نشریه پژوهش سیستم های بس ذره ای
سال چهارم شماره 2 (پیاپی 8، زمستان 1393)

In this work، Cd1-xZnxS (x=0. 5، 0. 8) are synthesized by the microwave irradiation. The structural properties of powders were studied using X-Ray diffraction، Fourier transform infra-red and energy dispersive X-ray. The XRD study show that Cd0. 5Zn0. 5S and Cd0. 8Zn0. 2S crystallize in a Cubic and Hexagonal structures respectively. Decreasing the crystallite sizes were observed with Zn doping in lattice. The FTIR analysis confirms the formation of bonds. The EDAX spectrophotometry shows the appropriate compositions. Cd1-xZnxS (x=0. 5، 0. 8) thin films were made using Cd1-xZnxS (x=0. 5، 0. 8) nanoparticles in thermal evaporation system on glass substrate under 200°C. For investigating the impact of heat treatment on optical properties of films، specimens were kept at various temperatures under vacuum conditions. The structural، optical، and surface morphological properties of the films were studied using energy dispersive X-ray، X-Ray diffraction، UV visible spectrophotometer. The result shows that with increasing the annealing temperature، absorption coefficient، refractive index increase. However، with increment of annealing temperature، the bad gap energy decreases. Also، with increasing the doping level of Zn on Cd sites in compound، a reduction in absorption coefficient، refractive index was observed.

In this paper, carbon coated iron particles were synthesized by a DC arc-discharge method using a semi-automatic homemade reactor. The produced particles were studied using X-Ray diffraction, field-emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The production mechanism for core-shell particles in arc-discharge process was investigated. In production process and inside the created plasma, between anode and cathode, Fe-C particles are formed in a carbon-rich atmosphere. The carbon content of the iron alloy in liquid phase is more than the solid solubility. So, by decreasing cathode temperature, the excess carbon is ejected from the alloy and forms a carbon layer around the iron particles. The static and dynamic magnetic properties, in 1-18 GHz frequency range, were investigated and radar absorbing properties of the core-shell particles was studied.

The incompressibility coefficients of cold symmetric nuclear matter to 4-th order of expansion, have been studied in lowest order constrained variation (LOCV) method with relativistic corrections by using interaction which has been fitted to nucleon-nucleon scattering data as well as potential. In this research, the relativistic corrections of one-body and two- body cluster energy and boost interaction corrections have been calculated. Also the isobaric incompressibility coefficients of asymmetric nuclear matter have been calculated at saturation density as a function of asymmetric parameter. The isobaric incompressibility coefficient of asymmetric nuclear matter decreases almost linearly by increasing asymmetric parameter. The results are in comparable with other many-body calculations and experimental predictions.

In this research, Indium Tin Oxide (ITO) thin films have been deposited with the rate of 0.10 nm/s and thicknesses of about 50, 100, 170 and 250 nm by electron beam method on glass substrates. During deposition the substrates temperatures were kept constant at 400 ̊C. X-ray Diffraction (XRD), X-ray Reflectivity (XRR) techniques are used to for thin films structural analysis ITO thin films. Their optical properties were analyzed using the spectroscopy of UV-Vis)310-800 nm(. Also Elemental analysis of matter was carried out with Energy dispersive X-ray analysis (EDS) system. MATLAB, GENX and XPOWDER softwares were used to data analysis. Then, real thickness (nm), mean electron density (e/Å3) and the roughness (nm) of ITO thin films were determined. For thicknesses 50, 100, 170 and 250 nm band gaps were determined 3.47, 3.58, 3.71 and 3.87 eV respectively. The results show that by increasing in thin films thickness, the mean particles sizes have been grown, optical transmittance, absorbance and band gap are decreased, increased and increased respectively.

In the present work the differential and total cross section for positron-hydrogen collisions has been calculated by using Coulomb wave in excitation channel. The method has been applied to study and transition of atomic hydrogen by positron impact at intermediate energy range Calculation of the scattering amplitude has been done by handling a new analytical method. Because of absence the experimental data in the discussed energy range our results have been compared with the available theoretical data. The results denote that considering Coulomb wave as the projectile wave function leads to better results in comparison with plane wave at intermediate energy range.

In this work the effect of size on the emission properties of InAs/GaAs conical-shaped quantum dot (QD) lasers coupled to wetting layer was investigated. At first, by use of numerical method of finite element and effective mass approximation, the Schrodinger equation for two types of QDs were solved and the envelop functions for the ground state, first excited state, and wetting layer state were obtained. Then, using the envelop functions, the transition dipole moments and spontaneous lifetimes were calculated and their dependence on size was investigated. In continue the output power of QD laser was calculated by use of semiconductor laser rate equations. The results show by increasing the QD size, the energy eigenvalues as well as the spontaneous lifetime decreases noticeably. We found out that the laser output decreases with increasing the size of QD. Respecting to this fact that the transition frequencies are also dependent on the size, the output frequency is revealed to shift by changing the QD size.