Sol-Gel Spin Coating Research Articles

Structural, Optical and Luminescence Properties of ZnO Thin Films Prepared by Sol-Gel Spin-Coating Method: Effect of Precursor Concentration

Transparent zinc oxide (ZnO) thin films are fabricated by a simple sol-gel spin-coating technique on glass substrates with different solution concentrations (0.3–1.2 M) using zinc acetate dehydrate [Zn(CH3COO)2·2H2O] as precursor and isopropanol and monoethanolamine (MEA) as solvent and stabilizer, respectively. The molar ratio of zinc acetate dehydrate to MEA is 1.0. X-ray diffraction, ultraviolet-visible spectroscopy and photoluminescence spectroscopy are employed to investigate the effect of solution concentration on the structural and optical properties of the ZnO thin films. The obtained results of all thin films are discussed in detail and are compared with other experimental data.

Physical Properties of Copper Oxide Thin Films Prepared by Sol–Gel Spin–Coating Method

In this study, copper oxide thin films prepared by the sol–gel method, have been deposed onto glass substrates by the spin coating technique. Our target was to study their properties and improve them for photovoltaic use. These properties were optimized by varying the temperature annealing and the molar concentration of the precursor solutions. The effects of the annealing temperature on the structural and optical properties of the thin films are studied. It was found that the film treated at 550°C shows a higher absorbance. Then by using this optimized temperature, CuO thin films of various molar concentrations, were deposited at the same experimental conditions. The structural analysis by X- ray diffraction (XRD) shows that all the samples are polycrystalline with monoclinic crystal structure. Raman scattering measurements of all thin films confirms the structure of CuO. The optical properties of the films were characterized by UV–Visible–NIR spectrophotometry, which shows that the films show high absorbance in the visible region. Their optical band gap decreases from 3.68 to 2.44 eV when the molar concentration of precursor solutions increases from 0.1 to 0.5 M. The electrical measurements show that the resistivity of the films varies slightly from 84 Ω cm to 124 Ω cm as the molar concentration increases.

Improving the Degradation Resistance and Surface Biomineralization Ability of Calcium Phosphate Coatings on a Biodegradable Magnesium Alloy via a Sol-Gel Spin Coating Method

Bioactive calcium phosphate (CaP) coatings have been applied on biodegradable magnesium (Mg) and its alloys to provide a suitable degradation rate for orthopedic applications. However, the porous CaP coatings formed in the aqueous solution owns poor degradation resistance and thus short in vivo valid life. This paper reports a sol-gel spin coating method to prepare hydroxyapatite (HA, Ca10(PO4)6(OH)2) and fluorine doping HA sealing coatings on a porous CaP coating. The effects of fluorine content on the degradation and biomineralization behaviors of the composite coatings were studied. It reveals that the homogeneous and stable sol-gel coating, especially the fluorapatite coating could significantly improve the degradation resistance and surface biomineralization ability of the porous CaP coating on the Mg alloy.

Characterization of Single Layer ZnO thin Films Prepared by Sol-gel Spin Coating Technique at Different Concentration

Characterization of Single Layer ZnO thin Films Prepared by Sol-gel Spin Coating Technique at Different Concentration

Experimental sol-gel fabrication and theoretical simulation of one-dimensional photonic crystals with a defect state

One-dimensional multilayer structures of the periodically alternating low refractive index (silica) and high refractive index (titania) materials have been deposited by sol–gel spincoating. The possibility of creating an optical filter by introducing a structural defect in the form of a layer of double thickness is shown theoretically and experimentally. All experimental spectra are in agreement with theoretical spectra calculated by transfer matrix method.

Effects of Starting Precursor Ratio on Optoelectrical Properties and Blue Emission of Nanostructured C-ZnS Thin Films Prepared by Spin Coating

Nanocrystalline cubic zinc sulfide (C-ZnS) thin films have been elaborated by sol–gel spin-coating of Zn(Ac)/thiourea starting precursors at different molar ratios, and their structural, morphological, compositional, optical, electrical, and photoluminescence properties comprehensively investigated. x-ray diffraction results showed that the samples had dominant cubic structure and their crystallinity improved with increasing S content. Morphological characterization of the C-ZnS thin films was carried out by field-emission scanning electron microscopy (FESEM), revealing that the films were smooth with spherical grains included in clusters. Energy-dispersive x-ray and Fourier-transform infrared spectra of ZnS compounds did not show any evidence of impurities. Optical characterization revealed increases of the average optical transmittance and bandgap (from 3.2 eV to 3.56 eV) with increasing S content. The refractive index in the visible region increased with the S content, while the extinction coefficient decreased. The compositional dependence of the optical dispersion parameters (oscillator and dispersion energy), dielectric constant, and surface energy loss function of the films was evaluated. Electrical characterization of the films was carried out using Hall-effect measurements. The ZnS thin films exhibited n-type conductivity, and the electrical resistivity decreased with increasing carrier concentration and mobility due to enhanced crystallite size and reduced structural disorder. Photoluminescence (PL) measurements indicated a blue-shift of the near-band-edge emission. The blue emission peaks centered at about 438 nm and 487 nm were enhanced due to transitions involving interstitial S atoms, surface states, and zinc vacancies.

