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Abstract Substoichiometric TiO 2 films have been prepared by reactive magnetron sputtering. Employing an oxygen feedback loop has enabled a precise control of the sub-stoichiometry in the growing TiO 2-x film as well as a high level of sample reproducibility. TiO 2-x was deposited on unheated substrates and subsequently annealed at 300 °C. These films have been characterized by a variety of techniques to unravel the interplay between stoichiometry and optical as well as electronic properties. Capping the films by a Si 3 N 4 layer was sufficient to prepare films with resistivities as low as 8 mΩcm showing a high mobility of up to 15 cm2/Vs. At the same time, a high transparency above 80% could be realized for these samples. The results verify that metal-like conductivity and high transparency can be realized simultaneously in undoped TiO 2-x. Upon variation of the film stoichiometry a metal-insulator transition has been observed in temperature dependent electrical measurements performed down to 2 K. Highlights • High conductivity and transparency in undoped TiO2 films was achieved. • Annealing the reactively sputtered films at 300 °C in Ar-atmosphere was sufficient. • Influence of oxygen content of the slight sub-stoichiometric films was investigated. • Temperature dependent Hall measurements prove metal-like transport. • Important differences in comparison to conventional TCOs are shown and explained. [ABSTRACT FROM AUTHOR]

Titanium dioxide thin films have been deposited on glass substrate at various solution flow rates by spray pyrolysis technique with substrate temperatures between 350 °C–550 °C. Samples were characterized for structural, morphological and optical properties by X-ray diffraction (XRD), scanning electron microscope (SEM) and UV–visible spectrometry. The XRD analysis of deposited TiO 2 films exhibited nanocrystalline nature and preferentially oriented along [101] direction. The UV–visible transmittance results show that all thin films were transparent with an average transmittance higher than 70% in the visible region. Due to nanosized grains, the optical band gaps of the TiO 2 thin films (3.35–3.68 eV) were larger than the bulk TiO 2 (3.2 eV). The SEM analysis revealed that thickness and morphology of TiO 2 films can be adjusted by rate of solution flow and substrate temperature. It seems that the process of spray pyrolysis provides an easy way to prepare either homogeneous thin and thick films. [ABSTRACT FROM AUTHOR]

In this study, Al-doped TiO 2 films are deposited by sol-gel dip-coating method. Structure, surface morphology, optical properties and photocatalytic degradation of Methylene blue have been investigated. The films are characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), UV–Visible spectroscopy and scanning electron microscope (SEM) equipped with electron dispersive X-ray (EDX). XRD analysis confirms the formation of single nanocrystalline anatase phase. The crystallite size is in the order of 17 nm and seems not affected by the presence of Al. AFM analysis reveals that the surface topography of TiO 2 :Al films is significantly affected by Al content. The optical properties are found not affected and all TiO 2 :Al thin films show high visible infrared transmission and high optical gap energy. The phocatalytic efficiency has been improved by Al doping; with the highest degradation rate of methylene blue observed for TiO 2 :0.2% Al. [ABSTRACT FROM AUTHOR]

The polymer/nanoparticle interface of polyaniline (PANI)/TiO 2 composite was characterized by using Fourier transform infra-red spectrometer imaging system, Raman (both coupled with optical microscope) and UV–vis spectroscopy. During characterization, as white light from the optical microscope impinges on TiO 2 , it absorbs supra band-gap photons and electron-hole pairs are produced. On accepting the holes, PANI gets oxidized from emeraldine salt form to its next oxidation state that is pernigraniline salt form, leading to a change in color. In optical micrographs this change in color appears as a halo around each TiO 2 particle and defines the extent of the oxidized area of PANI, which helps to characterize the extent of oxidation of PANI at the interface of PANI/TiO 2 . Further studies revealed that the range and extent of oxidation at the interface in polymer depend on the types of dispersions of TiO 2 nanoparticles in PANI matrix. [ABSTRACT FROM AUTHOR]

