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1.
SrTiO 3 powder has been prepared from Sr-oxalate and TiO 2 precursors, instead of using titanyl-oxalate. Sr-oxalate was precipitated from nitrate solution onto the surface of suspended TiO 2 powders. Crystallization of SrTiO 3 from the precursor was investigated by TGA, DTA and XRD analysis. It is evident that precursor, upon heating, dehydrates in two stages, may be due to the presence of two different types of Sr-oxalate hydrates. Dehydrated precursor then decomposes into SrCO 3 and TiO 2 mixture. Decomposition of SrCO 3 and simultaneous SrTiO 3 formation occur at much lower temperature, from 800 °C onwards, due to the fine particle size of the SrCO 3 and presence of acidic TiO 2 in the mixture. The precursor completely transforms into SrTiO 3 at 1100 °C. About 90 nm size SrTiO 3 crystallites are produced at 1100 °C/1 h, due to the lower calcination temperature and better homogeneity of the precursor. 相似文献
2.
Anatase titanium dioxide (TiO 2) thin films with high photocatalytic activity have been prepared with deposition rates as high as 16 nm/min by a newly developed vacuum arc plasma evaporation (VAPE) method using sintered TiO 2 pellets as the source material. Highly transparent TiO 2 thin films prepared at substrate temperatures from room temperature to 400 °C exhibited photocatalytic activity, regardless whether oxygen (O 2) gas was introduced during the VAPE deposition. The highest photocatalytic activity and photo-induced hydrophilicity were obtained in anatase TiO 2 thin films prepared at 300 °C, which correlated to the best crystallinity of the films, as evidenced from X-ray diffraction. In addition, a transparent and conductive anatase TiO 2 thin film with a resistivity of 2.6 × 10 − 1 Ω cm was prepared at a substrate temperature of 400 °C without the introduction of O 2 gas. 相似文献
3.
We demonstrate that the atomic structures, electronic states, and bonding nature of the interface between SrTiO 3 substrate and anatase TiO 2 thin films could be related and technologically manipulated at the atomic level. Applying advanced transmission electron
microscopy, the grown anatase TiO 2 thin films are found to make a clean and direct contact to the SrTiO 3 substrates in an epitaxial, coherent, and atomically abrupt way. The atomic-resolution microscopic images reveal that the
interface comprises SrO-terminated SrTiO 3 and Ti-terminated TiO 2 with the interfacial Ti of TiO 2 sitting above the hollow site, which is confirmed theoretically to be the most energetically favorable. Quantitatively, the
first-principles calculations predict that the oxygen sublattice at the interface undergoes a notable reconstruction, i.e.,
the interfacial O atoms of TiO 2 are displaced largely toward the SrO plane of the SrTiO 3, flattening the originally zigzag TiO 2 atomic chains. Consequently, the interfacial layers suffer a remarkable modification in the charge accumulation and also
a deviation in the density of states from their bulk counterparts, indicating that the substrate can have an impact on the
deposited thin films electronically. Using several analytic methods, the SrTiO 3/TiO 2 interface is found to take on a metallic nature, and the interfacial bonding is determined to be of a mixed covalent and
ionic character. This combined experimental and theoretical investigation gains insight into the complex atomic and electronic
structures of the buried interface, which are fundamental for relating the atomic-scale structures to their properties on
a quantum level. 相似文献
4.
Nano-sized homogeneously distributed TiO 2-20, -40, -60 wt.% SrO composite powders were successfully synthesized by a sol-gel method. The as-received amorphous TiO 2—20 wt.% SrO composite powders were crystallized with anatase TiO 2 at around 750 °C. As calcination temperatures increased, the anatase TiO 2 crystalline phase was transformed to rutile TiO 2 at about 900 °C, whereas nano-sized, squarish SrTiO 3 phase was detected. The peaks obtained after calcining at 1050 °C mainly exhibited the rutile TiO 2 and SrTiO 3 phases. However, a small number of SrO 2 peaks were also detected. For the comparison of photocatalytic activity depending on light sources, TiO 2-SrO composite powders were tested in phenol degradation. TiO 2-60 wt.% SrO composite powder showed good visible light photoactivity for the photo-oxidation of phenol. 相似文献
5.
