Properties Of TiO2 Thin Films Research Articles

Electrochromic Properties of TiO2 Thin Films Deposited by Metal Organic Chemical Vapor Deposition and Sol-Gel Techniques

Electrochromic Properties of TiO2 Thin Films Deposited by Metal Organic Chemical Vapor Deposition and Sol-Gel Techniques

Comparison of photocatalytic properties of TiO2thin films and fibers

Efficiency of solar panels degrades as a result of organic contamination such as airborne particles, bird droppings and leaves. Any foreign object on photovoltaic panels reduces the sunlight entering the absorbing surface of the solar panels. Since this leads to a major problem decreasing in energy production, solar panels should be cleaned. The self-cleaning method can be preferred. There are some methods to clean the surface of solar panels. Among the self-cleaning materials, TiO2 is the most preferable ones because of its powerful photocatalytic properties. In this study, photocatalytic TiO2 were produced in two different nanostructures: nanofibers and thin films. TiO2 nanofibers were successfully produced by electrospinning. TiO2 thin films were fabricated by reactive magnetron sputtering technique. Both TiO2 nanofiber and thin film structures were heat-treated to form TiO2 in anatase phase at 600 °C for 2 h in air. Then, they were evaluated by SEM analyses for morphology, X-ray diffraction (XRD) analyses for phase structures, X-ray photoelectron spectroscopy (XPS) for the chemical state and atomic concentration, and UV-spectrometer for photocatalytic performance. The results indicate that photocatalytic and transmittance properties of TiO2 thin films are better than those of nanofibers. Consequently, TiO2 based thin films exhibit better performance for solar cell applications due to the surface cleanliness.

Properties of TiO2 thin films deposited by rf reactive magnetron sputtering on biased substrates

TiO2 thin films are of paramount importance due to their pervasive applications. In contrast to previous published works where the substrate was heated at high temperatures to obtain TiO2 crystalline phase, we show in this study that it is possible to deposit crystalline TiO2 thin films on biased and unbiased substrate at room temperature using reactive rf magnetron sputtering. The bias voltage was varied from 0V to −100V.The deposited films were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy, Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and atomic force microscopy (AFM). The average crystallite size was estimated using x-ray diffraction. The results showed that the application of negative bias affects the surface roughness of the films and favors the formation of the rutile phase. The root mean square roughness (Rrms), the average grain size and the optical band gap of the films decreased as the substrate bias voltage was varied from 0 to −100V. The UV–visible transmittance spectra showed that the films were transparent in the visible range and absorb strongly in the UV range. This study shows that biasing the substrate could be a promising and effective alternative to deposit TiO2 crystallized thin films of engineered properties at room temperature.

Effect of Sn and La doping on optical and hydrophilic properties of TiO2 thin film

Sn and La co-doped TiO2 thin films were fabricated on surface of glass slide substrates. Co-doped titania thin films were prepared by a sol gel method using, TBT as a precursor. Morphology and crystallite size of the obtained co-doped thin films changed by changing the content of La. Accordingly, the doped titania thin films showed various water contact angles and optical band gaps. As, the optical band gap of the nanostructured doped titania thin films decreased with increasing in content of La from 3.4 to 2.32 eV. Moreover, the water contact angles changed from 69.0° to 13.5° by changing the content of La.

Characterization and photoelectrochemical performance of Zn-doped TiO2 films by sol–gel method

Zn-doped TiO2 (Zn–TiO2) thin films were prepared by the sol–gel method on titanium substrates with heat treatment at different temperatures. The effects of heat treatment temperatures and Zn doping on the structure, photocathodic protection and photoelectrochemical properties of TiO2 thin films were investigated. It is indicated that the photoelectrical performance of the Zn–TiO2 films is enhanced with the addition of Zn element compared with the pure-TiO2 film and the largest decline by 897 mV in the electrode potential is achieved under 300 °C heat treatment. SEM–EDS analyses show that Zn element is unevenly distributed in Zn–TiO2 films; XRD patterns reveal that the grain size of Zn–TiO2 is smaller than that of pure-TiO2; FTIR results indicate that Zn—O bond forms on Zn–TiO2 surface. Ultraviolet visible absorption spectra prove that Zn–TiO2 shifts to visible light region. Mott–Shottky curves show that the flat-band potential of Zn–TiO2 is more negative and charge carrier density is bigger than that of pure-TiO2, implying that under the synergy of the width of the space-charge layer, carrier density and flat-band potential, Zn–TiO2 with 300 °C heat treatment displays the best photocathodic protection performance.

