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Metal Layer (metal + layer)
Selected AbstractsSimply and reliably integrating micro heaters/sensors in a monolithic PCR-CE microfluidic genetic analysis systemELECTROPHORESIS, Issue 8 2009Runtao Zhong Abstract A novel fabrication process was presented to construct a monolithic integrated PCR-CE microfluidic DNA analysis system as a step toward building a total genetic analysis microsystem. Microfabricated Titanium/Platinum (Ti/Pt) heaters and resistance temperature detectors (RTDs) were integrated on the backside of a bonded glass chip to provide good thermal transfer and precise temperature detection for the drilled PCR-wells. This heater/RTD integration procedure was simple and reliable, and the resulting metal layer can be easily renewed when the Ti/Pt layer was damaged in later use or novel heater/RTD design was desired. A straightforward "RTD-calibration" method was employed to optimize the chip-based thermal cycling conditions. This method was convenient and rapid, comparing with a conventional RTD-calibration/temperature adjustment method. The highest ramping rates of 14°C/s for heating and 5°C/s for cooling in a 3-,L reaction volume allow 30 complete PCR cycles in about 33,min. After effectively passivating the PCR-well surface, successful ,-phage DNA amplifications were achieved using a two- or three-temperature cycling protocol. The functionality and performance of the integrated microsystem were demonstrated by successful amplification and subsequent on-line separation/sizing of ,-phage DNA. A rapid assay for Hepatitis B virus, one of the major human pathogens, was performed in less than 45,min, demonstrating that the developed PCR-CE microsystem was capable of performing automatic and high-speed genetic analysis. [source] Research and Prospects of Iron-Based SuperconductorsADVANCED MATERIALS, Issue 45 2009Zhi-An Ren Abstract The discovery of a new superconductor, LaFeAsO1,xFx with a superconducting critical temperatureT,c, of 26,K in 2008, has quickly renewed interest in the exploration of iron-based superconductors. More than 70 new superconductors have been discovered within several months, with the highest Tc of up to 55,K being observed in the SmFeAsO1,x compound. High Tcs have previously only been observed in cuprates; these new iron-based superconductors have been added as second members of the high- Tc family. The crystal structure of these compounds contains an almost 2D Fe,As layer formed by FeAs4 tetrahedrons, which can be separated by an oxide or metal layer that provides extra electrons to the Fe,As layer, and the itinerant iron 3d electrons form an antiferromagnetic (AFM) order state in the undoped parent compounds at around 100,200,K. Superconductivity can be induced by carrier doping, which destroys the AFM ground state. In this Review, the most recent findings on and basic experimental facts about this class of high- Tc materials will be presented, including the various superconducting structures, the synthesis methods, the physical properties of the parent compounds, the doping methods that could produce superconductivity, pressure effects, and the prospects for this new iron-based high- Tc family. [source] Pressureless Sintering of 3Y-TZP/Stainless-Steel Composite LayersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2008Mahdi Dourandish A pressureless sintering method was utilized to fabricate metal/ceramic joints out of yttria-stabilized zirconia (3Y-TZP) and stainless steels (SS). Ultrafine (150 nm) and nanoscale (75 nm) 3Y-TZP particles and micrometric 17-4PH, 316L, and 420 SS (<31 ,m) powders were tested. Isothermal and nonisothermal sintering behaviors of the powders and composite layers in hydrogen, argon, and vacuum atmospheres were examined. It was found that the mismatch strain between the zirconia ceramic and SS during cosintering is significant, which leads to bond cracking and joint failure. Nevertheless, interlayer diffusion of Zr, Fe, and Cr and the formation of a reaction zone, particularly during vacuum sintering, enables an accommodation of the residual stresses caused by the mismatch shrinkage upon cooling. The formation of a porous region close to the metal layer was observed. Sinter joining of zirconia to 420 SS is more successful compared with austenitic steel because of a lower difference in the coefficient of thermal expansion. [source] Microwave Bandgap in Multilayer Ceramic StructuresJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2006Bo Li A multilayer ceramic structure with a photonic bandgap (MC-PBG) was fabricated by a method of tape casting combined with screen printing. The MC-PBG structure is a two-dimensional array with either rectangular