Sol-gel Spin-coating Technique Research Articles

Sol-Gel Spin Coated Transparent Single-TiO2 and SiO2 Thin Film on Glass for Opto-electronic Applications

Great attention has been given on the sol-gel synthesis and spin-coating deposition techniques for the fabrication of various thin films. Because of its simple technique to fabricate dielectric (metal oxide) films using tetraethyl orthosilicate and titanium isopropoxide precursors. In this work, transparent single layer of SiO2 and TiO2 thin film was deposited on a glass substrate and characterized by  FTIR, UV-visible spectroscopy, fluorescence and scanning electron microscopy techniques. The single layer thin film was mechanically  stable and strong by adhering to glass substrates. The FTIR transmittance spectrum evidenced the existence of Si-O-Si and Ti-O-Ti at  ~1100 and 1400 cm-1. The UV-visible absorbance spectra of single layer of SiO2 and TiO2 thin films showed strong absorption at below  00 nm. The excitation wavelength at 380 nm, the fluorescence spectra of both thin films showed the highest emission spectrum  in between 733-798 nm. The SEM studies confirmed the smooth surface in both SiO2 and TiO2 layers. Further, it could be useful for  various applications such as back reflector in solar cells, anti-reflection coatings, hydrophobic and anti-fogging materials. 

Changing the Ca2+ ion ratio to modulate the temperature coefficient of resistivity (TCR) of La1-xCaxMnO3 films prepared by the sol-gel spin coating method

Perovskite manganese oxides are highly desirable for infrared acquisition owing to their characteristics of ferromagnetic metal-paramagnetic insulators. In this work, the sol-gel spin-coating technique was employed to prepare La1-xCaxMnO3 (LCMO) films with varying Ca2+ content (x = 0.1, 0.2, 0.3, 0.4, 0.5) on the (l00) LaAlO3 (LAO) substrates. In comparison to previous studies, the pre-sintering temperature, final sintering temperature, and final sintering period were modified. The crystal structure, surface topography, elemental valence states, and electrical transport performance of the LCMO films were characterized and analyzed as well. The results demonstrated that the diffraction peaks of the above films were aligned with those of the LAO single-crystal substrate. The change in Ca2+ content caused an increase in the Mn–O bond length, the amount of Mn4+, and the Mn–O–Mn angle in LCMO films, promoting the double exchange effect. These modifications had a considerable impact on the resistivity of LCMO films, increasing their TCR value. The maximum TCR of 22.92% K−1 was reached at x = 0.3 and peak TCR temperature (Tk) of 241.93 K. Therefore, the film has great application potential for infrared bolometers.

The Impact of Spinning Speed on n-TiO2/ZnO Bilayer Thin Film Fabricated through Sol–Gel Spin-Coating Method

The spinning speed parameter plays a crucial role in determining the properties of an n-TiO2/ZnO bilayer thin film fabricated using the sol–gel spin-coating technique, especially for solar cell applications. In this study, various spinning speeds were employed on an n-TiO2/ZnO bilayer thin film, and characterizations were conducted, such as morphological, structural, and optical properties. The findings revealed that the optimal conditions for the thin film were achieved at a spinning speed of 3000 rpm. Under this condition, a homogenous and compact surface morphology was observed, with an even distribution of ZnO grains. The successful fabrication of an n-TiO2/ZnO bilayer thin film was confirmed by the presence of characteristic peaks for both TiO2 and ZnO. Obviously, three dominant ZnO orientation peaks, which included (100), (002), and (101) were identified. The prevalence of the (002)-ZnO orientation plane indicated a high-quality structure with excellent crystallinity. In terms of optical properties, the achievement of high transmittance up to 75% resembles the high transparency of the thin film. The optical energy of the n-TiO2/ZnO bilayer thin film is estimated at 3.10 eV. In summary, the spinning speed parameter played a pivotal role in enhancing various properties of the thin film, making it a significant factor in its development for diverse applications.

