Papers by azeddine chelouche
Growth of AZO/Cu/AZO multilayer structures by confocal RF magnetron sputtering and their microstructural and optoelectronic properties before and after annealing
Materials Science and Engineering: B
Elaboration De Couches Minces De Zno a Faibles Pertes Optiques Par Procede Sol-Gel
Effect of Sol Concentration on Optical Propoerties of Sol-Gel Thin Films for Photonic Applications
Semiconductors, 2020
For this study, titanium dioxide (TiO 2) thin films were deposited on glass substrates at room te... more For this study, titanium dioxide (TiO 2) thin films were deposited on glass substrates at room temperature by the RF magnetron sputtering technique. The preparation parameters that offer better control and reproducibility of film fabrication were first optimized. Then, the effects of post-deposition annealing temperature at 350, 450, and 550°C on the microstructure, surface morphology, and optical properties of the prepared films were investigated using X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-Visible (UV-Vis) spectrophotometry. Interestingly, XRD analysis shows that as-deposited and annealed TiO 2 film possess anatase crystal structure only with a preferential orientation along the (101) plane. The intensity of the (101) diffraction peak and crystallite size are found to increase with increasing annealing temperature, which indicates an improvement in the crystallinity of the films. Raman spectra confirm that all samples possess anatase phase and the crystallinity is enhanced with increasing thermal annealing. From the analysis of SEM and AFM images, it is revealed that the heat treatment significantly affects the morphology, grain size, and surface roughness of the TiO 2 films. The UV-Vis spectroscopy analysis shows that as-deposited TiO 2 thin film is highly transparent in the visible region with an average transmittance about 84%, whereas the transmission decreases slightly with an increase in annealing temperature. Moreover, the optical band gap energy shows a red shift with increasing the annealing temperature.
Journal of Sol-Gel Science and Technology, 2020
TiO 2-based sol-derived materials were synthesized by supercritical drying assisted sol-gel proce... more TiO 2-based sol-derived materials were synthesized by supercritical drying assisted sol-gel process. The effects of supercritical fluid (acetone, ethanol, and methanol) on structural and morphological properties of TiO 2 nanocrystallites were investigated by XRD, infrared spectroscopy, SEM, and specific surface area measurements. The samples synthesized in acetone and ethanol are pure anatase and the brookite phase visibly appears when the methanol is used as supercritical fluid. The structural parameters are found to be dependent on supercritical drying conditions of fluids. The presence of Ti-O and Ti-O-Ti bonds was confirmed by FTIR measurements. EDAX analysis showed that the sample elaborated in ethanol is oxygen rich with higher cell parameters. SEM images show that the samples synthesized in acetone and methanol are formed by spherical and dispersed particles whereas the particles of the sample synthesized in supercritical ethanol are heavily agglomerated to form a denser monolithic block. BET measurements showed that the lowest pore diameter, the biggest pore volume, and the highest specific surface area are found in the TiO 2-based sol-derived materials synthesized in supercritical methanol. The adsorption isotherm of the sample synthesized in supercritical methanol is found to be composed of two hysterisis loops probably due to the presence of two types of pores which increase the global pore volume. This result indicates that the adsorption capacity can be generally improved by increasing the specific surface area and pore volume of catalysts.
Journal of Physics: Conference Series, 2018
Undoped, Ce-doped, Cu-doped and (Ce,Cu) co-doped ZnO aerogels were synthesized by sol-gel process... more Undoped, Ce-doped, Cu-doped and (Ce,Cu) co-doped ZnO aerogels were synthesized by sol-gel process in supercritical conditions of ethanol. [Cu]/ [Zn] and [Ce]/[Zn] atomic ratios were fixed at 0.02 (2%). The aerogels were investigated without any additional treatments by using X-ray diffraction (XRD), UV-visible spectrophotometry, scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), Fourier transforms infrared spectroscopy (FTIR) and photoluminescence spectroscopy (PL). XRD results revealed that all the samples are well crystallized in hexagonal wurtzite structure. EDS measurements showed that highly pure aerogels are prepared. SEM analysis indicated that the morphology of the samples is dependent on Cu and Ce dopants. From UV-visible spectroscopy analyses, it was shown that the absorption and the band gap of the aerogels are strongly affected by Ce and Cu dopants. FTIR spectra demonstrated that co-doping induces a shift of Zn-O bond vibration band toward low wavenumbers. The room temperature photoluminescence spectra put into evidence that the visible emission intensity is influenced by Ce and Cu doping. In particular, the co-doping leads to the appearance of a blue emission band at 443 nm.
