Iron doped thin TiO2 films synthesized with the RF PECVD method

Iron doped titanium dioxide coatings were synthesized with the help of RF plasma enhanced CVD technique. As a source of titanium, titanium chloride (IV) TiCl₄ was used while iron pentacarbonyl (0) Fe(CO)₅ served as iron supply. The coatings were diagnosed using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Their elemental and chemical composition was studied with the help of X-ray energy dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy, respectively. For the determination of their optical properties, variable angle spectroscopic ellipsometry (VASE) and ultraviolet-visible (UV-Vis) spectroscopy techniques were used. Iron content in the range of 0.07–11.5 at% was found in the films. Apart from oxygen, titanium and iron, a presence of trace amounts of chlorine, very likely originating from the titanium precursor, was recorded. FTIR studies showed that iron was built-in in the structure of TiO₂ matrix. Surface roughness, assessed using SEM and AFM techniques, increases with an increasing content of this element. VASE measurements revealed an increase of the coatings refractive index with a growing iron concentration, with the extinction coefficient remaining low and independent of that parameter. Trace amounts of iron resulted in a lowering of an absorption threshold of the films as well as their optical gap, but the tendency was reversed for high concentrations of that element.     

Ultrasound assisted sol-gel TiO2 powders and thin films for photocatalytic removal of toxic pollutants

The paper presents a study on the structural, surface and photocatalytic properties of the ultrasound assisted sol-gel titanium dioxide particles, as part of stable photocatalytic ink formulations deposited on fabrics. The photocatalytic activity was validated using methylene blue as reference pollutant, under UV, VIS and combined UV+VIS radiation and allowed selecting the optimum TiO₂ samples for inks preparation. To minimize the particles agglomeration stabilizing agents were added and the stability was quantitatively evaluated considering the relative increase in the VIS transmittance for a pre-set period of 30 min. Further on, the ink(s) were deposited by cold spraying on cotton woven fabrics and a removal efficiency higher than 95% was observed in the degradation of the highly toxic mustard gas, after 30 min of UV irradiation.     

Rare earth-doped TiO2 nanocrystalline thin films: Preparation and thermal stability

A colloidal sol–gel route was used for the synthesis of nanoparticulate TiO₂ and Ln³⁺-doped TiO₂ sols (Ln = Eu or Er; contents of 1, 2, or 3 mol.%), from which the corresponding functional nanocrystalline thin films were subsequently obtained by the dip-coating method. It was found that the as-synthesized sols are not entirely suitable for the preparation of homogeneous thin films due to the water's high surface tension, a problem that is however solved by diluting the sols in ethanol. Appropriate dilution conditions were then determined, and the effect of this dilution on the sol viscosity identified. Finally, the phase composition in the as-deposited condition and the thermal stability of the dip-coated thin films were investigated by X-ray thermodiffractometry up to 1000 °C. It was found that the as-deposited thin films are homogenous and formed by the desired anatase nanoparticles, which eventually start to transform into rutile particles at high temperature. However, no precipitation of titanates occurs in the temperature range investigated. Also, it was observed that increasing the Ln³⁺ content improves the thermal stability of these anatase nanocrystalline thin films, an effect that is, if any, slightly more marked for Eu³⁺ than for Er³⁺.     

Magnetic behavior of Ga doped yttrium iron garnet ferrite thin films deposited by sol-gel technique

Yttrium Iron Garnet (YIG) ferrites thin films having compositional formula Y₃Ga_xFe_5-xO₁₂, where (x = 0, 1, 2, 3, 4) are synthesized by sol gel dip coating technique. XRD, SEM and VSM characterizations are employed to explore structural, morphological and magnetic properties, respectively. XRD showed that Ga is completely doped in YIG and not formed any cluster or other phase with YIG. SEM confirmed the formation of agglomeration of YIG particles. Magnetic parameters like coercivity, remnant squareness, saturation magnetization, magnetic moment, anisotropy constant, initial permeability Y–K angles and microwave frequency were calculated of these films. The coercivity and moderate magnetization suggested that fabricated ferrite films are highly applicable in electromagnetic microwave absorption and frequency agile antenna for wireless communication.     

