Tarek BEN NASRALLAH - Academia.edu (original) (raw)

Papers by Tarek BEN NASRALLAH

Physica Scripta

In this study, the structural, electronic, and thermoelectric properties of pure NiO and Cu-doped... more In this study, the structural, electronic, and thermoelectric properties of pure NiO and Cu-doped NiO were investigated. The structural and optoelectronic properties of nickel oxide and in the supercell containing 32 atoms CuNi15O16 were obtained by density functional theory (DFT) using the generalized gradient approximation (GGA) with the Hubbard correction potential U. The theoretical results obtained using the quantum espresso code show that the ferromagnetic character of the supercell structure is more stable than the antiferromagnetic configuration, and incorporating copper in the NiO matrix reduces the spin-up band structure. The value of the band gap channel is approximately 1.7 eV. The spin-down states cross the Fermi level and indicate the half-metal character of the CuNiO alloys. These results suggest that Cu-doped NiO is a potential candidate for infrared light and spintronic applications. The transport coefficients of the nickel oxide and copper doped NiO were calculated...

Des couches minces de quinizarin (1. 4 dhaq) et d'anthraflavic (2. 6 dhaq) ont ete deposees s... more Des couches minces de quinizarin (1. 4 dhaq) et d'anthraflavic (2. 6 dhaq) ont ete deposees sous vide. Les etudes par absorption infra rouge, diffusion raman, resonance magnetique nucleaire, spectroscopie de photoelectrons (xps) montrent que les dihydroxyanthraquinones (dhaq) ne sont pas decomposes pendant le processus de depot. De plus, les mesures de point de fusion montrent que la purete du film est superieure a celle du produit de depart. On montre que les differences essentielles entre les deux dhaq sont dues au fait que le quinizarin possede une liaison hydrogene contrairement a l'anthraflavic. Plus precisement la bande d'absorption optique de la transition * est situee autour de 2,60 ev dans le quinizarin tandis qu'elle se trouve vers 3,45 ev dans l'anthraflavic. Ceci est attribue a l'effet batochrome de la liaison hydrogene. Apres formation du complexe ag/dhaq on montre que la bande d'absorption du quinizarin situee a 480 nm est modifiee par recui...

physica status solidi (a), 2001

International Conference on Science and Technology of Synthetic Metals, 1994

The photosensitive characteristics of silver chloro anthraquinone derivatives (Ag/CAQDs) has been... more The photosensitive characteristics of silver chloro anthraquinone derivatives (Ag/CAQDs) has been investigated. CAQD with electron attracting chlorine substituents form charge transfer complexes in which an electron is transfered from the silver to the CAQD. Film complexes were fabricated by sequential Ag/CAQD vacuum deposition. The properties of the samples are investigated before and after annealing. The metal complex was indentified by X-rays diffraction, I.R. absorption and XPS measurements. The optical properties are also modified in such a way that this complexes may be used as optical memories.

Advanced Materials for Optics and Electronics, 1995

Quinizarin (1,4‐DHAQ) and Ag/I,4‐DHAQ thin films deposited under vacuum were investigated by I–V ... more Quinizarin (1,4‐DHAQ) and Ag/I,4‐DHAQ thin films deposited under vacuum were investigated by I–V measurements at various temperatures. It is shown that when submitted to an electric field of 5 × 105 V cm−1 or less, the I‐V characteristics of AI/DHAQ/AI sandwich structures are ohmic. The temperature dependence is I ∝ exp(‐ΔE/kT). The measured activation energy is 0.3 eV in the case of pure DHAQ and 30meV in the case of Ag/DHAQ. Therefore we can imagine that in the former case the conductivity is controlled by thermally activated hopping above intermolecular barriers, while in the latter case the conductivity can be attributed to tunnelling between silver grains.