Journal of Luminescence, 2017
Low cerium doping investigation on structural and photoluminescence properties of sol-gel ZnO thi... more Low cerium doping investigation on structural and photoluminescence properties of sol-gel ZnO thin films,
Influence of Pb doping on the structural, morphological and optical properties of sol–gel ZnO thin films
Materials Science in Semiconductor Processing, 2016
Abstract In this work, undoped and lead (Pb)-doped ZnO thin films were deposited on glass substra... more Abstract In this work, undoped and lead (Pb)-doped ZnO thin films were deposited on glass substrate using the sol–gel dip-coating process. The effects of different Pb doping concentrations on the structural, morphological, optical, electrical and photoluminescence properties of such films were investigated by X-ray diffraction (XRD), energy-dispersive X-rays (EDS), atomic force microscopy (AFM), UV–vis–NIR spectrophotometry, Hall effect measurement and Photoluminescence (PL) spectroscopy. XRD patterns of the synthesized films exhibited hexagonal wurtzite crystal structure with a c -axis preferred (002) orientation. AFM images showed that film morphology and surface roughness were influenced by the Pb doping level. Incorporation of Pb was confirmed from elemental analysis using EDS. The UV–vis–NIR spectroscopy characterizations demonstrated that all the films were highly transparent with average visible transmission values ranging from 75% to 85%. Electrical measurement shows that carrier concentration and resistivity are dependent on Pb content. Room temperature PL spectra clearly indicated a great dependence of the UV, green and red emissions on the Pb concentration. In particular, the red emission at 2 eV is quenched after introduction of Pb atoms.
Influence of Mn doping on structural and optical properties of ZnO nano thin films synthesized by sol–gel technique
Applied Physics A, 2012
Undoped and Mn-doped ZnO samples with different percentages of Mn content (1, 5 and 10 at%) were ... more Undoped and Mn-doped ZnO samples with different percentages of Mn content (1, 5 and 10 at%) were synthesized by a dip-coating sol–gel method. We have studied the structural, chemical and optical properties of the samples by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-visible spectroscopy. The XRD spectra show that all the samples are hexagonal wurtzite structures. We note that doping favors c-axis orientation along (002) planes. Up to 5 at% of Mn doping level, the c-axis lattice parameter shifts towards higher values with the increase of manganese content in the films. The expansion of the lattice constant of ZnO–Mn indicates that Mn is really doped into the ZnO. The SEM investigations of all samples revealed that the crystallites are of nanometer size. The surface quality of the ZnO–Mn film increases with Mn doping but no significant change of the grain size is observed from SEM images. The transmittance spectra show that the transparency of all the samples is greater than 85 %. We note, also, that a small doping (1 %) lowered the refractive index while the thickness of the layers and the gap increase. However, on raising the proportion of Mn beyond 5 %, practically the same values of index and gap as pure ZnO are found.
