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Journal ArticleDOI

Synthesis and characterization of Ca doped ZnO thin films by sol–gel method

TL;DR: In this article, the structural changes in the molecular binding between ZnO and Ca, Fourier Transform Infrared spectroscopy (FTIR), Micro-Raman Spectroscopy and X-ray diffraction (XRD) were performed.
Abstract: ZnO thin films were synthesized using sol–gel method at 0.25 and 0.5 M molarity concentration. Moreover, the obtained thin films were Calcium-doped with 1 and 5 at% concentration. In order to investigate the structural changes in the molecular binding between ZnO and Ca, Fourier Transform Infrared spectroscopy (FTIR), Micro-Raman Spectroscopy and X-ray diffraction (XRD) were performed. The surface morphology and the chemical constituents distribution of the films were studied through Scanning Electron Microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and Atomic Force Microscopy (AFM), respectively. The optical and electrical properties were studied by UV–Vis spectroscopy, Spectral ellipsometry and electrical I–V measurements. The results show that the properties of prepared ZnO thin films were strongly influenced by the molarity concentration and Ca-dopant. The band shape obtained at FTIR is a band attributable to metal oxide bonds and can be attributed to the vibrational assignment of Zn–O bond. SEM-EDX and AFM investigations reveal an enlarged surface area due to the porous nature of the thin films and confirm the presence of Ca in the ZnO matrix. The XRD and Raman analyses indicate the achievement of the high crystalline quality and confirm the wurtzite phase of the synthesized thin films. The films transmittance spectra indicate values between 81 and 93% in the 350–800 nm wavelength region. We further performed I–V characteristics, resulting that Ca has a different impact of the electrical performances.
Citations
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Journal ArticleDOI
TL;DR: In this article, the effects of pH, Ca doping, light, ultrasound, and pH on the mineralization of tetracycline by Ca-doped ZnO nanopowders were systematically investigated.

45 citations

Journal ArticleDOI
TL;DR: In this article , the effects of pH, Ca doping, light, ultrasound, and pH on the mineralization of tetracycline by Ca-doped ZnO nanopowders were systematically investigated.

39 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of calcium on the structural, morphological, and optical properties of the resultant powders were investigated, and the XRD patterns showed that calcium has been incorporated into the ZnO lattice and the crystallites have nanometric size in the range of 50-nm.
Abstract: Ca-doped ZnO (CZO) nanopowders were synthesized via a simple sol–gel method. The effects of calcium on the structural, morphological, and optical properties of the resultant powders were investigated. The XRD patterns showed that calcium has been incorporated into the ZnO lattice and the crystallites have nanometric size in the range of 50 nm. TEM observations depicted that crystallites possess spherical shape and confirm the nanometric size. UV–Vis–NIR characterization revealed an absorption band in the UV range with a decrease in optical band gap from 3.24 to 3.2 eV with increasing Ca concentration. Pure ZnO- and Ca-doped ZnO nanoparticles were used as active layer and tested for their sensing performance to formaldehyde. The most performed prepared sensor exhibits good formaldehyde sensing properties, including a high response of 5.28 (5 ppm, 250 °C) and low detection limit (≤ 1 ppm).

23 citations

Journal ArticleDOI
TL;DR: In this paper, pure and doped ZnO thin films were prepared by sol-gel-based method and their electro-optical properties were investigated by using various techniques X-ray diffraction (XRD), EDS, and field emission scanning electron microscopy (FESEM).
Abstract: In this study, pure and doped ZnO thin films were prepared by sol–gel-based method and their electro-optical properties were investigated. For doping process, 1 at. % Al and Cu was incorporated in ZnO solution separately, and the thin films were prepared by dip coating method. The microstructure and morphology of calcined ZnO, Al-doped ZnO, and Cu-doped ZnO thin films were evaluated and compared by using various techniques X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and field emission scanning electron microscopy (FESEM). Results showed that nanostructured ZnO thin films with cross-linked nanoparticles (NPs) were formed, and the size of ZnO NPs increased with the Al and Cu doping. It was also found that the substitution and interstitial of Al and Cu dopants caused the instability of ZnO crystal structure and generation of extra point defects. Photoluminescence (PL) properties indicated that the dopants incorporation causes the decline of the PL intensity and the shift of the localized energy states of electrons and holes to lower energy levels. Evaluation of thin films in the UV–Vis range demonstrated that the transparency increased (>94%), and the band gap decreased to 3.08 and 3.06 eV with the incorporation of Al and Cu into ZnO thin films, respectively. The electrical conductivity also improved by Al and Cu doping of ZnO TFs.

