Thickness Of TiO2 Layer Research Articles

Parameters to be considered for the development of highly photoactive TiO2 layers on aluminium substrates by RF magnetron sputtering for treating polluted air

In this study, photoactive titanium dioxide films deposited on aluminium substrates using Radio-Frecquency (RF) magnetron sputtering have been developed, with the goal of advancing this technology for indoor air treatment. With this goal in mind, the influence of deposition parameters, namely post annealed heat treatment, working pressure and deposition time, on the physico-chemical properties of the layers has been studied. Photocatalytic efficiency for trichloroethylene degradation in gas phase, and self-cleaning performance of the developed materials have been evaluated. Samples have been thoroughly examined using different techniques (SAXRD, UV-Vis, SEM-EDX, contact angle, profilometry, hardness, among others) in order to determine the structural-photocatalytic relationship. The findings indicate that high-temperature annealing promotes the diffusion of alumina, copper and iron ions towards the surface of the samples resulting in the formation of aluminium alloys. These alloyed species can act as recombination centres adversely affecting the photocatalytic activity. The sputtering pressure also affects the nature of the titanium phases formed during the sputtering. Increasing the thickness of the TiO2 layer leads to rougher surfaces with TiO2-anatase as the predominant crystal phase. Annealing temperatures of 350 °C, argon pressures between 0.8 and 1.0 Pa, and TiO2 layer thickness of ca. 110 nm are the optimal conditions to prepare well-adhered TiO2 layers with high photocatalytic performance. UV-A photoinduced superhydrophilicity phenomena was observed for all TiO2/Al materials.

Influence of TiO2 Space layer on plasmon enhanced Luminescence of Ag/TiO2/NaGdF4:Er3+/Yb3+/Al3+ composite Films

ABSTRACT Lanthanide-doped upconversion nanoparticles (UCNPs)have potential applications in optical and optoelectronic devices due to their novel optical properties. The surface plasmon is an effective method in improving the upconversion luminescence (UCL) properties, and it is essential to tunee the distance between the metal NPs and UCNPs for improving UCL. In this work, the Ag/TiO2/NaGdF4:Er3+/Yb3+/Al3+ composite films were fabricated, and the effect of the TiO2 layer thickness on spectral characteristics in the composite films was investigated. It is shown that the thickness of TiO2 film has a significant effect on the Ag NPs plasma resonance and fluorescence intensity. The maximum upconversion emission enhancement factors of the red and green emission were obtained for the sample with 15-nm-thickness TiO2 under the 980 nm excitation. That is mainly originated from the enhancement of the resonate energy transfer (Yb3+→Er3+) rate under the competition between non-radiative transition and local field effects.

Visible-light photocatalytic degradation of dyes by TiO[formula omitted]–Au inverse opal films synthesized by Atomic Layer Deposition

TiO2–Au composite planar films and inverse opals were synthesized by Atomic Layer Deposition (ALD) using Direct Liquid Injection for TiO2 deposition and for the injection of preformed Au nanoparticles (NPs). A few nanometers thick layer of TiO2 was deposited after the Au NPs. Thermal annealing at 380 °C allowed to remove the polystyrene beads template and to form anatase TiO2.The obtained inverse opals have a layered structure of hollow TiO2 spheres interconnected by channels formed at the template beads contacts. Au NPs are homogeneously distributed on the surface. Their localized surface plasmon resonance (SPR) at 587 nm confirm that they are embedded in TiO2. These photocatalysts were tested for the degradation of methylene blue solutions under visible-light illumination. A significant photocatalytic effect is reported with a 95% degradation after 7 h of exposure only for the composite inverse opal. This results from the transfer of hot electrons from the NPs excited at their SPR to the conduction band of TiO2. They generate reactive oxygen species at the surface of TiO2 which are involved in the initial stage of MB degradation. These results highlight the potential of ALD for the fabrication of complex composite structures for application in photocatalysis.