SrSnO 3 thin films were prepared by pulsed laser deposition on amorphous silica and single crystal substrates of R-sapphire, (100)LaAlO 3 and (100)SrTiO 3. High quality epitaxial (100) oriented films were obtained on LaAlO 3 and SrTiO 3 while a texture was revealed for films on sapphire deposited at the same deposition temperature of 700 °C. Amorphous films were obtained on silica but a post annealing at 800 °C induced crystallization with a random orientation. The screening of deposition temperature showed epitaxial features on SrTiO 3 from 650 °C while no crystallization was observed at 600 °C. The influence of substrate and deposition temperature was confirmed by Scanning Electron Microscopy and Atomic Force Microscopy observations. 相似文献
6.
BaTiO 3 films were epitaxially grown on SrTiO 3 (001) substrates buffered with SrRuO 3 films as bottom electrode by pulsed laser deposition under high oxygen pressure of 30 Pa. The quality of the BaTiO 3/SrRuO 3/SrTiO 3 multilayer films was analyzed by means of X-ray diffraction, atomic force microscopy and transmission electron microscopy. BaTiO 3 films were found to be highly c-axis-oriented tetragonal phase with c/a = 1.002. The dielectric constant first increased with increasing temperature, and showed a peak at the Curie temperature of about 356 K. The films had well-saturated hysteresis loops with a remnant polarization of 7.3 μC/cm 2 and a coercive field of 29.5 kV/cm at room temperature. 相似文献
7.
Nano-crystalline TiO 2 thin films were synthesized by using sol-gel and spin-coating techniques on glass substrates for photo-catalytic applications. Prior to deposition, a TiO 2 colloidal suspension was synthesized by microwave-induced thermal hydrolysis of the titanium tetrachloride aqueous solution. In this study, the deposited TiO 2 coating with a grain size of 13 ± 2 nm was uniform without aggregation. Co ion implantation into the as-calcined TiO 2 thin films was conducted with fluences of 1 × 10 15-1 × 10 16 doses/cm 2 at 40 keV. In addition to the emission of TiO 2, the photoluminescence study showed the presence of another Co-related optical center at 405 nm in the Co-implanted TiO 2 thin films. Due to the strong capability of forming impurity compounds between the energetic cobalt ions and TiO 2, the photoluminescence emission and UV-Vis absorption efficiencies were improved. 相似文献
8.
Multiferroic DyFeO 3 thin films deposited on (001) Nb-doped SrTiO 3 (NSTO) substrates are prepared by pulsed laser deposition. We demonstrate the epitaxial deposition of DyFeO 3 thin films on the substrates with the DyFeO 3(001)//NSTO(001) out-of-plane and DyFeO 3[100]//NSTO[110] in-plane epitaxial relationship. In addition, the weak ferromagnetism and significant magnetodielectric coupling effect at low temperature are revealed. It is indicated that the DyFeO 3 thin films have very different properties from the DyFeO 3 single crystals in term of multiferroicity. 相似文献
9.
Lead-free piezoelectric thin films of NaNbO 3-BaTiO 3 were fabricated on Pt/TiO x/SiO 2/Si substrates by chemical solution deposition. Perovskite NaNbO 3-BaTiO 3 single-phase thin films with improved leakage-current and ferroelectric properties were prepared at 650 °C by doping with a small amount of Mn. The 1.0 and 3.0 mol% Mn-doped 0.95NaNbO 3-0.05BaTiO 3 thin films showed slim ferroelectric P- E hysteresis and field-induced strain loops at room temperature. The 1.0 and 3.0 mol% Mn-doped 0.95NaNbO 3-0.05BaTiO 3 films showed remanent polarization values of 6.3 and 6.2 μC/cm 2, and coercive field of 41 and 55 kV/cm, respectively. From the slope of the field-induced strain loop, the effective piezoelectric coefficient ( d33) was found to be 40-60 pm/V. 相似文献
10.
Dielectric SrTiO 3 thin films were deposited on LaAlO 3 and Si substrates using laser molecular beam epitaxy. The correlations between the deposition parameters of SrTiO 3 thin films, their structural characteristics, and dielectric properties were studied. The conditions for achieving epitaxial SrTiO 3 thin films were found to be limited to deposition conditions such as deposition temperature. We show that the SrTiO 3 films with single (110) orientation can be grown directly on Si substrates. The nature of epitaxial growth and interfacial structures of the grown films were examined by various techniques, such as Laue diffraction and X-ray photoelectron spectroscopy. The SrTiO 3/Si interface was found to be epitaxially crystallized without any SiO 2 layer. Furthermore, we have measured dielectric properties of the grown SrTiO 3 multilayer suitable for tunable microwave device. A large tunability of 74.7%, comparable to that of SrTiO 3 single-crystal, was observed at cryogenic temperatures. Such STO thin films will be very promising for the development of microelectronic device applications. 相似文献
11.
