A. Mzerd

SYNTHESIS AND MAGNETIC PROPERTIES OF Ni-DOPED ZnO THIN FILMS: EXPERIMENTAL AND AB INITIO STUDY

Structural and magnetic properties of Zn1−xNixO thin films and diluted magnetic semiconductors have been investigated. This sample has been synthesized using a spray pyrolysis technique with a stoechiometric mixture of zinc acetate (C4H6O4Zn⋅2H2O) and Nickel acetate (C4H6O4Ni⋅ 2H2O) on a heated glass substrate at 450∘C. The films were characterized by X-ray diffraction (XRD), UV–Vis spectrophotometry and Hall Effect measurements. These films of ZnO crystallized in the hexagonal Wurtzite structure. The optical study showed that the band-gap energy was increased, from 3.3eV to 3.5eV, with increasing the Ni concentration. The film resistivity was affected by Ni-doping, and the best resistivity value 1.15×10−2 (Ω cm) was obtained for the film doped with 2 at.% Ni. The electronic structure and optical properties of the Wurtzite structure Zn1−xNixO were obtained by first-principles calculations using the Korringa–Kohn–Rostoker method combined with the coherent potential approximation (CPA), as well as CPA confirm our results.

Transparent and conductive Al/F and In co-doped ZnO thin films deposited by spray pyrolysis

In doped ZnO (IZO), In-Al co-doped ZnO (IAZO) and In-F co-doped ZnO (IFZO) were deposited on glass substrates at 350 °C by spray pyrolysis technique. The structural, optical and electrical properties of as-deposited thin films were investigated and compared. A polycrystalline and (002) oriented wurtzite crystal structure was confirmed by X-ray patterns for all films; and the full width at half -maximum (FWHM) of (002) diffraction peak increased after co-doping. The investigation of the optical properties was performed using Uv-vis spectroscopy. The average transmittances of all the films were between 70 and 85%. Hall Effect measurements showed that the electrical conductivity of co-doped films increased as compared with IZO thin film. The highest conductivity of about 16.39 Ω-1 cm-1 was obtained for as-deposited IFZO thin film. In addition, the thin films were annealed at 350 °C for two hour under Ar atmosphere and their optical, electrical properties and the associated photoluminescence (PL) responses of selected films were analysed. After annealing, the electrical conductivity of all thin films was improved and the optical transmittance remained above 70%. Room temperature PL revealed that the annealed IAZO thin film had a strong green emission than that of IZO film.

Fe-doped CuO deposited by spray pyrolysis technique

Pure CuO and Fe-doped CuO nanostructures with different weight ratios (0%, 1%, 2%, 3% of Fe) were deposited on heated glass substrate by using a simple and low cost spray pyrolysis technique. The as-deposited thin films were carried out at fixed substrate temperature of 350°C. The Structural, morphological, optical and electrical properties of the films were investigated. The X-Ray Diffraction spectra showed that all samples exhibit polycrystalline nature corresponding to monoclinic crystal structure with two preferred orientations along the (-111) and (111) axis and confirmed that Fe ions incorporated successfully into CuO crystal lattice by occupying Cu ions sites. Polycrystalline morphology changes considerably with the variation of Fe content. Roughness parameters Ra and Rms of the surface and the grain size were estimated. Furthermore, the bandgap energy of the obtained CuO nanostructures was 1.47eV and the value was slightly decreased by Fe substitution. In addition, Hall Effect measurements revealed that the iron doping induced an increase in the resistivity.

In Situ Low-Temperature Chemical Bath Deposition of CdS Thin Films without Thickness Limitation: Structural and Optical Properties

In this work, thin CdS films have been deposited using the chemical bath deposition technique (CBD). Different synthesis parameters, such as number of runs, deposition time, and postannealing temperature, are studied and optimized in order to avoid the supersaturation phenomenon and to achieve a low-temperature growth. CdS thin films, of cubic structure, oriented along the (111) direction with homogenous and smooth surface, have been deposited by using the CBD growth process without any annealing treatment. Based on a set of experimental observations, we show that the solution saturation phenomenon can be avoided if the deposition is performed in several runs at a short deposition time. Throughout the CBD technique, it is then possible not only to overcome any film thickness limitation but also to grow the CdS films in a single technological step at a low temperature and without any postdeposition annealing treatment. CdS films with excellent structural quality and a controllable thickness are obtained when the deposition bath temperature is fixed at 65°C. In addition, deposited films exhibit an optical transmittance ranging from 70 to 95% depending on the synthesis parameters, with band gap energy around 2.42 eV. The process developed in this work might be useful for depositing CdS films on flexible substrates.

