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1.
In 2O 3 thin films have been prepared from commercially available pure In 2O 3 powders by high vacuum thermal evaporation (HVTE) and from indium iso-propoxide solutions by sol-gel techniques (SG). The films have been deposited on sapphire substrates provided with platinum interdigital sputtered electrodes. The as-deposited HVTE and SG films have been annealed at 500°C for 24 and 1 h, respectively. The film morphology, crystalline phase and chemical composition have been characterised by SEM, glancing angle XRD and XPS techniques. After annealing at 500°C the films’ microstructure turns from amorphous to crystalline with the development of highly crystalline cubic In 2O 3−x (JCPDS card 6-0416). XPS characterisation has revealed the formation of stoichiometric In 2O 3 (HVTE) and nearly stoichiometric In 2O 3−x (SG) after annealing. SEM characterisation has highlighted substantial morphological differences between the SG (highly porous microstructure) and HVTE (denser) films. All the films show the highest sensitivity to NO 2 gas (0.7–7 ppm concentration range), at 250°C working temperature. At this temperature and 0.7 ppm NO 2 the calculated sensitivities ( S= Rg/ Ra) yield S=10 and S=7 for SG and HVTE, respectively. No cross sensitivity have been found by exposing the In 2O 3 films to CO and CH 4. Negligible H 2O cross has resulted in the 40–80% relative humidity range, as well as to 1 ppm Cl 2 and 10 ppm NO. Only 1000 ppm C 2H 5OH has resulted to have a significant cross to the NO 2 response. 相似文献
2.
An all alkoxide based sol–gel route was investigated for preparation of epitaxial La 0.5Sr 0.5CoO 3 (LSCO) films on 100 SrTiO 3 (STO) substrates. Films with 20–30 to 80–100 nm thickness were prepared by spin-coating 0.2–0.6 M (metal) solutions on the STO substrates and heat treatment to 800 °C at 2 °C min − 1, 30 min, in air. The films were epitaxial with a cube-on-cube alignment and the LSCO cell was strained to match the STO substrate of 3.905 Å closely; a and b = 3.894 Å and 3.897 Å for the 20–30 and 80–100 nm films, respectively. The c-axis was compressed to 3.789 Å and 3.782 Å for the 20–30 and 80–100 nm films, respectively, which resulted in an almost unchanged cell volume as compared to polycrystalline film and nano-phase powders prepared in the same way. The SEM study showed mainly very smooth, featureless surfaces, but also some defects. A film prepared in the same way on an -Al 2O 3 substrate was dense and polycrystalline with crystallite sizes in the range 10–50 nm and gave cubic cell dimensions of ac = 3.825 Å. The conductivity of the ca 30–40 nm thick polycrystalline film was 1.7 mΩcm, while the epitaxial 80–100 nm film had a conductivity of around 1.9 mΩcm. 相似文献
3.
Hydrogen-radical durability of TiO 2 thin films has been investigated under conditions for preparing Si thin film solar cells by catalytic chemical vapor deposition method. It is found that the composition and the optical transmittance of TiO 2 films are almost the same before and after hydrogen-radical exposures with a filament temperature at approximately 1700 °C and a H 2 pressure of approximately 133 Pa. The durability of TiO 2 film has also been observed even under the condition with higher hydrogen-radical density under a filament temperature at approximately 1900 °C, in which SnO 2 and ZnO are easily deoxidized. The application of TiO 2 film as a protecting material of transparent conducting oxide film for Si thin film solar cells are discussed by the hydrogen-radical durability and fundamental properties of TiO 2 thin film. 相似文献
4.