Magnetic studies on one-step chemically synthesized nickel ferrite thin films

Nickel ferrite thin films were synthesized at room temperature using one-step electrodeposition solution processing. Reaction kinetics was also proposed. An effect of air baking on the structural, surface morphological and magnetic properties was investigated. As-deposited nickel ferrite thin films were cubic in crystal structure. Calculated grain size after annealing was increased from 30 to 48 nm in addition to formation of rough surface morphology. Due to decrease in defect levels after air baking the annealed nickel ferrite thin film showed saturation magnetization of 268 emu/cc, higher than non-annealed (230 emu/cc), when used in magnetic studies.     

Niobium/Vanadium doped TiO2 multilayered sol-gel films: Structure,surface chemistry and optical properties

In this work multilayered TiO₂ films deposited on glass and Si substrates by the sol-gel – dipping method were studied, focusing on the influence of Niobium/Vanadium doping on the structure, surface chemistry and their optical properties. The TiO₂ films doped with 1.2 at% Nb(V) crystallized in anatase phase as evidenced by XRD analysis. It was found that thicker films are obtained in the case of V-doped TiO₂ films, while the values of the optical band-gap show similar values. Bands related to the vibration of oxygen in the Ti–O, Nb–O and V–O bonds were identified based on Infrared Spectroscopic Ellipsometry, proving the incorporation of the dopants in the matrix of the TiO₂ films. Both types of doped films exhibit around 80% transparency on a wide spectral range (300–1700 nm). Niobium and Vanadium have been identified in the surface / subsurface region in the 5+ oxidation state (although a high sensitivity of the Vanadium oxidation states during profiling experiments was found due to the preferential sputtering effect). From a morphological point of view, all titania films show a very uniform and compact microstructure, with a homogeneous superficial structure of small grains with diameters in the range of 10–20 nm.     

铈和锰掺杂纳米TiO2的溶胶-凝胶法制备及其光催化性能

采用溶胶-凝胶法制备了TiO₂、Mn⁴⁺/TiO₂、Ce⁴⁺/TiO₂和Mn⁴⁺-Ce⁴⁺/TiO₂光催化剂。通过考察掺杂离子的种类和用量对所得催化剂用于紫外光催化降解甲基橙性能的影响，表明Ce⁴⁺/TiO₂中Ce⁴⁺的适宜掺杂量为1.0%，Ce⁴⁺-Mn⁴⁺/TiO₂中，当Mn4+的掺杂量为25.0%时，Ce⁴⁺的适宜掺杂量为0.50%，相应的脱色效率为92.39%和99.41%。当掺杂量适当时，四种催化剂用于紫外光催化降解甲基橙的活性次序为：Mn⁴⁺-Ce⁴⁺/TiO₂ > TiO₂>Ce⁴⁺/TiO₂> Mn⁴⁺/TiO₂。XRD分析结果表明，所得光催化剂均为锐钛矿型纳米粒子。     

不同金属离子掺杂TiO2薄膜的制备及光催化活性的研究

以溶胶-凝胶法制备了分别用Ag^+、Cu²⁺、Fe³⁺、La³⁺、Ce³⁺和Eu³⁺等离子掺杂的纳米TiO₂薄膜，经XRD和UV-Vis对薄膜样品进行表征并研究了其光催化活性。XRD结果证明，掺镧TiO₂薄膜与未掺杂薄膜的X射线衍射图基本一致，实验条件下主要为锐钛矿型，且掺入La^3+离子使得TiO₂薄膜的晶粒变小。UV-Vis吸收光谱说明当λ＞380 nm时，其吸光度低于0.15。薄膜光催化降解亚甲基蓝的实验表明,La³⁺或Fe^3+掺杂薄膜的光催化降解率远高于未掺杂TiO₂薄膜，而Ce^3+或Cu^2+离子掺杂薄膜与未掺杂薄膜的光催化活性相似，掺Ag⁺或Eu³⁺离子则降低了活性。当最佳掺杂量La³⁺为0.6%或Fe³⁺为1.5%时，光催化降解率分别高达92%和82%。     

