Sol-gel Films Research Articles

Optimization and evaluation of ultra-trace amounts of lead in real samples using sol–gel based optical sensor coupled with colorimetry

The entrapment of the sensitive reagent 5-(2′-bromophenylazo)-6‑hydroxy-pyrimidine-2,4‑dione (BPAHPD) in a silica sol-gel thin film coated on a glass substrate has been investigated for the development of a highly sensitive and selective optode for the determination of lead ions. The fabrication of thin films requires tetraethoxysilane as a precursor, a sol-gel pH of 2.75, a water: alkoxide ratio of 5:1, and a BPAHPD concentration of 4.0 × 10–4 M. The effect of sol-gel parameters on the optode's sensing performance was investigated. The fabricated optode is utilized for lead ion detection over a dynamic range of 4.00–144 ng mL–1 with detection and quantification limits of 1.20 and 3.95 ng mL–1, respectively. It gave repeatable results with relative standard deviation (RSD) values of 1.90% and 1.15% for lead concentrations of 40.0 and 80.0 ng mL–1, respectively, and a response time of two minutes. Through capturing BPAHPD in a sol-gel matrix and appropriately modifying the structure of doped sol-gel, interference studies have determined that lead exhibits a high degree of selectivity. To ascertain total lead, Pb4+ was reduced to Pb2+ using a few drops of 6.00 M hydrochloric acid and a freshly prepared sodium azide solution of 2.50 % (w/v). The optode can be easily regenerated with 0.15 M of nitric acid solution. The optode has complete reversibility. Optode detection of lead in diverse vegetable, food, biological, water, and soil samples yielded favorable results when compared to other techniques.

Photoluminescence properties of Lu2Si2O7:Eu3+ sol-gel thin films obtained using GLYMO as a silicon source

Thin films of Lu2Si2O7:Eu3+ were prepared via sol-gel methods and dip coating using lutetium nitrate and (3-Glycidyloxypropyl)trimethoxysilane as precursors, and ethanol and ethylene glycol were used as solvents. Acetylacetone was used as a stabilizer, and the pH was adjusted using acetic acid. Lu2Si2O7:Eu3+ films were deposited on silica quartz substrates and exhibited a monoclinic structure with preferential orientation along the [012] direction after heat treatment at 1000 °C. The film’ morphology was characterized by scanning electron microscopy, and the photoluminescence spectrum revealed a strong emission at 612 nm (5D0→7F2), corresponding to the Eu3+ ions, under 254 nm excitation. Notably, both the optical yield and decay time increased with increasing SiO2 content.

Enhanced Acetone Gas Sensing Properties of Al-Doped ZnO Thin Films Developed by Sol-Gel Dip Coating Method

The acetone sensing capabilities of pure and Al-doped ZnO thin films developed by the sol-gel dip coating technique were examined inthis study. An investigation was conducted to examine the impact of Al doping concentration on the structural, morphological and sensing characteristics of the films. The results showed that acetone gas detection in ZnO thin films might be enhanced by doping with Al. In particular, when exposed to 10 ppm of acetone at room temperature, the response of 3 at% Al-doped ZnO thin film was the highest, achieving 53% and showed a fast response time of 6 s and a recovery time of 32 s. The researchers conducted additional investigations into the selectivity of acetone in the film when exposed to various interfering gases. The results revealed that acetone exhibited a favourable level of selectivity. The results presented herein demonstrate the effectiveness of sol-gel dip-coated thin films of Al-doped ZnO in the context of acetone gas sensing applications.

