Synthesis of ordered mesoporous zirconium phosphate films by spin coating and vapor treatments

Ordered mesoporous zirconium phosphate films were prepared on a silicon substrate by spin coating using a mixture of zirconium isopropoxide, triethyl phosphate, Pluronic P123 triblock copolymer, nitric acid, ethanol, and water. The spin-on film was consecutively treated with vapors of phosphoric acid and ammonia. The post-vapor treatments effectively enhanced the thermal stability of an ordered mesostructure when heated to 500 degrees C. XRD and TEM analyses show that the calcined zirconium phosphate film has a hexagonal structure with straight channels parallel to the film surface. The zirconium phosphate film exhibited high proton conductivity of 0.02 S/cm parallel to the film surface at 80% RH and 25 degrees C.     

Remarkable birefringence in a TiO2-SiO2 composite film with an aligned mesoporous structure

Mesoporous titania-silica composite films with highly aligned cylindrical pores are prepared by the sol-gel method using a substrate with structural anisotropy. The strong alignment effect of a rubbing-treated polyimide film on a substrate provides a narrow alignment distribution in the plane of the film regardless of the fast condensation rate of titania precursors. The collapse of the mesostructure upon the surfactant removal is effectively suppressed by the reinforcement of the pore walls with silica by exposing the as-deposited film to a vapor of a silicon alkoxide. The existence of a silica layer on the titania pore wall is proved from the distributions of Ti and Si estimated by the elemental analysis in high resolution electron microscopy. The obtained mesoporous titania-silica composite film exhibits a remarkable birefringence reflecting the highly anisotropic mesoporous structure and the high refractive index of titania that forms the pore wall. The Δn value estimated from the optical retardation and the film thickness is larger than 0.06, which cannot be achieved with the conventional mesoporous silica films with uniaxially aligned mesoporous structure even though the alignment of the pores in the films is perfect. These inorganic films with mesoscopic structural anisotropy will find many applications in the field of optics as phase plates with high thermal/chemical/mechanical stabilities.     

New benchmark for water photooxidation by nanostructured alpha-Fe2O3 films

Thin films of silicon-doped Fe2O3 were deposited by APCVD (atmospheric pressure chemical vapor deposition) from Fe(CO)5 and TEOS (tetraethoxysilane) on SnO2-coated glass at 415 degrees C. HRSEM reveals a highly developed dendritic nanostructure of 500 nm thickness having a feature size of only 10-20 nm at the surface. Real surface area determination by dye adsorption yields a roughness factor of 21. XRD shows the films to be pure hematite with strong preferential orientation of the [110] axis vertical to the substrate, induced by silicon doping. Under illumination in 1 M NaOH, water is oxidized at the Fe2O3 electrode with higher efficiency (IPCE = 42% at 370 nm and 2.2 mA/cm2 in AM 1.5 G sunlight of 1000 W/m2 at 1.23 VRHE) than at the best reported single crystalline Fe2O3 electrodes. This unprecedented efficiency is in part attributed to the dendritic nanostructure which minimizes the distance photogenerated holes have to diffuse to reach the Fe2O3/electrolyte interface while still allowing efficient light absorption. Part of the gain in efficiency is obtained by depositing a thin insulating SiO2 interfacial layer between the SnO2 substrate and the Fe2O3 film and a catalytic cobalt monolayer on the Fe2O3 surface. A mechanistic model for water photooxidation is presented, involving stepwise accumulation of four holes by two vicinal iron or cobalt surface sites.     

NH4PO3-SiO2复合电解质的溶胶凝胶法制备和导电性能

用溶胶凝胶法制备了复合固体电解质xNH₄PO₃-SiO₂(x=1，2，4)，并研究了该电解质在125～250 ℃范围内的导电性能。复合电解质的相结构分析表明，NH₄PO₃和SiO₂在溶胶凝胶法制备过程中没有发生化学反应;复合电解质的电导率随着NH₄PO₃含量增大而提高，并与NH₄PO     

Optical, electrical and dielectric properties of TiO2-SiO2 films prepared by a cost effective sol-gel process

Titanium dioxide (TiO(2)) and silicon dioxide (SiO(2)) thin films and their mixed films were synthesized by the sol-gel spin coating method using titanium tetra isopropoxide (TTIP) and tetra ethyl ortho silicate (TEOS) as the precursor materials for TiO(2) and SiO(2) respectively. The pure and composite films of TiO(2) and SiO(2) were deposited on glass and silicon substrates. The optical properties were studied for different compositions of TiO(2) and SiO(2) sols and the refractive index and optical band gap energies were estimated. MOS capacitors were fabricated using TiO(2) films on p-silicon (100) substrates. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics were studied and the electrical resistivity and dielectric constant were estimated for the films annealed at 200°C for their possible use in optoelectronic applications.     

