Enhancement of fatigue endurance and retention characteristic in Bi3.25Eu0.75Ti3O12 thin films

The effects of moderate annealing temperature (600–800 °C) on the microstructure, fatigue endurance, retention characteristic, and remnant polarization (2P_r) of Bi_3.25Eu_0.75Ti₃O₁₂ (BET) thin films prepared by metal-organic decomposition (MOD) were studied in detail. 2P_r (66 µC/cm² under 300 kV/cm), fatigue endurance (3% loss of 2P_r after 1.2 × 10¹⁰ switching cycles), and retention characteristic (no significant polarization loss after 1.8 × 10⁵s) for BET thin film annealed at 700 °C are better than those for thin films annealed at other temperature. The mechanisms concerning the dependence of microstructure and ferroelectric properties on the annealing temperature were discussed.     

Structural, optical and electrical characterization of spray-deposited TiO2 thin films

Titanium oxide (TiO₂) thin films were deposited onto glass substrates by means of spray pyrolysis method using methanolic titanyl acetyl acetonate as precursor solution. The thin films were deposited at three different temperatures namely 350, 400 and 450 °C. As-deposited thin films were amorphous having 100–300 nm thickness. The thin films were subsequently annealed at 500 °C in air for 2 h. Structural, optical and electrical properties of TiO₂ thin films have been studied. Polycrystalline thin films with rutile crystal structure, as evidenced from X-ray diffraction pattern, were obtained with major reflexion along (1 1 0). Surface morphology and growth stages based on atomic force microscopy measurements are discussed. Electrical properties have been studied by means of electrical resistivity and thermoelectric power measurements. Optical study shows that TiO₂ possesses direct optical transition with band gap of 3.4 eV.     

Influence of Nb dopant on the structural and optical properties of nanocrystalline TiO2 thin films

In this study, preparation of Nb-doped (0-20 mol% Nb) TiO₂ dip-coated thin films on glazed porcelain substrates via sol-gel process has been investigated. The effects of Nb on the structural, optical, and photo-catalytic properties of applied thin films have been studied by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Surface topography and surface chemical state of thin films was examined by atomic force microscope and X-ray photoelectron spectroscopy. XRD and Raman study showed that the Nb doping inhibited the grain growth. The photo-catalytic activity of the film was tested on degradation of methylene blue. Best photo-catalytic activity of Nb-doped TiO₂ thin films were measured in the TiO₂-1 mol% Nb sample. The average optical transmittance of about 47% in the visible range and the band gap of films became wider with increasing Nb doping concentration. The Nb⁵⁺ dopant presented substitutional Ti⁴⁺ into TiO₂ lattice.     

Effects of post-deposition surface treatment on the optical, structural and hydrogen sensing properties of TiO2 thin films

TiO₂ thin films were prepared by DC reactive magnetron sputtering in a mixture of oxygen and argon on glass and oxidized silicon substrates. The effect of post-deposition annealing (300 °C, 500 °C and 700 °C for 8 h in air) on the structural and morphological properties of TiO₂ thin films is presented. In addition, the effect of Pt surface modification (1, 3 and 5 nm) on hydrogen sensing was studied. XRD patterns have shown that in the range of annealing temperatures from 300 °C to 500 °C crystallization starts and the thin film structure changes from amorphous to polycrystalline (anatase phase). In the case of samples on glass substrate, optical transmittance spectra were recorded. TiO₂ thin films were tested as sensors of hydrogen at concentrations 10,000-1000 ppm and operating temperatures within the 180-200 °C range. The samples with 1 nm and in particular with 3 nm of Pt on the surface responded to hydrogen fast and with high sensitivity.     