Characterization of an airborne organic contaminant sensor based on microfibers with sol–gel film

Introduction: Based on microfibers with sol–gel film, this study focuses on developing an organic contaminant sensing device to monitor airborne organic contamination in high-power laser facilities.Methods: The device heightened the sensitivity to the external environment with the nano-structure of sol–gel on the microfiber surface. The relationship between the additional laser transmission power loss caused by contaminants and the filling rate of the porosity of the film was discussed. In addition, we obtained the relationship between the additional loss and the refractive index of the microstructure.Results: The experimental results indicated that employing microfibers with microstructure coating could significantly improve sensing sensitivity to airborne organic contaminants. The precision of sensing surface contaminants can reach ng/cm2. When the concentration of organic contaminants is lower than 7.5%, the adsorption process of the microstructure coating is dominated by single-molecule adsorption, and the additional loss increases exponentially with increasing concentration, while the sensing limit is 70 ppm. When the concentration of organic contaminants exceeds 7.5%, the adsorption process of the surface microstructure coating is dominated by multimolecular adsorption. Therefore, the additional loss is exponentially related to the concentration of airborne organic contaminants, while the sensing limit is 10 ppm.Discussion: The study explored the adsorption mechanism of the sol–gel film to airborne organic contaminants at different concentrations. The Langmuir monolayer adsorption isotherm model and the Freundlich multi-molecular layer adsorption isotherm model was adopted to analyze and verify the experimental results, which suggested that the experimental results agree well with the simulation results. This work can be considered for in situ monitoring of airborne concentration contaminants and the transmittance of optics with the sol–gel film, and it also provides a new research method for in situ monitoring of airborne organic contaminants in the vacuum environment.

Sol-gel prepared amorphous Ta2O5 thin film for application in high LIDT antireflection coating and UV photodetection

In this report, a sol–gel method has been developed using tantalum ethoxide to produce homogenous thin films of amorphous Ta2O5 for application in optical coating for high power laser as well as photodetection in the UV range. Morphology, stoichiometry, optical properties, short range atomic structure and valence band have been investigated at various annealing temperature up to 500 °C. A large valence band onset of 3.5 ± 0.20 eV has been measured for the film annealed at 500 °C, ensuring hole blockage through the film and electron selective transport. Extended X-ray absorption fine structure (EXAFS) study has revealed the Ta–O bond distance to be 1.85 Å for as-deposited film, which increased with annealing and approached the crystallographic value. The sol-gel prepared Ta2O5 film has been used as antireflection (AR) coating on silicon and fused silica (FS) substrates. 99.4% transmission with a LIDT of 20 J/cm2 @6 ns at 1064 nm is obtained for Ta2O5/SiO2 AR coatings on FS. Using these sol-gel films, Ta2O5/Si vertical heterojunction photodetectors have been fabricated, which exhibited a responsivity of 560 mA/W, external quantum efficiency of 213%, and specific detectivity ∼1 × 1012 Jones at −1 V bias voltage and 325 nm illumination wavelength.

Influence of the Deposition Parameters on the Properties of TiO2 Thin Films on Spherical Substrates.

Wastewater treatment targeting reuse may limit water scarcity. Photocatalysis is an advanced oxidation process that may be employed in the removal of traces of organic pollutants, where the material choice is important. Titanium dioxide (TiO2) is a highly efficient photocatalyst with good aqueous stability. TiO2 powder has a high surface area, thus allowing good pollutant adsorption, but it is difficult to filter for reuse. Thin films have a significantly lower surface area but are easier to regenerate and reuse. In this paper, we report on obtaining sol-gel TiO2 thin films on spherical beads (2 mm diameter) with high surface area and easy recovery from wastewater. The complex influence of the substrate morphology (etched up to 48 h in concentrated H2SO4), of the sol dilution with ethanol (1:0 or 1:1), and the number of layers (1 or 2) on the structure, morphology, chemical composition, and photocatalytic performance of the TiO2 thin films is investigated. Etching the substrate for 2 h in H2SO4 leads to uniform, smooth surfaces on which crystalline, homogeneous TiO2 thin films are grown. Films deposited using an undiluted sol are stable in water, with some surface reorganization of the TiO2 aggregates occurring, while the films obtained using diluted sol are partially washed out. By increasing the film thickness through the deposition of a second layer, the roughness increases (from ~50 nm to ~100 nm), but this increase is not high enough to promote higher adsorption or overall photocatalytic efficiency in methylene blue photodegradation (both about 40% after 8 h of UV-Vis irradiation at 55 W/m2). The most promising thin film, deposited on spherical bead substrates (etched for 2 h in H2SO4) using the undiluted sol, with one layer, is highly crystalline, uniform, water-stable, and proves to have good photocatalytic activity.

