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Sample records for metal barrier layer

  1. Low resistance barrier layer for isolating, adhering, and passivating copper metal in semiconductor fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Weihs, Timothy P. (Baltimore, MD); Barbee, Jr., Troy W. (Palto Alto, CA)

    2002-01-01

    Cubic or metastable cubic refractory metal carbides act as barrier layers to isolate, adhere, and passivate copper in semiconductor fabrication. One or more barrier layers of the metal carbide are deposited in conjunction with copper metallizations to form a multilayer characterized by a cubic crystal structure with a strong (100) texture. Suitable barrier layer materials include refractory transition metal carbides such as vanadium carbide (VC), niobium carbide (NbC), tantalum carbide (TaC), chromium carbide (Cr.sub.3 C.sub.2), tungsten carbide (WC), and molybdenum carbide (MoC).

  2. Electrical and materials characterization of tungsten-titanium diffusion barrier layers and alloyed silver metallization

    Science.gov (United States)

    Bhagat, Shekhar Kumar

    With the constant miniaturization of semiconductor devices, research is always ongoing to obtain the best materials and/or materials systems which fulfill all the requirements of an ideal interconnect. Silver (Ag) and silver based alloys are front runners among other metals and alloys being investigated. Ag has a low electrical resistivity (1.59 micro-ohm-centimeters for bulk), very high thermal conductivity (4.25 Watt per centimeters per Kelvin), and has better electromigration resistance than aluminum (Al). In the pure form, however, it has several drawbacks (e.g., a tendency to diffuse in silicon substrate at higher temperatures, inadequate adhesion to silicon dioxide, poor corrosion resistance, and agglomeration at higher temperatures). These drawbacks can be circumvented by the addition of diffusion barrier layers and/or alloying in silver. The present study investigates both routes to make silver a legitimate interconnect material. Initially this study focuses on thermal stability and behavior of tungsten-titanium (W-Ti) barrier layers for Ag metallization. It is shown that Ag thin films are thermally stable up to 650 degrees centigrade with the presence of W-Ti under layers. The effect of a W-Ti layer on the {111} texture formation in Ag thin film is also evaluated in detail. Insertion of a thin W-Ti over layer on Ag thin films is investigated with respect to their thermal stability. This research also evaluates the diffusion of Ag into silicon dioxide and W-Ti barriers. This project shows that W-Ti is an effective barrier layer for silver metallization. Later, the study investigates the effect of Cu addition in silver metallization and its impact on electromigration resistance. It is shown that Cu addition enhances the electromigration lifetime for silver metallization.

  3. Positron annihilation lifetime spectroscopy (PALS) application in metal barrier layer integrity for porous low- k materials

    CERN Document Server

    Simon, Lin; Gidley, D W; Wetzel, J T; Monnig, K A; Ryan, E T; Simon, Jang; Douglas, Yu; Liang, M S; En, W G; Jones, E C; Sturm, J C; Chan, M J; Tiwari, S C; Hirose, M

    2002-01-01

    Positron Annihilation Lifetime Spectroscopy (PALS) is a useful tool to pre-screen metal barrier integrity for Si-based porous low-k dielectrics. Pore size of low-k, thickness of metal barrier Ta, positronium (Ps) leakage from PALS, trench sidewall morphology, electrical test from one level metal (1LM) pattern wafer and Cu diffusion analysis were all correlated. Macro-porous low-k (pore size >=200 AA) and large scale meso-porous low-k (>50~200 AA) encounter both Ps leakage and Cu diffusion into low-k dielectric in the 0.25 mu mL/0.3 mu mS structures when using SEMATECH in-house PVD Ta 250 AA as barrier layer. For small scale meso-porous (>20~50 AA) and micro- porous (<=20 AA) low-k, no Ps leakage and no Cu diffusion into low-k were observed even with PVD Ta 50 AA, which is proved also owing to sidewall densification to seal all sidewall pores due to plasma etch and ash. For future technology, smaller pore size of porous Si-based low-k (=<50 AA) will be preferential for dense low-k like trench sidewall to...

  4. Investigation of Thickness Dependence of Metal Layer in Al/Mo/4H-SiC Schottky Barrier Diodes.

    Science.gov (United States)

    Lee, Seula; Lee, Jinseon; Kang, Tai-Young; Kyoung, Sinsu; Jung, Eun Sik; Kim, Kyung Hwan

    2015-11-01

    In this paper, we present the preparation and characterization of Schottky barrier diodes based on silicon carbide with various Schottky metal layer thickness values. In this structure, molybdenum and aluminum were employed as the Schottky barrier metal and top electrode, respectively. Schottky metal layers were deposited with thicknesses ranging from 1000 to 3000 Å, and top electrodes were deposited with thickness as much as 3000 Å. The deposition of both metal layers was performed using the facing target sputtering (FTS) method, and the fabricated samples were annealed with the tubular furnace at 300 degrees C under argon ambient for 10 min. The Schottky barrier height, series resistance, and ideality factor was calculated from the forward I-V characteristic curve using the methods proposed by Cheung and Cheung, and by Norde. For as-deposited Schottky diodes, we observed an increase of the threshold voltage (V(T)) as the thickness of the Schottky metal layer increased. After the annealing, the Schottky barrier heights (SBHs) of the diodes, including Schottky metal layers of over 2000 Å, increased. In the case of the Schottky metal layer deposited to 1000 Å, the barrier heights decreased due to the annealing process. This may have been caused by the interfacial penetration phenomenon through the Schottky metal layer. For variations of V(T), the SBH changed with a similar tendency. The ideality factor and series resistance showed no significant changes before or after annealing. This indicates that this annealing condition is appropriate for Mo SiC structures. Our results confirm that it is possible to control V(T) by adjusting the thickness of the Schottky metal layer.

  5. Fabrication of metallic single electron transistors featuring plasma enhanced atomic layer deposition of tunnel barriers

    Science.gov (United States)

    Karbasian, Golnaz

    The continuing increase of the device density in integrated circuits (ICs) gives rise to the high level of power that is dissipated per unit area and consequently a high temperature in the circuits. Since temperature affects the performance and reliability of the circuits, minimization of the energy consumption in logic devices is now the center of attention. According to the International Technology Roadmaps for Semiconductors (ITRS), single electron transistors (SETs) hold the promise of achieving the lowest power of any known logic device, as low as 1x10-18 J per switching event. Moreover, SETs are the most sensitive electrometers to date, and are capable of detecting a fraction of an electron charge. Despite their low power consumption and high sensitivity for charge detection, room temperature operation of these devices is quite challenging mainly due to lithographical constraints in fabricating structures with the required dimensions of less than 10 nm. Silicon based SETs have been reported to operate at room temperature. However, they all suffer from significant variation in batch-to-batch performance, low fabrication yield, and temperature-dependent tunnel barrier height. In this project, we explored the fabrication of SETs featuring metal-insulator-metal (MIM) tunnel junctions. While Si-based SETs suffer from undesirable effect of dopants that result in irregularities in the device behavior, in metal-based SETs the device components (tunnel barrier, island, and the leads) are well-defined. Therefore, metal SETs are potentially more predictable in behavior, making them easier to incorporate into circuits, and easier to check against theoretical models. Here, the proposed fabrication method takes advantage of unique properties of chemical mechanical polishing (CMP) and plasma enhanced atomic layer deposition (PEALD). Chemical mechanical polishing provides a path for tuning the dimensions of the tunnel junctions, surpassing the limits imposed by electron beam

  6. Ceramic barrier layers for flexible thin film solar cells on metallic substrates: a laboratory scale study for process optimization and barrier layer properties.

    Science.gov (United States)

    Delgado-Sanchez, Jose-Maria; Guilera, Nuria; Francesch, Laia; Alba, Maria D; Lopez, Laura; Sanchez, Emilio

    2014-11-12

    Flexible thin film solar cells are an alternative to both utility-scale and building integrated photovoltaic installations. The fabrication of these devices over electrically conducting low-cost foils requires the deposition of dielectric barrier layers to flatten the substrate surface, provide electrical isolation between the substrate and the device, and avoid the diffusion of metal impurities during the relatively high temperatures required to deposit the rest of the solar cell device layers. The typical roughness of low-cost stainless-steel foils is in the hundred-nanometer range, which is comparable or larger than the thin film layers comprising the device and this may result in electrical shunts that decrease solar cell performance. This manuscript assesses the properties of different single-layer and bilayer structures containing ceramics inks formulations based on Al2O3, AlN, or Si3N4 nanoparticles and deposited over stainless-steel foils using a rotogravure printing process. The best control of the substrate roughness was achieved for bilayers of Al2O3 or AlN with mixed particle size, which reduced the roughness and prevented the diffusion of metals impurities but AlN bilayers exhibited as well the best electrical insulation properties.

  7. Investigation of Structure and Properties of Barrier Layers in Metals (Fe, Cu) at Low Temperatures

    Science.gov (United States)

    Kuterbekov, K. A.; Nurkenov, S. A.; Kislitsin, S. B.; Kuketayev, T. A.; Tussupbekova, A. K.

    2016-11-01

    Experimental studies of the effect of a barrier layer on the kinetics of thermally induced diffusion procesess and phase transformations in a layered Fe-Be syatem are investigated at the energy 1.6 MeV. Thermal stability of the barrier layer in the Fe:O+ system is validated and a possibility of its use as a subsurface layer for a beryllium coating is demonstrated. For the Cu:O+ system it is shown that the implanted layer in the matrix comes apart already at the annealing temperature 180°C and could not be used in a copper matrix as a subsurface barrier layer. For the first time, a method is proposed for retardation of diffusion and phase formation processes and realized in a layered iron - beryllium system using an implanted layer of oxygen ions. The sequence and characteristic times of thermally-induced phase-transformation processes taking place in the subsurface layers and in the bulk of the Fe (10 μm) systems: O+ - Be (0.7 μm) - 57Fe (0.1 μm) and Fe (10 μm) - Be (0.7 μm) - 57Fe (0.1 μm) are determined.

  8. Optimal deposition conditions of TiN barrier layers for the growth of vertically aligned carbon nanotubes onto metallic substrates

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Cespedes, J; Bertran, E [FEMAN Group, IN2UB, Departament de Fisica Aplicada i Optica, Universitat de Barcelona, C/ Martii Franques, 1, E-08028, Barcelona (Spain); Alvarez-Garcia, J [Centre de Recerca i Investigacio de Catalunya, S.A., Travessera de Gracia 108, Entressol, E-08012, Barcelona (Spain); Zhang, X; Hampshire, J [Teer Coatings Ltd, West Stone House, Berry Hill Industrial Estate, Droitwich, Worcestershire, WR9 9AS (United Kingdom)

    2009-05-21

    Plasma enhanced chemical deposition (PECVD) has proven over the years to be the preferred method for the growth of vertically aligned carbon nanotubes and nanofibres (VACNTs and VACNFs, respectively). In particular, carbon nanotubes (CNTs) grown on metallic surfaces present a great potential for high power applications, including low resistance electrical contacts, high power switches, electron guns or supercapacitors. Nevertheless, the deposition of CNTs onto metallic substrates is challenging, due to the intrinsic incompatibility between such substrates and the metallic precursor layers required to promote the growth of CNTs. In particular, the formation of CNT films is assisted by the presence of a nanometric (10-100 nm) monolayer of catalyst clusters, which act as nucleation sites for CNTs. The nanometric character of the precursor layer, together with the high growth temperature involved during the PECVD process ({approx}700 deg. C), strongly favours the in-diffusion of the catalyst nanoclusters into the bulk of the metallic substrate, which results in a dramatic reduction in the nucleation of CNTs. In order to overcome this problem, it is necessary to coat the metallic substrate with a diffusion barrier layer, prior to the growth of the catalyst precursor. Unlike other conventional ceramic barrier layers, TiN provides high electrical conductivity, thus being a promising candidate for use as barrier material in applications involving low resistance contacts. In this work we investigate the anti-diffusion properties of TiN sputtered coatings and its potential applicability to the growth of CNTs onto copper substrates, using Fe as catalyst material. The barrier and catalyst layers were deposited by magnetron sputtering. Auger electron spectroscopy was used to determine the diffusivity of Fe into TiN. Morphological characterization of the CNTs coatings was performed on scanning and transmission electron microscopes. Raman spectroscopy and x-ray diffraction were

  9. Analysis of Al diffusion processes in TiN barrier layers for the application in silicon solar cell metallization

    Science.gov (United States)

    Kumm, J.; Samadi, H.; Chacko, R. V.; Hartmann, P.; Wolf, A.

    2016-07-01

    An evaporated Al layer is known as an excellent rear metallization for highly efficient solar cells, but suffers from incompatibility with a common solder process. To enable solar cell-interconnection and module integration, in this work the Al layer is complemented with a solder stack of TiN/Ti/Ag or TiN/NiV/Ag, in which the TiN layer acts as an Al diffusion barrier. X-ray photoelectron spectroscopy measurements prove that diffusion of Al through the stack and the formation of an Al2O3 layer on the stack's surface are responsible for a loss of solderability after a strong post-metallization anneal, which is often mandatory to improve contact resistance and passivation quality. An optimization of the reactive TiN sputter process results in a densification of the TiN layer, which improves its barrier quality against Al diffusion. However, measurements with X-ray diffraction and scanning electron microscopy show that small grains with vertical grain boundaries persist, which still offer fast diffusion paths. Therefore, the concept of stuffing is introduced. By incorporating oxygen into the grain boundaries of the sputtered TiN layer, Al diffusion is strongly reduced as confirmed by secondary ion mass spectroscopy profiles. A quantitative analysis reveals a one order of magnitude lower Al diffusion coefficient for stuffed TiN layers. This metallization system maintains its solderability even after strong post-metallization annealing at 425 °C for 15 min. This paper thus presents an industrially feasible, conventionally solderable, and long-term stable metallization scheme for highly efficient silicon solar cells.

  10. Electroless deposition of NiCrB diffusion barrier layer film for ULSI-Cu metallization

    Science.gov (United States)

    Wang, Yuechun; Chen, Xiuhua; Ma, Wenhui; Shang, Yudong; Lei, Zhengtao; Xiang, Fuwei

    2017-02-01

    NiCrB films were deposited on Si substrates using electroless deposition as a diffusion barrier layer for Cu interconnections. Samples of the prepared NiCrB/SiO2/Si and NiCrB/Cu/NiCrB/SiO2/Si were annealed at temperatures ranging from 500 °C to 900 °C. The reaction mechanism of the electroless deposition of the NiCrB film, the failure temperature and the failure mechanism of the NiCrB diffusion barrier layer were investigated. The prepared samples were subjected to XRD, XPS, FPP and AFM to determine the phases, composition, sheet resistance and surface morphology of samples before and after annealing. The results of these analyses indicated that the failure temperature of the NiCrB barrier film was 900 °C and the failure mechanism led to crystallization and grain growth of the NiCrB barrier layer after high temperature annealing. It was found that this process caused Cu grains to reach Si substrate through the grain boundaries, and then the reaction between Cu and Si resulted in the formation of highly resistive Cu3Si.