Photonic band gap analysis of 1D TiO2/SiO2 photonic crystals using plane wave method for thin film solar cell applications

The properties of photonic crystals that allow or inhibit the propagation of electromagnetic (EM) waves in between photonic band gap (PBG) regimes have proved to be significant. In this work, we investigated the PBG analysis of one-dimensional TiO2/SiO2 photonic crystal using plane wave method (PWM). The PBG width depends of on the various optical parameters such as lattice constant (Λ), center wavelength (λc), thickness of the layers (d), dielectric constant (ε) and refractive indices (n). Among various parameters, the center wavelength (300-1100nm), the thickness of TiO2 (28-103 nm) and SiO2 (51-189 nm) layers were optimized for the tuned bandgap. The obtained results revealed that the PBG shifting towards the lower frequency region and reducing the size due to the increment of center wavelength and thicknesses. This result is useful for the understanding the way of photon propagation within artificial structure and it could be possible for the better back reflector in thin film solar cells.

KESAN KETEBALAN LAPISAN PENGANGKUT ELEKTRON TIO2 TERHADAP PRESTASI SEL SURIA ORGANIK: KAJIAN SIMULASI

Organic solar cell has gained more attention due to its low-cost production and easy fabrication process. However, the power conversion efficiency (PCE) is still low as compared to that of inorganic solar cell. One of the approaches to improve the PCE of organic solar cell is by introducing an electron transport layer which can extract the electrons effectively in between photoactive layer and cathode. Simulation study using SCAPS (Solar Cell Capacitance Simulator) software was conducted to examine the effects of TiO2 electron transport layer thickness on the performance of organic solar cell with ITO/TiO2/P3HT:PCBM/Ag structure. P3HT:PCBM acted as photoactive layer, whereas ITO and Ag played roles as cathode and anode, respectively. The range of studied thickness was from 30 to 180 nm. The simulation result indicates that the PCE increased with TiO2 layer thickness in the range of 30 to 120 nm, and it saturated when the TiO2 layer thickness was further raised to 180 nm. The highest PCE of 2.139% was obtained at TiO2 layer thickness of 180 nm.

MoS2 Transistors with Low Schottky Barrier Contact by Optimizing the Interfacial Layer Thickness

Molybdenum disulfide (MoS2) has attracted great attention from researchers because of its large band gap, good mechanical toughness and stable physical properties; it has become the ideal material for the next-generation optoelectronic devices. However, the large Schottky barrier height (ΦB) and contact resistance are obstacles hampering the fabrication of high-power MoS2 transistors. The electronic transport characteristics of MoS2 transistors with two different contact structures are investigated in detail, including a copper (Cu) metal–MoS2 channel and copper (Cu) metal–TiO2-MoS2 channel. Contact optimization is conducted by adjusting the thickness of the TiO2 interlayer between the metal and MoS2. The metal-interlayer-semiconductor (MIS) structure with a 1.5 nm thick TiO2 layer has a smaller Schottky barrier of 22 meV. The results provide insights into the engineering of MIS contacts and interfaces to improve transistor characteristics.

Nanoscale TiO2 Coatings Improve the Stability of an Earth-Abundant Cobalt Oxide Catalyst during Acidic Water Oxidation.

The large-scale deployment of proton-exchange membrane water electrolyzers for high-throughput sustainable hydrogen production requires transition from precious noble metal anode electrocatalysts to low-cost earth-abundant materials. However, such materials are commonly insufficiently stable and/or catalytically inactive at low pH, and positive potentials required to maintain high rates of the anodic oxygen evolution reaction (OER). To address this, we explore the effects of a dielectric nanoscale-thin layer, constituted of amorphous TiO2, on the stability and electrocatalytic activity of nanostructured OER anodes based on low-cost Co3O4. We demonstrate a direct correlation between the OER performance and the thickness of the atomic layer deposited TiO2 layers. An optimal TiO2 layer thickness of 4.4 nm enhances the anode lifetime by a factor of ca. 3, achieving 80 h of continuous electrolysis at pH near zero, while preserving high OER catalytic activity of the bare Co3O4 surface. Thinner and thicker TiO2 layers decrease the stability and activity, respectively. This is attributed to the pitting of the TiO2 layer at the optimal thickness, which allows for access to the catalytically active Co3O4 surface while stabilizing it against corrosion. These insights provide directions for the engineering of active and stable composite earth-abundant materials for acidic water splitting for high-throughput hydrogen production.

