Sol-gel Deposition Technique Research Articles

Exploring resistive switching properties and mechanisms in sol-gel derived Gd2Ti2O7 thin films for RRAM applications

This study focused on investigating the effects of film thicknesses and thermal treatments on the resistance-switching characteristics of Gd2Ti2O7-based RRAM devices for the first time. Gd2Ti2O7 thin films were successfully synthesized using a sol-gel deposition technique on ITO/glass substrates as the foundation for this research. The conduction mechanism of the filament was found to be primarily influenced by oxygen vacancies. The study found that annealing at 300 °C resulted in a slight increase in oxygen vacancies and switching cycles. However, annealing at 200 °C and 400 °C led to a significant decrease in oxygen vacancies, resulting in reduced switching cycles. To further enhance the device performance, a post-metal annealing process was applied at 300 °C to form an extra AlOx layer. This additional layer facilitated the coexistence of oxygen vacancies and aluminum ions, promoting the formation of conductive filaments and enhancing the resistive switching performance of the devices. As a result, the device subjected to 300 °C post-metal annealing demonstrated optimized resistive switching properties, including a maximum of 1248 switching cycles, a Ron/Roff ratio of 102, and VSet/VReset = −5.38 V/2.08 V. These findings highlight the promising potential of Gd2Ti2O7-based RRAM devices for practical applications in Resistive Random Access Memory (RRAM).

Study of the effects of heating on the physical, optical, and electrical properties of NiO thin films synthesized using a low-cost sol-gel method

Developments in low-cost techniques for growing high-quality nickel oxide thin films (NiOTFs) are critical enablers for the fabrication of NiO-based devices, particularly solar cells, light-emitting diodes, lasers, and many other applications. In this study, it has been demonstrated that the optical, electrical, and structural characteristics of NiOTFs coated on glass substrate employing a low-cost solution method are strongly influenced by post-thermal annealing treatments in ambient air. A comprehensive study was carried out on the characteristics of the deposited NiOTFs. X-ray diffraction (XRD) measurements indicate the enhancement of the crystal quality of films after annealing. There is a noticeable change and improvement in coated NiOTFs with heat treatment at 300 and 600 ℃ due to clear shifts in density. During the heating temperature increment, the energy of the band gap was shifted from 3.63 to 3.44 eV, and the electrical resistance of the NiOTFs varied from 1020 to 700 Ω-cm. Furthermore, the results indicate that the low-cost sol-gel (SG) deposition technique has a greater potential for producing high-quality p-type NiOTFs with minimal defects for electronic device applications.

Tailoring of the Structural, Optical, and Electrical Characteristics of Sol-Gel-Derived Magnesium-Zinc-Oxide Wide-Bandgap Semiconductor Thin Films via Gallium Doping.

The Ga-doped Mg0.2Zn0.8O (GMZO) transparent semiconductor thin films were prepared using the sol-gel and spin-coating deposition technique. Changes in the microstructural features, optical parameters, and electrical characteristics of sol-gel-synthesized Mg0.2Zn0.8O (MZO) thin films affected by the amount of Ga dopants (0-5 at%) were studied. The results of grazing incidence X-ray diffraction (GIXRD) examination showed that all as-prepared MZO-based thin films had a wurtzite-type structure and hexagonal phase, and the incorporation of Ga ions into the MZO nanocrystals refined the microstructure and reduced the average crystallite size and flatness of surface roughness. Each glass/oxide thin film sample exhibited a higher average transmittance than 91.5% and a lower average reflectance than 9.1% in the visible range spectrum. Experimental results revealed that the optical bandgap energy of the GMZO thin films was slightly higher than that of the MZO thin film; the Urbach energy became wider with increasing Ga doping level. It was found that the 2 at% and 3 at% Ga-doped MZO thin films had better electrical properties than the undoped and 5 at% Ga-doped MZO thin films.

Processing and Weathering of Sol-Gel Clearcoats for Coil-Coated Steel

Clearcoats provide long-term aesthetics and protection for underlying coating systems, increasing product lifetimes. However, organic clearcoats are predominantly produced using fossil-fuel feedstocks. In search of a sustainable alternative, an experimental investigation was conducted on the development of glass-like clearcoats produced using the sol-gel process. The processing of sol-gel clearcoats over a pigmented polyurethane coating was studied by modifying the sol-gel solution pH, ageing, curing, precursor chemistry and deposition techniques. Under optimal formulation and processing conditions, defect-free sol-gel clearcoats were produced that have the potential to be scaled up to a coil-coating line using existing technologies. Mechanical testing demonstrated the coatings had excellent adhesion, hardness, and flexibility. Furthermore, accelerated laboratory weathering tests revealed the sol-gel coatings had superior degradation resistance compared to the organic coatings tested, resulting in negligible colour changes and higher gloss retention after 4000 h of exposure. The durability and environmental benefits of sol-gel clearcoats highlight their potential as a replacement for traditional organic clearcoats in a variety of applications.