or hexagonal metal coils in a ceramic matrix. The metal coils are connected to the base metal layer in the ceramic substrate to form a monolithic body. The surface-wave dispersion properties of these MC-PBG structures were measured. A stop band, which is significantly influenced by the symmetrical characteristics of the inductor,capacitor (LC) arrays, was found in both the structures in the frequency range of 2.0,3.5 GHz. Because of their effective surface-wave suppression, MC-PBG structures can be used as high-performance antenna substrates to enhance the broadside gain of patch antenna devices. [source] Biomimetic Polymer Nanostructures by Injection MoldingMACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2003Nikolaj Gadegaard Abstract The nanometer scale topography of self-assembling structural protein complexes in animals is believed to induce favorable cell responses. An important example of such nanostructured biological complexes is fibrillar collagen that possesses a cross-striation structure with a periodicity of 69 nm and a peak-to-valley distance of 4,6 nm. Bovine collagen type I was assembled into fibrillar structures in vitro and sedimented onto solid supports. Their structural motif was transferred into a nickel replica by physical vapor deposition of a small-grained metal layer followed by galvanic plating. The resulting inverted nickel structure was found to faithfully present most of the micrometer and nanometer scale topography of the biological original. This nickel replica was used as a die for the injection molding of a range of different thermoplastic polymers. Total injection molding cycle times were in the range of 30,45 seconds. One of the polymer materials investigated, polyethylene, displayed poor replication of the biological nanotopographical motif. However, the majority of the polymers showed very high replication fidelity as witnessed by their ability to replicate the cross-striation features of less than 5 nm height difference. The latter group of materials includes poly(propylene), poly(methyl methacrylate), poly(L -lactic acid), polycaprolactone, and a copolymer of cyclic and linear olefins (COC). This work suggests that the current limiting factor for the injection molding of nanometer scale topography in thermoplastic polymers lies with the grain size of the initial metal coating of the mold rather than the polymers themselves. [source] Design of multilayer triangular substrate integrated waveguide filter in LTCCMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2009Wei Shen Abstract This article proposes a four-pole quasi-elliptic function triangular substrate integrated waveguide bandpass filter, which was fabricated using multilayer low-temperature cofired ceramic technology. In our design, neural network inverse model is adopted to fast capture the sizes of TSIW cavities, with the coupling matrix transformation implemented to achieve cross coupling on the basis of multilayer TSIW. A slot on the top metal layer is introduced so as to suppress the two higher spurious modes. The filter has 65% size reduction in comparison with its planar counterpart, with good agreement obtained between the simulated and measured S-parameters. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2582,2585, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24680 [source] A wideband microstrip antenna with symmetric radiation patternsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2008Veeresh G. Kasabegoudar Abstract A wideband microstrip antenna using a coplanar capacitive feed with nearly 50% impedance bandwidth has been realized on a stacked air-dielectric substrate with only one metal layer above the ground plane. In this article an approach of modifying the patch shape is proposed to obtain symmetric radiation patterns in the entire frequency band of this antenna. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1991,1995, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23575 [source] On the improvement of the electroluminescent signal of organic light-emitting diodes by the presence of an ultrathin metal layer at the interface organic/ITOPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2008J. C. Bernède Under DOI 10.1002/pssa.200723206 erroneously a paper was published online in January 2008 which already had been published elsewhere. Please find this paper, entitled "On the improvement of the electroluminescent signal of organic light emitting diodes by the presence of an ultra-thin metal layer at the interface organic/ITO" by J. C. Bernède, F. Martinez, G. Neculqueo, and L. Cattin under DOI 10.1002/pssr.200701217, published in phys. stat. sol. (RRL) 2, No. 1, 10,12 (2008). (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Semi-insulating (Cd,Mn)Te:V crystals: Electrical contactsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007M. Witkowska-Baran Abstract The high-resistivity (Cd,Mn)Te is believed to be suitable to succesfully replace the commonly used (Cd,Zn)Te system as a material for manufacturing large-area X- and ,-ray detectors. The purpose of our study was to elaborate a method of preparing high quality (Cd,Mn)Te crystal plates as well as a technique of producing good electrical contacts to that material. (Cd,Mn)Te was grown using the Bridgman method. The crystals were doped with vanadium to the level of 1016 cm,3. The crystals are twinned in the (111) plane, but by slicing the crystal parallel to the twinning plane we obtained monocrystalline plates of large area (e.g. 30 × 30 mm2), which is essential for application purposes. Proper annealing of those plates in cadmium vapours allowed us to reduce the number of cadmium vacancies forming during the growth process. Due to the vanadium dopant acting as a compensating centre we obtained a semi-insulating material. In order to obtain good contacts to the (Cd,Mn)Te plates we used the method proposed initially for CdTe by Rioux et al. The ZnTe:Sb layers (,1 ,m thick) were grown on the epi-ready (Cd,Mn)Te:V plates by the MBE technique. The grown layers were p-type and formed a good electrical contact to the crystal plates. Finally , a standard technique was used to cover the ZnTe layer by a metal layer. The contacts formed on (111) surfaces of (Cd,Mn)Te were studied. We believe that the contacts to the (111) surface are important for applications. In the paper we describe techniques of preparing electrical contacts and results of their characterization. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Oxidation treatment on Ni/Au Ohmic contacts to p-type GaNPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Z. Z. Chen Abstract Current,voltage (I,V) characteristics, transmission line method (TLM), and optical transmittance measurements are performed to investigate the effects of thermal oxidation and plasma-induced oxidation treatments on Ni/Au contacts to p-type GaN. Whether oxidation and thermal annealing are performed simultaneously or in succession, the specific contact resistances of Au/Ni/p-GaN are reduced. As to plasma-induced oxidation, neither no-oxidation nor long-time oxidation treatments on Ni/Au layers are suitable for obtaining a low-resistance Ohmic contact. The roles of oxidation are believed to activate the Mg acceptor in p-GaN and to form an oxygenous intermediate semiconductor layer, which may lower the Schottky barrier height between the metal layer and p-GaN. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Role of polymer chain end groups in plasma modification for surface metallization of polymeric materialsPOLYMER INTERNATIONAL, Issue 6 2009Norihiro Inagaki Abstract How to improve adhesion between poly(oxybenzoate- co -oxynaphthoate) (Vecstar OC and FA films) and copper metal by Ar, O2, N2 and NH3 plasma modification was investigated. The mechanism of adhesion improvement is discussed from the viewpoint of chemical and physical interactions at the interface between the Vecstar film and copper metal layer. The adhesion between Vecstar OC film and copper metal was improved by chemical rather than physical interactions. Polymer chain end groups that occur at Vecstar OC film surfaces contribute effectively to adhesion. This improvement in adhesion is due to interactions between copper metal and OC groups formed by plasma modification. Aggregation of the OC groups to the copper metal/Vecstar OC film interface is a key factor for good adhesion. From this aspect, heat treatment of plasma-modified Vecstar OC films on glass plates is effective in the aggregation, and the peel strength for the copper metal/Vecstar OC film system reached 1.21 N (5 mm),1. Copyright © 2009 Society of Chemical Industry [source] Evidence for the Hypothesis of Ignition of Propellants by Metallic Vapour DepositionPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2002Michael This paper examines the experimental evidence to support the hypothesis of ignition of energetic material by the process of metallic vapour deposition. The hypothesis has been presented previously, and this is the continuation of the work. The hypothesis has been developed at QinetiQ to explain certain measurements of incident radiative flux during electrothermal-chemical (ETC) experimentation, which show no correlation with the ignition event. Indeed, measured levels of radiation have been so low that radiative energy transfer for ETC plasma ignition could be said to be negligible. Measurement of the thickness of a metal layer resulting