Thickness effect in the photocatalytic activity of TiO2 thin films derived from sol-gel process

TiO₂ films in various thicknesses were prepared by sol-gel method, and their photocatalytic activities in the decomposition of gaseous 2-propanol were evaluated. It was found that the photocatalytic activities of transparent TiO₂ films increase with the increase of film thickness: The photocatalytic activity of TiO₂ films in 670 nm-thickness was 3.7 times that of films in 70 nm-thickness. We proposed that the higher photocatalytic activities for the thicker TiO₂ films originate from the greater amount of photogenerated electron and hole pairs, which are transferred from the inside to the surface of TiO₂ films. We also provided some experimental evidences supporting this mechanism.     

Magnetic properties of electrodeposited CoFeB thin films and nanowire arrays

A pulse electrodeposition method for preparing stress-free CoFeB thin films is described. The method was optimized to produce amorphous films with soft magnetic properties and the best composition was found to be Co₉₄Fe₅B₁. The optimized conditions were used to obtain arrays of ordered nanowires, using nanoporous alumina membranes as templates. While magnetization measurements demonstrate that the microstructure of the array influences the detailed characteristics of the hysteresis loops, the general pattern of the magnetization curves, characterized by high saturation fields and low squareness, is the same as for crystalline Co arrays obtained in similar conditions. This observation, as well as data obtained from variable temperature measurements, shows that the overall magnetic behavior is determined mainly by the competition of the shape anisotropy and magnetostatic interactions. Whether the wire axis is easy or hard for the array depends upon the array geometry: wire diameter, length and the packing density of the wires. In order to explain these effects, a micromagnetic model was used to calculate the saturation fields for in-plane and out-of-plane magnetized array, as a function of the geometrical parameters. These agree well with the experimental results.     

(001)-oriented Cu2-ySe thin films with tunable thermoelectric performances grown by pulsed laser deposition

Highly (001)-oriented Cu_2-ySe thin films with tunable thermoelectric performances have been grown by pulsed laser deposition. By using targets with different Cu/Se ratios that further determines the copper deficiency of as-grown films, the carrier concentrations of as-grown films are tuned within a broad range from 10¹⁸ to 10²¹ cm⁻³. The optimum performance is observed at carrier concentration ~1.58×10²⁰ cm⁻³. The distinct properties of Cu_2-ySe thin films with nearly ideal chemical stoichiometric ratio are observed. In addition, a weak change in the electrical transport during the second-order phase transition was observed in the thin films due to the anisotropic structure of the Cu_2-ySe.     

Reversible,repeatable and low phase transition behaviour of spin coated nanostructured vanadium oxide thin films with superior mechanical properties

Smooth, uniform and crystalline vanadium oxide thin films were deposited on quartz by spin coating technique with four different rpm i.e., 1000, 2000, 3000 and 4000 and subsequently post annealed at 350, 450 and 550?°C in vacuum. Transmission electron microscopy (TEM), Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) techniques were utilized for microstructural characterizations and phase analysis, respectively, for vanadium oxide powder and deposited film. Nanorods were observed to be grown after vacuum annealing. X-ray photoelectron spectroscopy (XPS) technique was utilized to study the elemental oxidation state of deposited vanadium oxide films. Thermo-optical and electrical properties such as solar transmittance (τ_s), reflectance (ρ_s), absorptance (α_s), infrared (IR) emittance (ε_ir) and sheet resistance (R_s) of different thin films were evaluated. Based on the optical characteristics the optimized condition of the film processing was identified to be spin coated at 3000?rpm. Subsequently, the nanoindentation technique was utilized to measure hardness and Young's modulus of the optimized film. The measured nanomechanical properties were found to be superior to those reported for sputtered vanadium oxide films. Finally, temperature dependent phase transition characteristics of optimized vanadium oxide films were studied by differential scanning calorimetry (DSC) technique. Reversible and repeatable phase transition was found to occur in the range of 44–48?°C which was significantly lower than the phase transition temperature (i.e., 68?°C) of bulk VO₂.     

