Time filter
Source Type

Meziani S.,CRTSE | Moussi A.,CRTSE | Mahiou L.,CRTSE | Outemzabet R.,University of Science and Technology Houari Boumediene
Materials Science- Poland | Year: 2016

Hydrogen, amorphous silicon nitride (SiNx:H abbreviated SiNx) films were grown on multicrystalline silicon (mc-Si) substrate by plasma enhanced chemical vapour deposition (PECVD) in parallel configuration using NH3/SiH4 gas mixtures. The mc-Si wafers were taken from the same column of Si cast ingot. After the deposition process, the layers were oxidized (thermal oxidation) in dry oxygen ambient environment at 950 °C to get oxide/nitride (ON) structure. Secondary ion mass spectroscopy (SIMS), Rutherford backscattering spectroscopy (RBS), Auger electron spectroscopy (AES) and energy dispersive X-ray analysis (EDX) were employed for analyzing quantitatively the chemical composition and stoichiometry in the oxide-nitride stacked films. The effect of annealing temperature on the chemical composition of ON structure has been investigated. Some species, O, N, Si were redistributed in this structure during the thermal oxidation of SiNx. Indeed, oxygen diffused to the nitride layer into Si2O2N during dry oxidation. © Wroclaw University of Technology 2016.

Aoudj S.,CRTSE | Aoudj S.,University Blida1 | Khelifa A.,University Blida1 | Drouiche N.,CRTSE | And 2 more authors.
Chemical Engineering Journal | Year: 2015

A combined two-step EC-EF process was designed to simultaneously remove Cr(VI) and fluoride from pretreated acidic semiconductor effluents. The EC step comprises integrated reduction of chromium(VI) with coagulation of fluoride, while in the EF step, clarification takes place. In EC step a hybrid Fe-Al was used as sacrificial anode and stainless steel as cathode. Initially, the effect of anodic material on EC-EF efficiency was investigated and it was found that the combination 2Fe-2Al gives the optimum results. Most of Cr(VI) removal was ascribed to iron plates, while fluoride removal was mainly ascribed to aluminum plates. Presence of coagulants enabled the removal of suspended solids which are present in initial solution. Effects of initial pH, current intensity, anions nature, chloride concentration and initial concentration on EC-EF process efficiency using hybrid anode were studied. The behavior of the hybrid anode depends on both iron and aluminum individual properties toward pollutants. Under optimum conditions, residual concentrations of Cr(VI) and fluoride and turbidity after EC-EF were found under national discharge standards. © 2014 Elsevier B.V.

Bozetine I.,CRTSE | Bozetine I.,University of Science and Technology Houari Boumediene | Boukennous Y.,CRTSE | Trari M.,University of Science and Technology Houari Boumediene | Moudir N.,CRTSE
Energy Procedia | Year: 2013

Orthophosphate silver with superior quality and quantum size effect is elaborated by precipitation from phosphate precursors. The powders were investigated by X-ray diffraction, SEM-EDS, FTIR, thermal analysis, and diffuse reflectance. Spherical like Ag3PO4 particles with size between 0.8 to 10 μm were obtained. The powders crystallize in a cubic symmetry and the smaller crystallites are obtained with Na2HPO 4. The optical gap, determined from the diffuse reflectance spectra through the Kubelka-Munk function, lies between 2.05 and 2.30 eV. © 2013 The Authors.

