TiO2 Thin Films Research Articles

Microstructural, wettability, and corrosion behaviour of TiO2 thin film sputtered on aluminium

Microstructural, wettability, and corrosion behaviour of TiO2 thin film sputtered on aluminium

Effect of annealing temperature on the structural, optical, morphological, and photocatalytic properties of TiO2 thin films prepared by sol-gel spin-coating and electron beam physical vapor deposition

TiO2 thin films were prepared by sol-gel spin-coating (SGSC) and electron beam-physical vapor deposition (EB-PVD) methods and annealed at different temperatures (Ta ). X-ray diffraction spectroscopy (XRD) results show that the TiO2 films prepared by the SGSC method transformed from the anatase single phase to the coexistence of anatase and rutile with the increase of Ta . However, TiO2 films prepared by the EB-PVD method existed only in the anatase phase, and the crystalline strength was enhanced with the increase of Ta . Meanwhile, particles of TiO2 targets annealed at different Ta showed a rutile phase for TiO2 target particles in the EB-PVD method. The results indicate that the EB-PVD method hinders the nucleation growth and phase transformation of TiO2 films. Scanning electron microscopy and atomic force microscopy also show that the grain size and R ms of TiO2 thin films prepared by the SGSC method increased with the increase of Ta , and the grain size becomes inhomogeneous when the rutile phase is formed. Ultraviolet–visible results show that the forbidden bandwidth and light absorption capacity increase with increasing Ta . For the EB-PVD method, the grain size and surface roughness gradually increased when the Ta of the films was less than 800 °C, while annealing at 800 °C changed the direction of growth and nucleation, and also produced surface cracks; XRD verified the hypothesis that the EB-PVD method hinders the nucleation growth as well as the phase transition of the films. Weak differences in the optical absorption properties and bandgap values of the films also indicate that the EB-PVD method hinders the phase transformation of TiO2 films. Finally, the results of degradation of methylene blue (MB) under simulated visible light showed that the films prepared by the SGSC method gradually improved the photocatalytic performance with the enhancement of the crystalline strength of the anatase phase. The TiO2 films prepared by the EB-PVD method improved the photocatalytic performance with the increase of the active area.

Energy Storage Performance of (Na0.5Bi0.5)TiO3 Relaxor Ferroelectric Film

The (Na0.5Bi0.5)TiO3 relaxor ferroelectric materials have great potential in high energy storage capacitors due to their small hysteresis, low remanent polarization and high breakdown electric field. In this work, (Na0.5Bi0.5)TiO3 thin films with ~400 nm were prepared on (001) SrTiO3 substrate by pulsed laser deposition technology. The (Na0.5Bi0.5)TiO3 films have good crystallization quality with a dense microstructure and relaxor ferroelectric properties, as confirmed by the elongated hysteresis loops and the relation of <A>∝Eα. A high Eb of up to 1400 kV/cm is obtained, which contributes to a good Wrec of 24.6 J/cm3 and η of 72% in (Na0.5Bi0.5)TiO3 film. In addition, the variations of Wrec and η are less than 4% and 10% in the temperature range of 20–120°C. In the frequency range of 103 Hz–2 × 104 Hz, the variations of Wrec and η are less than 10%. All those reveal the great potential of NBT film for energy storage.

Designing Co-coordinated phytic acid 3D network structure for superhydrophilic property of TiO2 nanoparticles

Traditionally, nano-TiO2 as one of the hydrophilic materials has garnered significant attention due to its inherent stability, non-toxicity, and abundance. However, its limited number of hydroxyl groups fails to meet the actual needs for superhydrophilic applications. Therefore, it is crucial to explore a simple and efficient method to introduce more hydroxyl groups to enhance the hydrophilicity of nano-TiO2. In this work, hydroxyl‑rich phytic acid (Pa) was introduced into the surface of nano-TiO2 and a 3D network structure of Co-coordinated phytic acid was further constructed to extremely enhance the hydrophilicity and stability of nano-TiO2. The TiO2@Pa-Co suspension was prepared by adsorbing hydroxyl‑rich Pa molecules on the surface of nano-TiO2 and assembling Co-coordinated Pa and then modified onto a glass slide by a conventional spin-coating method to obtain TiO2@Pa-Co thin film. The hydrophilic performance tests demonstrated that the TiO2@Pa-Co thin film presented innate superhydrophilic properties, as evidenced by a water contact angle of 2.0°, significantly smaller than that of the blank TiO2 (65.0°) and TiO2@Pa (29.1°) thin films. Notably, it also displays good durability, corrosion resistance, and anti-fogging properties. The superhydrophilic performances can be attributed to the ability of phytic acid to offer a large number of hydroxyl groups for improving the hydrophilicity of TiO2, while the Co ions act as a bridge, connecting with Pa and further construct a 3D network structure for the enhanced hydrophilic stability of TiO2. This study presents an inventive design concept to prepare superhydrophilic and stable TiO2 thin film by developing an organo-metallic coordination layer.