Preparation, electrical and optical properties of (Pb,Ca)TiO3 thin films using a modified sol-gel technique

Calcium modified lead titanate sol was synthesized using lead acetate trihydrate, calcium nitrate tetrahydrate and titanium tetra-n-butoxide as starting materials, methanol and ethanolamine were selected as solvent and stabilizing or complexing agent, respectively. (Pb_0.76Ca_0.24)TiO₃ thin films were prepared on platinum-coated silicon and fused silica substrates with the solution using the spinning method. The surface morphology and crystal structure, surface compositions and chemical states, electrical and optical properties of the thin films were investigated. The films have good composition homogeneity and thickness uniformity. The dielectric constant and dissipation factor of 1 kHz at room temperature were found to be 280 and 0.027, respectively, for thin films with 0.5 μm thickness annealed at 600°C for 1 h. The remanent polarization and coervive field were 15 μC/cm² and 64 kV/cm, respectively. The thin films exhibited good optical transmissitivity, and had optical direct transitions. The dispersion relation of refractive index and wavelength followed the single electron oscillation model. The band gap of the film which annealed at 650°C was 3.68 eV. The results also confirmed that ethanolamine was very effective in preparing uniform and dense oxide films, owing to the superior stability of the sols during hydrolytic polycondensation.     

铁基纳米晶带材表面TiO2薄膜制备及其磁性能研究

介绍了一种通过溶胶-凝胶法在铁基纳米晶带材表面制备TiO2薄膜的方法,并研究了涂层后对带材的磁性能影响.结果表明,通过溶胶-凝胶法可在带材表面形成一层TiO2薄膜;带材表面变得光滑、平整;涂层后带材的有效磁导率下降,品质因数增加,软磁性能下降;提拉2次得到的薄膜对带材磁性能影响最小.     

Thermal treatment effect on the optical properties of ZrO2 thin films deposited by thermionic vacuum arc

This paper shows the ex situ thermal treatment effects of the ZrO₂ thin films obtained by TVA (thermionic vacuum arc) technique on the optical properties (e.g., transmittance, refractive index and band-gap energy) of ZrO₂ thin films. The crystal structure, surface and optical properties were investigated for ZrO₂ thin films deposited on glass substrates by thermionic vacuum arc (TVA) method. The thermal treatment effect on the optical properties of the thin films was determined. The XRD analysis showed that the deposited ZrO₂ thin films have baddeleyite (monoclinic) and zirconium (hexagonal) structures. The thicknesses and refractive index were determined by interferometric measurements. The thin films were thermal treated at different temperatures (350 °C, 450 °C and 550 °C), and the analysis showed that the optical properties of ZrO₂ deposited thin films were improved by thermal treatment at 450 °C.     

Photocatalytic properties of porous TiO2/Ag thin films

In this study, nanocrystalline TiO₂/Ag composite thin films were prepared by a sol-gel spin-coating technique. By introducing polystyrene (PS) spheres into the precursor solution, porous TiO₂/Ag thin films were prepared after calcination at a temperature of 500 °C for 4 h. Three different sizes (50, 200, and 400 nm) of PS spheres were used to prepare porous TiO₂ films. The as-prepared TiO₂ and TiO₂/Ag thin films were characterized by X-ray diffractometry (XRD) and by scanning electron microscopy to reveal structural and morphological differences. In addition, the photocatalytic properties of these films were investigated by degrading methylene blue under UV irradiation.When PS spheres of different sizes were introduced after calcination, the as-prepared TiO₂ films exhibited different porous structures. XRD results showed that all TiO₂/Ag films exhibited a major anatase phase. The photodegradation of porous TiO₂ thin films prepared with 200 nm PS spheres and doped with 1 mol% Ag exhibited the best photocatalytic efficiency where ∼ 100% methylene blue was decomposed within 8 h under UV exposure.     

Effect of thermal annealing time on optical and structural properties of TeO2 thin films

TeO₂ thin films were deposited on quartz substrates by rf reactive sputtering technique from a Te metal target. The obtained samples were annealed in an argon atmosphere at 450 °C for different annealing times up to 90 min. X-ray diffraction studies revealed that the as-grown samples were amorphous and there was no appreciable change in structure for a short annealing time. Thin films became polycrystalline with the tetragonal (α-phase) structure of tellurium dioxide crystal with the increase of the thermal annealing time. The refractive index and optical energy gap of the films were calculated by modelling transmittance spectra. The optical energy gap decreased continuously from 3.83 eV to 3.71 eV with increasing thermal annealing time.     

