Performance Of TiO2 Thin Films Research Articles

Atomic Layer Deposition of Defective Amorphous TiOx Thin Films with Improved Photoelectrochemical Performance.

A proper control of defects in TiO2 thin films is challenging work for enhancing the photoelectrochemical (PEC) efficiency in water splitting processes. Additionally, a deep understanding of how defects affect the PEC performance of TiO2 thin films is of great interest for achieving better performance. With these aims, we prepared defective amorphous TiOx thin films at various growth temperatures by atomic layer deposition using tetrakis(dimethylamido)titanium as the Ti precursor. Careful X-ray photoelectron spectroscopy and electron spin resonance spectroscopy analyses revealed that the defect concentration in the TiOx thin films can be controlled by adjusting the growth temperature during the ALD process. We also evaluated the light absorption properties of the deposited TiOx thin films using ultraviolet-visible absorption spectroscopy. And it was found that the TiOx thin film deposited at a growth temperature of 200 °C exhibited the highest defect concentration and the highest photocurrent density of 0.051 mA/cm2 at 1.23 V vs reversible hydrogen electrode (RHE) compared to those of the other films. The light absorption efficiency, photogenerated charge separation efficiency, and charge transfer efficiency of defective amorphous TiOx thin films were carefully studied to understand the correlation between the defect concentration in the prepared TiOx thin film and its PEC activity. This study provides insight into the PEC properties of defective amorphous ALD-TiOx thin films.

Achievement of high electrochromic performance of TiO2 thin films prepared via spray pyrolysis method, influence of annealing process

In this study, an optimised TiO2 thin film was first prepared by the traditional spray pyrolysis method on SnO2:F (FTO) coated glass substrates, and then it was annealed at 450 °C in an ambient air atmosphere for different time durations of 1, 2, and 3 h. The FESEM images, XRD diffractograms, Raman and PL spectra indicate that compared to the pristine state, the annealing process has considerably affected the morphology and improved the crystallinity and stoichiometry of the layer. The electrochromic (EC) measurements revealed that the 3h annealed sample has the highest ever reported colouration efficiency of 91.54 cm2.C−1 (approximately 30 times bigger than the related reports) and low colouration and bleaching times of 0.2 and 1.1 s, respectively.

Evaluation of the performance of TiO2 thin films doped with silver nanoparticles as a protective coating for metal prostheses

Metallic alloys are widely used in orthopedic and dental prostheses due to their mechanical stability, hard tissue compatibility, strong resistance to corrosion and biocompatibility. Corrosion may occur once the prosthesis is integrated into the patient due to the presence of natural defects in alloys, which limits their biocompatibility. A promising strategy to prevent corrosion in metallic implants is to grow TiO2 films on their surface, which act as an extension of the prosthesis to the bone and increase biocompatibility. In addition, silver nanoparticles are well known for their antibacterial properties. In this work, we propose the combination of the biocompatible properties of TiO2 coatings with the antibacterial activity of metallic silver nanoparticles through their synthesis as thin films on 316 L stainless steel. These coatings were prepared by the sol-gel process, a versatile and low-cost synthetic method. The corrosion resistance of 316 L steel samples coated with these films was evaluated by the linear polarization technique using a simulated body fluid (SBF) electrolyte at 37 °C and pH of 7.25. Our results showed a decrease in the corrosion rate of about 70 % for both coated and non-coated samples. Coated samples were characterized by SEM microscopy. The coating was found to be biocompatible with osteoblast cells and exhibited antifungal activity against Aspergillus flavus.

Thermal and plasma enhanced atomic layer deposition of ultrathin TiO2 on silicon from amide and alkoxide precursors: growth chemistry and photoelectrochemical performance

