Liquid phase deposition synthesis of hexagonal molybdenum trioxide thin films

Hexagonal molybdenum trioxide thin films with good crystallinity and high purity have been fabricated by the liquid phase deposition (LPD) technique using molybdic acid (H₂MoO₄) dissolved in 2.82% hydrofluoric acid (HF) and H₃BO₃ as precursors. The crystal was found to belong to a hexagonal hydrate system MoO₃.nH₂O (n~0.56). The unit cell lattice parameters are a=10.651 Å, c=3.725 Å and V=365.997 Å³. Scanning electron microscope (SEM) images of the as-deposited samples showed well-shaped hexagonal rods nuclei that grew and where the amount increased with increase in reaction time. X-ray photon electron spectroscopy (XPS) spectra showed a Gaussian shape of the doublet of Mo 3d core level, indicating the presence of Mo⁶⁺ oxidation state in the deposited films. The deposited films exhibited an electrochromic behavior by lithium intercalation and deintercalation, which resulted in coloration and bleaching of the film. Upon dehydration at about 450 °C, the hexagonal MoO₃.nH₂O was transformed into the thermodynamically stable orthorhombic phase.     

Atomic layer deposition of crystalline molybdenum oxide thin films and phase control by post-deposition annealing

Molybdenum forms a range of oxides with different stoichiometries and crystal structures, which lead to different properties and performance in diverse applications. Herein, crystalline molybdenum oxide thin films with controlled phase composition are deposited by atomic layer deposition. The MoO₂(thd)₂ and O₃ as precursors enable well-controlled growth of uniform and conformal films at 200–275 °C. The as-deposited films are rough and, in most cases, consist of a mixture of α- and β-MoO₃ as well as an unidentified suboxide MoO_x (2.75 ≤ x ≤ 2.89) phase. The phase composition can be tuned by changing deposition conditions. The film stoichiometry is close to MoO₃ and the films are relatively pure, the main impurity being hydrogen (2–7 at-%), with ≤1 at-% of carbon and nitrogen. Post-deposition annealing is studied in situ by high-temperature X-ray diffraction in air, O₂, N₂, and forming gas (10% H₂/90% N₂) atmospheres. Phase-pure films of MoO₂ and α-MoO₃ are obtained by annealing at 450 °C in forming gas and O₂, respectively. The ability to tailor the phase composition of MoO_x films deposited by scalable atomic layer deposition method represents an important step towards various applications of molybdenum oxides.     

Surface layer-by-layer chemical deposition reaction for thin film formation of nano-sized metal 8-hydroxyquinolate complexes

The feasibility of a novel and simple layer-by-layer chemical deposition method for the preparation of nano-sized metal 8-hydroxyquinolate complexes has been investigated and reported. Uniform nanocrystalline films have been synthesized via dipping a substrate alternately in metal ion solution followed by ligand solution. The stoichiometry of the as-grown anhydrous Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complex crystals were confirmed from the metal analysis and molar stoichiometric ratio of metal ion to 8-hydroxyquinoline. This was characterized as 1:2 for the Co(II), Ni(II), Cu(II) and Zn(II)–quinolate complexes. The Fe(III)–quinolate thin film was found to exhibit a 1:3 ratio. Electron impact-mass spectra (EI-MS) of all the synthesized thin film metal quinolate complexes were recorded and the results refer to the existence of the molecular ion peak at the corresponding m/z values. Confirmation of such stoichiometric 1:2 and 1:3 ratios were also evident from the (EI-MS) study. The deposited thin films were also subjected to analysis by a scanning electron microscope (SEM) and a particle size ?50 nm was detected. FT-IR and UV–Vis spectroscopy were further used to confirm the structure of the metal 8-hydroxyquinolate complexes. Thermal gravimetric analysis (TGA) was also used to follow up the possible thermal decomposition steps and to calculate the thermodynamic parameters of the nano-sized metal complexes.     