Effect of SnO2 on the photocatalytical properties of TiO2 films

TiO₂/SnO₂ thin films with different tin atomic percentages were successfully prepared on glass substrates by the spray pyrolysis method from an alcoholic solution of TiO[C₅H₇O₂]₂ with different concentrations of SnCl₄. The TiO₂/SnO₂ thin films prepared at 450 °C presented the anatase phase in polycrystalline configuration from %Sn = 0 in the starting solution up to %Sn = 20, at higher tin content the films present an amorphous configuration. The resulting thin films have a homogeneous surface structure with some porosity. The photocatalytical properties of the films were evaluated with the degradation of methylene blue. The products of the degradation reaction were identified by ¹H nuclear magnetic resonance and the film properties were studied by atomic force microscopy, scanning electron microscopy, UV–Vis spectroscopy, and X-ray diffraction.     

Structural, thermal and optical characterization of TiO2:ZrO2 thin films prepared by sol-gel method

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 (63-286 nm). 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 3 months in ambient temperature, we have noticed the formation of the anatase phase (tetragonal structure with 14.8 nm 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 (8.58-20.56 nm).     

Hydrophilicity on carbon-doped TiO2 thin films under visible light

Carbon-doped TiO₂ thin films in the anatase phase with dopant concentrations of 1.1, 0.9, and 0.7 mol% were fabricated by a radio-frequency magnetron sputtering method. Dopant carbons were located at the oxygen sites. Carbon substitution caused the absorbance edge and/or the shoulder of TiO₂ to shift to a higher wavelength region. Carbon-doped TiO₂ thin films underwent a hydrophilic conversion when irradiating with visible light (400–530 nm). The hydrophilic property under visible light was inferior to that under ultraviolet light, which is explained by considering that the visible light sensitivity originates from the localized C 2p formed in the band-gap.     

Thermal optical properties of TiO2 films

A fibre optic experimental arrangement was used to determine the thermo-optic coefficient (dn/dT) of electron beam deposited titanium dioxide coatings on the cleaved end faces of multimode optical fibres for a wavelength range between 600 and 1050 nm. The temperature-induced change in the index of refraction (n) and extinction coefficient (k) were successfully determined from reflection spectra. Measurements of n and k at various wavelengths for different temperatures enabled the determination of dn/dT and dk/dT. It was found that dn/dT takes different values at different temperature ranges. For example, at 800 nm, dn/dT was (−1.77±0.7)×10⁻⁴ K⁻¹, between 18°C and 120°C, and took a value of (−3.04±0.7)×10⁻⁴ K⁻¹ between 220°C and 325°C.     

Effect of Nb, Cr, Sn additions on gas sensing properties of TiO2 thin films

The effect of Nb and Cr dopants as well as Sn⁴⁺ additions on the electronic structure of rf-sputtered TiO₂ thin films and its subsequent influence on gas sensor performance is reported. The changes in the electrical conductivities of TiO₂ thin films doped with up to 10 at.% Nb, 4 at.% Cr and TiO₂-SnO₂ in the full range of compositions upon exposure to hydrogen and oxygen are demonstrated. The spectral dependence of the absorption coefficient in the vicinity of the band gap transition of TiO₂ is shown to be affected by doping.     

WO3/TiO2复合薄膜的制备及其电致变色性能

使用水热法在掺氟SnO₂涂覆的导电玻璃（FTO）基板上生长TiO₂纳米线,随后在TiO₂纳米线上采用水热法生长WO₃纳米线,制备出WO₃/TiO₂复合薄膜。通过循环伏安法（CV）、计时电流法（CA）、计时电量法（CC）等电化学测试技术研究了WO₃/TiO₂复合薄膜的电致变色性能;采用紫外分光光度计对薄膜的着色﹑漂白状态的响应时间进行测试。通过以上测试,计算得到了薄膜的循环稳定性﹑光调制﹑着色效率和切换时间（Y和X）等参数。结果显示WO₃/TiO₂复合薄膜的电致变色性明显提高,其中WO₃/TiO₂复合薄膜可逆性增加了6%,着色效率提高了40.96 cm2/C。      

Structural and optical properties of heteroepitaxial beta Ga2O3 films grown on MgO (100) substrates

Gallium oxide (Ga₂O₃) films were deposited on MgO (100) substrates by metalorganic vapor phase epitaxy. Structure analyses showed that the films deposited at 550-700 °C were epitaxial β-Ga₂O₃ films with an out of plane relationship of β-Ga₂O₃(100)||MgO(100). The film deposited at 650 °C showed the best crystallinity and the microstructure of the film was investigated by high resolution transmission electron microscopy. A theoretical model of the growth mechanism was proposed and the in-plane epitaxial relationship was given to be β-Ga₂O₃[001]||MgO<011>. A four-domain structure inside the epitaxial film was clarified. The β-Ga₂O₃ film deposited at 650 °C showed an absolute average transmittance of 95.9% in the ultraviolet and visible range, which had an optical band gap of 4.87 eV.     