Effect of TiO2 layer thickness on the energy conversion efficiency of dye-sensitized solar cells

The past two decades have seen the unprecedentedly rapid emergence of dye-sensitized solar cells that are efficient, inexpensive, and eco-friendly. However, a systematic study of the dependence on active layer thickness into energy conversion efficiency (ECE) of solar cells has not been reported often. In this study, we synthesized the TiO2 nanoparticles with various particle sizes and fabricated TiO2 nanoparticle-based dye-sensitized solar cells with different thickness of the TiO2 active layers. Then, a systematic study was carried out to enhance the ECE and found that as the thickness of TiO2 active layers increases, the ECE could improve from 3.77% to 5.10%. This is an enhancement of as much as 26%. Therefore, it can be concluded that the optimal TiO2 layer thickness in dye-sensitized solar cells (DSSC) depends on the particle size due to back scattering and charge transport properties.

Fabrication and characterisation of ZnO@TiO2 core/shell nanowires using a versatile kinetics-controlled coating growth method

This study aims to provide a strategy for fabricating a scalable and reproducible ZnO@TiO2 heterostructure with precisely engineered TiO2 layer thickness by employing a simple wet chemical method to fabricate Zinc oxide nanowires (ZnO NWs) with a titanium oxide (TiO2) shell. It is also directed at investigating the impact of the reaction parameters: temperature, time and ammonia concentration, on the heterostructure, as well as the influence of photonic annealing on both ZnO NWs and ZnO@TiO2 heterostructure. Transmission, scanning electron microscopy, X-ray mapping and X-ray diffraction confirmed the ZnO@TiO2 heterostructure morphology, its shell thickness and presence of its elements. They also indicated that one hour was sufficient to produce the TiO2 shell at room temperature. In addition, both the reaction time and temperature did not impact on the TiO2 shell thickness. However, changing ammonia content from 300 µl to 400 µl significantly increased the TiO2 shell thickness from ∼2.5 nm up to ∼90 nm. The 2.5 nm shell showed an anatase crystalline structure whilst the thicker shells were mostly amorphous. X-ray photoelectron spectroscopy confirmed that the oxidation state of Ti was consistent with TiO2. Photoluminescence measurements showed a large improvement in the optical properties of ZnO NWs after forming the TiO2 shell, increasing the intensity of the UV band relative to the visible band by a factor of 4.5. The photonic annealing process showed a greater improvement by a factor of 7.1 for the ZnO@TiO2 heterostructure and tenfold for bare ZnO nanowires.

Transformations of the Microstructure and Phase Compositions of Titanium Alloys during Ultrasonic Impact Treatment Part II: Ti-6Al-4V Titanium Alloy

Experimental and theoretical studies enabled the reveal of patterns of the microstructure formation in the surface layer of Ti-6Al-4V titanium alloy subjected to ultrasonic impact treatment. The mixed amorphous and nanocrystalline structure of the 200 nm thick uppermost surface layer of titanium dioxide TiO2 was demonstrated using transmission electron microscopy. The 5 µm thick intermediate layer containing nanocrystalline α grains, and the 50–60 µm thick lower layer containing fragmented α-Ti grains with retained β phase were also observed. The refinement of the β-Ti phase during ultrasonic impact treatment was accompanied by the formation of the orthorhombic (α″) martensitic phase. Molecular dynamics simulation of strains of a vanadium-doped titanium crystallite subjected to ultrasonic impact treatment revealed the formation of striped dislocation substructures as well as the development of reversible β→α phase transformations. Ab initio calculations of the atomic structure of V-doped Ti crystallites containing α, β or α″ phases of titanium were carried out. On the basis of the results of the experimental observations, a molecular dynamics simulation and ab initio calculations a mechanism was proposed, which associated the development of the strain-induced β→α″ phase transformations in Ti-6Al-4V alloy with the presence of oxygen. The role of the electronic subsystem in the development of the strain-induced phase transformations was discussed.

