Home About us Contact
|
Home About us Contact | ||
|
|
||
SiO2 Film (sio2 + film)
Selected AbstractsSynthesis of Al2O3,SiO2 Films by Ar/O2 Plasma-Enhanced CVD from Alkoxide Precursors,CHEMICAL VAPOR DEPOSITION, Issue 5 2006Y. Li Amorphous Al2O3, SiO2, and Al2O3,SiO2 composite films have been produced at 800,°C from alkoxide solution precursors by liquid-injection oxygen plasma enhanced CVD. The films' structures and morphologies are affected by the feed rate of the liquid precursor and their compositions can be controlled by adjusting the Si/Al ratios in the starting source. Steel substrates coated with the above films gained excellent protection when they were exposed to high temperature atmosphere containing KCl vapor. [source] Chitosan Hydrogel-Capped Porous SiO2 as a pH Responsive Nano-Valve for Triggered Release of InsulinADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Jianmin Wu Abstract A pH responsive, chitosan-based hydrogel film is used to cap the pores of a porous SiO2 layer. The porous SiO2 layer is prepared by thermal oxidation of an electrochemically etched Si wafer, and the hydrogel film is prepared by reaction of chitosan with glycidoxypropyltrimethoxysilane (GPTMS). Optical reflectivity spectroscopy and scanning electron microscopy (SEM) confirm that the bio-polymer only partially infiltrates the porous SiO2 film, generating a double layer structure. The optical reflectivity spectrum displays Fabry,Pérot interference fringes characteristic of a double layer, which is characterized using reflective interferometric Fourier transform spectroscopy (RIFTS). Monitoring the position of the RIFTS peak corresponding to the hydrogel layer allows direct, real-time observation of the reversible volume phase transition of the hydrogel upon cycling of pH in the range 6.0,7.4. The swelling ratio and response time are controlled by the relative amount of GPTMS in the hydrogel. The pH-dependent volume phase transition can be used to release insulin trapped in the porous SiO2 layer underneath the hydrogel film. At pH 7.4, the gel in the top layer effectively blocks insulin release, while at pH 6.0 insulin penetrates the swollen hydrogel layer, resulting in a steady release into solution. [source] New supplying evaporation precursor method with CVDHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2009Motohiro Oshima Abstract We propose a novel system of chemical vapor deposition (CVD), i.e., flash boiling spray CVD (SF-CVD) to eliminate several kinds of problems, such as the decomposition of precursors in the supply line and evaporator. In this method, liquid precursors are supplied directly to the vacuum chamber through an injector, just like fuel for an automobile engine, without any vaporizers, so as to induce an unsteady and intermittent flash boiling spray in the chamber. However, it is necessary to keep the lowest ambient pressure possible because the saturated vapor pressure of the precursors is very low. Thus, this is very useful for modifying the saturated vapor pressure of the precursors. A technique of lowering the vaporization pressure is proposed by mixing a more saturated vapor-pressure organic solvent with a precursor. To determine the principles underlying FS-CVD, we first formed SiO2 film on the Si substrate. A mixed solution of tetraethylorthosilicate (TEOS) and n-pentane was used as the mixing solution. The film thickness distribution of SiO2 film on a 100-mm-diameter Si wafer was ±4% using this method. Furthermore, this method enabled us to control film with various thicknesses by optimizing the injection duration, cycle, and injection cycle per second. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20235 [source] Development of flame retardancy properties of new halogen-free phosphorous doped SiO2 thin films on fabricsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Aysun Cireli Abstract In this study, flame retardancy properties of fabrics treated with phosphorous (P) doped and undoped SiO2 thin films were developed by sol,gel technique. As to this aim, P-doped and undoped SiO2 film were coated on cotton fabric from the solutions prepared from P, Si-based precursors, solvent, and chelating agent at low temperature in air using sol,gel technique. To determine solution characteristics, which affect thin film structure, turbidity, pH values, and rheological properties of the prepared solutions were measured using a turbidimeter, a pH meter, and a rheometer machines before coating process. The thermal, structural, and microstructural characterization of the coating were done using differential thermal analysis/thermograviometry, fourier transform infrared spectroscopy, X-ray diffractometry, and scanning electron microscopy. In addition, tensile strength, wash fastness, flame retandancy, and lightness properties of the coated fabrics were determined. To compensate the slight loss of tensile strength of samples, which occurred at the treated fabrics with P-doped Si-based solutions, the cotton fabrics were coated with polyurethane films during second step. In conclusion, the flame retardant cotton fabric with durability of washing as halogen-free without requiring after treatment with formaldehyde was fabricated using sol,gel processing for the first time. Moreover the cotton fabrics, which were treated with P-doped Si-based solutions and then coated with polyurethane at second step, still has got nonflammable property. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] High-Temperature Stability of Lanthanum Orthophosphate (Monazite) on Silicon Carbide at Low Oxygen Partial PressuresJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Michael K. Cinibulk The stability of lanthanum orthophosphate (LaPO4) on SiC was investigated using a LaPO4 -coated SiC fiber at 1200°,1400°C at low oxygen partial pressures. A critical oxygen partial pressure exists below which LaPO4 is reduced in the presence of SiC and reacts to form La2O3 or La2Si2O7 and SiO2 as the solid reaction products. The critical oxygen partial pressure increases from ,0.5 Pa at 1200°C to ,50 Pa at 1400°C. Above the critical oxygen partial pressure, a thin SiO2 film, which acts as a reaction barrier, exists between the SiC fiber and the LaPO4 coating. Continuous LaPO4 coatings and high strengths were obtained for coated fibers that were heated at or below 1300°C and just above the critical oxygen partial pressure for each temperature. At temperatures above 1300°C, the thin LaPO4 coating becomes morphologically unstable due to free-energy minimization as the grain size reaches the coating thickness, which allows the SiO2 oxidation product to penetrate the coating. [source] Kinetics and Products of Molybdenum Disilicide Powder OxidationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2002Yuntian T. Zhu In this study, we investigated the kinetics and products of the oxidation of MoSi2 powder with an average particle size of 1.6 ,m at 900°, 1000°, and 1100°C, using a small sample size of 0.5 g. Such a small sample size allowed us to minimize the effect of oxygen transportation through the powder volume, while maintaining a good relative weighing accuracy. X-ray diffraction of oxidized samples indicated the formation of Mo5Si3 and Mo metal. Analysis of the oxidation kinetics suggested that gaseous MoO3 formed initially and amorphous SiO2 film later. The oxidation kinetics and products observed in this study differ from those reported in an early study, in which a larger sample size was used. [source] Electrical characteristics of temperature-difference liquid phase deposited SiO2 on GaN with (NH4)2Sx treatmentPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2008Ming-Kwei Lee Abstract The characteristics of a SiO2 film grown on (NH4)2Sx treated GaN by temperature-difference liquid phase deposition were investigated. Hydrofluorosilicic acid and boric acid were used as deposition solutions. For GaN without the (NH4)2Sx treatment, an Al/SiO2/GaN MOS diode shows poor electrical characteristics due to the native oxides existing at the interface. With (NH4)2Sx treatment of GaN, a stable sulfide-terminated surface is obtained and the leakage current density of SiO2/GaN is improved from 6.15 × 10,4 A/cm2 to 2.08 × 10,5 A/cm2 at the electric field of 2 MV/cm. The effective oxide charges decrease from 6.09 × 1011 C/cm2 to 2.23 × 1011 C/cm2. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Enhanced performance by inserting ultrathin SiO2 layer in organic light-emitting devicesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2007Lianbin Niu Abstract Improved performance of organic light-emitting devices (OLEDs) has been obtained by insertion of an ultrathin film of silicon oxide (SiO2) at the interface of 8-hydroxyquinoline aluminum (Alq3) and N,N ,-bis(1-naphthyl)- N,N ,-diphenyl-1,1,-biphenyl-4,4,-diamine (NPB) layers. When a 1.0 nm SiO2 film was inserted, for an unoptimized indium,tin oxide (ITO)/NPB/SiO2/Alq3/Al device, the current efficiency was as high as 7.35 cd/A. Compared with conventional devices, a higher efficiency has been achieved. The mechanism of performance enhancement is discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] HVPE Growth of GaN on a GaN Templated (111) Si SubstratePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003Y. Honda Abstract The hydride vapor phase epitaxial (HVPE) growth of GaN was attempted on a (111) Si substrate. In order to suppress the chemical reaction of the Si at high temperatures, the surface of the substrate was covered by a thin SiO2 film or GaN pyramids which were grown by selective metalorganic vapor phase epitaxy (MOVPE). The GaN pyramids served as the seeds for the following HVPE growth of GaN. Uniform layer of 12 ,m thick wurtzite GaN was achieved successfully. The full width at half maximum (FWHM) of (0004) X-ray rocking curve was 450 arcsec. The cathode luminescence (CL) spectra at 4.2 K exhibited a strong band edge emission peak of which FWHM was as broad as 30.3 meV. [source] Scanning Probe Parallel Nanolithography with Multiprobe Cantilever Array Fabricated by Bulk Silicon MicromachiningIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2008Hensy Gandjar Non-member Abstract This work describes a scanning probe parallel nanolithography (SPNL) technique for high throughput in nanometric patterning on single-crystal silicon (SCS) substrates. Two types of multiprobe cantilever arrays used for SPNL were fabricated by conventional micromachining. All the probes mounted on the free end of each cantilever were made of quasitrihedral pyramidal shape composed of (311) and (411) planes using the originally designed mask. Negative and positive types of nanolithography were performed on the basis of field-enhanced anodization and self-assembled monolayer mask techniques, respectively, and they succeeded in drawing a number of nanometric patterns of silicon dioxide (SiO2) on SCS substrates. After anisotropic wet etching of the SCS substrates using the SiO2 films as the mask material, we were also able to fabricate nanowires and nanogrooves. The effects of the applied voltage and scan time of cantilever arrays on wire and groove dimensions were systematically examined by atomic force microscopy (AFM) observations. An optimum condition for the parallel SPNL is proposed on the basis of this research. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Aerosol Catalyst Particles for Substrate CVD Synthesis of Single-Walled Carbon Nanotubes,CHEMICAL VAPOR DEPOSITION, Issue 6 2006P. Queipo Abstract Individual single-walled carbon nanotubes (SWCNTs) were grown by a CVD method on thin SiO2 films using iron and carbon monoxide as the catalyst material and the carbon source, respectively. Catalyst particles were produced via physical vapor deposition (PVD) as an aerosol using a hot-wire particle generator and then deposited by two different approaches. Particles collected onto the substrates by diffusion inside the reactor led to the production of large diameter SWCNTs (,3,6,nm) with lengths up to 30,,m. An outside deposition, via electrostatic precipitator, resulted in the synthesis of longer SWCNTs (,,50,,m) with smaller diameters (<,2,nm). [source] Evidence for a Size-Selective Adsorption Mechanism on Oxide Surfaces: Pd and Au atoms on SiO2/Mo(112)CHEMPHYSCHEM, Issue 10 2008Stefan Ulrich Sieving single atoms: The binding of single metal atoms to thin SiO2 films grown on Mo(112) depends on the size of the adatom. While Pd atoms are able to pass the nanopores in the silica network (see figure) and strongly bind to the Mo,SiO2 interface, Au atoms are too big for a penetration and interact only with line defects in the oxide surface. [source] | ||||||||||||||||