Electrochemical sensor for acetaminophen based on an imprinted TiO2 thin film prepared by liquid phase deposition

An electrochemical sensor based on a molecularly imprinted TiO₂ thin film is proposed for the determination of acetaminophen. The imprinted TiO₂ films were obtained by liquid phase deposition (LPD) in the presence of acetaminophen, the functional monomer and the aqueous solution of (NH₄)₂TiF₆ and H₃BO₃. The results show that acetaminophen is embedded into the imprinted film in the presence of p-tert-butylcalix[6]arene as a functional monomer, and can be removed completely by washing with ethanol. The surface morphology, spectral properties and electrochemical characterizations of the imprinted sensor were investigated in detail. The combination of molecularly imprinted and LPD technique was shown to be a general strategy for constructing a molecular recognition system.     

Tunable dielectric thin films by aqueous, inorganic solution-based processing

Sub-micron, nanolaminated, dielectric thin films comprised of amorphous aluminum oxide phosphate (AlPO) and hafnium oxide sulfate (HafSOx) layers were fabricated in open-air conditions from aqueous inorganic precursors by spin coating with minimal thermal processing. These nanolaminated thin film insulators display an averaging effect of effective dielectric permittivity in devices with controlled AlPO:HafSOx thickness ratios, enabling tunable dielectric properties. X-ray reflectivity measurements were used to characterize film thickness, smoothness, and uniformity. Scanning electron microscopy was used to analyze final nanolaminated devices. Electrical characterization of metal-insulator-insulator-metal capacitors revealed tunable relative dielectric constants ranging from approximately 5–10 with loss tangents less than 2% at 10 kHz in devices with approximately 300 nm total dielectric thickness. The results suggest a simple, inexpensive processing approach for fabricating devices that require insulating layers with specific dielectric properties.     

Model of electrochromic and related phenomena in tungsten oxide thin films

We have developed a model of electrochromic and related phenomena in tungsten oxide thin films based on the assumption that the constitution of such films is heterogeneous and built up of nanosized particles, pores and adsorbed substances (mainly water). It is discussed why a high-efficiency reversible blue colour is observed in amorphous tungsten oxide films (α-WO₃ films) as well as why such porous thin films with polycrystalline or amorphous constitution and with a variety of particle properties can be easily obtained by a physical vapour deposition process in a low-pressure atmosphere in the presence of water. A substrate temperature in the range 450–550 K corresponds to some plateau on the water desorption curves which divided physically adsorbed water from chemically adsorbed water. Two types of structural units based on tetrahedrally and octahedrally coordinated tungsten ions have the main role in the formation of the film constitution. The tetrahedral structural units have a glass-forming function, but the octahedral ones have a modification function. From the electrochemistry point of view, the internal multiphase interfaces in such films are distributed multiphase electrodes. The adsorbed water together with defects of the oxide particles provide reagents for reversible coloration reactions in the film. The colour centres can be induced thermally (oxygen nonstoichiometry) or electrically (injected ions) or by radiation (photoinjected hydrogen). The electrochromism and related phenomenon of α-WO₃ films can be directly related to ion insertion/extraction processes controlled by external forces. Electronic Publication     

Application of liquid phase deposited titania nanoparticles on silica spheres to phosphopeptide enrichment and high performance liquid chromatography packings

A novel core-shell composite (SiO(2)-nLPD), consisting of micrometer-sized silica spheres as a core and nanometer titania particles as a surface coating, was prepared by liquid phase deposition (LPD). Here, we show the resulting core-shell composite to have better efficient and selective enrichment for mono- and multi-phosphopeptides than commercially available TiO(2) spheres without any enhancer. The material exhibited favorable characteristics for HPLC, which include narrow pore size distribution, high surface area and pore volume. We also show that the core-shell composite can efficiently separate adenosine phosphate compounds due to the Lewis acid-base interaction between titania and phosphate group when used as HPLC packings. After coating the silica sphere with titania by LPD, the silanol of silica spheres will be shielded and that the stationary phase, C(18) bonded SiO(2)-3LPD, could be used under extreme pH condition.     