International Journal of Applied Physics and Mathematics, 2013

Electrochromic iridium oxide thin films were deposited by spray pyrolysis technique onto indium-d... more Electrochromic iridium oxide thin films were deposited by spray pyrolysis technique onto indium-doped tin oxide (ITO) coated glass substrates using iridium chloride as an aqueous solution. The influence of the substrate temperature, the deposition period of time and the solution molarity have been investigated as related to the film's electrochromic (EC) performance. The electrochromic properties of the films were investigated in a (0.5M H 2 SO 4) aqueous electrolytic solution using cyclic voltammetry (CV). The transmittance has been measured over the spectral wavelength range between 300 and 2400 nm. The substrate temperature (T sub), the deposition period of time, the solution molarity and the colouration and bleaching potentials were optimized and found to be 400 o C, 10 min, 0.02 M, ±0.8 V, respectively. The films have acquired a maximum transmittance solar modulation ΔT s and a maximum visible modulation ΔTv at 630 nm optimal optical modulation. The iridium oxide thin films have demonstrated a pronounced anodic electrochromic behavior owing to Ir +4 Ir +3 intervalance charge transitions.

Solar Energy Materials and Solar Cells, 2006

AgInS 2 thin films have been prepared on glass substrates by the spray pyrolysis process using an... more AgInS 2 thin films have been prepared on glass substrates by the spray pyrolysis process using an aqueous solution which contains silver acetate (AgCH 3 CO 2), thiourea (SC(NH 2) 2) and indium chloride (InCl 3) as precursors. The depositions were carried out in the range of the substrate temperature from 260 to 420 1C. The value of the concentration ratio in the spray solution of indium and silver elements x ¼ [Ag + ]/[In 3+ ] was varied from 1 to 1.5 with [In 3+ ] ¼ 10 À2 M and [S 2À ]/[In 3+ ] was taken constant, equal to 4. The structural study shows that AgInS 2 thin film, prepared at 420 1C using optimal concentration ratio x ¼ 1:3 crystallizes in the chalcopyrite phase with a strong (1 1 2) X-ray diffraction line. Moreover, microprobe analysis (EPMA) shows that a nearly stoichiometric composition is obtained for these experimental conditions. Indeed, the atomic percentage of elements were. 24.5, 25.0, 49.5 for Ag, In and S, respectively. On the other hand from transmission and reflectance spectra, the obtained band gap energy is 1.83 eV for such film.

Solar Energy Materials and Solar Cells, 2007

physica status solidi (a), 2004

Zinc sulphide (ZnS) thin films have been prepared on Pyrex substrates by the spray pyrolysis tech... more Zinc sulphide (ZnS) thin films have been prepared on Pyrex substrates by the spray pyrolysis technique using zinc chloride and thiourea as precursors. The depositions were carried out on substrates heated at 450 °C. The films were then annealed under sulphur atmosphere for one hour at 450 or 500 °C. This process allows one to obtain well-crystallized cubic-type -ZnS thin

physica status solidi (a), 2000

Materials Science and Engineering: A, 2010

Materials Chemistry and Physics, 1995

Materials Chemistry and Physics, 1993

Materials Chemistry and Physics, 2001

Journal of Solid State Chemistry, 1993

ABSTRACT Quinizarin (1,4-DHAQ) thin films deposited under vacuum were investigated by IR absorpti... more ABSTRACT Quinizarin (1,4-DHAQ) thin films deposited under vacuum were investigated by IR absorption, X-ray diffraction, nuclear magnetic resonance (NMR), optical absorption, electron spectroscopy for chemical analysis elemental analysis (XPS), and scanning electron microscopy and melting point measurements. It was found that amorphous quinizarin thin films are obtained. IR absorption spectra, ion mass spectroscopy, and NMR spectra show that there is no decomposition during the deposition of the film, the quinizarin powder being sublimated under vacuum from a tantalum boat sustained at T = 418 K. In addition, elemental analysis and melting point measurements demonstrate that the deposition process is also a purifying process of the quinizarin. SEM microphotographs show that continuous, smooth thin films may be obtained when they are deposited at a sufficiently slow rate. XPS analysis shows that, after decomposition of the peak spectra, the O1s peak is composed of two different components corresponding to the oxygen bonded in the carbonyl and the hydroxyl groups. In the case of the C1s peak, the main component corresponds to the carbon of the cycle, while it was not possible to discriminate between the carbonyl and hydroxyl bonds, perhaps because of the hydrogen bond between these two groups. The presence of an absorption band around 480 nm in the optical absorption confirms the hydrogen bond between the hydroxyl and carboxyl in the 1,4-DHAQ. Optical absorption of an Ag/DHAQ structure shows that a complex may be obtained by annealing.