  11. Method for forming a barrier layer

    Energy Technology Data Exchange (ETDEWEB)

    Weihs, Timothy P. (Baltimore, MD); Barbee, Jr., Troy W. (Palo Alto, CA)

    2002-01-01

    Cubic or metastable cubic refractory metal carbides act as barrier layers to isolate, adhere, and passivate copper in semiconductor fabrication. One or more barrier layers of the metal carbide are deposited in conjunction with copper metallizations to form a multilayer characterized by a cubic crystal structure with a strong (100) texture. Suitable barrier layer materials include refractory transition metal carbides such as vanadium carbide (VC), niobium carbide (NbC), tantalum carbide (TaC), chromium carbide (Cr.sub.3 C.sub.2), tungsten carbide (WC), and molybdenum carbide (MoC).

  12. High performance metal-supported solid oxide fuel cells with Gd-doped ceria barrier layers

    DEFF Research Database (Denmark)

    Klemensø, Trine; Nielsen, Jimmi; Blennow Tullmar, Peter

    2011-01-01

    Metal-supported solid oxide fuel cells are believed to have commercial advantages compared to conventional anode (Ni–YSZ) supported cells, with the metal-supported cells having lower material costs, increased tolerance to mechanical and thermal stresses, and lower operational temperatures. The im...

  13. Trapping gases in metal-organic frameworks with a selective surface molecular barrier layer

    Science.gov (United States)

    Tan, Kui; Zuluaga, Sebastian; Fuentes, Erika; Mattson, Eric C.; Veyan, Jean-François; Wang, Hao; Li, Jing; Thonhauser, Timo; Chabal, Yves J.

    2016-12-01

    The main challenge for gas storage and separation in nanoporous materials is that many molecules of interest adsorb too weakly to be effectively retained. Instead of synthetically modifying the internal surface structure of the entire bulk--as is typically done to enhance adsorption--here we show that post exposure of a prototypical porous metal-organic framework to ethylenediamine can effectively retain a variety of weakly adsorbing molecules (for example, CO, CO2, SO2, C2H4, NO) inside the materials by forming a monolayer-thick cap at the external surface of microcrystals. Furthermore, this capping mechanism, based on hydrogen bonding as explained by ab initio modelling, opens the door for potential selectivity. For example, water molecules are shown to disrupt the hydrogen-bonded amine network and diffuse through the cap without hindrance and fully displace/release the retained small molecules out of the metal-organic framework at room temperature. These findings may provide alternative strategies for gas storage, delivery and separation.

  14. Proactive control of the metal-ceramic interface behavior of thermal barrier coatings using an artificial alpha-Al2O 3 layer

    Science.gov (United States)

    Su, Yi-Feng

    The reliability and life of thermal barrier coatings (TBCs) used in the hottest sections of advanced aircraft engines and power generation systems are largely dictated by: (1) the ability of a metallic bond coating to form an adherent thermally grown oxide (TGO) at the metal-ceramic interface and (2) the rate at which the TGO grows upon oxidation. It is postulated that a thin alpha-Al2O3 layer, if it could be directly deposited on a Ni-based alloy, will guide the alloy surface to form a TGO that is more tenacious and slower growing than what is attainable with state-of-the-art bond coatings. A chemical vapor deposition (CVD) process was used to directly deposit an alpha-Al2O3 layer on the surface of a single crystal Ni-bases superalloy. The layer was 150 nm thick, and consisted of small columnar grains (˜100 to 200 nm) with alpha-Al2O 3 as the major phase with a minute amount of theta-Al2O 3. Within 0.5 h of oxidation at 1150°C, the resulting TGO formed on the alloy surface underwent significant lateral grain growth. Consequently, within this time scale, the columnar nature of the TGO became well established. After 50 h, a network of ridges was clearly observed on the TGO surface instead of equiaxed grains typically observed on uncoated alloy surface. Comparison of the TGO morphologies observed with and without the CVD-Al2O 3 layer suggested that the transient oxidation of the alloy surface was considerably reduced. The alloy coated with the CVD-Al2O 3 layer also produced a much more adherent and slow growing TGO in comparison to that formed on the uncoated alloy surface. The CVD-Al2O 3 layer also improved its spallation resistance. Without the CVD-Al 2O3 layer, more than 50% of the TGO spalled off the alloy surface after 500 h in oxidation with significant wrinkling of the TGO that remained on the alloy surface. In contrast, the TGO remained intact with the CVD-Al2O3 layer after the 500 h exposure. Furthermore, the CVD layer significantly reduced the degree of

  15. Comparative Study of SiO2, Al2O3, and BeO Ultrathin Interfacial Barrier Layers in Si Metal-Oxide-Semiconductor Devices

    Directory of Open Access Journals (Sweden)

    J. H. Yum

    2012-01-01

    Full Text Available In a previous study, we have demonstrated that beryllium oxide (BeO film grown by atomic layer deposition (ALD on Si and III-V MOS devices has excellent electrical and physical characteristics. In this paper, we compare the electrical characteristics of inserting an ultrathin interfacial barrier layer such as SiO2, Al2O3, or BeO between the HfO2 gate dielectric and Si substrate in metal oxide semiconductor capacitors (MOSCAPs and n-channel inversion type metal oxide semiconductor field effect transistors (MOSFETs. Si MOSCAPs and MOSFETs with a BeO/HfO2 gate stack exhibited high performance and reliability characteristics, including a 34% improvement in drive current, slightly better reduction in subthreshold swing, 42% increase in effective electron mobility at an electric field of 1 MV/cm, slightly low equivalent oxide thickness, less stress-induced flat-band voltage shift, less stress induced leakage current, and less interface charge.

  16. Barrier Coatings for Refractory Metals and Superalloys

    Energy Technology Data Exchange (ETDEWEB)

    SM Sabol; BT Randall; JD Edington; CJ Larkin; BJ Close

    2006-02-23

    In the closed working fluid loop of the proposed Prometheus space nuclear power plant (SNPP), there is the potential for reaction of core and plant structural materials with gas phase impurities and gas phase transport of interstitial elements between superalloy and refractory metal alloy components during service. Primary concerns are surface oxidation, interstitial embrittlement of refractory metals and decarburization of superalloys. In parallel with kinetic investigations, this letter evaluates the ability of potential coatings to prevent or impede communication between reactor and plant components. Key coating requirements are identified and current technology coating materials are reviewed relative to these requirements. Candidate coatings are identified for future evaluation based on current knowledge of design parameters and anticipated environment. Coatings were identified for superalloys and refractory metals to provide diffusion barriers to interstitial transport and act as reactive barriers to potential oxidation. Due to their high stability at low oxygen potential, alumina formers are most promising for oxidation protection given the anticipated coolant gas chemistry. A sublayer of iridium is recommended to provide inherent diffusion resistance to interstitials. Based on specific base metal selection, a thin film substrate--coating interdiffusion barrier layer may be necessary to meet mission life.

  17. Metal deposition using seed layers

    Science.gov (United States)

    Feng, Hsein-Ping; Chen, Gang; Bo, Yu; Ren, Zhifeng; Chen, Shuo; Poudel, Bed

    2013-11-12

    Methods of forming a conductive metal layers on substrates are disclosed which employ a seed layer to enhance bonding, especially to smooth, low-roughness or hydrophobic substrates. In one aspect of the invention, the seed layer can be formed by applying nanoparticles onto a surface of the substrate; and the metallization is achieved by electroplating an electrically conducting metal onto the seed layer, whereby the nanoparticles serve as nucleation sites for metal deposition. In another approach, the seed layer can be formed by a self-assembling linker material, such as a sulfur-containing silane material.

  18. On the porosity of barrier layers

    Directory of Open Access Journals (Sweden)

    J. Mignot

    2009-09-01

    Full Text Available Barrier layers are defined as the layer between the pycnocline and the thermocline when the latter are different as a result of salinity stratification. We present a revisited 2-degree resolution global climatology of monthly mean oceanic Barrier Layer (BL thickness first proposed by de Boyer Montégut et al. (2007. In addition to using an extended data set, we present a modified computation method that addresses the observed porosity of BLs. We name porosity the fact that barrier layers distribution can, in some areas, be very uneven regarding the space and time scales that are considered. This implies an intermittent alteration of air-sea exchanges by the BL. Therefore, it may have important consequences for the climatic impact of BLs. Differences between the two computation methods are small for robust BLs that are formed by large-scale processes. However, the former approach can significantly underestimate the thickness of short and/or localized barrier layers. This is especially the case for barrier layers formed by mesoscale mechanisms (under the intertropical convergence zone for example and along western boundary currents and equatorward of the sea surface salinity subtropical maxima. Complete characterisation of regional BL dynamics therefore requires a description of the robustness of BL distribution to assess the overall impact of BLs on the process of heat exchange between the ocean interior and the atmosphere.

  19. Determination of the Potential Barrier at the Metal/Oxide Interface in a Specular Spin Valve Structure with Nano-oxide Layers Using Electron Holography

    Institute of Scientific and Technical Information of China (English)

    王岩国; 沈峰; 张泽; 蔡建旺; 赖武彦

    2002-01-01

    The local potential distribution in a specular spin valve structure with nano-oxide layers has been mapped byusing off-axis electron holography in a field emission gun transmission electron microscope. A potential jumpof 3-4 V across the metal/oxide interface was detected for the first time. The presence of the potential barrierconfirms the formation of the metal/insulator/metal structure, which contributes to the increasing mean free pathof spin-polarized electrons via the specular reflection of spin-polarized electrons at the metal/oxide interface. Itleads to nearly double enhancement of the magnetoresistance ratio from 8% to 15%.

  20. Composite layers for barrier coatings on polymers

    Science.gov (United States)

    Brochhagen, Markus; Vorkoetter, Christoph; Boeke, Marc; Benedikt, Jan

    2016-09-01

    Amorphous hydrogenated carbon (a-C:H), amorphous hydrogenated silicon (a-Si:H), and SiO2 thin films are of high interest because they can serve as a gas barrier on polymers. To understand how the coating changes the overall barrier properties of the thin film-polymer system, optical, mechanical, and barrier properties have to be studied. One of the important characteristic of such coatings is their compressive stress, which has beneficial as well as unwanted effects. The stress can cause deformation of the bulk material or de-lamination of the film. The mechanical stability can be improved and it is possible to reduce cracking due to elongation, as the compressive stress can compensate externally applied tensile strain. Stress and mechanical properties of composite layers can be manipulated directly by embedding nanoparticles in an amorphous matrix film. Therefore nanoparticles and amorphous layers are investigated before they can be assembled in a composite layer. Growth rates as well as optical and mechanical properties are explored in this work. An inductively coupled plasma source was used for all amorphous layers and the silicon nanoparticles with diameter around 5 nm were produced in a capacitively coupled plasma reactor. This work is supported by DFG within SFB-TR87.

  1. Improved metallic and thermal barrier coatings

    Science.gov (United States)

    Stecura, S.

    1981-01-01

    Low thermal conductivity two layer ceramic coatings are efficient thermal barriers between cooled matallic components and high temperature combustion gases. Potential components are combustors, blades, and vanes in aircraft engines of power-generating turbines. Presence of two layer coatings greatly reduces temperature and coolant requirements.

  2. Nanostructured zirconia layers as thermal barrier coatings

    Directory of Open Access Journals (Sweden)

    Radu Robert PITICESCU

    2011-09-01

    Full Text Available The coatings obtained by thermal spray are used both as antioxidant and connection materials (e.g. MCrAlY type alloys as well as thermal barrier coatings (e.g. partially stabilized zirconia oxide with yttria oxide. This paper studies the characteristics of the coatings obtained with nanostructured powders by thermal spraying and air plasma jet metallization. Testing of coatings is done against the most disturbing factor, thermal shock. Structural changes occurring after thermal shock tests are highlighted by investigations of optical and electronic microscopy. The results obtained after quick thermal shock show a good morphological and surface behavior of the developed coatings.

  3. Tungsten-titanium diffusion barriers for silver metallization

    Energy Technology Data Exchange (ETDEWEB)

    Bhagat, Shekhar [Department of Chemical and Materials Engineering, Arizona State University, Tempe, Arizona 85287-6006 (United States); Han, Hauk [Science and Engineering of Materials Program, Center for Solid State Science, Arizona State University, Tempe, Arizona 85287-1706 (United States); Alford, T.L. [Department of Chemical and Materials Engineering, Arizona State University, Tempe, Arizona 85287-6006 (United States)]. E-mail: alford@asu.edu

    2006-12-05

    Diffusion barrier properties and thermal stability of reactive sputtered W-Ti films between Ag and Si were studied using X-ray diffractometry, X-ray fluorescence spectrometry, Rutherford backscattering spectrometry, four point probe analysis, and field emission scanning electron microscopy. These films were annealed in vacuum at different temperatures for 1 h. Silver layers were found to be stable up to 600 deg. C; after which, Ag agglomerated at 700 deg. C. Rutherford backscattering analysis showed that interfacial reactions took place at temperatures higher than 400 deg. C. Four point probe resistivity measurements showed that the films were stable up to 600 deg. C. At 700 deg. C the resistivity increased abnormally. These results support further investigation of W-Ti films as a potential barrier layer for Ag metallization in the high temperature electronics.

  4. Microstructures and Mechanical Properties of Ceramic/Metal Gradient Thermal Barrier Coatings

    Institute of Scientific and Technical Information of China (English)

    XIAO Jin-sheng; JIANG Bing; LIU Jie; HUANG Shi-yong

    2003-01-01

    The ceramic/metal gradient thermal barrier coatings (CMGTBCs) which combined the conceptions of thermal barrier coatings ( TBG ) and functional gradient materials ( FGMs ) are investigated. The structure model studied in this paper is a general model which includes four different layers: pure ceramic layer , ceramic/metal gradient layer, pure metal layer, and substrate layer. The microstructures of gradient layer have different ceramics and metal volume fraction profile along with the direction of thickness. The profile function used to describe the gradient microstructures can be expressed in power-law or polynomial expression. The mechanical properties of CMGTBCs are obtained by means of microscopic mechanics. As special cases, the interactive solutions are given by Mori- Tanaka method, and the non- interactive solutions by dilute solution. The Young's modulus calculated by these methods are compared with those by other methods , e g, the rule of mixtures.

  5. Superconductivity in Layered Organic Metals

    Directory of Open Access Journals (Sweden)

    Jochen Wosnitza

    2012-04-01

    Full Text Available In this short review, I will give an overview on the current understanding of the superconductivity in quasi-two-dimensional organic metals. Thereby, I will focus on charge-transfer salts based on bis(ethylenedithiotetrathiafulvalene (BEDT-TTF or ET for short. In these materials, strong electronic correlations are clearly evident, resulting in unique phase diagrams. The layered crystallographic structure leads to highly anisotropic electronic as well as superconducting properties. The corresponding very high orbital critical field for in-plane magnetic-field alignment allows for the occurrence of the Fulde–Ferrell– Larkin–Ovchinnikov state as evidenced by thermodynamic measurements. The experimental picture on the nature of the superconducting state is still controversial with evidence both for unconventional as well as for BCS-like superconductivity.