Impact of Graphene oxide (GO) and reduced Graphene Oxide (rGO) on the TiO2 thin film composite (TiO2: GO/ rGO) photoanodes

Graphene and its derivatives have several advantages such as large surface area, great chemical stability, high transmittance, and good electrical conductivity, which are the fundamental qualities required by photovoltaic industries. GO and rGO are mixed in various proportions ranging 0 wt.% - 15 wt.% to spin coat TiO2: GO/rGO composite thin films. The effect of graphene oxide and reduced graphene oxide on the performance the TiO2 based composite photoanodes are obtained. A tetragonal anatase phase of TiO2 was confirmed by the XRD analysis. The calculated crystallite size decreases with lower concentrations of GO and rGO but starts to increase for higher concentrations. The spectrophotometer studies have confirmed that the optical bandgap of pure TiO2 films is decreased on doping with GO and rGO. The SEM analysis have confirmed that the surface is tightly packed with the uniformly distributed grains, and they are very compact.

Al-Mg co-doped TiO2 thin film as a promising ETL for perovskite solar cells: An experimental and DFT investigation

Solar cells offer a potential solution to the energy crisis, and perovskite solar cells are the latest frontrunner. However, low electrical conductivity of TiO2 ETL serves as a bottleneck to its efficiency. In this study, Al-Mg co-doped anatase thin films are prepared by one-step spin coating method and then characterized to tackle this problem. XRD results show that doping leads to smaller crystallite size and decreased interplanar spacing, but increases the lattice strain and dislocation density. AFM images reveal that Al-Mg co-doping increases surface roughness. Surface morphology of the co-doped film is good, covering the whole substrate uniformly without any pinholes. XPS results ensure that the desired composition is achieved. UV–vis spectroscopy data show that optical bandgap increases with Al-Mg co-doping, leading to the highest bandgap for Ti0.87Mg0.1Al0.03O2, which also has the highest transmittance peak, reaching 90 % in the visible region. Urbach energies are also calculated to get a better estimate of the effective bandgaps. Band edge positions are calculated using Mulliken’s electronegativity, demonstrating improved band alignment due to Al-Mg co-doping. The bandgap trend is further corroborated with DFT + U simulations, which show that calculated bandgaps match the experimentally obtained optical bandgaps. Additionally, density of states reveal that Ti 3d orbital dominates the conduction band and O 2p orbital dominates the valence band, with hybridization taking place between different orbitals. Four-point probe test demonstrates that Al-Mg co-doping leads to a consistent decrease in sheet resistance of the thin film. Better band alignment and higher visible light transmittance combined with enhanced conductivity indicate that Al-Mg co-doped anatase thin film has high potential as an ETL for perovskite solar cells.

Triadic metal chalcogen HgBi2S3 nanoparticles as sensitizers for TiO2 thin film: SILAR synthesis and characterization

Triadic metal chalcogen HgBi2S3 nanoparticles as sensitizers for TiO2 thin film: SILAR synthesis and characterization

Gallium-incorporated TiO2 thin films by atomic layer deposition for future electronic devices

Gallium-incorporated TiO2 thin films by atomic layer deposition for future electronic devices

Properties Enhancement of Cu2O/TiO2 Heterostructure Film Using Two-step Hydrothermal and Potentiostatic Deposition Method