The properties of sol–gel derived CeTi 2O 6 thin films deposited using a solution of cerium chloride heptahydrate and titanium propoxide in ethanol are discussed. The effect of annealing temperature on structural, optical, photoluminescence, photocatalysis and electrochemical characteristics has been examined. Lowest annealing temperature for the formation of crystalline CeTi 2O 6 phase in these samples is identified as 580 °C. The optical transmittance of the films is observed to be independent of the annealing temperature. The optical energy bandgap of the 600 °C annealed film for indirect transition is influenced by the presence of anatase phase of TiO 2 in its structure. Fourier transform infrared spectroscopy investigations have evidenced increased bond strength of the Ti–O–Ti network in the films as a function of annealing temperature. The photoluminescence intensity of the films has shown dependence on the annealing temperature with the films fired at 450 °C exhibiting the maximum photoluminescence activity. The decomposition of methyl orange and eosin (yellow) under UV–visible light irradiation in the presence of crystalline CeTi 2O 6 films shows the presence of photoactivity in these films. The photocatalytic response of CeTi 2O 6 films is found to be superior to the TiO 2 films. In comparison to crystalline films, the amorphous films have shown superior electrochemical characteristics. The 500 °C annealed amorphous films have exhibited the most appropriate properties for incorporation in electrochromic devices comprising tungsten oxide as the primary electrochromic electrode. 相似文献
5.
(100)-oriented 0.462Pb(Zn 1/3Nb 2/3)O 3–0.308Pb(Mg 1/3Nb 2/3)O 3–0.23PbTiO 3 (PZN-PMN-PT) perovskite ferroelectric thin films were prepared on La 0.7Sr 0.3MnO 3/LaAlO 3 (LSMO/LAO) substrate via a chemical solution deposition route. The perovskite LSMO electrode was found to effectively suppress the pyrochlore phase while promote the growth of the perovskite phase in the PZN-PMN-PT film. The film annealed at 700 °C exhibited a high dielectric constant of 2130 at 1 kHz, a remnant polarization, 2 Pr, of 29.8 μC/cm 2, and a low leakage current density of 7.2 × 10 − 7 A/cm 2 at an applied field of 200 kV/cm. The ferroelectric polarization was fatigue-free at least up to 10 10 cycles. Piezoelectric coefficient, d33, of 48 pm/V was also demonstrated. The results showed that much superior properties could be achieved with the PZN-PMN-PT thin films on the solution derived LSMO electrode than on Pt electrode by sputtering. 相似文献
6.
Thick film H 2 sensors were fabricated using SnO 2 loaded with Ag 2O and PdO x. The composition that gave highest sensitivity for H 2 was in the wt.% ratio of SnO 2:Ag 2O:PdO x as 93:5:2. The nano-crystalline powders of SnO 2–Ag 2O–PdO x composites synthesized by sol–gel method were screen printed on alumina substrates. Fabricated sensors were tested against gases like H 2, CH 4, C 3H 8, C 2H 5OH and SO 2. The composite material was found sensitive against H 2 at the working temperature 125 °C, with minor interference of other gases. H 2 gas as low as 100 ppm can be detected by the present fabricated sensors. It was found that the sensors based on SnO 2–Ag 2O–PdO x nanocrystalline system exhibited high performance, high selectivity and very short response time to H 2 at ppm level. These characteristics make the sensor to be a promising candidate for detecting low concentrations of H 2. 相似文献
7.
Thin films of SrBi 4Ti 4O 15 (SBTi), a prototype of the Bi-layered-ferroelectric oxide family, were obtained by a soft chemical method and crystallized in a domestic microwave oven. For comparison, films were also crystallized in a conventional method at 700 °C for 2 h. Structural and morphological characterization of the SBTi thin films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. Using platinum coated silicon substrates, the ferroelectric properties of the films were determined. Remanent polarization P r and a coercive field E c values of 5.1 μC/cm 2 and 135 kV/cm for the film thermally treated in the microwave oven and 5.4 μC/cm 2 and 85 kV/cm for the film thermally treated in conventional furnace were found. The films thermally treated in the conventional furnace exhibited excellent fatigue-free characteristics up to 10 10 switching cycles indicating that SBTi thin films are a promising material for use in non-volatile memories. 相似文献
8.