  6. Brain barrier systems: a new frontier in metal neurotoxicological research

    OpenAIRE

    Zheng, Wei; Aschner, Michael; Ghersi-Egea, Jean-Francois

    2003-01-01

    The concept of brain barriers or a brain barrier system embraces the blood–brain interface, referred to as the blood–brain barrier, and the blood–cerebrospinal fluid (CSF) interface, referred to as the blood–CSF barrier. These brain barriers protect the CNS against chemical insults, by different complementary mechanisms. Toxic metal molecules can either bypass these mechanisms or be sequestered in and therefore potentially deleterious to brain barriers. Supportive evidence suggests that damag...

  7. Ocean barrier layers' effect on tropical cyclone intensification.

    Science.gov (United States)

    Balaguru, Karthik; Chang, Ping; Saravanan, R; Leung, L Ruby; Xu, Zhao; Li, Mingkui; Hsieh, Jen-Shan

    2012-09-04

    Improving a tropical cyclone's forecast and mitigating its destructive potential requires knowledge of various environmental factors that influence the cyclone's path and intensity. Herein, using a combination of observations and model simulations, we systematically demonstrate that tropical cyclone intensification is significantly affected by salinity-induced barrier layers, which are "quasi-permanent" features in the upper tropical oceans. When tropical cyclones pass over regions with barrier layers, the increased stratification and stability within the layer reduce storm-induced vertical mixing and sea surface temperature cooling. This causes an increase in enthalpy flux from the ocean to the atmosphere and, consequently, an intensification of tropical cyclones. On average, the tropical cyclone intensification rate is nearly 50% higher over regions with barrier layers, compared to regions without. Our finding, which underscores the importance of observing not only the upper-ocean thermal structure but also the salinity structure in deep tropical barrier layer regions, may be a key to more skillful predictions of tropical cyclone intensities through improved ocean state estimates and simulations of barrier layer processes. As the hydrological cycle responds to global warming, any associated changes in the barrier layer distribution must be considered in projecting future tropical cyclone activity.

  8. Silicon based substrate with environmental/thermal barrier layer

    Science.gov (United States)

    Eaton, Jr., Harry Edwin (Inventor); Allen, William Patrick (Inventor); Jacobson, Nathan S. (Inventor); Bansal, Narottam P. (Inventor); Opila, Elizabeth J. (Inventor); Smialek, James L. (Inventor); Lee, Kang N. (Inventor); Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Meschter, Peter Joel (Inventor)

    2002-01-01

    A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a barium-strontium alumino silicate.

  9. Polymer/layered silicates nanocomposites for barrier technology

    CSIR Research Space (South Africa)

    Labuschagne, Philip W

    2012-02-01

    Full Text Available -1 Intelligent Nanomaterials: Processes, Properties, and Applications February 2012/Chapter 13 Polymer/layered silicates nanocomposites for barrier technology Labuschagne, PW, Moolman, S and Maity, A. Corresponding author: PLabusch...

  10. Silicon based substrate with environmental/ thermal barrier layer

    Science.gov (United States)

    Eaton, Jr., Harry Edwin (Inventor); Allen, William Patrick (Inventor); Jacobson, Nathan S. (Inventor); Bansal, Nanottam P. (Inventor); Opila, Elizabeth J. (Inventor); Smialek, James L. (Inventor); Lee, Kang N. (Inventor); Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Meschter, Peter Joel (Inventor)

    2002-01-01

    A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a barium-strontium alumino silicate.

  11. Silicon based substrate with calcium aluminosilicate/thermal barrier layer

    Science.gov (United States)

    Eaton, Jr., Harry Edwin (Inventor); Allen, William Patrick (Inventor); Miller, Robert Alden (Inventor); Jacobson, Nathan S. (Inventor); Smialek, James L. (Inventor); Opila, Elizabeth J. (Inventor); Lee, Kang N. (Inventor); Nagaraj, Bangalore A. (Inventor); Wang, Hongyu (Inventor); Meschter, Peter Joel (Inventor)

    2001-01-01

    A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a calcium alumino silicate.

  12. Preparation and characterization of TiO2 barrier layers for dye-sensitized solar cells.

    Science.gov (United States)

    Zheng, Yichen; Klankowski, Steven; Yang, Yiqun; Li, Jun

    2014-07-09

    A TiO2 barrier layer is critical in enhancing the performance of dye-sensitized solar cells (DSSCs). Two methods to prepare the TiO2 barrier layer on fluorine-doped tin dioxide (FTO) surface were systematically studied in order to minimize electron-hole recombination and electron backflow during photovoltaic processes of DSSCs. The film structure and materials properties were correlated with the photovoltaic characteristics and electrochemical properties. In the first approach, a porous TiO2 layer was deposited by wet chemical treatment of the sample with TiCl4 solution for time periods varying from 0 to 60 min. The N719 dye molecules were found to be able to insert into the porous barrier layers. The 20 min treatment formed a nonuniform but intact TiO2 layer of ∼100-300 nm in thickness, which gave the highest open-circuit voltage VOC, short-circuit photocurrent density JSC, and energy conversion efficiency. But thicker TiO2 barrier layers by this method caused a decrease in JSC, possibly limited by lower electrical conductance. In the second approach, a compact TiO2 barrier layer was created by sputter-coating 0-15 nm Ti metal films on FTO/glass and then oxidizing them into TiO2 with thermal treatment at 500 °C in the air for 30 min. The dye molecules were found to only attach at the outer surface of the barrier layer and slightly increased with the layer thickness. These two kinds of barrier layer showed different characteristics and may be tailored for different DSSC studies.

  13. Remote forcing annihilates barrier layer in southeastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Shenoi, S.S.C.; Shankar, D.; Shetye, S.R.

    -1 GEOPHYSICAL RESEARCH LETTERS, VOL. ???, XXXX, DOI:10.1029/, Remote forcing annihilates barrier layer in southeastern Arabian Sea S. S. C. Shenoi, D. Shankar, and S. R. Shetye National Institute of Oceanography, Goa, India. Time-series measurements... thick barrier layer (BL) exists during March{April ow- ing to a surface layer of low-salinity waters advected earlier during December{January from the Bay of Bengal. The BL is almost annihilated by 7 April owing to upwelling. The relic BL that survives...

  14. Cathode-Electrolyte Interfaces with CGO Barrier Layers in SOFC

    DEFF Research Database (Denmark)

    Knibbe, Ruth; Hjelm, Johan; Menon, Mohan

    2010-01-01

    Electron microscopy characterization across the cathode–electrolyte interface of two different types of intermediate temperature solid oxide fuel cells (IT-SOFC) is performed to understand the origin of the cell performance disparity. One IT-SOFC cell had a sprayed-cosintered Ce0.90Gd0.01O1.95 (CGO......10) barrier layer, the other had a barrier layer deposited by pulsed laser deposition (PLD) CGO10. Scanning electron microscopy, transmission electron microscopy (TEM), and electron backscattered diffraction (EBSD) investigations conclude that the major source of the cell performance difference...... is attributed to CGO–YSZ interdiffusion in the sprayed-cosintered barrier layer. From TEM and EBSD work, a dense CGO10 PLD layer is found to be deposited epitaxially on the 8YSZ electrolyte substrate—permitting a small amount of SrZrO3 formation and minimizing CGO–YSZ interdiffusion....

  15. Ultraviolet photodetectors based on ZnO nanorods-seed layer effect and metal oxide modifying layer effect

    Directory of Open Access Journals (Sweden)

    Zhou Hai

    2011-01-01

    Full Text Available Abstract Pt/ZnO nanorod (NR and Pt/modified ZnO NR Schottky barrier ultraviolet (UV photodetectors (PDs were prepared with different seed layers and metal oxide modifying layer materials. In this paper, we discussed the effect of metal oxide modifying layer on the performance of UV PDs pre- and post-deposition annealing at 300°C, respectively. For Schottky barrier UV PDs with different seed layers, the MgZnO seed layer-PDs without metal oxide coating showed bigger responsivity and larger detectivity (Dλ* than those of PDs with ZnO seed layer, and the reason was illustrated through energy band theory and the electron transport mechanism. Also the ratio of D254* to D546* was calculated above 8 × 102 for all PDs, which demonstrated that our PDs showed high selectivity for detecting UV light with less influence of light with long wavelength.

  16. Ultraviolet photodetectors based on ZnO nanorods-seed layer effect and metal oxide modifying layer effect.

    Science.gov (United States)

    Zhou, Hai; Fang, Guojia; Liu, Nishuang; Zhao, Xingzhong

    2011-02-15

    Pt/ZnO nanorod (NR) and Pt/modified ZnO NR Schottky barrier ultraviolet (UV) photodetectors (PDs) were prepared with different seed layers and metal oxide modifying layer materials. In this paper, we discussed the effect of metal oxide modifying layer on the performance of UV PDs pre- and post-deposition annealing at 300°C, respectively. For Schottky barrier UV PDs with different seed layers, the MgZnO seed layer-PDs without metal oxide coating showed bigger responsivity and larger detectivity (Dλ*) than those of PDs with ZnO seed layer, and the reason was illustrated through energy band theory and the electron transport mechanism. Also the ratio of D254* to D546* was calculated above 8 × 102 for all PDs, which demonstrated that our PDs showed high selectivity for detecting UV light with less influence of light with long wavelength.

  17. Behavior of alumina barrier layer in the supporting electrolytes for deposition of nanowired materials

    Energy Technology Data Exchange (ETDEWEB)

    Jagminas, Arunas, E-mail: jagmin@ktl.mii.l [Institute of Chemistry, A. Gostauto 9, 01108 Vilnius (Lithuania); Cesuniene, Asta [Institute of Chemistry, A. Gostauto 9, 01108 Vilnius (Lithuania); Vrublevsky, Igor [Department of Microelectronics, Belarusian State University of Informatics and Radioelectronics, 6 Brovka str, Minsk 220013 (Belarus); Jasulaitiene, Vitalija; Ragalevicius, Rimas [Institute of Chemistry, A. Gostauto 9, 01108 Vilnius (Lithuania)

    2010-03-30

    In this study, we report the results obtained investigating the behavior of sulfuric and chromic acid alumina templates in typical supporting electrolytes frequently used for alternating current (ac) deposition of various nm-scaled materials. Qualitative analysis of voltammetric profiles taken for as-grown, ac-treated and annealed alumina films in a conventional tetraborate re-anodizing solution revealed dramatical changes in the properties of alumina barrier layer during ac treatment in these supporting electrolytes even at low current density. These changes were related here with the transport of protons through the barrier layer during ac treatment, discharge at the metal/oxide interface and hydrogenation of alumina material by hydrogen atoms in an upward way. This conclusion comes from the behavior of Pt/Hg|alumina|Me{sup z+} electrode and the valence band X-ray photoelectron spectra taken from the inner part of alumina barrier layer material before and after the ac treatment.

  18. Fundamental Investigations Regarding Barrier Properties of Grafted PVOH Layers

    Directory of Open Access Journals (Sweden)

    Markus Schmid

    2012-01-01

    Full Text Available The current work focuses on fundamental investigations regarding the barrier properties of grafted PVOH layers produced by the Transfer Method. The layers (or papers used for the different experiments were produced and grafted during the course of this work. Papers with different types of PVOH (different Mowiol types were produced by coating. Experiments using different parameters (temperature, reaction duration, and concentration were performed using the Transfer Method. Contact angle measurements and Cobb60 measurements were carried out on the grafted and untreated PVOH layers. Furthermore, the water vapour transmission rate of the PVOH layers was determined. The results of this work showed that the method of chromatogeny or chromatogenic chemistry improves the water vapour barrier properties of grafted PVOH layers enormously.

  19. Arabian Sea Fronts and Barrier Layers

    Science.gov (United States)

    2015-09-30

    Shcherbina Applied Physics Laboratory 1013 NE 40th St. Seattle, WA 98105 phone: (206)897-1446 fax: (206)543-6785 email: ashcherbina...science questions are: 1. What combination of air-sea interactions and upper-ocean physical processes control mixed layer properties and upper ocean...to identify the optimal experimental site will commence in late 2015, tentatively followed by a reconnaissance deployment of autonomous instruments

  20. Room Temperature Magnetic Barrier Layers in Magnetic Tunnel Junctions

    Energy Technology Data Exchange (ETDEWEB)

    Nelson-Cheeseman, B. B.; Wong, F. J.; Chopdekar, R. V.; Arenholz, E.; Suzuki, Y.

    2010-03-09

    We investigate the spin transport and interfacial magnetism of magnetic tunnel junctions with highly spin polarized LSMO and Fe3O4 electrodes and a ferrimagnetic NiFe2O4 (NFO) barrier layer. The spin dependent transport can be understood in terms of magnon-assisted spin dependent tunneling where the magnons are excited in the barrier layer itself. The NFO/Fe3O4 interface displays strong magnetic coupling, while the LSMO/NFO interface exhibits clear decoupling as determined by a combination of X-ray absorption spectroscopy and X-ray magnetic circular dichroism. This decoupling allows for distinct parallel and antiparallel electrode states in this all-magnetic trilayer. The spin transport of these devices, dominated by the NFO barrier layer magnetism, leads to a symmetric bias dependence of the junction magnetoresistance at all temperatures.

  1. Roughness of laser deposited metal / metal oxide layered structures

    Energy Technology Data Exchange (ETDEWEB)

    Liese, Tobias; Meschede, Andreas; Roeder, Johanna; Krebs, Hans-Ulrich [Institut fuer Materialphysik, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany)

    2007-07-01

    The roughness of laser deposited Ti/MgO and Ag/ZrO{sub 2} layered thin films were investigated by atomic force microscopy (AFM) and X-ray reflectivity (XRR), which are sensitive on the surface and interface roughness, respectively. When depositing the metals, nucleation and island growth occur which first roughen the surfaces with increasing layer thickness. Then, coalescence and island zipping processes reduce the roughness again. Minimal roughness is reached, when the metal layers are just closed. In both systems, the deposition of the metal oxide leads to layer smoothing. The underlying growth processes for single and double layers as well as the reduction of roughness in multilayers are discussed.

