Home About us Contact
|
Home About us Contact | ||
|
|
||
SiO2 Layer (sio2 + layer)
Selected AbstractsHybrid Sputtering-Remote PECVD Deposition of Au Nanoparticles on SiO2 Layers for Surface Plasmon Resonance-Based Colored CoatingsPLASMA PROCESSES AND POLYMERS, Issue 8 2010Haile Takele Beyene Abstract In this paper, a hybrid system consisting of metal nano-particles dispersed on the surface of a dielectric layer is presented: a remote Expanding Thermal Plasma CVD system is used for the deposition of the inorganic (i.e. SiO2) layers from hexamethyldisiloxane/oxygen mixtures in combination with an rf magnetron sputtering tool for the deposition of metallic (i.e. gold) nanoparticles on top of the SiO2 layers. The optical properties of the Au/SiO2 layers have been investigated by means of UV-VIS-NIR variable angle spectroscopic ellipsometry. Rutherford backscattering and transmission electron microscopy were used to determine the film density, the nanoparticle size and its distribution, respectively. The uniform distribution of gold nanoparticles on the surface of the SiO2 layers allows obtaining red- to blue- colored coatings as a consequence of the shift of the surface plasmon resonance band to higher wavelengths, caused by an increase in size of nanoparticles and metal surface coverage. [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] Effects of High Water-Vapor Pressure on Oxidation of Silicon Carbide at 1200°CJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2003Peter F. Tortorelli The oxidation of SiC at 1200°C in a slowly flowing gas mixture of either air or air + 15 vol% H2O at 10 atm (1 MPa) was studied for extended times to examine the effects of elevated water-vapor pressure on oxidation rates and microstructural development. At a water-vapor pressure of 1.5 atm (150 kPa), distinct SiO2 scale structures were observed on the SiC; thick, porous, nonprotective cristobalite scales formed above a thin, nearly dense vitreous SiO2 layer, which remained constant in thickness with time as the crystalline SiO2 continued to grow. The pore morphology of the cristobalite layer differed depending on the type of SiC on which it was grown. The crystallization and growth rates of the cristobalite layer were significantly accelerated in the presence of the high water-vapor pressure and resulted in rapid rates of SiC surface recession that were on the order of what is observed when SiO2 volatility is rate controlling at high gas-flow velocities (30 m/s). The recession process can be described by a paralinear kinetic model controlled by the conversion of dense vitreous SiO2 to porous, nonprotective SiO2. [source] Surface Plasmon-coupled Polarized Emission of N-Acetyl- l -Trytophanamide,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2004Ignacy Gryczynski We report an observation of ultraviolet (UV) surface plasmon-coupled emission (SPCE) of N-acetyl- l -tryptophanamide (NATA). The sample was spin coated from poly(vinyl alcohol) (PVA) solution on 20 nmaluminium film deposited on a quartz substracte. The directional UV SPCE occurs within a well-defined narrow angle at 52dG from the normal to the coupling hemicylinder quartz prism. The NATA directional emission is highly p polarized as expected for surface plasmon-coupled radiation. The 10 nm protective SiO2 layer deposited on top of the aluminum film significantly neutralized the fluorophore quenching by the metal surface. SPCE of NATA demonstratees a remarkable intrinsic dispersive property,the maximum of the emission spectrum depends on the observation angle. The efficient spectral resolution of SPCE can be used in the construction of miniaturized spectrofluorometers. The observation of SPCE of tryptophan opens a new possibility for the study of many unlabeled proteins with the technique complementary to surface plasmon resonance analysis. [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] Tunneling current in gate dielectric stack in sub-45 nanometer CMOS devicesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2009Hitender Kumar Tyagi Abstract Direct tunneling current through dual layer SiO2/high-K dielectric structures are investigated for substrate injection. Correlation of dielectric constants and band offsets with respect to silicon has been taken into consideration in order to identify possible materials to construct these devices. The direct tunneling current in oxide/high-K dielectric structures with equivalent oxide thickness (EOT) of 2.0 nm can be significantly lower than that through single layer oxides of the same thickness. Various structures and materials of high-K stacks of interest have been examined and compared to access the reduction of gate current in these structures. It is estimated that HfO2/SiO2 dual stack structure can reduce gate leakage current by four orders of magnitude as compared with pure SiO2 layer of same EOT. The importance of interfacial layer in dual stack structure is high-lighted for the reduction of gate leakage current. The present approach is capable of modeling high-K stack structures consisting of multiple layers of different dielectrics (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Photoluminescence spectroscopy and transport electrical measurements reveal the quantized features of Si nanocrystals embedded in an ultra thin SiO2 layerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2007C. Dumas Abstract In this paper, we have investigated the quantized charging features revealed by nanometer scale devices containing a 2D array of Si nanoparticles (nps) embedded into a SiO2 layer. The Si nps were synthesized by ultra low energy ion implantation and annealing under slightly oxidizing ambient. The structural characteristics of the material (oxide thicknesses, nps size and density) have been studied by Transmission Electron Microscopy (TEM) and Energy Filtered TEM (EFTEM). Moreover, photoluminescence (PL) spectroscopy and electrical I(V) measurements using a MOS capacitor addressing only a few nps have been performed at room temperature. It is observed that, as the oxidizing annealing temperature increases, the nps size decreases and the oxide quality is restored. These features appear on the PL spectra as a blue shift of the PL red band linked to quantum confinement into nps and on the I(V) characteristics as an increase of the voltage peak width and a decrease of the main current background. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Low interface state density AlGaN/GaN MOSHFETs with photochemical vapor deposition SiO2 layersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003C. K. Wang Abstract High quality SiO2 was successfully deposited onto AlGaN by photo chemical vapor deposition (photo-CVD) using D2 lamp as the excitation source. It was found that the interface state density was only 1.1 × 1011 cm,2 eV,1. AlGaN/GaN metal,oxide,semiconductor heterojunction field effect transistors (MOSHFETs) were also fabricated with such photo-CVD oxide as the insulating layer. Compared with AlGaN/GaN metal,semiconductor HFETs (MESHFETs) with similar structure, it was found that we could reduce the gate leakage current by more than four orders of magnitude by inserting the 32 nm-thick photo-CVD SiO2 layer between AlGaN/GaN and gate metal. With a 1 ,m gate length, it was found that room temperature saturated Ids, maximum gm and gate voltage swing (GVS) of the fabricated nitride-based MOSHFET are 800 mA/mm, 86 mS/mm and 9 V, respectively. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The Atomic Layer Deposition of HfO2 and ZrO2 using Advanced Metallocene Precursors and H2O as the Oxygen Source,CHEMICAL VAPOR DEPOSITION, Issue 11-12 2008Charles L. Dezelah IV Abstract The atomic layer deposition (ALD) of HfO2 and ZrO2 thin films is investigated using (MeCp)2HfMe2, (MeCp)2Hf(OMe)(Me), (MeCp)2ZrMe2, and (MeCp)2Zr(OMe)(Me) as the precursors at deposition temperatures between 300 and 500,°C, with water vapor as the oxygen source. A self-limiting growth mechanism is confirmed at 350,°C for all the metal precursors examined. The processes provide nearly stoichiometric HfO2 and ZrO2 films with carbon and hydrogen concentrations below 0.5 and 1.0 at.-%, respectively, for representative samples. All films are polycrystalline as deposited, and possess a thin interfacial SiO2 layer. The capacitance-voltage (C - V) and current density-voltage (I - V) behavior is reported and discussed for capacitor structures containing films from this study. [source] Density Investigation by X-ray Reflectivity for Thin Films Synthesized Using Atmospheric CVD,CHEMICAL VAPOR DEPOSITION, Issue 9-10 2008Shinichi Kishimoto Abstract The density of hafnia and titania films is investigated by an X-ray reflectivity (XRR) analysis using an X-ray diffractometer equipped with a relatively low power X-ray source. Several films are prepared using a CVD technique operated under atmospheric pressure. The XRR profile of the hafnia films is obtained, and fitted with the assumption of the existence of an HfSiO intermediate layer on the Si substrate with a SiO2 layer. The density of the hafnia films is lower than that of the bulk crystal. On the other hand, the XRR profile of the titania films on the glass substrate can be fitted using a seven-lamella model. The film density of titania is also lower than that of the bulk crystal. XRR analysis may become a powerful weapon to determine not only the structure model but also the crystallinity of each layer. [source] Oxide layer dissolution in Si/SiOx/Si wafer bonded structuresCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2009N. Zakharov Abstract The evolution of the interfaces of hydrophilic-bonded Si wafers and the corresponding low-angle twist boundary have been analysed in relation to thermal annealing and their relative crystallographic orientation. Two orientation relationships were investigated: Si<001>/Si<001> and Si<001>/Si<110>, where the interfaces are seperated by thin native SiO2 layers. The interfaces were analysed by TEM and STEM/EELS. It is found that the decomposition rate of the intermediate oxide layer and the formation of a Si(Si bonded interface depend very much on the lattice mismatch and on the twist angle. The velocity of the dissolution of the thin oxide layers and the formation of Si(Si bonds at the bonding interface depend on the orientation relations of the corresponding wafers. The processes of interface fusion and the dissolution of oxide layer are discussed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electron beam induced defects in Ge-implanted SiO2 layersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005Roushdey Salh Abstract Scanning electron microscopy (SEM) and cathodoluminescence (CL) have been used to investigate the irradiation-sensitive defect structure of pure and Ge+ -implanted amorphous silicon dioxide layers. CL emission spectra at specimen temperatures between liquid nitrogen (LNT) and room temperature (RT) are identified with particular defect centers including the nonbridging oxygen-hole center (NBOHC: ,Si,O,) associated with the red luminescence at 650 nm (1.9 eV), the self trapped exciton (STE) with the yellow-green luminescence at 580 nm (2.1 eV) and the Si related oxygen deficient center (SiODC) with the blue (460 nm; 2.7 eV) and ultraviolet UV band (295 nm; 4.2 eV). In Ge doped SiO2 an additional emission band is identified at (410 nm; 3.1 eV). This band corresponds to the Ge related oxygen deficient center (GeODC). The annealing process of Ge+ -implanted layer leads first to a strong increase of the violet luminescence due to formation of Ge dimers, trimers and higher aggregates, finally to destruction of the luminescence centers by further growing to Ge nanoclusters. