Search results for "CVD."
showing 10 items of 81 documents
Transient Radiation Responses of Optical Fibers: Influence of MCVD Process Parameters
2012
International audience; A dedicated set of fibers elaborated via the Modified Chemical Vapor Deposition (MCVD) technique is used to study the influence of composition and drawing parameters on their responses to an X-ray pulse representative of the radiation environments associated with Megajoule class lasers. These canonical fibers were designed to highlight the impact of these parameters on the amplitude and kinetics of the transient pulsed X-ray Radiation Induced Attenuation (RIA) at room temperature. From preforms differing by their core composition, three optical fibers were elaborated by varying the tension and speed during the drawing process. No or only slight RIA change results fro…
Surface investigation of plasma HMDSO membranes post-treated by CF4/Ar plasma
2002
Fluorination treatment has been performed on polysiloxane membranes using a plasma glow discharge of a gases mixture CF4 and argon (plasma enhanced chemical vapor deposition). Atomic force microscopy, XPS analyses and contact angle measurements have been undertaken to explain the surface transformation and behavior, which strongly depend on the morphology, the composition and the hydrophilic/hydrophobic character of the plasma-polymerized initial membranes. Main result is that fluorination, which leads to hydrophobic membranes, has a more relevant effect on amorphous silica-like membranes than on polymer-like ones, according to their chemical composition whereas the plasma surface reaction …
Correlation between Zn vacancies and photoluminescence emission in ZnO films.
2006
Photoluminescence and positron annihilation spectroscopy have been used to characterize and identify vacancy-type defects produced in ZnO films grown on sapphire by metal-organic chemical-vapor deposition. The photoluminescence of the samples in the near band edge region has been studied, paying particular attention to the emission at 370.5 nm (3.346 eV). This emission has been correlated to the concentration of Zn vacancies in the films, which has been determined by positron annihilation spectroscopy. Jesus.Zuniga@uv.es Vicente.Munoz@uv.es
Optical characterization of Mg-doped GaN films grown by metalorganic chemical vapor phase deposition
2000
Scanning electron microscopy, micro-Raman, and photoluminescence (PL) measurements are reported for Mg-doped GaN films grown on (0001) sapphire substrates by low-pressure metalorganic chemical vapor phase deposition. The surface morphology, structural, and optical properties of GaN samples with Mg concentrations ranging from 1019 to 1021 cm−3 have been studied. In the scanning micrographs large triangular pyramids are observed, probably due to stacking fault formation and three-dimensional growth. The density and size of these structures increase with the amount of magnesium incorporated in the samples. In the photoluminescence spectra, intense lines were found at 3.36 and 3.31 eV on the tr…
Structural characterization of a-plane Zn1−xCdxO (0 < x <0.085) thin films grown by metal-organic vapor phase epitaxy.
2006
Zn1−xCdxO(11math0) films have been grown on (01math2) sapphire (r–plane) substrates by metal-organic vapor phase epitaxy. A 800-nm-thick ZnO buffer, deposited prior to the alloy growth, helps to prevent the formation of pure CdO. A maximum uniform Cd incorporation of 8.5 at. % has been determined by Rutherford backscattering spectrometry. Higher Cd contents lead to the coexistence of Zn1−xCdxO alloys of different compositions within the same film. The near band-edge photoluminescence emission shifts gradually to lower energies as Cd is incorporated and reaches 2.93 eV for the highest Cd concentration (8.5 at. %). The lattice deformation, due to Cd incorporation, has been described using a n…
Vanadium dioxide and gold nanocomposite films for glazing application
2009
Vanadium dioxide is a material with great potential as an intelligent glazing material. The technology is based on a metal to semiconductor transition (MST) where there is an associated structural change from the higher temperature rutile structure to the lower temperature monoclinic structure. This structural transition results in significant changes in optical properties and electrical conductivity. Hybrid aerosol assisted and atmospheric pressure chemical vapour deposition methodology has been utilised, to produce thin films of gold nano-particle vanadium dioxide nanocomposites. Good surface coverage is observed comparable to that of APCVD processes and a variety of different film thickn…
OLIVE OIL CONSUMPTION AND RISK OF CORONARY HEART DISEASE AND/OR STROKE: A META-ANALYSIS OF CASE-CONTROL, COHORT AND INTERVENTION STUDIES
2014
Increasing evidence suggests that the Mediterranean diet can reduce the risk of CVD. Olive oil is the hallmark of this dietary pattern. We conducted a meta-analysis of case–control, prospective cohort studies and a randomised controlled trial investigating the specific association between olive oil consumption and the risk of CHD (101 460 participants) or stroke (38 673 participants). The results of all observational studies were adjusted for total energy intake. The random-effects model assessing CHD as an outcome showed a relative risk (RR) of 0·73 (95% CI 0·44, 1·21) in case–control studies and 0·96 (95% CI 0·78, 1·18) in cohort studies for a 25 g increase in olive oil consumption. In co…
Functional Thin Films for Glazing Application
2009
Vanadium dioxide is a thermochromic material with great potential for use in intelligent glazing. The thermochromic properties result from a metal to semiconductor transition (MST) where there is an associated structural change from the higher temperature rutile structure to the lower temperature monoclinic structure. This structural transition results in significant changes in optical properties and electrical conductivity. Various chemical vapour deposition (CVD) methodologies have been utilised, to produce thin films of vanadium dioxide. Different strategies are presented for the inclusion of metal dopants and the production of nano-composites. The use of a surfactant molecule, tetraocty…
Energy modelling studies of enhanced glazing.
2009
The research on new “energy materials” is a very interesting field of study in the direction of energy saving control in the building construction sector. Lots of studies have been carrying on to develop new enhanced glazing, new synthesis and analysing procedures but simulating their real behaviour is often very difficult and expensive. The easiest way to test the energy performance of new enhanced glazing, in this work doped vanadium (IV) dioxide thermochromic glazing, is to simulate the way they would respond if they were installed in a building. The software used to perform such simulations is Energy Plus™ which is an energy analysis and thermal load simulation program. The aim of this …
Fabrication and characterisation of ZnO nanostructures: from nanoscale building blocks to hybrid nanomaterials - towards emerging technologies in sen…
2012
Metal oxide nanostructures characterized by multiple morphologies and structures are at the forefront of applications driven nanotechnology research. In particular, they represent a versatile solution for performance enhancement and applications in multifunctional devices and offer distinct advantages over their bulk counterparts. The current state in ZnO nanomaterials research and its impact in nanotechnology and modern engineering are discussed through the lens of con-tinuing technological advances in synthetic techniques allowing to obtain the material with predefined specific set of criteria including size, functionality, and uniqueness. Aim of this research activity is fabrication and …