Characterization of zinc-modified lithium tantalate thin films fabricated by chemical solution deposition method

Zinc-substituted lithium tantalate thin films were fabricated for improving the electrical resistivity by compensating the valence of lattice defects in LiTaO₃ crystal. The films with the chemical composition of (Li_1.00-x Zn _x )TaO₃ were fabricated on (111)Pt/TiO₂/SiO₂/(100)Si substrate by a chemical solution deposition technique using metal-organic precursors. Dense films consisting of a ilumenite-type crystalline phase were deposited by spin coating on the substrates, followed by heat-treatment at 650°C for 5 min in air. The leakage current density of the LiTaO₃ film was reduced from approximately 10⁻⁴ to 10⁻⁶ A/cm² by substituting Zn²⁺ ions for Li⁺ ions in the LiTaO₃ films. Polarization–electric field hysteresis loop was improved significantly by partial substitution of Zn²⁺ for Li⁺ ions, which is based on the enhancement of electrical resistivity.     

Fabrication and morphology control of BaWO4 thin films by microwave assisted chemical bath deposition

Highly crystallized barium tungstate (BaWO₄) thin films with dumbbell-like, kernel-like, bowknot-like and cauliflower-like microstructure were synthesized from an aqueous solution containing barium nitrate, ethylenediamine tetraacetate acid disodium and sodium tungstate, via mild microwave assisted chemical bath deposition process. The resulting BaWO₄ films with different morphologies were characterized by X-ray diffraction spectrum, scanning electron microscope, Raman and photoluminescence spectra. The results indicate that the morphologies of final products significantly depend on the reaction conditions including the reaction time, the initial concentration of precursor reagent and the physicochemical characteristics of the substrates. Furthermore, the oriented aggregation mechanism is proposed as a possible formation mechanism of the films with specific morphologies.     

Evaporated thin films of insulating poly-(tetrabromo-p-phenylenediselenide)

It has been shown that thin insulating film at the interface transparent conductive oxide/organic electroluminescent film could improve the performance of organic electroluminescent diodes (OLED). Such insulating film can be inorganic or organic. Poly-(tetrabromo-p-phenylenediselenide) (PBrPDSe) has been proved to be an efficient insulating film in OLED. The properties of these evaporated PBrPDSe thin films have been systematically studied by IR absorption, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, electron spin resonance and optical transmission measurements. It is shown that, when the deposition temperature is kept below the decomposition temperature of the polymer, tetrabromo-p-phenylenediselenide molecule is preserved during the deposition process. However the polymer, which is insoluble in powder form, becomes soluble after deposition. It can be concluded that films are mainly composed of oligomers of tetrabromo-p-phenylenediselenide.The electrical properties of SnO₂/PBrPDSe/Al thin films structures have been studied. The current-voltage characteristics exhibit a rectifying behaviour with a forward direction corresponding to a positive bias of the transparent conductive oxide film, the SnO₂.     

Unexpected formation by pulsed laser deposition of nanostructured Fe/olivine thin films on MgO substrates

Olivine-type LiFePO₄ thin films were grown on MgO (1 0 0) substrates by pulsed laser deposition (PLD). The formation of an original nanostructure is evidenced by transmission electron microscopy measurements. Indeed, on focused ion beam prepared cross sections of the thin film, we observe, the amazing formation of metallic iron/olivine nanostructures. The appearance of such a structure is explained owing to a topotactic relation between the two phases as well as a strong Mg diffusion from the substrate to the film surface. Magnesium migration is thus concomitant with the creation of metallic iron domains that grow from the core of the film to the surface leading to large protuberances. To the best of our knowledge, this is the first report on iron extrusion from the olivine-type LiFePO₄.     