Niobium-doped TiO 2 films as highly transparent conducting oxides for electrical contacts were investigated. As-deposited films were amorphous and exhibited high resistivities ranging from 10 to 10 5 Ω cm. A slight oxygen deficiency in as-deposited films was essential to gain low resistivities (10 − 3 Ω cm) and low optical absorption coefficients ( α 550 nm < 2 × 10 3 cm − 1 ) in the annealed films. Therefore, we controlled the oxygen stoichiometry during the film deposition by adjusting the magnetron discharge voltage, while the oxygen gas flow was kept constant. The Hall mobility of degenerately doped films (electron concentration > 10 20 cm − 3 ) increased with decreasing substrate temperature owing to metal-like phonon scattering in these samples. [ABSTRACT FROM AUTHOR]

Recently, fabrication of the nanoporous TiO 2 photoelectrode on metal foils by means of sputtering of the Ti film on preheated metal substrate followed by the TiO 2 deposition (doctor blade technique) and sintering represents the frequently applied technique. This is despite the relatively complicated procedure and number of parameters to be controlled in order to fabricate films of required properties. In this work an approach is applied and discussed in which the nanoporous TiO 2 electrode is fabricated under conditions similar to pulsed laser deposition but with the deposit formed directly on the ablated target at atmospheric pressure and room temperature. The titanium dioxide thin film is grown by ablation of the Ti foil with the nanosecond UV laser (266 nm) at fluence up to 1.5 J/cm 2 . The rutile–anatase phase transformation takes place during this one-step process and no thermal pre-and post-treatment of the deposit is needed. In samples produced in air, the presence of mixed phases of the non-stoichiometric anatase (> 70%), rutile and negligible amount of TiN is consistently confirmed by the X-ray diffraction, energy-dispersive X-ray and Raman spectra. For applications of the reported films as electrode material in the third generation photovoltaic cells, the use of industrial lasers could significantly improve the process efficiency. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) based on one-dimensional anatase TiO 2 nanotube arrays were prepared by using a two-step deposition method to fill the arrays of TiO 2 nanotubes in different lengths with perovskite. The photovoltaic performance of PSCs was found to be significantly dependent on the length of the TiO 2 nanotubes, and the power conversion efficiency decreased as the length of the TiO 2 nanotubes increased from ~ 0.40 μm to ~ 0.65 and then to ~ 0.93 μm. The PSC fabricated with ~ 0.40 μm-long anatase TiO 2 nanotube arrays yielded a power conversion efficiency of 11.3% and a fill factor of 0.68 under illumination of 100 mW/cm 2 AM 1.5G simulated sunlight, which is significantly higher than previously reported solar cells based on 1-D TiO 2 nanostructures. Incident photon-to-current efficiency and electrochemical impedance spectroscopy measurements indicated that longer TiO 2 nanotubes led to higher recombination losses of charge carriers, possibly due to poor filling of the nanotube arrays with perovskite. [ABSTRACT FROM AUTHOR]

Titania aerogels were synthesized by sol–gel route followed by ambient pressure subcritical drying technique. The aerogels synthesized in the present work possess a maximum surface area of 252 m 2 /g. The pore size distribution is between 2 and 30 nm which confirms their mesoporosity. The oxygen plasma treatment on titania aerogel thin films improved the surface area up to 273 m 2 /g and produced additional hydrophilic groups on the surface. It is confirmed by BET surface area, XPS and thermal analysis in conjunction with dye adsorption studies. After plasma treatment the dye adsorption capacity was increased 2.5 times higher than that of untreated aerogel film. The increased surface area and the hydrophilic groups generated on the titania aerogel surface during plasma treatment are responsible for enhanced dye adsorption. The overall nanoporous morphology of titania aerogel is preserved after plasma treatment. [ABSTRACT FROM AUTHOR]