from dropwise vapour condensation gives good correlation to the flux requirements for ignition. [source] Use of recombinant rotavirus VP6 nanotubes as a multifunctional template for the synthesis of nanobiomaterials functionalized with metalsBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Germán Plascencia-Villa Abstract The structural characteristics and predefined constant size and shape of viral assemblies make them useful tools for nanobiotechnology, in particular as scaffolds for constructing highly organized novel nanomaterials. In this work it is shown for the first time that nanotubes formed by recombinant rotavirus VP6 protein can be used as scaffolds for the synthesis of hybrid nanocomposites. Rotavirus VP6 was produced by the insect cell-baculovirus expression vector system. Nanotubes of several micrometers in length and various diameters in the nanometer range were functionalized with Ag, Au, Pt, and Pd through strong (sodium borohydride) or mild (sodium citrate) chemical reduction. The nanocomposites obtained were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM) with energy dispersive spectroscopy (EDS), dynamic light scattering, and their characteristic plasmon resonance. The outer surface of VP6 nanotubes had intrinsic affinity to metal deposition that allowed in situ synthesis of nanoparticles. Furthermore, the use of preassembled recombinant protein structures resulted in highly ordered integrated materials. It was possible to obtain different extents and characteristics of the metal coverage by manipulating the reaction conditions. TEM revealed either a continuous coverage with an electrodense thin film when using sodium citrate as reductant or a discrete coverage with well-dispersed metal nanoparticles of diameters between 2 and 9,nm when using sodium borohydride and short reaction times. At long reaction times and using sodium borohydride, the metal nanoparticles coalesced and resulted in a thick metal layer. HRTEM-EDS confirmed the identity of the metal nanoparticles. Compared to other non-recombinant viral scaffolds used until now, the recombinant VP6 nanotubes employed here have important advantages, including a longer axial dimension, a dynamic multifunctional hollow structure, and the possibility of producing them massively by a safe and efficient bioprocess. Such characteristics confer important potential applications in nanotechnology to the novel nanobiomaterials produced here. Biotechnol. Bioeng. 2009; 104: 871,881. © 2009 Wiley Periodicals, Inc. [source] Generation of Nanopores Down to 10 nm for Use in Deep-Nulling InterferometryCHEMPHYSCHEM, Issue 2 2008Axel Wehling Dr. Abstract Scanning electron microscope images show that it is easy to generate nanopores on polycarbonate membranes with well-defined pore diameters by ion-track perforation and subsequent magnetron sputtering with metal. The size reduction of the nanopores during sputtering with gold is a linear function of time. Images of different angles and from the bottom side of the membrane show that the channels are the smallest very close to the surface of the metal layer, have a conelike shape, and reach about half as much into the polymer membranes as the metal-layer thickness. This topographical pore shape is ideal for use as optically coherent near-field sources in deep-nulling microscopy. We present the first results of significantly improved nulling stabilization in the presence (<2 nm optical pathway difference) and the absence (<0.6 nm optical pathway difference) of the nanoapertures in the focal region of a deep-nulling microscope. [source] Fabrication of Precise Fluidic Structures in LTCCINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2009Fred Barlow A number of emerging applications of low-temperature co-fired ceramic (LTCC) require embedded fluidic structure within the co-fired ceramic and or precise external dimensional tolerances. These structures enable the control of fluids for cooling, sensing, and biomedical applications, and variations in their geometry from the design can have a significant impact on the overall performance of the devices. One example of this type of application is a multilayer cooler developed recently by the authors for cooling laser diode bars. In many laser systems, laser diodes are the primary emitters, or assemblies of these diode bars are used to pump traditional laser crystals such as Nd:YLF. Assemblies of these diodes require large amounts of electrical current for proper operation, and the device operating temperature must be carefully controlled in order to avoid a shift in the output wavelength. These diodes are packaged into water-cooled assemblies and by their nature dissipate enormous amounts of