Design of hybrid Au grating/TiO2 structure for NIR enhanced photo-electrochemical water splitting

Titanium oxide is commonly considered as an effective catalyst for photo-electrochemical water splitting due to its low cost, high activity, and perfect stability. However, a wide bandgap of TiO2 prevents the utilization of visible and near-infrared photons in the photo-electrochemical process. Photosensitization of TiO2 with plasmon active nanostructures was proposed as a way to solve this problem but the optimal design of coupled TiO2-plasmonic nanostructures, as well as the exact mechanism of plasmon triggering, are still under debate. In this work, we propose a plasmon-based TiO2 photosensitization, using the gold grating, covered by homogenous TiO2 layer. The gold grating supports the excitation and propagation of surface plasmon polariton wave (SPP), which is responsible for TiO2 triggering (unlike common localized plasmon resonance commonly used for TiO2 activation). For the optimization of the present structure design, we studied the impact of TiO2 layer thickness, illumination regime, and spatial distribution of plasmonic evanescent wave energy with regards to the mechanism of TiO2 activation. Obtained results proved that the proposed structure can be used for efficient photo-electrochemical water splitting and hydrogen production under irradiation with NIR photons of 700–1000 nm wavelengths. It was also verified that for a certain TiO2 layer thickness the activation of catalytic activity is mostly due to the plasmon electric field, which is concentrated at the electrolyte/catalyst surface.

Interfacial Dipole Layer Enables High-Performance Heterojunctions for Photoelectrochemical Water Splitting

TiO2 has been widely used as an n-type overlayer, simultaneously serving as a protective layer for photocathodes. However, the photovoltage generated from a TiO2 junction with p-type absorbers, such as p-Si, Sb2Se3, SnS, and Cu2O, is insufficient. We report a dipole reorientation strategy to overcome this limitation by inserting a polyethylenimine ethoxylated (PEIE) layer between a p-type absorber and TiO2. Furthermore, we demonstrate that the PEIE dipole orientation can be rearranged by increasing the layer thickness, leading to an upward shift of the TiO2 band edge. The magnitude of band shift induced by the dipole effect depends on the TiO2 layer thickness. Using this approach, the onset potential was significantly improved to 0.5 V versus the reversible hydrogen electrode (VRHE) in a p-Si/PEIE/TiO2/Pt device. The versatility of the effective dipole reorientation strategy was demonstrated by application to a range of TiO2-protected heterojunction photocathodes based on Sb2Se3, Cu2O, and SnS.

Preparation of WO3/Mo/CrNi/TiO2 Composite Multifunctional Photothermal Conversion Films With Self-Cleaning and Low Emissivity

To improve the sunlight transmittance and infrared reflectivity, different membrane compositions are designed to realize self-cleaning and low emissivity of the membrane. The WO3/Mo/CrNi/TiO2 composite film was prepared by magnetron sputtering technology, and the complementary effect of these films with four different argon/oxygen ratios of TiO2 layer and different film thicknesses was analyzed. The microstructure characterization proves that the self-cleaning function of the composite film is determined by the photocatalytic properties and superhydrophilic properties of the TiO2.

Magnetron sputtered TiO2/CuO heterojunction thin films for efficient photocatalysis of Rhodamine B

TiO2-based heterojunction nano-thin films are competitive photocatalysts for water pollution treatment due to their abundant availability, non-toxicity, and rapid separation of photogenerated charge carriers. Moreover, the layer thickness, as a vital factor influencing the photocatalytic properties of TiO2-based heterojunction nano-thin films, requires further exploration. Herein, we prepared heterostructured TiO2/CuO nano-thin films by a facile magnetron sputtering approach. The TiO2 nanoparticles were uniformly deposited onto the underlayer CuO to construct heterojunction, and the thickness of the upper TiO2 layer and underlying CuO layer were precisely controlled by simply varying the sputtering time. The samples were described via SEM, XRD, Raman, AFM, and UV–vis DRS analysis. The SEM results exhibited that the optimized heterojunction thin film was composed of the underlying CuO layer with a thickness of 90 nm and the upper TiO2 layer with a thickness of 120 nm. The optical absorption studies of this nano-film showed two band gaps of 1.8 and 3.1 eV. The CuO/TiO2 heterojunction nano-film (1 cm × 1 cm) exhibited superior photocatalytic activity, by degrading 92.94% Rhodamine B (RhB) within 120 min duration under a 300 W high-pressure mercury lamp illumination, which benefited from the better crystalline structure, more active sites, and the effective electrons and holes transfer. Moreover, a possible charge transfer mechanism of TiO2/CuO nano-thin film was proposed based on the results of the capture experiment.

