Effect of Substrate Temperature on Properties of Nickel Oxide (NiO) Thin Films by Spray Pyrolysis (original) (raw)
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A simple and inexpensive spray pyrolysis technique was employed to deposit nickel oxide (NiO) thin films from hydrated nickel chloride salt solution onto amorphous glass substrate. The as-deposited films were transparent, uniform and well adherent to the glass substrate. The effect of the substrate temperature, the volume and the concentration of the sprayed solution on the structural, optical and electrical properties was studied using X-ray diffraction, optical transmittance, four point probe, scanning electron microscopy and atomic force microscopy. The structural analyses show that all the samples have a cubic structure. It was found that the increase in the volume of sprayed solution leads to an increment in the crystallite size of NiO and improves the homogeneity of the film. Optical measurements have shown that an increase in the thickness of the layer results in a decrease in the optical transmission, but it remains higher than 70 % even if the thickness exceeds 600 nm. At the same time, the optical gap decreases from 3.7 to 3.55 eV when the thickness increases from 133 to 620 nm. Low values of the electrical resistivity (less than 10 Ω.cm) were obtained for thin films with thicknesses less than about 240 nm, but for higher thicknesses the resistivity increases linearly to reach about 170 Ω.cm for a thickness of 620 nm.
2004
Nickel oxide films have been deposited from nickel chloride solution by spray pyrolysis technique onto glass substrates at different substrate temperatures ''T sub ''. X-ray diffraction (XRD) analysis showed that, at low T sub ; amorphous films have been obtained, while at higher T sub > 275 C; crystalline NiO with preferential growth along (1 1 1) plane. From measurements of spectral transmittance and reflectance, and on the basis of Murmann's exact equations, the optical constants have been computed over the spectral range 300-2500 nm. Analysis of the spectral absorption confirmed direct and indirect transitions with values markedly affected by T sub due to structure and offstoichiometry changes of the formed films. The dark electrical resistivity drops with three orders of magnitude for films deposited at higher substrate temperature due to improvement in crystallinity. The results have been interpreted by assuming two-phase model. Infrared spectral reflectance showed presence of nickel chloride in films formed at T sub p225 C; which is consistence with XRD findings and claiming incomplete pyrolytic reaction.
Nickel oxide thin films were prepared by chemical bath deposition (CBD) and by chemical spray pyrolysis from the same precursor onto glass substrate. The sprayed NiO thin films are polycrystalline in cubic phase structure with (111) preferred orientation. While the chemical bath deposited as a nickel hydroxide phase and transfer to polycrystalline NiO with annealing. The annealed CBD-films are polycrystalline NiO with cubic phase structure and preferred orientation (200). Sprayed and CBD-NiO films have optical transmittance in the visible region 70 and 46 %, respectively. Sprayed and CBD-NiO thin films have optical band gap 3.54 and 3.62 eV, respectively. Sprayed NiO thin films can be used as transparent materials in invisible electronics applications.
2018
Thin films of nickel oxide (NiO) were deposited on glass substrates at a different temperature of growth using a spray pyrolysis technique. X-ray diffraction (XRD) and optical properties have been studied for the properties of the samples obtained. Analysis of XRD data show that at a low growth temperature, an amorphous form has been obtained, while at high growth temperature (Tsub ≥ 275 C), single phase of the NiO formed which has a cubic structure. Optical properties were examined using spectral measurement at wavelength range of 300-2500nm. Optical constants (n and k) were calculated from corrected transmittance and corrected reflectance. The data obtained show that the direct transition (Eg) decreased from 3.738 to 3.146 eV and the indirect transition change from 2.790 to 2.049eV with increasing temperature. On the contrary, Urbach energy (band tail width), EU was found to be decreased from 0.65 to 0.36 eV. This behavior is believed to be associated with the increase of substrat...
Study of Physical Properties of Nanocrystalline NiO Thin Films Prepared by Spray Pyrolysis Technique
Volume 5,Issue 1,2019, 2019
In this paper a systematic study has been carried out on the influence of thickness on the physical properties of nanocrystalline nickel oxide (NiO) thin films prepared on glass substrate by spray pyrolysis method. The prepared nanocrystalline NiO films were characterized using X-ray diffraction technique (XRD), field emission scanning electron microscopy (FESEM) and optical measurement techniques. XRD patterns reveal the cubic structure for all the samples and the crystallite size varies with the thickness. FESEM images confirmed that all the films are homogeneous, without any crack, dense and exhibit almost complete coverage of the substrate. The optical parameters such as transmittance, absorption coefficient and energy band gap of the films as a function of film thickness was investigated by UV-Vis spectrophotometer. The band gap of the films is found to be direct allowed transition and the variation of band gap values of nanocrystalline NiO thin films were found to be in the range of 3.48 eV to 3.53 eV.