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Low interface state density AlGaN/GaN MOSHFETs with photochemical vapor deposition SiO2 layersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003C. K. Wang Abstract High quality SiO2 was successfully deposited onto AlGaN by photo chemical vapor deposition (photo-CVD) using D2 lamp as the excitation source. It was found that the interface state density was only 1.1 × 1011 cm,2 eV,1. AlGaN/GaN metal,oxide,semiconductor heterojunction field effect transistors (MOSHFETs) were also fabricated with such photo-CVD oxide as the insulating layer. Compared with AlGaN/GaN metal,semiconductor HFETs (MESHFETs) with similar structure, it was found that we could reduce the gate leakage current by more than four orders of magnitude by inserting the 32 nm-thick photo-CVD SiO2 layer between AlGaN/GaN and gate metal. With a 1 ,m gate length, it was found that room temperature saturated Ids, maximum gm and gate voltage swing (GVS) of the fabricated nitride-based MOSHFET are 800 mA/mm, 86 mS/mm and 9 V, respectively. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hybrid Sputtering-Remote PECVD Deposition of Au Nanoparticles on SiO2 Layers for Surface Plasmon Resonance-Based Colored CoatingsPLASMA PROCESSES AND POLYMERS, Issue 8 2010Haile Takele Beyene Abstract In this paper, a hybrid system consisting of metal nano-particles dispersed on the surface of a dielectric layer is presented: a remote Expanding Thermal Plasma CVD system is used for the deposition of the inorganic (i.e. SiO2) layers from hexamethyldisiloxane/oxygen mixtures in combination with an rf magnetron sputtering tool for the deposition of metallic (i.e. gold) nanoparticles on top of the SiO2 layers. The optical properties of the Au/SiO2 layers have been investigated by means of UV-VIS-NIR variable angle spectroscopic ellipsometry. Rutherford backscattering and transmission electron microscopy were used to determine the film density, the nanoparticle size and its distribution, respectively. The uniform distribution of gold nanoparticles on the surface of the SiO2 layers allows obtaining red- to blue- colored coatings as a consequence of the shift of the surface plasmon resonance band to higher wavelengths, caused by an increase in size of nanoparticles and metal surface coverage. [source] In Situ Monitoring of Silicon Plasma Etching Using a Quantum Cascade Laser Arrangement,CHEMICAL VAPOR DEPOSITION, Issue 6-7 2007D. Stancu Abstract In etch plasmas used for semiconductor processing, concentrations of the precursor gas NF3 and of the etch product SiF4 are measured online and in situ using a new diagnostic arrangement, the Q-MACS Etch system, which is based on quantum cascade laser absorption spectroscopy (QCLAS). In addition, the etch rates of SiO2 layers and of the silicon wafer are monitored including plasma-etching endpoint detection. For this purpose the Q-MACS Etch system is working as an interferometer arrangement. The experiments are performed in an industrial, dual-frequency, capacitively coupled, magnetically enhanced, reactive ion etcher (MERIE), which is a plasma reactor developed for dynamic random access memory (DRAM) technologies. In the spectral range 1028 ± 0.3 cm,1, the absorption cross-sections of SiF4 and NF3 are determined to be ,,=,(7.7 ± 0.7) × 10,18 cm2 molecule,1 and ,,=,(8.7 ± 0.8) × 10,20 cm2 molecule,1, respectively. [source] Atomic Layer Deposition, Characterization, and Dielectric Properties of HfO2/SiO2 Nanolaminates and Comparisons with Their Homogeneous Mixtures,CHEMICAL VAPOR DEPOSITION, Issue 2-3 2006L. Zhong Abstract Nanolaminates of HfO2 and SiO2 were prepared using atomic layer deposition (ALD) methods. Successive exposure of substrates maintained at 120 or 160,°C to nitrogen flows containing Hf(NO3)4 and (tBuO)3SiOH led to typical bilayer spacings of 2.1,nm, with the majority of each bilayer being SiO2. The density of the SiO2 layers (measured using X-ray reflectometry (XRR)) was slightly higher than expected for amorphous silica, suggesting that as much as 10,% HfO2 was incorporated into the silica layers. Based on cross-sectional transmission electron microscopy (TEM) and XRR, oxidation of the silicon substrate was observed during its first exposure to Hf(NO3)4, leading to a SiO2 interfacial layer and the first HfO2 layer. Combining the ALD of Hf(NO3)4/(tBuO)3SiOH with ALD cycles involving Hf(NO3)4 and H2O allowed the systematic variation of the HfO2 thickness within the nanolaminate structure. This provided an approach towards controlling the dielectric constant of the films. The dielectric constant was modeled by treating the nanolaminate as a stack of capacitors wired in series. The nanolaminate structure inhibited the crystallization of the HfO2 in post-deposition annealing treatments. As the HfO2 thickness decreased, the preference for the tetragonal HfO2 phase increased. [source] | |||||||||||||