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• Dielectric analysis is used to analyze the observed magnetic transitions. • Due to magnetoelectric coupling, magnetic changes are observed in dielectric spectra. • Shift in raman modes and change in bond length are shown as a function of eu content. • Magnetic transitions are observed due to reorientation of spins along different axis. BiFeO 3 is a multiferroic material, so its ferroelectric and ferromagnetic properties are coupled. Due to the presence of magneto-electric coupling in the system, magnetic changes are obvious in the dielectric spectra. As a thin film of BFO exhibits a weak magnetic moment, dielectric analysis can be utilized to observe different magnetic transitions. In the present work, thin films of Eu3+ substituted BiFeO 3 are prepared to stabilize the Perovskite phase. The role of Eu3+ substitution in triggering the structural phase transformation is analyzed using Raman analysis. Capacitance and dissipation spectrum as a function of temperature for various Eu3+ concentrations are studied in detail. The presence of various transitions is observed in the dielectric permittivity. The possible origin of the transitions in permittivity spectra is discussed in terms of spin-lattice and charge interactions and their degrees of freedom. Substitution with rare-earth ions significantly affects the system's magnetic characteristic, including contribution from magnetization from sub-lattice and magnetic anisotropy. Eu3+ substitution led to the change in the spin reorientation axis, which has been explained in terms of phenomenological and microscopic variation in magnetization due to the contribution from the rare earth ion. [ABSTRACT FROM AUTHOR]

Abstract Al doped zinc magnesium oxide (Zn 1-x Mg x O:Al) thin films with tunable optical bandgap (3.48 eV–3.66 eV) and resistivity level of 10−3 Ω·cm were prepared by sol-gel process. The effect of the Mg incorporation on the structural, electrical and optical properties was studied by analyzing the results of X-ray diffraction diffractograms, transmittance spectra, Hall measurement and X-ray photoelectron spectroscopy. Mg incorporation influences the crystal structure through reducing the c-axis lattice constant. Blueshift of absorption edge with Mg incorporation manifests the bandgap widening effect. Mg incorporation also increases the film resistivity through decreasing Hall mobility and carrier concentration. Employed as the front electrode, these Zn 1-x Mg x O:Al thin films improved the blue response of hydrogenated amorphous silicon solar cells through reducing the optical loss in ZnO:Al. Zn 1-x Mg x O:Al with x ≤ 0.13 enables an open-circuit voltage (V oc) of about 0.9 V and a fill factor (FF) of about 0.7. The Zn 0.87 Mg 0.13 O:Al empowers a gain of about 9% in short-circuit current density relative to ZnO:Al via the bandgap widening and the improved refractive-index-matching, while the Zn 0.80 Mg 0.20 O:Al deteriorates V oc and FF through increasing the downward band bending at the Zn 1-x Mg x O:Al/p-a-SiC:H interface. This work paves the way for applying the sol-gel derived Zn 1-x Mg x O:Al thin films to optoelectronic devices such as ultraviolet light detector, ultraviolet light emitting diodes and solar cells. Highlights • Low-resistance Zn 1-x Mg x O:Al thin films were obtained with sol-gel process. • Sol-del derived Zn 1-x Mg x O:Al was applied to the electrode of a-Si:H solar cells. • Zn 1-x Mg x O:Al (x ≤ 0.13) enabled a V oc of about 0.9 V and a FF of about 0.7. • Zn 0.87 Mg 0.13 O:Al empowered a J sc gain of about 9% relative to ZnO:Al. [ABSTRACT FROM AUTHOR]

Accessibility and specific surface area are important factors related to the functions and efficiencies of thin films that act as adsorbents, supports for catalysts, and so on. Therefore, controlling the surface morphology or macro porosity has attracted a great deal of attention. In this work, a spontaneous silica film growth process in a sol–gel solution was studied by observing electron microscopy images as well as by using UV-VIS spectroscopy and surface roughness measurements. As a result, a macroporous silica film was formed in a sol–gel solution containing Pluronic P123 as a structure-directing agent. Furthermore, a preparation of macroporous silica films that have different morphologies was attained by using different Pluronic surfactants and inorganic salts. Some films had a micrometer order rod-like structure, and others had a reticular structure composed of a concatenation of short rod-like nanoparticles. Nitrogen adsorption desorption isotherms were measured for silica deposits that formed during film growth in the sol–gel solution to discuss the characteristics of the silica thin films. [ABSTRACT FROM AUTHOR]

Self-supporting mesoporous silica thin films are generally fabricated by the first high-temperature thermal degradation of the pore-forming templates and the subsequent dissolution of the substrates . Herein, the poly-α-methyl styrene (PAMS) layers were treated as the sacrificial substrates for the preparation of nanoporous silica aerogel thin films, and the sacrificial substrates were eliminated by a low-temperature thermal degradation. In this work, the obtained self-supporting silica aerogel thin film had a large size of about 8 mm × 8 mm, and exhibited high flexibility. In addition, effect of the viscosity on the properties and microstructures of the films was also examined. [ABSTRACT FROM AUTHOR]

