Contribution à l'étude de l'interaction phonon MOU-PIC central au voisinage des transitions de phase de KNbO3 et AgNbO3

Not availableRappel de la technique de la diffusion Raman puis de la théorie dynamique des transitions de phase concernant les notions de mode MOU et de PIC central. Description des propriétés de KNbO3. Présentation des résultats expérimentaux à température ambiante: 1) effet de la polarisation ; 2) caractère monodomaine de l'échantillon KNbO3. Evolution en température du mode MOU et du PIC central. Comparaison des résultats avec ceux d'autres techniques. Description du mécanisme des transitions de phase successives présentes par KNbO3. Présentation des résultats expérimentaux et calculs obtenus pour un cristal de AgNbO

The optical parameters of CuInS2 thin films deposited by spray pyrolysis method for photovoltaic applications

International audienceIn this work, CuInS2 (CIS) thin films were prepared by spray pyrolysis method, and optical properties were investigated. CuInS2 in the form of films is prepared at different deposition conditions by a simple and economical spray pyrolysis method. Optical constants such as band gap Eg, extinction coefficient k, refractive index n, and dielectric constants e1 and e2 were determined from the measured transmittance and absorption spectra in the wavelength range between 550-850 nm. Furthermore, the optical band gap values were calculated by the Tauc model. The absorption spectra of the films showed that this compound is a direct band gap material. The major result of this study is optical properties of CuInS2. © 2015 IEEE

Characteristics of CuInS2 thin films synthesizes by chemical spray pyrolysis

International audienceCuInS2 multi-component semiconductors thin films were prepared by chemical spray pyrolysis at different deposition conditions. The structural, optical, and electrical properties of the films were investigated. Samples were characterized using Raman spectroscopy, spectrophotometric and the 4-point probe method. Raman spectra indicate that the sprayed thin films are grown only with CH-ordering. Optical analysis by means of transmittance T(λ) and absorption A(λ) measurements in the wavelength range between 550 and 850 nm allow us to determine the direct band gap energy. Resistivity studies of the samples revealed that HK-S1 was less resistive than the other samples

Determination of the optimal conditions for the deposition of Cadmium sulfide thin films by chemical bath deposition using Taguchi method

International audienceThin films of Cadmium sulfide (CdS) is one of the promising semiconductor materials which can be used as a tampon materials deposited by chemical bath deposition (CBD) in thin film solar cells thanks to its tunable direct band gap energy, large transmission coefficient and cost effective. The role of the CdS layer is still debated within the scientific community, but the material efficiency obtained with this fine n-type semiconductor layer is very high. It could protect the damage associated with the following spray deposits of defects in the surface of the absorber or adapt the width of the energy band gap between the absorber (∼1.2 (eV)) and the window layer (∼3.3 (eV)). The aim of this present study is to investigate the influence of deposition parameters of CdS thin films using the L9 orthogonal array of the Taguchi's design of experiments (DOE) elaborated by CBD method on ordinary glass substrate. The Taguchi design was used to evaluate the effects of four deposition parameters called factors namely the ratios [Cd]/[S], time of deposition, Ammonia concentration [NH4Cl] and volume ratio V(H2O)/V(NH3) on optical properties of elaborated films. The identification of the most influent factor of the deposition process on the band gap energy of elaborated films is also done by employing the analysis of variance (ANOVA). The Taguchi analysis employed in the present investigation led to optimize process parameters for the most optimal deposition conditions. Under the optimized configuration, the CdS films showed optimal gap energy of 2.42 (eV) [1]. The Taguchi analysis employed in the present investigation led to optimize process parameters for the most optimal deposition conditions. © 2015 IEEE

Effect of different S/In ratio of In2S3 films prepared by chemical spray pyrolysis method

International audienceIn2S3 thin films were prepared using chemical spray pyrolysis technique. An aqueous solution of InCl3 and CS(NH2)2 was sprayed on to glass substrates and kept at 300 °C, using air as a carrier gas. Stoichiometry of the films was varied by adjusting the molarity of the spray solution. Structure and properties of films with different S/In ratios have been investigated. Raman spectroscopy present bands at 302 and 329 cm-1 indicating the presence of the β-phase in all the films. Optical transmittance of films is over 80% in the visible region and its energy band gap decreases from 2.7 to 2.67 ev. PL emission in the wavelength range 300-800 nm was recorded

Influence of silver doped indium sulfide on the structural and optical properties of spray pyrolyzed indium sulfide thin films

International audienceSilver doped indium sulfide thin films were deposited on ordinary glass substrates at 350°C, using chemical spray pyrolysis (CSP) technique. The samples have been prepared by varying the Ag/In ratio in solution from 0 % to 4 %. The effect of silver on structural and optical properties of In2S3Ag thin films has been investigated in detail using various characterization tools. XRD patterns confirmed that all the films have a nanocrystalline nature. The Raman spectroscopy showed the main mode at 306 cm-1 and 327 cm-1 indicating the presence of the β-phase in all films. Optical transmittance of spray pyrolyzed films exceeds 80% in the visible region and band gaps are estimated varying from 2.60 eV to 2.73 eV. © 2016 IEEE

Optimization of parameters for deposition of In2S3 films by spray pyrolysis using Taguchi method

International audienceThe aim of this research is to investigate the influence of the experimental conditions on the structural, morphological and optical properties of Indium Sulfide thin films deposition according to the Taguchi analysis method. The films are deposited on a glass substrate by spray pyrolysis a deposition method which is dependent on the concentrations of the precursor (indium and sulfide), the substrate temperature and the duration of the process. These four parameters are the key factors to be optimized in our study in conjunction with the morphological and optical properties of the films thanks to the Taguchi analysis, using a L9 Orthogonal array. © 2016 Taylor and Francis Group, LLC

Copper indium gallium disulphide (CuInGaS 2) thin films deposited by spray pyrolysis for solar cells: Influence of deposition time in controlling properties of sprayed CuInGaS 2 absorbers

International audienceCuInGaS2 (CIGS) multi-component semiconductors thin films were elaborated by spray pyrolysis on glass substrates using different spray times. The structural, optical and electrical properties of CuInGaS2 thin films were investigated. The obtained films were characterized using X-ray diffraction, Raman spectroscopy (RS), UV–Vis spectrophotometer and Hall Effect measurement. Thin films were formed by varying deposition time in the range, 30–50 min, keeping other deposition parameters as constant. The X-ray spectra revealed that the CuInGaS2 thin films have chalcopyrite structures with a highly (112) preferential orientation. The best crystallinity is obtained for HK-50 the maximum (112) peak intensity. RS also confirmed this structure. Optical constants such as band gap (Eg), extinction coefficient (k), refractive index (n), dielectric constants (εr) and (εi) and optical conductivity (σo p t) were calculated from the measured transmittance and absorption spectra in the wavelength range between 550 and 900 nm. The bulk concentration, mobility (μ), conductivity (σ), resistivity (ρ) and conduction type of thin films obtained at different deposition times were determined using Hall Effect measurements. It has been observed that the optimum time of spray was 50 min for best performed CuInGaS2 thin films with low resistivity and high mobility. Deposition time has been discussed to obtain the high quality thin film absorbers for solar cell applications. Here, we report a study on structural, optical and electrical properties of CuInGaS2 films grown by chemical spray pyrolysis in view of its application as an absorber in thin film solar cells. © 2016, Springer Science+Business Media New York