A hybrid layer system consisting of anatase, an N-substituted dithienylated phenothiazine (DTPT) with a carboxylic anchor group as molecular donor–π–acceptor-system and poly(3-hexylthiophene) as hole transporting material is studied by means of X-ray and UV-photoelectron spectroscopy and UV/vis spectroscopy. The optoelectronic properties of the DTPT and the energy level alignment at the interface DTPT/TiO 2 enable the design of an UV-responsive hybrid solar cell, which is conceptually presented. [ABSTRACT FROM AUTHOR]

A PECVD (Plasma-enhanced Chemical Vapor Deposition) process operating at 150 °C has been implemented to prepare micro-columnar porous TiO 2 anatase thin films, performing post-annealing at 300 °C for 5 h. Optimized PECVD conditions have enabled us to obtain homogeneous films with thickness equal to 1–2 μm ± 0.2 μm. An anatase seeding interface deposited prior to the PECVD process has enabled us to reduce crystallization time down to 1.5 h. The size of nano-crystals in prepared anatase thin films has been estimated to be 20 nm by applying the Scherrer equation. Besides, the band-gap energy ( E g ) of synthesized anatase thin films on quartz was found to be 3.30 eV. [ABSTRACT FROM AUTHOR]

The light-trapping TiO 2 electrode is proposed and prepared originally by employing the high-refractive-index rutile TiO 2 microspheres sandwiched between two layers of the low-refractive-index anatase TiO 2 nanoparticles. Owing to its excellent light-trapping property, the dye-sensitized solar cells based on this electrode exhibit a total efficiency of 10.05%, which is 18% higher than that of traditional dye-sensitized solar cells based on high-index rutile TiO 2 as a top reflecting layer. This TiO 2 electrode with symmetrical structure is a promising candidate for applications in the TiO 2 based photoelectric device. [ABSTRACT FROM AUTHOR]

A technique to deposit Nb-doped films of TiO 2 by radio-frequency magnetron sputtering was investigated. Nb wires are put onto the sputter track of a metallic titanium target and the oxidation state of the target is controlled by the intensity of a Ti line from the plasma emission. The sputtered films are analyzed with X-ray diffraction, RBS (Rutherford back scattering), energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and SEM (scanning electron microscopy). After post-heating at 400 °C, all films exhibit the anatase structure. The films are polycrystalline with a Nb/[Nb + Ti] content from 2 to 17 at.%. RBS and SEM indicate that the films consist of two sub-layers with the surface layer containing more Nb and exhibiting a clearer columnar structure. There is an optimum oxidation state of the target in the transition region between metallic and oxidic modes where the lowest resistivity of 7 × 10 − 4 Ωcm is achieved. Nb is incorporated as Nb 5 + into the anatase lattice, but in suboptimal films, Ti vacancies (acceptors) may compensate the donor effect of Nb. The oxygen content in the films is higher than for stoichiometric TiO 2 . O interstitials may increase the mass density of the films. The lattice parameter a and the unit cell volume increase with the Nb content in a similar manner as observed for single crystals of TiO 2 :Nb. [ABSTRACT FROM AUTHOR]

Epitaxial rutile-TiO2(011) and anatase-TiO2(001) films have been grown by pulsed laser deposition on Al2O3(1-102) and LaAlO3(100), respectively. For low growth rates of ~0.0012nm/s and growth temperatures of 600°C high quality films are obtained. In particular the anatase films exhibit 100nm wide flat terraces for 10-15nm film thickness. Atomic steps of both ~0.25 and ~0.5nm are measured, suggesting the existence of two different terminations, although only a 4 x 1 reconstruction is observed in reflection high-energy electron diffraction. The rutile films exhibit coherent twin domain boundaries, which is likely the reason for smaller terrace sizes compared to anatase films. Photocatalytic activity of the films is measured by decomposition of methyl orange solution under UV-irradiation. The anatase films are about twice as active as the rutile films. For both films the activity does not change significantly for films of 10nm and thicker. For rutile films the activity is also compared to that of single crystal rutile TiO2(011) samples. Both rutile-films and single crystals exhibit very similar activity, indicating the good quality of the films. Post-growth annealing of the films in air at 600°C decreases the photocatalytic activity of the films. On the other hand, reduction of thin films by vacuum annealing to 800°C does not change the photocatalytic activity of the films significantly compared to the as grown films. This is in contrast to single crystal rutile samples whose photocatalytic activity for the decomposition of methyl orange almost doubles after reduction by high-temperature annealing in vacuum compared to the stoichiometric bulk-samples. The differences between films and bulk samples may hint differences in defect formation due to the substrate interface. [ABSTRACT FROM AUTHOR]