An easy and effective method for fabricating a two layer structure of superhydrophobic inorganic/organic thin film with good mechanical property was developed by sol–gel process. The inorganic/organic thin film that is composed of SiO 2 sol and polyvinyl butyral (PVB). The modified-SiO 2 nanoparticles was effectively modified by methoxytrimethysilane and sprayed on an inorganic/organic (SiO 2 + PVB)-coated polycarbonate substrate. The water contact angle of the superhydrophobic inorganic/organic (SiO 2 + PVB) thin film was more than 150° and the average transmittance was 92.7% in the visible wavelength (400–700 nm). According to ISO 2409 standard, the adhesion of the coated film has a quality of rank 1. The hardness was greater than 3H as performed by pencil hardness test. In addition, the superhydrophobic property was maintained after the thin film was treated by pressing wipe paper under a 500 g weight and moving it parallel to the sample. The results demonstrate that the superhydrophobic inorganic/organic (SiO 2 + PVB) thin film has properties of superhydrophobicity, and good mechanical and optical properties. [ABSTRACT FROM AUTHOR]

Pyroelectric Pb(Zr 0.52 Ti 0.48 )O 3 films have been grown by sol–gel process on Si(001). Intrinsic pyroelectric coefficient has been measured through ferroelectric loops recorded at different temperatures and is about − 300 μC/m 2 K. Corresponding converted pyroelectric power density is estimated to be ~ 1 mW/cm 3 for a temperature variation of 10 °C every 6 s. Pyroelectric response of these films has been confirmed by direct measurements of the pyroelectric current with temperature variations at zero electric field. These results are of high interest for integrated thermally-sensitive devices. [ABSTRACT FROM AUTHOR]

NiO films were grown epitaxially on MgO (100) substrates by a sol–gel spin-coating technique using a solution of nickel acetate tetrahydrate in 2-methoxyethanol stabilized by monoethanolamine. X-ray diffraction, high-resolution transmission electron microscopy, and selected-area electron diffraction analyses indicated that the NiO films grew epitaxially on the MgO substrates. X-ray reciprocal space maps around the asymmetric 311 diffraction point revealed that the NiO films were in a partially strained state, with the lattice parameter contracted along the direction normal to the surface and expanded along the direction parallel to the surface in each film, caused by a lattice mismatch between NiO and MgO. Strain relaxation was gradually enhanced as the film thickness increased. In addition, the Poisson's ratio of NiO was estimated to be about 0.22 from the lattice parameter changes, which is somewhat lower than the value predicted from the elastic constants of NiO. [ABSTRACT FROM AUTHOR]

We investigate the effects of preheating temperature on the crystalline state of seed layer and hydrothermal ZnO nanorods grown thereon. The ZnO seed layers are deposited on Si (100) substrates by sol–gel multi-spin coatings and preheated at different elevated temperatures. Average grain size of ZnO seeds measured by scanning electron microscopy at each temperature of 100, 200, and 300 °C is about 29, 21, and 19 nm, respectively, and the more intense (002) reflection by X-ray diffraction (XRD) and higher ultra-violet emission peak from photoluminescence are observed at lower preheating temperature. The seed layers also exhibit a tendency of increase in oxygen vacancy concentration due to the increase in crystal defects present in the thin film with the increase of preheating temperature. The nanorod crystals grown by hydrothermal method exhibit a strong dependence of growth alignment along (002) orientation of the seed layer influenced by the preheating temperature as revealed by XRD analysis after nanorod growth. [ABSTRACT FROM AUTHOR]

(TiO 2 ) 1 − x –(ZnO) x thin films, with x = 0.00, 0.25, 0.50, 0.75, and 1.00, were deposited on glass substrates by the sol–gel process. Pure TiO 2 and ZnO thin films were synthesized from titanium isopropoxide-based and zinc acetate-based precursor solutions, respectively, whereas the composite films were obtained from the mixture of these solutions at specific vol.% ratios. Using the Tauc model, it was determined that the band-gap energy increased from 3.43 eV for the TiO 2 thin films up to 3.60 eV for the sample with x = 0.50. With further increase in x, the absorption edges of the films were red-shifted and the band-gap energy decreased down to 3.29 eV for the ZnO thin films. Additionally, the films were evaluated for their ability to degrade methylene blue. The photocatalytic activity of pure ZnO thin films was enhanced by aging the ZnO sol for 48 h. Moreover, it was found that the photocatalytic performance improved by decreasing the x value, with the TiO 2 thin films displaying the highest response. These results are explained in terms of the crystallinity and the surface morphology of the (TiO 2 ) 1 − x –(ZnO) x thin films. [ABSTRACT FROM AUTHOR]