Spectroscopic and electrical properties of SiO2 films prepared by simple and cost effective sol-gel process

Amorphous SiO2 thin films were prepared on glass and silicon substrates by cost effective sol-gel method. Tetra ethyl ortho silicate (TEOS) was used as the precursor material, ethanol as solvent and concentrated HCl as a catalyst. The films were characterized at different annealing temperatures. The optical transmittance was slightly increased with increase of annealing temperature. The refractive index was found to be 1.484 at 550 nm. The formation of SiO2 film was analyzed from FT-IR spectra. The MOS capacitors were designed using silicon (100) substrates. The current-voltage (I-V), capacitance-voltage (C-V) and dissipation-voltage (D-V) measurements were taken for all the annealed films deposited on Si (100). The variation of current density, resistivity and dielectric constant of SiO2 films with different annealing temperatures was investigated and discussed for its usage in applications like MOS capacitor. The results revealed the decrease of dielectric constant and increase of resistivity of SiO2 films with increasing annealing temperature.     

Atomistic simulation of the formation of nanoporous silica films via molecular chemical vapor deposition on nonporous substrates

To distinguish thin deposited film characteristics clearly from the influence of substrate morphological properties, the growth mechanism and the macroscale and nanoscale properties of nanoporous SiO(2) films deposited on nonporous silica (SiO(2)) substrates from chemical precursors Si(OH)(4) and TEOS (tetraethoxysilane) via low-pressure chemical vapor deposition are the primary targets of this study. This work employs a kinetic Monte Carlo (KMC) simulation method coupled to the Metropolis Monte Carlo method to relax the strained silica structure. The influence of the deposition temperature (473, 673, and 873 K) on the properties of the SiO(x) layers is addressed via analysis of the film growth rates, density profiles of the deposited thin films, pore size distributions, carbon depth profiles (with respect to TEOS), and voidage analysis for layers of different thicknesses (8-18 nm). A comparison of simulation with experimental results is also carried out.     

Boundary layer chemistry probed by in situ infrared spectroscopy during SiO2 deposition at atmospheric pressure from tetraethylorthosilicate and ozone

The deposition of silicon dioxide films at 450 degrees C was studied in quasi real time by probing the thermally activated boundary layer region near the growing surface during atmospheric pressure chemical vapor deposition (APCVD). Potential tetraethylorthosilicate (TEOS)/O(3) reaction products have been investigated in an attempt to clarify the reaction mechanism leading to the observed silanol deposition intermediates and delineate the film formation process. The organic products formed during the TEOS/O(3) reaction are acetic acid, formic acid, formaldehyde, carbon monoxide, carbon dioxide, and water. Quantitative methods are developed using FT-IR (Fourier transform infrared) spectroscopy during ozonation of TEOS at elevated temperatures. The measurement of gaseous alcohols of silicon alkoxides by FT-IR is demonstrated by application of an in situ methodology that probes the high-temperature region within the CVD environment. Partial least squares (PLS) Beer's law absorption models are used in determining relative TEOS, ozone, and ethoxysilanol levels during the reaction. The reaction order in TEOS is measured at 1.65 +/- 0.02 over a 0.9 Torr pressure range. Similarly, the ratio of ethoxysilanol formed versus the amount of ozone consumed is ca. 1:3. A radical chain oxidative mechanism involving direct reaction of TEOS and ozone is proposed for formation of highly reactive silanol film growth intermediates.     