Thin films of TiO2 were deposited by reactive sputtering of a Ti target on unheated substrates and post-heated at 300°C and 500°C. They exhibit a granular structure. Direct current-sputtered films are amorphous as-deposited and crystallize (to pure anatase) only at 500°C. Radio-frequency (rf)-sputtered films are already crystalline (pure anatase) as-deposited on unheated substrates. Above a thickness of 100nm, the crystallite size, as deduced from the half-width of X-ray diffraction (XRD) peaks, is constant at 35nm and decreases to zero when the thickness decreases to 25nm. Below a thickness of 25nm, the films are X-ray amorphous. Height and half-width of the XRD peaks of rf-sputtered films do not change upon post-heating at 300 or 500°C. A larger lattice parameter ratio c/a is observed with respect to the bulk value that decreases with increasing film thickness and is about 1% larger for a film thickness larger than 100nm. [ABSTRACT FROM AUTHOR]

Abstract: The goal of this study was to investigate the formation of titanium dioxide nanotubes on the surface of cast Ti–30Nb–xTa alloys by anodizing. The anodization technique for creating the nanotubes utilized a potentiostat and an electrolyte containing 1M H3PO4 with 0.8wt.% NaF. The grain size of the Ti–30Nb–xTa alloys increased as the Ta content increased. Using X-ray diffraction, for the Ti–30Nb alloy the main peaks were identified as α″ martensite with strong peaks of β phase. The phases in the Ti–30Nb–xTa alloys changed from a duplex (α″+β) microstructure to solely β phase with increasing Ta content. The nanotubes that formed on the surface of the Ti–30Nb–xTa alloys were amorphous TiO2 without an evidence of the crystalline anatase or rutile forms of TiO2. Scanning electron microscopy revealed that the average diameters of the small and large nanotubes on the Ti–30Nb alloy not containing Ta were approximately 100nm and 400nm, respectively, whereas the small and large nanotubes on the alloy had diameters of approximately 85nm and 300nm, respectively. As the Ta content increased from 0 to 15wt.%, the average lengths of the nanotubes increased from 2μm to 3.5μm. Energy-dispersive X-ray spectroscopy indicated that the nanotubes were principally composed of Ti, Nb, Ta, O and F. Contact angle measurements showed that the nanotube surface had good wettability by water droplets. [Copyright &y& Elsevier]

Abstract: Hydrophilic and solar-heat-reflective coatings were deposited on glass substrates by radio-frequency sputtering. This bifunctional coating was a multilayer film consisting of SiO2, TiO2, and a heat-resistant silver alloy, which was used instead of pure silver. The multilayer film was used to improve the spectral reflection and spectral transmission properties. The heat-resistant silver alloy developed in this study facilitated the formation of an anatase layer on the surface of the coating at elevated temperatures. The photocatalytic anatase layer made the surface hydrophilic. The hydrophilic and optical properties of samples prepared at various temperatures were determined. Under ultraviolet irradiation, the water contact angle decreased from around 60° to 6° for a sample with an anatase surface layer. The sample glass reflected most of the infrared light and simultaneously transmitted visible light. [Copyright &y& Elsevier]