A modified sol–gel process was developed for the fabrication of sub-micrometer scale yttrium-doped barium zirconate (BZY) thin film at much lower processing temperatures. The film was fabricated by direct spin-coating of the sol on a Si 3 N 4 passivated Si substrate, followed by low temperature thermal annealing at 1000 °C, and single BZY phase without barium carbonate residue was obtained. A 200 nm-thick thin film without obvious through-film cracks was fabricated with optimized process parameters of sol concentration and heating rate. The stoichiometry of the BZY thin film was well-controlled and no Ba evaporation was observed due to the low processing temperature. The combination of sol–gel and spin coating method can be a promising alternative to vacuum-based thin film deposition techniques for the fabrication of sub-micrometer scale BZY thin film. [ABSTRACT FROM AUTHOR]

Abstract: Ba0.5Sr0.5TiO3(BST)/Bi1.5Zn1.0Nb1.5O7(BZN) multilayer thin films were prepared on Pt/Ti/SiO2/Si substrates by a sol–gel method. The structures and morphologies of BST/BZN multilayer thin films were analyzed by X-ray diffraction (XRD) and field-emission scanning electron microscope. The XRD results showed that the perovskite BST and the cubic pyrochlore BZN phases can be observed in the multilayer thin films annealed at 700°C and 750°C. The surface of the multilayer thin films annealed at 750°C was smooth and crack-free. The BST/BZN multilayer thin films annealed at 750°C exhibited a medium dielectric constant of around 147, a low loss tangent of 0.0034, and a relative tunability of 12% measured with dc bias field of 580kV/cm at 10kHz. [Copyright &y& Elsevier]

Abstract: Strontium hexaferrite SrFe12O19 thin films have been synthesized on the Si (100) substrate using spin coating sol–gel process. The influence of different citric acid to metal ions (CA/MN) molar ratios of 0.5, 1 and 1.5 on the formation of SrFe12O19 was investigated. Fourier transform infrared analysis and theoretical calculations were conducted to determine and help control the concentration of metal citrates in solution precursors. X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer techniques were also applied to evaluate the composition, microstructure, crystallite size and magnetic properties of the SrFe12O19 thin films. The results showed that single phase strontium hexaferrite thin films with optimum physical properties can be obtained from the solution with the CA/MN molar ratio of 1 after calcination at 800°C. The SrFe12O19 thin films synthesized with the CA/MN molar ratio of 1 exhibited crystallite size of 42nm and isotropically magnetic properties of Ms =267.5kA/m (at 795.8kA/m), Mr =134kA/m, and Hc =341.4kA/m. [Copyright &y& Elsevier]

Abstract: The gel-derived TiO2 and P–TiO2 transparent films coated on fused-SiO2 substrates were prepared using a spin-coating technique. Effects of phosphorus dopants and calcination temperature on crystal structure, crystallite size, microstructure, light transmittance and photocatalytic activity of the films were investigated. By introducing P atoms to Ti–O framework, the growth of anatase crystallites was hindered and the crystal structure of anatase-TiO2 could withstand temperature up to 900°C. The photocatalytic activities of the prepared films were characterized using the characteristic time constant (τ) for the photocatalytic reaction. The titania film with a smaller τ value possesses a higher photocatalytic ability. After exposing to 365-nm UV light for 12h, the P–TiO2 films calcined between 600°C and 900°C can photocatalytically decomposed ≥84mol% of the methylene blue in water with corresponding τ≤7.1h, which were better than the pure TiO2 films prepared at the same calcination temperature. [Copyright &y& Elsevier]

Abstract: Rib channel waveguides were produced with the application of chemical wet etching of the sol-gel derived silica–titania (SiO2–TiO2) waveguide films. The silica–titania films were etched in water solutions of ammonia fluoride. In the etching process, the waveguide films were selectively masked with a photoresist. This paper presents the theoretical analysis of rib channel waveguides as well as the results of experimental research on slab and rib channel waveguides. For slab waveguides the attenuation of 0.15dB/cm was obtained, and for the produced single mode rib channel waveguides, the attenuation of 1.7dB/cm was obtained. [Copyright &y& Elsevier]

Abstract: (Na0.85K0.15)0.5Bi0.5TiO3 (NKBT) thin films derived from different amounts of Na/K excess content were fabricated via an aqueous sol–gel method on a Pt(111)/Ti/SiO2/Si substrate, and the effect of Na/K excess content on the microstructure and electrical properties of the NKBT thin films was investigated. A second phase appears when Na/K excess content is below 20mol%. Appropriated Na/K excess can enhance the polarization and dielectric properties due to compensation of Na/K loss that occurred during heat treatment. The 20mol% excess derived NKBT thin film exhibits the best ferroelectric and dielectric properties with a remnant polarization (Pr) of 13.6μC/cm2, and a coercive field (Ec) of 104.8KV/cm, together with a dielectric constant of 406 and a dissipation factor of 0.064. Similar to the dielectric response change with Na/K excess content, the decreasing concentration of charged defects is the main reason resulting in the increase of the piezoelectric property. The film with a 20mol% excess content exhibited an effective d 33 ⁎ of about 56pm/V. Also, the NKBT with a 20mol% excess content exhibits the lowest current density of 5.6×10−5 A/cm2 at 10V. [Copyright &y& Elsevier]