Meziani S.,CRTSE | Moussi A.,CRTSE | Mahiou L.,CRTSE | Outemzabet R.,University of Science and Technology Houari Boumediene
Proceedings of 2015 IEEE International Renewable and Sustainable Energy Conference, IRSEC 2015 | Year: 2015

This work is a contribution towards the understanding of the optical and structural properties of graded refractive index layers SiN/SiO2 to lead to antireflective coating and efficient passivation of multicristalline silicon wafer. We investigate the influence of the thermal annealing on optical properties and chemical bonding of double anti-reflection coating (DARC) SiNx/SiO2 dielectric stack structure. Hydrogenated amorphous silicon nitride (SiNx:H) coating is prepared by plasma enhanced chemical vapor deposition (PECVD) using a gas mixture of NH3/SiH4 on multicristalline silicon wafer substrates. We have grown silicon oxide (SiO2) thin films on the top of SiNx by using thermal oxidation methods in the aim of creating graded-index refractive coating. The effects of annealing temperatures (500 to 1000°C) under nitrogen atmosphere are investigated. Based on Fourier Transform Infra-Red analysis (FTIR), it was observed that after annealing temperature, IR absorption of Si-N bonding decreased, while the integral intensity of Si-O bonding increased. This is due to a partial conversion of the phases Si-N and Si-O to Si-O-N phase. On the other hand, the change on the weighted reflectance in the range of 400-1100 nm (UV-Vis-IR) is observed. We have found a decrease of minimum reflectivity R= 0.77% (1= 690 nm) and weighted reflectance Rw = 7.71%. Thus, the N2 annealing method might have the tremendous potential for antireflective coating and surface passivation of solar cells applications. © 2015 IEEE.

Chebout K.,CRTSE | Chebout K.,University of Boumerdès | Iratni A.,University of Boumerdès | Bouremana A.,CRTSE | And 3 more authors.
Solid State Ionics | Year: 2013

A gas sensing device based on Vanadium oxide (V2O 5)/Porous Si (PS)/Si structure has been used to detect ethanol vapor at different concentrations. The V2O5 thin films were deposited on porous silicon by sol-gel (Dip-coating) technique. The Vanadium oxide has been produced from vanadium alcoxide precursor. The capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of Al/V2O5/PS/Si structure have been measured in the range from 1 Hz to 10 MHz frequency at room temperature in the presence of ethanol vapor. It is found that both C-V and G/ω-V of the capacitor are very sensitive to frequency and the sensor characteristics are modified in the presence of the gas. Conductance and capacitance measurements at low frequencies indicate the presence of interface states which can follow an alternating current (ac) signal that contributes to excess capacitance and conductance. © 2013 Elsevier B.V.

PubMed | Ecole Polytechnique - Palaiseau, CRTSE and University of Boumerdès
Type: Journal Article | Journal: Nanoscale research letters | Year: 2014

The formation of macropores in silicon during electrochemical etching processes has attracted much interest. Experimental evidences indicate that charge transport in silicon and in the electrolyte should realistically be taken into account in order to be able to describe the macropore morphology. However, up to now, none of the existing models has the requested degree of sophistication to reach such a goal. Therefore, we have undertaken the development of a mathematical model (phase-field model) to describe the motion and shape of the silicon/electrolyte interface during anodic dissolution. It is formulated in terms of the fundamental expression for the electrochemical potential and contains terms which describe the process of silicon dissolution during electrochemical attack in a hydrofluoric acid (HF) solution. It should allow us to explore the influence of the physical parameters on the etching process and to obtain the spatial profiles across the interface of various quantities of interest, such as the hole concentration, the current density, or the electrostatic potential. As a first step, we find that this model correctly describes the space charge region formed at the silicon side of the interface.

Bouhafs D.,CRTSE | Khelifati N.,CRTSE | Kouhlane Y.,CRTSE
Acta Physica Polonica A | Year: 2016

