Structural Properties and Stress in ZnO Films Obtained from a Nanocolloidal Sol

This paper deals with stress analysis of ZnO films, via substrate curvature measurements. The films were prepared from a nanocolloidal sol by dip-coating and annealed from 150 to 400°C under pure or ozone-enriched oxygen. The chemical film evolution is followed by FT-IR spectroscopy, and the structural properties by X-ray diffraction and optical absorption spectroscopy. It is shown that the films annealed under pure oxygen are in a compressive stress state due to a stuffing effect during grain growth, whereas the films annealed under ozone-enriched oxygen are in a tensile stress state due to pore collapsing. This astonishing difference has been attributed to the skeleton, thinner in the latter than in the former films. Indeed, the acidifying action of ozone on alcohols is believed to be responsible for slowing down the grain growth during annealing.     

Ultraviolet-Laser-Induced Crystallization of Sol-Gel Derived Inorganic Oxide Films

Structural changes stimulated by ultraviolet (UV) laser irradiations of sol-gel derived inorganic oxide films were investigated. Dried gel films of TiO₂, Nb₂O₅, Ta₂O₅, SrTiO₃ and Pb(Zr _x Ti_1–x )O₃ (PZT) were found to be crystallized by the laser irradiation. On the other hand, the photo-induced change in gel films of BaTiO₃, LiNbO₃ and LiTaO₃ was not observed although the laser beams were absorbed in the films. These sol-gel films were thermally crystallized at almost the same temperature around 600–700°C except TiO₂. Thus, the UV-laser-induced crystallization is not directly ascribed to a simple thermal effect with the irradiation. Photochemical properties of the cations are assumed to be important for the change in sol-gel films.     

Selective Formation of Spinel Iron Oxide in Thin Films by Complexing Agent-Assisted Sol-Gel Processing

The structure of iron oxide was controlled by regulating the hydrolytic polymerization of aquo iron complexes with organic polydentate ligands such as diols. Iron oxides were prepared by calcining the precursor polymers obtained from iron nitrate nonahydrate and diols. When the diols were 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol, α-Fe₂O₃ with corundum structure appeared exclusively or as the main crystalline phase, in spite of the amount of diol used and the calcination temperature. In the case of 1,2-decanediol and 1,2-dodecanediol, when five moles of the diols were used to one mole of iron nitrate and the calcination temperatures were below 400°C, ψ-Fe₂O₃ with spinel structure appeared as the main phase and, when less than five moles of the diols were used, α-Fe₂O₃ appeared exclusively or as the main phase, irrespective of the calcination temperature. This tendency was also observed in thin films. Thus, a transparent magnetic film composed of γ-Fe₂O₃ could be prepared by applying a benzene solution of the iron polymer, obtained with 5 equivalents of 1,2-decanediol, on quartz and calcining the gel film at 350°C.     

Structural and IR Spectroscopic Analysis of Sol-Gel Processed CuFeMnO4 Spinel and CuFeMnO4/Silica Films for Solar Absorbers

Black colored CuFeMnO₄ spinel powders and films were prepared using sol-gel process from Mn-acetate and Fe- and Cu-chloride precursors. Films were deposited by dip-coating technique and heat-treated at 500°C. For CuFeMnO₄/silica films 3-aminopropyl-triethoxysilane (3-APTES) or tetraethoxysilane (TEOS) were used in molar proportion (Mn : Cu : Fe) : silica = 1 : 1. Films and powders were prepared by heating at 500°C. IR spectroscopic measurements were employed to follow the hydrolysis-condensation reactions in (Mn : Cu : Fe)/3-APTES sols hydrolysed with water, and (Mn : Cu : Fe)/TEOS sols hydrolysed with (NH₃)_aq (Stöber processing). The resulting coatings were examined with transmission electron microscopy (TEM) combined with electron dif-fraction analyses, Rutherford back scattering (RBS) and proton induced X-ray emission (PIXE) techniques. Results revealed that (Mn : Cu : Fe)/3-APTES films had a composite structure consisting of the upper Cu_1.4Mn_1.6O₄ spinel and the lower amorphous SiO₂ layer. RBS measurements confirmed the composite structure, showing also that the composition of the film was Mn : Cu : Fe = 1 : 0.96 : 0.29, i.e. close to the precursors ratio Mn : Cu : Fe = 3 : 3 : 1. (Mn : Cu : Fe)/TEOS films prepared from sols which were catalysed with (NH₃)_aq consisted of amorphous monodispersed spherical SiO₂ particles with a size of about 400–420 nm. Solar absorbance (a _s) and thermal emittance (e _T) values of CuFeMnO₄ (500°C) and (Mn : Cu : Fe)/TEOS films (500°C) showed that CuFeMnO₄ films could be used as potential selective coatings for solar absorbers in solar collector systems.     

