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Microwave Plasma (microwave + plasma)

Distribution by Scientific Domains

Polymers and Materials Science	72%

Selected Abstracts

Functionalization of COC Surfaces by Microwave Plasmas

PLASMA PROCESSES AND POLYMERS, Issue S1 2007
Hartmut Steffen
Abstract Cyclic olefin copolymers (COC) combine excellent transparency, high moisture barrier, high strength and stiffness and very low shrinkage. COCs have excellent chemical resistance to aqueous acids and bases and to most polar solvents. This property combination makes them excellent candidates for diverse diagnostic applications in biomedical science. But they are very hydrophobic and thus not suitable for cell-contacting applications. This work investigates the surface functionalization of COC compared to PS by NH3 and SO2 microwave plasmas. The surfaces were mainly analysed by high-resolution X-ray photoelectron spectroscopy (XPS). Moreover, cells were cultivated on both substrates to verify the applicability of COC for cell-based disposables. Actually, microwave plasma-functionalized COC surfaces support the adhesion and proliferation of adherent cell lines, which usually require the coating of the substrate with extra cellular matrix molecules. [source]

Synthesis and Characterization of Alumina Microtubes in a Template Process from Short Carbon Fibers,

ADVANCED ENGINEERING MATERIALS, Issue 5 2007
Z. Pajkic
A novel, two step process for synthesis of Al2O3 microtubes from short carbon fibers as templates is reported. In the first process step, the carbon fibers are coated with a Al-AlN-Al4C3 composite in a microwave plasma fluidized bed CVD process. The coated material is then being treated in a furnace on high temperature in air, resulting finaly with alumina microtubes (hollow fibers). [source]

Catalyst-Free Efficient Growth, Orientation and Biosensing Properties of Multilayer Graphene Nanoflake Films with Sharp Edge Planes,

ADVANCED FUNCTIONAL MATERIALS, Issue 21 2008
Nai Gui Shang
Abstract We report a novel microwave plasma enhanced chemical vapor deposition strategy for the efficient synthesis of multilayer graphene nanoflake films (MGNFs) on Si substrates. The constituent graphene nanoflakes have a highly graphitized knife-edge structure with a 2,3,nm thick sharp edge and show a preferred vertical orientation with respect to the Si substrate as established by near-edge X-ray absorption fine structure spectroscopy. The growth rate is approximately 1.6,µm min,1, which is 10 times faster than the previously reported best value. The MGNFs are shown to demonstrate fast electron-transfer (ET) kinetics for the Fe(CN)63,/4, redox system and excellent electrocatalytic activity for simultaneously determining dopamine (DA), ascorbic acid (AA) and uric acid (UA). Their biosensing DA performance in the presence of common interfering agents AA and UA is superior to other bare solid-state electrodes and is comparable only to that of edge plane pyrolytic graphite. Our work here, establishes that the abundance of graphitic edge planes/defects are essentially responsible for the fast ET kinetics, active electrocatalytic and biosensing properties. This novel edge-plane-based electrochemical platform with the high surface area and electrocatalytic activity offers great promise for creating a revolutionary new class of nanostructured electrodes for biosensing, biofuel cells and energy-conversion applications. [source]

Phosphorus incorporation and activity in (100)-oriented homoepitaxial diamond layers

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2009
G. Frangieh
Abstract In this work, we present a study about the homoepitaxial growth of phosphorus-doped diamond on (100) substrates. The growth was performed by microwave plasma assisted chemical vapor deposition (MPCVD) adding an organic precursor for phosphorus (tertiarybutylphosphine: TBP) in the gaseous phase. We show that phosphorus is incorporated in (100) chemical vapor deposition (CVD) diamond as proved by secondary ion mass spectrometry (SIMS). The recombination of excitons bound to phosphorus donors is observed by cathodoluminescence (CL) spectroscopy. The influence of the growth parameters on the phosphorus donor activity is investigated. We show that the [C*]/[H2] ratio is a key parameter for controlling the P-donor activity when diamond is grown on (100) surfaces. [source]

Towards optical-quality nanocrystalline diamond with reduced non-diamond content

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2009
Z. Remes
Abstract Our nominally undoped nanocrystalline diamond (NCD) films were deposited on fused silica substrates by the microwave plasma enhanced chemical vapor deposition (MW CVD) at a relatively low temperature below 600,°C. They show high dark resistivity and measurable photosensitivity after surface oxidation. We present the "true" optical absorptance spectra calculated from transmittance T and reflectance R measurements corrected on the surface scattering and compare them with the normalized photocurrent spectra. The optical scattering does not allow to evaluate the small optical absorption in visible and near IR range from the T and R spectra. The photocurrent spectra were measured in the ultraviolet, visible, and near infrared optical range using the dual beam photocurrent spectroscopy (DBP) under constant UV illumination. Previously, NCD films often showed non-diamond content with the photo-ionization threshold at 0.8,eV increasing significantly the optical absorption in near IR and visible region. Here, we show that the non-diamond content can be reduced by several orders of magnitude by depositing NCD on the carefully selected UV-grade fused silica substrates under the optimized growth conditions followed by the post-deposition chemical etching and cleaning. Unlike the NCD layers with high non-diamond content, the NCD layers with reduced non-diamond content are stable up to 450,°C. [source]