Abstract: Multilayer lithium tantalate thin films were deposited on Pt–Si [Si(111)/SiO2/TiO2/Pt(111)] substrates by sol–gel process. The films were annealed at different annealing temperatures (300, 450 and 650°C) for 15min. The films are polycrystalline at 650°C and at other annealing conditions below 650°C the films are in amorphous state. The films were characterized using X-ray diffraction, atomic force microscopy (AFM) and Raman spectroscopy. The AFM of images show the formation of nanograins of uniform size (50nm) at 650°C. These polycrystalline films exhibit spontaneous polarization of 1.5μC/cm2 at an application of 100kV/cm. The dielectric constant of multilayer film is very small (6.4 at 10kHz) as compared to that of single crystal. [ABSTRACT FROM AUTHOR]

Abstract: Transparent thin films of Ga-doped ZnO (GZO), with Ga dopant levels that varied from 0 to 7at.%, were deposited onto alkali-free glass substrates by a sol–gel process. Each spin-coated film was preheated at 300°C for 10min, and then annealed at 500°C for 1h under air ambiance. The effects of Ga dopant concentrations on crystallinity levels, microstructures, optical properties, and electrical resistivities of these ZnO thin films were systematically investigated. Photoluminescence spectra of GZO thin films were examined at room temperature. XRD results revealed that the undoped ZnO thin films exhibited a preferred orientation along the (002) plane and that the ZnO thin films doped with Ga showed degraded crystallinity. Experimental results also showed that Ga doping of ZnO thin films could markedly decrease surface roughness, improve transparency in the visible range, and produce finer microstructures than those of undoped ZnO thin films. The most promising films for transparent thin film transistor (TTFT) application produced in this study, were the 3 and 5at.% Ga-doped ZnO thin films, both of which exhibited an average transmittance of 90.6% and an RMS roughness value of about 2.0nm. [ABSTRACT FROM AUTHOR]

Abstract: Lead germanate–silicate (Pb5Ge2.85Si0.15O11) ferroelectric thin films were successfully fabricated on Pt/Ti/SiO2/(100)Si substrates by the sol–gel process. The thin films were fabricated by multi-coating at preheating temperatures of 350 and 450°C. After annealing the thin films at 600°C, the films exhibited c-axis preferred orientation. The degree of c-axis preferred orientation of the thin films preheated at 350°C was higher than that of films preheated at 450°C. Grain growth was influenced by the annealing time. The thin films exhibited a well-saturated ferroelectric P–E hysteresis loop when preheated at 350°C and annealed at 600°C for 1.5h. The values of the remanent polarization (Pr) and the coercive field (Ec) were approximately 2.1μC/cm2 and 100kV/cm, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Silver-doped titanium dioxide thin films were deposited on glass substrates by the sol–gel process. Undoped films and films doped with 1 and 3 mol% Ag were annealed at 100 or 500 °C. The optical and morphological properties of the films were analyzed by optical absorption spectroscopy and scanning electron microscopy. Additionally, the films were evaluated for their ability to degrade methylene blue. It was found that the photocatalytic activity is barely sensitive to silver doping for films annealed at 100 °C, whereas the effect of silver resulted in enhanced photocatalytic activity for films annealed at 500 °C. For the latter annealing temperature, the photocatalytic activity increased with increasing Ag doping concentration. [Copyright &y& Elsevier]

Abstract: This work investigates the preparation, microstructure and thermal/electrical properties of fluorinated polyimide–organosilicate hybrids utilizing acetic acid and ammonia as the catalysts for sol–gel process to grow organosilicate filler particles. Nano-scale organosilicate was observed in the base-catalyzed hybrids, which was ascribed to the relative inertness of base catalysts in promoting the hydrolysis reaction. This postponed the formation of particles and hence smaller particle size. Electrical measurements found that the base-catalyzed hybrids possess lower dielectric constants (κ =2.40 at nominal Si content=0.4 mol) due to the absence of polar groups and formation of silica xerogels with high porosity in the samples. In both hybrids, leakage current densities increase with the increase of Si content. However, leakage current density of base-catalyzed hybrid was higher than that of acid-catalyzed hybrid at the same Si content due to the smaller particle size and highly porous feature of organosilicate embedded in the base-catalyzed hybrids. [Copyright &y& Elsevier]

Abstract: Incorporation of Ag nanocrystal into indium tin oxide films (Ag–ITO) could enhance the conductivity of transparent oxide thus attracts more and more interest. Ag–ITO films were prepared by a modified sol–gel method. The surface structure was investigated by X-ray diffraction, X-ray diffuse scattering, and X-ray photoelectron spectroscope techniques. The results showed that stannous chloride worked well as the reduction agent of silver and ion donor source, resulting in high quality nanocomposite thin films. The embedment of silver nanoparticles decreased the crystallization temperature and inhibited the growth of indium oxide. Ag–ITO films have a hierarchical structure. Furthermore, the nanocomposite films were densified and homogenized through prolonging the thermal duration time. XPS results confirmed that a small amount of silver oxide appeared. [Copyright &y& Elsevier]