Tin colloids and metal-metal oxide films prepared by chemical liquid deposition. III

Colloids and thin metal-metal oxide films have been prepared by a method we call Chemical Liquid Deposition (CLD). The metal is evaporated to yield atoms which are solvated at liquid nitrogen temperature, and upon warming stable liquid colloidal solutions are formed. In the case of tin, the particle size of these colloids ranges between 200–500 Å. Zeta potentials were calculated by a Hückel approximation for most of these negatively charged particles. Upon solvent removal, colloidal particles coalesce to form films, which contain some residual solvent. The synthesis of colloids and films from Sn with acetone, 2-butanone, THF, ethanol, 2-propanol, DMF and DMSO is reported. FTIR, High Resolution Mass Spectrometry, Thermogravimetric Analyses (TGA) and Scanning Electron Microscopy (SEM) film characterization has been carried out. These studies indicate that solvents are incorporated into the films. The resistivity studies showed that they more behave as semiconductors than pure metals. TGA studies reveal that loss of weight occurs within 200–500°C. The films are very stable with 5–10% weight loss at 550°C. SEM reveals their surface morphology. Mössbauer gives information about oxidation states of some tin films.     

Epitaxial oxide thin films by pulsed laser deposition: Retrospect and prospect

Pulsed laser deposition (PLD) is a unique method to obtain epitaxial multi-component oxide films. Highly stoichiometric, nearly single crystal-like materials in the form of films can be made by PLD. Oxides which are synthesized at high oxygen pressure can be made into films at low oxygen partial pressure. Epitaxial thin films of highT _c cuprates, metallic, ferroelectric, ferromagnetic, dielectric oxides, superconductor-metal-superconductor Josephson junctions and oxide superlattices have been made by PLD. In this article, an overview of preparation, characterization and properties of epitaxial oxide films and their applications are presented. Future prospects of the method for fabricating epitaxial films of transition metal nitrides, chalcogenides, carbides and borides are discussed.     

Dielectric properties of Ca(Zr0.05Ti0.95)O3 thin films prepared by chemical solution deposition

Ca(Zr_0.05Ti_0.95)O₃ (CZT) thin films were grown on Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrates by the soft chemical method. The films were deposited from spin-coating technique and annealed at 928 K for 4 h under oxygen atmosphere. CZT films present orthorhombic structure with a crack free and granular microstructure. Atomic force microscopy and field-emission scanning electron microscopy showed that CZT present grains with about 47 nm and thickness about 450 nm. Dielectric constant and dielectric loss of the films was approximately 210 at 100 kHz and 0.032 at 1 MHz. The Au/CZT/Pt capacitor shows a hysteresis loop with remnant polarization of , and coercive field of 18 kV/cm, at an applied voltage of 6 V. The leakage current density was about at 3 V. Dielectric constant-voltage curve is located at zero bias field suggesting the absence of internal electric fields.     

Dispersion of functional tetraphenylporphyrin-ligated metal into ultra-thin flexible acrylate films. 1. Preparation of thin films

As functional metal complexes, copper phthalocyanine (CuPc) and Cobalt (II) meso-tetraphenylporphyrin (CoTPP) were chosen to prepare metal complex/polymer hybrid thin films which were prepared by metal complex sublimation and reactive monomer evaporation onto the glass substrate in the bell jar reactor in vacuum conditions. The polarized transmission micrograph images show that the film deposited at 80 °C contains uniformly dispersed tiny grains and the film deposited at 30 °C is amorphous and homogeneous. As the deposition rate increases, the crystalline clusters were found and were dispersed uniformly. Those crystalline clusters are not to be developed by recrystallization process. Deposited metal complex/acrylate hybrid thin films were in situ photopolymerized. The kinetics of photopolymerization was investigated by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The thickness of the films was about 200 nm. The reactive monomer acts as a solvent to avoid the recrystallization of metal complexes and to have two-compositional continuous phase. The percent of metal complex can be adjusted up to 60% by controlling the metal complex sublimation rate. A good achievement in the uniformity and continuity of the film matrix has been made and the recrystallization of metal complex in the hybrid films has not been observed.     

The determination of serum retinol by high performance liquid chromatography

A method for the quantitation of retinol in serum by normal phase high performance liquid chromatography is described. The mobile phase consists of a hexane/diethylether/methanol mixture with spectrophotometric detection. The sample preparation is similar to that described by other authors and involves protein precipitation followed by extraction and direct injection onto the chromatograph. Adequate sensitivity is achieved using 200 μl samples. The internal standard chosen is α-naphthol because of its spectral similarities to retinol and its greater stability than the commonly used retinyl esters. The method has been successfully applied to the clinical evaluation of a number of malabsorption syndromes for which it is preferred to the measurement of total carotenoids.     

