Publications internationales
Résumé: The structural, elastic, electronic, magnetic, and optical properties of Ca1-xCrxTe (x = 0, 0.25, 0.50 and 0.75) compounds in the ferromagnetic Rock-Salt phase were investigated. The study is done using the method of Plane Waves Linearized and Augmented with Full Potential (FP-LAPW) having as theoretical basis in Density Functional Theory (DFT). We used the GGA-PBE approximation for the calculation of structural properties, and the Tran-Blaha modified Becke-Johnson (TB-mBJ) approximation for the calculation of electronic and optical properties. The objective is to see the impact of the incorporation of chromium (Cr) on the different properties of CaTe. Structural properties study showed that ternary compounds are stable in ferromagnetic phase and the lattice parameter "a" decrease when the Cr rate increase. The elastic properties results showed that all ternary compounds are mechanically stable …
Résumé: Ordered vacancy compound CuIn3Se5 thin flms of nearly perfect stoichiometry were successfully deposited onto glass substrates by thermal evaporation technique from ball-milled powder. The deposited flms were annealed in vacuum. The structural and compositional properties of the powder were characterized by x-ray difraction (XRD) and x-ray photoelectron spectroscopy, and the obtained results confrm the ordered defect nature of the ball-milled powder. The obtained thin flms were characterized by XRD, scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy, atomic force microscopy (AFM), ultraviolet–visible spectroscopy, and electrical Hall-efect measurements. The efect of a high annealing process on the structural, morphological, optical and electrical properties of CuIn3Se5 thin flms was investigated. XRD results showed that both flms are polycrystalline in nature and have an ordered defect structure. The crystallization of the flms increases after annealing. Both SEM and AFM images indicated that the annealed flm shows a rough surface with large grain size as compared to the as-grown CuIn3Se5 flms. Optical properties reveal a high absorption coefcient (α > 104 cm−1), and the energy band gap was found to be 1.27 eV for annealed CuIn3Se5 flms. The optical constant, such as extinction coefcient k, of both flms was also discussed. Hall-efect measurement results showed that the as-grown and annealed CuIn3Se5 flms have n-type conductivity. The mobility and the carrier concentration of the flms increase after annealing, while the resistivity decreases. The obtained CuIn3Se5 thin flms with suitable properties make them promising semiconductor material for photovoltaic solar cell applications.
Résumé: The CuAlxGa1−xTe2 powders used in this study were made by planetary ball milling the source element powders (Cu, Al, Ga and Te). All of the produced powders and thin films were polycrystalline, with a tetragonal chalcopyrite structure with (1 1 2) orientation, according to XRD analysis. The structural and electronic features of the CuAlxGa1−xTe2 semiconductors were predicted using ab initio calculations based on Density Function Theory (DFT). The acquired results demonstrated that once the Al concentration increased, the lattice parameters and energy band gap changed in a way that was consistent with the experimental data.
Résumé: Nanoparticles Cu 2 SnSe 3 alloys were synthesized by mechanical alloying from mixtures of pure crystalline Cu, Sn and Se powders using a low cost planetary ball milling process optimizing the milling duration and the rotational speed. The properties of Cu 2 SnSe 3 (CTSe) thin films deposited by thermal evaporation from this powder on glass substrate at T s= 400 C were investigated. Powders and films were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM), to determine their microstructure, morphology, chemical compositions and root-mean-square (RMS) roughness. XRD analysis revealed that all samples crystallize in polycrystalline nature with cubic structure and lattice parameter a= 5.68 Å. The optical measurements were carried out in the [500-2500nm] wavelength range and were determined from spectral …
Résumé: The CuIn0.5Ga0.5Se2 (CIGS) nanocrystalline powders were prepared by mechanical alloying method. Effect of various milling times and higher milling speed on the structure of CIGS nanoparticles was investigated by X-ray diffraction measurements. The Rietveld method was used to refine the XRD data using the MAUD program. Refinement process reveals that the main phase of the CIGS powders milled for different milling times is of chalcopyrite structure. Milling time dependence of the unit-cell parameters and crystallite size has also been reported. The TEM observations demonstrated that the size of agglomerated CIGS powder is about 140 nm. The EDAX analysis of various grains of the milled powder shows that the compositions vary from one grain to another. However, the global composition was found slightly copper rich.