Ultraviolet-Laser-Induced Crystallization of Sol-Gel Derived Indium Oxide Films

Modification of sol-gel derived indium oxide thin films using ultraviolet lasers was investigated. Irradiation by an ArF excimer (6.4 eV) and the fourth harmonic generation of a Nd : YAG laser (4.7 eV) was found to be effective in crystallization with a loss of hydroxyl groups and a decrease in the sheet resistance of the sol-gel films. Transparent crystalline indium oxide films were successfully obtained by 6.4 eV laser irradiation at fluences below 20 mJ/(cm2·shot), whereas degradation of the films was induced by a relatively high-fluence beam.     

Preparation and Characterization of Molybdenum Oxide Thin Films by Sol-Gel Process

This paper presents a new sol-gel process to prepare molybdenum oxide thin films. A molybdenum acetylacetonate sol was prepared by employing the system CH₃COCH₂COCH₃/MoO₃/C₆H₅CH₃/HOCH₂CH₂OCH₃. A molybdenum acetylacetonate gel was prepared by addition of aqueous NH₃. Thermal gravimetry (TG) and differential thermal analyses (DTA) of the gel suggested that crystallization of MoO₃ occurs in a 140 K temperature range around 508°C. MoO₃ films were prepared on fused silica, Si (111) and Al₂O₃ (012) substrates by annealing spin coating films of the sol in oxygen environment at 508°C. X-ray diffraction (XRD) showed that all films crystallize in -MoO₃ structure, and crystallites on fused silica substrate are arbitrarily oriented while those on Si (111) and Al₂O₃(012) substrates oriented in the (010) direction. SEM investigations showed that MoO₃ grains of all films are randomly distributed, with a longitudinal dimension of about 1–5 m and the film thickness is about 1 m.     

Preparation and Characterization of MgO Thin Films by a Novel Sol-Gel Method

MgO thin films have been prepared on Si substrates by a novel and simple sol-gel method using magnesium nitrate and collodion as starting material. Solutions consisting of magnesium nitrate in a mixture of collodion and ethanol were spin-coated onto silicon substrates. It was found that collodion was a necessary component to form stable sols and the crystallization and structures were clearly dependent on the amount of the collodion and the annealing temperature. The MgO thin films with good crystallization were obtained after annealing at 800°C. Meanwhile, the microstructure of the MgO films was examined by transmission electron microscopy and atomic force microscopy.     

SiO2-Iron Oxide Composites Obtained by Sol-Gel Method

Composite SiO₂-iron oxide materials were prepared by three experimental procedures. In the first case (1), the iron oxides were precipitated during the sol-gel process. In the second case (2), the SiO₂ matrix was initially obtained, and the iron oxides were formed by thermal treatment after impregnation of a soluble Fe²⁺ salt in the previously processed matrix. In the third method (3), ferrite powders, prepared by wet chemical method, were embedded into a SiO₂ based sol-gel matrix. Two type of precursors (tetraethoxysilane (TEOS) or methyltriethoxysilane (MTEOS) were used as SiO₂ sources. Various properties versus both type of precursor and on the method of preparation were noticed. Materials with high porosity and nano-sized iron oxide content could be prepared using the mentioned above methods.     