Polymeric solar cell with 18.06% efficiency based on poly(para-nitroaniline)/TiO2 composites

In this paper, the poly para-nitro aniline [PPNN]/titanium (IV) oxide [TiO2]NPs composite was synthesized and investigated followed by the fabrication of thin film. The sol gel and physical vapor deposition (PVD) techniques have been successfully used to deposit [PPNN/TiO2]MNC thin film with good adhesion and film thickness ≅ 100 ± 3 nm. The structural and morphological properties of [PPNN/TiO2]MNC thin films were studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The measured optical properties of [PPNN/TiO2]MNC thin films as Reflectance (R) in the UV–vis–NIR spectrum, Absorbance (Abs), and Transmittance (T) have been employed to probe the optical characteristics at room temperatures. As well as the calculations of TD-DFT (time-dependent density functional theory) and the optimization through TD-DFT/Mol3 and Cambridge Serial Total Energy Bundle (TD-FDT/CASTEP) were employed to study the geometrical characteristics. The rectifier ration (RR), indeality factor (n) and barrier potential ΦB (eV) values are 0.74 × 105, 2.98 and 1.05 at 375 K, respectively. The Au/[PPNN/TiO2]MNC/p-Si/Al heterojunction device's power conversion efficiency are 18.06 at 200 W. cm−2. The obtained results candidates [PPNN/TiO2]MNC thin film as a good material for solar cells and optoelectronic devices.

Polyamide aerogel-derived n-doped carbon aerogel decorated with platinum nanoparticles as highly active and stable electrocatalysts for oxygen reduction reaction

We prepared polyamide aerogel (PA)-derived carbon aerogel (CA) supported Pt nanoparticles with the supercritical CO2 deposition (SCD) technique as electrocatalysts for the oxygen reduction reaction (ORR). PAs were pyrolyzed at 800 °C to yield CPA and some CPA monoliths were subsequently etched with CO2 at 1000 °C to yield etched CPA (ECPA) to increase micro-mesoporosity and surface area in order to investigate their effect on the Pt nanoparticle dispersion and electrocatalytic performance towards ORR. The N-rich backbone of PAs yielded homogenously distributed N atoms in the CA structure enabling homogenous distribution of Pt nanoparticles, efficient dispersion of the Nafion ionomer and possible creation of ORR-active sites. Highly dispersed Pt nanoparticles with average size of 1.5 and 3.0 nm were obtained on CPA and ECPA, respectively. Pt-ECPA electrocatalysts showed enhanced electrochemically active surface area (ESA) and ORR mass activity when compared with commercial Pt-C. Pt-CPA showed similar ESA, mass and specific activity to that of commercial Pt-C due to lower mesopore volume and higher average Pt nanoparticle size. Accelerated stability tests (AST) revealed superior stability of Pt-CPA electrocatalyst due to favorable initial Pt nanoparticle size enabling successful immobilization Pt nanoparticles on CPA through the N-functionalities. Two important parameters, pore structure of carbon aerogel and initial Pt nanoparticle size, can be controlled through the powerful combination of sol-gel and supercritical deposition techniques to achieve both highly active and stable electerocatalysts.

Enhanced Optical and Ragged Metamaterials Properties of Silver Silica Nanocomposite Thin Film via Sol-Gel and Electrophoresis Deposition Technique

Various filling fractions of silver silica nanocomposites (Ag-SiO2 NC) were successfully synthesized via sol-gel technique and deposited onto indium tin oxide via electrophoretic deposition (EPD). Ag-SiO2 NC was investigated using X-ray diffraction, FTIR spectroscopy, Uv-vis and transmission electron microscopy. The XRD and Uv-vis results revealed that Ag-SiO2 NC is stable with a filling fraction of 0.6 in the dielectric medium with excellent absorption peak. Spectroscopy Ellipsometry shows that the effective permittivity and refractive index obtained from this filling fraction are -0.88 and 0.90, respectively. We discovered a ragged of metamaterial properties at negative permittivity.