  2. Atomic layer deposition on polymer based flexible packaging materials: Growth characteristics and diffusion barrier properties

    Energy Technology Data Exchange (ETDEWEB)

    Kaeaeriaeinen, Tommi O., E-mail: tommi.kaariainen@lut.f [ASTRaL, Lappeenranta University of Technology, Prikaatinkatu 3 E, 50100 Mikkeli (Finland); Maydannik, Philipp, E-mail: philipp.maydannik@lut.f [ASTRaL, Lappeenranta University of Technology, Prikaatinkatu 3 E, 50100 Mikkeli (Finland); Cameron, David C., E-mail: david.cameron@lut.f [ASTRaL, Lappeenranta University of Technology, Prikaatinkatu 3 E, 50100 Mikkeli (Finland); Lahtinen, Kimmo, E-mail: kimmo.lahtinen@tut.f [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 541, 33101 Tampere (Finland); Johansson, Petri, E-mail: petri.johansson@tut.f [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 541, 33101 Tampere (Finland); Kuusipalo, Jurkka, E-mail: jurkka.kuusipalo@tut.f [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 541, 33101 Tampere (Finland)

    2011-03-01

    One of the most promising areas for the industrial application of atomic layer deposition (ALD) is for gas barrier layers on polymers. In this work, a packaging material system with improved diffusion barrier properties has been developed and studied by applying ALD on flexible polymer based packaging materials. Nanometer scale metal oxide films have been applied to polymer-coated papers and their diffusion barrier properties have been studied by means of water vapor and oxygen transmission rates. The materials for the study were constructed in two stages: the paper was firstly extrusion coated with polymer film, which was then followed by the ALD deposition of oxide layer. The polymers used as extrusion coatings were polypropylene, low and high density polyethylene, polylactide and polyethylene terephthalate. Water vapor transmission rates (WVTRs) were measured according to method SCAN-P 22:68 and oxygen transmission rates (O{sub 2}TRs) according to a standard ASTM D 3985. According to the results a 10 nm oxide layer already decreased the oxygen transmission by a factor of 10 compared to uncoated material. WVTR with 40 nm ALD layer was better than the level currently required for most common dry flexible packaging applications. When the oxide layer thickness was increased to 100 nm and above, the measured WVTRs were limited by the measurement set up. Using an ALD layer allowed the polymer thickness on flexible packaging materials to be reduced. Once the ALD layer was 40 nm thick, WVTRs and O{sub 2}TRs were no longer dependent on polymer layer thickness. Thus, nanometer scale ALD oxide layers have shown their feasibility as high quality diffusion barriers on flexible packaging materials.

  3. Atomic Layer Deposition Films as Diffusion Barriers for Silver Artifacts

    Science.gov (United States)

    Marquardt, Amy; Breitung, Eric; Drayman-Weisser, Terry; Gates, Glenn; Rubloff, Gary W.; Phaneuf, Ray J.

    2012-02-01

    Atomic layer deposition (ALD) was investigated as a means to create transparent oxide diffusion barrier coatings to reduce the rate of tarnishing for silver objects in museum collections. Accelerated aging by heating various thicknesses (5 to 100nm) of ALD alumina (Al2O3) thin films on sterling and fine silver was used to determine the effectiveness of alumina as a barrier to silver oxidation. The effect of aging temperature on the thickness of the tarnish layer (Ag2S) created at the interface of the ALD coating and the bulk silver substrate was determined by reflectance spectroscopy and X-Ray Photoelectric Spectroscopy (XPS). Reflectance spectroscopy was an effective rapid screening tool to determine tarnishing rates and the coating's visual impact. X-Ray Photoelectric Spectroscopy (XPS), and Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) analysis showed a phase transformation in the Ag2S tarnish layer at 177 C and saturation in the thickness of the silver sulfide layer, indicating possible self-passivation of the tarnish layer.

  4. Lightweight Absorption and Barrier Systems Comprising N-Layer Microperforates

    OpenAIRE

    Kim, Nicholas N; Bolton, J. Stuart

    2017-01-01

    Since the concept of microperforated panels (MPPs) was introduced by Maa, there have been continuing efforts to apply MPPs, primarily as fiber-free sound absorbing materials, typically wall-mounted. The objective of the present work was to demonstrate that multi-layer MPPs can also be effective functional absorbers and lightweight barrier systems. The acoustical properties of lightweight MPPs depend on hole diameter, thickness, porosity, mass per unit area, and air cavity depth. In the case o...

  5. Buffer layers on biaxially textured metal substrates

    Science.gov (United States)

    Shoup, Shara S.; Paranthamam, Mariappan; Beach, David B.; Kroeger, Donald M.; Goyal, Amit

    2001-01-01

    A method is disclosed for forming a biaxially textured buffer layer on a biaxially oriented metal substrate by using a sol-gel coating technique followed by pyrolyzing/annealing in a reducing atmosphere. This method is advantageous for providing substrates for depositing electronically active materials thereon.

  6. Synthesis of tantalum nitride diffusion barriers for Cu metal by plasma immersion ion implantation

    CERN Document Server

    Kumar, M; Kumar, D; George, P J; Paul, A K

    2002-01-01

    A Tantalum nitride diffusion barrier layer for copper metal was synthesized by Plasma Immersion Ion Implantation technique (PIII). Effect of nitrogen dose in Ta layer was investigated in improving its diffusion barrier properties. Silicon wafers coated with Ta were implanted with nitrogen at two different doses viz. 10$^{15}$ions/cm$^2$ and 10$^{17}$ions/cm$^2$ corresponding to low and high dose regime. High dose of implanted nitrogen ions in the film render it to become Ta(N), Thereafter a copper (Cu) layer was deposited on the samples to produce Cu/Ta(N)/Si structure. To evaluate the barrier properties of Ta(N) these samples were annealed up to 700$^\\circ$C for 30 minutes. Sheet resistance, X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) measurements were carried out to investigate the effect of annealing. Low dose implanted Ta layer does not show any change in its diffusion barrier properties, while high dose implanted layer stops the diffusion of Cu metal through it at annealing temperature...

  7. Magnetron sputtered gadolinia-doped ceria diffusion barriers for metal-supported solid oxide fuel cells

    DEFF Research Database (Denmark)

    Sønderby, Steffen; Klemensø, Trine; Christensen, Bjarke H.

    2014-01-01

    Gadolinia-doped ceria (GDC) thin films are deposited by reactive magnetron sputtering in an industrial-scale setup and implemented as barrier layers between the cathode and electrolyte in metal-based solid oxide fuel cells consisting of a metal support, an electrolyte of ZrO2 co-doped with Sc2O3...... and substrate bias voltage. A GDC layer thickness of 0.6 μm is found to effectively block Sr diffusion when bias voltage and deposition temperature is tuned to promote dense coatings. The adatom mobility has a large influence on the film density. Low temperature and bias voltage result in underdense column...

  8. Barrier enhancement of Ge MSM IR photodetector with Ge layer optimization

    Science.gov (United States)

    Asar, Tarık; Özçelik, Süleyman

    2015-12-01

    Germanium thin films were deposited on n-type Silicon substrates with three different sputter power by using DC magnetron sputtering system at room temperature. The structural and morphological properties of the samples have been obtained by means of X-ray diffraction and atomic force microscopy measurements. Then, Germanium metal-semiconductor-metal infrared photodetectors were fabricated on these structures. The carrier recombination lifetime and the diffusion length of the devices were also calculated by using the carrier density and mobility data was obtained from the room temperature Hall Effect measurements. The dark current-voltage measurements of devices were achieved at room temperature. The electrical parameters such as ideality factor, Schottky barrier height, saturation current and series resistance were extracted from dark current-voltage characteristics. Finally, it has been shown that the barrier enhancement of Ge MSM IR photodetector can be achieved by Ge layer optimization.

  9. Preparation of Thin Metal Layers on Polymers

    Directory of Open Access Journals (Sweden)

    J. Siegel

    2007-01-01

    Full Text Available Continuous gold layers of increasing thickness were prepared by the vacuum deposition method on pristine and plasma modified sheets of  PE, PET and PTFE. Various surface profiles were obtained. The surface morphology was studied using atomic force microscopy (AFM. The continuity of the metal layer on the polymer surface was validated by measuring its electrical resistance. Changes in the wettability of the plasma treated polymers were evaluated by measuring the aging curves. These were obtained as the dependence of contact angle on ageing time. 

  10. Tailoring capping layers to reduce stress gradients in copper metallization

    Science.gov (United States)

    Murray, Conal E.; Priyadarshini, Deepika; Nguyen, Son; Ryan, E. Todd

    2016-12-01

    Capping layers for back-end-of-line metallization, which primarily serve as diffusion barriers to prevent contamination, also play a role in mitigating electromigration in the underlying conductive material. Stress gradients can be generated in copper metallization due to the conditions associated with the capping process. To study the effects of deposition and subsequent annealing on the mechanical response of copper films with various capping schemes, we employed a combination of conventional and glancing incidence X-ray diffraction techniques to quantify the stress gradient maxima. The Cu films with dielectric caps, such as silicon nitride, can exhibit large gradients that decrease slightly with thermal cycling. However, Co and TaN-based metallic capping layers create significantly lower stress gradient maxima in copper features both before and after annealing. The different evolution of stress gradients in Cu films with dielectric and metallic caps due to thermal cycling reveals the interaction of dislocation-mediated, plastic deformation with the cap/Cu interface.

  11. Schottky barriers at metal-finite semiconducting carbon nanotube interfaces

    OpenAIRE

    Xue, Yongqiang; Ratner, Mark A.

    2003-01-01

    Electronic properties of metal-finite semiconducting carbon nanotube interfaces are studied as a function of the nanotube length using a self-consistent tight-binding theory. We find that the shape of the potential barrier depends on the long-range tail of the charge transfer, leading to an injection barrier thickness comparable to half of the nanotube length until the nanotube reaches the bulk limit. The conductance of the nanotube junction shows a transition from tunneling to thermally-acti...

  12. Advanced atom chips with two metal layers.

    Energy Technology Data Exchange (ETDEWEB)

    Stevens, James E.; Blain, Matthew Glenn; Benito, Francisco M.; Biedermann, Grant

    2010-12-01

    A design concept, device layout, and monolithic microfabrication processing sequence have been developed for a dual-metal layer atom chip for next-generation positional control of ultracold ensembles of trapped atoms. Atom chips are intriguing systems for precision metrology and quantum information that use ultracold atoms on microfabricated chips. Using magnetic fields generated by current carrying wires, atoms are confined via the Zeeman effect and controllably positioned near optical resonators. Current state-of-the-art atom chips are single-layer or hybrid-integrated multilayer devices with limited flexibility and repeatability. An attractive feature of multi-level metallization is the ability to construct more complicated conductor patterns and thereby realize the complex magnetic potentials necessary for the more precise spatial and temporal control of atoms that is required. Here, we have designed a true, monolithically integrated, planarized, multi-metal-layer atom chip for demonstrating crossed-wire conductor patterns that trap and controllably transport atoms across the chip surface to targets of interest.

  13. ANTIREFLECTION MULTILAYER COATINGS WITH THIN METAL LAYERS

    OpenAIRE

    L. A. Gubanova

    2016-01-01

    The design of anti-reflective coatings for metal surfaces of Al, Ti, N,i Cr is proposed. The coatings have the form of alternating layers of dielectric/metal/dielectric with the number of cells up to15. The method of calculation of such coatings is proposed. We have calculated the coatings of the type [HfO2/Cr/HfO2]15, [ZrO2/Ti/Al2O3]15, [ZrO2/Cr/ZrO2]15. It is shown that the proposed interference coatings provide reduction of the residual reflectance of the metal several times (from 3.5 to 6...

  14. ANTIREFLECTION MULTILAYER COATINGS WITH THIN METAL LAYERS

    Directory of Open Access Journals (Sweden)

    L. A. Gubanova

    2016-03-01

    Full Text Available The design of anti-reflective coatings for metal surfaces of Al, Ti, N,i Cr is proposed. The coatings have the form of alternating layers of dielectric/metal/dielectric with the number of cells up to15. The method of calculation of such coatings is proposed. We have calculated the coatings of the type [HfO2/Cr/HfO2]15, [ZrO2/Ti/Al2O3]15, [ZrO2/Cr/ZrO2]15. It is shown that the proposed interference coatings provide reduction of the residual reflectance of the metal several times (from 3.5 to 6.0 in a wide spectral range (300-1000 nm. The proposed coatings can be recommended as anti-reflective coatings for energy saving solar systems and batteries, and photovoltaic cells.

  15. Thermal stability of atomic layer deposited Ru layer on Si and TaN/Si for barrier application of Cu interconnection.

    Science.gov (United States)

    Shin, Dong Chan; Kim, Moo Ryul; Lee, Jong Ho; Choi, Bum Ho; Lee, Hong Kee

    2012-07-01

    The thermal stability of thin Ru single layer and Ru/TaN bilayers grown on bare Si by plasma enhanced atomic layer deposition (PEALD) have been studied with Cu/Ru, Cu/Ru/TaN structures as a function of annealing temperature. To investigate the characteristics as a copper diffusion barrier, a 50 nm thick Cu film was sputtered on Ru and Ru/TaN layers and each samples subjected to thermal annealing under N2 ambient with varied temperature 300, 400, and 500 degrees C, respectively. It was found that the single 5 nm thick ALD Ru layer acted as an effective Cu diffusion barrier up to 400 degrees C. On the other hand ALD Ru (5 nm)/TaN (3.2 nm) showed the improved diffusion barrier characteristics even though the annealing temperature increased up to 500 degrees C. Based on the experimental results, the failure mechanism of diffusion barrier would be related to the crystallization of amorphous Ru thin film as temperature raised which implies the crystallized Ru grain boundary served as the diffusion path of Cu atoms. The combination of ALD Ru incorporated with TaN layer would be a promising barrier structure in Cu metallization.

  16. Enhanced efficiency of Schottky-barrier solar cell with periodically nonhomogeneous indium gallium nitride layer

    Science.gov (United States)

    Anderson, Tom H.; Mackay, Tom G.; Lakhtakia, Akhlesh

    2017-01-01

    A two-dimensional finite-element model was developed to simulate the optoelectronic performance of a Schottky-barrier solar cell. The heart of this solar cell is a junction between a metal and a layer of n-doped indium gallium nitride (InξGaN) alloy sandwiched between a reflection-reducing front window and a periodically corrugated metallic back reflector. The bandgap of the InξGaN layer was varied periodically in the thickness direction by varying the parameter ξ∈(0,1). First, the frequency-domain Maxwell postulates were solved to determine the spatial profile of photon absorption and, thus, the generation of electron-hole pairs. The AM1.5G solar spectrum was taken to represent the incident solar flux. Next, the drift-diffusion equations were solved for the steady-state electron and hole densities. Numerical results indicate that a corrugated back reflector of a period of 600 nm is optimal for photon absorption when the InξGaN layer is homogeneous. The efficiency of a solar cell with a periodically nonhomogeneous InξGaN layer may be higher by as much as 26.8% compared to the analogous solar cell with a homogeneous InξGaN layer.

  17. Thermal stability of tungsten-titanium diffusion barriers for silver metallization

    Energy Technology Data Exchange (ETDEWEB)

    Bhagat, S.K. [School of Materials, Arizona State University, Tempe, Arizona (United States); Theodore, N.D. [School of Materials, Arizona State University, Tempe, Arizona (United States); Wireless and Packaging Systems Laboratory, Freescale Semiconductor Inc., Tempe, Arizona (United States); Alford, T.L. [School of Materials, Arizona State University, Tempe, Arizona (United States)], E-mail: alford@asu.edu

    2008-09-01

    Tungsten-titanium thin films have been extensively applied as barrier layers for aluminum and copper metallization. The present work investigated the feasibility of tungsten-titanium barrier layers for silver metallization. Reactive sputtered W-Ti was deposited on a Si wafer followed by an Ag thin film on top. The resulting samples were annealed in vacuum at temperatures up to 700 deg. C. These were then characterized using X-ray diffractometry, Rutherford backscattering spectrometry, secondary ion mass spectroscopy, transmission electron microscopy, scanning electron microscopy and four point probe analysis. The analyses showed that the samples were stable up to 600 deg. C. Secondary ion mass spectroscopy showed that above 600 deg. C, agglomeration of silver film started. Si started moving into the tungsten-titanium film above 600 deg. C. Movement of Si resulted in local Si voiding as indicated by transmission electron microscopy. At Si/W-Ti interface, silicide formation occurred. Silver agglomerated completely at 700 deg. C. These results showed that W-Ti was an effective barrier layer for silver metallization for process temperatures below 600 deg. C.