Abstract: Epitaxial anatase titanium dioxide (TiO2) films have been grown by atomic layer deposition (ALD) on Si(001) substrates using a strontium titanate (STO) buffer layer grown by molecular beam epitaxy (MBE) to serve as a surface template. The growth of TiO2 was achieved using titanium isopropoxide and water as the co-reactants at a substrate temperature of 225–250°C. To preserve the quality of the MBE-grown STO, the samples were transferred in-situ from the MBE chamber to the ALD chamber. After ALD growth, the samples were annealed in-situ at 600°C in vacuum (10−7 Pa) for 1–2h. Reflection high-energy electron diffraction was performed during the MBE growth of STO on Si(001), as well as after deposition of TiO2 by ALD. The ALD films were shown to be highly ordered with the substrate. At least four unit cells of STO must be present to create a stable template on the Si(001) substrate for epitaxial anatase TiO2 growth. X-ray diffraction revealed that the TiO2 films were anatase with only the (004) reflection present at 2θ =38.2°, indicating that the c-axis is slightly reduced from that of anatase powder (2θ =37.9°). Anatase TiO2 films up to 100nm thick have been grown that remain highly ordered in the (001) direction on STO-buffered Si(001) substrates. [Copyright &y& Elsevier]

Abstract: The effects of crystallinity, phase and oxygen vacancies on optical and photocatalytic properties of titania (TiO2) thin films were systematically studied. The as-deposited amorphous titania films were prepared by reactive sputtering titanium metal targets in argon–oxygen plasma at 100°C and subsequently annealed at various temperatures of 400–800°C in air, vacuum and H2 atmosphere. The results indicate that in general the crystallinity of the annealed films is enhanced with the increasing annealing temperature. At the same temperature, the H2 annealed films achieve better crystallinity but containing more oxygen vacancies than the films annealed in air and in vacuum. In H2 or in vacuum, the concentration of oxygen vacancies in the annealed films increases with increasing temperature, while in air it remains constant. Oxygen vacancies in titania film not only facilitate phase transformation but also lower the band gap of titania, and make the film visible-light responsive. Photocatalytic properties of the TiO2 films were characterized in UV and visible light irradiation by following the Ag reduction and degradation of methylene blue. The films annealed at 600–700°C in H2 possess the best film crystallinity and the proper concentration of oxygen vacancies and exhibit the best photocatalytic performance under both UV and visible light. [Copyright &y& Elsevier]

Abstract: Anatase (TiO2) thin films were grown by non-aqueous sol-gel dip-coating using titanium (IV) n-butoxide as precursor and 1-butanol as solvent. High withdrawal speed of 4.7mm/s in dip-coating resulted in defect free films of 100nm average film thickness after subsequent heat treatments. According to scanning electron microscope and X-ray diffraction measurements, the films consisted of nanocrystalline anatase with 30nm mean crystallite size. Refractive index n(λ) and extinction coefficient k(λ) were determined over the wavelength range from 200 to 1650nm. The optical band gap of the film material was approximately 3.2eV. The results showed very similar optical characteristics to those that are accomplished with chemically more reactive aqueous sol-gel processes. Furthermore, it was found that in addition to porosity, coordination number of Ti atoms to nearest oxygen neighbors is likely to have a significant role in explaining differences of optical properties between bulk anatase and thin film materials of the present work. [Copyright &y& Elsevier]

Abstract: This study presents the fabrication method and the dielectric property of polymer matrix composite films of carbon nanotube (CNT) coated with TiO2. The TiO2 was coated with sol–gel method using titanium (IV) butoxide (TNBT), HO2 and benzyl-alcohol as the surfactant. The configuration of CNT-TiO2 hybrid was observed with the field emission scanning electron microscope images. The coated TiO2 was thermally treated and transformed into the anatase structure to enhance the mechanical strength and get the high insulating property. The anatase structure was proved from the diffraction angles of XRD. The CNT-TiO2 hybrid was mixed with the epoxy resin using 3-roll-mil and casted into the films using film casting method. The structure of CNT-TiO2 hybrid was ascertained to be maintained against the high shear stress during the mixing and casting processes. The dielectric property of the composite films was measured following IPC-TM-6550. The dielectric property at 1GHz of the composite film of 5wt.% CNT is about 10 and the loss tangent at 1GHz is about 0.06. [Copyright &y& Elsevier]

