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1.
The analysis of the interface between grains and pores in thin films of CeO2, prepared by two different sol-gel procedures, was performed using grazing incidence small-angle X-ray scattering. The existence and the average thickness of an interfacial layer, formed during one of the preparation procedures, were examined by analyzing the depletion of scattering intensity in the Porod's scattering region. 相似文献
2.
Evolution of texture in CeO2 thin films was studied using biased magnetron sputtering and ion beam assisted magnetron sputtering. Films deposited onto polycrystalline Hastelloy metal substrates by biased magnetron sputtering develop preferential (002) growth as the energy of the ions is increased from zero to above 100 eV. For ion beam assisted magnetron sputtering (magnetron IBAD), with the ion beam directed at 55° to the substrate normal, the evolution of biaxial alignment is controlled by the ion beam energy and the ion/atom arrival rate ratio. Ion beam energies >200 eV and ion/atom ratios >0.3 lead to perfect biaxial alignment with one pole aligned along the ion beam direction. Epitaxial growth of CeO2 films was observed for MgO(001) substrates at 750°C without any ion assistance, and on yttria-stabilised zirconia (001) buffer layers at room temperature and a bias of −80 V. 相似文献
3.
Thin films of titania-ceria have been prepared via sol-gel processing by employing titanium and cerium chloride compounds in highly acidic conditions for the precursor sol. This sol-gel route allows obtaining titania-ceria and cerium titanate films, CeTi2O6, after thermal treatment in air. The films exhibit a high optical transparency which is modulated by controlling the composition and the thermal treatment. The materials have been characterized by X-ray diffraction, UV-visible spectroscopy, ellipsometric spectroscopy and atomic force microscopy. The titania-ceria films show, as a function of the composition, the formation of different phases after thermal treatment in air at 800 °C. In particular, with the composition Ce25-Ti75 we have obtained a pure cerium titanate phase, CeTi2O6, which can be formed only in a very strict range of compositions. 相似文献
4.
P.J. King M. WernerP.R. Chalker A.C. JonesH.C. Aspinall J. BascaJ.S. Wrench K. BlackH.O. Davies P.N. Heys 《Thin solid films》2011,519(13):4192-4195
Cerium oxide dielectric thin films have been grown on n-type silicon by atomic layer deposition using a monomeric homoleptic CeIV alkoxide precursor with water vapour. Herein we report the dielectric properties of CeO2 films deposited from tetrakis(1-methoxy-2-methyl-2-propanolate)cerium. The resulting films exhibit permittivities in the range 25-42 at 1 MHz with a strong dependency on the deposition temperature. The microstructural origin of this behaviour has been investigated. The as-deposited films were found to be crystalline and they exhibited the cubic fluorite structure for deposition temperatures in the range 150 °C to 350 °C. Variations in the crystallite sizes are governed by the deposition temperature and have been estimated using a Debye-Scherrer analysis of the X-ray diffraction patterns. The changing crystallite size correlates with changes seen in the triply-degenerate F2g first-order Raman line half-width at 465 cm− 1. It is concluded that the frequency dependency of the film dielectric properties is strongly influenced by the crystallite size which in turn is governed by the growth temperature. 相似文献
5.
S.K. Sharma P. Thakur D.K. Shukla N.B. Brookes K.R. Pirota M. Knobel 《Thin solid films》2010,519(1):410-413
Ce1 − xFexO2 − δ/LaAlO3(001) thin films (x = 0.01 and 0.03) have been prepared by pulsed laser deposition method and thoroughly characterized using X-ray diffraction (XRD), dc magnetization, near edge X-ray absorption fine structure (NEXAFS), and X-ray magnetic circular dichroism (XMCD). XRD data reveal a single-phase cubic structure with a strong crystallographic orientation along the (200) plane. Room temperature ferromagnetism is confirmed through isothermal hysteresis as well as temperature dependent magnetization measurements, which clearly show the ferromagnetic Curie temperature occurring at least above 350 K. The Fe L3,2 edge NEXAFS spectra for both Fe-doped thin films exhibit mixed valent Fe2+/Fe3+ states, whereas Ce M5,4 edge shows the 4+ state of Ce, throughout the doping. With the increase in Fe doping, Fe2+ state increases and a simultaneous decrease in magnetization value is also observed. The XMCD signal of both samples reveals the ferromagnetic ordering of substituted Fe ions in the ceria matrix. Our results indicate that ferromagnetism is intrinsic to the ceria system and is not due to any secondary magnetic impurity. 相似文献
6.