Due to its low cost and suitable band gap, silicon has been studied as a photoanode material for some time. However, as a result of poor stability during the oxygen evolution reaction (OER), Si still remains unsuitable for any extended use. Ultra-thin titanium dioxide (TiO2) films have been used as protective coatings and are shown to enhance Si photoanode lifetime with added solar to hydrogen performance improvements through distancing the oxidation reaction away from the Si photoanode surface and improved charge transport through the anode. This study details the nucleation, growth chemistry, and performance of TiO2 thin films prepared via thermal and plasma enhanced atomic layer deposition (ALD) using both titanium isopropoxide and tetrakis(dimethylamido)titanium as the precursor material. The effect of post ALD treatments of plasma and air annealing was also studied. Films were investigated using photoelectrochemical cell testing to evaluate photoelectrochemical performance, and in-vacuum cycle-by-cycle x-ray photoelectron spectroscopy was used as the primary characterisation technique to study nucleation mechanisms and film properties contributing to improvements in cell performance. TiO2 grown by plasma enhanced ALD results in cleaner films with reduced carbon incorporation. However, despite increased carbon incorporation, thermally grown films showed improved photocurrent as a result of oxygen vacancies in these films. Post deposition annealing in a H2 ambient is shown to further improve photocurrent in all cases, while annealing in atmosphere leads to uniform film chemistry and enhanced photocurrent stability in all cases.

Synthesis and Self-Cleaning Property of TiO₂ Thin Film Doping with Fe3+, Al3+, Ce3+ Ions.

Enhancing the response to visible light and inhibiting recombination of photogenerated electrons and holes is a key point for strongly improved self-cleaning performances of TiO₂ self-cleaning films. In this work, TiO₂ thin film doping with three different ions (Fe3+, Al3+, Ce3+) on glass substrate respectively by sol-gel method to explore the effect of ions on self-cleaning performance of TiO₂ thin films. All the prepared samples are characterized by XRD, SEM, UV-Vis and water contact angle tester. Moreover, the self-cleaning mechanism of doping TiO₂ thin film is discussed. The water contact angle of TiO₂ thin film doping with 9% Fe (molar ratio), 5% Ce and 5% Al are reach at 0°, respectively. In comparison with the water contact angle of pure TiO₂ thin film (2.5°), TiO₂ thin film doping with metal ions exhibit better self-cleaning property.

Effect of voltage on microstructure and its influence on corrosion and tribological properties of TiO2 coatings

To improve the corrosion resistance performance of TiO2 thin films, a coating was prepared on 316 L stainless steel substrate following the electrophoretic deposition process. The structural, surface composition and morphological compositions of TiO2 films were analyzed by Scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD), respectively. Micro-scratch tester was used to investigate the tribological properties and corrosion performance was examined employing electrochemical impedance spectroscopy (EIS) and Potentiodynamic polarization in 3.5 wt.% aqueous NaCl solution. Among the three coatings produced at three different applied voltages, film obtained under 30 V exhibited the lowest corrosion current density value of 0.212 µA as well as the highest charge transfer resistance (the corrosion resistance) and the double layer capacitance, which was attributed mainly to the significant decrease of micro-pore into the film.

Enhanced performance of planar perovskite solar cells using Ce-doped TiO2 as electron transport layer

Electron transport layer plays a key role in improving charge extraction efficiency and inhibiting electron–hole recombination in perovskite solar cells. In this study, Ce ion was doped into compact TiO2 layer to improve electron transport performance of TiO2 thin film. Through UV–Vis and UPS tests, it was found that TiO2 obtained an appropriate band position after Ce ions doping. Specially speaking, Ce-doped TiO2 band position facilitates electron transport at the interface. As a result, the device based on 0.009 M Ce-TiO2 shows the power conversion efficiency is 16.18%, which is 5.75% higher than the device without Ce ions doping. In this work, we provided a new method to improve the electron extraction rate of TiO2 thin film, which is beneficial for performance of the devices.

Photocatalytic Degradation of Different VOCs in the Gas-Phase over TiO2 Thin Films Prepared by Ultrasonic Spray Pyrolysis

In this study, we deposited TiO2 thin films onto borosilicate glass by ultrasonic spray pyrolysis at 350 and 450 °C. The aim of study is to determine the effect of deposition temperature on photocatalytic activity of TiO2 thin films and to investigate the performance of TiO2 thin films on photocatalytic degradation of methyl tert-butyl ether (MTBE), acetone, acetaldehyde, and heptane as functions of different operating parameters. TiO2 thin films deposited at 350 and 450 °C have a thickness value of 190 and 330 nm, respectively. All as-prepared TiO2 films possess an anatase crystalline structure. According to the X-ray photon spectroscopy (XPS) study, the TiO2 thin film deposited at 350 °C showed a higher amount of oxygen vacancies and hydroxyl groups on the film surface after UV treatment. The aged-TiO2 thin film deposited at 350 °C showed a water contact angle (WCA) value of 0° after 10 min UV irradiation, showing superhydrophilic surface behavior. The TiO2 film deposited at 350 °C exhibited the highest amount of conversion of MTBE (100%). The results also showed that TiO2 films are capable of photocatalytic degradation of MTBE (100%) and acetaldehyde (approx. 80%) in humid air conditions and high airflow rate. The visible-light-activity of TiO2 thin films was tested with 5 ppm MTBE and acetone. TiO2 thin films deposited at 350 °C with a surface area of 600 cm2 showed 60% of MTBE and 33% of acetone degradation under VIS light.