Optical, luminescence, photocurrent and structural properties of sol-gel ZnO fibrous structure thin films for optoelectronic applications: A combined experimental and DFT study

Zinc oxide is an important oxide semiconductor, with excellent physical and chemical properties that are used in different applications fields. In this research paper, ZnO thin films were synthesized using different types of solvent by sol-gel spin coating technique. The effect of solvent on the structural, morphological, photocurrent and optical properties of the films has been studied. X-ray diffraction revealed the high crystallinity of films in the wurtzite structure with a c-axis preferred orientation. SEM micrographs revealed that all films exhibit a fibrous structure, where the more homogeneous and dense surfaces were observed for ZnO-2-PrOH and ZnO–EtOH films. The optical properties analysis shows that the films have high transparency. Different structural and optical parameters were influenced by the type of solvent, where ZnO-2-PrOH film displays an improvement in structural and optical properties. The photoluminescence PL spectrum revealed three emissions, two green emissions and a UV emission at 390 nm. ZnO-2-PrOH film exhibits a high intensity ratio of UV to visible (IUV/Ivis), a best UV response, and photocurrent properties. Finally, structural and optical parameters were also calculated by first-principles DFT calculations, discussed, and compared to those experimental.

Performance and mechanism of a novel biopolymer binder for clayey soil stabilization: Mechanical properties and microstructure characteristics

In this study, a novel stabilization approach using locust bean gum (LBG) was proposed to enhance the strength properties of natural soil. A series of laboratory tests were first performed on specimens using various biopolymer contents and curing durations. Subsequently, scanning electron microscopy and X-ray diffractometry were used to assess the intrinsic mechanism and microstructure. The LBG treatment considerably improved the mechanical strength of the natural soil, and the compressive, shear, and tensile strength increased with increasing biopolymer content. The increment in soil cohesion with increasing biopolymer content was more apparent than that in the internal friction angle. Sol–gel film sticking to soil particles significantly alters the macrofailure characteristic, which increases the failure path and ruptures plane unevenness, resulting in the failure of plane tortuosity. The increased curing duration prolonged interparticle interaction and strengthened biopolymer bonds, leading to improved mechanical properties. The enhanced effect of the LBG binder on soil can be explained by the formation of large stable aggregates with widely structured bonding groups. The entire biopolymer-soil matrix structures an integral matrix phase with a network system for strength enhancement.

A new chemosensor doped sol gel for Thorium(IV) determination

Abstract Herein, Diferuloylmethane (Curcumin) doped in a sol-gel thin film was introduced as a Thorium Th(IV) chemosensor. The suggested chemosensor exhibits a substantial decrease in fluorescence signal upon exposure to an aqueous solution containing Th(IV). To learn more about the coordination mode, sites, and quantum properties, computational work was done using the density functional theory (DFT). A lower predicted formation energy for the curcumin/Th(IV) complex (−9.57 × 104 eV) than for the free curcumin (−3.42 × 104 eV) has been found. While the dipole moment of the free Curcumin was 9.7955 debye, that of the Curcumin/Th(IV) complex was 40.6876 debye, which was greater. This implies that Curcumin and Th(IV) are well-coordinated. The suggested chemosensor can detect Th(IV) ion in aqueous solution throughout the range of 1.0 × 10−8 to 9.0 × 10−7 mol L−1, at pH 5, with a lower detection limit (LOD) of 2.50 × 10−8 mol L−1 and a lower quantification limit (LOQ) of 7.58 × 10−8 mol L−1. The effects of interference ions were investigated. Applications for determining Th(IV) directly in real samples produced findings that exhibited good agreement with results from inductively coupled plasma optical emission spectrometry (ICP-OES). The suggested chemosensor indicated outstanding performance features for Th(IV) including selectivity, long-term response stability, and high repeatability.