Behaviors of different dispersers on morphologies of porous TiO2 films

TiO₂ films with nanoparticles dispersed by using three different additives such as acetylacetone, Emulsifier OP-10, and polyethylene glycol, respectively. It is found that for the TiO₂ films produced with appropriate amount of Emulsifier OP-10, there are no reaggregation of TiO₂ nanoparticles with pores of about 5–20 nm. By adding polyethylene glycol, the pore size of the TiO₂ films could be in the range from about 50 to 200 nm. However, by using acetylacetone, aggregations of TiO₂ nanoparticles always exist in the TiO₂ films. The related mechanism on the aggregation of nanoparticles in the TiO₂ slurries is discussed.     

Hydrophilicity of anatase TiO2/Cr-doped TiO2 thin films with different band gaps

Based on the concept that the electron-hole separation effect caused by a different band-gap structure would improve its hydrophilicity, anatase-TiO₂/Cr-doped TiO₂ thin films were synthesized by DC magnetron sputtering. The optical band gaps of TiO₂ thin films decreased from 3.23 to 2.95 eV with increasing Cr-doping content. Multilayer TiO₂ thin films with different band gaps exhibited a superhydrophilicity under UV illumination. In particular, in anatase TiO₂ (3.23 eV)/4.8% Cr-doped TiO₂ (2.95 eV), the hydrophilicity, which indicated a contact angle of less than 20°, lasted for 48 h in the dark after UV illumination was discontinued. This outstanding result has rarely been reported for TiO₂ thin films, which confirmed that the prominent superhydrophilicity of anatase TiO₂/Cr-doped TiO₂/glass could be attributed to the retardation of electron-hole recombination caused by the band-gap difference.     

Chemical vapor deposition and characterization of nitrogen doped TiO2 thin films on glass substrates

Photocatalytically active, N-doped TiO₂ thin films were prepared by low pressure metalorganic chemical vapor deposition (MOCVD) using titanium tetra-iso-propoxide (TTIP) as a precursor and NH₃ as a reactive doping gas. We present the influence of the growth parameters (temperature, reactive gas phase composition) on the microstructural and physico-chemical characteristics of the films, as deduced from X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and ultra-violet and visible (UV/Vis) spectroscopy analysis. The N-doping level was controlled by the partial pressure ratio R = [NH₃]/[TTIP] at the entrance of the reactor and by the substrate temperature. For R = 2200, the N-doped TiO₂ layers are transparent and exhibit significant visible light photocatalytic activity (PA) in a narrow growth temperature range (375-400 °C). The optimum N-doping level is approximately 0.8 at.%. However, the PA activity of these N-doped films, under UV light radiation, is lower than that of undoped TiO₂ films of comparable thickness.     

Microstructure and optical properties of photoactive TiO2:N thin films

In this work, we have chosen oxidation of TiN thin films as a feasible method for preparation of nitrogen-doped titanium dioxide thin films, TiO₂:N, for photocatalytic applications. DC reactive magnetron sputtering with the plasma emission control was used for deposition of stoichiometric TiN thin films. The microstructure and chemical composition of films before and after oxidation were investigated by means of RBS, X-ray diffraction (XRD) in grazing incidence diffraction (GID) configuration, AFM and XPS techniques. The electrical conductivity was measured by the van der Pauw method as a function of the oxidation temperature. The optical transmittance and reflectance spectra of the films were measured over the visible and UV ranges of the light spectrum. GID diffraction patterns of as-sputtered TiN thin films and those after oxidation indicate that TiO₂ rutile is formed at around 300 °C. Nitrogen is still present as indicated by XPS studies even when XRD detects the rutile only. Optical absorption of thin films oxidized at 450 °C is shifted towards the visible range of the light spectrum.