HfO 2 thin films with columnar microstructure were deposited directly on ZnS substrates by electron beam evaporation process. SiO 2 thin films, deposited by reactive magnetron sputtering, were used as buffer layers, HfO 2 thin films of granular microstructure were obtained on SiO 2 interlayer by this process. X-ray diffraction patterns demonstrate that the as-deposited HfO 2 films are in an amorphous-like state with small amount of crystalline phase while the HfO 2 films annealed at 450 °C in O 2 for 30 min and in Ar for 150 min underwent a phase transformation from amorphous-like to monoclinic phase. Antireflection effect in certain infrared wave band, such as 3–6 μm, 4–12 μm, 4–8 μm and 3–10 μm, can be observed, which was dependent on the thickness of thin films. The cross-sectional images of HfO 2 films, obtained by field emission scanning electron microscopy, revealed that there was no distinct morphological change upon annealing. 相似文献
9.
Thirty to a hundred-nm thick epitaxial CeO 2 layers are grown on YSZ (100), (110) and (111) surfaces of yttria-stabilized ZrO 2 (YSZ) by electron beam evaporation of Ce in oxygen at reduced pressure. Their growth, structure and thermal stability are studied with several bulk and surface sensitive techniques including Rutherford backscattering spectrometry, cross-sectional high resolution electron microscopy, low energy electron diffraction and low energy reflection electron microscopy. Excellent epitaxy is obtained on all YSZ surfaces at a growth temperature of 750 K. The surfaces of films grown on (111)-oriented substrates are flat, whereas those on the other substrates are faceted into small (111) planes. The grain sizes in the films are in the 10 nm range and smaller. 相似文献
10.
Fluidized chemical vapor deposition (FCVD) technology was developed for coating SnO 2 thin film on Al 2O 3 ultrafine particles. TEM and HREM analysis found that SnO 2 films with different structures were deposited by controlling the coating temperature, reactant concentration, etc. Nanocrystalline SnO 2 film was coated at 573.15 K by gas phase reaction of SnCl 4 with H 2O. EPMA and EDS studies indicated that the distribution of SnO 2 inner and outer of the agglomerates was uniform. Nucleation and film deposition were coexisted mechanism during the FCVD coating process. The fraction of SnO 2 in the composite particles increased with increasing coating temperature, SnCl 4 concentration, and coating time. The mass fraction of SnO 2 in the composite particles increased strongly with the ratio of P H2O and P SnCl4 at low mole ratio of H 2O with SnCl 4, but increased little under the conditions of excess H 2O with respect to SnCl 4. 相似文献
11.
Undoped and Pd-doped SnO 2 films were deposited under various conditions for the investigation of the effect of Pd doping, porosity, and thickness on their H 2 gas sensing properties. The temperature of the substrate and the pressure of the discharge gas were varied. All films formed were composed of columns with thicknesses between 20 and 30 nm. The film density decreased as the discharge gas pressure increased and the substrate temperature decreased. It showed values between 4.2×10 3 and 7.0×10 3 kg/m 3 depending on the deposition condition. Low film density and Pd doping resulted in high sensitivity and fast response. The largest sensitivity was observed for a Pd-doped film with a low density of 4.7×10 3 kg/m 3 and a thickness of 20 nm. 相似文献
12.
Pulsed laser deposited nanocrystalline V 2O 5 thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and optical spectroscopy. The films were deposited on amorphous glass substrates, keeping the O 2 partial pressure at 13.33 Pa and the substrate temperature at 220 °C. The characteristics of the films were changed by varying the laser fluence and repetition rate. XRD revealed that films are nanocrystalline with an orthorhombic structure. XPS shows the sub-stoichiometry of the films, that generally relies on the fact that during the formation process of V 2O 5 films, lower valence oxides are also created. From the HRTEM images, we observed the size evolution and distribution characteristics of the clusters in the function of the laser fluence. From the spectral transmittance we determined the absorption edge using the Tauc plot. Calculation of the Bohr radius for V 2O 5 is also reported. 相似文献
13.