Effects of deposition time in chemically deposited ZnS films in acidic solution
Thin Solid Films, 2015
ABSTRACT
Nanocomposite films formed by direct inclusion of ZnO aerogel nanoparticles in liquid state silic... more Nanocomposite films formed by direct inclusion of ZnO aerogel nanoparticles in liquid state silica matrix and deposited by dip and spin-coating techniques on glass substrates were elaborated. The ZnO aerogel particles were synthesized in supercritical methanol using a modified sol-gel process. The elaborated particles and the coated composite films were characterized by XRD, FTIR spectroscopy and by optical absorption. XRD patterns show a broadening of diffraction peaks of ZnO crystallites and a significant reduction in the intensity after their dispersion in silica. A reduction in lattice parameters was observed after the introduction of ZnO aerogel particles in silica. The Zn-O vibration bond strongly shifts to lower wavenumbers in composite films compared to the aerogel due to the formation of silica layerand successfully grafted over the ZnO nanoparticles. A strong Zn-O-Zn vibration bond is observed only in the spin-coated film. The blue shift observed in the absorption spectra ...
Particularities of pure and Al-doped ZnO nanostructures aerogels elaborated in supercritical isopropanol
Arab Journal of Basic and Applied Sciences
Abstract Undoped and Al-doped ZnO nanoparticles are synthesized in supercritical isopropanol usin... more Abstract Undoped and Al-doped ZnO nanoparticles are synthesized in supercritical isopropanol using zinc acetate di-hydrate, aluminum nitrates and methanol as precursor, dopant source and solvent, respectively. The atomic ratio [Al]/[Zn] is fixed to 3%. X-ray diffraction (XRD) results indicate that the synthesized ZnO nanoparticles possess hexagonal wurtzite structure. Al-doping of ZnO aerogel leads to the improvement of the crystalline quality due to the occupation of Zn2+ sites by Al3+ ions. The crystallites size is found to be 32 nm in pure ZnO and 50 nm in the doped aerogel. Fourier-transform infrared spectroscopy spectra reveal that the intensity of the absorption bands in ZnO decreases and the Zn-O vibration band position shifts towards higher wave numbers upon Al-doping. UV–Visible measurements show a reduction in the band gap and a shift towards long wavelength side of the absorbance with Al-doping. Scanning electron microscopy images reveal that aerogel grains are quasi-spherical in pure ZnO and have different and random forms of morphologies in the doped sample. Room temperature photoluminescence (PL) studies put into evidence that the PL emission peaks are influenced by the Al-doping, in particular, a decrease in the green emission at 535 nm is observed.
Synthèse de films nano-composites de ZnSePMMA et ZnSepolystyrène
Structural and morphological characterizations of ZnO nanopowder synthesized by hydrothermal route using inorganic reactants
Journal of Semiconductors, 2014
Zinc oxide nanoscale powder has been synthesized by a hydrothermal route using zinc sulfate and s... more Zinc oxide nanoscale powder has been synthesized by a hydrothermal route using zinc sulfate and sodium hydroxide. The as-prepared powder was annealed at 600℃ for 2 h and then characterized by X-ray diffraction (XRD), scanning electron microscopy and infra-red Fourier transformed spectroscopy. XRD measurements have shown a ZnO hexagonal wurtzite polycrystalline structure with good crystallinity and the formation of a new sodium pyrosulfate phase in the as-prepared powder. The annealing improves the crystalline quality of the powder and transforms the sodium pyrosulfate phase to a sodium sulfate one. The thermal treatment does not affect the lattice parameters and the Zn-O bond length but improves the random orientation of the ZnO crystallites growth. ZnO crystallites have an interconnected-nano-needles morphology forming irregular shaped aggregates. The size of the crystallites is about 20 nm. EDX analysis has shown the presence of C and S in addition to Zn and O. FTIR spectra confir...