This work reports on the synthesis and the structural and optical characterization of beta barium borate (β-BBO) thin films containing 4, 8 and 16 mol% of titanium oxide (TiO 2) deposited on fused silica and silicon (0 0 1) substrates using the polymeric precursor method. The thin films were characterized by X-ray diffraction, Raman spectroscopy, atomic force microscopy and scanning electron microscopy techniques. The optical transmission spectra of the thin films were measured over a wavelength range of 800-200 nm. A decrease was observed in the band gap energy as the TiO 2 content was raised to 16 mol%. Only the β-BBO phase with a preferential orientation in the (0 0 l) direction was obtained in the sample containing 4 mol% of TiO 2 and crystallized at 650 °C for 2 h. 相似文献
12.
The TiO 2 thin films doped by Ni uniformly and non-uniformly were prepared on glass substrate from an aqueous solution of ammonium
hexa-fluoro titanate and NiF 2 by liquid phase deposition technique. The addition of boric acid as an F
− scavenger will shift the equilibrium to one side and thereby deposition of the film is progressed. The rate of the reaction
and the nature of deposition depend on growing time and temperature. The resultant films were characterized by XRD, EDAX,
UV and SEM. The result shows that the deposited films have amorphous background, which becomes crystalline at 500°C. The EDAX
data confirms the existence of Ni atoms in TiO 2 matrix. XRD analysis reveals the peaks corresponding to Ni but no peak of crystalline NiO was found. The transmittance spectra
of Ni uniformly and non-uniformly doped TiO 2 thin films show ‘blue shift and red shift’, respectively. Ni-doped TiO 2 thin films can be used as photocatalyst for the photodegradation of methyl orange dye. It was found that, organic dye undergoes
degradation efficiently in presence of non-uniformly Ni-doped TiO 2 thin films when compared to uniformly doped films and pure TiO 2 films under visible light. The photocatalytic activity increases with increase in the concentration of Ni in case of nonuniformly
doped thin films but decreases with the concentration when uniformly doped thin films were used. 相似文献
13.
A sol-gel dip coating technique was used to fabricate TiO 2/SnO 2 nano composite thin films on soda-lime glass. The solutions of SnO 2 and TiO 2 were mixed with different molar ratios of SnO 2:TiO 2 as 0, 3, 4, 6, 8, 9, 10.5, 13, 15, 19.5, 25 and 28 mol.% then the films were prepared by dip coating of the glasses. The effects of SnO 2 concentration, number of coating cycles and annealing temperature on the hydrophilicity of films were studied using contact angle measurement. The films were characterized by means of scanning electron microscopy, X-ray diffraction and atomic force microscopy measurements. The nano composite thin films fabricated with 8 mol.% of SnO 2, four dip coating cycles and annealing temperature of 500 °C showed super-hydrophilicity. 相似文献
14.
A method of ion plasma deposition is proposed for obtaining thin multicomponent films with continuously graded composition in depth of the film. The desired composition–depth profile is obtained by varying the working gas pressure during deposition in the presence of an additional adsorbing screen in the drift space between a sputtered target and substrate. Efficiency of the proposed method is confirmed by Monte Carlo simulation of the deposition of thin films of Ba
x
Sr1–x
TiO3 (BSTO) solid solution. It is demonstrated that, during sputtering of a Ba0.3Sr0.7TiO3 target, the parameter of composition stoichiometry in the growing BSTO film varies in the interval of x = 0.3–0.65 when the gas pressure is changed within 2–60 Pa. 相似文献
15.