We have investigated in this work the effect of the temperature profile during homogeneous phosphorous diffusion gettering (PDG) on multicrystalline (mc-Si) silicon p-type wafers destined for photovoltaic solar cells. Temperatures were varied from 800 °C to 950 °C with time cycle of 90 minutes. Phosphorous profile of n+p junction was measured by secondary ion mass spectroscopy (SIMS) from 0.45 μm to 2.4 μm. Chromium concentration profile measured on the same samples by SIMS shows a high accumulated concentration of Cr atoms in the gettering layer at 900 °C and 950 °C, compared to samples obtained at 800 °C and 850 °C. The effective lifetime (Teff) of minority charge carriers characterized by quasi-steady state photoconductance (QSSPC) is in correlation with these results. From the QSSPC measurements we have observed an amelioration of Teff from 7 μs before PDG to 26 μs in the samples after PDG, processed at 900 °C. This indicates the extraction of a non-negligible concentration (5 × 1014 cm-3 to 5 × 1015 cm-3) of Cr from the bulk to the surface gettering layer, as observed in the chromium SIMS profiles. A light degradation of Teff (18 μs) is observed in the samples treated at 950 °C due probably to a partial dissolution of the metallic precipitates, especially at the grain boundaries and in the dislocations vicinity. The related TCr-Impurity lifetime value of about 8.5 μs is extracted, which is the result of interstitial Cri or CriBs pairs, proving their strongest recombination activity in silicon.

Moudir N.,Blida University | Boukennous Y.,CRTSE | Moulai-Mostefa N.,Blida University | Moulai-Mostefa N.,Dr. Yahia Fares University Center of Médéa | And 5 more authors.
Energy Procedia | Year: 2013

The preparation of fine silver particles is getting great attention due to their applications in electrical fields such as the fabrication of conductive pastes used in solar cell metallization. This study deals with the preparation of silver powders by a chemical reduction method using silver nitrate as a starting material, and either sodium or ammonium hydroxides as reactants, and formaldehyde as a reducing agent. The effects of ratio change between the silver nitrate and the base concentrations, on the characteristics of the silver micro particles, were examined. The physicochemical properties of the powders were evaluated using XRD, SEM, and granulometry. It was shown that the particle size and shape of the powder depend on the molar ratio of silver nitrate to base and, on the base nature. © 2013 The Authors.

Moudir N.,Blida University | Moulai-Mostefa N.,Blida University | Moulai-Mostefa N.,Dr. Yahia Fares University Center of Médéa | Boukennous Y.,CRTSE
Particulate Science and Technology | Year: 2015

In this study we report the preparation and characterization of fine silver microparticles by simple chemical reduction of silver nitrate using two types of bases and poly(N-vinylpyrrolidone) as protective agent. The influence of silver nitrate concentration and the nature and concentration of bases, on the properties of the silver microparticles was investigated. The structural characteristics of microparticles were determined using X-ray diffraction, scanning electron microscopy, and particle distribution analysis. It was noticed that the structure and the shape of silver microparticles depend on the base nature and the concentration of silver nitrate added to the base. It was also noted the absence of agglomerates in the powder prepared with PVP. This polymer not only serves as both coordinating agent and stabilizing one, but also plays an important role in controlling the size and shape of metal particles. © 2015 Taylor and Francis Group, LLC.

Kaci S.,CRTSE | Keffous A.,CRTSE | Hakoum S.,CRTSE | Mansri A.,CRTSE
Vacuum | Year: 2015

In the present study, we have carried out the adsorption effect of H2 on lead sulfide nanocrystalline thin films based gas sensors by measuring the variation of their current-voltage characteristics (I-V). The PbS thin films were synthesized by modified polyol process on amorphous a-SiC and p-Si(100) substrates in different chemical bath deposition. The obtained thin films were examined by Scanning Electron Microscopy (SEM) and Rutherford backscattering spectrometry (RBS) to get the general view of the product formed such as morphology and elemental composition. The films conductivity was n-type. We have obtained high density of uniform PbS nanocrystalline thin films. Upon exposure to gaseous molecules, the current at forward bias of nc-PbS decreased. The mechanism of gas sensing procedure was discussed. These sensors are highly sensitive with fast response to H2 gas. Our results have shown that nc-PbS thin films have potential to be a good H2 gas sensor at room temperature. © 2015 Elsevier Ltd. All rights reserved.

Loading CRTSE collaborators
Loading CRTSE collaborators