Abstract: Nanocrystalline anatase (TiO2) thin films prepared by a physical vapour deposition method were nitrided by annealing in flowing NH3 at temperatures ranging between 650°C and 700°C. It was established that there was a narrow window of temperatures which allowed both incorporation of interstitial nitrogen into the films with retention of the anatase phase without chemical reduction and preservation of the characteristic nanocrystalline morphology. These optimally modified films responded to visible light in photowetting tests and showed the ability to degrade an organic dye under visible light irradiation. [Copyright &y& Elsevier]

Abstract: The fabrication of dense or porous titania films by the sol–gel method using anatase colloidal solutions was examined. When anatase colloidal solutions without surfactants were deposited on a substrate, the anatase films thus obtained had a relatively high refractive index (~2.0). Porous films were fabricated using the anatase colloidal solutions with surfactants. Some films had phase separation structures on the submicron scale, such as spinodal decomposition, which consisted of anatase nanocrystal agglomerate regions and surfactant regions. When the dispersion of the anatase colloids was improved, mesoporous films could also be fabricated, although mesopores were irregular in size, shape, and arrangement. [Copyright &y& Elsevier]

Abstract: In direct contrast to the way in which silicon is precisely doped for integrated circuit applications in order to optimize device performance, there is little nuanced understanding of the correlation between TiO2 doping level, charge carrier concentration, and the operation of TiO2-based photocatalysts, dye-sensitized solar cells, and sensors. The present work outlines a rigorous methodology for the determination of free carrier concentration for doped metal oxide semiconductors such as TiO2 that are not amenable to standard metrology methods. Undoped, Cr-, Mn-, and Nb-doped polycrystalline anatase TiO2 are synthesized via atomic layer deposition (ALD) using Ti(OCH(CH3)2)4, H2O, Cr(C5H7O2)3, Mn(DPM)3 (DPM = 2,2,6,6-tetramethyl-3, 5-heptanedionato), and Nb(OCH2CH3)5 as the source materials for Ti, O, Cr, Mn, and Nb, respectively. Chemical composition and crystallinity are investigated and a thorough “device-like” characterization of TiO2 Schottky diodes is carried out to justify the subsequent extraction of carrier concentration values from capacitance–voltage (C–V) measurements using the Mott–Schottky approach. The influence of factors such as substrate type, contact metal type, and surface and interface preparation are examined. Measurements of donor carrier concentration are obtained for undoped, Cr-, Mn-, and Nb-doped TiO2 synthesized by ALD. Possible causes for the obtained carrier concentrations are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Sculptured porous titania films as photoanode in dye-sensitized solar cell (DSSC) were prepared using an electron-beam evaporation system with glancing angle deposition (GLAD) method. By controlling the substrate rotation rate and the incident angle of evaporant, titania films of various thicknesses were prepared on ITO glasses. The as-deposited nano-porous films are comprised of helical nano-columns and assembled in an orderly manner with gaps or pores in between, which offer large internal surface area for dye adsorption and direct electron transfer path. There is a positive correlation between the film thickness, film effective surface area, amount of absorbed dye and cell efficiency. The nano-porous films provide a synergistic effect of high surface area, effective route for electron transfer, tight interfaces, and enhanced light trapping, which are all beneficial for higher cell efficiency. The DSSC consisting of a 6μm titania film, deposited at substrate rotating rate 0.17rpm and incident angle 73°, gave a cell efficiency of 6.1%. [ABSTRACT FROM AUTHOR]

Abstract: We have studied the structural and optical properties of thin films of TiO2, doped with 5% ZrO2 and deposited on glass substrate (by the sol–gel method). The dip-coated thin films have been examined at different annealing temperatures (350 to 450°C) and for various layer thicknesses (63–286nm). Refractive index and porosity were calculated from the measured transmittance spectrum. The values of the index of refraction are in the range of 1.62–2.29 and the porosity is in the range of 0.21–0.70. The coefficient of transmission varies from 50 to 90%. In the case of the powder of TiO2, doped with 5% ZrO2, and aged for 3months in ambient temperature, we have noticed the formation of the anatase phase (tetragonal structure with 14.8nm grains). However, the undoped TiO2 exhibits an amorphous phase. After heat treatments of thin films, titanium oxide starts to crystallize at the annealing temperature 350°C. The obtained structures are anatase and brookite. The calculated grain size, depending on the annealing temperature and the layer thickness, is in the range (8.58–20.56nm). [ABSTRACT FROM AUTHOR]