  18. Evidence of a Symmetry-Dependent Metallic Barrier in Fully Epitaxial MgO Based Magnetic Tunnel Junctions

    Science.gov (United States)

    Greullet, F.; Tiusan, C.; Montaigne, F.; Hehn, M.; Halley, D.; Bengone, O.; Bowen, M.; Weber, W.

    2007-11-01

    We report on the experimental observation of tunneling across an ultrathin metallic Cr spacer layer that is inserted at the interface of a Fe/MgO/Fe(001) junction. We show how this remarkable behavior in a solid-state device reflects a quenching in the transmission of particular electronic states, as expected from the symmetry-filtering properties of the MgO barrier and the band structure of the bcc Cr(001) spacer in the epitaxial junction stack. This ultrathin Cr metallic barrier can promote quantum well states in an adjacent Fe layer.

  19. Potential barrier heights at metal on oxygen-terminated diamond interfaces

    Science.gov (United States)

    Muret, P.; Traoré, A.; Maréchal, A.; Eon, D.; Pernot, J.; Pinẽro, J. C.; Villar, M. P.; Araujo, D.

    2015-11-01

    Electrical properties of metal-semiconductor (M/SC) and metal/oxide/SC structures built with Zr or ZrO2 deposited on oxygen-terminated surfaces of (001)-oriented diamond films, comprised of a stack of lightly p-doped diamond on a heavily doped layer itself homoepitaxially grown on an Ib substrate, are investigated experimentally and compared to different models. In Schottky barrier diodes, the interfacial oxide layer evidenced by high resolution transmission electron microscopy and electron energy losses spectroscopy before and after annealing, and barrier height inhomogeneities accounts for the measured electrical characteristics until flat bands are reached, in accordance with a model which generalizes that by Tung [Phys. Rev. B 45, 13509 (1992)] and permits to extract physically meaningful parameters of the three kinds of interface: (a) unannealed ones, (b) annealed at 350 °C, (c) annealed at 450 °C with the characteristic barrier heights of 2.2-2.5 V in case (a) while as low as 0.96 V in case (c). Possible models of potential barriers for several metals deposited on well defined oxygen-terminated diamond surfaces are discussed and compared to experimental data. It is concluded that interface dipoles of several kinds present at these compound interfaces and their chemical evolution due to annealing are the suitable ingredients that are able to account for the Mott-Schottky behavior when the effect of the metal work function is ignored, and to justify the reverted slope observed regarding metal work function, in contrast to the trend always reported for all other metal-semiconductor interfaces.

  20. Potential barrier heights at metal on oxygen-terminated diamond interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Muret, P., E-mail: pierre.muret@neel.cnrs.fr; Traoré, A.; Maréchal, A.; Eon, D. [Inst. NEEL, Univ. Grenoble Alpes, F-38042 Grenoble, France and CNRS, Inst. NEEL, F-38042 Grenoble (France); Pernot, J. [Univ. Grenoble Alpes, Inst. NEEL, F-38042 Grenoble, (France); CNRS, Inst. NEEL, F-38042 Grenoble, (France); Institut Universitaire de France, 103 Boulevard Saint-Michel, F-75005 Paris (France); Pinero, J. C.; Villar, M. P.; Araujo, D., E-mail: daniel.araujo@uca.es [Dpto. Ciencias de los Materiales, Universidad de Cádiz, 11510 Puerto Real (Cádiz) (Spain)

    2015-11-28

    Electrical properties of metal-semiconductor (M/SC) and metal/oxide/SC structures built with Zr or ZrO{sub 2} deposited on oxygen-terminated surfaces of (001)-oriented diamond films, comprised of a stack of lightly p-doped diamond on a heavily doped layer itself homoepitaxially grown on an Ib substrate, are investigated experimentally and compared to different models. In Schottky barrier diodes, the interfacial oxide layer evidenced by high resolution transmission electron microscopy and electron energy losses spectroscopy before and after annealing, and barrier height inhomogeneities accounts for the measured electrical characteristics until flat bands are reached, in accordance with a model which generalizes that by Tung [Phys. Rev. B 45, 13509 (1992)] and permits to extract physically meaningful parameters of the three kinds of interface: (a) unannealed ones, (b) annealed at 350 °C, (c) annealed at 450 °C with the characteristic barrier heights of 2.2–2.5 V in case (a) while as low as 0.96 V in case (c). Possible models of potential barriers for several metals deposited on well defined oxygen-terminated diamond surfaces are discussed and compared to experimental data. It is concluded that interface dipoles of several kinds present at these compound interfaces and their chemical evolution due to annealing are the suitable ingredients that are able to account for the Mott-Schottky behavior when the effect of the metal work function is ignored, and to justify the reverted slope observed regarding metal work function, in contrast to the trend always reported for all other metal-semiconductor interfaces.

  1. Nonlinear optical properties of ultrathin metal layers

    DEFF Research Database (Denmark)

    Lysenko, Oleg

    2016-01-01

    . The optical characterization of the plasmonic waveguides is performed using femtosecond and picosecond optical pulses. Two nonlinear optical effects in the strip plasmonic waveguides are experimentally observed and reported. The first effect is the nonlinear power transmission of the plasmonic mode......-order nonlinear susceptibility of the plasmonic mode in the gold strip waveguides significantly depends on the metal layer thickness and laser pulse duration. This dependence is explained in detail in terms of the free-electron temporal dynamics in gold. The third-order nonlinear susceptibility of the gold layer...... duration dependence of the third-order nonlinear susceptibility of gold is calculated in the broad range from tens of femtoseconds to tens of picoseconds using the two-temperature model of the free-electron temporal dynamics of gold, and shows the saturation of the thirdorder nonlinear susceptibility...

  2. The interaction of acoustic waves with a three-layer barrier at different angles of incidence

    Science.gov (United States)

    Nikiforov, A. A.

    2017-01-01

    In this paper influence of the bubble layer on the transmission of the acoustic waves through the three-layer barrier placed in the water at various angles of incidence is investigated. Barrier consists of a layer of gel with polydispersed air bubbles limited polycarbonate layers. It is shown that the presence of bubbles in the layer substantially lowers the transmission of the acoustic waves through the multi-layer barrier for frequencies close to the resonant frequency of the bubbles. For these frequencies the values of the reflection and transmission coefficients are almost independent of the angle of incidence and determined by the parameters of the bubble gel.

  3. The electric double layer in hydriding metals

    Directory of Open Access Journals (Sweden)

    K. Jamroziak

    2008-12-01

    Full Text Available Purpose: The effect of penetration hydrogen into fatigue load metals is widely investigated by many researchers.Hydrogen is the chemical element which plays negative role in fatigue durability of structures. It decides on fatiguebrittle cracking. In the paper authors carry out an analysis of fatigue durability. Making use of naturally coming intoexistence the electric double layer phenomenon authors discussed the model of absorbing hydrogen into fatigue gap.Design/methodology/approach: A proposed model of the mechanism of hydrogen absorption by metal wasbased on particle hydrogen and water vapor from the air.Findings: It assumes that the EDL has crucial role in intercepting of polar dipole particles of hydrogenand water’s vapor, especially in an already formed fatigue micro-gaps and gaps by effects of its electrostaticattraction force. The authors assume that the main source of hydrogen is water’s vapor, and number of hydrogendipoles is negligible.Practical implications: The problems of metals’ fragility/durability were also discussed in other papersin which author mainly tried to develop new methods of materials’ production with the consideration of assumedfatigue durability.Originality/value: Currently, in progress are works on proposing a model for hydrogen absorption by metal.Such approach to optimization in production and development of the new technologies is an essence of modernconstructions that work in all variety of mechanical stress conditions.

  4. Polysulfide intercalated layered double hydroxides for metal capture applications

    Science.gov (United States)

    Kanatzidis, Mercouri G.; Ma, Shulan

    2017-04-04

    Polysulfide intercalated layered double hydroxides and methods for their use in vapor and liquid-phase metal capture applications are provided. The layered double hydroxides comprise a plurality of positively charged host layers of mixed metal hydroxides separated by interlayer spaces. Polysulfide anions are intercalated in the interlayer spaces.

  5. Polysulfide intercalated layered double hydroxides for metal capture applications

    Energy Technology Data Exchange (ETDEWEB)

    Kanatzidis, Mercouri G.; Ma, Shulan

    2017-04-04

    Polysulfide intercalated layered double hydroxides and methods for their use in vapor and liquid-phase metal capture applications are provided. The layered double hydroxides comprise a plurality of positively charged host layers of mixed metal hydroxides separated by interlayer spaces. Polysulfide anions are intercalated in the interlayer spaces.

  6. Effect of an Opaque Reflecting Layer on the Thermal Behavior of a Thermal Barrier Coating

    Science.gov (United States)

    Spuckler, Charles M.

    2007-01-01

    A parametric study using a two-flux approximation of the radiative transfer equation was performed to examine the effects of an opaque reflective layer on the thermal behavior of a typical semitransparent thermal barrier coating on an opaque substrate. Some ceramic materials are semitransparent in the wavelength ranges where thermal radiation is important. Even with an opaque layer on each side of the semitransparent thermal barrier coating, scattering and absorption can have an effect on the heat transfer. In this work, a thermal barrier coating that is semitransparent up to a wavelength of 5 micrometers is considered. Above 5 micrometers wavelength, the thermal barrier coating is opaque. The absorption and scattering coefficient of the thermal barrier was varied. The thermal behavior of the thermal barrier coating with an opaque reflective layer is compared to a thermal barrier coating without the reflective layer. For a thicker thermal barrier coating with lower convective loading, which would be typical of a combustor liner, a reflective layer can significantly decrease the temperature in the thermal barrier coating and substrate if the scattering is weak or moderate and for strong scattering if the absorption is large. The layer without the reflective coating can be about as effective as the layer with the reflective coating if the absorption is small and the scattering strong. For low absorption, some temperatures in the thermal barrier coating system can be slightly higher with the reflective layer. For a thin thermal barrier coating with high convective loading, which would be typical of a blade or vane that sees the hot sections of the combustor, the reflective layer is not as effective. The reflective layer reduces the surface temperature of the reflective layer for all conditions considered. For weak and moderate scattering, the temperature of the TBC-substrate interface is reduced but for strong scattering, the temperature of the substrate is increased

  7. Silver doped metal layers for medical applications

    Science.gov (United States)

    Kocourek, T.; Jelínek, M.; Mikšovský, J.; Jurek, K.; Weiserová, M.

    2014-04-01

    Biological, physical and mechanical properties of silver-doped layers of titanium alloy Ti6Al4V and 316L steel prepared by pulsed laser deposition were studied. Metallic silver-doped coatings could be a new route for antibacterial protection in medicine. Thin films of silver and silver-doped materials were synthesized using KrF excimer laser deposition. The materials were ablated from two targets, which were composed either from titanium alloy with silver segments or from steel with silver segments. The concentration of silver ranged from 1.54 at% to 4.32 at% for steel and from 3.04 at% to 13.05 at% for titanium alloy. The layer properties such as silver content, structure, adhesion, surface wettability, and antibacterial efficacy (evaluated by Escherichia coli and Bacillus subtilis bacteria) were measured. Film adhesion was studied using scratch test. The antibacterial efficacy changed with silver doping up to 99.9 %. Our investigation was focused on minimum Ag concentration needed to reach high antibacterial efficiency, high film adhesion, and hardness.

  8. Application of the photomodulated reflectance technique to the monitoring of metal layers

    Energy Technology Data Exchange (ETDEWEB)

    Dobos, Gabor; Lenk, Sandor; Ujhelyi, Ferenc; Szita, Zsofia; Kocsanyi, Laszlo [Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki ut 8, 1111 Budapest (Hungary); Somogyi, Andras [Semilab Corporation, Prielle Kornelia ut 2, 1117 Budapest (Hungary)

    2011-09-15

    Photomodulated reflectance (PMR) measurement techniques are currently used for the monitoring of ultra-shallow junctions. This paper discusses the possibility of applying them to the characterisation of metal layers. A finite element method based computer model has been created to study the dependence of the PMR signal on different sample parameters. We present the results of these simulations and show that the method can be used to establish the thickness of a metal layer (if the material is known) and it can also provide information about the metal/semiconductor interface. This information might be used to characterise the barrier seed layer beneath the metal, by a non-contact and non-destructive way. Simulation results are also supported by actual measurements on test samples. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Low-Temperature Plasma-Assisted Atomic Layer Deposition of Silicon Nitride Moisture Permeation Barrier Layers.

    Science.gov (United States)

    Andringa, Anne-Marije; Perrotta, Alberto; de Peuter, Koen; Knoops, Harm C M; Kessels, Wilhelmus M M; Creatore, Mariadriana

    2015-10-14

    Encapsulation of organic (opto-)electronic devices, such as organic light-emitting diodes (OLEDs), photovoltaic cells, and field-effect transistors, is required to minimize device degradation induced by moisture and oxygen ingress. SiNx moisture permeation barriers have been fabricated using a very recently developed low-temperature plasma-assisted atomic layer deposition (ALD) approach, consisting of half-reactions of the substrate with the precursor SiH2(NH(t)Bu)2 and with N2-fed plasma. The deposited films have been characterized in terms of their refractive index and chemical composition by spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR). The SiNx thin-film refractive index ranges from 1.80 to 1.90 for films deposited at 80 °C up to 200 °C, respectively, and the C, O, and H impurity levels decrease when the deposition temperature increases. The relative open porosity content of the layers has been studied by means of multisolvent ellipsometric porosimetry (EP), adopting three solvents with different kinetic diameters: water (∼0.3 nm), ethanol (∼0.4 nm), and toluene (∼0.6 nm). Irrespective of the deposition temperature, and hence the impurity content in the SiNx films, no uptake of any adsorptive has been observed, pointing to the absence of open pores larger than 0.3 nm in diameter. Instead, multilayer development has been observed, leading to type II isotherms that, according to the IUPAC classification, are characteristic of nonporous layers. The calcium test has been performed in a climate chamber at 20 °C and 50% relative humidity to determine the intrinsic water vapor transmission rate (WVTR) of SiNx barriers deposited at 120 °C. Intrinsic WVTR values in the range of 10(-6) g/m2/day indicate excellent barrier properties for ALD SiNx layers as thin as 10 nm, competing with that of state-of-the-art plasma-enhanced chemical vapor-deposited SiNx layers of a few hundred

  10. Seasonal variation of the barrier layer in the PN section

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yuan; WU Dexing; LIN Xiaopei; SHAN Feng

    2009-01-01

    In this paper, we use the conductivity-temperature-depth (CTD) observation data and a three-dimensional ocean model in a seasonally-varying forcing field to study the barrier layer (BL) in the PN section in the East China Sea (ECS). The BL can be found along the PN section with obviously seasonal variability. In winter, spring and autumn, the BL occurs around the slope where the cold shelf water meets with the warm Kuroshio water. In summer, the BL can also be found in the shelf area near salinity front of the Changjiang (Yangtze) River Dilution Water (YRDW). Seasonal variations of BL in the PN section are caused by local hydrological characteristics and seasonal variations of atmospheric forcing. Strong vertical convection caused by sea surface cooling thickens the BL in winter and spring in the slope area. Due to the large discharge of Changjiang River in summer, the BL occurs extensively in the shelf region where the fresh YRDW and the salty bottom water meet and form a strong halocline above the seasonal thermocline. The formation mechanism of BL in the PN section can be explained by the vertical shear of different water masses, which is called the advection mechanism. The interannual variation of BL in summer is greatly affected by the YRDW. In the larger YRDW year (such as 1998), a shallow but much thicker BL existed on the shelf area.