Low-cost piezo-MEMS speaker technology

In this paper, we are reporting low-cost piezo-MEMS speakers based on an SOI-free process. The speaker membrane is made of a 1.5 μm thick polyimide passive layer, obviating the need for SOI wafers. The custom-made PZT solution for depositing 1 μm sol-gel PZT thin films has further reduced fabrication costs. The membranes are realized by a backside Deep Reactive Ion etching (DRIE) on the silicon wafer. Laser doppler vibrometer (LDV) characterization has shown the resonance frequency of a single speaker element with a diameter of 2.5 mm to be 30 kHz with a sensitivity of 100 mm/s/V, whereas sensitivity at 4 kHz is around 1.2 mm/S/V. The speaker element can produce around 70–90 dB in-ear Sound Pressure Level (SPL) response in audible frequencies (100 Hz – 10 kHz) at 5 V excitation as shown by a simulation in an ear-coupler which is in line with the LDV measurements. Moreover, on average, the fabricated 4 × 4 arrays have shown a 10 dB higher SPL than a single-speaker element as measured by a microphone.

Rapid laser-induced low temperature crystallization of thermochromic VO2 sol-gel thin films

The thermochromic properties of vanadium dioxide (VO2) offer great advantages for energy-saving smart windows, memory devices, and transistors. However, the crystallization of solution-based thin films at temperatures lower than 400°C remains a challenge. Photonic annealing has recently been exploited to crystallize metal oxides, with minimal thermal damage to the substrate and reduced manufacturing time. Here, VO2 thin films, obtained via a green sol–gel process, were crystallized by pulsed excimer laser annealing. The influence of increasing laser fluence and pulse number on the film properties was systematically studied through optical, structural, morphological, and chemical characterizations. From temperature profile simulations, the temperature rise was confirmed to be confined within the film during the laser pulses, with negligible substrate heating. Threshold laser parameters to induce VO2 crystallization without surface melting were found. With respect to furnace annealing, both the crystallization temperature and the annealing time were substantially reduced, with VO2 crystallization being achieved within only 60 s of laser exposure. The laser processing was performed at room temperature in air, without the need of a controlled atmosphere. The thermochromic properties of the lasered thin films were comparable with the reference furnace-treated samples.

Sol-Gel Films Doped with Enzymes and Banana Crude Extract as Sensing Materials for Spectrophotometric Determination.

Chromogenic enzymatic reactions are very convenient for the determination of various biochemically active compounds. Sol-gel films are a promising platform for biosensor development. The creation of sol-gel films with immobilized enzymes deserves attention as an effective way to create optical biosensors. In the present work, the conditions are selected to obtain sol-gel films doped with horseradish peroxidase (HRP), mushroom tyrosinase (MT) and crude banana extract (BE), inside the polystyrene spectrophotometric cuvettes. Two procedures are proposed: the use of tetraethoxysilane-phenyltriethoxysilane (TEOS-PhTEOS) mixture as precursor, as well as the use of silicon polyethylene glycol (SPG).In both types of films, the enzymatic activity of HRP, MT, and BE is preserved. Based on the kinetics study of enzymatic reactions catalyzed by sol-gel films doped with HRP, MT, and BE, we found that encapsulation in the TEOS-PhTEOS films affects the enzymatic activity to a lesser extent compared to encapsulation in SPG films. Immobilization affects BE significantly less than MT and HRP. The Michaelis constant for BE encapsulated in TEOS-PhTEOS films almost does not differ from the Michaelis constant for a non-immobilized BE. The proposed sol-gel films allow determining hydrogen peroxide in the range of 0.2-3.5 mM (HRP containing film in the presence of TMB), and caffeic acid in the ranges of 0.5-10.0 mM and 2.0-10.0 mM (MT- and BE-containing films, respectively). BE-containing films have been used to determine the total polyphenol content of coffee in caffeic acid equivalents; the results of the analysis are in good agreement with the results obtained using an independent method of determination. These films are highly stable and can be stored without the loss of activity for 2 months at +4 °C and 2 weeks at +25 °C.

