Physique

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SnS Thin Films Prepared by Chemical Spray Pyrolysis method

M. MESSAOUDI, A. Derrouiche, M. Maiza, M.S. Aida, N. Attaf and H. Nezzari  (2017)
Article de conférence

Tin sulfide (SnS) is interesting semiconductor that found application is several fields such as photovoltaic and gas sensor due to its interesting optical and electrical properties. In the present study, chemical spray pyrolysis deposition (CSP) was used to deposit tin sulfide (SnS) thin films onto glass substrates at 350°C. The starting solutions were prepared by the dilution of SnCl2 and thiourea in distilled water. The structural, optical and electrical, properties of the films were determined using X-ray diffraction, UV visible transmittance and Hall Effect measurements respectively. The influences of flow rate (10, 15 and 20 ml/h) in the structural, optical and electrical properties were determined. The XRD data confirms that the films prepared at low flow rate are a mixture of SnS and Sn2S3 phases. However, when the flow rate is increase; structures of the films are amorphous. From the UV-visible transmittance in the visible range we noticed that films optical band gap value ranged from 1.2 to 1.5 eV. The Hall Effect measurements indicate that SnS thin film exhibits p-type conduction with a conductivity decrease by two orders from 5.15x10-3 to 5.8x10-7 (?.cm)-1. Voir les détails

Mots clés : tin sulfide; solar cell; UV-visible, spary pyrolysis.

Electrical Characteristics of SnS /ZnS Heterojunction

M. MESSAOUDI, L. Beddek, M. Maiza M.S. Aida, N.Attaf and H. Nezzari  (2017)
Article de conférence

Thin sulphide (SnS) is a promising candidate for a low cost, no toxic solar cells absorber layer. In this paper thin films of SnS were prepared by spray pyrolysis onto glass and ZnS/FTO coated glass substrates at different substrate temperatures in the range 250-400°C. SnS were characterized with X-rays diffraction and scanning electron microscopy and UV visible transmittance. The electrical properties of SnS/ZnS heterojunctions were determined using recording their current-voltage I(V) and capacitance-voltage (C-V) characteristics at ambient and at different measurement temperatures from 28-94°C. The results analysis indicate that the saturation current varied from 0.68 to 2.8 µA and series resistance from 191 to 800 ? , The structures ideality factor is ranged from 1.37 to 2.7. The diffusion potential (Vd) was determined by the intercept of extrapolation of 1/C2-V curve to the abscise axis (V=0) we found Vd values ranged from 0.67 to 1.2 V. Voir les détails

Mots clés : Tin sulfide; thin films; solar cell; spray pyrolysis; SnS/CdS Heterojuction.

Structural, Optical and Electrical Properties of PbS Thin Films Deposited by CBD at Different Bath pH

L. Beddek, M. MESSAOUDI, S. Guitouni, N. Attaf, M.S. Aida  (2015)
Publication

PbS thin films were grown on glass substrates by chemical bath deposition (CBD). The precursor aqueous bath contained 1mole of lead nitrate, 1mole of Thiourea and complexing agents (triethanolamine (TEA) and NaOH). Bath temperature and deposition time were fixed at 60°C and 3 hours, respectively. However, the PH of bath was varied from 10.5 to 12.5. Structural properties of the deposited films were characterized by X-ray diffraction and Raman spectroscopy. The preferred direction was revealed to be along (111) and the PbS crystal structure was confirmed. Strains and grains sizes were also calculated. Optical studies showed that films thicknesses do not exceed 600nm. Energy band gap values of films decreases with increase in pH and reached a value ~ 0.4eV at pH equal 12.5. The small value of the energy band gap makes PbS one of the most interesting candidate for solar energy conversion near the infrared ray Voir les détails

Mots clés : CBD, PbS, pH, Thin films, X-ray diffraction

The effect of copper concentration on CdS/CZTSheterojunction properties

S.Guitouni, M.Khammar, M.Messaoudi, N.Attaf, M.S.Aida  (2015)
Publication

Cu2ZnSnS4 (CZTS) / CdS heterojunctions have been prepared by a successive deposition of CZTS and CdS thin films on glass substrates by spray pyrolysis and chemical bath deposition techniques respectively. The concentration of cupric chloride in the starting solution has been varied in order to investigate its influence on device properties. The realized CZTS/CdS heterojunctions were characterized by recording their IV characteristics at ambient and at different temperatures. The current-voltage (IV) characteristics of the different heterostructures exhibit a rectifying behavior with a good ideality factor ranged from 1.5 to 2.7. From these IV characteristics we have deduced the saturation current series resistance and barrier height of the devices. We found that these quantities vary from 0.22 to 1.68µA for the saturation current and from 300 to 2500 for the series resistance. We have deduced also that the potential barrier was found between 0.3 and 1.31eV. From these results we inferred that the realized structures are suitable for their applications as solar cells. Voir les détails