Synthesis of 3D pore mesostructured silica films by vapor infiltration of tetraethoxysilane

Nonionic alkyl poly(oxyethylene) surfactants (Brij 56) films on a silicon substrate were treated with a tetraethoxysilane (TEOS) vapor. Mesostructured silica films were formed through a nano-phase transition under the infiltration of TEOS into the surfactant films. It was found that the calcined film had a 3D pore structure from the field emission scanning electron microscope (FE-SEM) observations in a different orientation. Grazing angle of incidence small angle X-ray scattering (GISAXS) measurement results showed that the symmetry of the film was an Fmmm space group oriented with the (010) plane parallel to the surface. The ordered structure of the films showed higher thermal stability than the films prepared by a conventional solvent-evaporation method.     

Nano-architectural silica thin films with two-dimensionally connected cagelike pores synthesized from vapor phase

Novel mesostructured silica thin films were prepared on a Si substrate by a vapor-phase synthesis. Vapor of tetraethoxysilane (TEOS) was infiltrated into a surfactant film consisting of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer. Nanophase transition from a lamellar structure to a two-dimensional cage structure of a silica-surfactant nanocomposite was found under vapor infiltration. The rearrangement into the cage structure implies high mobility of the silica-surfactant composites in solid phase. The silica thin films have two-dimensionally connected cagelike mesopores and are isotropic parallel to the film surface. The structure of pores of the films is advantageous for next-generation low-k films. The mesoporous structure has a large lattice parameter d of approximately 102 A, silica layer thickness of approximately 58 A, pillar diameter in the middle of approximately 60 A, pore size of approximately 72 A, BET surface area of approximately 729 m(2)/g, and pore volume of approximately 1.19 cm(3)/g. The films synthesized by the vapor infiltration show a lower concentration of residual Si-OH groups compared to the films prepared by a conventional sol-gel method. The films show high thermal stability up to 900 degrees C and high hydrothermal stability. This method is a simpler process than conventional sol-gel techniques and attractive for mass production of a variety of organic-inorganic composite materials and inorganic porous films.     

Boundary effects on the electrical conductivity of pure and doped cerium oxide thin films

Thin films of CeO(2) (both nominally pure and 10 mol% gadolinium-doped) grown via pulsed-laser deposition were studied. The electrical conductivity of the samples was measured as a function of thickness, temperature and oxygen partial pressure (pO(2)) using impedance spectroscopy. As expected, undoped CeO(2) exhibits electronic conductivity (with activation energy between 1.4 and 1.6 eV) whereas the highly doped samples are oxygen vacancy conductors (activation energy around 0.7 eV for epitaxial films). In order to investigate the influence of the nature of the substrate the thin films were grown on two different substrates, Al(2)O(3) (0001) and SiO(2) (0001), and compared. While the films grown on SiO(2) exhibit a microstructure characterized by columnar grains, the films grown on Al(2)O(3) are epitaxial. Notably, for films on both substrates the conductivity and activation energy vary with film thickness and exhibit remarkable differences when the films on different substrates are compared. In the case of the polycrystalline films (SiO(2) substrate), the space charge layer effects of the grain boundaries dominate over the substrate-film interface effect. In the case of the epitaxial films (Al(2)O(3) substrate), a small interface effect, probably due to a space charge layer or structural strain, is observed.     

Hydrophilicity/porous structure-tuned, SiO2/polyetherimide-coated polyimide nonwoven porous substrates for reinforced composite proton exchange membranes

Porous substrate-reinforced composite proton exchange membranes have drawn considerable attention due to their promising application to polymer electrolyte membrane fuel cells (PEMFCs). In the present study, we develop silica (SiO(2)) nanoparticles/polyetherimide (PEI) binders-coated polyimide (PI) nonwoven porous substrates (referred to as "S-PI substrates") for reinforced composite membranes. The properties of S-PI substrates, which crucially affect the performance of resulting reinforced composite membranes, are significantly improved by controlling the hygroscopic SiO(2) particle size. The 40 nm S-PI substrate (herein, 40 nm SiO(2) particles are employed) shows the stronger hydrophilicity and highly porous structure than the 530 nm S-PI substrate due to the larger specific surface area of 40 nm SiO(2) particles. Based on the comprehensive understanding of the S-PI substrates, the structures and performances of the S-PI substrates-reinforced composite membranes are elucidated. In comparison with the 530 nm S-PI substrate, the hydrophilicity/porous structure-tuned 40 nm S-PI substrate enables the impregnation of a large amount of a perfluorosulfonic acid ionomer (Nafion), which thus contributes to the improved proton conductivity of the reinforced Nafion composite membrane. Meanwhile, the reinforced Nafion composite membranes effectively mitigate the steep decline of proton conductivity with time at low humidity conditions, as compared to the pristine Nafion membrane. This intriguing finding is further discussed by considering the unusual features of the S-PI substrates and the state of water in the reinforced Nafion composite membranes.     

