Deposition of silica thin films formed by sol–gel method

Deposition of silica thin films on silicon wafer was investigated by in situ mass measurements with a microbalance configured for dip coating. Mass change was recorded with respect to deposition time when the substrate was fully immersed in the silica sol. Mass gain during deposition was higher than predicted from monolayer coverage of silica nano particles. This implied that deposition was facilitated by gelling of the nanoparticles on the substrate. The rate of deposition was enhanced by increasing the particle concentration in the sol and by decreasing the particle size from 12 to 5 nm. Increasing the salt concentration of the silica sol at constant pH enhanced the deposition of the silica particles. Reducing the pH of the sol from 10 to 6 decreased the deposition rate due to aggregation of the primary silica particles.     

Synthesis and characterization of tellurium-doped CdO nanoparticles thin films by sol–gel method

In this work, tellurium (Te) doped CdO nanoparticles thin films with different Te concentrations (1, 3, 5, 7 and 10 %) were prepared by sol–gel method. The effects of Te doping on the structural, morphological and optical properties of the CdO thin films were systematically studied. From X-ray diffraction spectra, it has seen that all of thin films were formed polycrystalline and cubic structure having (111), (200) and (311) orientations. The structure of CdO thin films with Te-dopant was formed the unstable CdTeO₃ monoclinic structure crystal plane ( $ {\bar{\text{1}}\text{22}} $ 1 ¯ 22 ), however, the intensity of this unstable peak of the crystalline phase decreased with the increase of Te-doping ratio. The strain in the structure is also studied by using Williamson-Hall method. From FE-SEM images, it has seen that particles have homogeneously distributed and well hold onto the substrate surface. Additionally, grain size increases from 27 to 121 nm with the increase of Te-doping ratio. Optical results indicate that 1 % Te-doped CdO thin film has the maximum transmittance of about 87 %, and the values of optical energy band gap increases from 2.50 to 2.64 eV with the increase of Te-doping ratio. These results make Te-doped CdO thin films an attractive candidate for thin film material applications.     

Effect of annealing temperature on the quality of Al-doped ZnO thin films prepared by sol–gel method

The different thermal expansion coefficients and lattice mismatch between ZnO and Al may produce residual stress in Al-ZnO (AZO) thin films. Annealing processes can be applied to modulate this residual stress. In this study, three different rapid thermal annealing (RTA) temperatures (350, 450, and 600 °C) were applied to an AZO thin film, prepared using sol–gel method. The mechanical properties, optical properties, and structure of the AZO thin film were investigated experimentally. The results show that increasing the RTA temperature increased the Young’s modulus and hardness of the films. The grain size of the films also increased with increasing RTA temperature. However, the film thickness and shear stress component decreased with increasing RTA temperature. Both compressive and tensile stress decreased gradually with increasing film thickness after RTA treatment. It was demonstrated that the use of a relatively high RTA temperature can effectively relax the residual stress in AZO thin films.     

Preparation of nanostructured titania thin films by sol–gel technology

This study is concerned with the preparation of hydrolytically active heteroligand complex [Ti(OC₄H₉)_3.61(O₂C₅H₇)_0.39] from titanium butoxide and acetylacetone and with the gel formation kinetics in a solution of this complex upon hydrolysis and polycondensation. Single-layer and double-layer thin films of a solution of this precursor were coated on polished silicon substrates using the dip-coating method. The crystallization of nanostructured titania films during the heat treatment of these xerogel coatings was studied using various protocols; the anatase–rutile phase transition temperature was found to depend on the film thickness. The effects of the precursor solution viscosity on the film thickness and crystallite size were determined.     

Transparent conductive tungsten-doped tin oxide thin films synthesized by sol–gel technique on quartz glass substrates

Transparent conductive tungsten-doped tin oxide (SnO₂:W) thin films were synthesized on quartz glass substrates by sol–gel dip-coating method. It was found that the films were highly transparent and the average optical transmission was about 90% in the visible and near infrared region from 400 to 2,500 nm. The optical band gap is about 4.1 eV. The lowest resistivity of 5.8 × 10^?3 ohm cm was obtained, with the carrier mobility of 14.2 cm² V^?1 s^?1 and carrier concentration of 7.6 × 10¹⁹ cm^?3 in 3 at.% W-doping films annealed at 850 °C in air. The structural properties, surface morphology and chemical states for the films were investigated.     

