Effect of oxygen partial pressure on the photoluminescence properties of sol–gel synthesized nano-structured ZnO thin films (original) (raw)
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2022
In this work, the effects of different post-annealing temperatures on the prepared ZnO glass films were studied. The deposited ZnO films were prepared by a sol–gel spin coating technique. The influence of the annealing temperature on the photoluminescent, elemental, optical, structural, crystallite size properties were investigated. The PL spectra show a blue shift in DLE and the intensities of the DLE emission decreased due to the annealing temperature increasing. EDS peaks confirm the successful synthesis of ZnO film. The optical transparency of ZnO films was measured at different annealing temperatures and showed a visible transmittance of 94%. The optical band gap of ZnO film was increased as the annealing temperature increased. The XRD results show the deposited ZnO film has a hexagonal wurtzite structure. Diffraction intensity and crystal size increase with the increase in annealing temperature, while full width at half maxima decreases.
Optical properties of ZnO thin films prepared by sol–gel process
Microelectronics Journal, 2009
Abstract： Nanosized ZnO films were prepared by sol-gel process on quartz substrates. The effects of sol concentration and annealing temperature on the surface morphology, microstructure and optical properties of the films were investigated. The results show that the sols remain stable and usable for spin-coating within 7 d. The ZnO films have a homogeneous and dense surface with grain size about 30 nm. The ZnO thin film annealed at 500 ℃ for 1 h from the sol with Zn concentration of 0.8 mol/L shows an average transmittance of 94% in visible wavelength range. The optical band gaps in ZnO films by various annealing temperatures are from 3.265 eV to 3.293 eV. The violet emission located at 438 nm is probably due to the recombination transitions relating to the interface traps at the grain boundaries.
Comparative Study of ZnO Thin Films Prepared by Different Sol-Gel Route
Acta Physica Polonica A, 2010
The ZnO thin films were prepared from zinc acetate dihydrate as main precursor by using sol-gel method and deposited by drainage and dip coating technique. Four different routes and coating techniques were used for the preparation of samples. The morphology, optical, and structural properties of the sol-gel made ZnO thin films were studied with respect to the preparation of sol-gel route, drainage and dip coating technique. The microstructure of the ZnO thin films and the powders were analyzed by X-ray diffraction. The ZnO thin films prepared in this study were amorphous while its powders were polycrystalline with various diffraction peaks in the X-ray diffraction patterns. The morphology of the film was examined by using scanning electron microscopy. The surface morphology of the ZnO thin films strongly depends on preparation route and deposition technique. The optical characteristics of the samples were obtained by using UV-Visible spectrophotometer at 200-900 nm wavelength. The optical constants (refractive index, extinction coefficient etc.) of the ZnO thin films depend on preparation conditions. The photoluminescence spectra of the ZnO films show the band-edge and sub-band transitions.
Photoluminescence Properties of ZnO Thin Film Prepared by Sol-Gel Route
Applied Mechanics and Materials, 2013
Temperature dependent photoluminescence (PL) properties of ZnO thin film prepared by sol-gel route were investigated. The excitonic-related emission peak at 3.336 eV dominates the spectra, and is attributed to the recombination of excitons bound to structural defects (DBX). Moreover, its thermal activation energy is 5.7 meV obtained by using least-squares fitting method. Compared to its larger localization energy, we propose that there exists a nonradiative relaxation path with energy released during the formation of DBX. The observed peak position of blue emission is in line with theoretical energy interval between the interstitial zinc level and valence band.
UV Photoluminescence of ZnO Nanostructures Based Thin films synthesized by Sol Gel method
2016
During past few decades, Zinc oxide thin films have gained much interest of the researchers, due to its applications in the wide range of fields of optoelectronic devices, photovoltaic, semiconductor lasers and modern LED’s. Selection of proper growth technique for ZnO nanostructures governs several structural and electrical parameters. ZnO shows n-type behavior naturally, donor defects are responsible for emission of UV spectra. ZnO is a wide band gap material with excellent physical properties, good heat conductor, transparent, electron mobility is high and it is non-toxic. Nanostructures based ZnO thin films are prepared using sol-gel and spin coating method. XRD results reveals hexagonal structure of ZnO. Photoluminescence in the utra-violet range maybe due to near-band-edge (NBE) transitions. Ultra violet emissions are observed and can be induced by the band edge recombination of ZnO. This ultra-violet luminescence has origin in free exciton emission. UV luminescence is due to ...