Dose rate effects on the thermoluminescence kinetics properties of MWCVD diamond films

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2007
S. Gastélum
Abstract Dose rate effects are important in thermoluminescent (TL) dosimeter applications because a certain absorbed dose given at different dose rates may result in a different TL yield. The present work reports about the dose rate effects on TL glow curves and kinetics properties of microwave plasma assisted chemical vapor deposition (MWCVD) diamond films grown on (100) silicon. The diamond films were exposed to , radiation at 20.67, 43.4 and 81.11 Gy min,1 dose rates in the range of 0.05,10 kGy. The films showed a linear dose behavior up to 2 kGy and reached saturation for higher doses. The TL intensity varied as a function of dose rate and the samples had a maximum TL response for relatively lower dose rates. A single first order kinetics TL peak was typical for low doses while at higher doses two first order kinetics peaks were necessary to fit the glow curves. The results indicate that dose rate effects may be significant in dosimetric applications of MWCVD diamond. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Interaction of Stearic Acid Deposited on Silicon Samples With Ar/N2 and Ar/O2 Atmospheric Pressure Microwave Post-discharges

PLASMA PROCESSES AND POLYMERS, Issue S1 2009
Cédric Noël
Abstract In this work, the interactions of a stearic acid film deposited on silicon by spin coating with the post-discharge of an Ar/N2 or Ar/O2 atmospheric pressure microwave plasma are studied. Sample surface before and after plasma treatment is analysed by means of different surface analysis methods (water contact angle measurements, XPS, ToF-SIMS and FTMS). Both plasma treatments modify the surface but with a higher etching rate for Ar/O2 post-discharges. The creation of double carbon bonds CC is observed during the treatments, with a higher quantity after Ar/N2 treatments. The mechanisms leading to modifications of stearic acid are discussed. [source]

A Novel Approach for Chemical Vapor Synthesis of ZnO Nanocrystals: Optimization of Yield, Crystallinity,

CHEMICAL VAPOR DEPOSITION, Issue 7-9 2009
Moazzam Ali
Abstract The experimental yield of ZnO nanocrystals decreases drastically with increasing reactor temperature in a typical chemical vapor synthesis (CVS) of ZnO nanocrystals from diethylzinc. A novel CVS set-up , a microwave plasma combined with a hot-wall zone , is described to minimize the loss of particles at higher reactor temperatures. The powder samples have been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). It is observed that the synthesis set-up and reaction temperature have substantial influence not only on yield but also on crystallite size and crystallinity of the pure wurtzite-type ZnO nanocrystals. The lattice constants of ZnO nanocrystals increase with decreasing crystallite size. Defect densities (twin and stacking faults), as well as microstrain, decrease with increasing reactor temperature, whereas crystallinity increases. [source]

Surface Science Contribution to the BEN Control on Si(100) and 3C-SiC(100): Towards Ultrathin Nanocrystalline Diamond Films,

CHEMICAL VAPOR DEPOSITION, Issue 7-8 2008
Jean-Charles Arnault
Abstract Deposition of thin and smooth nanocrystalline diamond films requires a high degree of control of the nucleation stage. The nature of the interface between diamond film and substrate is also important for some applications. The successive steps of the bias-enhanced nucleation (BEN) process are studied in-situ on Si(100) and 3C-SiC(100) using electron spectroscopies. Thin nanodiamond films (80,900,nm) have been achieved on Si(100). The formation of a thin covering SiC layer (2,3,nm) during the plasma exposure for parameters stabilization (PEPS) step leads us to study the plasma/surface interactions on 3C-SiC(100) surfaces. The C-terminated 3C-SiC(100) demonstrates a large inertia under microwave plasma (MP)CVD conditions. An enhancement of diamond nucleation on this surface is observed. Moreover, surface analysis reveals very little damage after BEN on 3C-SiC surfaces. [source]

Growth of Diamond Nanoplatelets by CVD,

CHEMICAL VAPOR DEPOSITION, Issue 7-8 2008
Hou-Guang Chen
Abstract Hexagonal, single-crystalline, diamond nanoplatelets synthesized by microwave plasma (MP)CVD on Au-Ge alloy and nanocrystalline diamond (nc-diamond) film substrates, respectively, are reported. On the nc-diamond matrix, hexagonal diamond nanoplatelets can grow to a thickness of as little as approximately 10,nm. The effects of various processing parameters, such as methane concentration, microwave power, and gas pressure, on the growth of diamond nanoplatelets are explored. High-resolution transmission electron microscopy (HRTEM) reveals that the diamond nanoplatelets contain multi-parallel twins, and the side faces of the platelets exhibit {100}/{111} ridge-and-trough structure. Anisotropic growth of diamond nanoplatelet is believed to result from the side face structure of the twinned platelets and intensive plasma reaction. [source]