Solution-Processed All-Solid-State Electrochromic Devices Based on SnO2/NiO doped with Tin

We investigated the photochromic (PC) and electrochromic (EC) properties of tin-doped nickel oxide (NiO) thin films for solution-processable all-solid-state EC devices. The PC effect is shown to be enhanced by the addition of Sn into the precursor NiO solution. We fabricated an EC device with six layers—ITO/TiO2 (counter electrode)/SnO2 (ion-conducting layer)/SiO2 (barrier)/NiO doped with tin (EC layer)/ITO—by a hybrid fabrication process (sputtering for ITO and TiO2, sol–gel spin coating for SnO2 and NiO). The EC effect was also observed to be improved with the Sn-doped NiO layer. It was demonstrated that UV/O3 treatment is one of the critical processes that determine the EC performance of the hydroxide ion-based device. UV/O3 treatment generates hydroxide ions, induces phase separation from a single mixture of SnO2 and silicone oil, and improves the surface morphology of the films, thereby boosting the performance of EC devices. EC performance can be enhanced further by optimizing the thickness of TiO2 and SiO2 layers. Specifically, the SiO2 barrier blocks the transport of charges, bringing in an increase in anodic coloration. We achieved the transmittance modulation of 38.3% and the coloration efficiency of 39.7 cm2/C. We also evaluated the heat resistance of the all-solid-state EC device and found that the transmittance modulation was decreased by 36% from its initial value at 100 °C. Furthermore, we demonstrated that a large-area EC device can be fabricated using slot-die coating without much compromise on EC performance.

Biopolymer‐Templated Deposition of Ordered and Polymorph Titanium Dioxide Thin Films for Improved Surface‐Enhanced Raman Scattering Sensitivity

AbstractTitanium dioxide (TiO2) is an excellent candidate material for semiconductor metal oxide‐based substrates for surface‐enhanced Raman scattering (SERS). Biotemplated fabrication of TiO2 thin films with a 3D network is a promising route for effectively transferring the morphology and ordering of the template into the TiO2 layer. The control over the crystallinity of TiO2 remains a challenge due to the low thermal stability of biopolymers. Here is reported a novel strategy of the cellulose nanofibril (CNF)‐directed assembly of TiO2/CNF thin films with tailored morphology and crystallinity as SERS substrates. Polymorphous TiO2/CNF thin films with well‐defined morphology are obtained by combining atomic layer deposition and thermal annealing. A high enhancement factor of 1.79 × 106 in terms of semiconductor metal oxide nanomaterial (SMON)‐based SERS substrates is obtained from the annealed TiO2/CNF thin films with a TiO2 layer thickness of 10 nm fabricated on indium tin oxide (ITO), when probed by 4‐mercaptobenzoic acid molecules. Common SERS probes down to 10 nm can be detected on these TiO2/CNF substrates, indicating superior sensitivity of TiO2/CNF thin films among SMON SERS substrates. This improvement in SERS sensitivity is realized through a cooperative modulation of the template morphology of the CNF network and the crystalline state of TiO2.

Photocatalytic Crystalline and Amorphous TiO2 Nanotubes Prepared by Electrospinning and Atomic Layer Deposition.

In this work core/shell composite polymer/TiO2 nanofibers and from those TiO2 nanotubes were prepared. First, poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) fibers were synthetized by electrospinning. They were covered with a 100 nm thick amorphous TiO2 layer by atomic layer deposition at 50 °C. Later the polymer core was removed by two different methods: dissolution and annealing. In the case of dissolution in water, the as-prepared TiO2 nanotubes remained amorphous, while when annealing was used to remove the polymers, the TiO2 crystallized in anatase form. Due to this, the properties of amorphous and crystalline TiO2 nanotubes with exactly the same structure and morphology could be compared. The samples were investigated by SEM-EDX, ATR-IR, UV-Vis, XRD and TG/DTA-MS. Finally, the photocatalytic properties of the TiO2 nanotubes were studied by decomposing methyl-orange dye under UV light. According to the results, crystalline anatase TiO2 nanotubes reached the photocatalytic performance of P25, while amorphous TiO2 nanotubes had observable photocatalytic activity.