Pathways to Tailor Photocatalytic Performance of TiO2 Thin Films Deposited by Reactive Magnetron Sputtering.

TiO2 thin films are used extensively for a broad range of applications including environmental remediation, self-cleaning technologies (windows, building exteriors, and textiles), water splitting, antibacterial, and biomedical surfaces. While a broad range of methods such as wet-chemical synthesis techniques, chemical vapor deposition (CVD), and physical vapor deposition (PVD) have been developed for preparation of TiO2 thin films, PVD techniques allow a good control of the homogeneity and thickness as well as provide a good film adhesion. On the other hand, the choice of the PVD technique enormously influences the photocatalytic performance of the TiO2 layer to be deposited. Three important parameters play an important role on the photocatalytic performance of TiO2 thin films: first, the different pathways in crystallization (nucleation and growth); second, anatase/rutile formation; and third, surface area at the interface to the reactants. This study aims to provide a review regarding some strategies developed by our research group in recent years to improve the photocatalytic performance of TiO2 thin films. An innovative approach, which uses thermally induced nanocrack networks as an effective tool to enhance the photocatalytic performance of sputter deposited TiO2 thin films, is presented. Plasmonic and non-plasmonic enhancement of photocatalytic performance by decorating TiO2 thin films with metallic nanostructures are also briefly discussed by case studies. In addition to remediation applications, a new approach, which utilizes highly active photocatalytic TiO2 thin film for micro- and nanostructuring, is also presented.

Photocatalytic performance of TiO2 thin film decorated with Cu2O nanoparticles by laser ablation

Cu2O nanoparticles decorated TiO2 thin films were fabricated by laser ablation. The effects of Cu2O nanoparticles on the structure, optical properties and photocatalytic performance of TiO2 thin film were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectrometer system, optical absorption and photocatalytic evaluation system, respectively. XRD patterns indicate that the decoration has the effect of lowering the grain orientation of Cu2O. The photocatalytic performance in hydrogen generation of Cu2O decorated TiO2 composite thin film was significantly improved compared with that of either Cu2O nanoparticles or TiO2 single layer thin film with 1.70 and 1.77 times, respectively. The oxidation of Cu2O was demonstrated to dominate the photocatalytic performances of Cu2O/TiO2 composite thin films by varying the laser ablation powers.

Nanostructured TiO2 thin films by chemical bath deposition method for high photoelectrochemical performance

TiO2 thin films were deposited by simple chemical bath deposition method onto conducting and non-conducting glass substrates. The resulting films were annealed at 300°, 400°, and 500 °C for 3 h. In XRD studies, crystallite size and microstrain from x-ray line broadening profile were estimated by Scherrer’s and Williamson-Hall plot method. Also, structural parameters such as unit cell volume, lattice constants, dislocation density, and stacking fault probability have been calculated. Optical absorption spectra illustrate that the band gap energy has been decreased from 3.45 to 3.19 eV with increasing annealed temperatures. Furthermore, the photoluminescence (PL) spectra exhibited two luminescence centers, one is for near-band-edge emission (NBE) and another is for deep level emission (DLE). From FT-IR spectrum of 400 °C annealed film, it was found that strong band around at 609 cm−1 is associated with the characteristic vibrational mode of anatase TiO2. The morphology and elemental composition of the 400 °C annealed film were investigated by field emission scanning electron microscopy (FESEM) and energy dispersive x-ray (EDS) analysis respectively. Present work deals with a significant photoelectrochemical cell performance of TiO2 thin films annealed at 400 °C and explored the cell parameters like conversion efficiency (η) and fill factor (FF). Finally, it was found that the deposited TiO2 films showed the outstanding PEC performance with supreme photoconversion efficiency 1.94%.

