Site location of Al-dopant in ZnO lattice by exploiting the structural and optical characterisation of ZnO:Al thin films

The zinc oxide thin films, highly transparent, doped aluminium were prepared on glass substrates by the reactive chemical spray method. The incorporation nature of Al atoms in the ZnO lattice was determined by X-ray diffraction and optical analyses. Indeed, for low doping ⩽2%, the results of X-ray spectra analysis show a simultaneous reduction of lattice parameters (a and c), this variation, which follows VEGARD’s law, tends to indicate a substitution of Zn by Al. By against for doping >2% the increase in the lattice parameters thus the grain sizes, in accordance with the VEGARD’s law can be explained by occupation of the interstitial sites by Al atoms. Beyond 4%, the material tends to get disorderly and the crystallites orientation is random. The studied optical properties show that the variation of the optical gap follows a law of the x3/2 form for x < 3% (x is the aluminium atom fraction incorporated in the ZnO lattice). The granular structure is fairly visible and some local growths are disrupted. The crystallite size at low enlargement is coherent with the XRD results. Keywords: Al-doped ZnO thin films, XRD, Substitutional and interstitial sites, Band gap, SE

Enhancement of optical and electrical properties of spray pyrolysed ZnO thin films obtained from nitrate chemical by Al-Sn co-doping

International audienceUn-doped, Al-doped, and Sn-Al co-doped ZnO thin films have been successfully synthesized by Spray Pyrolysis method. Zinc Nitrate (Zn(NO3)2), Tin Chloride (SnCl2) and Aluminum Nitrate (Al(NO3)3) were used as starting chemicals at different compositions. Films depositions were carried out on glass substrates at 350 °C. The X-ray diffraction confirmed that the Al-Sn co-doping did not change the ZnO Hexagonal Wurtzite structure. The obtained un-doped ZnO films were highly oriented along the preferential (002) crystallographic plane while the Sn- Al co-doped ZnO films were disoriented with slight loss of crystallinity. The optical measurement showed an increase of the average transmittance from 65 % to 81 % and the band gap energy (Eg) from 3.23 to 3.30 eV. The electrical conductivity has increased with the Al-Sn co-doping concentration to reach the value of 0.335 (Ω.cm)−1

First synthesis of vanadium oxide thin films by spray pyrolysis technique

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Optical and electrical properties of Bi₂S₃ films deposited by spray pyrolysis

International audienceThin films of Bi2S3 were prepared by spray pyrolysis method. Optical constants, electrical and photoelectrical studies have been carried out on these films. The optical constants confirm that the Bi2S3 thin film has a direct band gap of 1.69 eV. The Hall Effect measurements indicate that the Bi2S3 thin films prepared by spray pyrolysis method are n-type in nature with a carrier concentration of 3.51 × 1017 cm− 3. An activated process with activation energy of 65 meV governs the conduction in these films. The photoconductivity measurement indicates the presence of continuously distributed localized gap states in this material

Synthesis and characterization of antireflective Ag@AgCl nanocomposite thin films

International audienceSilver chloride thin films were easily prepared for the first time by direct spraying of silver chloride (AgCl) solution with low molarity on glass substrates heated at 200 °C, 250 °C, 300 °C and 350 °C. The X-ray diffraction (XRD) data showed that the films have cubic symmetry and are subject to compressive and tensile strains. Transmission electron microscopy revealed the presence of Ag nanoparticles (NPs) of different sizes embedded in AgCl thin films. These nanoparticles were roughly spherical and well crystallized in the case of the film prepared at 350 °C. The Raman and X-ray photoelectron spectroscopy confirmed the XRD results. The UV–vis-NIR spectroscopy indicated a low reflectance with antireflecting properties and high optical transmission superior to 80 % at 350 °C. The obtained films have wide indirect band gap and exhibit localized surface plasmon resonance (LSPR) peak at 407 nm at deposition temperature of 350 °C due to the presence of Ag NPs

The relationship between processing and structural, optical, electrical properties of spray pyrolysed SnO₂ thin films prepared for different deposition times

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«Propriétés structurales et optiques des couches minces WO_(3-x) fabriquées par la technique Spray-Pyrolysis»

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Rietveld refinement combined with first-principles study of Zn and Al-Zn doped CdO thin films and their structural, optical and electrical characterisations

International audienceUn-doped, Zn-doped, and Al–Zn co-doped CdO thin films were deposited onto glass substrates at 350 °C by spray pyrolysis. X-ray diffraction (XRD) analysis was conducted to investigate the structural properties of the films. The XRD patterns confirmed that all the films crystallize in a cubic structure and that the addition of Zn and Al did not alter the CdO crystal structure. Energy-dispersive X-ray spectroscopy analysis further confirmed the successful incorporation of Zn and Al into the CdO films. Theoretical calculations based on first-principles were performed, and crystallographic information files (CIF) were obtained for optimized theoretical supercells in space group Pm3-m. The CIF files were used as input for experimental XRD spectra Rietveld refinement, to determine the Wyckoff positions of the dopants and their occupation rates. The optical properties of the films were characterized using transmittance measurements in the wavelength range of 300–1700 nm. The optical data indicated an increase in the average transmittance from 60 to 70% within the wavelength range of 600–1700 nm upon Al–Zn co-doping. The estimated direct optical band gap of the un-doped, doped, and co-doped CdO thin films is varied between 2.41 and 2.50 eV. All the samples exhibited n-type conductivity with low electrical resistivity of about 1.32 × 10–4 Ω⋅cm. Co-doped CdO thin films with 1% Al and 3% Zn exhibited higher carrier concentration (4.39 × 10+20 cm−3) than the other samples