Composite thin films of poly(phenylene oxide)/poly(styrene) and PPO/silver via vapor phase deposition

We report fabrication of thin (100～300 nm) poly(phenylene oxide) (PPO) films and their composites with poly (styrene) (PS) and silver (Ag) nanoparticles using a one‐step electron beam‐assisted vapor phase co‐deposition technique. Surface morphology and the structure of the deposited polymer thin film composites were characterized by FTIR, Raman, X‐ray spectroscopy, and contact angle measurements. As‐deposited PPO films and PPO/Ag composites were of porous nature and contrary to solvent casting techniques were free from nodular growth. In the case of PPO/PS thin film polymer composites, however, film morphology displayed nodular growth of PPO with nodule diameters of about ～200 nm and height of approximately 50 nm. Unique morphological changes on the porous PPO thin film surface were noticed at different Ag filling ratios. Further, the capacitance of PPO/Ag composites (<16 wt%) were measured under radio‐frequency conditions and they were functional up to 100 MHz with an average capacitance density of about 2 nF/cm². The fabricated PPO‐based composite systems are discussed for their potential applications including embedded capacitor technology. Copyright © 2008 John Wiley & Sons, Ltd.     

Fabrication of solid thin film electrolyte and LiCoO2 by aerosol flame pyrolysis deposition

Aerosol flame pyrolysis deposition method was applied to deposit the oxide glass electrolyte film and LiCoO₂ cathode for thin film type Li-ion secondary battery. The thicknesses of as-deposited porous LiCoO₂ and Li₂O–B₂O₃–P₂O₅ electrolyte film were about 6 μm and 15 μm, respectively. The deposited LiCoO₂ was sintered for 2 min at 700 °C to make partially densified cathode layer, and the deposited Li₂O–P₂O₅–B₂O₃ glass film completely densified by the sintering at 700 °C for 1 h. After solid state sintering process the thicknesses were reduced to approximately 4 μm and 6 μm, respectively. The cathode and electrolyte layers were deposited by continuous deposition process and integrated into a layer by co-sintering. It was demonstrated that Aerosol flame deposition is one of the good candidates for the fabrication of thin film battery.     

氧化银纳米粒子的制备及其动态受激荧光

采用真空蒸发沉积法和辉光放电氧化法,制备了粒径在5～30 nm之间的可控、空间分布均匀、高纯度的氧化银纳米薄膜,使薄膜成岛状生长和避免光照是制备过程中的两个关键问题.用XPS分析了Ag 3d和O 1s轨道的结合能,计算了银和氧的原子比,证明其成分为Ag2O,用XRD确定了氧化银纳米薄膜最强的衍射峰分别对应Ag2O的（111）、（110）、（200）、（211）晶面族.研究了这种薄膜在可见光波段的光吸收,计算得氧化银的禁带宽度为2.8 eV.在蓝光持续照射几分钟激活后,观察到了其中纳米粒子在蓝光激发下发黄光和绿光,在绿光激发下发红光的现象,这种光致发光具有动态“闪烁”的特点.提出了氧化银光分解引入缺陷能级（如Ag3O, Ag2＋O和Ag3＋O）新的理论模型并对此现象进行定性的解释.     

利用层层自组装技术制备聚电解质多层膜高效液相色谱固定相

以聚(乙烯-alt-马来酸)的苯乙胺衍生物与聚烯丙基胺盐酸盐为原料,通过层层自组装技术(LBL)在色谱硅胶表面交替沉积得到聚电解质多层膜高效液相色谱(HPLC)固定相;利用紫外光谱、红外光谱和元素分析研究了HPLC固定相的结构和组成.结果表明,聚电解质多层膜HPLC固定相被成功构筑在硅胶颗粒表面;制备的多层膜固定相可方便地用于6种芳香烃类及4种烷基苯类物质的分离分析.本文的研究结果说明LBL技术在制备HPLC固定相方面具有一定的应用价值.