Mots clés : CZTS; heterojunction; spray pyrolysis; solar cells;IV

Étude des propriétés structurales électroniques et thermodynamiques de l’alliage quaternaireZn1-xMgxSeyTe1-y

Latifa TAIRI (2018)
Thèse de doctorat

First-principles calculations are performed to study the structural, electronic and thermodynamic properties of Zn1-xMgxSeyTe1-yalloys using the full potential-linearized augmented plane wave method (FP-LAPW) within the density functional theory (DFT). In this approach the Perdew-Burke-Ernzerhorf generalized gradient approximation (PBE-GGA) was used for the exchange-correlation potential. Moreover, the modified Becke Johnson approximation (mBJ) was also used for band structure calculations. First for the MgX binary compoundsvarious phases were considered in order to confirm the most stable one and to predict the transition pressure between different phases. The lattice constant for theternary alloys exhibits a small deviation from the Vegard's law. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. The bowing of the fundamental gap versus composition predicted by our calculations is in good agreement with available theoretical data. In addition, we have studied the thermal properties of these alloys using the Debye model implemented in Gibbs program. Finally, the energy band gap of Zn1-xMgxSeyTe1-y quaternary alloys lattice matched to InAsandZnTesubstrats was investigated. To our knowledge this is the first quantitative theoretical investigation on Zn1-xMgxSeyTe1-y quaternary alloys and still awaits experimental confirmations. Voir les détails

Mots clés : Zn1-xMgxSeyTe1-y Quaternary alloys, Functional density (DFT), Approximation of the generalized gradient (PBE-GGA), mBJ approximation, InAs and ZnTe substrates

Sulfide precursor concentration and lead source effect on PbS thin flms properties

L. Beddek, M. MESSAOUDI, N. Attaf, M.S. Aida, J. Bougdira  (2016)
Publication

Lead sul?de (PbS) thin ?lms were synthesized using chemical bath deposition (CBD). Bath solutions are formed of various concentrations of thiourea, sul?de source, ranged from 0.6 to 1.2 M and two different salts as Pb source (lead acetate and lead nitrate). From the growth mechanism, we inferred that PbS is formed through the ion by ion process when using acetate lead source, while, using nitrate source yields to ?lms growth through the complex decomposition process. Due to the difference in the involved growth process, lead acetate produces ?lms with larger crystallite size (from 4 to 16 nm), smooth and dense ?lms. However, lead nitrate produces rough ?lms with smaller crystallite size (from 1 to 4 nm).Increasing the thiourea concentration results in crystallinity improvement when using lead acetate and, oppositely, in crystallinity degradation when using lead nitrate. Due to the quantum effect caused by the small crystallite sizes, the ?lms optical gap is varied from 0.5 to 0.9 eV. Voir les détails

Mots clés : Thin ?lms Lead sul?de Chemical bath deposition

Gap states density measurement in copper oxide thin films

M. Lamri Zeggar, M. MESSAOUDI, M.S. Aida n, N. Attaf  (2016)
Publication

The density of gap states near the Fermi level have been measured in copper oxide (CuO) thin ?lms deposited by spray pyrolysis technique. The measurement method is based on the exploitation of the current–voltage characteristics of the space charge limited current (SCLC) measured in a sandwich Au/CuO/Au structure. The measured gap states density is equal to 1.5x1014cm-3 and 2.0 x1014 ev-1 respectively in films prepared at 300 and 400 °C substrate temperature, while the defect position are located at 16 and 20meV above Fermi level. The carriers mobility and concentration are also determined from SCLC, the obtained results are in good agreement with Hall effect measurement ones. Voir les détails

Mots clés : Density of states Thin ?lms Spray pyrolysis Solar cells

Contribution à la caractérisation et synthèse de pigment de peinture à base de calamine. Evaluation de la qualité et analyse des incertitudes sur les propriétés.

