Electrochemical deposition of ZnO film and its photoluminescence properties (original) (raw)
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Investigation of Chemical Bath Deposition of ZnO nanocrystals Thin Films Using Different ZnNO3
Archives of Materials Science and Engineering
In this work, thin films growth at different ZnNO 3 concentrations: 0.02 M, 0.03 M and 0.04 M by chemical bath deposition (CBD) as-prepared on glass substrates at 80 °C ± 2 °C. Patterns Diffraction x-ray (DRX) shown peaks 2θ = (31.72, 32.769, 34.36, 36.10, 47.44, 56.52, 62.78, 67.84 and 69.02), at concentration 0.02 M show formation from hydrozincite [Zn 5 (CO 3 ) 2 (OH) 6 ]. The optical band gap shifts from 3.8 eV to 3.6 eV. Photoluminescence (PL) spectra show intensity variation of the green emission (GE) may be resulted from variation of the intrinsic defect in ZnO films, such zinc vacancy (V Zn ), oxygen vacancy (V O ), and interstitial zinc (Zn i ), interstitial oxygen (O i ). The presence of defects in our samples is responsible for the observed broad visible PL bands; this indicates reductions of oxygen vacancies and increase of oxygen interstitials. It could be believed that the presence of defects in samples is responsible for the observed broad visible PL band. The concentration increased the visible defect luminescence, which might be due to improvement to sample stoichiometric. The presence of both green emission (GE) and yellow emission (YE) can be seen through the deconvolution of the defect increasing the concentration, the position of the GE shifted from 1.96-2.45 eV and the increase of its intensity. The shifts of these two visible PL bands might be due to changes in local environments of the defects centers in samples due to increased concentration. Therefore, the GE relate to donor levels dominated due to increase of oxygen vacancies. ZnO is an n-type semiconductor and it means that most defects are Zn interstitials and oxygen vacancies. Raman spectra showed increase of the 437 cm -1 (E 2 mode) peak intensity due concentration 0.4 M. environmental problems are becoming more and more serious with the development of industry and economy. Thus, improving the stability of ZnO without sacrificing its efficiency represents very attractive scientific and technological problems to be solved. Metal-oxide thin films (especially, wide and direct band gap semiconductors) are of great interest in optical and electronical industries, including and ultraviolet (UV) optical devices, such as light-emitting diodes and laser diodes. Semiconducting ZnO thin films have been prepared by a wide range of methods: electrodeposited [3], thermal oxidation of ZnS thin films [4], hydrothermal technique . However,
Applied Surface Science, 2010
The development of cost-effective and low-temperature synthesis techniques for the growth of highquality zinc oxide thin films is paramount for fabrication of ZnO-based optoelectronic devices, especially ultraviolet (UV)-light-emitting diodes, lasers and detectors. We demonstrate that the properties, especially UV emission, observed at room temperature, of electrodeposited ZnO thin films from chloride medium (at 70 8C) on fluor-doped tin oxide (FTO) substrates is strongly influenced by the post-growth thermal annealing treatments. X-ray diffraction (XRD) measurements show that the films have preferably grown along (0 0 2) direction. Thermal annealing in the temperature range of 150-400 8C in air has been carried out for these ZnO thin films. The as-grown films contain chlorine which is partially removed after annealing at 400 8C. Morphological changes upon annealing are discussed in the light of compositional changes observed in the ZnO crystals that constitute the film. The optical quality of ZnO thin films was improved after post-deposition thermal treatment at 150 8C and 400 8C in our experiments due to the reducing of defects levels and of chlorine content. The transmission and absorption spectra become steeper and the optical bandgap red shifted to the single-crystal value. These findings demonstrate that electrodeposition have potential for the growth of high-quality ZnO thin films with reduced defects for device applications.
Physica B: Condensed Matter, 2007
High energy electron irradiation (HEEI) effects on the as-grown and annealed ZnO thin films grown by electrochemical deposition were investigated. Both samples were exposed to the sequential electron irradiations of 6, 12 and 15 MeV energies at a fluence of 1 Â 10 12 e À /cm 2 . The results of X-ray diffraction suggest that a highly strong crystallographic structure can be produced by annealing process. Photoluminescence (PL) studies show that the EI produces violet emission which results from the zinc interstitial. Recombination lifetime (RL) values of the both films reveal that the high quality crystals are obtained. The decreasing trends of RL values with increasing electron energy have been explained by the formation of crystal defects due to the HEEI.
Research on Chemical …
Zinc oxide thin films have been deposited on glass substrates by the chemical bath deposition method; a surfactant, cetyltrimethylammonium bromide (CTAB); was used as capping agent. The films were annealed at two different temperatures: 200 and 300°C. The structural features were investigated by X-ray diffraction analysis which exhibited hexagonal wurtzite structures along with c-axis orientations. Crystallite size was estimated and found to be around 33-41 nm. The effect of post-deposition thermal annealing on the morphological and optical properties has been investigated by scanning electron microscopy and photoluminescence spectra at room temperature. The band gap energies of uncapped and CTAB-capped ZnO films were found to be 3.28 and 3.48 eV, respectively.