Effect of Laser Conditioning on Surface Modification and Laser Damage Resistance of SiO2 Antireflection Film

SiO2 sol-gel antireflection film coated on fused silica can reduce the reflection loss and improve the transmittance of the optical component, although it is still prone to laser induced damage. Laser conditioning is an effective way to improve the laser induced damage threshold (LIDT) of SiO2 sol-gel antireflection film. In this paper, single-layer SiO2 sol-gel antireflection films pretreated by triple-frequency laser with different parameters are characterized by the macroscopical parameters, such as transmittance, refractive index, and thickness. The law of surface modification and the defect removal mechanism of the SiO2 sol-gel antireflection film by laser conditioning are obtained. It is found that laser conditioning can reduce the thickness of the film and introduce densification. In addition, laser conditioning can eliminate micro-defects, such as vacancies and voids in the preparation of SiO2 sol-gel antireflection films, which is the main reason to improve the laser damage resistance of films. Finally, the laser conditioning process with three step laser energy combinations of (0.2–0.6–1.0) Fth0 (zero damage threshold) is the best one to obtain high transmittance, and excellent effects on structure modification and defect removal of films. The research in this paper provides data support for the engineering application and mechanism research of laser conditioning.

Optical and mechanical characterization of sol-gel thin films of ZrO2 stabilized with different Y2O3-doping mol%

The influence of the molar proportion of Y2O3 dopant (3, 9, and 12 mol%) on the optical and mechanical properties of ZrO2 thin films was studied. For this purpose, the three types of deposited thin films were first characterized microstructurally by spectrophotometry, optical microscopy, scanning electron microscopy, and X-ray diffractometry, and then their optical properties were measured by spectrophotometry and their mechanical properties by nanoindentation. It was found that they all crystallize in the cubic phase, even for dopant contents that would not do so in bulk materials. It was also found that, with increasing Y2O3 dopant, the refractive index increases while the optical absorption and extinction coefficients, the hardness, and the elastic modulus decrease. These trends are due to the poorer crystallinity and greater distortion of the crystal lattice of YSZ thin films with increasing Y2O3 dopant. The results are especially relevant for applications which require certain conditions of reflection and absorption of light energy, while maintaining optimal mechanical properties.

Investigation of electrophysical, photo- and gas-sensitive properties of ZnO–SnO2 sol–gel films

Thin nanocomposite films based on tin dioxide with a low content of zinc oxide (0.5–5[Formula: see text]mol.%) were obtained by the sol–gel method. The synthesized films are 300–600[Formula: see text]nm thick and contains pore sizes of 19–29[Formula: see text]nm. The resulting ZnO–SnO2 films were comprehensively studied by atomic force and Kelvin probe force microscopy, X-ray diffraction, scanning electron microscopy, and high-resolution X-ray photoelectron spectroscopy spectra. The photoconductivity parameters on exposure to light with a wavelength of 470[Formula: see text]nm were also studied. The study of the photosensitivity kinetics of ZnO–SnO2 films showed that the film with the Zn:Sn ratio equal to 0.5:99.5 has the minimum value of the charge carrier generation time constant. Measurements of the activation energy of the conductivity, potential barrier, and surface potential of ZnO–SnO2 films showed that these parameters have maxima at ZnO concentrations of 0.5[Formula: see text]mol.% and 1[Formula: see text]mol.%. Films with 1[Formula: see text]mol.% ZnO exhibit high response values when exposed to 5–50[Formula: see text]ppm of nitrogen dioxide at operating temperatures of [Formula: see text]C and [Formula: see text]C.

