Physique

Nombre total de résultats : 258
Pertinence Titre A-Z Plus récents Plus anciens
10 25 50
Année de publication
et

Study of structural properties of thin films of TiO2 doped Ni obtained by Sol-gel method

H. Dehdouh, B. Toubal, H. Bensouyad, H. Sedrati, M. Brahimi, F. Abbas, and R. Bensaha  (2011)
Article de conférence

The objectives through this work, is the study of the structural properties of the thin films of titanium dioxide obtained by dip-coating. Holding in account the effect of nickel on these properties.The properties of the thin films of TiO2 strongly depend on the microstructures obtained. Those are modulated by the technique and the conditions of preparation, as well as by the heat treatments on the one hand [1]. And in other hand by the effect of impurities [2].In this work, we are interested in the study of the structural properties of the thin films of TiO2 un-doped and doped Ni obtained by sol-gel method. For that we study the evolution of the grains size, the crystalline structure with the temperature of treatment, the number of dipping and the concentration of doping 2% and 5% nickel. Our results show that the structure and the grains size of our layers change when one varies the temperature of treatment as well as the number of steeping and the concentration of nickel doping, more the nickel rate is large plus the structure is fine, this is led to the variation of the index of refraction, of the grains size, the gap, the transmittance and the temperature of crystallization. We used several techniques of investigation to follow the structural evolutions and their structural properties resulting from various heat treatments, various dipping and different Ni concentration: Differential calorimetric analysis (DSC), diffraction of the rays X (XRD), UV-visible Spectroscopy, scanning electronic microscopy (SEM). Voir les détails

Mots clés : sol-gel process, TiO2 doped Ni, Structural properties

Structural Characterization of TiO2 Thin Films on Aluminum Substrates Obtained by Sol-Gel Process

H. Dehdouh, R. Bensaha  (2013)
Article de conférence

In this work, TiO2 thin films were prepared by dip-coating Sol-Gel process on aluminum substrates. The deposition process allows having layers of good quality (homogeneity, adhesion). The layers thus prepared have undergone annealing at 550 °C for 1\2h and 2h and characterized by different techniques: Differential scanning calorimetric (DSC), X-ray diffraction (XRD), Raman spectroscopy and scanning electronic microscopy (SEM). The DSC curve shows an exothermic peak corresponding to the crystallization of TiO2. XRD and Raman results indicate that TiO2 layers deposited on aluminum crystallize in tetragonal anatase phases of TiO2 by annealing at 550 °C, the grain size depend on the annealing time. Then observing the cavities of TiO2 randomly formed on aluminum by SEM. Voir les détails

Mots clés : Aluminum substrate, TiO2Thin films, anatase

Correlation between structure and photoluminescence properties of thin films of TiO2 doped Er3+, obtained by the sol-gel process

Rabah BENSAHA;, Heider DEHDOUH, Manel BRAHIMI, Fouzia ABBAS, Hanene BENSOUYAD, hichem SEDRATI  (2013)
Article de conférence

In this work, we are interested to the study of the influence of structure on photoluminescence properties of Er3+ doped TiO2 thin films, dip-coated by the sol-gel method. TiO2 thin films and powders obtained are doped with different rates of Erbium (0.1, 0.5, 1, 3 at %) and have undergone an annealing at 450 ° C. Thin films and powders thus obtained were characterized by different techniques: differential scanning calorimetric (DSC), infrared spectroscopy FTIR, Raman spectroscopy and photoluminescence. (DSC) results show that the Erbium causes a shift of the transformation from amorphous TiO2 to anatase crystalline state to the low temperatures and the latter varies according to the percentage of erbium. While the FTIR shows strong absorption peaks around 438 cm-1 and 612 cm-1 corresponding respectively to the vibration Ti-O-Ti and Ti-O of TiO2. In contrast the Raman spectra show the presence of two phases’ anatase and brookite in the case of un-doped thin films and the disappearance of the brookite in those doped with Erbium and annealed at 450 °C. Finally, the photoluminescence curves show the green and red up-conversion emissions. Green emissions are positioned in the range of 520-570 nm (2H11 / 2, 4S3/2 4I15/2), and then for those of the red they are set in the range 640-690 nm (4F9/2, 4I15/2). We also note that the emission intensity of red and green gradually increased when the erbium rate increases. Voir les détails

Mots clés : TiO2 doped Er3+, sol-gel, photoluminescence properties

ETUDE DE L’INFLUENCE DE : Er3+ ET Alq3 SUR LES PROPRIETES STRUCTURALES ET OPTIQUES DES COUCHES MINCES DE TiO2

Heider DEHDOUH (En préparation)
Thèse de doctorat

Les semi-conducteurs transparents (OTC) sont des oxydes avec de de bons propriétés optiques, électriques et magnétiques, ils peuvent devenir « de type n » s’ils possèdent un excès d’électrons dans leur réseau, soit par des défauts de structure, ou par un dopage approprié selon l’application visée. Ce travail de thèse consiste à élaborer des couches minces de TiO2 dopées en différentes concentrations d’erbium et d’Alq3, nous avons opté pour le procédé sol gel grâce à ces faibles coûts, qualité des couches et la facilité de sa mise en œuvre. Dans ce travail nous nous sommes intéressés à l’étude les modifications dues aux dopants luminescents sur la matrice de TiO2 en termes de stœchiométrie, de porosité, cristallinité, la morphologie, l’indice de réfraction et l’absorbance des films. Les techniques de caractérisation adoptées sont : la microscopie électronique à balayage (MEB), la microscopie à force atomique (AFM), la diffraction des rayons X (DRX), spectroscopie Raman, l’ellipsométrie (EM), la spectrophotométrie UV- visible, la photoluminescence (PL), la VSM et la spectroscopie des lignes noires (m-lines). Nous envisagerons des applications tel que : la télécommunication optique, les guides d’ondes et les semi-conducteurs dilués. Voir les détails

Mots clés : TiO2, dopage Er3+, dopageAlq3, sol-gel, Propriétés structurales et optiques.