氧化铑变色薄膜的制备及其电变色研究

采用溶胶-凝胶方法制备了氧化铑电致变色薄膜。通过施加阴极或阳极电位, 薄膜在碱性电解液中呈现从亮黄（还原态）到深绿（氧化态）的可塑颜色变化,而 且可达到上千次循环而性能不变。采用XRD,SEM,TG,DTA,UVV,FTIR和循环伏安 等技术对薄膜的晶态、形貌、热处理过程和电变色过程进行了研究。得出100 ℃处 理的膜内含有一定量的结晶水,其性能最好。对薄膜的电致变色性能如：着色效率 、响应时间及循环寿命、开路记忆等进行了测试,并讨论了氧化铑薄膜电变色的反 应机理。     

溶胶-凝胶工艺制备发光薄膜研究进展

本文综述了通过深胶－凝胶工艺制备发光薄膜的基本过程、薄膜的表征方法、发光薄膜的当前发展及应用情况。依据组成特点,对溶胶－凝胶法制备的发光薄膜乾地了分类阐述,并预言了今后该法制备发光薄膜的发展趋势。     

Analysis of Antimony Doping in Tin Oxide Thin Films Obtained by the Sol-Gel Method

The antimony doping in SnO₂ thin films prepared by the sol-gel dip-coating method has been studied using two characterization techniques. In order to determine the actual doping level directly in the deposited layers, X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) have been used. We found that this doping level is systematically lower than expected from the starting solutions composition, and that two oxidation states are present: Sb³⁺ and Sb⁵⁺. As the antimony content increases, there is a competition between Sb⁵⁺ and Sb³⁺ species.The SnO₂: Sb thin films have also been observed by transmission electron microscopy (TEM), showing that the measured mean size of crystallites decreases as the Sb content increases in the oxide. No precipitates of either Sn or Sb oxides (other than SnO₂) could be detected.     

Influence of Elaboration Parameters on the Properties of Tin Oxide Films Obtained by the Sol-Gel Process

The influence of elaboration parameters during the sol-gel process is studied for tin oxide films deposition. The Dip Coating Sol-Gel route can be divided into three elaboration stages: the pulling phase and the drying and densification steps. During the pulling phase, the relative humidity ratio and the withdrawal speed are found to influence the film morphology and the film thickness respectively. Then, we show how a correct control of the sample drying is able to eliminate cracks. The densification step (temperature and duration), leading to the final network, is considered in details, and resulting effects on physical properties are presented: crytallinity, optical behaviour, atomic density, stoichiometry, electrical conductivity etc... We show through these results the specificity of the tin oxide elaborated with our procedure     

Auto-Organisation in Silica-Based Organic-Inorganic Gels Obtained by Sol-Gel Process

A new type of hybrid material is prepared through sol-gel processing by the polycondensation of (MeO)₃Si–R–Si(OMe)₃ units containing a rigid organic anisotropic group R. The hybrid covalently bounded organic-inorganic gel shows an unexpected structural birefringence n (n = 2 × 10^–3). This birefringence is induced by a strain field anisotropy during gel aging as revealed by simultaneous dynamic light scattering and birefringence measurements. To better address the role of the strain field, we use a free interface sol-gel/air to control strain anisotropy and to measure the gel optical axis and its birefringence. We find that the birefringence is associated to a long-range orientational order of organic moieties induced by the strain anisotropy during the gel aging.     

镍氢蓄电池材料用氧化锆布膜中铝含量的分析测试技术

运用N2O-C2H2火焰原子吸收光谱法进行镍氢蓄电池材料用氧化错布膜中铝含量的分析测试技术,建立了铝的共振线、灯电流、火焰燃烧比等最佳实验条件.显示出该方法具有很好的灵敏度和重现性,具有操作简便、容易掌握、分析周期短、干扰小等优点.测定样品铝含量的相对标准偏差均小于1.0%(n=6).标准加入回收率均在97.5%～98.6%范围内.适用于镍氢蓄电池材料用氧化锆布膜中铝含量的控制分析和样品系统分析.     

Sol-Gel Deposited Sb-Doped Tin Oxide Films

The structural, electrical and optical properties of single sol-gel derived antimony-doped tin oxide (ATO) films sintered at 550°C have been measured. The reproducibility of both the preparation and the characterization procedures have been tested by a round-robin test involving eight laboratories within a Concerted European Action (CEA) project. The resistivity measured as a function of Sb content has been obtained by electric and reflectance and transmission measurements. Their differences are discussed in terms of structural and grain boundary effects. An increase of Sb content results in a decrease of the crystallite size (7.0 to 5.4 nm) and a greater influence of the grain boundary.     