Mohamed Tayeb ABEDGHARS (2018)
Thèse de doctorat

The iron oxide pigment consists of 53.18% iron with a siliceous matrix. The calamine itself contains 73.83% iron. The density of the pigment and calamine is respectively ρ=3.0665 g/cm3 and ρ=5.4203 g/cm3. The pigment is of oolitic structure. Calamine has a homogeneous structure of the three iron oxides. The grain size of the compounds is between 0.6 and 40 μm with a D50 of less than 8 μm. Their specific surfaces are 1.6 and 1.5 m2/g. The calamine has an ability to keep its magnetization unlike the pigment which has a low magnetization.Simultaneous Thermal analysis shows a mass increase of 3.602% between 400 and 1000 °C for calamine and exotherm equal to 1.128 W/g. For the iron pigment, this analysis shows an overall mass loss equal to 11.05% accompanied by heat absorption equal to 1.926 W/g. For the iron pigment, this analysis shows an overall mass loss equal to 11.05% accompanied by a heat absorption equal to 1.926 W/g. Concerning the mixtures with 5, 10, 15, 20, 25 and 35% of calamine, we find a decrease of the loss of mass. The flow of heat takes a polynomial pace increasing.The SEM observations show a homogeneous structure of the calamine composed of grains of iron oxides of different sizes ranging from 1 μm to 10 μm and aggregates of small particles. As for the iron oxide pigment, it is composed of aggregates of grains more or less rounded formed of oxides of iron and gangue. The EDS analysis shows a dominance of the iron element for both materials. The optical measurement spectra show that the three compounds do not absorb any visible radiation and absorb significant fluxes in the near UV. They reflect all the incident radiation in the visible but reflect very little near UV radiation. The X-ray diffraction of calamine shows that the crystalline phases of its constitution are mixtures of wustite, magnetite and hematite. As for the iron oxide pigment, it is composed of the following crystalline phases: goethite, hematite, fayalite, silica, phosphorus pentoxide, and hausmannite. The prediction model that we developed deals with the modeling of mass loss and thermal behavior as a function of the mixing rate by a combined model of "neuronal network NN" and the MTCS simulation, which allowed us to calculate this mass loss and the corresponding energy variation. The model based on the neural network approach, by its high precision, offers us a reduced range of uncertainties compared to the linear model. Voir les détails

Mots clés : Pigment iron, scale (calamine), iron oxides, grinding, Simultaneous thermal analysis, X-ray diffraction, spectrophotometry.

Deposition of tin(II) sulfide thin films by ultrasonic spraypyrolysis: Evidence of sulfur exo-diffusion

M. MESSAOUDI, M.S. Aida, N. Attaf, Bezzi, J. Bougdira et G.Medjahdi  (2014)
Publication

Tin Sulfide (SnS) thin films were deposited by ultrasonic spray pyrolysis technique, on glass substrate heated at 280 °C, with different deposition times. The used precursor SnCl2 and thiourea are dissolved in methanol. X-ray diffraction (XRD) analysis indicates that films are mainly composed with orthorhombic SnS phase at low deposition time. With increasing deposition time, the hexagonal SnS2 phases become dominant. SnO2 and metallic Sn phases have been detected with increasing deposition time. Scanning electron microscopy (SEM) observations reveal that films surfaces are rough with the presence of bubbles due to S2 gas exo-diffusion from the bulk during film growth. A model of S gas formation is presented. Voir les détails

Mots clés : Tin Sulfide Thin films Spray pyrolysis

Elaboration et Caractérisation de Couches Minces SnS

Meriem Messaoudi (2016)
Thèse de doctorat

The present work deals with the deposition and characterization of tin sulfide thin film for the photovoltaic application. Films were synthesized by spray pyrolysis technique due to its simplicity and low cost. The starting solutions, were composed of tin chloride (SnCl2) and thiourea (CS (NH2)2) as a source of Sn and S respectively. Sets of films were prepared by varying four deposition parameters namely deposition time, solvent, spray flow rate and substrate temperature. After preparation films were subjected of various characterizations: structural, morphological, optical and electrical. The structural characterization indicates that SnS films have an orthorhombic structure with a preferential orientation (111) when prepared at low flow rate, high substrate temperature and distilled water as solvent. However, secondary phases such as Sn2S3, SnO2 and Sn metal are detected in films prepared with methanol as solvent. SEM results indicate the presence of bubbles and craters on the surface of films prepared with methanol, this is due to the sulfur exo-diffusion in form gas of S2. The optical studies show that SnS film has a large absorption coefficient in the visible range; the optical gap value is in the order of 1.3eV suggesting that SnS thin films can be a good candidate for thin films solar cells. The electrical measurements indicate that films prepared at high substrate temperature have a large conductivity. The I-V characterization of the two realized SnS/CdS and SnS/ZnS heterostructures reveal a typical behavior of a heterojunction with a good ideality factor; their characteristics are improved after thermal annealing. The Au/SnS/CdS/FTO heterojunction exhibits a photovoltaic effect but with a poor efficiency. Voir les détails

Mots clés : Tin sulfide, Spray pyrolysis, Thin films, solar cells.