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Zgaren I.,University of Carthage | Balti J.,University of Carthage | Jaziri S.,University of Carthage | Jaziri S.,Laboratoire Of Physique Of La Matire Condensee
Solid State Communications

Auger processes are investigated for CdS/ZnS core-shell quantum dots. Auger recombination (AR) lifetime and electron relaxation inside the core are computed. Using the effective-mass theory and by solving a three-dimension Schrödinger equation we predict the dependence of Auger relaxation on size of core-shell nanocrystals. We considered in this work different AR processes: the excited electron (EE), excited hole (EH), multiexciton AR type. Likewise, Auger multiexciton recombination rates are predicted for biexciton. Our results show that biexciton AR type is more efficient than the other AR process (excited electron (EE) and excited hole (EH)). We also found that electron Auger relaxation P→S is very efficient in core-shell nanostructures. © 2011 Elsevier Ltd. All rights reserved. Source

Allouche N.K.,Laboratoire Of Physique Of La Matire Condensee | Jebbari N.,Laboratoire Of Physique Of La Matire Condensee | Guasch C.,Montpellier University | Turki N.K.,Laboratoire Of Physique Of La Matire Condensee
Journal of Alloys and Compounds

The structural and optical properties of the CuInS2 semiconductor thin films doped with aluminum ([Al]/[In] = 1 and 2) are reported. Films are deposited using the spray pyrolysis technique on various substrates: glass, In2S3/glass, ZnO/glass, as well as SnO 2/glass, In2S3 and ZnO are used as optical windows in photovoltaic system, CuInS2 as the absorber material and SnO2 as ohmic contact. In2S3, ZnO and SnO 2 are grown by spray pyrolysis. During CuInS2 thin layer deposition, the substrate temperature is 340°C. The deposition run lasts for 5 min. X-ray diffraction is used to characterize CuInS2 film cristallinity. The effect of aluminum inclusions as well as of the substrate material on the CuInS2 film is investigated. The optical absorption coefficient α for the Al-doped CuInS2 compounds is obtained from reflection and transmission spectra. It is in the range of [3.694.37]×10 6cm-1 ([9.5512.31]×106 cm-1, respectively) for 1 aluminum content in the spray solution (2, respectively). The direct band gap value is in the order of 1.44 eV for the 1Al-doped CuInS2 thin layers and 1.48 eV for 2 Al content. © 2010 Elsevier B.V. All rights reserved. Source

Tabet J.,University of Lyon | Tabet J.,University Claude Bernard Lyon 1 | Eden S.,University of Lyon | Eden S.,University Claude Bernard Lyon 1 | And 11 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

Vapor jets of DNA and RNA bases (adenine, cytosine, thymine, and uracil) from an oven with a capillary exit have been studied in the intermediate regime between molecular and viscous flow corresponding to Knudsen numbers in the range 0.1 < Kn < 10. The temperature control method ensured stationary flow. Assuming the Knudsen hypothesis, the pressure of sublimated molecules in the oven was determined as a function of temperature and the transmission probability of the capillary (Clausing factor). Thus it was possible to relate the oven temperature and pressure to the total flux through the capillary, determined by measuring the total mass of DNA/RNA base molecules condensed on a cold surface intersecting the jet. The angular distribution of molecules in the jet has been also studied experimentally using an optical interference method. The measured profiles are in good agreement with Troïtskii's [Sov. Phys. JETP 7 (1962) 353] analytical law for (cos θ)3/2 angular dependence in the intermediate regime with error functions associated with the mean free path between intermolecular collisions. © 2010 Elsevier B.V. All rights reserved. Source

Kamoun Allouche N.,Laboratoire Of Physique Of La Matire Condensee | Kamoun Allouche N.,Montpellier University | Ben Nasr T.,Laboratoire Of Physique Of La Matire Condensee | Turki Kamoun N.,Laboratoire Of Physique Of La Matire Condensee | Guasch C.,Montpellier University
Materials Chemistry and Physics

Zinc sulphide multilayer films are prepared by chemical bath deposition from different host solutions. X-ray diffraction and scanning electron microscopy are used to characterize the structural properties of the films. The surface composition of the films is studied by Auger electrons spectroscopy, and optical properties are studied by spectrophotometric measurements. X-ray diffraction patterns reveal distinct single crystalline phase with preferential orientation along the (1 1 1) plane of the zinc blende structure for the ZnS multilayer. The spacing between (1 1 1) planes of ZnS is well matched to the spacing between (1 1 2) planes of the chalcopyrite CuInS2. After heat treatment all films show a near stoichiometric surface composition as indicated in their AES data. UV-vis measurements show that ZnS multilayer films prepared from the zinc sulphate solution have more than 70% transmission in the wavelengths above 350 nm and an optical band gap of about 3.76 eV. © 2010 Elsevier B.V. All rights reserved. Source

Allouche N.K.,Laboratoire Of Physique Of La Matire Condensee | Allouche N.K.,Montpellier University | Ben Nasr T.,Laboratoire Of Physique Of La Matire Condensee | Guasch C.,Montpellier University | Kamoun Turki N.,Laboratoire Of Physique Of La Matire Condensee
Comptes Rendus Chimie

Semiconducting copper sulphide (Cu2S) thin films have been deposited on various substrates (SnO2:F/glass, glass) by the simple and economical chemical bath deposition technique. The depositions were carried out during a deposition time of about 32.5 min in the pH range of 9.4 to 11. The synthesized Cu2S thin films were characterized using various techniques without any annealing treatment. X-ray diffraction study shows that Cu2S films exhibit the best crystallinity for pH = 10.2. For this pH value, Auger electron spectroscopy investigations show that Cu2S thin films grown on an SnO2/glass substrate exhibit stochiometric composition with [Cu]/[S] concentrations ratio equal to 2.02. Using the Kelvin method, the work function difference (material- probe) for the Cu2S films deposited on SnO2/glass substrates at the optimum pH value was found to be equal to 145 meV. Hall measurements confirm the p-type electrical conductivity of the obtained films. The electrical resistivity was of the order of 3.85 × 10-4 Ω-cm. The transmission and reflection coefficients vary in the range of [35-60] % and [5-15] % respectively, in the visible range, and the band gap energy is about 2.37 eV. © 2010 Académie des sciences. Source

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