Development of pseudocapacitive materials based on cobalt and iron oxide compounds for an asymmetric energy storage device

Composite electrodes based on cobalt hydroxide and iron oxide, respectively, with silica as an under-layer were developed with the use of sol-gel and electrochemical deposition techniques. The electrodes demonstrate similar surface morphologies of the upper pseudocapacitive layer formed by lamellas. The composite Co-based electrodes as well as Fe-based electrodes with silica reveal higher values of capacitance retention after multiple charge-discharge process than the ones without it. The influence of OH−concentration upon pseudocapacitive behavior was estimated for Co–based electrodes. The mixed electrolyte with an extremely low alkali concentration proved to increase capacitance retention of the electrodes. A model of an asymmetric pseudocapacitor was fabricated with the use of the Co and Fe–based electrodes, pre-coated with silica. The use of differential capacitance technique in a full electrochemical cell allowed balancing charges of positive and negative electrodes within their potential windows. The maximum voltage range of 1.4 V was achieved for the cell which exceeds the window of electrochemical stability of water.

Influence of sintering temperature on structural, morphological and optical properties of nanocrystalline bismuth ferrite thin films via sol-gel processing

Nanocrystalline thin films of pure bismuth ferrite were synthesized by sol-gel deposition technique on the corning glass substrate. The influence of sintering temperature on microstructure, morphology, and optical parameters has been systematicallystudied. Optimization of sintering temperature for single-phase nanocrystalline bismuth ferrite fabrication was carried out and found to be at 550 °C. X-ray diffraction confirms the presenceof distortedrhombohedral perovskite structure of bismuth ferrite oriented along (hkl) plane of (101).Surface morphology and Root mean square (RMS) surface roughness of the thin films prepared were determined from the micrographs of atomic force microscopy (AFM).Several optical constants viz. bandgap energy, extinction coefficient,Urbach energy, has been determined using Ultraviolet-Visible spectroscopy of the thin films within the range 200 -800 nm. With the increase in sintering temperature, there is a decrease in the optical bandgap of the material which would be essential for the wide range of applications in thin-film solar cells along with optoelectronic devices.

Synthesis, Microstructure and Properties of Magnetron Sputtered Lead Zirconate Titanate (PZT) Thin Film Coatings

Compared to aluminum nitride (AlN) with simple stoichiometry, lead zirconate titanate thin films (PZT) are the other promising candidate in advanced micro-electro-mechanical system (MEMS) devices due to their excellent piezoelectric and dielectric properties. The fabrication of PZT thin films with a large area is challenging but in urgent demand. Therefore, it is necessary to establish the relationships between synthesis parameters and specific properties. Compared to sol-gel and pulsed laser deposition techniques, this review highlights a magnetron sputtering technique owing to its high feasibility and controllability. In this review, we survey the microstructural characteristics of PZT thin films, as well as synthesis parameters (such as substrate, deposition temperature, gas atmosphere, and annealing temperature, etc.) and functional proper-ties (such as dielectric, piezoelectric, and ferroelectric, etc). The dependence of these influential factors is particularly emphasized in this review, which could provide experimental guidance for researchers to acquire PZT thin films with expected properties by a magnetron sputtering technique.

Effect of lithium salt precursors on the physical properties of ZnO-Li thin films

Zinc oxide (ZnO) thin films were prepared on glass substrates with three different lithium salt precursors (acetate, chloride and nitrates) with Li/Zn atomic ratio varying between 0% and 20% using sol-gel deposition and spin-coating technique. The aim of the work was to compare the physical properties of lithium containing ZnO thin layers obtained using different Li salt precursors; in order to identify the most suitable one. The X-ray diffraction measurements showed that all 500°C annealed films were polycrystalline. The samples prepared from lithium nitrates solutions showed a preferred orientation along c-axis (002) and their crystallites sizes are much larger compared to other Li source. The ultraviolet-visible transmission spectra confirmed the good transparency of all ZnO films with an average transmission around 85 % in the visible range. The optical band gap values varied between 3.19 eV and 3.28 eV. All the results revealed that the ZnO-Li films prepared with LiNO3 exhibit the highest crystallographic quality and the best optical and electrical properties compared to C2H3LiO2 and LiCl containing precursors.