  11. Metal-semiconductor Schottky barrier junctions and their applications

    CERN Document Server

    1984-01-01

    The present-day semiconductor technology would be inconceivable without extensive use of Schottky barrier junctions. In spite of an excellent book by Professor E.H. Rhoderick (1978) dealing with the basic principles of metal­ semiconductor contacts and a few recent review articles, the need for a monograph on "Metal-Semiconductor Schottky Barrier Junctions and Their Applications" has long been felt by students, researchers, and technologists. It was in this context that the idea of publishing such a monograph by Mr. Ellis H. Rosenberg, Senior Editor, Plenum Publishing Corporation, was considered very timely. Due to the numerous and varied applications of Schottky barrier junctions, the task of bringing it out, however, looked difficult in the beginning. After discussions at various levels, it was deemed appropriate to include only those typical applications which were extremely rich in R&D and still posed many challenges so that it could be brought out in the stipulated time frame. Keeping in view the la...

  12. Tunable Staged Release of Therapeutics from Layer-by-Layer Coatings with Clay Interlayer Barrier

    Science.gov (United States)

    Min, Jouha; Braatz, Richard D.; Hammond, Paula T.

    2014-01-01

    In developing new generations of coatings for medical devices and tissue engineering scaffolds, there is a need for thin coatings that provide controlled sequential release of multiple therapeutics while providing a tunable approach to time dependence and the potential for sequential or staged release. Herein, we demonstrate the ability to develop a self-assembled, polymer-based conformal coating, built by using a water-based layer-by-layer (LbL) approach, as a dual-purpose biomimetic implant surface that provides staggered and/or sustained release of an antibiotic followed by active growth factor for orthopedic implant applications. This multilayered coating consists of two parts: a base osteoinductive component containing bone morphogenetic protein-2 (rhBMP-2) beneath an antibacterial component containing gentamicin (GS). For the fabrication of truly stratified composite films with the customized release behavior, we present a new strategy—implementation of laponite clay barriers—that allows for a physical separation of the two components by controlling interlayer diffusion. The clay barriers in a single-component GS system effectively block diffusion-based release, leading to approximately 50% reduction in bolus doses and 10-fold increase in the release timescale. In a dual-therapeutic composite coating, the top GS component itself was found to be an effective physical barrier for the underlying rhBMP-2, leading to an order of magnitude increase in the release timescale compared to the single-component rhBMP-2 system. The introduction of a laponite interlayer barrier further enhanced the temporal separation between release of the two drugs, resulting in a more physiologically appropriate dosing of rhBMP-2. Both therapeutics released from the composite coating retained their efficacy over their established release timeframes. This new platform for multi-drug localized delivery can be easily fabricated, tuned, and translated to a variety of implant

  13. Ultrathin, transferred layers of thermally grown silicon dioxide as biofluid barriers for biointegrated flexible electronic systems

    Science.gov (United States)

    Fang, Hui; Zhao, Jianing; Yu, Ki Jun; Song, Enming; Barati Farimani, Amir; Chiang, Chia-Han; Jin, Xin; Xue, Yeguang; Xu, Dong; Du, Wenbo; Seo, Kyung Jin; Zhong, Yiding; Yang, Zijian; Won, Sang Min; Fang, Guanhua; Choi, Seo Woo; Chaudhuri, Santanu; Huang, Yonggang; Ashraful Alam, Muhammad; Viventi, Jonathan; Aluru, N. R.; Rogers, John A.

    2016-10-01

    Materials that can serve as long-lived barriers to biofluids are essential to the development of any type of chronic electronic implant. Devices such as cardiac pacemakers and cochlear implants use bulk metal or ceramic packages as hermetic enclosures for the electronics. Emerging classes of flexible, biointegrated electronic systems demand similar levels of isolation from biofluids but with thin, compliant films that can simultaneously serve as biointerfaces for sensing and/or actuation while in contact with the soft, curved, and moving surfaces of target organs. This paper introduces a solution to this materials challenge that combines (i) ultrathin, pristine layers of silicon dioxide (SiO2) thermally grown on device-grade silicon wafers, and (ii) processing schemes that allow integration of these materials onto flexible electronic platforms. Accelerated lifetime tests suggest robust barrier characteristics on timescales that approach 70 y, in layers that are sufficiently thin (less than 1 μm) to avoid significant compromises in mechanical flexibility or in electrical interface fidelity. Detailed studies of temperature- and thickness-dependent electrical and physical properties reveal the key characteristics. Molecular simulations highlight essential aspects of the chemistry that governs interactions between the SiO2 and surrounding water. Examples of use with passive and active components in high-performance flexible electronic devices suggest broad utility in advanced chronic implants.

  14. Vacuum barrier for excimer lasers

    Energy Technology Data Exchange (ETDEWEB)

    Shurter, Roger P. (Jemez Springs, NM)

    1992-01-01

    A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput.

  15. Vacuum barrier for excimer lasers

    Energy Technology Data Exchange (ETDEWEB)

    Shurter, R.P.

    1992-09-15

    A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput. 3 figs.

  16. The barrier layer in the southern region of the South China Sea

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    By analysing the CTD data in the southernregion of the South China Sea gathered during six cruises between 1989 and 1999, a barrier layer with seasonal variation just like what exists in the equatorial oceans is found in this region. It is the first discovery in such a marginal sea yet.It is strong in autunm and a little weak in summer and winter. The thicker the barrier layer, the higher the average temperature of the upper mixed layer. The region with the thicker barrier layer overlaps the region with the higher average temperature of the upper mixed layer, and accords with the thicker region of the warm pool in the South China Sea got from the Levitus data. The barrier layer in the southern region of the South China Sea has significant influence on the heat storage of the upper ocean there.``

  17. The role of the spray pyrolysed Al2O3 barrier layer in achieving high efficiency solar cells on flexible steel substrates

    Science.gov (United States)

    Gledhill, Sophie E.; Zykov, Anton; Rissom, Thorsten; Caballero, Raquel; Kaufmann, Christian A.; Fischer, Christian-Herbert; Lux-Steiner, Martha; Efimova, Varvara; Hoffmann, Volker; Oswald, Steffen

    2011-07-01

    Thin film chalcopyrite solar cells grown on light-weight, flexible steel substrates are poised to enter the photovoltaic market. To guarantee good solar cell performance, the diffusion of iron from the steel into the CIGSe absorber material must be hindered during layer deposition. A barrier layer is thus required to isolate the solar module from the metal substrate, both electronically and chemically. Ideally the barrier layer would be deposited by a cheap roll-to-roll process suitable to coat flexible steel substrates. Aluminium oxide deposited by spray pyrolysis matches the criteria. The coating is homogeneous over rough substrates allowing comparatively thin barrier layers to be utilized. In this article, solar cell results are presented contrasting the device performance made with a barrier layer to that without a barrier layer. Secondary Ion Mass spectrometry (SIMS) measurements show that the spray pyrolysed barrier layer diminishes iron diffusion to the chalcopyrite absorber layer. The role of sodium, imperative for the growth of high efficiency chalcopyrite solar cells, and how it interacts with Al2O3 is discussed.

  18. The energy barrier at noble metal/TiO{sub 2} junctions

    Energy Technology Data Exchange (ETDEWEB)

    Hossein-Babaei, F., E-mail: fhbabaei@kntu.ac.ir, E-mail: fhbabaei@yahoo.com; Lajvardi, Mehdi M., E-mail: mm.lajvardi@gmail.com; Alaei-Sheini, Navid, E-mail: navid-alaei@yahoo.com [Electronic Materials Laboratory, Industrial Control Center of Excellence, Electrical Engineering Department, K. N. Toosi University of Technology, Tehran 16317-14191 (Iran, Islamic Republic of)

    2015-02-23

    Nobel metal/TiO{sub 2} structures are used as catalysts in chemical reactors, active components in TiO{sub 2}-based electronic devices, and connections between such devices and the outside circuitry. Here, we investigate the energy barrier at the junctions between vacuum-deposited Ag, Au, and Pt thin films and TiO{sub 2} layers by recording their electrical current vs. voltage diagrams and spectra of optical responses. Deposited Au/, Pt/, and Ag/TiO{sub 2} behave like contacts with zero junction energy barriers, but the thermal annealing of the reverse-biased devices for an hour at 523 K in air converts them to Schottky diodes with high junction energy barriers, decreasing their reverse electric currents up to 10{sup 6} times. Similar thermal processing in vacuum or pure argon proved ineffective. The highest energy barrier and the lowest reverse current among the devices examined belong to the annealed Ag/TiO{sub 2} contacts. The observed electronic features are described based on the physicochemical parameters of the constituting materials. The formation of higher junction barriers with rutile than with anatase is demonstrated.

  19. Plasma sprayed and electrospark deposited zirconium metal diffusion barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Hollis, Kendall J [Los Alamos National Laboratory; Pena, Maria I [Los Alamos National Laboratory

    2010-01-01

    Zirconium metal coatings applied by plasma spraying and electrospark deposition (ESD) have been investigated for use as diffusion barrier coatings on low enrichment uranium fuel for research nuclear reactors. The coatings have been applied to both stainless steel as a surrogate and to simulated nuclear fuel uranium-molybdenum alloy substrates. Deposition parameter development accompanied by coating characterization has been performed. The structure of the plasma sprayed coating was shown to vary with transferred arc current during deposition. The structure of ESD coatings was shown to vary with the capacitance of the deposition equipment.

  20. Resin infusion of layered metal/composite hybrid and resulting metal/composite hybrid laminate

    Science.gov (United States)

    Cano, Roberto J. (Inventor); Grimsley, Brian W. (Inventor); Weiser, Erik S. (Inventor); Jensen, Brian J. (Inventor)

    2009-01-01

    A method of fabricating a metal/composite hybrid laminate is provided. One or more layered arrangements are stacked on a solid base to form a layered structure. Each layered arrangement is defined by a fibrous material and a perforated metal sheet. A resin in its liquid state is introduced along a portion of the layered structure while a differential pressure is applied across the laminate structure until the resin permeates the fibrous material of each layered arrangement and fills perforations in each perforated metal sheet. The resin is cured thereby yielding a metal/composite hybrid laminate.

  1. Observations of barrier layer formation in the Bay of Bengal during summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Vinayachandran, P.N.; Murty, V.S.N.; RameshBabu, V.

    of a new halocline and hence a barrier layer within the upper 30 m of the water column. The ensuing ocean-atmosphere interaction was restricted to the new thinner mixed layer. The cooling that was restricted to the mixed layer led to an inversion...

  2. Inter-Layer Energy Transfer through Wetting-Layer States in Bi-layer InGaAs/GaAs Quantum-Dot Structures with Thick Barriers

    DEFF Research Database (Denmark)

    Xu, Zhang-Cheng; Zhang, Ya-Ting; Hvam, Jørn Märcher

    2009-01-01

    The inter-layer energy transfer in a bi-layer InGaAs/GaAs quantum dot structure with a thick GaAs barrier is studied using temperature-dependent photoluminescence. The abnormal enhancement of the photoluminescence of the QDs in the layer with a larger amount of coverage at 110K is observed, which...

  3. Effects of sputtering power Schottky metal layers on rectifying performance of Mo-SiC Schottky contacts

    Science.gov (United States)

    Lee, Seula; Lee, Jinseon; You, Sslimsearom; Kyoung, Sinsu; Kim, Kyung Hwan

    2016-01-01

    In this study, Schottky barrier diodes based on silicon carbide with various levels of Schottky metal layer input power were prepared and characterized. In this structure, molybdenum and aluminum were employed as the Schottky metal and top electrode, respectively. Schottky metal layers were deposited with input power ranging from 30 to 210 W. Schottky metal layers and top electrodes were deposited with a thickness of 3000 Å. The Schottky barrier heights, series resistances, and ideality factor were calculated from current-voltage (I-V) curves obtained using the Cheung-Cheung and Norde methods. All deposition processes were conducted using a facing targets sputtering system. Turn on voltage was minimized when the input power was 90 W, at which point electrical characteristics were observed to have properties superior to those at other levels of input power.

  4. Analysis of Ta-based Barrier Layer of Cu-interconnect by Second Ion Mass Spectrometry%Cu互连工艺中Ta基扩散阻挡层的二次离子质谱剖析

    Institute of Scientific and Technical Information of China (English)

    曹永明; 方培源; 姜蕾

    2004-01-01

    With the development of deep submicron integrated circuits (IC), copper metallization has been a replacement for conventional aluminum metallization in high density IC manufacture. But Cu is quite mobile in Si and has poor adhesion to Si or SiO2, which could degrade the performance of copper interconnect. Therefore, a diffusion barrier layer between copper interconnect and Si device is necessary. In this paper, Ta-based barrier layers are deposited on Si substrate with deposition technology of magnetron sputtering. The depth profile of copper interconnect and Ta-diffusion barrier layer are investigated by second ion mass spectrometry(SIMS).

  5. Diffusion barrier and adhesion properties of SiO(x)N(y) and SiO(x) layers between Ag/polypyrrole composites and Si substrates.

    Science.gov (United States)

    Horváth, Barbara; Kawakita, Jin; Chikyow, Toyohiro

    2014-06-25

    This paper describes the interface reactions and diffusion between silver/polypyrrole (Ag/PPy) composite and silicon substrate. This composite material can be used as a novel technique for 3D-LSI (large-scale integration) by the fast infilling of through-silicon vias (TSV). By immersion of the silicon wafer with via holes into the dispersed solution of Ag/PPy composite, the holes are filled with the composite. It is important to develop a layer between the composite and the Si substrate with good diffusion barrier and adhesion characteristics. In this paper, SiOx and two types of SiOxNy barrier layers with various thicknesses were investigated. The interface structure between the Si substrate, the barrier, and the Ag/PPy composite was characterized by transmission electron microscopy. The adhesion and diffusion properties of the layers were established for Ag/PPy composite. Increasing thickness of SiOx proved to permit less Ag to transport into the Si substrate. SiOxNy barrier layers showed very good diffusion barrier characteristics; however, their adhesion depended strongly on their composition. A barrier layer composition with good adhesion and Ag barrier properties has been identified in this paper. These results are useful for filling conductive metal/polymer composites into TSV.