Gallium oxide thin films were prepared by thermal evaporation and deposition of Ga 2O 3 on NaCl(001) cleavage planes at varying substrate temperatures, oxygen pressures and deposition rates. The structure of the so-prepared thin films was checked by Transmission Electron Microscopy and Selected Area Diffraction and also characterized by X-ray Photoelectron Spectroscopy and Atomic Force Microscopy, both in the as-deposited state and after different oxidative and reductive treatments. The substrate temperature proved to be most crucial for the structure of the gallium oxide films, ranging from low-contrast amorphous structures at low substrate temperatures (298 K) to nanosphere structures at higher temperatures (580 K). The stability of the films was found to be mainly determined by the interaction of substrate temperature and deposition rate. Crystalline β-Ga 2O 3 structures were obtained after oxidative, reductive and annealing treatments at and beyond 773 K suggesting that the crystallization is mainly a thermal annealing effect. 相似文献
14.
This work reports on the effect of post-deposition rapid thermal annealing on the structural and electrical properties of deposited TiB 2 thin films. The TiB 2 thin films, thicknesses from 9 to 450 nm, were deposited by e-beam evaporation on high resistivity and thermally oxidized silicon wafers. The resistivity of as-deposited films varied from 1820 μΩ cm for the thinnest film to 267 μΩ cm for thicknesses greater than 100 nm. In the thickness range from 100 to 450 nm, the resistivity of TiB 2 films has a constant value of 267 μΩ cm. A rapid thermal annealing (RTA) technique has been used to reduce the resistivity of deposited films. During vacuum annealing at 7 × 10−3 Pa, the film resistivity decreases from 267 μΩ cm at 200 °C to 16 μΩ cm at 1200 °C. Heating cycles during RTA were a sequence of 10 s. According to scanning tunneling microscopy analysis, the decrease in resistivity may be attributed to a grain growth through polycrystalline recrystallization, as well as to an increase in film density. The grain size and mean surface roughness of annealed films increase with annealing temperature. At the same time, the conductivity of the annealed samples increases linearly with grain size. The obtained results show that RTA technique has a great potential for low resistivity TiB2 formation. 相似文献
15.
Using a Zn 3In 2O 6 target, indium-zinc oxide films were prepared by pulsed laser deposition. The influence of the substrate deposition temperature and the oxygen pressure on the structure, optical and electrical properties were studied. Crystalline films are obtained for substrate temperatures above 200°C. At the optimum substrate deposition temperature of 500°C and the optimum oxygen pressure of 10 −3 mbar, both conditions that indeed lead to the highest conductivity, Zn 3In 2O 6 films exhibit a transparency of 85% in the visible region and a conductivity of 1000 S/cm. Depositions carried out in oxygen and reducing gas, 93% Ar/7% H 2, result in large discrepancies between the target stoichiometry and the film composition. The Zn/In (at.%) ratio of 1.5 is only preserved for oxygen pressures of 10 −2–10 −3 mbar and a 93% Ar/7% H 2 pressure of 10 −2 mbar. The optical properties are basically not affected by the type of atmosphere used during the film deposition, unlike the conductivity which significantly increases from 80 to 1400 S/cm for a film deposited in 10 −2 mbar of O 2 and in 93% Ar/7% H 2, respectively. 相似文献
16.
Hf(OCH 2CH 2NMe 2) 4, [Hf(dmae) 4] (dmae=dimethylaminoethoxide) was synthesized and used as a chemical vapor deposition precursor for depositing Hf oxide (HfO 2). Hf(dmae) 4 is a liquid at room temperature and has a moderate vapor pressure (4.5 Torr at 80 °C). It was found that HfO 2 film could be deposited as low as 150 °C with carbon level not detected by X-ray photoelectron spectroscopy. As deposited film was amorphous but when the deposition temperature was raised to 400 °C, X-ray diffraction pattern showed that the film was polycrystalline with weak peak of monoclinic (020). Scanning electron microscope analysis indicated that the grain size was not significantly changed with the increase of the annealing temperature. Capacitance–voltage measurement showed that with the increase of annealing temperature, the effective dielectric constant was increased, but above 900 °C, the effective dielectric constant was decreased due to the formation of interface oxide. For 500 Å thin film, the dielectric constant of HfO 2 film annealed at 800 °C was 20.1 and the current–voltage measurements showed that the leakage current density of the HfO 2 thin film annealed at 800 °C was 2.2×10 −6 A/cm 2 at 5 V. 相似文献
17.