Etde ZnO préparées par sol-gelude de l’effet du stabilisant et du dopage Argent sur les propriétés des couches minces
Kinetic Monte Carlo simulation of self-organized growth of silver nanoparticles in a TiO2 matrix
Journal of Crystal Growth, 2021
In the present study, we have used a simulation program based on the kinetic Monte Carlo (KMC) me... more In the present study, we have used a simulation program based on the kinetic Monte Carlo (KMC) method able to describe the self-organized growth process of silver nanoparticles (AgNPs) in a titanium dioxide (TiO2) thin film. First, the deposition process of TiO2 films prepared by a sol–gel technique is investigated. Obtained simulated TiO2 nanostructures and numerical results are given and discussed according to the deposition rate as the main influent parameter. Next, a new simulation pattern describing the spontaneous periodic array formation of smaller spherical AgNPs in a TiO2 matrix is developed. The origin of the transmission spectra is analyzed in terms of the polarization nature, incident angle and excitation wavelength.
Al-Doping Effects on Structural and Morphological Properties of ZnO Aerogels Synthesized in Supercritical Ethanol
Aerogels of pure and aluminium doped ZnO (Al-ZnO) were synthesized by sol-gel route followed by s... more Aerogels of pure and aluminium doped ZnO (Al-ZnO) were synthesized by sol-gel route followed by supercritical drying in ethanol. The atomic percentage of the dopant is fixed at 1, 3, 5 and 10 at.%. The elaborated aerogels were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive analysis (EDAX) and Fourier transform infrared spectroscopy (FTIR). The DRX results revealed good crystalline quality of the synthesized samples with hexagonal wurtzite crystallographic structure. No crystalline phase related to aluminum ions or aluminum based compounds has been detected. With increasing Al content in aerogels, the crystallinity deteriorates and the cell parameters are found to be slightly changed. SEM images showed that the presence of Al atoms in the ZnO lattice strongly alters grain morphology, especially for higher doping levels (≥ 5 at.%). The EDAX spectra showed well-defined peaks related only to Zn, O and Al and confirmed the absence of...
超臨界メタノール中でのZnOエアロゲルナノ粉末の合成:構造,モルホロジおよび光学的性質に及ぼすゾル濃度の効果
Journal of Sol-Gel Science and Technology, 2016
In this work, almost stress-free highly c-axis oriented zinc oxide (ZnO) thin films were deposite... more In this work, almost stress-free highly c-axis oriented zinc oxide (ZnO) thin films were deposited on glass substrates by a sol-gel dip-coating process. Theeffects of low cerium doping concentration (Ce/Zn<1%) on the structural,morphological and optical properties of the prepared films were studied by X-ray diffraction (XRD), atomic force microscopy (AFM), UV-Visible spectrophotometry and photoluminescence spectroscopy (PL). XRD analysis revealed that all the films were highly c-axis oriented and had a hexagonal wurtzite structure. The crystallite size values were determined and found to be dependent on Ce content. AFM images have shown that film morphology and surface roughness were influenced by Ce doping concentration. UV-Visible measurements have revealed that all the films were highly transparent withaverage visible transmittance values ranging from 75% to 90%. Photoluminescencemeasurements have indicated that UV and visible emissions decrease drastically as the Ce concentra...
Synthesis and Characterization of Tio2 Thin Films for Photovoltaic and Optoelectronic Applications
In this paper, TiO2 thin films were first deposited by RF magnetron sputtering on glass substrate... more In this paper, TiO2 thin films were first deposited by RF magnetron sputtering on glass substrates at different temperatures. Then, the obtained samples were characterized by several techniques: X-ray diffraction, scanning electron microscopy, atomic force microscopy and ultraviolet-visible spectroscopy. Hence, after a brief description of the preparation conditions we investigate the effects of substrate temperature, Ts, (RT, 200, 300 and 400 °C) on structural, morphological and optical properties of all prepared TiO2 thin films. It was found that increasing Ts leads to several interesting phenomena: (i) more uniform distribution of densely packed well-defined grains (ii) the root mean square roughness increases from 3.88 to 9.56 nm, (iii) improvement of the crystalline structure, (iv) the crystallite size increases from 13.4, to 22.3 nm, (v) the films are highly transparent in the visible region and (vi) the direct optical band gap value of the films is found to decrease from 3.64...
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Papers by azeddine chelouche