The Antimicrobial Activity of Micron-Thin Sol-Gel Films Loaded with Linezolid and Cefoxitin for Local Prevention of Orthopedic Prosthesis-Related Infections.

Orthopedic prosthesis-related infections (OPRI) are an essential health concern. OPRI prevention is a priority and a preferred option over dealing with poor prognosis and high-cost treatments. Micron-thin sol-gel films have been noted for a continuous and effective local delivery system. This study aimed to perform a comprehensive in vitro evaluation of a novel hybrid organic-inorganic sol-gel coating developed from a mixture of organopolysiloxanes and organophosphite and loaded with different concentrations of linezolid and/or cefoxitin. The kinetics of degradation and antibiotics release from the coatings were measured. The inhibition of biofilm formation of the coatings against Staphylococcus aureus, S. epidermidis, and Escherichia coli strains was studied, as well as the cell viability and proliferation of MC3T3-E1 osteoblasts. The microbiological assays demonstrated that sol-gel coatings inhibited the biofilm formation of the evaluated Staphylococcus species; however, no inhibition of the E. coli strain was achieved. A synergistic effect of the coating loaded with both antibiotics was observed against S. aureus. The cell studies showed that the sol-gels did not compromise cell viability and proliferation. In conclusion, these coatings represent an innovative therapeutic strategy with potential clinical use to prevent staphylococcal OPRI.

Exploring ferroelectric properties of sol-gel lead zirconate titanate nano-crystalline thin films and ceramics by doping ytterbium for energy-storage application

This work concerns how ytterbium affects the ferroelectric characteristics of sol-gel Yb doped lead zirconate (PYZ) and lead zirconate titanate (PYZT) thin films and ceramics. Lead zirconate Pb(0.9) )-Yb0.01 Zr (0.09 (PYZ) and lead zirconate titanate Pb0.9-Yb0.01-Zr0.045-Ti0.045 (PYZT) doping with ytterbium thin films were prepared on a glass substrate using a sol-gel doctor blade coating technique at low temperature. The structure of the synthesized thin films and ceramic nanocrystals was examined using X-ray diffraction (XRD), transmission electron microscopy (TEM), and electron diffraction (ED). PYZ and PYZT ceramics had 11.8 nm and 30.65 nm respectively, whereas PYZ and PYZT thin films featured nanocrystals that were, respectively, 17.5 nm and 13.87 nm in size. Particle size was determined to be entirely consistent across the TEM and XRD data. Dielectric investigations showed that the dielectric constant was dropping for ceramic samples as compared to thin film samples. According to hysteresis loop estimates, the energy-storage density and efficiency for thin films and ceramics were average approximately 39.35 J cm−3 and 66.02 percent for (PYZ) and 71.33 J cm−3 and 70.91 percent for (PYZT), respectively. The results showed that the ferroelectric, dielectric, and structural properties of materials affected the ytterbium content. (PYZ) and (PYZT) thin films and ceramics may have a prospective use in energy storage devices.

Preparation and evaluation of high-transparent scratch-resistant thin films on plasma treated polycarbonate substrate

New simple aqueous sol–gel procedure has been used for producing hard transparent organic–inorganic coatings on polycarbonate (PC). Sol-gel thins films were prepared by mixing Si and Al aqueous alkoxides and applied on the plasma treated PC. Tetraethyl orthosilicate (TEOS), 3-glycidoxypropyltrimethoxysilane (GPTMS) and aluminum tri sec-butoxide were used as main precursors. Before applying coatings PC were treated by Dielectric Barrier Discharge (DBD) system being conducted at atmosphere pressure. The effects of temperature, sols volume ratios and aging time on the coatings properties were scrutinized. Chemical, structural, morphological, optical and mechanical analyses of the samples were done by ATR-FTIR, EDS, XRD, FE-SEM, TEM, UV/vis spectroscopy, ellipsometry, pencil hardness and eraser scratch methods. TEM results showed well-dispersed nano-particles in the liquid sol. All of the films showed higher average transmittance (89 %) than the raw PC (86 %) that was stemmed from the lower refractive index (1.481) than raw PC (1.58). Films indicated good adhesion onto the plasma treated substrates (5B). The pencil hardness of the PC substrate (4B) improved to 3H (8 pencil grade increment) with just a single layer coating (775 nm thickness) due to the preparation of new hard structures of interlocked Si and Al atoms.