First principle calculations with SIC correction of Fe-doped CuO compound

In this work the electronic properties of Fe doped CuO thin films are studied by using a standard density functional theory. This approach is based on the abinitio calculations under the Korringa Kohn Rostoker coherent potential approximation. We carried out our investigations in the framework of the general gradient approximation and self interaction corrected. The density of states in the energy diagrams are presented and discussed. The computed electronic properties of the studied compound confirm the half metalicity nature of this material. In addition, the absorption spectra of the studied compound within the Generalized Gradient Approximation, as proposed by Perdew Burke Ernzerhof approximations are examined. When compared with the pure CuO, the Fermi levels of doped structures are found to move to the higher energy directions. To complete this study, the effect of Fe doping method in CuO has transformed the material to half metallic one. We found a high wide impurity band in two cases of approximations methods.

Effects of sulfur concentration on structural, optical and electrical properties of Tin Oxide thin films deposited by spray pyrolysis technique

Thin films of Tin oxide doped with deferent concentration of Sulfur were prepared on glass substrates at 400 °C by spray pyrolysis technique. The thin films were characterized to study their physical properties. Effects of Sulfur concentration on structural, optical and electrical properties of transparent Tin Oxide thin films were investigated in the Sulfur content range (0–10) at%. It was observed from X-ray diffraction patterns (XRD) that the films have a polycrystalline structure and the intensity of the peaks depends on the doping content. No diffraction peak related to dopants in XRD patterns along with a shift in peaks angles to SnO<inf>2</inf> proved that S ions were doped into SnO<inf>2</inf> thin films and the size of the grains has been changed from 3.7 to 4.1 nm. The optical gap of Sn<inf>1−x</inf>S<inf>x</inf>O<inf>2</inf> thin films was determined to be about 2.58 to 3.63 eV. From the Hall Effect measurements, the minimum resistivity 6.34×10⁻² (Ω.cm) was obtained from S-doped SnO<inf>2</inf> (5 at. %).

Effect of Gd doping and (Gd, Li) co-doping ZnO thin films on optical properties: Experimental and ab-initio study

The ZnO thin films were deposited by spray pyrolysis technique on glass substrate heated at 450° C, using as source zinc acetate with a molar concentration of 0.05 mol/l. Our interest is to study in some details the effect of doping Gd:ZnO (GZO) and co-doping Gd,Li:ZnO (GLZO) on optical properties. For this, we have used the optical UV-Visible spectroscopy to determine the band gap energy of the samples. Optical analysis revealed that the band gap energy increases, from 3.20 to 3.23 eV, with increasing the Gd concentration and increases for co-doped ZnO (Gd,2% Li) as compared to Gd doped ZnO from 3.23 to 3.25 eV. The electronic structure and optical properties of the Wurtzite structure Zn1−x−yGdxLiyO were obtained by ab-initio calculations using the Korringa-Kohn-Rostoker method (KKR) combined with the Coherent Potential Approximation (CPA), as well as Coherent Potential Approximation (CPA) confirms our results.

Physical properties of Gd doped ZnO thin films grown by spray pyrolysis

Undoped ZnO, Gd doped ZnO (GZO) thin films were prepared by chemical spray pyrolysis method at 350°C on glass substrates. The effect of gadolinium doping on structural, morphological, optical and electrical properties as function of dopant concentration has been studied. X-ray analysis showed that the films are polycrystalline fitting well with hexagonal wurtzite structure and have preferred orientation in [002] direction. The AFM analysis showed that the grain size as well as the roughness of the Gd doped ZnO films constantly decreases with increasing dopant content. The deposited films showed an average optical transmittance around 85% in the visible region and the optical band gap of the ZnO:Gd films decreases from 3.27 eV to 3.18 eV as dopant content increases. Hall Effect measurements showed that electrical conductivity, mobility carriers and carrier concentration of the films are increased after 1.5 % Gd doping concentration.

Preparation and characterization of Al doped ZnO thin films by spray pyrolysis

ZnO and Al-doped ZnO (AZO) thin films were prepared at 350°C on glass substrates by chemical spray pyrolysis method. In this contribution, the effects of aluminum doping on structural, optical and electrical properties are studied as function of dopant concentration, which was varied between 0 and 5 %. X-ray diffraction indicates that all the films exhibit hexagonal wurtzite structure and has polycrystalline nature. The preferential growth showed a variation depending on the doping ratios. Transmission measurements showed that for visible wavelengths, the AZO films have an average transmission of over 80%. The lowest resistivity was found to be 0.2 Ω.cm with a carrier concentration of 6.2 1020 cm-3 and high transmittance of 90 % at 550 nm after annealing.