Substitution effects on physical and chemical properties of Cu2Fe1-xCoxSnS4 thin films synthesized by the sol-gel technique

The impact of iron and cobalt substitution on the structural, morphological and optical properties of the copper iron cobalt tin sulfide Cu2Fe1-xCoxSnS4 thin films was studied. Employing the simple and easy sol-gel spin-coating technique on soda-lime glass substrates without sulfurization phase, Cu2Fe1-xCoxSnS4 (x = 0, 50 and 100%) compound was formed with the (112) preferential orientation for all thin films in the tetragonal stannite structure at space-group I42 m. By performing X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy, Energy Dispersive analysis and UV–Vis–NIR spectrophotometry, the physical and chemical properties were examined. The substitution was observed to provide a slight variation of the lattice parameters. The crystallite size was found to vary between 14 and 32 nm and decreased by increasing the cobalt content. The Raman spectra confirm the result of the XRD via the appearance of two peaks located at 321 and 284 cm−1, corresponding to the A1 vibration mode. The morphological analysis showed homogenous film surfaces. Optical characterizations showed that all thin films exhibit a band-gap energy, estimated between 1.1 and 1.53 eV, with an absorption coefficient greater than 104 cm−1. The possible use of thin films as an absorber for solar cells, with an adjustable optical band gap is proven.

Effect of Al-doping on morphology, structure, and optical band gap of ZnO thin films synthesized by sol–gel spin-coating technique

Effect of Al-doping on morphology, structure, and optical band gap of ZnO thin films synthesized by sol–gel spin-coating technique

Improved transparent conductive properties of highly c-axis oriented ZnO thin films upon (Ga, Mg) co-doping

The paper reports the growth and characterization of highly c-axis oriented ZnO thin films and their physical properties upon (Ga, Mg) co-doping. The films were produced on glass substrates by sol-gel spin-coating technique. X-ray diffraction (XRD) patterns of all the films reveal the presence of a hexagonal wurtzite crystal structure of ZnO with a c-axis preferred orientation and crystallite sizes in the range of 28–50 nm. Surface morphological studies reveal the granular morphology of the films. The optical transparency in the visible region increases upon doping and co-doping with a maximum (>95%) for the (1 at% Ga +3 at % Mg) co-doped ZnO thin film (assigned with code name 1G3MZO). The band gap is blue-shifted upon co-doping and found to be a maximum of 3.32 eV for the 1G3MZO film. The electrical conductivity improves upon co-doping, and an optimum value of 70.3 (Ω-cm)−1 is obtained in the 1G3MZO film. It has been concluded that the 1G3MZO film has improved transparent conductive properties and, therefore, finds application in optoelectronic devices.

Investigation of the structural and temperature-dependent electrical properties of MZnO (M = Ce and Sm) Schottky diode devices fabricated using the sol–gel spin-coating technique

In the present study, the Schottky diode devices based on Ce and Sm co-doped ZnO thin films were fabricated using the sol–gel spin-coating technique with Pd and Pt as Schottky contacts. The structural and electrical properties of the fabricated Schottky diode devices were investigated at room temperature and in the temperature range of 320–160 K. The crystalline structure of the prepared films was studied using X-ray diffraction spectroscopy. The I–V characteristics of the fabricated Schottky diode devices based on Pd and Pt Schottky contacts manifest good diode behavior with the rectification of nine and ten orders of magnitudes, respectively. The ideality factor for Pd-based Schottky diode was found to decrease with temperature, and the lowest value obtained at 160 K was 1.3, while for the Pt-based Schottky diode, the ideality factor was found to increase with decreasing temperature. Moreover, by using two Gaussian models, the barrier height for Pt Schottky diodes was found to decrease with decreasing temperature indicating the inhomogeneity in the barrier height. Furthermore, alongside the thermionic emission theory, the fabricated Schottky diode parameters were also analyzed with Cheung–Cheung and the modified Nord methods. Finally, the current transport mechanism in both fabricated Pd and Pt was found to be controlled by an Ohmic, trap-filled voltage and space-charge-limited current mechanisms in the low, moderate and higher voltage bias, respectively.

Indium and hafnium chloride modified titanium oxide thin films

Titanium oxide (TiO2) thin films were prepared by the sol-gel spin-coating technique. The influences of indium (In), hafnium (Hf), and In&Hf doping on electrochemical and structural properties were investigated. The structural properties of undoped and doped TiO2 were investigated using thermogravimetric/differential thermal (TG/DTA), X-ray Powder Diffraction (XRD), and atomic force microscopy (AFM). The optical properties were investigated using ultraviolet–visible (UV–Vis) spectroscopy, and band gap energies were calculated using the Tauc method from transmission measurement. The results showed that TiO2 had better electrochemical properties, and the band gap increased with In&Hf doping.