Comparison of structural, optical, photocatalytic behavior and hydrophilic properties of pure and Sn/La co-doped TiO2 thin films

In this study, a new method to enhance the hydrophilic properties of TiO2 thin films coated on the glass was developed by Sn and La co doped thin films. The effects of Sn (5–20 mol%) and La (5 mol%) co doped on the optical and hydrophilic were investigated. The optical, microstructure and hydrophilic properties of the thin film were studied using differential Uv–Vis spectroscopy, X-ray diffraction, scanning electron microscope and contact angle measurement. After 20 mol% Sn and 5 mol% La doped TiO2 thin film are superhydrophilic with water contact angle less than 19.2°. Also, the optical absorption spectrum indicates that the TiO2 have a direct band gap of 3.15 eV. But optical band gap of the doped TiO2 was found to be 3.0–1.8 eV.

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.

Influence of Nb content on the structural and optical properties of anatase TiO2 polycrystalline thin film by e-beam technique

In this paper, we report the structural and optical properties of Nb-doped TiO2 thin films deposited by e-beam evaporation technique. After post annealing in air at 500 °C for 1 h, the samples were characterized by various techniques such as X-ray diffraction (XRD), Raman spectroscopy, UV–Vis spectrophotometry and spectroscopic Ellipsometer. Both XRD and Raman analyses indicate that the films were crystallized into the polycrystalline anatase TiO2 structure. However it was observed that the crystallinity of the films decreases with the addition of Nb atoms and tends to become amorphous at 20% Nb content in TiO2 film. Moreover, no new phases such as Nb2O5, NbO2 or Nb metal were observed. The band gap energy was found to decrease with the increasing of Nb concentration which was verified by ellipsometric study. Ellipsomtric measurements also indicate that refractive index (n) of the films decreases while extinction coefficient (k) increases with the increasing of Nb content. All these analyses elucidate that the incorporation of Nb atom into TiO2 may tune the structural and optical properties of TiO2 thin films.

Enhanced structural, optical and super-hydrophilic properties of TiO2 thin film co-doped by V and Sn

The focus of this work is to study the effect of Sn doping and V doping on structural, surface morphological, optical and hydrophilic properties of TiO2 thin films. The pure and doped TiO2 thin films were prepared using a sol gel synthesis. The XRD studies reveal that the Sn and V doping decrease the crystalline size and formation both of anatase and rutile phases of TiO2 at 500 °C (Sn = 5 mol%, V = 15 mol%). Accordingly, the thin films showed various water contact angles and optical band gaps. As, the optical band gap of the nanostructured thin films decreased with various content of dopant from 3.38 to 2.33 eV. Moreover, the water contact angles changed from 69.0° to 0°.

자기세정을 위한 스퍼터링 TiO2박막의 산소 표면처리에 따른 특성

자기세정을 위한 스퍼터링 TiO₂박막의 산소 표면처리에 따른 특성

Influence of Substrate Surface Properties on Laser-induced Damage Properties of TiO2 Thin Films

Various investigations have focused on the laser-induced damage of thin films. However, substrate surface properties have not been taken into account. TiO2 thin films with a one-quarter wavelength optical thickness were deposited by electron beam evaporation on two types of substrates with different surface properties. The surface morphologies of TiO2 thinfilms were captured by atomic force microscopy, and the laser-induced damage threshold of TiO2 thin films was measured. The relationship between the substrate surface properties and the laser-induced damage properties of TiO2 thin films was observed and analyzed.

Dielectric relaxation and conduction mechanisms in sprayed TiO2 thin films as a function of the annealing temperature

The electrical properties of TiO2 thin films deposited by chemical spray pyrolysis onto Si substrates were investigated in the metal–oxide–semiconductor (MOS) configuration using current–voltage characteristics and impedance spectroscopy. The electrical properties were analyzed in relation to the changes in microstructure induced during annealing in air up to a temperature of 950 °C. Anatase to rutile transformation started after annealing at 800 °C, and at 950 °C, only the rutile phase was present. The dielectric relaxation strongly depended upon the microstructure of TiO2 with the dielectric constant for the anatase phase between 45 and 50 and that for the rutile phase 123. Leakage current was reduced by three orders of magnitude after annealing at 700 °C due to the densification of the TiO2 film. A double-logarithmic plot of the current–voltage characteristics showed a linear relationship below 0.12 V consistent with Ohmic conduction, while space-charge-limited conduction mechanism as described by Child’s law dominated for bias voltages above 0.12 V.