Effect of Annealing Temperature on Structural, Optical, and Electrical Properties of Sol–Gel Spin-Coating-Derived Cu2ZnSnS4 Thin Films

The effect of annealing temperature on structural, optical, and electrical properties of Cu2ZnSnS4 (CZTS) thin films grown on a glass substrate by spin coating sol–gel technique has been studied. Structural study showed that all samples had kesterite crystalline structure. Scanning electron microscopy images showed that the crystalline quality of the samples was improved by heat treatment. Optical study showed that the energy gap values for the samples ranged from 1.55 eV to 1.78 eV. Moreover, good optical conductivity values (1012 S−1 to 1014 S−1) were obtained for the samples. Investigation of the electrical properties of the CZTS thin films showed that the carrier concentration increased significantly with the annealing temperature. The photoelectrical behavior of the samples revealed that the photocurrent under light illumination increased significantly. Overall, the results show that the CZTS thin films annealed at 500°C had better structural, optical, and electrical properties and that such CZTS thin films are desirable for use as absorber layers in solar cells. The photovoltaic properties of the CZTS layer annealed at 500°C were also investigated and the associated figure of merit calculated. The results showed that the fabricated ZnS–CZTS heterojunction exhibited good rectifying behavior but rather low fill factor.

Nanostructure of Al-ZnO Thin Films on ITO/Glass Substrate Prepared via Sol-Gel Spin Coating Process

Solar energy is probably the most important source of renewable energy available today. ZnO is a potential material for the fabrication solar cell. Zinc oxide (ZnO) nano-structure semiconductors have been recently gained much attention in the electronic and optical device applications. ZnO is a compound semiconductor, which has a high extention band gap (E= 3.37 eV) at room temperature (RT) with a Wurtzite crystal structure. In particular ZnO can be employed as the transparent conducting oxide (TCO) in solar cell applications due to its high productivity, non-toxic, low cost, and excellent electrical conductivity. In this study, aluminum doped ZnO (AZO) polycrystalline films have been fabricated on ITO/substrates via a sol-gel spin-coating method. The quantity of aluminum doping in the solution was 4.0 %. After synthesis, the films were pre-heated at 300°C for 25 min and after that the films were inserted in a Tub-furnace and post-annealing at 450°C to 750°C for 1 h. The microstructural and structural properties of AZO films were studied through X-ray diffraction (XRD), UV-Vis NIR and scanning electron microscope (SEM) analysis. The TCO applications of the transmittance of samples were also examined. The results showed that the annealing temperature does not seriously affect on the transmittance of AZO films over the visible range.

Solution-Processed Complementary Resistive Switching Arrays for Associative Memory

Complementary resistive switches (CRS) based on back-to-back nanofilamentary resistive RAM devices have been fabricated by an all-solution-processed method, employing inkjet-printed Ag and Au contacts and a spin-coated sol–gel zirconium oxide dielectric layer. The devices demonstrate electrical switching behavior below 3 V, stable on-state windows, reasonable cycle lifetimes, and can be implemented in $2\times 2$ memory arrays with no crosstalk during addressing. For reliable operation and high yields of the CRS devices, printing and annealing processes were carefully optimized to eliminate the coffeering effect on the bottom electrode, and produce a pin-hole free dielectric. The arrays are fully pulse programmable and are able to retain their state for > $10^{4}$ s. Additionally, the arrays can be operated as associative or content addressable, memory for pattern matching applications, which is demonstrated through a basic hamming distance mapping measurement for different stored data states.

