مجله فیزیک کاربردی
سال هفتم شماره 1 (پیاپی 12، بهار و تابستان 1396)

In this paper, using COMSOL Muliphysics software, GaAs ÝÇåÏ film growth prepared by the chemical vapour deposition Method was simulated. A mixed multiphysics model was used for this purpose. In order to compare the simulation results with those of from experiment, all of the steps and details regarding the GaAs growth reactions were utilized on the basis of an experimental research. Simulation steps including model designing, mesh analysis, chemical and thermodynamic relations and complete sets of chemical Reactions were investigated. Crucial parameters such as the flow rate, pressure and the temperature distribution within the chamber were studied and the graphical results were presented for analyzing.Then, the effect of substrate temperature on growth rate and mass distribution of thin film was investigated. Comparison between the simulation result and experimental data determines the accuracy of the represented model and also provide a promising description for dependency of film growth on substrate temperature.

Globular Clusters are the oldest populations of stars of our Galaxy which their stars have unique characteristics. Similar initial mass, equal age and equal distance from us are common characteristics of stars of a cluster. Distribution of the globular clusters is very interesting. Most of them are in galactic halo and specially in halo near to the galactic center. Globular clusters nearer to central part of our galaxy have different evolution respect to others, due to external force of Galactic center. Because of the subject Cluster M13 respect to Omega Centaurs are nearer to galactic center and it has less number and smaller size. In this work we obtained distribution of the globular clusters in galactic coordinates. Meanwhile a list of 133 Globular clusters from 150 ones is presented and the most luminous ones in the north and south sky which are observable by naked eye, and their general characteristics are studied.

In this paper, optical properties of a hybrid system consisting of a semiconductor quantum dot placed in the vicinity of a metal (plasmonic) nanoparticle with spherical and ellipsoidal symmetry is investigated. An analytical expression for the absorption and dispersion using the density-matrix approach via semi-classical theory is derived and numerically discussed. In our numerical calculations, we have used Au and Ag metals, because these metals have predominately been the materials of choice for plasmonic applications around the optical frequencies. It is shown that the optical dispersion and absorption strongly depends on the particle size and shape, the quantum dot-nanoparticle distance (the semiconductor quantum dot-plasmonic nanoparticle center-to-center distance), and the dielectric constant of host matrix. It is important to note that dependences of optical properties of a hybrid system on changing and adjusting of the geometrical parameters of system can be used for optical sensing purposes and design of tunable bio-nanosensors.

In this paper, we investigate thermoelectric properties of polyaniline molecular junction for three different coupling geometries of the coupling of the molecule to the electrodes including para (symmetric), meta and ortho (asymmetric) configurations. The selected electrodes are three dimensional and face center cubic (FCC) similar to the experimental works. The nonequilibrium Green function formalism is used to obtain thermoelectric coefficients in nonlinear response regime. The Hamiltonian of the system is described by tight binding method. The results show, in asymmetric coupling, the electrical conductance and thermal conductance decrease whereas thermopower and figure of merit show better behavior and increase in meta and ortho configurations. Therefore asymmetry in polyaniline molecular junction causes an improvement in thermoelectric efficiency of the junction that is a desirable result for scientists. On the other hand, the oscillating behavior of thermopower indicates the kind of carriers and the place of molecular energy levels relative to the Fermi energy change during the thermal tunneling.

In this paper,the structural, electronic and optical properties of Mercury Telluride (HgTe) in hexagonal phase have been studied. The calculations have been performed with pseudopotantial method in density functional theory framework by using Quantum-Espresso package. It can be seen from band structure calculation that the cinnabar phase has semiconducting property. The calculation of the real part of dielectric function leads to refractive index 4.489 for hexagonal phase.
lculation that the cinnabar phase has semiconducting property. The calculation of the real part of dielectric function leads to refractive index 4.489 for hexagonal phase.

In this paper, we calculate the electronic transmission coefficient of a benzene ring connected to two metallic leads via the para and meta contacts in the presence of electron-electron interaction (Hubbard model). For this purpose, we use the Green’s function technique and the nearest neighbor tight-binding approach. Then, we obtain the electronic conductance as a function of energy by a numerical self-consistent method due to the shape of interaction. The result show that in the presence of the electron-electron interaction, the positions of peaks, dips and Fano resonances which are appeared in the conductance spectra will be shifted. Moreover, the value of the conductance at zero energy strongly depends on variation of the Hubbard parameter value; which leads to the metal-insulator transition in the meta case. Considering of the electron - electron interaction within the self-consistent approach gives a realistic viewpoint with respect to the models in which this interaction is considered by the mean field approximation.