ZnO is a wide band-gap (3.37 eV) II–VI compound semiconductor with hexagonal wurtzite structure. These films were deposited by electrodeposition technique, containing very low concentrations of sodium citrate and 30% hydrogen peroxide. Ammonium hydroxide is added to control the reaction. The structural, compositional, Surface morphology and optical analysis were studied by X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), Scanning Electron Microscope (SEM), and Atomic Force Microscopy (AFM).The hexagonal structure of ZnO (101) is observed with average grain size 48nm. The average RMS surface roughness of the film is observed to be 328.621nm. The bandgap of the ZnO film is observed to be 3.35 eV. The strong peak of ZnO at 381 nm is observed in photoluminescence spectroscopy.
Effective Annealing of ZnO Thin Films Grown by Electrochemical Deposition Technique
Turkish Journal of Physics
Wide and direct band gap ZnO thin films have been grown on conductive indium-tin-oxide (ITO) substrates by electrochemical deposition (ECD) technique using different growth parameters. High quality films in terms of crystallographic and optical characteristics have been obtained under a cathodic potential of-0.9 V; a pH of 5.2, using 0.1 M Zn(NO 3)2 solution. Oxygen gas flow through the solution increased the growth rate and the quality of samples. Subsequent heat treatments at various temperatures for 30 minutes under dry N 2 gas flow show that the most suitable annealing temperature is 300 • C for these electrochemically deposited thin films on ITO. X-ray diffraction (XRD) measurements show that the samples have preferably grown along the direction of (101) and that the annealing at 300 • C caused an increase in the peak intensity belonging the (101) surfaces. The Atomic Force Microscopy (AFM) measurements revealed that the annealing process improved the surface quality of the samples. It has also been observed from the absorption measurements that the band-gap is enhanced from 3.23 to 3.37 eV after this certain heat treatment.
Emission, Defects, and Structure of ZnO Nanocrystal Films Obtained by Electrochemical Method
Thin Film Processes - Artifacts on Surface Phenomena and Technological Facets, 2017
ZnO nanocrystal (NC) films, prepared by electrochemical etching with varying the technological routines, have been studied by means of photoluminescence (PL), scanning electronic microscopy (SEM), energy dispersion spectroscopy (EDS), Raman scattering, and X ray diffraction (XRD) techniques. Raman and XRD studies have confirmed that annealing stimulates the ZnO oxidation and crystallization with the formation of wurtzite ZnO NCs. The ZnO NC size decreases from 250-300 nm down to 40-60 nm with increasing the etching time. Two PL bands connected with the near-band edge (NBE) and defect-related emissions have been detected. Their intensity stimulation with NC size decreasing has been detected. The NBE emission enhancement is attributed to the week quantum confinement and exciton-light coupling with polariton formation in small ZnO NCs. The luminescence, morphology, and crystal structure of ZnO:Cu NCs versus Cu concentration have been investigated as well. The types of Cu-related complexes are discussed using the correlation between the PL spectrum transformations and XRD parameters. It is shown that the plasmon generation in Cu nanoparticles leads to the surface enhanced Raman scattering (SERS) effect and to PL intensity increasing the defect-related PL bands. The comparison of ZnO and ZnO:Cu NC emissions has been done and discussed.
Applied Surface Science, 2011
A simple and inexpensive spray pyrolysis technique (SPT) was employed for the synthesis of nanocrystalline zinc oxide (ZnO) thin films onto soda lime glass and tin doped indium oxide (ITO) coated glass substrates at different substrate temperatures ranging from 300 °C to 500 °C. The synthesized films were polycrystalline, with a (0 0 2) preferential growth along c-axis. SEM micrographs revealed the uniform distribution of spherical grains of about 80–90 nm size. The films were transparent with average visible transmittance of 85% having band gap energy 3.25 eV. All the samples exhibit room temperature photoluminescence (PL). A strong ultraviolet (UV) emission at 398 nm with weak green emission centered at 520 nm confirmed the less defect density in the samples. Moreover, the samples are photoelectrochemically active and exhibit the highest photocurrent of 60 μA, a photovoltage of 280 mV and 0.23 fill factor (FF) for the Zn450 films in 0.5 M Na2SO4 electrolyte, when illuminated under UV light.► Synthesis of nanocrystalline ZnO thin films onto glass and ITO coated glass substrates by SPT. ► The substrate temperature dependent properties of ZnO thin films were investigated. ► The sample deposited at 450 °C shows the better photoelectrochemical performance.
Materials Science-Poland, 2019
An aqueous colloidal solution was prepared at 80 °C and pH = 9 from suitable chemical compounds to produce zinc oxide (ZnO) crystals and thin films. The ZnO crystals were grown in the colloidal solution under special conditions. Their micrographs showed ZnO rods with hexagonal structure. The number of the rods, increased over time. The ZnO thin films were produced on glass substrates in the same colloidal solution using the chemical bath deposition (CBD) method in different deposition times. The produced films were post-annealed for about one hour at 400 °C. Crystalline structure, phase transitions and nanostructure of the films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). ZnO wurtzite structure was dominant, and by increasing the deposition time, the films became more crystalline. Nanostructure of the films changed from rod to wire and transformed into pyramid-like structures. Also, morphology of the films chang...