Comparison of Five-Layered ZrO2 and Single-Layered Ce, Eu, and Dy-Doped ZrO2 Thin Films Prepared by Sol-Gel Spin Coating Method

Comparison of Five-Layered ZrO₂ and Single-Layered Ce, Eu, and Dy-Doped ZrO₂ Thin Films Prepared by Sol-Gel Spin Coating Method

Comparison of Pure and Doped TiO2 Thin Films Prepared by Sol-Gel Spin-Coating Method

Comparison of Pure and Doped TiO₂ Thin Films Prepared by Sol-Gel Spin-Coating Method

Effect of Thickness on Micro-Structural and Optical Properties of Al-Doped ZnO Films Prepared by Sol-Gel Spin Coating

Aluminium (Al) doped Zinc oxide (ZnO) thin films of different thicknesses were prepared on glass substrates by sol-gel spin coating method. The effect of thicknesses on micro-structural and optical properties was investigated for transparent conducting oxide (TCO) application in solar cells and other optoelectronic applications. Grazing incidence x-ray diffraction (GIXRD) showed maximum orientation along (002) plane of c-axis. The variation of different structural parameters like crystallite size, micro-strain, c-axis strain, dislocation density as a function of film thickness was investigated. The FTIR spectra confirmed the formation of Al-doped ZnO film. FESEM images showed spherical shaped nanosized grains and formation of micro pores. The optical absorption increased and absorption peak shifted towards longer wavelength (red shift) with increase in the thickness of the film respectively. The optical transmittance of all the films has a transparency of more than 75% in the visible region. The optical band gap (Eg) decreased with increase in the film thickness. The diffused reflectance (DRS) showed very low reflectance in the region of 400-800 nm, but increased in the 800-900 nm region. Photoluminescence (PL) spectra of the prepared films showed intense band edge UV and low intense visible emissions respectively. The effect of thickness of Al-doped ZnO film on micro-structure, surface morphology, optical absorption and transmittance, diffused reflectance and PL have been investigated and the results are reported.

Fabrication of ZnO Thin Films by Sol–Gel Spin Coating and Their UV and White-Light Emission Properties

ZnO thin films have been fabricated by the sol–gel spin-coating technique and annealed under different conditions, and their ultraviolet (UV) and white-light emission properties investigated. Different ambient conditions including oxygen, nitrogen, zinc-rich nitrogen, and vacuum were used to tune the main properties of the ZnO thin films. The resistivity varied from the conductive to semi-insulating regime, and the luminescence emission from fairly intense UV to polychromatic. The emission intensity was also found to be a function of the annealing conditions. Possible routes to compensate the loss of emission characteristics are discussed. X-ray photoelectron spectroscopy (XPS) analysis was carried out to detect the chemical states of the zinc/oxygen species. The changes in the electrical and emission properties are explained based on annihilation/formation of inherent donor/acceptor-type defects. Such ZnO thin films could have potential applications in solid-state lighting.

Optical and Electrical Properties of Copper Doped Nickel Oxide Thin Films by Using Sol-Gel Spin Coating Method

In this present work, we report on optical and electrical properties of Cu-doped NiO thin film were deposited on ITO coated glass substrate by using sol-gel spin coating technique. The grown thin films were characterized by Atomic Force Microscopy, UV visible and impedance measurement. The absorption spectra indicates that a strong absorption peak was found at 356.19 nm and also absorption peak values was increased with the increase in doping concentration of copper. The surface roughness of the thin film was estimated by using AFM. From Nyquist plot and Bode plot it was observed that un-doped NiO films shows higher resistivity than doped NiO films, but with increase in value of dopant concentration resistivity increases.

Characterization of Doped and Undoped Tin Oxide Thin Films Prepared by Sol Gel Spin Coating Technique

Characterization of Doped and Undoped Tin Oxide Thin Films Prepared by Sol Gel Spin Coating Technique

Preparation and Characterization of Ni Added ZnO Thin Film by Sol-Gel Spin Coating Techniques

Preparation and Characterization of Ni Added ZnO Thin Film by Sol-Gel Spin Coating Techniques

Sol-gel derived Al-doped zinc oxide – Reduced graphene oxide nanocomposite thin films