Two-steps hydrothermal were demonstrated to create a high efficiently interfacial layer of TiO2 thin film. The first hydrothermal was conducted to synthesize a well-aligned and compact structure of TiO2 nanorods on FTO substrate. Etching treatment in an acidic medium of hydrochloric acid (HCl) as a second hydrothermal favors increasing the surface area prior to any deposition to be a heterostructure film. The morphology of nanorods changed while the electrical resistivity decreased, demonstrating that the etching treatment had a substantial effect on the TiO2 thin film properties. Cyclic voltammetry (CV) was conducted prior deposition. The electrodeposition of Cu2O on the TiO2 thin film was fabricated by using copper acetate-based solution with pH value of 12.0 at bath temperature of 60°C. The finding revealed that the pyramidal structure of Cu2O film was deposited uniformly, which is believed that the properties of TiO2 interfacial layer were excellently improved.

Chemi-resistive behavior of spray deposited Cu-doped TiO2 thin films: application in hydrogen sensing devices

Chemi-resistive behavior of spray deposited Cu-doped TiO2 thin films: application in hydrogen sensing devices

Influence of oxygen pressure during deposition on the microwave dielectric tunability of Ba0.5Sr0.5TiO3 thin films in PLD process

Thin films of Ba0.5Sr0.5TiO3 (BSTO) were pulsed laser deposited on platinized silicon substrates with varying oxygen pressure from 5 × 10−1 mbar to 5 × 10−6 mbar. A strong correlation between the oxygen partial pressure during the PLD process and the structural and microwave dielectric properties of the PLD-grown BSTO thin films is observed. The structural properties of the PLD-grown BSTO films were analyzed by XRD, Raman spectroscopy, FTIR spectroscopy, and XPS studies, and it is observed that oxygen vacancies are formed in low oxygen pressure deposited films. Dielectric studies at microwave frequencies show that high oxygen pressure deposited BSTO films show good microwave dielectric properties and crystallinity. At 1 GHz frequency, the BSTO film grown at 5 × 10−2 mbar oxygen pressure exhibits a dielectric constant ∼470 and dielectric loss ∼0.15. The oxygen vacancies change the nature of metal-oxide bonding (Ti-O bond), affect the polarizabilities, and, as a result, reduce the dielectric constant. A maximum dielectric tunability of 71 % is observed in microwave frequencies for the BSTO films grown at 5 × 10−2 mbar oxygen pressure.

Crystalline as-deposited TiO 2 anatase thin films grown from TDMAT and water using thermal atomic layer deposition with in situ layer-by-layer air annealing

We report a new thermal atomic layer deposition (thermal-ALD) process including an air exposure as a third precursor to deposit crystalline TiO2 anatase thin films from tetrakis(dimethylamido)titanium(IV) (TDMAT) and water at deposition temperatures as low as 180 °C and film thicknesses as low as 10 nm. This ALD process enables TiO2-antase crystal growth during the deposition at low temperatures (< 220 °C). This additional oxidant pulse is used to fully oxidize the Ti to a 4+ state in the amorphous film, lowering the barrier to crystalline anatase formation. This new approach is informed by preliminary studies of post-deposition annealing (PDA) of thermal ALD films in both nitrogen and air atmospheres, which demonstrate the importance of having an oxidizing atmosphere to achieve the nucleation of the crystalline anatase phase. This oxidizing atmosphere is subsequently introduced into the ALD cycle as a third precursor and is shown to be more effective and efficient in promoting the crystalline transformation than even by post-deposition annealing. The crystalline anatase phase is verified by Raman spectroscopy and grazing incidence X-ray diffraction (GIXRD). The mechanism for crystallization during the TDMAT/H2O/air ALD cycle is probed by chemical state analysis via X-ray photoelectron spectroscopy (XPS). We propose that sub-oxidation in TiO2 thin films deposited by the thermal-ALD process inhibits crystallization during ALD from TDMAT/H2O chemistry. Scanning electron microscopy (SEM) is used to investigate the microstructure of these TiO2 thin films as a function of thickness (5 nm to 50 nm) and deposition temperature (180 °C to 220 °C). The reported layer-by-layer air anneal process is found to crystallize entire films in shorter total process times than thermal-ALD with ex situ post deposition annealing at identical temperatures, presumably due to the improved surface diffusion kinetics accessed during the deposition process.

