Caractérisation Des Couches Minces D’oxyde De Nickel (NiO) Elaboré Par Spray Pyrolyse

Abstract

The aim of this thesis focused on the elaboration and characterization of nickel oxide (NiO) thin films using spray pyrolysis method at 500°C heated glass substrate. In order to study and optimize the spray deposition condition, the effect of preparative parameters such us solvents nature, the concentration of precursor and volume of the sprayed solution on structural, optical and electrical properties of undoped NiO thin films will be carried in this work. Furthermore, to enhance some characteristics of NiO materials, the incorporation of dopant in the materials are the effective way to change several physical properties (transparency, conductivity and defect structure…etc). In this study, Copper (Cu) and lithium (Li) doped nickel oxide thin films were elaborated using spray pyrolysis technique. The dependence of Cu and Li doping concentration on the structural, morphological, optical, photoluminescence and electrical properties of NiO thin films will be reported. X-ray diffraction (XRD), UV-visible spectrophotometer, Fourier transformed infrared (FT-IR) spectroscopy, photoluminescence (PL) spectroscopy, Seebeck effect and four-point probe method were used to characterize the deposited films. The obtained results show that: • The XRD analysis indicated that undoped NiO films deposited at different solvent nature present polycrystalline nature with (111) preferential orientation. The crystallite size of films varies between 22-39 nm as function of solvent nature. All films exhibit a high optical transparency between 84% and 71% in the visible range. However, the optical band gap was found to vary in the range 3.58 to 3.65 eV. The obtained results confirm that the films prepared with de-ionized water have better crystallinity, with good optical and electrical properties. • With variation of precursor concentration, the (111) peak intensity becomes more significant, when precursor concentration reaches 0.1 M leading to an increment in NiO crystallite size close to 37nm. FT-IR analysis of spectra confirmed the existence of Ni-O bonds vibrations modes. The band gap energy of the films decreases from 3.68 to 3.60 eV with increasing precursor concentration. • From XRD results it was shown that the deposited thin film with the volume lower than 10 ml was amorphous and with increasing volume up to 10 ml NiO thin films structure become polycrystalline with cubic structure and (111) as preferential orientation. All films exhibit an average optical transparency between 50% and 80% in the visible range and their band gap values were ranged in 3.38-3.62eV. The minimum resistivity of the NiO films is 8.662 Ω.cm from film prepared at 30ml solution volume. • the XRD patterns showed that undoped and doped NiO films structure are polycrystalline with (111) preferred orientation and the observation of shift orientation of the peaks after doping with Cu ,whereas doping with Li in the NiO material did not change position of the diffraction peaks significantly. The grain size decreases as doping concentration increase in NiO samples. From the transmittance spectra, it observed that the optical transparency decrease with the increase of Cu or Li doping concentration. The band gap energy is found to vary from 3.62-3.95eV in the case of Cu doped NiO films, however from the films prepared with Li doped NiO films the band gap is ranged from 3.84 to 3.57 eV . The type conductivity of all samples are P-type semiconductor, whereas a low conductivity was obtained for the undoped NiO thin films, after doping the conductivity increases as a function of Cu or Li doping level.