Optical investigation of sol–gel-synthesized and spin-coated SiO2/TiO2 multilayers

In this work, silicon dioxide (SiO2)/titanium dioxide (TiO2) multilayer films were deposited on silicon substrates through the sol–gel spin-coating technique using the precursors titanium butoxide and tetraethyl orthosilicate. After the preparation, the various optical and morphological properties of the films were studied by using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and ultraviolet–visible (UV–Vis) spectroscopy. The XRD patterns showed intense diffraction peaks, which were found to correspond to anatase titanium dioxide and it matched well the standard Joint Committee on Powder Diffraction Standards file. The crystallite sizes of the prepared samples were calculated as 24 nm for three stacks of silicon dioxide/titanium dioxide thin films and 30 nm for five stacks of silicon dioxide/titanium dioxide thin films using Debye–Scherrer’s formula. The FTIR transmittance spectra confirmed Si–O–Ti vibrational modes at 800 and 960 cm−1 with related functional groups. A reflectance of 86% was measured by using UV–Vis spectroscopy. These dielectric multipliers will be useful in solar cells as backside reflectors for an improved light-harvesting mechanism.

Spectroscopic Studies of CdS Nanocrystalline Thin Films Synthesized by Sol–Gel Spin Coating Technique for Optoelectronic Application: Influence of Co-Doping

Spectroscopic Studies of CdS Nanocrystalline Thin Films Synthesized by Sol–Gel Spin Coating Technique for Optoelectronic Application: Influence of Co-Doping

Effects of annealing temperature on the phase formation, optical, photoluminescence and magnetic properties of sol-gel YFeO3 films

YFeO 3 (YFO) thin films were deposited onto quartz substrates via sol-gel spin-coating technique and annealed at different temperature ranged between 650 and 900 °C. The impact of annealing temperature on the phase formation, microstructural, optical, photoluminescence (PL) and magnetic properties of the films were systematically investigated. X-ray diffraction analysis revealed an amorphous structure in film annealed at 650 °C and formation of hexagonal-YFO ( h -YFO) phase in films annealed at 750–800 °C. The films annealed at 850–900 °C exhibited an orthorhombic-YFO ( o -YFO) structure. Atomic force microscopy images of h -YFO films showed homogeneous surface with uniform particles size and shape. The particle size increased and had irregular shape in o -YFO films. The average particle size was 44 and 117 nm, while the root square roughness was 1.38 and 2.55 nm for h - and o -YFO films annealed at 750 and 850 °C, respectively. The optical band gap ( E g ) was 2.53 and 2.86 eV for h - and o -YFO films annealed at 750 and 850 °C, respectively. The PL spectra of h -YFO films were red-shifted compared with that of o -YFO films. The PL emission related to near band edge was observed at 459.0 and 441.9 nm for h - and o -YFO films annealed at 750 and 850 °C, respectively. The magnetization was enhanced with the increasing of annealing temperature and has the value of 4.8 and 12.5 emu/cm 3 at 5000 Oe for h - and o -YFO films annealed at 750 and 850 °C, respectively.

EFFECT OF OPERATING TEMPERATURE ON THE PERFORMANCE OF RELAXOR-FERROELECTRIC PLZT FILMS-BASED POWER ENERGY-STORAGE DEVICES

Thermal stability is a key factor to determine the applicability of dielectric capacitors in the power energy-storage devices. The effects of operating temperature on the polarization hysteresis, energy-storage performance, and charge-discharge cycling stability of thin-film capacitors have been revealed in this study by investigating the relaxor Pb0.92La0.08(Zr0.52Ti0.48)O3 (PLZT) thin film grown on Pt/Ti/SiO2/Si substrates using a sol-gel spin-coating technique. The PLZT thin films demonstrate good thermal stability of polarization hysteresis and outstanding energy storage properties over a wide temperature range from room temperature to 150C. With increasing operating temperature up to 200C, the polarization hysteresis loops gradually become more slanted and slightly broaden. The fluctuation in recoverable energy density is less than 8%, and the change of energy-storage efficiency is less than 12% at 200C, which may be associated with the high dynamic polar nanoregions (PNRs) in relaxor ferroelectrics. At room temperature, PLZT thin film shows an excellent charge-discharge cycling life with fatigue-free performance after 1010 cycles in both discharge energy-storage density and energy-storage efficiency. However, the reduction of discharge energy-storage density and energy-storage efficiency, performed at an operating temperature of 200C, is about 18% after 1010 charge-discharge cycles. All these results suggest that such PLZT thin film capacitors are very attractive for energy-storage applications operating under high-temperature conditions.

