Magnetic field effect on the binding energy of a hydrogenic impurity in GaAs-Ga₁₋xAlxAs superlattice

The binding energy of shallow hydrogenic impurity in GaAs-GaAs-Ga₁₋xAlxAs superlattices, under the influence of magnetic field, is theoretically studied following a variational procedure within the effective-mass approximation and the new analytic wave function of superlattice. The binding energy is calculed and analyzed for various applied magnetic field, different impurity position and superlattice with different widths. The result show that the impurity binding energy depends strongly on the impurity position and magnetic field. It is also found that for impurities located at the center of the quantum wells of superlattices the binding energy always increases with the applied magnetic field

High Second-Order Nonlinear Susceptibility Induced in GaN/AlxGa1 – xN Coupled Quantum Well for Infrared Photodectors Application

The second harmonic generation (SHG) of GaAs/AlxGa1 − xAs a wurtzite coupled quantum wells (CQWs) is studied theoretically for different widths of well, barrier and values Al concentration, taking into account the strain-induced piezoelectric (PZ) effects. The analytical expression of the SHG susceptibility is deduced by using the compact density matrix approach. The confined wave functions and energies of electrons GaN/AlxGA1 – x N are calculated in the effective-mass approximation, solving the Schrödinger equation by Numerov’s method using six order approximations for the derivatives. The calculated results also reveal that by adjusting the widths of well, the barrier and Al concentration respectively, a set of optimal structural parameters can be found for obtaining a strong SHG susceptibility. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2777

Absorption Coefficients of GaN / AlxGa1 – xN Core-Shell Spherical Quantum Dot

The total absorption coefficient in spherical GaN/AlxGa1 – xN core-shell nanodots is theoretically investigated taking into account effective mass approximation. The influence of the nanosystem geometry upon the energy spectrum and transition energy δE associated to interlevel transitions is studied. We found that the energy transitions vary with the core-shell radius, and the peak position of the total absorption coefficient is greatly affected by changing of the shell radius. The possibility of tuning the resonant energies by using the geometric core shell effect of the spatial confinement can be useful in the optoelectronic devices applications. Also we observed that the magnitudes of the total absorption coefficient can be increased significatly compared traditional cases of QD, and the peaks are shifted to the lower energies. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2960

Acyclicity in edge-colored graphs

A walk $W$ in edge-colored graphs is called properly colored (PC) if every pair of consecutive edges in $W$ is of different color. We introduce and study five types of PC acyclicity in edge-colored graphs such that graphs of PC acyclicity of type $i$ is a proper superset of graphs of acyclicity of type $i+1$, $i=1,2,3,4.$ The first three types are equivalent to the absence of PC cycles, PC trails, and PC walks, respectively. While graphs of types 1, 2 and 3 can be recognized in polynomial time, the problem of recognizing graphs of type 4 is, somewhat surprisingly, NP-hard even for 2-edge-colored graphs (i.e., when only two colors are used). The same problem with respect to type 5 is polynomial-time solvable for all edge-colored graphs. Using the five types, we investigate the border between intractability and tractability for the problems of finding the maximum number of internally vertex disjoint PC paths between two vertices and the minimum number of vertices to meet all PC paths between two vertices

FANO resonances in solid-fluid one and two dimensional systems

The gaol of this paper is to demonstrate that the propagation of acoustic waves in a single slab made of a homogeneous one dimensional (1D) solid embedded in a fluid at oblique incidence on a slab made of two dimensional (2D) rectangular rods immersed in a fluid, can exhibit transmission zeros near resonances the so-called Fano resonances

Numerical study of electrical characteristics of conjugated polymer light-emitting diodes

Conjugated polymers now provide a class of processible, film-forming semiconductors and metals. In this work, the electronic properties of polymer lightemitting diodes devices are numerically studied. Our results show how an insulating buffer layer with suitable thickness decreases the barrier height at the cathode and therefore increases the electron injection. We also discuss the effects from persistent charged traps

Schottky Diodes and Thin Films Based on Copolymer: Poly(aniline-co-toluidine)

Poly(aniline-co-o-toluidine) (PANI-co-POT) thin films were deposited on indium tin oxide- (ITO-) coated glass substrates by electrochemical polymerization under cyclic voltammetric conditions from aniline-co-o-toluidine monomer in an aqueous solution of HCl as a supporting electrolyte. These measurements showed that the optical band gap of the copolymer films is on the order of 2.65 eV. On the other hand, ITO/PANI-co-POT/Al devices were fabricated by thermal evaporation of Aluminum circular electrodes on the as-deposited PANI-co-POT films. The Current-Voltage characteristics of these devices are nonlinear. The diode parameters were calculated from I-V characteristics using the modified Shockley equation. The C-F characteristics were also measured

Odd properly colored cycles in edge-colored graphs

It is well-known that an undirected graph has no odd cycle if and only if it is bipartite. A less obvious, but similar result holds for directed graphs: a strongly connected digraph has no odd cycle if and only if it is bipartite. Can this result be further generalized to more general graphs such as edge-colored graphs? In this paper, we study this problem and show how to decide if there exists an odd properly colored cycle in a given edge-colored graph. As a by-product, we show how to detect if there is a perfect matching in a graph with even (or odd) number of edges in a given edge set

Dielectric Behavior of Ceramic (BST)/Epoxy Thick Films

Composite materials were made by mixing powders of Ba1−xSrxTiO3 (x=0.2 and 0.4) ceramics and epoxy resin with various volume fractions (vol%). Dielectric measurements of these composites were performed as a function of filler ratio in the range 100–360°K at 10 KHz. The dielectric constant of the composite increased with increasing volume fraction varies slightly with temperature. The 20 vol% of BST(0.4)-epoxy composite had the highest dielectric constant of 19.4 and dielectric loss tangent of 0.027. Among the dielectric mixing models presented, the model of Lichtenecker shows the best fit to the experimental data for both composites