Abstract: Undoped and In doped ZnO films have been deposited by sol–gel spin coating method. The effect of indium incorporation on structural and optical properties of ZnO films has been investigated. X-ray diffraction patterns of the films showed the hexagonal wurtzite type polycrystalline structure and that indium incorporation leads to substantial changes in the structural characteristics of ZnO films. The SEM and AFM measurements showed that the surface morphology of the films was affected from the indium incorporation. Optical reflectance and transmittance were recorded with a double beam spectrophotometer with an integrating sphere. The optical band gap of these films was determined. The absorption edge shifted to the lower energy depending on the dopant materials. The optical constants of these films were determined using transmittance and reflectance spectra. [Copyright &y& Elsevier]

Abstract: Praseodymium-substituted bismuth titanate (Bi3.2Pr0.8Ti3O12, BPTO) thin films were successfully deposited on Pt(111)/Ti/SiO2/Si(100) substrates by spin coating with a sol–gel technology and rapid thermal annealing. The effects of annealing atmospheres (vacuum, ambient atmosphere and oxygen) on the growth and properties of thin films were investigated. The results show that the intensity of the (117) diffraction peak of Bi3.2Pr0.8Ti3O12 film annealed in oxygen is stronger than those annealed in ambient atmosphere and vacuum. The XRD spectra demonstrated that a highly (117) orientation could be obtained when the Bi3.2Pr0.8Ti3O12 thin film was annealed in an oxygen-sufficient environment. The BPTO thin films annealed in oxygen atmosphere exhibits the maximum remanent polarization (2P r) of 49 μC/cm2 and a low coercive field (2E c) of 130 kV/cm, fatigue free characteristics up to ≧1011 switching cycles. These results indicate that the BPTO thin film is useful in nonvolatile ferroelectric random access memory applications. [Copyright &y& Elsevier]

Abstract: A kind of ZnO:(La, Eu)Cl nanocomposite thin film phosphor with strong red emission was synthesized by the sol–gel process. X-ray diffraction and scanning electron microscopy characterization indicate that the films were composed of nano-sized grains and a LaOCl phase appeared accompanying with (100) oriented ZnO phase after annealed at 600 °C in oxygen. The photoluminescence properties were investigated by measuring the excitation and emission spectra. These luminescence results suggested that Eu3+ ions could incorporate into the LaOCl lattice and charge transfer occurred between LaOCl phase and Eu3+ ions. La co-doping with Eu-Cl leads to the improvement of the red luminescence of Eu3+ and also suppressed the broad green emission of ZnO host. [Copyright &y& Elsevier]

Abstract: Corona poling is an interesting non-contact poling process for ferroelectric materials which, has in the past, been extensively applied to ferroelectric polymers, but not to other types of ferroelectric materials. Here, it has been investigated as an alternative technique to the conventional direct-contact poling of ferroelectric thin films. Contact-poling and corona poling techniques were applied to highly (001)/(100) oriented lead zirconate titanate thin films of composition 52% Zr, 48% Ti (PZT52/48). Different poling voltages and durations were used to pole the samples, and the effects on the piezoelectric coefficients e 31,f and d 33,f were explored. From the magnitudes of piezoelectric coefficients and suppression of e 31,f relative to d 33,f, it was concluded that corona poling is a more suitable technique for poling PZT52/48 thin films than direct poling, since piezoelectric coefficients were higher and sample damage was less for corona poling when compared with contact-poling. [Copyright &y& Elsevier]

Abstract: Pure and cobalt doped titanium dioxide thin films have been prepared on glass and Si (100) substrates by sol–gel spin coating method. The structural and optical properties of the films as a function of cobalt concentration (up to 15 wt.%) have been systematically studied by Rutherford backscattering spectroscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, optical spectroscopy and spectroscopic ellipsometry methods. Rutherford backscattering studies show the presence of cobalt dopant in the films is almost equal to the precursor stoichiometry. Grazing incidence X-ray diffraction and Raman spectroscopy studies confirm the amorphous phase of the as-deposited films and crystalline anatase phase for the films annealed at 600 °C. The optical spectroscopy measurements show that the films are fully transparent in the visible region and there is a band gap narrowing upon increasing cobalt dopant concentration. The refractive index, band gap (E g) and thickness of the films were determined from spectroscopic ellipsometry measurements. The refractive index of the films was found to increase from 2.2 to 2.7 with the increase in cobalt concentration with a simultaneous decrease of band gap from 3.1 to 2.8, which is favorable for photocatalytic applications. The packing density of the films was calculated by Clausius–Mossotti relation and is found to increase with cobalt concentration. [Copyright &y& Elsevier]