Elaboration of Highly Modified Stainless Steel/Lead Dioxide Anodes for Enhanced Electrochemical Degradation of Ampicillin in Water

Lead dioxide-based electrodes have shown a great performance in the electrochemical treatment of organic wastewater. In the present study, modified PbO2 anodes supported on stainless steel (SS) with a titanium oxide interlayer such as SS/TiO2/PbO2 and SS/TiO2/PbO2-10% Boron (B) were prepared by the sol–gel spin-coating technique. The morphological and structural properties of the prepared electrodes were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). It was found that the SS/TiO2/PbO2-10% B anode led to a rougher active surface, larger specific surface area, and therefore stronger ability to generate powerful oxidizing agents. The electrochemical impedance spectroscopy (EIS) measurements showed that the modified PbO2 anodes displayed a lower charge transfer resistance Rct. The influence of the introduction of a TiO2 intermediate layer and the boron doping of a PbO2 active surface layer on the electrochemical degradation of ampicillin (AMP) antibiotic have been investigated by chemical oxygen demand measurements and HPLC analysis. Although HPLC analysis showed that the degradation process of AMP with SS/PbO2 was slightly faster than the modified PbO2 anodes, the results revealed that SS/TiO2/PbO2-10%B was the most efficient and economical anode toward the pollutant degradation due to its physico-chemical properties. At the end of the electrolysis, the chemical oxygen demand (COD), the average current efficiency (ACE) and the energy consumption (EC) reached, respectively, 69.23%, 60.30% and 0.056 kWh (g COD)−1, making SS/TiO2/PbO2-10%B a promising anode for the degradation of ampicillin antibiotic in aqueous solutions.

Structural, Morphological, and Optical Analysis of La-Doped NiO Films Fabricated by the Sol-Gel Spin-Coating Technique for Solid-State Electronics

Structural, Morphological, and Optical Analysis of La-Doped NiO Films Fabricated by the Sol-Gel Spin-Coating Technique for Solid-State Electronics

Tuning room-temperature TCR of La0.7K0.3− xSrxMnO3 (0.00 ≤ x ≤ 0.3) films by K and Sr co-occupying A-site

A series of La0.7K0.3−xSrxMnO3 (0.00 ≤ x ≤ 0.3) films were fabricated on LaAlO3 substrates using a sol-gel spin-coating technique. The relationship between electrical transport properties and a microstructure was explained via the Jahn–Teller effect, a phenomenological percolation model, and a double-exchange mechanism. The results revealed the strong impact of K and Sr co-occupying A-sites on the formation of Mn3+/Mn4+ pairs, crystal structure, conductivity, surface morphology, and in-plane and out-of-plane strains. The as-fabricated La0.7K0.25Sr0.05MnO3 films showed a peak temperature coefficient of resistivity of 16.63% K−1 at 298.3 K.

Environmentally Benign Structural, Topographic, and Sensing Properties of Pure and Al-Doped ZnO Thin Films.

In the present research work, Zn1–xAlxO thin films with varying proportions of Al (x = 0.00, 0.01, 0.02, and 0.03) are prepared by a chemical sol–gel spin-coating technique. The crystal structural, morphological, and humidity-sensing properties of the synthesized Zn1–xAlxO thin films, with varying concentrations of Al (x = 0.00, 0.01, 0.02, and 0.03), were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM); a special humidity-controlled chamber was designed for the humidity-sensing studies. In structural and phase analyses, XRD patterns of Zn1–xAlxO thin films show a hexagonal wurtzite crystal structure. The average crystallite sizes of Zn1–xAlxO thin films were calculated and found to be ∼18.00, 22.50, 26.30, and 29.70 nm using the X-ray diffraction (XRD) pattern. The surface morphology of Zn1–xAlxO Al (x = 0.00, 0.01, 0.02, and 0.03) thin films obtained from AFM micrographs analysis indicates the modification of the spherical grains into nanorods, which were distributed throughout the surface of the films. The SEM image of 3 wt % Al-doped ZnO nanomaterials also shows that spherical nanoparticles changed to nanorod-like structures with a high packing density. Furthermore, increasing the Al-doping concentration from 0 to 3 wt % in ZnO NPs shows lower hysteresis loss, less aging effect, and good sensitivity in the range of 9.8–16.5 MΩ/%RH. The sensitivity of the sensing materials increased with increasing Al-doping concentration, which is very useful for humidity sensors.