Characterization of the structure, morphology, and optical properties of titanium dioxide thin film deposited by spray pyrolysis technique for self-cleaning glass

Abstract The research in material science has actively pursued the creation of self-cleaning materials, especially for windows. Titanium dioxide (TiO2) is considered a promising substance for developing hydrophilic self-cleaning surfaces due to its photocatalytic activity. In this research, TiO2 nanoparticles were synthesized using TiCl3 as the precursor and co-precipitation as the experimental method in order to obtain anatase phase. The nanoparticles, then, was deposited by spray pyrolysis technique with different spraying time; 1, 2, 3, and 4 minutes and different types of TiO2 nanoparticles—synthesis and commercial—as the primary variations. TiO2 thin film was formed using ethyl cellulose as binder and isopropyl alcohol as solvent. The synthesized TiO2 nanoparticles and deposited thin film were, then, characterized using XRD, Maud software, UV-Visible Spectrophotometer, optical microscope, and SEM. The higher band gap energy value of TiO2 thin films was obtained with the average of 3.746 eV and 3.744 eV for TI(S) and TI(C), respectively, as a result of ethyl cellulose composition on the thin film. The thin film was categorized as hydrophilic.

Analyze photocatalytic degradation of methylene blue using TiO2 deposited onto conductive and non-conductive substrates under UV-C light

Abstract Degradation of methylene blue has been extensively studied by using TiO2 thin film as photocatalyst deposited onto non-conductive substrates. In this research, we proposed to utilize TiO2 thin film deposited onto conductive substrate, i.e., PCB. We compared concentration degradation between TiO2 thin film deposited onto conductive and non-conductive substrates. In this study, a photocatalysis process was carried out to decompose methylene blue pollutants. This research aims to obtain the performance of TiO2 photocatalyst coated with spray coating method on conductive and non-conductive substrates using UV-C light. This research begins with the manufacture of photocatalysis reactor, manufacture and coating of substrate, manufacture of methylene blue solution, concentration calculation. In this study, two types of thin layer substrates were made using the spray coating method. The first substrate is made using acrylic material as a non-conductive substrate, the second material uses a conductive substrate, PCB. The results shows that concentration of conductive and non-conductive substrates decreases 51% and 33,3 %, respectively. Therefore, conductive substrate may increase photocatalytic process. The use of substrates that are conductors can conduct electrons well, so that when interacting with TiO2, electrons generated by the photocatalysis process can move more easily. Acrylic and PCB materials are distinguished based on the ability to conduct electricity. Acrylic as an insulator and PCB acts as a conductor substrate.

Effects of annealing temperature and ion doping on energy storage performance of Na0.5Bi0.5TiO3-Based thin films

Lead-free ferroelectric thin film capacitors offering superb power density and fast charge-discharge rates are ideal for energy storage applications. However, the trade-off relationship between polarization strength and breakdown strength significantly hinders the improvement of energy storage performance. In this work, relaxor-ferroelectric Na0.5Bi0.5TiO3 (NBT) thin films have been deposited on Pt/Ti/SiO2/Si substrate via sol-gel method. First, the energy storage performance of the films is optimized by adjusting the annealing temperature. It is found that the NBT film annealed at 650 °C has both excellent breakdown strength and polarization strength. Then the influence of ion doping on the energy storage performance of NBT films has been studied. An excellent energy storage density of 42.1 J/cm3 and efficiency of 55.8 % are simultaneously achieved in the 2 % Mn-NBT thin film. Additionally, the energy storage performance remains stable within the temperature range of 25–180 °C and frequency range of 500–5000 Hz. The energy storage performance of 2 % Mn-NBT thin film did not decrease significantly after 107 electrical cycles. It is predicted that this work will advance the utilization of Na0.5Bi0.5TiO3-based film capacitors in energy storage systems.