Abstract: The antireflective (AR) properties of Al2O3 thin films with small roughness on soda–lime silica glass substrates were investigated. By immersing porous Al2O3 thin films in hot water, nanocrystals of pseudoboehmite were formed on the film surface. The reflectance of the Al2O3 films treated with hot water for 30 min was less than 0.5% in the wavelength region of 360–620 nm. The Al2O3 films with small roughness resulting from the hot water treatment become denser from their surface to the interface with the substrate, and the refractive index gradient brought by the structure results in excellent AR properties. [Copyright &y& Elsevier]

Abstract: Polycrystalline ferroelectric lead-free Bi0.5Na0.5TiO3 (BNT) thin films have been successfully deposited on Pt/Ti/SiO2/Si substrates by an improved sol–gel process using rapid thermal annealing. Our results indicate that thermal annealing in an oxygen atmosphere after each layer of coating is effective in promoting crystallization of the film at a relatively low temperature of 650 °C. The resulting film is dense and well crystallized in the rhombohedral perovskite phase, and has good electrical and ferroelectric properties. The observed dielectric constant and loss at 100 kHz are 277 and 0.02, respectively, while the observed remanent polarization and coercive field under an alternating current electric field of 1100 kV/cm are 8.3 μC/cm2 and 200 kV/cm, respectively. The BNT based film is expected to be a promising candidate for lead-free piezoelectric applications. [Copyright &y& Elsevier]

Abstract: Organically-modified silicate incorporating various amounts of zirconium precursor was synthesized via a sol–gel route. The material was deposited as thin films on PMMA substrates and densified by UV-curing. Mechanical properties were measured by nanoindentation and data were recorded continuously as a function of the penetration depth during the loading–unloading cycles. Values of hardness and Young modulus were found in the range 340–440 MPa and 4–6 GPa, respectively. It was shown that these values could be tailored by varying the relative amount of zirconium in the layer. The material exhibited a very elastic behaviour that was related to its high degree of cross-linking assessed by infrared spectroscopy. Results were compared with measurements published by various groups on related materials. The mechanical and optical properties of the samples made this class of materials promising as hard coatings for optical applications. [Copyright &y& Elsevier]

Abstract: We report on the properties of Nd-substituted bismuth titanate Bi4− x Nd x Ti3O12 (BNdT) thin films for ferroelectric non-volatile memory applications. The Nd-substituted bismuth titanate thin films fabricated by modified chemical solution deposition technique showed much improved properties compared to pure bismuth titanate. A pyrochlore free crystalline phase was obtained at a low annealing temperature of 640 °C and grain size was found to be considerably increased as the annealing temperature increased. The film properties were found to be strongly dependent on the Nd content and annealing temperatures. The measured dielectric constant of BNdT thin films was in the range 172–130 for Bi4− x Nd x Ti3O12 with x =0.0–0.75. Ferroelectric properties of Nd-substituted bismuth titanate thin films were significantly improved compared to pure bismuth titanate. For example, the observed 2P r and E c for Bi3.25Nd0.75Ti3O12, annealed at 680 °C, were 38 μC/cm2 and 98 kV/cm, respectively. The improved microstructural and ferroelectric properties of BNdT thin films suggest their suitability for high density ferroelectric random access memory applications. [Copyright &y& Elsevier]

Abstract: Transparent conducting coatings of sol–gel ATO (antimony-doped tin oxide) were used to improve surface smoothness of commercial sputter-deposited ITO (indium tin oxide) coatings for application as display electrodes. In order to overcome the deteriorating evaporation-cooling during dip coating, the coating solution was heated moderately to 25 °C thus providing the substrate with the required heat. This way, the surface roughness of the ITO could be reduced with an only 45 nm thick ATO coating to R pv =3.8 nm (R a =0.4 nm) compared to 31 nm (3.8 nm) for the ITO substrate. Another benefit of such additional coating is the possibility to tailor surface properties of the electrodes in wide ranges. This was used to increase the work function of the ITO substrate from initially 4.3–4.6 eV to about 4.8–5.2 eV by the ATO coating. [Copyright &y& Elsevier]

Abstract: ZnO thin films are prepared on glass substrate by sol–gel spin-coating method and the effect of preheating temperature on c-axis preferred orientation and optical properties of the films are investigated. The ZnO thin film that was preheated at 275 °C and post-heated at 650 °C using a sol with Zn concentration of 0.7 mol/l is highly oriented along the (002) plane. The transmittances of ZnO thin films preheated at 200∼300 °C and post-heated at 650 °C are over 85% in visible range and exhibit absorption edges at about 368 nm. The optical band gap energy is evaluated to be 3.24∼3.26 eV. The photoluminescence shows the ultraviolet emission at near band edge and broad green-yellow radiation at 490∼620 nm. The effect of preheating temperature on structural and optical properties of ZnO thin films is discussed. [Copyright &y& Elsevier]