Bi and Sn Doping Improved the Structural, Optical and Photovoltaic Properties of MAPbI3-Based Perovskite Solar Cells

One of the most amazing photovoltaic technologies for the future is the organic–inorganic lead halide perovskite solar cell, which exhibits excellent power conversion efficiency (PCE) and can be produced using a straightforward solution technique. Toxic lead in perovskite can be replaced by non-toxic alkaline earth metal cations because they keep the charge balance in the material and some of them match the Goldschmidt rule’s tolerance factor. Therefore, thin films of MAPbI3, 1% Bi and 0%, 0.5%, 1% and 1.5% Sn co-doped MAPbI3 were deposited on FTO-glass substrates by sol-gel spin-coating technique. XRD confirmed the co-doping of Bi–Sn in MAPbI3. The 1% Bi and 1% Sn co-doped film had a large grain size. The optical properties were calculated by UV-Vis spectroscopy. The 1% Bi and 1% Sn co-doped film had small Eg, which make it a good material for perovskite solar cells. These films were made into perovskite solar cells. The pure MAPbI3 film-based solar cell had a current density (Jsc) of 9.71 MA-cm−2, its open-circuit voltage (Voc) was 1.18 V, its fill factor (FF) was 0.609 and its efficiency (η) was 6.98%. All of these parameters were improved by the co-doping of Bi–Sn. The cell made from a co-doped MAPbI3 film with 1% Bi and 1% Sn had a high efficiency (10.03%).

Qualitative analysis of PZT (52/48) MPB using different synthesis methods

The current work reports a comparison between the structural and optical attributes of PZT (52/48) powder and thin film prepared via solid-state reaction and sol-gel spin-coating technique, respectively. The two obtained PZT samples, PZT-I corresponding to powder which was calcined at 875°C for 2 h, and PZT-II corresponding to a thin film which was annealed at 650°C for 2 h, were investigated via X-Ray Diffraction, Raman Spectroscopy, UV–Vis Spectroscopy, and SEM analysis. The diffraction spectra suggested the creation of a polycrystalline perovskite structure in both the samples. The optical band gap was evaluated using Tauc's relation. The bandgap values were found to be 3.2 eV for PZT-I and 3.87 eV for PZT-II. The bandgap values are significantly different for the PZT materials prepared by the two different methods.

Influence of boron addition on the phase transformation, microstructure, mechanical and in-vitro cellular properties of bredigite-type coatings deposited by a spin coating technique

Doped calcium silicates, e.g. bredigite (Ca7MgSi4O16) have recently become a growing interest in biomedicine thanks to outstanding biocompatibility, bioactivity, and improved mechanical properties when compared to calcium phosphate counterparts. Here, we have produced thin bredigite-type coatings on Ti6Al4V substrate by the polyvinyl alcohol (PVA) assisted sol-gel spin-coating technique and studied the influence of boron incorporation (0.5 and 1.0 mol) on the microstructural, phase, nanomechanical, and in-vitro cellular properties of deposited coatings. Chemical and structural analysis of the coatings was thoroughly performed by Focussed Ion Beam Scanning Electron Microscope (SEM/FIB), Atomic Force Microscopy (AFM), differential thermal analysis (DTA-TG), X-ray diffraction (XRD), and Fourier-Transform Infrared spectroscopy (FTIR), while the nanomechanical properties were evaluated by nanoindentation and nanoscratch tests. Overall, all deposited films were smooth and porous composed of ∼25–50 nm nanoparticles. The boron incorporation increased the coating thickness as a result of PVA interaction with borate ions. The nanomechanical properties (Young's modulus, nanohardness, critical load for cracking) decreased by the boron addition as a result of decreasing the strength of grain boundaries between the nanoparticles. The in-vitro contact cytotoxicity testing revealed high proliferation of the osteoblast cells in all coatings giving the potential of application in orthopedics.

Dependence of Structural and Optical Properties of ZnO Thin Films Grown by Sol–Gel Spin-Coating Technique on Solution Molarity

Dependence of Structural and Optical Properties of ZnO Thin Films Grown by Sol–Gel Spin-Coating Technique on Solution Molarity