F. Wu A. Pavlovska D.J. Smith R.J. Culbertson B.J. Wilkens E. Bauer 《Thin solid films》2008,516(15):4908-4914
Thirty to a hundred-nm thick epitaxial CeO2 layers are grown on YSZ (100), (110) and (111) surfaces of yttria-stabilized ZrO2 (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
7.
Molybdenum sulphide was cathodically electrodeposited from aqueous solutions of sodium tetrathiomolybdate. The as-deposited films were X-ray amorphous with a composition, measured by microprobe analysis, close to MoS2. Annealing these films in Ar resulted in highly-textured films of MoS2 with the van der Waals planes parallel to the substrate. A small expansion in the c spacing of the annealed films was explained by the presence of oxygen in the crystals. A direct bandgap of 1.78 eV was found for the annealed films. 相似文献
8.
Highly (100)-oriented CeO2 films prepared on amorphous substrates by laser chemical vapor deposition
CeO2 films were prepared on amorphous silica substrates by laser chemical vapor deposition using cerium dipivaloylmethanate precursor and a semiconductor InGaAlAs (808 nm in wavelength) laser system. The laser spot size was about 20 mm, which was sufficient to cover the whole substrate. Highly (100)-oriented CeO2 films were obtained at extraordinary high deposition rates ranging from 60 to 132 μm/h. Films exhibited a columnar feather-like structure with a large number of nano-sized voids, and a surface morphology consisting of either nearly flat or pyramidal top-ending columns depending on the laser power. Nearly flat top-ending columns could be fairly (100)-oriented at the top and (111)-oriented laterally. 相似文献
9.
Thin (d=60 nm/140 nm) nanocrystalline CeO2 films were deposited onto mica flakes. Their sintering behavior was characterized and compared with the known equivalent TiO2 special effect pigments in terms of grain size, grain growth and layer porosity. The color travel of the resulting products was analyzed using the CIELAB color metric. The intensity of the interference color was correlated with the effective refractive indices of these films, which also depend on their porosity. 相似文献
10.
Epitaxial growth of CeO2 and yttria-stabilized ZrO2 (YSZ) double layer films has been successfully carried out on biaxially textured nickel substrates at a temperature between 400 and 600 °C using electrostatic spray assisted vapour deposition method. The structure of the double layer was characterized by X-ray diffraction and scanning electron microscopy. The results show that highly oriented CeO2/YSZ double buffer films were formed epitaxially onto biaxially textured Ni substrates. The orientation relationships between YSZ layer and Ni substrate are 001YSZ//001Ni and 110YSZ//100Ni, while the orientation relationships between CeO2 and YSZ are 001CeO2//001YSZ and 100CeO2//100YSZ. 相似文献
11.
TiO2 films were grown by an advanced pulsed laser deposition method (PLD) on ITO substrates to be used as functional electrodes in the manufacturing of solar cells. A pure titanium target (99.99%) was irradiated by a Nd:YAG laser (355 and 532 nm, 5 ns, 35 mJ, 3 J/cm2) in an oxygen atmosphere at different pressures (20-160 mTorr) and at room temperature. After deposition, the films were subjected to an annealing process at 350 °C. The film structure, surface morphology, thickness, roughness, and optical transmission were investigated. Regardless of the wavelength used, the films deposited at room temperature presented only Ti2O and TiO peaks. After thermal treatment, the TiO2 films became strongly crystalline, with a tetragonal structure and in the anatase phase; the threshold temperature value was 250 °C. The deposition rate was in the range of 0.035-0.250 nm/pulse, and the roughness was 135-305 nm. Optical transmission of the films in the visible range was between 40% and 60%. 相似文献
12.
C. Cantalini W. Wlodarski H. T. Sun M. Z. Atashbar M. Passacantando A. R. Phani S. Santucci 《Thin solid films》1999,350(1-2):276-282
In2O3 thin films have been prepared from commercially available pure In2O3 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 In2O3−x (JCPDS card 6-0416). XPS characterisation has revealed the formation of stoichiometric In2O3 (HVTE) and nearly stoichiometric In2O3−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 NO2 gas (0.7–7 ppm concentration range), at 250°C working temperature. At this temperature and 0.7 ppm NO2 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 In2O3 films to CO and CH4. Negligible H2O cross has resulted in the 40–80% relative humidity range, as well as to 1 ppm Cl2 and 10 ppm NO. Only 1000 ppm C2H5OH has resulted to have a significant cross to the NO2 response. 相似文献
13.