Abstract: Photocatalytically active nanoporous anatase TiO2 films were deposited on glass plates by a sol–gel process conducted in the presence of polyethylene glycol (PEG). The films in different stages of the formation process were characterized by field emission scanning electron microscope, thermogravimetry–differential thermal analysis, ultraviolet–visible (UV–visible) spectroscopy and X-ray diffraction. The as-deposited TiO2/PEG composite films were smooth and dense, and were made nanoporous after the embedded PEG was thermally removed during calcination. The higher the content of PEG the larger was the resultant pore size. There were no cracks in the films common to films prepared in the presence of PEG, and the thermal stability of the films were also improved by the PEG addition. UV–visible spectroscopy showed that the calcination of PEG–TiO2 films also resulted in red shifting the absorption band of TiO2. The films were active in the photooxidation of iodide and methyl orange, and demonstrated an activity increase that scaled with the increase in the PEG content in the sol–gel preparation. [Copyright &y& Elsevier]

Undoped TiO2 and Ag–TiO2 (up to 23 at.% Ag) cermet thin films and polycrystalline powders have been prepared by sol–gel process. Their structure, composition, surface morphology and optical properties have been investigated by X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and ultraviolet–visible spectroscopy (UV–VIS spectroscopy). It has been observed that while Ag does not form a solid solution with TiO2, it promotes the anatase to rutile phase transformation. The transformation temperature decreases from 827 °C for undoped TiO2 to about 650 °C for 23 at.% Ag-doped TiO2. SIMS analyses show that Ag is mostly present on the surface of the films. XPS studies confirm that these Ag are in the Ag0 state. Optical analyses show that with increasing Ag content, the refractive index (n) increases and the optical absorption behavior of the cermet films is modified, but the band gap of the anatase TiO2 is not influenced. [Copyright &y& Elsevier]

SiO2/MC (Methylcellulose) composite materials formed by the sol–gel technique were investigated for optical applications. MC was used as an organic binder to get a thicker film by a single spin-coating process. After spin-coating and placement in air, a uniform single coating layer with a thickness of approximately 900 nm was obtained. The films were annealed in 0.2 bar O2 ambiance under the irradiation of 222 nm excimer UV (ultraviolet) lamps at temperatures from room temperature to 300 °C. The film properties were studied by scanning electron microscopy, thermal gravimetric analysis, Fourier-transform infrared spectroscopy, UV–VIS spectrophotometry, and X-ray photoelectron spectroscopy. Absorption feature approximately 2900 cm−1 in FTIR spectra, corresponding to some organic compounds, was found to disappear after UV annealing at low temperatures, indicating active oxygen species produced by UV light can enhance the removal of the organic compounds in the films. This UV annealing technique can be applicable to other optical and electrical materials. [Copyright &y& Elsevier]

Thin film phosphors with compositions of RP1−xVxO4: A (R=Y, Gd, La; A=Sm3+, Er3+; x=0, 0.5, 1) have been prepared by a Pechini sol–gel process. X-Ray diffraction, atomic force microscopy (AFM), photoluminescence excitation and emission spectra were utilized to characterize the thin film phosphors. The results of XRD showed that a solid solution formed in YVxP1−xO4: A film series from x=0 to x=1 with zircon structure, which also held for GdVO4: A film. However, LaVO4: A film crystallized with a different structure, monazite. AFM study revealed that the phosphor films consisted of homogeneous particles ranging from 90 to 400 nm depending on the compositions. Upon short ultraviolet excitation, the films exhibit the characteristic Sm3+ 4G5/2–6HJ (J=5/2, 7/2, 9/2) emission in the red region and Er3+ 2H11/2, 4S3/2–4I15/2 emission in the green region, respectively. With the increase of x values in YVxP1−xO4: Sm3+ (Er3+) films, the emission intensity of Sm3+ (Er3+) increases due to the increase of energy transfer probability from VO43− to Sm3+ (Er3+). Due to the structural effects, the Sm3+ (Er3+) shows similar spectral properties in YVO4 and GdVO4 films, which are much different from those in LaVO4 film. [Copyright &y& Elsevier]

A room temperature spraying technique was developed for the deposition of transparent conducting sol–gel ATO (antimony doped tin oxide, SnO2:Sb) coatings, based on an 0.2 M solution of SnCl2 in 1-propanol with 5 mol.% SbCl3 and a mixture of 2-isopropoxyethanol and 2-butoxyethanol as additives with a low evaporation rate. The selection of solvents and the adjustment of the evaporation rate are crucial to obtain uniform films and to avoid film defects like wetting problems or an orange peel effect. The ATO coatings were spray deposited manually on complex shaped substrates as well as on large area flat substrates with a size up to 21×30 cm2 by means of an industrial flat spray coater. The resulting ATO coatings are characterised by a thickness of up to 120 nm, a resistivity of approximately 2×10−2 Ω cm and a transmission T>85% in the visible, which is similar to the properties obtained for dip coated films. [Copyright &y& Elsevier]