Nanoscale TiO2 Protection Layer Enhances the Built-In Field and Charge Separation Performance of GaP Photoelectrodes.

Nanoscale oxide layer protected semiconductor photoelectrodes show enhanced stability and performance for solar fuels generation, although the mechanism for the performance enhancement remains unclear due to a lack of understanding of the microscopic interfacial field and its effects. Here, we directly probe the interfacial fields at p-GaP electrodes protected by n-TiO2 and its effect on charge carriers by transient reflectance spectroscopy. Increasing the TiO2 layer thickness from 0 to 35 nm increases the field in the GaP depletion region, enhancing the rate and efficiency of interfacial electron transfer from the GaP to TiO2 on the ps time scale as well as retarding interfacial recombination on the microsecond time scale. This study demonstrates a general method for providing a microscopic view of the photogenerated charge carrier's pathway and loss mechanisms from the bulk of the electrode to the long-lived separated charge at the interface that ultimately drives the photoelectrochemical reactions.

Preparation of core-shell C@TiO2 composite microspheres with wrinkled morphology and its microwave absorption

In this work, we successfully synthesize the core-shell structure carbon@titanium dioxide (C@TiO2) composite microspheres with wrinkled surface through a three-step method and build up the relationship between the TiO2 layer thickness and the microwave absorption property. The absorbing mechanism of the novel microsphere is revealed. Interface polymerization is applied for preparation of wrinkled poly glycidyl methacrylate/divinylbenzene polymer microspheres (PGMA/PDVB); Then, TiO2 layer is controllably coated on the surface of PGMA/PDVB microspheres by hydrolysis of tetrabutyl titanate (TBT); C@TiO2 composite microspheres are obtained by vacuum carbonization with PGMA/PDVB@TiO2 microspheres as the precursor. TiO2 layer thickness on the surface of C@TiO2 composite microspheres can be effectively adjusted by controlling the amount of TBT. When the amount of TBT is 0.75 mL, C@TiO2 composite microspheres exhibit the outstanding electromagnetic loss performance. The maximum reflection loss value (RLmax) reaches -49.21 dB at the thickness of 2 mm, corresponding effective absorption bandwidth is 5.27 GHz. The maximum effective absorption bandwidth is 5.5 GHz at 2.2 mm. The results show that the introduction of TiO2 can regulate electromagnetic parameters and enhance interface polarization ability. Meanwhile, the surface wrinkle structure offers more opportunities for multiple reflections of electromagnetic and introduces a large number of defective skeleton structure. The synergy of multiple advantages makes the absorbing performance of C@TiO2 composite microspheres significantly improved. This work plays a guiding role for the composition and the structure optimization of existing microwave absorbers.

Implication of color of sensitizing dyes on transparency and efficiency of transparent dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) are one of the potential candidates for the fabrication of colourful and see-through solar cells for energy harvesting esthetic windows. However, a trade-off between transparency and power conversion efficiency (PCE) has to be tackled amicably to realize the solar cells with good PCE and transparency. Judicious selection of dyes to bypass the light absorption in the high eye-sensitivity region (500–600 nm) is one of the plausible solutions. This was demonstrated utilizing yellow (D-131) and red (N-719) commercial dyes along with newly developed blue (SQ-138) and green coloured (SQ-140) dyes with intense and sharp light absorption mainly in the far-red to near-infrared (NIR) wavelength region. Transparent DSSCs fabricated using the most commonly used red-coloured dye N-719 although exhibited an increase in the PCE from 2.9% to 5.3% upon increasing the thickness of the transparent TiO2 layer from 4 μm to 10 μm but resulted in a serious loss in the average visible transparency (AVT) from 58.6% to 7.3% making the DSSC non-transparent. Contrary to this, under similar thickness variations, dyes D-131, SQ-138 and SQ-140 exhibiting very high AVT of >70% maintained the AVT > 40%, which is necessary for good visual perception.