  6. Electrical properties of graphene tunnel junctions with high-κ metal-oxide barriers

    Science.gov (United States)

    Feng, Ying; Trainer, Daniel J.; Chen, Ke

    2017-04-01

    An insulating barrier is one of the key components in electronic devices that makes use of quantum tunneling principles. Many metal-oxides have been used as a good barrier material in a tunnel junction for their large band gap, stable chemical properties and superb properties for forming a thin and pin-hole-free insulating layer. The reduced dimensions of transistors have led to the need for alternative, high dielectric constant (high-κ) oxides to replace conventional silicon-based dielectrics to reduce the leaking current induced by electron tunneling. On the other hand, a tunnel junction with one or both electrodes made of graphene may lead to novel applications due to the massless Dirac fermions from the graphene. Here we have fabricated sandwich-type graphene tunnel junctions with high-κ metal-oxides as barriers, including Al2O3, HfO2, ZrO2, and TiO2. Tunneling properties are investigated by observing the temperature and time dependences of the tunneling spectra. Our results show the potential for applications of high-κ oxides in graphene tunnel junctions and bringing new opportunities for memory and logic electronic devices.

  7. Theory of Metallic Work Functions Between Metals and Layers of Exclusion Zone Ordered Water

    CERN Document Server

    Widom, A; Srivastava, Y N

    2016-01-01

    The magnitude of the work function to bring an electron from a metal into the exclusion zone water layer making hydrophilic contact with the metallic interface is theoretically computed. The agreement with recent experimental measurements is satisfactory.

  8. Anomalous electron transport in metal/carbon multijunction devices by engineering of the carbon thickness and selecting metal layer

    Science.gov (United States)

    Dwivedi, Neeraj; Dhand, Chetna; Rawal, Ishpal; Kumar, Sushil; Malik, Hitendra K.; Lakshminarayanan, Rajamani

    2017-06-01

    A longstanding concern in the research of amorphous carbon films is their poor electrical conductivity at room temperature which constitutes a major barrier for the development of cost effective electronic and optoelectronic devices. Here, we propose metal/carbon hybrid multijunction devices as a promising facile way to overcome room temperature electron transport issues in amorphous carbon films. By the tuning of carbon thickness and swapping metal layers, we observe giant (upto ˜7 orders) reduction of electrical resistance in metal/carbon multijunction devices with respect to monolithic amorphous carbon device. We engineer the maximum current (electrical resistance) from about 10-7 to 10-3 A (˜107 to 103 Ω) in metal (Cu or Ti)/carbon hybrid multijunction devices with a total number of 10 junctions. The introduction of thin metal layers breaks the continuity of relatively higher resistance carbon layer as well as promotes the nanostructuring of carbon. These contribute to low electrical resistance of metal/carbon hybrid multijunction devices, with respect to monolithic carbon device, which is further reduced by decreasing the thickness of carbon layers. We also propose and discuss equivalent circuit model to explain electrical resistance in monolithic carbon and metal/carbon multijunction devices. Cu/carbon multijunction devices display relatively better electrical transport than Ti/carbon devices owing to low affinity of Cu with carbon that restricts carbide formation. We also observe that in metal/carbon multijunction devices, the transport mechanism changes from Poole-Frenkel/Schottky model to the hopping model with a decrease in carbon thickness. Our approach opens a new route to develop carbon-based inexpensive electronic and optoelectronic devices.

  9. Silicon based substrate with calcium aluminosilicate environmental/thermal barrier layer

    Science.gov (United States)

    Eaton, Jr., Harry Edwin (Inventor); Allen, William Patrick (Inventor); Miller, Robert Alden (Inventor); Jacobson, Nathan S. (Inventor); Smialek, James L. (Inventor); Opila, Elizabeth J. (Inventor); Lee, Kang N. (Inventor); Nagaraj, Bangalore A. (Inventor); Wang, Hongyu (Inventor); Meschter, Peter Joel (Inventor)

    2001-01-01

    A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a calcium alumino silicate.

  10. Functional barrier in two-layer recycled PP films for food packaging applications

    Science.gov (United States)

    Scarfato, P.; Di Maio, L.; Milana, M. R.; Feliciani, R.; Denaro, M.; Incarnato, L.

    2014-05-01

    A preliminary study on bi-layer virgin/contaminated polypropylene co-extruded films was performed in order to evaluate the possibility to realize an effective functional barrier in PP-based multi-layer systems. In particular, the specific migration in 10% v/v aqueous ethanol of two surrogate contaminants (phenyl-cyclohexane and benzophenone) contained in the contaminated layer across the PP functional barrier was measured at different times and the results were compared with those obtained from a contaminated mono-layer polypropylene film. Moreover, the thermal and mechanical performances of the produced films were investigated.

  11. Glomerular endothelial surface layer acts as a barrier against albumin filtration

    NARCIS (Netherlands)

    Dane, M.J.; Berg, B.M. van den; Avramut, M.C.; Faas, F.G.; Vlag, J. van der; Rops, A.L.; Ravelli, R.B.; Koster, B.J.; Zonneveld, A.J. van; Vink, H.; Rabelink, T.J.

    2013-01-01

    Glomerular endothelium is highly fenestrated, and its contribution to glomerular barrier function is the subject of debate. In recent years, a polysaccharide-rich endothelial surface layer (ESL) has been postulated to act as a filtration barrier for large molecules, such as albumin. To test this hyp

  12. Effect of W addition on the electroless deposited NiP(W) barrier layer

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Yishi [State Key Laboratory of Metal Matrix Composites, Key Laboratory for Thin Film and Microfabrication Technology of the Ministry of Education, School of Material Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai (China); Hu, Anmin, E-mail: huanmin@sjtu.edu.cn [State Key Laboratory of Metal Matrix Composites, Key Laboratory for Thin Film and Microfabrication Technology of the Ministry of Education, School of Material Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai (China); Hang, Tao [State Key Laboratory of Metal Matrix Composites, Key Laboratory for Thin Film and Microfabrication Technology of the Ministry of Education, School of Material Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai (China); Peng, Li [Shanghai Entry-Exit Inspection and Quarantine Bureau (China); Li, Ming [State Key Laboratory of Metal Matrix Composites, Key Laboratory for Thin Film and Microfabrication Technology of the Ministry of Education, School of Material Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai (China)

    2013-10-01

    Electroless deposition of NiP, NiWP thin film on p-type Si as the barrier layer to prevent the diffusion of Cu into Si was investigated. The thermal stability of the Si/Ni(W)P/Cu layers were evaluated by measuring the changes of resistance of the samples after annealed at various temperatures. XRD was applied to detect the formation of Cu{sub 3}Si and evaluate the barrier performance of the layers. The results of XRD of the stacked Si/NiP/Cu, Si/NiWP-1/Cu, Si/NiWP–2/Cu films reveal that Cu atom could diffuse through NiP barrier layer at 450 °C, Cu could hardly diffuse through NiWP layer at 550 °C. This means that with W added in the layer, the barrier performance is improved. Although the resistance of Si/NiWP-1 and Si/NiWP-2 are higher than that of Si/NiP, the resistance of stacked layers of Si/NiWP-1/Cu and Si/NiWP–2/Cu are close to that of Si/NiP/Cu. This means that using NiWP as barrier layer is acceptable.

  13. Barrier inhomogeneities and interface states of metal/4H-SiC Schottky contacts

    Science.gov (United States)

    Huang, Lingqin; Geiod, Rechard; Wang, Dejun

    2016-12-01

    The barrier and interface states of Ti, Mo, Ni, and Pt contacts to 4H-SiC were investigated. It is found that the barrier heights for all the contacts are Gaussianly distributed and the barrier inhomogeneity varies with the contact metal type. However, the energy-averaged interface states density in the band gap is metal-insensitive. When considering Gaussian distribution, the interface states density extracted from the electrical properties is consistent with the average density of Gaussianly distributed 4H-SiC surface states, indicating that the barrier inhomogeneities at metal/SiC contacts mainly originate from the spatial variation of surface states on SiC surface. The barrier height and barrier inhomogeneity could be modulated by the contact metal, obeying the barrier height theory of Cowley and Sze.

  14. Inter-Layer Energy Transfer through Wetting-Layer States in Bi-layer InGaAs/GaAs Quantum-Dot Structures with Thick Barriers

    Institute of Scientific and Technical Information of China (English)

    XU Zhang-Cheng; ZHANG Ya-Ting; J(φ)rn M. Hvam; Yoshiji Horikoshi

    2009-01-01

    The inter-layer energy transfer in a bi-layer InGaAs/GaAs quantum dot structure with a thick GaAs barrier is studied using temperature-dependent photoluminescence. The abnormal enhancement of the photoluminescence of the QDs in the layer with a larger amount of coverage at 110K is observed, which can be explained by considering the resonant F(o)rster energy transfer between the wetting layer states at elevated temperatures.

  15. The effect of the ferromagnetic metal layer on tunnelling conductance and magnetoresistance in double magnetic planar junctions

    Institute of Scientific and Technical Information of China (English)

    谢征微; 李伯臧; 李玉现

    2002-01-01

    Based on the free-electron approximation, we investigate the effect of the ferromagnetic metal layer on the tunnelling magnetoresistance (TMR) and tunnelling conductance (TC) in the double magnetic tunnel junctions (DMTJs)of the structure NM/FM/Ⅰ(S)/NM/Ⅰ(S)/FM/NM, where FM, NM and Ⅰ(S) represent the ferromagnetic metal, nonmagnetic metal and insulator (semiconductor), respectively. The FM, Ⅰ(S) and inner NM layers are of finite thickness,while the thickness of the outer NM layer is infinite. The calculated results show that, due to the spin-dependent interfacial potential barriers caused by electronic band mismatch between the various magnetic and nonmagnetic layers,the dependences of the TMR and TC on the thicknesses of the FM layers exhibit oscillations, and a much higher TMR can be obtained for suitable thicknesses of FM layers.

  16. Recombination barrier layers in solid-state quantum dot-sensitized solar cells

    KAUST Repository

    Roelofs, Katherine E.

    2012-06-01

    By replacing the dye in the dye-sensitized solar cell design with semiconductor quantum dots as the light-absorbing material, solid-state quantum dot-sensitized solar cells (ss-QDSSCs) were fabricated. Cadmium sulfide quantum dots (QDs) were grown in situ by successive ion layer adsorption and reaction (SILAR). Aluminum oxide recombination barrier layers were deposited by atomic layer deposition (ALD) at the TiO2/hole-conductor interface. For low numbers of ALD cycles, the Al2O3 barrier layer increased open circuit voltage, causing an increase in device efficiency. For thicker Al2O3 barrier layers, photocurrent decreased substantially, leading to a decrease in device efficiency. © 2012 IEEE.

  17. Theoretical investigation of silicide Schottky barrier detector integrated in horizontal metal-insulator-silicon-insulator-metal nanoplasmonic slot waveguide.

    Science.gov (United States)

    Zhu, Shiyang; Lo, G Q; Kwong, D L

    2011-08-15

    An ultracompact integrated silicide Schottky barrier detector (SBD) is designed and theoretically investigated to electrically detect the surface plasmon polariton (SPP) propagating along horizontal metal-insulator-silicon-insulator-metal nanoplasmonic slot waveguides at the telecommunication wavelength of 1550 nm. An ultrathin silicide layer inserted between the silicon core and the insulator, which can be fabricated precisely using the well-developed self-aligned silicide process, absorbs the SPP power effectively if a suitable silicide is chosen. Moreover, the Schottky barrier height in the silicide-silicon-silicide configuration can be tuned substantially by the external voltage through the Schottky effect owing to the very narrow silicon core. For a TaSi(2) detector with optimized dimensions, numerical simulation predicts responsivity of ~0.07 A/W, speed of ~60 GHz, dark current of ~66 nA at room temperature, and minimum detectable power of ~-29 dBm. The design also suggests that the device's size can be reduced and the overall performances will be further improved if a silicide with smaller permittivity is used.

  18. The modulation of Schottky barriers of metal-MoS2 contacts via BN-MoS2 heterostructures.

    Science.gov (United States)

    Su, Jie; Feng, Liping; Zhang, Yan; Liu, Zhengtang

    2016-06-22

    Using first-principles calculations within density functional theory, we systematically studied the effect of BN-MoS2 heterostructure on the Schottky barriers of metal-MoS2 contacts. Two types of FETs are designed according to the area of the BN-MoS2 heterostructure. Results show that the vertical and lateral Schottky barriers in all the studied contacts, irrespective of the work function of the metal, are significantly reduced or even vanish when the BN-MoS2 heterostructure substitutes the monolayer MoS2. Only the n-type lateral Schottky barrier of Au/BN-MoS2 contact relates to the area of the BN-MoS2 heterostructure. Notably, the Pt-MoS2 contact with n-type character is transformed into a p-type contact upon substituting the monolayer MoS2 by a BN-MoS2 heterostructure. These changes of the contact natures are ascribed to the variation of Fermi level pinning, work function and charge distribution. Analysis demonstrates that the Fermi level pinning effects are significantly weakened for metal/BN-MoS2 contacts because no gap states dominated by MoS2 are formed, in contrast to those of metal-MoS2 contacts. Although additional BN layers reduce the interlayer interaction and the work function of the metal, the Schottky barriers of metal/BN-MoS2 contacts still do not obey the Schottky-Mott rule. Moreover, different from metal-MoS2 contacts, the charges transfer from electrodes to the monolayer MoS2, resulting in an increment of the work function of these metals in metal/BN-MoS2 contacts. These findings may prove to be instrumental in the future design of new MoS2-based FETs with ohmic contact or p-type character.

  19. Deposited Micro Porous Layer as Lubricant Carrier in Metal Forming

    DEFF Research Database (Denmark)

    Arentoft, Mogens; Bay, Niels; Tang, Peter Torben

    2008-01-01

    A new porous coating for carrying lubricant in metal forming processes is developed. The coating is established by simultaneous electrochemical deposition of two pure metals. One of them is subsequently etched away leaving a porous surface layer. Lubricant can be trapped in the pores acting as lu...

  20. Energy dissipation in intercalated carbon nanotube forests with metal layers

    Science.gov (United States)

    Vertically aligned carbon nanotube (CNT) forests were synthesized to study their quasi-static mechanical properties in a layered configuration with metallization. The top and bottom surfaces of CNT forests were metalized with Ag, Fe, and In using paste, sputtering, and thermal evaporation, respectiv...

  1. Alloyed 2D Metal-Semiconductor Heterojunctions: Origin of Interface States Reduction and Schottky Barrier Lowering.

    Science.gov (United States)

    Kim, Yonghun; Kim, Ah Ra; Yang, Jin Ho; Chang, Kyoung Eun; Kwon, Jung-Dae; Choi, Sun Young; Park, Jucheol; Lee, Kang Eun; Kim, Dong-Ho; Choi, Sung Mook; Lee, Kyu Hwan; Lee, Byoung Hun; Hahm, Myung Gwan; Cho, Byungjin

    2016-09-14

    The long-term stability and superior device reliability through the use of delicately designed metal contacts with two-dimensional (2D) atomic-scale semiconductors are considered one of the critical issues related to practical 2D-based electronic components. Here, we investigate the origin of the improved contact properties of alloyed 2D metal-semiconductor heterojunctions. 2D WSe2-based transistors with mixed transition layers containing van der Waals (M-vdW, NbSe2/WxNb1-xSe2/WSe2) junctions realize atomically sharp interfaces, exhibiting long hot-carrier lifetimes of approximately 75,296 s (78 times longer than that of metal-semiconductor, Pd/WSe2 junctions). Such dramatic lifetime enhancement in M-vdW-junctioned devices is attributed to the synergistic effects arising from the significant reduction in the number of defects and the Schottky barrier lowering at the interface. Formation of a controllable mixed-composition alloyed layer on the 2D active channel would be a breakthrough approach to maximize the electrical reliability of 2D nanomaterial-based electronic applications.