A modified dip coating process was developed to deposit transparent conducting sol–gel SnO2:Sb (ATO, antimony doped tin oxide) coatings inside tubes and cavities in optical quality. The necessity for this improvement arises from the fact that the conventional dip coating process applied to tubes results in coatings with poor and non-reproducible properties, showing large variations in the thickness, an increased roughness and an island-like morphology. The main reason for this is found in a delayed and restricted solvent evaporation, due to an impediment of a laminar flow and a progressive saturation of the atmosphere inside the tube. By means of an additional exhausting pipe, a forced laminar flow was, therefore, generated inside the tube, which guarantees a fast evaporation and hydrolysis of the sol–gel films by a continuous renewal of the atmosphere. In this way, ATO coatings with an excellent thickness uniformity and a low roughness of Ra≈1 nm could be deposited on borosilicate glass tubes of 300 mm length and inner diameters down to 11 mm. After a heat treatment at temperatures up to 550 °C, single layer coatings exhibit a high optical transmission (T>85%) and a resistance down to 10 kΩ over a length of 22 cm. [Copyright &y& Elsevier]

TiO2 thin films were prepared on NiTi surgical alloy by sol–gel method. The forming process, surface morphology and structure of the films were studied by X-ray diffraction and atomic force microscopy. The results showed that nm-scale TiO2 particles were embedded in the film of 205 nm thickness. The film existed mainly in the form of anatase, and the film was compact and smooth. The electrochemical corrosion measurement indicated that TiO2 thin film, as a protective layer, was effective for improving corrosion resistance of NiTi alloy. Additionally, in vitro blood compatibility of the film and NiTi alloy was evaluated by dynamic clotting time and blood platelets adhesion tests. The results showed that NiTi alloy coated with TiO2 film had improved blood compatibility. [Copyright &y& Elsevier]

Using a sol–gel method, rare earth element europium doped lead zirconate titanate thin films with a pure perovskite structure were obtained. The effects of excess lead and pyrolyzing temperature on the crystalline structure of the thin films were investigated using X-ray diffraction. Their ferroelectric and dielectric properties were determined by P–E loop and impedance measurements. The remnant polarization is 23.5 μC/cm2 and the coercive electric field strength is 5.5 kV/mm. The dielectric constant and the dissipation factor is approximately 950 and 0.07, respectively. [Copyright &y& Elsevier]

The single- and bi-layered nanocrystalline SnO2/TiO2 films are prepared using a sol–gel process and the humidity sensing behaviors of the films are investigated. The films possess the grain size of nanometer order and nanoporous structure. The bilayered films exhibit a better linearity with narrower hysteresis loop in the resistance variation for relative humidity than single layered films. The bilayered SnO2/TiO2 film shows high sensitivity with nearly three orders change in the resistance during the relative humidity variation from 30 to 90%. The humidity sensing behaviors in the single- and bi-layered films are discussed. [Copyright &y& Elsevier]

• Simultaneous sol-gel and step growth polymerization within one procedure. • Aluminium component acting as reactant and catalyst for network formation process. • Multi-layer systems by sol-gel and combustion chemical vapour deposition technique. • Coatings with high barrier effect on polymer films under ambient conditions. • Composite layers are very thin and even have a transparency-enhancing effect. The combustion chemical vapour deposition (CCVD) technology was used to generate thin inorganic silica-coatings on polyethylene terephthalate (PET) films. These SiO x base layers were combined with flexibly configurable hybrid sol-gel layers to create multi-layer systems with improved property profiles, such as high gas barrier against oxygen or water vapour. The inorganic-organic sol-gel hybrid layer is produced by the simultaneous step growth polymerization of three reactants: 3-aminopropyltriethoxysilane, 4,4′-methylene- bis (N,N-diglycidylaniline) and aluminium-tri- sec -butoxide. The controlled sol-gel process allows simultaneous covalent bond formation between the silica, alumina and epoxy resin containing components, which is crucial for the target property of the hybrid material layer. The so synthesized ternary hybrid material layer has a significantly improved gas barrier effect as well as a higher light transmittance compared to the unmodified coating. For the reduction of the Oxygen Transmission Rate (OTR), the exact adjustment of the Al component proved to be the main influencing factor. The combination of CCVD and sol-gel technology is very well suited to create composite systems whose gas barrier properties are sufficient for use in the food and pharmaceutical packaging sector, even for sensitive content. These coatings have very low values for the OTR which range up to 10−1 cm3 / (m2 d bar) as well as adequate transmission rates for water vapour which range up to 100 g / (m2 d). In addition, these composite layers can also ensure light transmission. By applying a coating system based on three single layers, the initial transmittance of the PET film could be exceeded by 1% up to 87%. Thus, composite layers even with a total thickness of about 400 nm, which were completely generated under ambient conditions, can build up a barrier effect on PET films. [ABSTRACT FROM AUTHOR]