Transparent conducting fluorine-doped tin oxide (SnO 2:F) films have been deposited on glass substrates by pulsed laser deposition. The structural, electrical and optical properties of the SnO 2:F films have been investigated as a function of F-doping level and substrate deposition temperature. The optimum target composition for high conductivity was found to be 10 wt.% SnF 2 + 90 wt.% SnO 2. Under optimized deposition conditions ( Ts = 300 °C, and 7.33 Pa of O 2), electrical resistivity of 5 × 10 − 4 Ω-cm, sheet resistance of 12.5 Ω/□, average optical transmittance of 87% in the visible range, and optical band-gap of 4.25 eV were obtained for 400 nm thick SnO 2:F films. Atomic force microscopy measurements for these SnO 2:F films indicated that their root-mean-square surface roughness ( 6 Å) was superior to that of commercially available chemical vapor deposited SnO 2:F films ( 85 Å). 相似文献
18.
Atmospheric pressure chemical vapour deposition of tin monoselenide and tin diselenide films on glass substrate was achieved by reaction of diethyl selenide with tin tetrachloride at 350–650 °C. X-ray diffraction showed that all the films were crystalline and matched the reported pattern for SnSe and/or SnSe 2. Wavelength dispersive analysis by X-rays show a variable Sn:Se ratio from 1:1 to 1:2 depending on conditions. The deposition temperature, flow rates and position on the substrate determined whether mixed SnSe–SnSe 2, pure SnSe or pure SnSe 2 thin films could be obtained. SnSe films were obtained at 650 °C with a SnCl 4 to Et 2Se ratio greater than 10. The SnSe films were silver–black in appearance and adhesive. SnSe 2 films were obtained at 600–650 °C they had a black appearance and were composed of 10 to 80 μm sized adherent crystals. Films of SnSe only 100 nm thick showed complete absorbtion at 300–1100 nm. 相似文献
19.
Anatase titania nanopowders with mean particle sizes of 7, 15, 26 and 38 nm synthesized by sol–gel method were used to sinter bulk TiO 2 nanoceramics. The relative densities and average grain sizes of the TiO 2 nanoceramics were studied as a function of the compaction pressure on green sheet, sintering temperature, and mean particle size of the starting TiO 2 nanopowders. The relative density of the TiO 2 nanoceramics increases rapidly and average grain size increases slowly with increasing sintering temperature below 800 °C. Sintering at higher temperatures above 800 °C enhances the densification of the TiO 2 nanoceramics and leads to a increase of the grain size. Bulk TiO 2 nanoceramics with an average grain size of less than 60 nm and relative density over 95% was obtained by a phase-transformation-assisted pressureless sintering at a relatively low temperature (800 °C). 相似文献
20.
The evolution of microstructure and texture of molecular beam deposited Si 0.7Ge 0.3 films on SiO 2 at the deposition temperature range of 400–700°C was investigated by X-ray diffraction and transmission electron microscopy. At deposition temperatures between 400 and below 500°C, the films were directly deposited as a mixed-phase on SiO 2 and have a inversely cone-shaped structure. In this temperature range deposited as a mixed-phase, the grain size increases as the temperature increases, so that the grains not only grow up by deposition, but also laterally grow by the solid phase crystallization, furthermore, the texture is changed from a {110} texture to mixed {311} and {110} textures. At 500°C, the film was deposited as only a crystalline phase and has a columnar structure with a strong {110} texture. In the temperature range of 500–700°C, as the temperature increases, the {311} and {111} textures develop whereas the {110} texture reduces. The film deposited at 700°C has a random orientation and structure. 相似文献
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