Synthesis and characterization of nickel oxide (NiO) thin films
Nickel Oxide (NiO) thin films were deposited by simple spray pyrolysis technique using nickel nitrate solution onto preheated glass substrate at substrate temperature 320 0 C and 380 0 C. Influence of substrate temperature on structural, morphological and optical properties were studied using X-ray diffraction, scanning electron microscopy and optical absorption. XRD results reveal that films are polycrystalline with single phase cubic structure and crystallinity of the film increases as the temperature increases. Surface morphological study shows spherical granular like shape at high deposition temperature. Optical band gap increases from 2.85 to 3.01 eV as the temperature increases.
Tin-doped nickel oxide thin films have been successfully prepared by spray pyrolysis technique on glass substrates at 460°C. The effects of tin doping on structural, optical, and electrical properties were investigated. X-ray diffraction pattern reveals that all prepared thin films have cubic structure with (111) preferred orientation. The surface topography of these films was performed by atomic force microscopy. Optical measurements show a high transparency in the visible range around 95%. The optical band gap Eg decreases with Sn content from 3.633 to 3.54 eV. PL measurements show some bands transition which shift irregularly with Sn doping. Finally, the electric conductivity of NiO thin film was investigated through the impedance spectroscopy measurements in the frequency range 5 Hz-13 MHz at various temperatures. These measurements show a thermally activation of the electric. AC conductivity of NiO thin films is investigated through Jonscher law. Also, from these measurements, dielectric parameters were calculated.
International Letters of Chemistry, Physics and Astronomy, 2014
In this work, nickel-cobalt oxide (Ni (1-x) Co x O) thin films, where x = 0, 4, 6 and 8 % have been successfully deposited on glass substrates by chemical spray pyrolysis (CSP) technique at substrate temperature of (400 °C) and thickness of about 300 nm. The structural and optical properties of these films have been studied using XRD, AFM, and UV-Visible spectroscopy. The XRD results showed that all films are polycrystalline in nature with cubic structure and preferred orientation along (111) plane. The crystallite size was calculated using Scherrer formula and it is found that the undoped NiO sample has maximum crystallite size (51.16 nm). AFM results showed homogenous and smooth thin films. The absorbance and transmittance spectra have been recorded in the wavelength range of (300-900) nm in order to study the optical properties. The optical energy gap for allowed direct electronic transition was calculated using Tauc equation. It is found that the band gap decreases as the Coconcentration increases and the band gap values were in the range of 3.58-3.66 eV and 3.58 eV for the prepared Nickel-Cobalt Oxide thin films. The Urbach energy increases as the Co-concentration increases and the Urbach. The optical constants including (absorption coefficient, real and imaginary parts of dielectric constant) were also calculated as a function of photon energy. Refractive index and extinction coefficient for Nickel-Cobalt Oxide thin films were estimated as a function of wavelength.
Physica B Condensed Matter, 2002
Polycrystalline nickel oxide films with preferential growth along (1 1 1) plane were deposited onto glass substrates, maintained at 3501C, by the spray pyrolysis technique using nickel chloride as starting solution. The effect of solution concentration on their structural, electrical, and optical properties was studied. Using X-ray diffraction, the structural characteristics have been studied and due to the high degree of preferred orientation, Voigt analysis of single reflection was used to determine the microstructural properties (crystallite size and microstrain). The refractive index n and the extinction coefficient k have been computed from the corrected transmittance and reflectance measurements over the spectral range 300-2400 nm. Analysis of the absorption versus photon energy curves revealed a direct transition with optical band gap, E g ; of 3.6 eV and indirect transition within the range 3.97-3.75 eV as solution molarity increases from 0.05 to 0.3 M. The electrochromic behaviour of polycrystalline nickel oxide film were investigated by means of cyclic voltametry in 1 M KOH aqueous solution. Cycling showed significant increase in solar optical modulation reaching a value of 0.23 after 150 cycles.
Optical and Quantum Electronics, 2019
Undoped and cobalt doped nickel oxide thin films (Co:NiO) at different doping concentrations were deposited on a glass substrate at constant substrate temperature by spray pyrolysis. The doping percentage increased from 0 to 10% and the effects of doping content on structural, morphological and optical properties were explored by X-ray diffraction, atomic force microscopy and UV-visible spectroscopy, respectively. X-ray diffraction configurations proved the NiO thin films were polycrystalline in nature having a cubic crystal structure. The regularly used parameters such as crystallite size, micro-strain, dislocation density and texture coefficient are presented from structural data. The average crystallite size is found between 10 and 14 nm with cobalt doping (Co) concentration. The band gap energies were increased with the effect of Co doping concentration in the range between 2.10 and 2.50 eV. The various optical constants as a function of photon energy are modified with Co doping concentration.