Sugarcane juice clarification by lanthanum phosphate nanofibril coated ceramic ultrafiltration membrane: PPO removal in absence of lime pre-treatment, fouling and cleaning studies

The present work explores the possibility of employing rare earth phosphates deposited alumina substrates for ceramic membrane applications. Multichannel porous alumina supports are coated with Lanthanum phosphate nanofibrils of thickness 6 µm by sol-gel deposition technique. The performance of lanthanum phosphate coated ultrafiltration (UF) membrane for sugarcane juice clarification was studied by measuring polyphenol oxidase (PPO) enzyme, bacteria removal efficiency and permeate flux decline profile. The PPO enzyme activity was observed to be lower by 70% in permeate along with a less bacterial presence. The analysis of sucrose loss with time is also studied for raw sugarcane juice, clarified and limed sugarcane juice. A hybrid cleaning strategy involving an innovative brushing action on the membrane surface for physical cleaning combined with chemical cleaning was implemented in this study. The fouled membrane was analyzed by FESEM, EDX, and FTIR. Shelf-life study of feed and permeate confirmed that permeate was more stable than the feed. The experimental results conclude that raw sugarcane juice clarification using lanthanum phosphate coated UF membrane was viable with the use of innovative physical cleaning method as proposed in this study.

Electrochemically assisted deposition of sol–gel films on graphene nanosheets

Due to physical collisions and electron transfer between the working electrode and conductive nano-materials, electrochemical reactions can occur on the surface of both. Here, we explore the use of an electrochemically assisted sol–gel deposition technique (EAT) to modify the surface of nanomaterials. Taking graphene as an example, the fabricated free-standing graphene–silica nanosheet composite exhibits a sandwich structure, with mesoporous silica films covering both sides of the graphene. The thickness of the nanocomposites can be tuned (up to ∼50 nm) by controlling the potential and duration of the deposition, and the concentration of the sol–gel precursor. The approach ensures, uniquely, that the silica films are securely attached to the graphene substrate. This indirect deposition technique could also be used for the surface modification of other nanomaterials.

Corrosion and Wear Behavior of Nano-Zirconium (Zr) Coated Commercial Grade Cast Iron by Sol-Gel and Plasma Spray Process

Hard facing with Nickel/cobalt based alloys for steel substrates are widely used for high temperature and pressure applications in chemically reactive environments due to their good corrosion and wear resistance properties. In the present research, the ceramic material, i.e., zirconium, is coated on a hypoeutectic cast iron substrate to improve its corrosion and wear resistance. The substrate was coated with zirconium by sol-gel process as well as by the plasma spray process for comparison purpose. Results of the research indicated that the successful deposition of zirconium on the cast iron substrate by sol-gel deposition technique had improved both corrosion and wear resistance of cast iron. SEM analysis revealed that the coating was denser without any internal cracks indicating the soundness of deposition. Also, sol-gel process of coating indicated better wear resistance as compared with plasma spray coated cast iron. Thus, zirconium coating on the substrate has made cast iron sound (without any surface defects) along with excellent corrosion and wear resistance properties. This has made cast iron suitable for structural and automotive applications.

TiO2 modifikovana karbonizovanim materijalima - fotokataliza/adsorpcija organskih polutanata u vodi - kratak pregledni rad

The TiO2 /carbonized materials in composites provide a synergistic effect of adsorption and photocatalysis. The activated carbon or carbonized material can be prepared using various raw materials that present agricultural waste. The most commonly used process for the preparation of the activated carbon (AC)/carbonized material is chemical activation. Chemical activation produces the activated carbon with a good surface area and pore system, which contributes to better adsorption of organic pollutants. The TiO2 /AC composite materials can be prepared by sol-gel, hydrothermal and metal organic chemical vapor deposition (MOCVD) techniques. The most commonly used techniques for characterization of the TiO2 /AC materials are XRD, BET, TG Analysis and UV-Vis DRS, and will therefore be discussed in this paper. The TiO2 /AC composite materials have shown significant efficiency in removal of organic pollutants from aqueous solutions. The adsorption process of organic pollutants can be affected by various process parameters that will be observed in this paper.

Ultra-low resistivity aluminum doped ZnO thin films on flexible substrates using sol-gel solution deposition

The effect of a combination of low temperature heat treatments, microwave annealing, and low temperature vacuum annealing on the resistivity of 1% Al-doped ZnO thin films (AZO) deposited on both flexible polyimide films and rigid silicon substrates was investigated. The sol-gel deposition technique was used to deposit successive layers with a 0.5-hour heat treatment application prior to the deposition of additional layers. Following the final layer deposition and 0.5-hour treatment, the samples either underwent a final thermal annealing or microwave plus thermal annealing. Finally, a post-treatment annealing in a high vacuum chamber at 300 °C was administered. The films exhibited ultra-low resistivity of 14 Ω-cm on the polyimide with good adhesion qualities and a 0.08 Ω-cm resistivity on silicon wafers. A hexagonal wurtzite structure with the (002) c-axis orientation in the film growth direction was evident along with a dense microstructure of homogeneously distributed grains.