钛金属有机物热解制备TiO2-SiO2复合膜及其光催化活性研究

混有一定量SiO_2溶胶的钛金属有机化合物膜液通过旋液成膜法制备前驱物膜 ，经热解得到TiO_2-SiO_2复合膜。于610 ℃焙烧15min所得复合膜(Ti:Si=9:1)经 SEM，XRD，UV-vis和XPS研究表明，膜面由30 nm * 200 nm大小的晶体粒子组成， 结构致密，膜厚约200 nm，其可见光透过率为玻璃基质的80%，膜表面Ti~(3+)OH~- 的比值为1.06。对不同SiO_2含量的膜液凝胶进行DSC分析显示，少量的SiO_2就能 显著提高TiO_2锐钛矿型晶相的形成温度。膜的光催化活性研究表明一定量的Fe~ (3+)有利于提高膜的光催化活性，但是如果以氯化物的形式加入则对光催化反应不 利，铬的氯化物同样如此。另外，在钛金属有机物热解制备TiO_2-SiO_2复合膜中 ，溶胶SiO_2不利于光催化反应，但是它可以改善膜的耐磨性。     

TiO2/SiO2纳米薄膜的光催化活性和亲水性

通过sol gel工艺在钠钙玻璃表面制备了均匀透明的TiO2/SiO2复合纳米薄膜.实验结 果表明: 当SiO2添加量较高时, TiO2/SiO2复合纳米薄膜的光催化活性明显降低;当SiO2添加 量较低时,TiO2/SiO2复合薄膜的光催化活性无明显变化.在TiO2薄膜中添加SiO2,可以抑制薄 膜中TiO2晶粒的长大,同时薄膜表面的羟基含量增加, 水在复合薄膜表面的润湿角下降, 亲 水能力增强.当SiO2含量为10％－20％（摩尔分数）时获得了润湿角为0°的超亲水性薄膜.     

Diffusion reaction of oxygen in HfO2/SiO2/Si stacks

We study the oxidation mechanism of silicon in the presence of a thin HfO2 layer. We performed a set of annealing in 18O2 atmosphere on HfO2/SiO2/Si stacks observing the 18O distribution in the SiO2 layer with time-of-flight secondary ion mass spectrometry (ToF-SIMS). The 18O distribution in HfO2/SiO2/Si stacks upon 18O2 annealing suggests that what is responsible for SiO2 growth is the molecular O2, whereas no contribution is found of the atomic oxygen to the oxidation. By studying the dependence of the oxidation velocity from oxygen partial pressure and annealing temperature, we demonstrate that the rate-determining step of the oxidation is the oxygen exchange at the HfO2/SiO2 interface. When moisture is chemisorbed in HfO2 films, the oxidation of the underlying silicon substrate becomes extremely fast and its kinetics can be described as a wet silicon oxidation process. The silicon oxidation during O2 annealing of the atomic layer deposited HfO2/Si is fast in its early stage due to chemisorbed moisture and becomes slow after the first 10 s.     

三甲基氯硅烷对纳米多孔二氧化硅薄膜的修饰

以正硅酸乙酯为先驱体,采用溶胶-凝胶法,结合旋转涂胶、超临界干燥工艺在硅片上制备了纳米多孔SiO2薄膜.用三甲基氯硅烷(TMCS)对该SiO2薄膜进行了表面修饰,采用FTIR、TG-DTA、AFM和椭偏仪等方法研究了TMCS修饰前后薄膜的结构、形貌、厚度与介电常数等性能.超临界干燥后的SiO2薄膜含有Si－O－Si与Si－OR结构,呈疏水性.在空气中250 ℃以上热处理后SiO2薄膜因含有Si－OH而呈吸水性. TMCS修饰后的SiO2薄膜在温度不高于450 ℃时可保持其疏水性和多孔结构. SiO2薄膜经TMCS修饰后基本粒子和孔隙尺寸增大,孔隙率提高,介电常数可降低至2.5以下.     