Surface structural features and optical analysis of nanostructured Cu-oxide thin film coatings coated via the sol-gel dip coating method

Nanostructured thin film coatings of copper oxide (Cu-oxide) were investigated to determine their physical structure, surface morphology, surface electronic bonding states, and optical properties. The Cu-oxide had been coated onto reflective aluminum substrates via a facile one-step sol–gel dip-coating route using a copper nitrate precursor. Characterizations were conducted using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and ultra-violet visible (UV–Vis) spectroscopic methods, and representative sol-gel reactions using copper nitrate precursor were proposed. The XPS spectra confirmed the presence of copper oxide elements. Further exploration of the Cu2p3/2 peak in XPS spectra revealed that the electronic structure of the copper component consisted of tetrahedral Cu(I) and octahedral Cu(II) with the presence of octahedral Cu(II) enabling coatings to have high absorption levels across the solar spectrum. The deconvolution of the O1s spectra exhibited three curve-fitting components: the lattice O²⁻, surface oxygen, and subsurface O⁻ species. FESEM results showed that the coating surface was an agglomerated copper oxide nanoparticles structure forming a porous structure. The optical band-gap of Cu-oxide thin film coatings, via the Tauc plot, was 2.7 eV.     

Electrodeposition of magnetic CoPd thin films: Influence of plating condition

The manufacture and properties evaluation of Co-based thin film alloys are extensively studied because of their magnetic properties that make them a critical element in many different applications and devices. Therefore the electrodeposition of CoPd alloy thin films was studied from a chloride bath containing glycine as additive. The cobalt content in the CoPd deposits varied from 6.4 to 94.0 at% by controlling the pH and [Co²⁺]/[Pd²⁺] ratio in the bath. Current efficiencies were independent of the solution pH and bath composition. The morphology of the deposits depended on the applied current density: current densities higher than 50 mA cm⁻² resulted in deposits with a typical cauliflower morphology. For current densities lower than 25 mA cm⁻² cracks was observed. The XRD measurements showed that all CoPd alloys were amorphous. The magnetic properties for CoPd alloys revealed that the coercivity (H_c) values ranged from 84 up to 555 Oe and the magnetic saturation (M_s) from 0 to 1.73 T.     

Effect of Y concentration and film thickness on microstructure and electrical properties of HfO2 based thin films

In this work, we introduced a simple solution processing method to prepare yttrium (Y) doped hafnium oxide (HfO₂) based dielectric films. The films had high densities, low surface roughness, maximum permittivity of about 32, leakage current < 1.0 × 10^?7 A/cm² at 2 MV/cm, and breakdown field >5.0 MV/cm. In addition to dielectric performance, we investigated the influence of YO_1.5 fraction on the electronic structure between Y doped HfO₂ thin films and silicon (Si) substrates. The valence band electronic structure, energy gap and conduction band structure changed linearly with YO_1.5 fraction. Given this cost-effective deposition technique and excellent dielectric performance, solution-processed Y doped HfO₂ based thin films have the potential for insulator applications.     

Electrical properties of nanoporous F doped SiO2 low-k thin films prepared by sol-gel method with catalyst HF

Using hydrofluoric acid as acid catalyst, F doped nanoporous low-k SiO₂ thin films were prepared through sol-gel method. Compared with the hydrochloric acid catalyzed film, the films showed better micro structural and electrical properties. The capacitance-voltage and current-voltage characteristics of F doped SiO₂ thin films were then studied based on the structures of metal-SiO₂-semiconductor and metal-SiO₂-metal, respectively. The density of state (DOS) of samples deposited on metal is found to decrease to a level of 2 × 10¹⁷ eV^?1 cm^?3. The values of mobile ions, fix positive charges, trapped charges and the interface state density between the SiO₂/Si interfaces also decrease obviously, together with the reduction of the leakage current density and the dielectric constant, which imply the improvement of the electrical properties of thin films. After annealing at a temperature of 450^°C, the lower values of the leakage current density and dielectric constant could be obtained, i.e. 1.06 × 10^?9 A/cm² and 1.5, respectively.     