Abstract: Self-limiting deposition of titanium dioxide thin films was accomplished using pulsed plasma-enhanced chemical vapor deposition (PECVD) and plasma-enhanced atomic layer deposition (PEALD) at low temperatures (T <200°C) using TiCl4 and O2. TiCl4 is shown to be inert with molecular oxygen at process conditions, making it a suitable precursor for these processes. The deposition kinetics were examined as a function of TiCl4 exposure and substrate temperature. The quality of the anatase films produced by the two techniques was nominally identical. The key distinctions are found in precursor utilization and conformality. Pulsed PECVD requires 20 times less TiCl4, while PEALD must be used to uniformly coat complex topographies. [ABSTRACT FROM AUTHOR]

Abstract: Transparent conducting Nb-doped anatase TiO2 (TNO) epitaxial films were sputtered from TiO2-, Ti2O3-, and Ti-based targets at various oxygen partial pressures (Po2). Using the TiO2- and Ti2O3-based targets, highly conductive films showing a resistivity (ρ) of ~3×10−4 Ωcm could be formed without postdeposition treatment. In the case of the TNO films formed from the Ti-based target, reductive annealing had to be carried out at a temperature of 600°C to achieve similar resistivity values. Thus, the use of oxide targets is preferable to obtain as-grown transparent conducting TNO films. In particular, the Ti2O3-based target is practically advantageous, because it offers a wide range of optimal Po2 values at which ρ values of the order of 10−4 Ωcm are achievable. [Copyright &y& Elsevier]

Abstract: A series of sculptured porous nano-columnar titanium oxide films were prepared by glancing angle deposition (GLAD) method using an electron-beam evaporation system. The films were deposited on ITO glasses at various incident angles from 53° to 86°and used as photoanode in a dye-sensitized solar cell (DSSC). The as-deposited TiO2 films are comprised of helical nano-columns and assembled in an orderly manner with gaps or pores in between. The porous nanostructured films provide a synergetic effect of high surface area, effective route for electron transfer, tight interfaces, and enhanced light trapping, which are all beneficial for higher cell efficiency. The DSSCs incorporated with the GLAD films of 4μm thick exhibited a high fill factor (FF) up to 0.77. The TiO2 film deposited at an incident angle of 73° provides the largest internal surface area and the largest amount of dye absorption and results in the highest light conversion efficiency of 2.78%. [Copyright &y& Elsevier]

Abstract: Titanium oxides have anti-inflammatory activity and tunable electrochemical properties that make them attractive materials for biomedical applications. This work investigated the compatibility of nanometric coatings of low-temperature phases of TiO2 with neurons in 4-day and 10-day cultures, using different cell densities to quantify cell survival and neurite extension. TiO2 films were prepared by sol–gel and thermal treatment (250–450 °C) of hydrolyzed titanium tetra-isopropoxide on electrically conducting or insulating slides. The conducting substrates were not passivated by the nanometric oxide layer and could be used as electrodes. Characterization of the films showed nano-structured TiO2 containing exclusively Ti+4 valence in anatase and amorphous phases. When coated with polylysine, all films permitted good neuron attachment and survival for at least ten days in culture. However, they generally reduced neurite growth compared to cell culture borosilicate glass, with dendrites more affected than axons. The analyses of surface topography, hydrophilicity, charge and chemical composition revealed that TiO2 chemistry was the main factor responsible for neurite inhibition. [Copyright &y& Elsevier]