A self-ordered, crystalline glass, mesoporous nanocomposite with high proton conductivity of 2 x 10(-2) S cm-1 at intermediate temperature

We prepared a TiO2-P2O5 self-ordered, crystalline glass, mesoporous nanocomposite (CGMN) with water-holding capacity at an intermediate temperature region (130-200 degrees C). This TiO2-P2O5 CGMN showed the high proton conductivity of 2 x 10-2 S cm-1 at 160 degrees C under fully saturated humidification conditions (100% RH). Additionally, these conductivities were stable at intermediate temperature conditions. The TiO2-P2O5 CGMN may have a potential not only for the fuel cell electrolytes operated at intermediate temperature conditions but also for electrochemical devices, including electrochromic displays, chemical sensors, lithium rechargeable batteries, and others.     

Kinetics of Photocatalytic Degradation of Formic Acid over Silica Composite Films Based on Polyoxometalates

The composite films, XW11O39^n-/SiO2,(X refers to Si,Ge or P,respectively) were prepared by tetraethoxysilane (TEOS) hydrolysis sol-gel method via spin-coating technique. Formation of the composite films is due to strong chemical reaction of organic silanol group with the surface oxygen atoms of XW11O39^n-, resulted in the saturation of the surface of the lacunary polyoxometalates (POMs). Therefore,the coordination structural model of the films was proposed. As for the films, retention of the primary Keggin structure was confirmed by UV-vis, FT-IR spectra and MAS NMR. The surface morphology of the films was characterized by SEM, indicating that the film surface is relatively uniform, and the layer thickness is in the range of 250-350nm. Aqueous formic acid (FA) (0-20mmol/L) was degraded into CO2 and H2O by irradiating the films in the near-UV area. The results show that all the films have photocatalytic activities and the degradation reaction follows Langmuir-Hinshelwood first order kinetics.     

脉冲激光沉积非晶态Ni-V2O5 复合薄膜及其电化学性能研究

首次报道了用355 nm脉冲激光沉积非晶态Ni-V2O5复合薄膜电极的电化学性能.采用不同摩尔比的NixV2O5 靶(x=0.1,0.3,0.5),在不同的基片温度(Ts)和O2气压力下制备了Ni-V2O5复合薄膜.XRD 和SEM测定表明, 在不锈钢基片上, Ts=300℃和氧气压力为14 Pa沉积0.5 h得到的是非晶态的Ni-V2O5薄膜.将此非晶态的Ni0.3V2O5薄膜电极用于锂电池的正极,与纯V2O5薄膜相比,不仅具有良好的放电速率性能和高的比容量,而且其充放电循环稳定性优异.该薄膜电极在放电速率为20 C时测得的比容量达200 mAh/g,并经1000次以上的充放电循环无明显的衰减.     

Atomic layer deposition of tungsten(III) oxide thin films from W2(NMe2)6 and water: precursor-based control of oxidation state in the thin film material

The atomic layer deposition of W2O3 films was demonstrated employing W2(NMe2)6 and water as precursors with substrate temperatures between 140 and 240 degrees C. At 180 degrees C, surface saturative growth was achieved with W2(NMe2)6 vapor pulse lengths of >/=2 s. The growth rate was about 1.4 A/cycle at substrate temperatures between 140 and 200 degrees C. Growth rates of 1.60 and 2.10 A/cycle were observed at 220 and 240 degrees C, respectively. In a series of films deposited at 180 degrees C, the film thicknesses varied linearly with the number of deposition cycles. Time-of-flight elastic recoil analyses demonstrated stoichiometric W2O3 films, with carbon, hydrogen, and nitrogen levels between 6.3 and 8.6, 11.9 and 14.2, and 4.6 and 5.0 at. %, respectively, at substrate temperatures of 160, 180, and 200 degrees C. The as-deposited films were amorphous. Atomic force microscopy showed root-mean-square surface roughnesses of 0.7 and 0.9 nm for films deposited at 180 and 200 degrees C, respectively. The resistivity of a film grown at 180 degrees C was 8500 microhm cm.