Journal of Physics and Chemistry of Solids, 1995

ABSTRACT We have deposited under vacuum two dihydroxyanthraquinones (DHAQ); quinizarin (1,4-DHAQ)... more ABSTRACT We have deposited under vacuum two dihydroxyanthraquinones (DHAQ); quinizarin (1,4-DHAQ) and anthraflavic (2,6-DHAQ). The former exhibits a strong absorption band in the visible range at about 480 nm which is attributed to a π → π∗ transition. The low value of the energy is attributed to the red shift effect of the hydrogen bond. For the latter compound this same π → π∗ absorbs at 360 nm because there is no hydrogen bond in 2,6-DHAQ. The films, after deposition, were characterized by infrared (IR), visible absorption and nuclear magnetic resonance (NMR) in order to check that the products did not decompose during the deposition process. In the case of 1,4-DHAQ the IR spectra of a thin film of quinizarin (tQ < 3 μm) and a thick film (tQ > 5 μm) were different. Only the spectra of thick films were identical to the reference powder spectra. This difference can be attributed to the high degree of disorder in the thin films. The optical properties of silver/DHAQ superposed films were studied using their thermal history as a parameter. The properties of Ag/2,6-DHAQ thin film samples, before or after annealing, were not modified, while those of 1,4-DHAQ thin films were modified after annealing of Ag/1,4-DHAQ samples.

Journal of Materials Science: Materials in Electronics, 2014

Indium doped tin oxide (SnO2:In) thin films were deposited on glass substrates by sol–gel dip coa... more Indium doped tin oxide (SnO2:In) thin films were deposited on glass substrates by sol–gel dip coating technique. X-ray diffraction pattern of SnO2:In thin films annealed at 500 °C showed tetragonal phase with preferred orientation in T (110) plane. The grain size of tin oxide (SnO2) in SnO2:In thin films are found to be 6 nm which makes them suitable for gas sensing applications. AFM studies showed an inhibition of grain growth with increase in indium concentration. The rms roughness value of SnO2:In thin films are found to 1 % of film thickness which makes them suitable for optoelectronic applications. The film surface revealed a kurtosis values below 3 indicating relatively flat surface which make them favorable for the production of high-quality transparent conducting electrodes for organic light-emitting diodes and flexible displays. X-ray photoelectron spectroscopy gives Sn 3d, In 3d and O 1s spectra on SnO2:In thin film which revealed the presence of oxygen vacancies in the SnO2:In thin film. These SnO2:In films acquire n-type conductivity for 0–3 mol% indium doping concentration and p type for 5 and 7 mol% indium doping concentration in SnO2 films. An average transmittance of >80 % (in ultra-violet–Vis region) was observed for all the SnO2:In films he In doped SnO2 thin films demonstrated the tailoring of band gap values. Photoluminescence spectra of the films exhibited an increase in the emission intensity with increase in indium doping concentration which may be due structural defects or luminescent centers, such as nanocrystals and defects in the SnO2.

Journal of Alloys and Compounds, 2009

ABSTRACT In this study, WO3 thin films were grown on glass substrates using an aqueous solution c... more ABSTRACT In this study, WO3 thin films were grown on glass substrates using an aqueous solution containing tungstate (NH4)2WO4 as precursor. The substrate temperature incremented from 250 to 500 °C, by steps of 50 °C. The structural properties were investigated using XRD, atomic force microscopy and scanning electronic microscopy techniques. Microprobe analyses showed that a balanced stoichiometric composition was obtained for thin films prepared at Ts = 350 and 400 °C. The X-ray diffraction analyses showed different structure crystallography in function of the substrate temperature. Moreover, films deposited at 400 °C were annealed in air for 2 h at 450 and 500 °C, respectively and the structural changes due to heat treatment were studied. Finally, the optical properties of these films were carried out using optical measurements of transmittance T(λ) and reflectance R(λ) spectra in 300–1800 nm domain. The refractive and absorption indexes, n and k were calculated. The band gap energy value was found lying in 2.6–3.6 eV domain.