Characterization of Au/Fe/Au and Au/Co/Au Magneto-Plasmonic Multilayers as an Ethanol Vapor Sensor

In this paper, we investigate the sensing performance of Au/Fe/Au and Au/Co/Au magneto-plasmonic nanostructures as transducers as well as the performance of TiO2 thin film and TiO2 NPs as sensing layers. A comparison between sensing performance of the traditional surface plasmon resonance (SPR) and the magneto-optic (MO) SPR (MOSPR) transducing techniques is presented here. The surface plasmon wave vector in these transducers which are consisted of metallic and magnetic materials is modulated by external magnetic field in the transverse configuration. Magneto-plasmonic structures show a great enhancement of an MO Kerr effect when the SPR condition is satisfied. As such enhancement strongly depends on the excitation conditions of the surface plasmon polariton (SPP) and, therefore, on the refractive index of the dielectric in contact with the metal layer, we use this enhanced MO signal as the sensing magnitude for investigating molecular interactions between ethanol vapor and TiO2 nanostructures onto the transducers. Besides, when the SPP is excited, applied magnetic field would modulate the SPP wave vector. The modulated nature of MOSPR signal would lead to a higher sensing performance in terms of sensitivity and signal-to-noise ratio with respect to the traditional SPR signal. Moreover, our results show that using TiO2 NPs in the vicinity of multilayer transducers creates a better sensing performance which is caused by porosity and enhancement in the surface area of absorbent layer.

High coloration efficiency, high reversibility and fast switching response of nebulized spray deposited anatase TiO2 thin films for electrochromic applications

Nebulized spray deposited electrochromic oxide thin films have shown better performance in electrochromic application due to the formation of finer particles on the substrate surface and improved contact between the substrate surface and film. In the present work, anatase phase TiO2 thin films with excellent electrochromic performance were prepared using nebulized spray deposition technique. The influence of substrate temperature on the electrochromic performance of TiO2 thin films was studied. In addition, various physical properties of the films were studied. The film prepared at lower substrate temperature of 200°C exhibit a high coloration efficiency of 260.7mCcm−2 at 600nm, fast switching kinetics (bleaching time=1.7s, coloration time=2.37s), high reversibility of 99% and consistent stability of about 1000 cycles. The present report suggests that the nebulized spray deposited TiO2 thin films can perform efficiently in electrochromic applications.

Effect of Ce-doping on the photocatalytic performance of TiO2 thin films

Ce-doped TiO2 thin films were prepared by sol-gel, spin coated on glass substrates, and annealed at 450 °C for 2 h. Solid solubility of Ce in anatase at the lowest doping level (≤0.25 mol% Ce) generated point defects that enhanced nucleation and recrystallization, resulting in relatively uniform grain sizes. In contrast, at ≥0.50 mol% Ce, overdoping, precipitation at grain boundaries, and liquid formation resulted in bimodal nanostructures with decreasing sizes of both the matrix grains and agglomerates owing to the progressive hindrance of Ti diffusion. The optimal photocatalytic performance at 0.25 mol% Ce was associated with a less densely packed array of fine matrix grains, while the performance at higher doping levels was dominated by liquid formation, greater packing densities, and blockage of active sites. The occurrence of Ce ↔ Ti intervalence charge transfer and associated oxygen vacancy formation are likely causes for the observed lowering of the band gap, reduction in the recombination rate, and enhancement of radiation absorption at longer wavelengths (red shift).

Influence of deposition temperature on the optical, structural, morphological, compositional and photoelectrochemical properties of TiO2 thin films

In this investigation, we are reporting a photoelectrochemical (PEC) performance of TiO2 thin films. Initially, TiO2 thin films were synthesized by using a single step hydrothermal method. The influence of temperature on the optical, structural, morphological, compositional and PEC properties of TiO2 thin films is investigated. The optical study reveals direct allowed type of transition. The XRD pattern confirms pure rutile phase with tetragonal crystal structure. The SEM analysis shows morphological transitions from 1D TiO2 nanorods to give a 3D TiO2 nanoflowers with increase in reaction temperature. The compositional data confirms the presence of titanium and oxygen in their respective oxidation state. HRTEM results confirm single crystalline nature of TiO2 thin films. As the reaction temperature increased from 120 to 180 °C photoconversion efficiency is enhanced from 0.33 to 0.47 %. Along with PEC performance electrochemical impedance spectra of all the samples is measured.