Antibacterial glass films prepared on metal surfaces by sol–gel method

This paper describes the preparation and characterization of glass films consisting of SiO₂, Li₂O, Na₂O, K₂O or MgO in varying compositions on stainless steel and aluminum substrates by sol–gel method. Silver phosphate or silver incorporated zeolite was also introduced into the sols for obtaining antibacterial effect. The SiO₂/Li₂O/Na₂O system having the composition of 85:5:10 wt% was found as the optimum for obtaining a stable sol and film formation. The films were investigated by scanning electron microscopy (SEM) and electron dispersive analysis by X-ray (EDX), Fourier transformed infrared (FTIR) spectroscopy, thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA). Homogenous films having 300 ± 20 nm thicknesses were formed by spin coating and then by curing at 500 °C for 1 h. Obtained films had high adherence to the metal substrates and they were also durable in acidic, basic or NaCl environments. They also presented a powerful antibacterial effect against E. coli.     

Atomic oxygen erosion resistance of sol–gel oxide films on Kapton

Silica, alumina and silica-alumina composite films were deposited on Kapton substrate via sol–gel method and their atomic oxygen (AO) erosion resistance was test in a ground-based AO simulator. The surface morphology and the structure of as-deposited films were investigated by scanning electronic microscope, X-ray photoelectron spectroscopy, and Fourier transformed infrared spectroscopy. After AO exposure, more cracks and micro-pores appear on the surface of silica and alumina films, respectively. For the silica-alumina composite films, their toughness and densification are good, and the stable interface is formed between the alumina and silica phases. Therefore, the silica-alumina composite-coated Kapton shows the best AO resistance and the erosion yield is two orders of magnitude less than that of pristine Katpon. Moreover, the composite-coated Kapton remains optically stable under AO exposure.     

Synthesis and characterization of lead oxide nano-powders by sol–gel method

Our goal in this research was to obtain lead oxide nano-powders by sol–gel method. In this method, lead oxide nano-powders were synthesized through the reaction of citric acid (C₆H₇O₈·H₂O) solution and lead acetate [Pb(C₂H₃O₂)₂] solution as stabilizer and precursor, respectively. The effect of different parameters including calcination temperature, (molar ratio of citric acid to lead acetate) and drying conditions were investigated. The prepared lead oxide nano-powders were characterized by FT-IR spectroscopy, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The prepared PbO samples consist of the particles in the range of 50–120 nm or the thick plate like structures with thickness of 53 nm depending on the drying conditions.     

Synthesis and characterization of nanocrystalline tin oxide by sol–gel method

Nanocrystalline SnO₂ particles have been synthesized by a sol–gel method from the very simple starting material granulated tin. The synthesis leads a sol–gel process when citric acid is introduced in the solution obtained by dissolving granulated tin in HNO₃. Citric acid has a great effect on stabilizing the precursor solution, and slows down the hydrolysis and condensation processes. The obtained SnO₂ particles range from 2.8 to 5.1 nm in size and 289–143 m² g⁻¹ in specific surface area when the gel is heat treated at different temperatures. The particles show a lattice expansion with the reduction in particle size. With the absence of citric acid, the precursor hydrolyzes and condenses in an uncontrollable manner and the obtained SnO₂ nanocrystallites are comparatively larger in size and broader in size distribution. The nanocrystallites have been characterized by means of TG-DSC, FT-IR, XRD, BET and TEM.     

Influence of the spin acceleration time on the properties of ZnO:Ga thin films deposited by sol–gel method

Journal of Sol-Gel Science and Technology - A detailed study of the structural, morphological, optical, and electrical properties of the spin-coated Ga-doped ZnO (GZO) films in which these...     

Photocatalytic and antibacterial activities of Ag-doped ZnO thin films prepared by a sol–gel dip-coating method

Silver-doped ZnO thin films with various loadings of Ag in the range of 0–10 mol% were prepared by the sol–gel dip-coating method. All prepared films show X-ray powder diffraction patterns that matched with ZnO in its würtzite structure. The grain size decreased as the Ag loading increased. The prepared films, under UV blacklight illumination, produced a photocatalytic degradation of methylene blue, rhodamine B and reactive orange solutions. Furthermore, they inhibited the growth of Escherichia coli bacteria under UV blacklight irradiation and to a lesser extent in dark conditions. The photocatalytic and antibacterial activities of the prepared films increased with Ag loading, presumably because Ag enhanced the efficiency of generation of superoxide anion radicals (^•O₂ ⁻) and hydroxyl radicals (^•OH).     

Microstructure and performance of AZO thin films prepared by sol–gel processing

Al-doped zinc oxide (AZO) films were prepared by a wet-chemical coating technique, their microstructure and crystal growth were characterized as a function of the single layer thickness. When similar final thicknesses are attained by more multiple subsequent coating-firing cycles, film porosity is reduced from over 14 to 2 %. Simultaneously the AZO crystallite size is increased from approximately 23 to 60 nm, a preferential c-axis oriented growth is observed. Different substrates (soda-lime glass, soda-lime glass with a SiO₂ barrier coating, borosilicate glass and alkali-free display glass) were used and the resulting AZO films were compared. It is found that the substrate composition primarily affects grain growth and subsequently the electrical performance of the AZO films.