation to conduction, above the percolation threshold, using the derived results. Relevance of the results to fracture networks will be discussed.

The gas-liquid surface of the penetrable sphere model. II

1978 ◽  
Vol 358 (1694) ◽  
pp. 267-280 ◽  
Keyword(s):  
Surface Tension ◽  
Correlation Function ◽  
Liquid Surface ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Intermolecular Potential ◽  
Direct Correlation Function ◽  
Sphere Model ◽  
One Dimensional

The direct correlation function between two points in the gas-liquid surface of the penetrable sphere model is obtained in a mean-field approximation. This function is used to show explicitly that three apparently different ways of calculating the surface tension all lead to the same result. They are (1) from the virial of the intermolecular potential, (2) from the direct correlation function, and (3) from the energy density. The equality of (1) and (2) is shown analytically at all temperatures 0 < T < T c where T c is the critical temperature; the equality of (2) and (3) is shown analytically for T ≈ T c , and by numerical integration at lower temperatures. The equality of (2) and (3) is shown analytically at all temperatures for a one-dimensional potential.

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