Fabrication of SiO2/TiO2 double layer thin films with self-cleaning and photocatalytic properties

Transparent antireflective SiO2/TiO2 double layer thin films were prepared using a sol–gel method and deposited on glass substrate by spin coating technique. Thin films were characterized using XRD, FE-SEM, AFM, UV–Vis spectroscopy and water contact angle measurements. XRD analysis reveals that the existence of pure anatase phase TiO2 crystallites in the thin films. FE-SEM analysis confirms the homogeneous dispersion of TiO2 on SiO2 layer. Water contact angle on the thin films was measured by a contact angle analyzer under UV light irradiation. The photocatalytic performance of the TiO2 and SiO2/TiO2 thin films was studied by the degradation of methylene blue under UV irradiation. The effect of an intermediate SiO2 layer on the photocatalytic performance of TiO2 thin films was examined. SiO2/TiO2 double layer thin films showed enhanced photocatalytic activity towards methylene blue dye.

Preparation and Electrochromic Performance of TiO2 Thin Film

Preparation and Electrochromic Performance of TiO2 Thin Film

Effect of single-cation doping and codoping with Mn and Fe on the photocatalytic performance of TiO2 thin films

TiO2 thin films with varying Mn and Fe dopant levels (0.01–5.00 mol% metal basis; single cation doping and codoping) were deposited on soda-lime-silica glass substrates by spin coating, followed by annealing in air at 450 °C for 2 h. The mineralogical, morphological, optical, and photocatalytic properties of the thin films were determined. The fabricated films were ∼250 nm thick and they were comprised of grains of ∼20–30 nm size. Anatase (or amorphous titania) was the only phase in essentially all the films, with the dopants' being soluble in anatase. All of the films were transparent (∼80%) in the visible region and the optical indirect band gaps were ∼3.4 eV. Photocatalytic testing (≤24 h) showed that the extent of photodegradation decreased with increasing dopant levels. The 0.01 mol% Fe-doped sample showed the best photoactivity since, at this doping level, the negative effects of electron/hole recombination and lattice distortion probably were minimal.

Studies on the Applicability of Artificial Neural Network (ANN) in Evaluation of Photocatalytic Performance of TiO2 thin Film Doped by SiO2

Nanocrystalline films of TiO2 and TiO2:SiO2 with high photocatalytic activity were prepared on glass substrates by the application of sol-gel method. Then the films were subjected to a high temperature treatment at 500°C, which resulted in growth of TiO2 crystals. Afterwards the TiO2:SiO2 films were in contact with an aqueous solution (10 mg.L-1) of methyl orange (MO) and irradiated under UV. The resulted films showed a high photocatalytic activity. In the current study the photocatalytic activity of TiO2 crystals was studied by an Artificial Neural Network (ANN). This was achieved by predicting the concentration of MO in various values of SiO2 concentration and time of degradation. In order to perform the modeling, Multi-layer Perceptron (MLP) network was used in this work, with its learning algorithm being Levenberg-Marquardt (LM). The outcome of modeling showed that there was an excellent agreement between the results of simulation and the data obtained from the experiments. It is worth noting that in the current work, the methods applied in recent papers and patents for the preparation of nanocrystalline films and determination of their photocatalytic performance and also modeling of such processes have been studied.

Micro-arc oxidization fabrication and ethanol sensing performance of Fe-doped TiO2 thin films

In-situ pure TiO2 and Fe-doped TiO2 thin films were synthesized on Ti plates via the micro-arc oxidation (MAO) technique. The as-fabricated anatase TiO2 thin film-based conductometric sensors were employed to measure the gas sensitivity to ethanol. The results showed that Fe ions could be easily introduced into the MAO-TiO2 thin films by adding precursor K4(FeCN)6·3H2O into the Na3PO4 electrolyte. The amount of doped Fe ions increased almost linearly with the concentration of K4(FeCN)6·3H2O increasing, eventually affecting the ethanol sensing performances of TiO2 thin films. It was found that the enhanced sensor signals obtained had an optimal concentration of Fe dopant (1.28at%), by which the maximal gas sensor signal to 1000 ppm ethanol was estimated to be 7.91 at 275°C. The response time was generally reduced by doped Fe ions, which could be ascribed to the increase of oxygen vacancies caused by Fe3+ substituting for Ti4+.