Transparent conductive ZnO films doped with 0–6 mol% of Al3+ (or AZO films) and AZO- rGO (rGO - reduced graphene oxide, ∼0–0.5 g/L) nanocomposite films were deposited on silica glass substrates by sol-gel multilayer spin-coating, with annealing at 250 °C in vacuum. The effects of the processing conditions on the structure, optical and electrical properties of the AZO-rGO films, as well as the AZO thin films for comparison, were investigated by XRD, Raman spectroscopy, TEM and SEM, UV-Vis-NIR spectroscopy, and with the four-point prober and Hall effect measurements. Al3+ ions and rGO sheets existed in the composite films, and both of more Al3+ amount and more rGO could result in worse crystallinity of ZnO. More amount of rGO led to more rGO flakers existed in the surface of the AZO-rGO films. Increasing Al-doping amount could not obviously affect the optical transmittances of the AZO-rGO films, but lead to the UV absorption edge of the films slightly blue-shifted. Optical transmittances of the AZO-rGO films decreased obviously with increasing the rGO ratio, but slightly decreased with increasing the annealing time. The minimum sheet resistance R□ could be obtained when Al-doping amount was ∼2 mol% and rGO ∼0.25 g/L: 50.1 kΩ/□ for the AZO film and 15.2 kΩ/□ for the AZO-rGO film. Addition of rGO could improve the electric conductivity of AZO films. Longer time of vacuum-annealing could also improve the electric conductivity of the AZO-rGO films. For the AZO-rGO film doped with 2 mol% Al3+ and 10 mg rGO after vacuum-annealing for 12 h, Hall mobility was ∼17.7 cm2/Vs and the carrier concentration was ∼10.6 × 1019/cm3.

Optical and Electrical Properties of (002)-Oriented ZnO Films Prepared on Amorphous Substrates by Sol-Gel Spin-Coating

Zinc oxide (ZnO) films were prepared on amorphous quartz substrates by sol-gel spin-coating using Zn(CH3COO)2•2H2O precursor. Isopropanol, ethanol and 2-methoxyethanol were used as solvents. The film drying temperature was kept constant at 200 oC and the annealing temperature was varied from 400 to 800 oC. Highly transparent and (002)-oriented hexagonal wurtzite-type ZnO films were obtained using isopropanol solvent. The ZnO films prepared at Tanneal = 600 oC showed the highest (002) preferential orientation, however it was not the significant feature to achieve low resistivity. The uniform and (002)-oriented ZnO films prepared at Tanneal = 400 oC display the highest transmittance (>93% in the visible region) and the lowest resistivity (7.1 Ω•cm).

Hydrogen Gas Sensing Based on SnO2 Nanostructure Prepared by Sol–Gel Spin Coating Method

A novel H2 gas sensor based on a SnO2 nanostructure was operated at room temperature (RT) (25°C). The SnO2 nanostructure was grown on Al2O3 substrates by a sol–gel spin coating method. The structural characteristics, surface morphology, and gas sensing properties of the SnO2 nanostructure were investigated. Thin film annealing at 500°C produced a high-quality SnO2 nanostructure with a crystallite size of 33.98 nm. A metal–semiconductor–metal gas sensor was fabricated using the SnO2 nanostructure and palladium metal. The gas sensor exhibited a sensitivity of 2570% to 1000 ppm H2 gas at RT. The sensing measurements for H2 gas at different temperatures (RT to 125°C) were repeatable␣for 50 min. Sensor sensitivity was tested under different H2 concentrations (150 ppm, 250 ppm, 375 ppm, 500 ppm, and 1000 ppm) at different operating temperatures. Adding glycerin to the sol solution increased the porosity of the SnO2 nanostructure surface, which increased the adsorption/desorption of gas molecules which leads to the high sensitivity of the sensor. Therefore, this H2 gas sensor is a suitable␣portable␣RT gas sensor.

A Comparative Study on Structural and Optical Properties of ZnO Micro-Nanorod Arrays Grown on Seed Layers Using Chemical Bath Deposition and Spin Coating Methods

In this study, Zinc Oxide (ZnO) seed layers were prepared on Indium Tin Oxide (ITO) substrates by using Chemical Bath Deposition (CBD) method and Sol-gel Spin Coating (SC) method. ZnO micro-nanorod arrays were grown on ZnO seed layers by using Hydrothermal Synthesis method. Seed layer effects of structural and optical properties of ZnO arrays were characterized. X-ray diffractometer (XRD), Scanning Electron Microscopy (SEM) and Ultraviolet Visible (UV-Vis) Spectrometer were used for analyses. ZnO micro-nanorod arrays consisted of a single crystalline wurtzite ZnO structure for each seed layer. Besides, ZnO rod arrays were grown smoothly and vertically on SC seed layer, while ZnO rod arrays were grown randomly and flower like structures on CBD seed layer. The optical absorbance peaks found at 422 nm wavelength in the visible region for both ZnO arrays. Optical bandgap values were determined by using UV-Vis measurements at 3.12 and 3.15 eV for ZnO micro-nanorod arrays on CBD seed layer and for ZnO micro-nanorod arrays on SC-seed layer respectively. DOI: http://dx.doi.org/10.5755/j01.ms.22.4.13443