KNbO 3 thin films were deposited on SrTiO 3 substrates by pulsed laser deposition. The X-ray diffraction patterns highlight an epitaxial growth according to the (011) orientation. This epitaxial growth was then confirmed by Electron Channeling Pattern. In agreement with the structural characteristics the dense microstructure consists in regular and ordered grains. Dielectric measurements were performed in the 20 Hz to 1 MHz frequency range on a KNbO 3 thin film grown on 2 at.% Nb doped (100)SrTiO 3 substrate in a large range of temperature in order to investigate the paraelectric-ferroelectric transition. Measurements at room temperature revealed a dielectric constant of 450 at 10 kHz and a minimum value of the loss tangent of 0.075 at 100 kHz. Dielectric study in the 20-600 °C temperature range showed a maximum of permittivity at the Curie temperature Tc = 410 °C and evidenced a “progressive” first-order phase transition, different from the classical “diffuse” transition. 相似文献
16.
(Cu,C)-Ba-O thin films have been epitaxially grown on (100) SrTiO 3 at 500 °C by pulsed laser deposition. Their crystallinity and transport properties have been investigated in order to clarify dominate deposition parameters for carbon-incorporation and superconductivity. The present study has revealed that the growth rate positively correlates with CO 3 content and superconducting properties. In addition, the results suggest that suppression of the radiation damage from energetic particles during deposition is an important factor in obtaining a high and sharp superconducting transition temperature. The work has shown that process parameters can be optimized for growth rate, CO 3 content and minimal radiation damage allowing a superconducting onset temperature of 50 K and zero resistance temperature above 40 K to be realized. 相似文献
17.
BiFeO 3 thin films were grown on (001) SrTiO 3 and (001) ZrO 2(Y 2O 3) substrates by single source metalorganic chemical vapor deposition in the temperature range T = 500 ÷ 800 °C using Fe(thd) 3 and Bi(C 6H 5) 3 as volatile precursors. X-ray diffraction analysis shows cube-on-cube epitaxial growth of BiFeO 3 on (001) SrTiO 3. The strongly reduced bismuth transfer into the film due to the high thermal stability of Bi(C 6H 5) 3 was counterbalanced by the increase of the total pressure as well as of the residence time of the precursor flow in the reactor; the Bi/Fe ratio in the film thus becomes close to that in the precursor mixture. Optical second harmonic generation measurements have evidenced the ferroelectric ordering in BiFeO 3 films and the apparent decrease of the Curie temperature of the strained films as compared to BiFeO 3 single crystal. 相似文献
18.
Microstructure and hydrophilicity of nano-titanium dioxide (TiO 2) thin films, deposited by radio frequency magnetron sputtering, annealed at different temperatures, were studied by field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and water contact angle methods. It is found that the crystal phase transforms from amorphous to rutile structure with increase of annealing temperature from room temperature to 800 °C. It is also indicated that the organic contaminants on the surface of the films can be removed and the oxygen vacancies can be reduced by the annealing treatment. Annealed at the temperature below 300 °C, amorphous TiO 2 thin films show rather poor hydrophilicity, and annealed at the temperature range from 400 to 650 °C, the super hydrophilicity anatase of TiO 2 thin films can be observed. However, when the annealing temperature reaches 800 °C, the hydrophilicity of the films declines mainly derived from the appearance of rutile. 相似文献
19.
Pure SrRuO 3 (SRO) thin films and SRO thin films containing the extra metallic phases Ru, RuO 2 and Sr 3Ru 2O 7 were deposited by MOCVD on (0 0 1) SrTiO 3 substrates under different conditions (Ru/Sr and Ar/O 2 ratio in the gas phase, substrate temperature, supersaturation). The single-phase compressively-strained SRO film is of high structural quality and shows a ferromagnetic transition at a suppressed Curie temperature ( Tc) of about 142 K and low electrical resistivity (230 μΩ cm). Under certain deposition conditions Ru and RuO 2 extra phases form leading to a reduced room temperature resistivity of 100 μΩ cm. On the other hand, the presence of Sr 3Ru 2O 7 increases the resistivity to 385 μΩ cm. We have observed that the existence of the extra phases caused a slight shift of Tc towards the bulk value, while relaxation of the lattice strain resulted in increase of Tc to 160 K. The deviation from the stoichiometric composition in films with extra phases is also confirmed by the residual electrical resistivity ratio. On the other hand, the pure SRO films, the compressively strained and the plastically relaxed exhibit a stoichiometric ratio. 相似文献
20.
We have studied the structural and optical properties of thin films of TiO 2, doped with 5% ZrO 2 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 TiO 2, doped with 5% ZrO 2, 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 TiO 2 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). 相似文献
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