New sol-gel deposition technique in the Smart-Windows – Computation of possible applications of Smart-Windows in buildings

The integration of a new architectural component into the building envelope can contribute to improving its energy performance, and the comfort conditions visual and thermo-hygrometric. Two deposition methods are used: dip-coating and spin-coating, optically characterized by spectro-photometric techniques. Measurements of a dynamic type have enabled the determination of parameters such as switching times (relative to the coloring and inverse process) and optical memory (important in smart-window applications to reduce the consumption of operating energy). The experimental results of the deposition technique on two electro-chromic devices measuring made at the Department of Engineering of the University of Messina, are shown below. In this study, through a computational investigation, the possibilities of environmental control of "Smart-Windows" with electro-chromic technology are investigated. To characterize these aspects, the thermal behavior of a building-model equipped with electro-chromic Smart-Windows was analyzed using the MC4 Software simulation program. Through the separate applications of the Smart Windows, connected with different types of shading, we have proceeded to simulate the calculation of the energy requirement of a block of the Engineering Faculty of the University of Messina, which has a building typology favorable to the study, being characterized by extensive glass walls facing south. Annual cooling thermal loads calculated for the building under examination. for different control strategies of the Smart Windows, they were then compared with the thermal loads obtained with traditional glass systems (actually installed) for different types of shielding in order to estimate any energy savings

Novel sol-gel deposited p-type SnO:Mn:K for solar cell applications

Novel p-type SnO:Mn:K thin films were synthesized by a sol-gel deposition technique on soda-lime glass substrates. The structure of the SnO:Mn:K thin films were investigated by scanning electron microscopy and X-ray diffraction pattern measurements and were found to be strongly influenced by the dopant concentration, with a significant changes in film morphology as the KMn dopant increases. Hall effect measurement revealed that p-type SnO:Mn:K thin films can be obtained within the optimized doping concentration. The p-type doping was also confirmed by integrating the SnO:Mn:K thin film onto n-type crystalline silicon to form a heterojunction device.

Transition from mobility-activated small polaron to carrier density-activated conduction of sol-gel-derived highly-oriented CuAlO2 thin film and enhanced thermoelectric properties

CuAlO2 is a technologically important material having diverse applications, including superior thermoelectric properties. Its unique crystallographic structure manifests an anisotropic environment for the charge carriers and phonons, which is considered to be the reason for the enhancement of the thermopower. To exploit this novel property, a controlled sol-gel deposition technique is adopted to realize highly c-axis-oriented growth of CuAlO2 thin film on Si and glass substrates. Thermoelectric measurements are performed in such a way that the carriers are confined along the a-b plane of the nanocrystal, which is parallel to the substrate. This allows a two-dimensional confinement of the charge carriers, leading to enhanced thermoelectric properties. Additionally, the temperature-dependent electrical characterizations depict two different charge-transport regimes with a cross-over at 360K. The low-temperature region corresponds to the mobility-activated small-polaron conduction and the high-temperature region belongs to the semiconductor-type carrier-density-activated conduction. Calculation of polaron activation energy from low-temperature regime indicates considerable influence of band carriers (hole) on the polaronic levels, due to which the above-mentioned transition is manifested. Calculations of activation and Fermi energy from high-temperature regime reveal a deep acceptor level and shallow Fermi level, which is typical of a non-degenerate semiconductor with acceptors not fully ionized at room temperature.

Nano-structured WO3 layers sensitized with ALD Pt for quick detection of H2S

WO3 nano-structured layers on top of micro-hotplates were formed by sol–gel deposition technique and electrochemical anodic etching of thin tungsten layers. Both types of gas sensing layers were activated by drop coated Pt nano-particles and alternatively, by atomic layer deposited (ALD) Pt. Due to the limited number of ALD cycles the Pt layer is not a contiguous but composed of uniformly distributed nano-particles of 2–3 nm size. Devices were characterized by their responses for exposure of H2S and NH3. Investigation of sensitivity, selectivity and device dynamics revealed that the ALD sensitized, electrochemically formed porous WO3 layer is suitable for quick detection of H2S.