heat, with waste heat fluxes on the order of 2000 W/cm2. The traditional solution to this problem has been the development of copper multilayer coolers. Assemblies of laser diodes are then formed by stacking these diode bars and coolers. Several problems exist with this approach including the erosion of the copper coolers by the coolant, a requirement for the use of deionized water within the system, and a significant CTE mismatch between the diode bar and the metal cooler. Diodes are bonded to these metal structures and liquid coolant is circulated through the metal layers in order to cool the diode bar. In contrast, the coolers developed by the authors utilize fluid channels and jets formed within LTCC as well as embedded cavity structures to control the flow of a high-velocity liquid and actively cool the laser diode bars mounted on the surface of the LTCC., The dimensional tolerances of these cooler assemblies and complex shapes that are used to control the fluid can have a significant impact on the overall performance of the laser system. This paper describes the fabrication process used to create the precise channel and jet structures used in these LTCC-based coolers, as well as some of the challenges associated with these processes. [source] Injection-locked GaInp/GaAs HBT frequency divider with stacked transformersMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2007Hung-Ju Wei Abstract The first integrated GaInP/GaAs heterojunction bipolar transistor (HBT) injection-locked frequency divider (ILFD) with the stacked transformers is demonstrated around 10 GHz. The stacked transformers formed by only two metal layers provide the inductive coupling in the cross feedback and separate biasing for base and collector to allow for the larger output swing in the LC tank and obtaining wide locking range. Under the supply voltage of 5 V and core power consumption of 20.5 mW, the locking range is 7.8% of the center operating frequency. The chip size of the entire ILFD including probing pads is 1.0 × 1.0 mm2. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2602,2605, 2007; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.22737 [source] Ultrathin metal layers to convert surface polarity of nitride semiconductorsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2005T. Nakayama Abstract The possibility of the surface-polarity conversion of AlN upon the deposition of ultrathin Al metal layers is investigated by the first-principles theoretical calculations. It is shown that, reflecting the crystal structures of underlying layers and the binding-energy difference between Al,N and Al,Al bonds, the surface-polarity conversion from N-face to Al-face polarity becomes possible only when the deposited Al metal layers have wurtzite structure and two-monolayer thickness. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Surface plasmon enhanced light emission from semiconductor materialsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Koichi Okamoto Abstract Surface plasmon (SP) coupling technique was used to enhance light emissions from semiconductor nanocrystals with evaporated metal layers. We found that the SP coupling can increase the internal quantum efficiencies (IQE) of emission from CdSe-based nanocrystals regardless of the initial efficiencies. This suggests that this technique should be much effective for various materials that suffer from low quantum efficiencies. We also obtained 70-fold enhancement of emission from silicon nanocrystals in silicon dioxide. Obtained IQE value is 38%, which is as large as that of a compound semiconductor with direct transition. The SP coupling technique would bring a great improvement to silicon photonics. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Development of thin-film Cu(In,Ga)Se2 and CdTe solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2-3 2004A. Romeo Abstract Cu(In,Ga)Se2 and CdTe heterojunction solar cells grown on rigid (glass) or flexible foil substrates require p -type absorber layers of optimum optoelectronic properties and n -type wide-bandgap partner layers to form the p,n junction. Transparent conducting oxide and specific metal layers are used for front and back electrical contacts. Efficiencies of solar cells depend on various deposition methods as they control the optoelectronic properties of the layers and interfaces. Certain treatments, such as addition of Na in Cu(In,Ga)Se2 and CdCl2 treatment of CdTe have a direct influence on the electronic properties of the absorber layers and efficiency of solar cells. Processes for the development of superstrate and substrate solar cells are reviewed. Copyright © 2004 John Wiley & Sons, Ltd. 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