EFFECT OF DEPOSITION TEMPERATURE ON THE PROPERTIES OF TIO2 THIN FILMS DEPOSITED BY MOCVD

Crystal structure, microstructure, and optical properties of TiO2 thin films deposited on quartz substrates by metal-organic chemical vapor deposition (MOCVD) in the temperature range from 250[Formula: see text]C to 450[Formula: see text]C have been studied. The crystal structure, thickness, microstructure, and optical properties have been carried out using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), atomic force microscope (AFM), and UV-visible transmittance spectroscopy, respectively. XRD patterns show that the obtained films are pure anatase. Simultaneously, the crystal size calculated using XRD peaks, and the grain size measured by AFM decrease with the increase in deposition temperature. Moreover, the texture of the films change and roughness decrease with the increase in deposition temperature. The spectrophotometric transmittance spectra have been used to calculate the refractive index, extinction coefficient, dielectric constant, optical energy gap, and porosity of the deposited films. While the refractive index and dielectric constant decrease with the increase of deposition temperature, the porosity shows the opposite.

Investigations on the Synthesis, Optical and Electrical Properties of TiO2 Thin Films by Chemical Bath Deposition (CBD) method

Titanium dioxide (TiO2) thin films were prepared by Chemical Bath Deposition (CBD) method. The X-ray diffraction (XRD) analysis was used to examine the structure and to determine the crystallite size of TiO2 thin film. The surface morphology of the film was studied using Scanning Electron Microscopy (SEM).The optical properties were studied using the UV-Visible and photoluminescence (PL) spectrum. Optical constants such as band gap, refractive index, extinction coefficient and electric susceptibility were determined. The FT-IR spectrum revealed the strong presence of TiO2. The dielectric properties of TiO2 thin films were studied for different frequencies and different temperatures. The AC electrical conductivity test revealed that the conduction depended both on the frequency and the temperature. Photoconductivity study was carried out in order to ascertain the positive photoconductivity of the TiO2 thin films.

Structural, morphological and optical properties of TiO2:Mn thin films prepared by spray pyrolysis technique

Mn-doped TiO2 thin films were deposited on glass substrates by spray pyrolysis technique at different manganese doping concentrations $$\left( {y = \frac{{\left[ {Mn^{2 + } } \right]}}{{\left[ {Ti^{4 + } } \right]}} = 0, 2, 4, 6\, and\,10\;\% } \right)$$ . X-ray diffraction (XRD), atomic force microscopy, scanning electron microscopy, spectrophotometry and spectrofluorimetry techniques were used in order to study the effect of Mn doping on the structural, morphological and optical properties of TiO2 thin films. It is found that better film crystallinity was obtained for Mn doping ratio of about 2 at%. Morphological studies revealed that the grown layers exhibited uniform and compact surfaces. An indirect band gap of about 3.44 eV was obtained according to the optical studies. Film thickness, refractive index and extinction coefficient were determined using envelope method. Both Wemple–Di Domenico single oscillator and Spitzer–Fan models were used to study the effect of manganese doping on some optical constants. All photoluminescence spectra showed several emissions in both UV and visible regions.

Overview of Superhydrophilic, Photocatalytic and Anticorrosive Properties of TiO2 Thin Films Doped with Multi-walled Carbon Nanotubes and Deposited on 316L Stainless Steel

TiO2 films with MWCNTs are produced for anticorrosive applications to increase the lifetime of steel materials. TiO2 has two additional properties, photoactivity and superhydrophilicity. Two TiO2 samples, synthesized in aqueous or alcoholic media, have been doped with MWCNTs. The material which best combines anticorrosive, superhydrophilic and photocatalytic properties, is the one produced in aqueous medium (Aq-TiO2-CNT). Doping with MWCNTs increases the photodegradation of p-nitrophenol from 18% to 50%. MWCNTs allow to reduce the corrosion current and the corrosion potential. The good superhydrophilicity of TiO2 is kept on stainless steel with a contact angle after illumination around 5°.

Microstructure, Optical and Photocatalytic Properties of TiO₂ Thin Films Prepared by Chelating-Agent Assisted Sol-Gel Method.