Pulsed electrophoretic deposition of hybrid coatings from aqueous suspensions as surface functionalization and sealing technique of anodized AA2024. Part I: Morphological characterization, analysis of the interfacial interactions, and evaluation of pore impregnation of the anodic layer

In this two-part series, pulsed direct current for cathodic electrophoretic deposition (pulsed-CEPD) was studied as sealing technique of anodized AA2024 by depositing hybrid sol-gel films from aqueous suspensions. The coating was obtained using tetraethyl orthosilicate and hexadecyltrimethoxysilane as precursors and two pulse widths were used: 10 microseconds and 100 milliseconds. For comparison, continuous direct current for cathodic electrophoretic deposition was also performed. In this first article, it was developed a low-cost automated apparatus capable of creating pulsed fields using a commercial power supply. This was necessary since the automation system provided by the power supply manufacturer did not have a short enough response time able to create pulse widths in the order of microseconds. Field emission scanning electron microscopy (FESEM) and focused ion beam milling techniques were utilized to evaluate the surface morphology and interaction mechanisms in the interface anodic layer/film. Low voltage scanning transmission electron microscopy (STEM)-in-FESEM, and transmission electron microscopy (TEM) were used to evaluate the pore impregnation provided by pulsed-CEPD. Results demonstrated that the developed apparatus successfully created pulsed fields. FESEM micrographs of the anodic layer sealed by pulsed-CEPD showed that the shortest pulse provided the best films, likely due to the greater control of hydrogen bubbles generation and the promotion of a more regular deposition. Also, they revealed two interfacial interactions between the anodic layer and the film. STEM-in-FESEM images showed that the shortest pulse width provided greater pore impregnation by particles. This observation was confirmed by TEM, which demonstrated an incomplete pore impregnation for the longest pulse. Discussion regarding result interpretations is presented based on the generation and dissipation of H2(g) (considering the current interruption); on an alternative to the colloidal stability theory due to the presence of a pulsed field; and on the electrokinetic effects at the electrodes during pulsed-CEPD, that discusses how electroosmotic flow influences the deposition.

Electrical characterization of sol-gel La2Ti2O7 films for resistive random access memory applications

The bipolar resistive switching (BRS) devices were investigated for RRAM applications in a MIM structure based on sol-gel derived amorphous La2Ti2O7 (LTO) thin films. The influences on the resistive switching (RS) properties according to the film thickness, electrode, annealing temperature and post metal annealing (PMA) treatment were also discussed. Moreover, RS performance of the RRAMs is affected by the work functions of electrodes. The RS characteristics of the devices are controlled by oxygen vacancies and the content of oxygen vacancies was seriously reduced after annealing, which led to a significant decrease of the endurance. In addition, PMA treatment increased the content of oxygen vacancies attributed to the forming of AlOx interface layer and made Al ions diffuse into the films to form bridges, which improved the RS performance of the devices. Consequently, the sample with 300 °C PMA exhibits the optimized RS properties with maximum switching cycles of 2674, a Ron/Roff ratio of 102, low operating voltages (VSet/VReset = 1.32 V/−1.21 V), and a retention time of over 104 s at room temperature and 85 °C, indicating the promising potential for practical RRAM applications. Conduction mechanism of all devices with Al top electrode were described by trap-controlled space-charge limited current (SCLC) and ohmic conduction.