Structural modification and magnetic properties enhancement with Er3+, of sol-gel TiO2 thin films

DEHDOUH Heider, BENSAHA Rabah, ZERGOUG Mourad  (2016)
Article de conférence

Nano-crystalline un-doped and erbium doped TiO2 thin films were dip-coated on glass substrates by sol-gel method. The films were annealed at 450 °C during 1 hour. DSC results show that the crystallization effectuates at 339°C for un-doped TiO2, whereas for erbium doped TiO2 the crystallization occurs earlier with two separated exothermic. XRD diagrams illustrate that un-doped and erbium doped TiO2 crystallize in anatase phase only and indicate that the crystallite size decreases from 24 to 21 nm as a function of the increase in Er3+ content. This result is confirmed by Raman spectra. Moreover, the VSM results indicate, on one hand, a ferromagnetic behaviour of the un-doped TiO2. On the other hand, the incorporation of Erbium leads to an enhancement of the ferromagnetic behaviour. It is worthy to mention that the weak Er3+ doping (0.1 at.%) is the high ordered magnetically with highest saturation magnetization of 1.92 memu. Both elaborated TiO2 and Er:TiO2 films show good structural properties and have a diluted magnetic semiconductors structure. The films are promising for the possible applications in optoelectronic devices. Voir les détails

Mots clés : TiO2 doped Er3+, Structural properties, sol-gel, Magnetic Properties, oxygen vacancies.

Analysis of HNLS Solitons with Quintic Nonlinearity Using Semi Implicit Operator Splitting Padé Method

M. Smadi 1, D. Bahloul, S. Aziez, A. Sid, D. Debbache  (2008)
Publication

In this communication, we use the semi-implicit finite difference operator splitting Padé method to solve the higher-order nonlinear Schrödinger equation with higher order linear and nonlinear effects such as the third order dispersion (TOD), Kerr dispersion, stimulated Raman scattering and the quintic nonlinearity. The role of quintic nonlinearity on the propagation characteristics of optical solitons is investigated for standard fibers. This method is readily generalized for nonlinear management fibers it’s found that the quintic nonlinearity has no significant role on the propagation of single solitons. Voir les détails

Mots clés : Optical solitons, Padé method, quintic nonlinearity. HNLS equation

Semi-implicit operator splitting Padé method for vector HNLS solitons

Siham AZIEZ, Moussa Smadi, Derradji BAHLOUL  (2008)
Publication

We use in this paper the semi-implicit finite difference operator splitting Padé (OSPD) method for solving the coupled higher-order nonlinear Schrödinger equation, which describes the propagation of vector solitons in optical fibers. This method having a fourth order accuracy in space shows good stability and efficiency for the coupled HNLS equations describing vector solitons. We have tested this method for analyzing the behavior of optical pulses in birefringent fibers verifying that the third order dispersion TOD has different effects on the two polarizations and the asymmetric oscillation is significant only in one polarization. Voir les détails

Mots clés : Birefringence, vector solitons, optical fibers, Operator Splitting Padé Method, coupled higher-order nonlinear Schrodinger equation, third order dispersion.

PROPAGATION OF TRAIN OF CHIRPED VECTOR SOLITONS IN BIREFRINGENT OPTICAL FIBERS WITH VARIABLE COEFFICIENTS

Siham AZIEZ, Derradji BAHLOUL  (2014)
Article de conférence

A propagation of train of chirped vector solitons in birefringent optical fibers with variable coefficients is studied numerically using the compact split step Padé scheme (CSSPS). A negative chirp makes the managed chirped vector soliton broadening, while; a positive chirp leads to a soliton compression. The effect of the chirp on the vector soliton temporal width of an amplification system (σ> 0) is greater than that in a loss system (σ< 0). The evolution of train of managed vector solitons is submitted not only to the effect of the chirp, but also to the interaction between the adjacent vector solitons. Voir les détails

Mots clés : Train of vector soliton, chirped soliton, optical fibers, compact split step Padé scheme, coupled higher-order nonlinear Schrodinger equations with variable coefficients, temporal waveform.

Semi-implicit operator splitting Padé method for vector HNLS solitons

Siham AZIEZ, Moussa Smadi, Derradji BAHLOUL  (2008)
Article de conférence

We use in this paper the semi-implicit finite difference operator splitting Padé (OSPD) method for solving the coupled higher-order nonlinear Schrödinger equation, which describes the propagation of vector solitons in optical fibers. This method having a fourth order accuracy in space shows good stability and efficiency for the coupled HNLS equations describing vector solitons. We have tested this method for analyzing the behavior of optical pulses in birefringent fibers verifying that the third order dispersion TOD Voir les détails

Mots clés : Birefringence, vector solitons, optical fibers, Operator Splitting Padé Method, coupled higher-order nonlinear Schrodinger equation, third order dispersion.

Propagation characteristics of Chirped Vector Soliton in optical fibers with variable coefficients

Siham AZIEZ, Derradji BAHLOUL  (2013)
Article de conférence

In this work we study the propagation characteristics of chirped vector solitons in optical fiber systems with variable coefficients by using the compact split step Padé scheme (CSSPS). The numerical simulations show that the chirped managed vector soliton with different perturbations maintains its characteristics during propagation along the polarization maintaining optical fiber. Voir les détails

Mots clés : vector soliton, chirped soliton, optical fibers, compact split step Padé scheme, coupled higher-order nonlinear Schrodinger equations, temporal waveform.