Single and multilayer TiO₂ thin films coated on two types of soda-lime glass substrates (microscope slides and cylinders) were prepared by a chelating agent-assisted sol-gel method, using ethyl acetoacetate as a chelating agent, dip-coating and calcination at 500 °C for 2 h in air. Phase composition, microstructural, morphological and optical properties of thin films were comprehensively investigated by using XRF, advanced XRD analysis, Raman and UV-vis spectroscopy and AFM. It was found out that the thickness of thin films increases linearly with increasing number of deposited layers, indicating a good adhesion of the titania solution to a glass substrate as well as to a previously calcined layer. 1 layer film crystallized to anatase-TiO₂(B) mixture with minor/negligible amount of nanosized brookite, 2-4 layers films crystallized to anatase-brookite-TiO₂(B) mixture. In contrast to other multilayers films, 4 layers film was highly inhomogeneous. The different phase composition of thin films was clarified based on the crystallization via titanate/s and metastable monoclinic TiO₂(B) as a consequence of several phenomena; the diffusion of Na⁺ ions from a soda-lime glass substrate, acidic conditions and repeated thermal treatment. The multilayer films were in average highly transparent (80-95%) in the visible light region with the sharp absorption edge in the UV light region. Additionally, the photocatalytic properties of selected multilayer films were compared in AO7 photodegradation. Photocatalytic experiments showed that thicker 4 layers film of tricrystalline anatase-brookite-TiO₂(B) phase mixture was similarly active as thinner 3 layers film of similar phase composition, which may be a consequence of the inhomogeneity of the thicker film.

Influence of Pore Size on the Optical and Electrical Properties of Screen PrintedTiO2Thin Films

Influence of pore size on the optical and electrical properties of TiO2thin films was studied. TiO2thin films with different weight percentages (wt%) of carbon black were deposited by screen printing method on fluorine doped tin oxide (FTO) coated on glass substrate. Carbon black decomposed on annealing and artificial pores were created in the films. All the films were 3.2 µm thick as measured by a surface profiler. UV-VIS-NIR spectrophotometer was used to study transmittance and reflectance spectra of the films in the photon wavelength of 300–900 nm while absorbance was studied in the range of 350–900 nm. Band gaps and refractive index of the films were studied using the spectra. Reflectance, absorbance, and refractive index were found to increase with concentrations of carbon black. There was no significant variation in band gaps of films with change in carbon black concentrations. Transmittance reduced as the concentration of carbon black in TiO2increased (i.e., increase in pore size). Currents and voltages (I-V) characteristics of the films were measured by a 4-point probe. Resistivity (ρ) and conductivity (σ) of the films were computed from theI-Vvalues. It was observed that resistivity increased with carbon black concentrations while conductivity decreased as the pore size of the films increased.

Alteration of titanium dioxide material properties by glancing angle deposition plus annealing treatment

Titanium dioxide (TiO2) nanostructured thin film (TNF), as an important semiconductor exhibiting large surface-to-volume ratio and unique property, has attracted more and more researches. As an important versatile nanofabrication technique, the glancing angle deposition technique (GLAD) is used to fabricate the TNF, frequently. However, little is known about the influence of GLAD on microstructure, crystalline structure, Ti/O chemical state and photoluminescence (PL) properties of TiO2 thin films. In this paper, pure anatase TNF and traditional TiO2 thin film (TTF) were deposited by combining GLAD system with the annealing treatment. All of the prepared TNFs keep discrete nanoscale columnar structures characterized by SEM. The evolution of morphology, crystallization structure, Ti/O chemical state and PL properties of TNFs and TTFs under annealing treatment have been investigated in detail. Simultaneously, comparing with TTFs, the influence of GLAD on TNFs material properties has been analyzed further. With the optimum annealing temperature (400 °C), one can obtain fine nanostructures and pure anatase precipitation of TNFs. The GLAD technique can adjust the preferred crystal orientation of TiO2 thin films, which can be used as a method of material structural design. Both TNFs and TTFs exhibit broad band (380–700 nm) photoluminescence. Nevertheless, the TNFs exhibit much weaker and smoother PL spectra than that of TTFs, due to the large surface-to-volume ratio. The results indicate the potential good catalytic applications of TNFs deposited by GLAD.

Effects of Continuous and Discontinuous Deposition Time in Reactive Direct Current Magnetron Sputtering of Titanium Dioxide Thin Films

The effect of continuous and discontinuous deposition time on the properties of TiO2 thin films deposited by reactive direct current magnetron sputtering (DCMS) on glass substrates was investigated. The deposition processes were designed for a condition of continuous deposition time D1 (60 min) and three conditions of discontinuous deposition time D2 (30 min × 2 times), D3 (15 min × 4 times), and D4 (1 min × 60 times). The crystal structure, surface morphology, and hydrophilicity of TiO2 thin films were characterized by X-ray diffraction, atomic force microscope, and water contact angle method, respectively. It was found that the increasing of discontinuous deposition time (conditions from D1 to D4) shows the changing of grain size from big grain size with spherical shape to small grain size with oval shape. The crystallinity of TiO2 films decrease with increasing the discontinuous deposition time. The water contact angles also decrease as a function of increasing discontinuous deposition time. These results may be explained from the accumulation of heat on the substrate which affected the phase composition and surface morphology of TiO2 thin films.