Oxide thin films synthesized using the sol-gel technique have the advantages of low cost, high thickness control, tunable refractive index and silicon technology compatibility, properties that make them potential materials for optoelectronic applications. For very thin films with low porosity, the determination of sorption and optical properties is quite complex because of the small sample size. Thus, there is a need to use especially designed techniques to obtain reliable results. In this work, a comprehensive study on the porosity evolution of SiO2 and TiO2 thin films using X-Ray Reflectometry and Environmental Ellipsometric Porosimetry is presented. For sol-gel SiO2 thin films, it was found that the effective refractive index increases with thermal treatment as the porosity decreases. However, the refractive index of the walls was found constant. For sol-gel TiO2 films, crystallized in anatase phase, both the effective refractive index and the wall refractive index increase with thermal treatment. SiO2 and TiO2 thermal oxides were also characterized for comparison. 相似文献
14.
Crystallized TiO2 thin films were deposited on a non-heated substrate by two methods: oxygen-ion-assisted reactive evaporation (ORE) and high-rate reactive sputtering (HRS) using two sputtering sources. When the films were deposited on an unheated glass substrate, amorphous films were initially grown on the substrate in case of both deposition methods, although an increase in oxygen-ion energy above 600 eV led to a growth of a crystallized layer on the amorphous films in the case of ORE. When the films were deposited by HRS on a crystallized TiO2 seed layer, homo-epitaxial growth was observed, and crystallized TiO2 films with an excellent hydrophilic property were obtained on unheated substrate. In contrast, when the films were deposited by ORE, amorphous films were initially grown on the crystallized TiO2 seed layer in a similar manner to the deposition of films on a glass substrate, and homo-epitaxial growth was not observed. These results suggest that the large kinetic energy of titanium atoms arriving at the substrate during HRS is a key factor in promoting epitaxial growth of the TiO2 film at low temperature. 相似文献
15.
The properties of sol–gel derived CeTi2O6 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 CeTi2O6 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 TiO2 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 CeTi2O6 films shows the presence of photoactivity in these films. The photocatalytic response of CeTi2O6 films is found to be superior to the TiO2 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
16.
We have grown RuO2 films by pulsed liquid injection atomic layer deposition using (Ru(thd)2(cod)) dissolved in pyridine. The deposition process took place at 290 °C and consisted of four steps. The films exhibited smooth surface. Analysis of the films using secondary ion mass spectroscopy (SIMS) revealed low content of carbon in the films. Resistivity of the RuO2 film at room temperature was about 160 µΩ cm. 相似文献
17.
Cerium oxide films of thickness 0.1–300 μm were deposited on Ni substrates via cathodic electrolytic and electrophoretic deposition. The films were studied by X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. Experimental results obtained by both deposition methods are compared. The influence of deposition parameters and additives on deposition yields and film morphologies is studied and discussed. 相似文献
18.
Electrochromic TiO2 anatase thin films on ITO were prepared by the sol-gel dipping method using a solution of titanium tetraisopropoxide, diethanolamine and ethanol. The films were transparent in the visible range and can be colored in a solution of LiClO4 in propylene carbonate. The transmittances of the colored films were found to be strongly dependent on the Li+ inserted charge. Combining the experimental data obtained from in situ Raman and in situ transmittance spectra with the data from chronoamperometic measurements, it was demonstrated that the fully colorated state of the TiO2 anatase films is Li0.5TiO2 with a crystalline structure of Imma space group symmetry. In the Raman spectra this coloration state exhibits five characteristic bands at 176, 224, 316, 531 and 629 cm−1. 相似文献
19.
Undoped and chromium doped titanium oxide thin films were fabricated by spray pyrolysis by using a solution of titanium tetrachloride and ethyl alcohol. The films have been deposited on heated glass substrates at 373 K. After annealing for 90 min at 723 K, the initially amorphous films became polycrystalline with a predominant anatase structure and average crystallite sizes depending on dopant (Cr) concentration. The repartition of chromium impurities in the matrix of titanium oxide films, analyzed by electron paramagnetic resonance and X-ray photoelectron spectroscopy showed that the entrance of chromium into the anatase structure is mainly achieved by substitution. A decrease in unit cell parameters ratio (c/a) with the increase of chromium content sustains this assertion. The wetting properties of the titanium oxide films were evaluated from contact angle measurements between de-ionized water and films surface during- and post-irradiation with UV light. The correlation between the concentration of the dopant, film structure, surface morphology and wettability characteristics is discussed. 相似文献
20.
Translucent CaGa2S4:Ce thin films were prepared by pulsed laser deposition. Optical absorption associated with the 4f1 (2F5/2) to 5d2 second-highest excited state transition of the Ce3+ ion was clearly observed at 3.60 eV as well as the 4f1 (2F5/2) to 5d1 lowest excited state transition at 2.93 eV. Energy splitting of the 5d state by the crystal field is discussed in terms of a model of a square antiprism structure with D4d symmetry. 相似文献