Fluorescence and Absorption Probe of Metal Ion Centers in Silicates Obtained by the Sol-Gel Technique

An optical probe of the structure of metal ion centers in sol-gel systems based on Eu3+ and Nd3+ emission and absorption measurements has been developed. The effects of the structure and composition of organic complexes of Eu3+ on the clustering processes and retention of water molecules in the gel and glasses were investigated. Mechanical properties of systems prepared with Triton detergent were also investigated. The studies have been performed for two types of complexes of lanthanides, with -diketones as the precursor lanthanide salts. The emission, excitation and absorption spectra of the precursor salts, gels and glasses heated to 1100 K were measured. Splitting of the levels and electronic transition probabilities were analyzed. The IR spectra were used for the detection of the OH– modes in the glasses.     

Strategies for Spatially Separating Molecules in Mesostructured Sol-Gel Silicate Films

Three strategies for placing molecules in designated regions of mesostructured thin films made by the sol-gel dip-coating technique are demonstrated. These strategies all involve one-step syntheses where all of the components are present in the sol from which the substrate is pulled. Silicate films templated by ionic surfactants contain three spatially-separated regions: a silicate framework, an organic region formed by the hydrocarbon tails of the surfactants, and an intervening ionic interface formed by the charged surfactant head groups. The first method exploits lipophilic interactions between the molecule and the micelle to place it in the organic region. The second method uses chemical bonding of multiple trialkoxysilane groups in a three dimensional array on the molecule to place it in the silica framework. The third method uses multiple functionality at opposite sides of the molecule to enable it to span two regions. Luminescent molecules are used, and spectroscopy monitors the formation.     

Scratch-Resistant Improvement of Sol-Gel Derived Nano-Porous Silica Films

Scratch-resistance of sol-gel derived nano porous silica films were studied. The thin films were prepared with a dip-coating method from both one-step and two-step catalyzed silica sols, and treated in a mixture gas of ammonia and water vapour afterwards. The thin films were characterized by using Atomic Force Microscope (AFM), ellipsometer, Fourier-transform Infrared Spectroscope (FTIR), respectively. Experimental results have shown that the two-step catalysis remarkably improves strength of the films, and abrasion-resistance and adhesion of the silica films were further increased after the mixture gas treatment. It is attributed to the cross-linking of silica particles in the sols by randomly branched or/and entangled linear chains and more Si–O–Si bonds formed by the mixture gas treatment.     

Atomic Force Microscopy Study of TiO2 Films Obtained by the Sol-Gel Method

Atomic Force Microscopy (AFM) was used to study the influence of thermal treatments on the structural and textural properties of the sol-gel TiO2 films obtained from Ti(OC3H7i)4. X-ray diffraction (XRD), ellipsometric and porosity measurements have also been made.The TiO2 sol-gel films were homogeneous, transparent and amorphous. Heat treatments in the 400–600°C range indicate that the films have a strong tendency to crystallization. The high initial homogeneity of the TiO2 films was preserved during the crystallization process. AFM shows that the thermally treated films exhibit uniform, monodispersed crystals.     

Thermal Decomposition and Crystallization of Aqueous Sol-Gel Derived Zirconium Acetate Gels: Effects of the Precursor Solution pH

Crystalline zirconia has previously been formed by desiccation and pyrolysis of a pH 3.4 zirconium acetate precursor solution. In this study, amorphous gels were formed by desiccation of zirconium acetate precursor solutions at pH 0.9 to 3.4 obtained by adding hydrochloric acid and at pH 8.0 by adding ammonium hydroxide to the available pH 3.4 precursor solution. The concentrations of the uncomplexed zirconium ion and the 1 : 1 and 1 : 2 zirconium acetate complexes varied with pH. Decomposition of the amorphous gel and its structure evolution to form crystalline zirconia by pyrolysis were studied. Several decomposition and structure transition temperatures occurring in the pyrolysis and the polymorph distribution in the pyrolysis products were dependent on the pH of the precursor solution. These variations of structure evolution with pH were also related to the relative concentrations of specific zirconium complexes in the precursor solutions. Removal of carbon by pyrolysis was improved by adding hydrochloric acid or ammonium hydroxide to the pH 3.4 precursor solution.