Photoelectrode FTO/ Anodized TiO2 Production and Characterization for Methylene Blue Affected Photoelectrochemical Decomposition

Background: The production of thin film TiO2 nanostructured systems for electrocatalytic, photocatalytic, and photoelectrocatalytic applications has been an essential topic in recent years. Due to the light-sensitive effect of TiO2, it can be produced by various methods and used as a photoelectrode to remove dye. Using magnetron sputtering, Ti thin films can be deposited on different substrates and converted into transparent TiO2 structures by electrochemical anodization. Methods: In this study, the thin Ti film was produced using a magnetic spraying technique on the FTO substrate, and then an anodic TiO2 structure was obtained by the anodization technique. TiO2 films produced by the anodizing technique were used as a photoelectrode for the degradation of MB. The reactor contained 400 mL of 20 mg/L MB solution at 20 °C. The produced photoelectrode was characterized by the SEM/EDS, FTIR, XRD, and UV-Vis Spectrophotometer analyses. Results: The EDS analysis confirmed the presence of titanium and oxygen in the FTO/ Anodized TiO2 photoelectrode. The XRD results showed that all the peaks of the produced FTO/ Anodic TiO2 were associated with the anatase phase of TiO2. According to the FTIR spectroscopy, the functional groups of the anodized TiO2 were obtained for the FTO/ Anodized TiO2. The electrocatalytic, photocatalytic, and photoelectrocatalytic degradation experiments were performed with the degradation of the dye solution of MB on the FTO/ Anodic TiO2 photoelectrode, and the rates of dye degradation were determined as 17.12%, 64.67%, and 82.12%, respectively. Conclusion: This study showed that the methylene blue dye of FTO/ Anodic TiO2 is a suitable photoelectrode for electrocatalytic, photocatalytic, and photoelectrocatalytic degradation.

Optical and photocatalytic properties of sol-gel AuNPs@TiO2 ultrathin film

The optical and photocatalytic properties of ultrathin TiO2 layers were investigated in order to stress out the effect of nanoscale thickness on the film properties. The method relies on monitoring localized surface plasmon resonance (LSPR) through UV–visible spectroscopy and enhanced Raman spectroscopy (SERS). To achieve this, TiO2 thin films were prepared using the sol–gel method on high density gold nanoparticles arrays (AuNPs). TiO2 anatase phase was obtained by thermal annealing and confirmed by XRD, HRTEM, and SERS. Our results reveal that the thinnest TiO2 layers consist of compact TiO2NPs of small dimensions and lower porosity compared to the thicker TiO2NPs layers. Subsequently, these thin TiO2 layers functionalizing AuNPs were applied in plasmonic photocatalysis, specifically for the N-demethylation of methylene blue in the visible range. When comparing layers with the same thickness (a single deposition layer with layers prepared by stacking various thin layers), the stacked layers demonstrated enhanced photocatalytic activity. This novel, stable form of TiO2 has the potential to open numerous opportunities in the fields of photocatalysis and detection.

Real-time and highly responsive hydrogen mapping in pure Fe using TiO2 thin films

A hydrogen visualization method with high responsivity and chemical stability under atmospheric corrosion is necessary to inhibit hydrogen embrittlement, which can occur with hydrogen uptake of structural materials. In this study, a highly responsive hydrogen mapping technique for steels was successfully established using a TiO2 thin film and Pd intermediate layer. The color of the TiO2 film on the hydrogen-detection side changes during hydrogen charging on the hydrogen-entry side of the Fe specimen, indicating that the color changes were attributed to the hydrogen uptake of the Fe surface and subsequent introduction of hydrogen atoms to the TiO2 film. Considering the responsivity and visibility, the optimal thickness of the TiO2 film was determined to be 20 nm. As TiO2 is a chemically stable material, the proposed mapping technique can be used to monitor the hydrogen absorbed into metallic materials under outdoor conditions.

Effect of doping on the structural, optical and electrical properties of TiO2 thin films for gas sensor

Effect of doping on the structural, optical and electrical properties of TiO2 thin films for gas sensor

Electronic relaxation in PLD TiO2 films processed with femtosecond UV-laser

Modifications of shallow electron trap states near conduction band was analyzed after surface structuring of TiO2 thin films prepared via pulsed laser deposition method. Laser-induced periodic surface structures (LIPSS) were produced on the large-area films after irradiation with femtosecond KrF laser (λ = 248 nm). While spatial period of LIPSS Λ ≈ 190 ± 10 nm was not affected by laser fluence, coherence was increased with an increase of laser dose. Time-resolved microwave conductivity measurements accompanied by theoretical modelling revealed energetic positions of shallow electron trap states, connected to LIPSS. A possibility to alter the trap states energy via surface structuring of the material was shown.