21 citations

Journal ArticleDOI
01 Nov 2022-OpenNano
TL;DR: In this article , a thorough review of the use of selenium or silver doped ZnO NPs for photocatalytic and antibacterial objectives was conducted in this study.

10 citations

References
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Journal ArticleDOI
L. Znaidi1
TL;DR: In this article, the main chemical routes used in the sol-gel synthesis of undoped ZnO thin films and highlights the chemical and physical parameters influencing their structural properties are summarized.
Abstract: During the last years, ZnO thin films have been studied extensively due to their potential applications in e.g. piezoelectric and optoelectronic devices or photovoltaic cells. Ordered c-axis orientation of ZnO crystallites is desirable for applications where crystallographic anisotropy is a prerequisite such as for short-wavelength semiconductor diode lasers (SDLs), and piezoelectric surface acoustic wave or acousto-optic devices. Many works were dedicated to c-axis oriented ZnO thin films elaboration and the study of their properties, including physical and chemical methods. For instance, sol–gel processes are particularly well adapted to produce ZnO films in a simple, low-cost and highly controlled way. This review summarizes the main chemical routes used in the sol–gel synthesis of undoped ZnO thin films and highlights the chemical and physical parameters influencing their structural properties. In this process, the ZnO films synthesis includes three principal steps: (i) solution preparation, (ii) coating and (iii) heat treatment. For the first step, the particle formation is discussed including nucleation and growth, particle size, morphology and colloids stability. These three steps involve several parameters such as: (i) nature and concentration of precursor, solvent and additive, and solution aging time, for the chemical system, (ii) coating method, thickness and substrate for the coating step, and (iii) pre-and post-heat treatment for the last step. The influence of these steps and synthesis parameters on ZnO thin films orientation is discussed.

618 citations

Journal ArticleDOI
Y Natsume1, H Sakata1
TL;DR: In this article, electrical conductivity and optical properties of undoped zinc oxide films prepared by the sol-gel process using a spin-coating technique were investigated, and it was shown that the optical band gap energy for the films was 3.20-3.21 eV and the electronic transition was of the direct transition type.

454 citations

Journal ArticleDOI
TL;DR: In this paper, the structure, optical and electrical properties of ZnO films were investigated, and the c-axis lattice constants of the thin films and the band gap were shown to be a little larger than those of the crystal. But the differences between the thin film and crystal might be attributable to the grain boundaries and imperfections in thin films.

361 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of thermal annealing in air on the physical properties of the sol-gel derived ZnO thin films were studied, and the powder and its thin film were characterized by X-ray diffractometer (XRD) method.

283 citations

Journal ArticleDOI
TL;DR: In this paper, a reliable sol-gel approach, which combines the formation of ZnO nanocrystals and a solvent driven, shape-controlled, crystal growth process to form well-organized ZnOsO nanostructures at low temperature is presented.
Abstract: A reliable sol–gel approach, which combines the formation of ZnO nanocrystals and a solvent driven, shape-controlled, crystal-growth process to form well-organized ZnO nanostructures at low temperature is presented. The sol of ZnO nanocrystals showed shape-controlled crystal growth with respect to the solvent type, resulting in either nanorods, nanoparticles, or nanoslates. The solvothermal process, along with the solvent polarity facilitate the shape-controlled crystal growth process, augmenting the concept of a selective adhesion of solvents onto crystal facets and controlling the final shape of the nanostructures. The XRD traces and XPS spectra support the concept of selective adhesion of solvents onto crystal facets that leads to yield different ZnO morphologies. The shift in optical absorption maxima from 332 nm in initial precursor solution, to 347 nm for ZnO nanocrystals sol, and finally to 375 nm for ZnO nanorods, evidenced the gradual growth and ripening of nanocrystals to dimensional nanostructures. The engineered optical band gaps of ZnO nanostructures are found to be ranged from 3.10 eV to 3.37 eV with respect to the ZnO nanostructures formed in different solvent systems. The theoretical band gaps computed from the experimental XRD spectral traces lie within the range of the optical band gaps obtained from UV-visible spectra of ZnO nanostructures. The spin-casted thin film of ZnO nanorods prepared in DMF exhibits the electrical conductivity of 1.14 × 10−3 S cm−1, which is nearly one order of magnitude higher than the electrical conductivity of ZnO nanoparticles formed in hydroquinone and ZnO sols. The possibility of engineering the band gap and electrical properties of ZnO at nanoscale utilizing an aqueous-based wet chemical synthesis process presented here is simple, versatile, and environmentally friendly, and thus may applicable for making other types of band-gap engineered metal oxide nanostructures with shape-controlled morphologies and optoelectrical properties.

177 citations