Abstract: Nanosize TiO2 thin film on glass substrate was obtained through dip-coating method using TiO2 sol. Suspended nanosize TiO2 sols with anatase structure in aqueous solution were synthesized by sol–gel method using TiCl4 as a precursor. TiCl4 was reacted with an aqueous solution of NH4OH to form Ti(OH)4, and H2O2 was then added to form peroxo titanic acid. It was further heated in water and converted to TiO2. The effects of the preparation parameters, viz., pH value of the Ti(OH)4 gel, concentration of H2O2, and heating temperature and time, on the properties of the TiO2 sol were investigated. The materials were characterized by X-ray diffraction, Fourier transform-infrared spectroscopy, and transmission electron microscopy. The results showed that the primary TiO2 particles were rhombus with the major axis ca. 10 nm and minor axis ca. 4 nm, and were in anatase structure. The sol was excellent in dispersibility and was stable in neutral and even slight basic conditions for at least 2 years without causing agglomeration. The best preparation condition was optimized with the pH value of Ti(OH)4 gel at 8, H2O2/TiO2 mole ratio of 2, and heating at 97 °C for 8 h. The transparent adherent TiO2 film on glass substrates exhibits strong hydrophilicity after illuminating with ultraviolet light and it can be used as an efficient photocatalyst. [Copyright &y& Elsevier]

Abstract: Titania (TiO2) nanotubes were prepared by anodizing titanium (Ti) foils in an electrochemical bath consisting of 1 M glycerol with 0.5 wt.% NH4F.The pH of the bath was kept constant at 6 and the anodization voltage was varied from 5 V, 20 V to 30 V. It is found that the morphology of the anodized titanium is a function of anodization voltage with pits-like oxide formed for the sample made at 5 V and samples made at 20 V and 30 V consisted of well-aligned nanotubes growing perpendicularly on the titanium foil. However, the nanotubes formed on the samples made at 30 V were not uniform in terms of the nanotubes'' diameter and wall thickness. Regardless of the anodization voltage, as anodised samples were amorphous. The crystal structure evolution was studied as a function of annealing temperatures and was characterised by X-ray diffraction and Raman spectroscopy analyses. Crystallization of the nanotubes to anatase phase occurred at 400 °C while rutile formation occurred at 700 °C. Disintegration of the nanotube arrays was observed at 600 °C and the structure completely vanished at 700 °C. TiO2 nanotube annealed at 400 °C and containing 100% anatase revealed the highest photocatalytic activity for the degradation of methyl orange. Consequently, these results indicate that diameter, wall thickness, crystal structure and degree of crystallinity of the TiO2 nanotube arrays are the important factors influencing the efficiency of the photocatalytic activity. [Copyright &y& Elsevier]

Abstract: Anatase TiO2 film (100–1000 nm thick) grown on glass, sapphire (0001), and Si (100) substrates by pulsed dc-magnetron reactive sputtering were evaluated for stress and strain analysis using Raman spectroscopy and curvature measurement techniques. The X-ray analysis revealed that films prepared for this study were purely anatase, and the measurements indicate that the film exhibit that (101) is the preferred growth orientation of the crystallites, especially for the film thicker than 100 nm. Curvature measurements and Raman spectroscopy, with 514.5 nm excitation wavelength, phonon line shift were used for stress analysis. A comparison between Raman lineshapes and peak shifts yields information on the strain distribution as a function of film thickness. The measurements of residual stresses for crystalline anatase TiO2 thin film showed that all thin film were under compressive stress. A correlation between Raman shifts and the measured stress from the curvature measurements was established. The behavior of the anatase film on three different substrates shows that the strain in film on glass has a higher value compared to the strain on sapphire and on silicon substrates. The dominant 144 cm−1 E g mode in anatase TiO2 clearly shifts to a higher value by 0.45–5.7 cm−1 depending on the type of substrate and film thickness. The measurement of the full width at half maximum values of 0.59–0.80 (2θ°) for the anatase (101) peaks revealed that these values are greater than anatase powder 0.119 (2θ°) and this exhibits strong crystal anisotropy with thermal expansion. [Copyright &y& Elsevier]