Phase transition,microstructure and electrical properties of Fe doped Ba0.70Ca0.30TiO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics of Ba_0.70Ca_0.30Ti_1?xFe_xO₃ (x=0–0.03) have been synthesized by a conventional solid state reaction method. The influence of Fe content on the microstructure, phase transition, dielectric, ferroelectric, and piezoelectric properties is investigated systematically. The ceramics with x≤0.02 are diphasic composites of tetragonal Ba_0.80Ca_0.20TiO₃:Fe and orthorhombic Ba_0.07Ca_0.93TiO₃:Fe solid solutions. The tetragonal phase is gradually suppressed as x increases, the ceramic with x=0.03 is found to have diphasic pseudocubic and orthorhombic phases. And the grain size is dependent on Fe content significantly. Introduction of Fe at B-sites improves the densification and decreases the sintering temperature. As x increases from 0 to 0.03, the room temperature relative dielectric permittivity enhances, dielectric loss decreases, and the Curie temperature decreases monotonically from 128 °C to 58 °C. However, the ferroelectricity enhances slightly and reaches the maximum near x=0.005, and then weakens with increasing x. On the other hand, the piezoelectric coefficient (d₃₃) and the electromechanical coupling coefficient (k_p) decrease simultaneously with increasing x, whereas the mechanical quality factor (Q_m) increases significantly. The structure–electrical properties relationship is discussed intensively to give more information on (Ba,Ca)TiO₃-based lead-free piezoelectric ceramics.     

Influence of rare earth addition in cobalt ferrite thin films obtained by pulsed laser deposition

The influence of rare earth (RE = Dy, Gd, Yb) ion doping on the structural, magnetic and optical properties of cobalt ferrite thin films was studied. CoFe_2-xRE_xO₄ (x = 0.01; 0.03; 0.05; 0.1; 0.2; 0.3) films were obtained by pulsed laser deposition on silicon substrates. The X-ray diffraction and Raman spectroscopy results on the bulk materials, which were used as targets during deposition, revealed the formation of residual phases as the concentration of RE dopant was increased. However, the annealed thin films presented diffraction lines and vibrational modes corresponding only to cobalt ferrite. A lower crystallinity of the deposited samples was observed when higher RE concentrations were used. Due to the substitution of Fe by RE elements which possess large ionic radii, the lattice parameter of the thin films presented a monotonous increase. The magnetic response of the nanostructures was correlated to the magnetic moment of the RE dopant and to the structural properties of the films. The optical bandgaps derived from the reflectance spectra presented an increasing trend as the Yb and Dy concentrations were augmented.     

Highly conducting and transparent antimony doped tin oxide thin films: the role of sputtering power density

Sb doped SnO₂ thin films were deposited on quartz substrates by magnetron sputtering at 600 °C and the effects of sputtering power density on the preferential orientation, structural, surface morphological, optical and electrical properties had been studied. The XRD analyses confirm the formation of cassiterite tetragonal structure and the presence of preferential orientation in (2 1 1) direction for tin oxygen thin films. The dislocation density analyses reveal that the generated defects can be suppressed by the appropriate sputtering power density in the SnO₂ lattice. The studies of surface morphologies show that grain sizes and surface roughness are remarkably affected by the sputtering power density. The resistivity of Sb doped SnO₂ thin films gradually decreases as increasing the sputtering power density, reaches a minimum value of 8.23×10⁻⁴ Ω cm at 7.65/cm² and starts increasing thereafter. The possible mechanisms for the change in resistivity are proposed. The average transmittances are more than 83% in the visible region (380–780 nm) for all the thin films, the optical band gaps are above 4.1 eV. And the mechanisms of the variation of optical properties at different sputtering power densities are addressed.