Journal of Colloid and Interface Science, 2014
Zinc oxide (ZnO) thin films were deposited on silicon substrates by a sol-gel method using the spin coating technique. The ZnO films were annealed at 700°C in an oxygen environment using different annealing times ranging from 1 to 4 h. It was observed that all the annealed films exhibited a hexagonal wurtzite structure. The particle size increased from 65 to 160 nm with the increase in annealing time, while the roughness of the films increased from 2.3 to 10.6 nm with the increase in the annealing time.
Photoluminescence studies of ZnO thin films prepared using a laser-assisted sol-gel method
Journal of the Korean Physical Society, 2012
ZnO thin films were grown on Si(100) substrates by using a laser-assisted sol-gel method involving irradiation from a 325-nm He-Cd laser. In contrast to conventionally-synthesized sol-gel ZnO thin films, the surfaces of those grown using the laser-assisted sol-gel method were much smoother. The optical properties of the ZnO thin films were investigated using temperature-dependent photoluminescence (PL). In the room-temperature PL spectra, the intensity of the blue-green emission was dramatically decreased by laser irradiation during the stages of deposition and post-heat treatment. Moreover, the full width at half maximum of the near-band-edge emission peaks was decreased by the laser irradiation. The activation energy of the laser-assisted sol-gel ZnO thin films was determined to be ∼99 meV, and the values of the fitting parameters α and β for Varshni's empirical equation were 4 × 10 −3 eV/K and 4.9 × 10 3 K, respectively. Another fitting based on the thermal broadening effect of the excitonic emission peak revealed a decreased exciton-phonon interaction in the laser-assisted ZnO thin films.
ZnO nanoparticles (ZnO–NPs) were synthesized using sol–gel method. The structural and optical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL). In this study, the effects of annealing temperature on photoluminescence (PL) of ZnO-NPs were studied. ZnO was annealed at various temperatures between 500 and 800 °C. The X-ray diffraction (XRD) results demonstrated that grain size increased with increase of annealing temperature. The average size of the nanoparticles was determined by SEM as well as XRD data and found to be 50 nm after annealing at 800 °C. As the annealing temperature increased from 500 to 800 °C, the intensities of both UV peak and that of green luminescence (GL) enhanced monotonously. The enhancement in the UV peak intensity is attributed to the decrease of grain boundaries and surface states; whereas, the remarkable improvement in the GL is assigned to the out-diffusion of oxygen from the sample up to 800 °C. It supports that GL is induced by the singly ionized oxygen vacancies. These oxygen vacancies are saturated due to the finiteness of the defects at 800 °C.
Characterization of thin films of ZnO prepared by sol-gel processes
18th European Frequency and Time Forum (EFTF 2004), 2004
Thin films of ZnO have been grown using sol-gel technique. The precursor materials for sol preparation include zinc acetate or zinc nitrate. Characterization was done using optical absorption, ellipsometry, X-ray diffraction, photoluminescence and scanning electron microscopy.
Pramana, 2011
Zinc oxide nanothin films were prepared on glass substrate by sol-gel dip-coating method using zinc acetate dihydrate, methanol, and monoethanolamine as precursor, solvent, and stabilizer, respectively. The relationship between drying conditions and the characteristics of ZnO nanocrystalline films (c-axis orientation, grain size, roughness and optical properties) was studied. The films were dried in an oven at different temperatures and by IR radiation. Then, the films were annealed at 500 • C in a furnace. The chemical composition, transmission spectra, structure, and morphology of the samples were studied using infrared (IR) and UV-visible spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM), respectively. The XRD results show that the drying conditions affect the orientation of crystallization along the (0 0 2) plane. AFM images show that the thicknesses of the films decrease from 128 to 93 nm by changing the drying conditions. The photoluminescence (PL) of ZnO nanothin films shows the UV emission at near band edge and broad green radiation at about 465 nm wavelength.