  2. Thermally induced decomposition of B4C barrier layers in Mo/Si multilayer structures

    NARCIS (Netherlands)

    Bruijn, S.; van de Kruijs, R. W. E.; Yakshin, A. E.; Zoethout, E.; F. Bijkerk,

    2010-01-01

    We investigate the influence of the Mo crystalline state (quasi-amorphous or crystalline) on the thermal stability of Mo/Si thin film multilayers with B4C diffusion barrier layers at either of the two interfaces. We find that multilayers containing amorphous Mo layers are more stable than those cont

  3. Damping behaviors of metal matrix composites with interface layer

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A novel technique of designing the interface layer in metal matrix composites of high damping capacity was developed via different CVD coatings on carbon fibers in Cf/Al composites. It was shown that the interface layer improved the tensile strength, elastic modulus and damping capacity of the Cf/Al composites. A carbon layer showed the highest improvement and a silicon layer the lowest, while a mixed carbon and silicon layer exhibited an intermediate effect. Moreover, the thickness of interface layer also influences the damping capacity. A thicker carbon layer produced a better damping capacity because the dependence of damping capacity on strain amplitude was increased. It is suggested that a micro-sliding action occurring in the interface layer is the main mechanism responsible for the high damping capacity of the composites.

  4. Valence-band offsets and Schottky barrier heights of layered semiconductors explained by interface-induced gap states

    Science.gov (United States)

    Mönch, Winfried

    1998-04-01

    Many metal chalcogenides are layered semiconductors. They consist of chalcogen-metal-chalcogen layers that are themselves bound by van der Waals forces. Hence, heterostructures involving layered compounds are abrupt and strain-free. Experimental valence-band offsets of heterostructures between GaSe, InSe, SnS2, SnSe2, MoS2, MoTe2, WSe2, and CuInSe2 and between some of these compounds and ZnSe, CdS, and CdTe as well as barrier heights of Au contacts on GaSe, InSe, MoS2, MoTe2, WSe2, ZnSe, CdS, and CdTe are analyzed. The valence-band discontinuities of the heterostructures and the barrier heights of the Schottky contact compounds are consistently described by the continuum of interface-induced gap states as the primary mechanism that governs the band lineup at semiconductor interfaces.

  5. Ternary metal-rich sulfide with a layered structure

    Science.gov (United States)

    Franzen, Hugo F.; Yao, Xiaoqiang

    1993-08-17

    A ternary Nb-Ta-S compound is provided having the atomic formula, Nb.sub.1.72 Ta.sub.3.28 S.sub.2, and exhibiting a layered structure in the sequence S-M3-M2-M1-M2-M3-S wherein S represents sulfur layers and M1, M2, and M3 represent Nb/Ta mixed metal layers. This sequence generates seven sheets stacked along the [001] direction of an approximate body centered cubic crystal structure with relatively weak sulfur-to-sulfur van der Waals type interactions between adjacent sulfur sheets and metal-to-metal bonding within and between adjacent mixed metal sheets.

  6. Specific features of waveguide recombination in laser structures with asymmetric barrier layers

    DEFF Research Database (Denmark)

    Polubavkina, Yu; Zubov, F. I.; Moiseev, E.

    2017-01-01

    The spatial distribution of the intensity of the emission caused by recombination appearing at a high injection level (up to 30 kA/cm2) in the waveguide layer of a GaAs/AlGaAs laser structure with GaInP and AlGaInAs asymmetric barrier layers is studied by means of near-field scanning optical...... microscopy. It is found that the waveguide luminescence in such a laser, which is on the whole less intense as compared to that observed in a similar laser without asymmetric barriers, is non-uniformly distributed in the waveguide, so that the distribution maximum is shifted closer to the p-type cladding...... layer. This can be attributed to the ability of the GaInP barrier adjoining the quantum well on the side of the n-type cladding layer to suppress the hole transport....

  7. Energy dissipation in intercalated carbon nanotube forests with metal layers

    Science.gov (United States)

    Boddu, Veera M.; Brenner, Matthew W.

    2016-02-01

    Vertically aligned carbon nanotube (CNT) forests were synthesized to study their quasi-static mechanical properties in a layered configuration with metallization. The top and bottom surfaces of CNT forests were metalized with Ag, Fe, and In using paste, sputtering, and thermal evaporation, respectively. Stacks of one, two, and three layers of these forests were assembled and compressed to measure their mechanical properties. The samples were strain limited to 0.7, and the results indicate that energy dissipation is approximately linear with respect to the number of layers and relatively independent of metal type. The energy per unit volume was approximately the same for all samples. Successive stacking of CNT forests reduces local buckling events, which is enhanced with a thick Ag deposition on the CNT forest surface. Young's modulus was also observed to increase as the number of layers was increased. These results are useful in the design of composite materials for high energy absorption and high stiffness applications.

  8. Improved adhesion of metal oxide layer

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention relates to: a method of preparing a coating ink for forming a zinc oxide layer, which method comprises the steps of: a) mixing zinc acetate and AlOH (OAc)2 in water or methanol and b) filtering out solids; a coating ink comprising zinc acetate and AlOH (OAc)2 in aqueous...... or methanolic solution; a method of preparing a layer comprising zinc oxide, which method comprises: i) coating a substrate with the coating ink of the invention to form a film, ii) drying the film, and iii) heating the dry film to convert the zinc acetate substantially to ZnO; and a method of preparing...

  9. Prospects of zero Schottky barrier height in a graphene-inserted MoS{sub 2}-metal interface

    Energy Technology Data Exchange (ETDEWEB)

    Chanana, Anuja; Mahapatra, Santanu [Nano-Scale Device Research Laboratory, Department of Electronic Systems Engineering, Indian Institute of Science (IISc) Bangalore, Bangalore 560012 (India)

    2016-01-07

    A low Schottky barrier height (SBH) at source/drain contact is essential for achieving high drive current in atomic layer MoS{sub 2}-channel-based field effect transistors. Approaches such as choosing metals with appropriate work functions and chemical doping are employed previously to improve the carrier injection from the contact electrodes to the channel and to mitigate the SBH between the MoS{sub 2} and metal. Recent experiments demonstrate significant SBH reduction when graphene layer is inserted between metal slab (Ti and Ni) and MoS{sub 2}. However, the physical or chemical origin of this phenomenon is not yet clearly understood. In this work, density functional theory simulations are performed, employing pseudopotentials with very high basis sets to get insights of the charge transfer between metal and monolayer MoS{sub 2} through the inserted graphene layer. Our atomistic simulations on 16 different interfaces involving five different metals (Ti, Ag, Ru, Au, and Pt) reveal that (i) such a decrease in SBH is not consistent among various metals, rather an increase in SBH is observed in case of Au and Pt; (ii) unlike MoS{sub 2}-metal interface, the projected dispersion of MoS{sub 2} remains preserved in any MoS{sub 2}-graphene-metal system with shift in the bands on the energy axis. (iii) A proper choice of metal (e.g., Ru) may exhibit ohmic nature in a graphene-inserted MoS{sub 2}-metal contact. These understandings would provide a direction in developing high-performance transistors involving heteroatomic layers as contact electrodes.

  10. Fabrication of metal organic framework materials using a layer-by-layer spin coating approach

    KAUST Repository

    Eddaoudi, Mohamed

    2016-03-17

    Embodiments describe a method of depositing an MOF, including depositing a metal solution onto a substrate, spinning the substrate sufficient to spread the metal solution, depositing an organic ligand solution onto the substrate and spinning the substrate sufficient to spread the organic ligand solution and form a MOF layer.

  11. Thick growing multilayer nanobrick wall thin films: super gas barrier with very few layers.

    Science.gov (United States)

    Guin, Tyler; Krecker, Michelle; Hagen, David Austin; Grunlan, Jaime C

    2014-06-24

    Recent work with multilayer nanocoatings composed of polyelectrolytes and clay has demonstrated the ability to prepare super gas barrier layers from water that rival inorganic CVD-based films (e.g., SiOx). In an effort to reduce the number of layers required to achieve a very low oxygen transmission rate (OTR (layer-by-layer (LbL) assembly. Buffering the chitosan solution and its rinse with 50 mM Trizma base increased the thickness of these films by an order of magnitude. The OTR of a 1.6-μm-thick, six-bilayer film was 0.009 cc/m(2)·day·atm, making this the best gas barrier reported for such a small number of layers. This simple modification to the LbL process could likely be applied more universally to produce films with the desired properties much more quickly.

  12. A high performance ceria based interdiffusion barrier layer prepared by spin-coating

    DEFF Research Database (Denmark)

    Plonczak, Pawel; Joost, Mario; Hjelm, Johan

    2011-01-01

    A multiple spin-coating deposition procedure of Ce0.9Gd0.1O1.95 (CGO) for application in solid oxide fuel cells (SOFCs) was developed. The thin and dense CGO layer can be employed as a barrier layer between yttria stabilised zirconia (YSZ) electrolyte and a (La, Sr)(Co, Fe)O3 based cathode....... The decomposition of the polymer precursor used in the spin-coating process was studied. The depositions were performed on anode supported half cells. By controlling the sintering temperature between each spin-coating process, dense and crack-free CGO films with a thickness of approximately 1 μm were obtained....... The successive steps of dense layer production was investigated by scanning electron microscopy. X-ray diffraction was employed to monitor the crystal structure of the CGO layer sintered at different temperatures. The described spin coated barrier layer was evaluated using an anode supported cell...

  13. Design, installation, and performance of a multi-layered permeable reactive barrier, Los Alamos National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Kaszuba, J. P. (John P.); Longmire, P. A. (Patrick A.); Strietelmeier, E. A. (Elizabeth A.); Taylor, T. P. (Tammy P.); Den-Baars, P. S. (Peter S.)

    2004-01-01

    A multi-layered permeable reactive barrier (PRB) has been installed in Mortandad Canyon, on the Pajarito Plateau in the north-central part of LANL, to demonstrate in-situ treatment of a suite of contaminants with dissimilar geochemical properties. The PRB will also mitigate possible vulnerabilities from downgradient contaminant movement within alluvial and deeper perched groundwater. Mortandad Canyon was selected as the location for this demonstration project because the flow of alluvial groundwater is constrained by the geology of the canyon, a large network of monitoring wells already were installed along the canyon reach, and the hydrochemistry and contaminant history of the canyon is well-documented. The PRB uses a funnel-and-gate system with a series of four reactive media cells to immobilize or destroy contaminants present in alluvial groundwater, including strontium-90, plutonium-238,239,240, americium-241, perchlorate, and nitrate. The four cells, ordered by sequence of contact with the groundwater, consist of gravel-sized scoria (for colloid removal); phosphate rock containing apatite (for metals and radionuclides); pecan shells and cotton seed admixed with gravel (bio-barrier, to deplete dissolved oxygen and destroy potential RCRA organic compounds, nitrate and perchlorate); and limestone (pH buffering and anion adsorption). Design elements of the PRB are based on laboratory-scale treatability studies and on a field investigation of hydrologic, geochemical, and geotechnical parameters. The PRB was designed with the following criteria: 1-day residence time within the biobarrier, 10-year lifetime, minimization of surface water infiltration and erosion, optimization of hydraulic capture, and minimization of excavated material requiring disposal. Each layer has been equipped with monitoring wells or ports to allow sampling of groundwater and reactive media, and monitor wells are located immediately adjacent to the up- and down-gradient perimeter of the

  14. Effect of layered manufacturing techniques, alloy powders, and layer thickness on metal-ceramic bond strength.

    Science.gov (United States)

    Ekren, Orhun; Ozkomur, Ahmet; Ucar, Yurdanur

    2017-07-06

    Direct metal laser sintering (DMLS) and direct metal laser melting (DMLM) have become popular for fabricating the metal frameworks of metal-ceramic restorations. How the type of layered manufacturing device, layer thickness, and alloy powder may affect the bond strength of ceramic to metal substructure is unclear. The purpose of this in vitro study was to evaluate the bond strength of dental porcelain to metal frameworks fabricated using different layered manufacturing techniques (DMLS and DMLM), Co-Cr alloy powders, and layer thicknesses and to evaluate whether a correlation exists between the bond strength and the number of ceramic remnants on the metal surface. A total of 75 bar-shaped metal specimens (n=15) were fabricated using either DMLS or DMLM. The powder alloys used were Keramit NP-S and EOS-Cobalt-Chrome SP-2 with layer thicknesses of 20 μm and 30 μm. After ceramic application, the metal-ceramic bond strength was evaluated with a 3-point-bend test. Three-way ANOVA followed by the Tukey honest significance difference test were used for statistical analysis (α=.05). De-bonding surface microstructure was observed with scanning electron microscopy. Energy dispersive spectroscopy analysis was conducted to evaluate the correlation between ceramic remnants on the metal surface and bond strength values. The mean bond strength value of DMLS was significantly higher than that of DMLM. While no statistically significant difference was found between layer thicknesses, alloy powders closely affected bond strength. Statistical comparisons revealed that the highest bond strength could be achieved with DMLS-Cobalt-Chrome SP2-20μm, and the lowest bond strength was observed in DMLS-Keramit NP-S-20μm (P≤.05). No correlation was found between porcelain remnants on the metal surface and bond strength values. The layered manufacturing device and the alloy powders evaluated in the current study closely affected the bond strength of dental porcelain to a metal framework

  15. Barrier layers against oxygen transmission on the basis of electron beam cured methacrylated gelatin

    Science.gov (United States)

    Scherzer, Tom

    1997-08-01

    The development of barrier layers against oxygen transmission on the basis of radiation-curable methacrylated gelatin will be reported. The electron beam cured gelatin coatings show an extremely low oxygen permeability and a high resistance against boiling water. Moreover, the methacrylated gelatins possess good adhesion characteristics. Therefore, they are suited as barrier adhesives in laminates for food packaging applications. If substrate foils from biodegradable polymers are used, the development of completely biodegradable packaging materials seems to be possible.

  16. The role of oxygen in the deposition of copper–calcium thin film as diffusion barrier for copper metallization

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Zhinong, E-mail: znyu@bit.edu.cn [School of Optoelectronics and Beijing Engineering Research Center of Mixed Reality and Advanced Display, Beijing Institute of Technology, Beijing 100081 (China); Ren, Ruihuang [School of Optoelectronics and Beijing Engineering Research Center of Mixed Reality and Advanced Display, Beijing Institute of Technology, Beijing 100081 (China); Xue, Jianshe; Yao, Qi; Li, Zhengliang; Hui, Guanbao [Beijing BOE Optoelectronics Technology Co., Ltd, Beijing 100176 (China); Xue, Wei [School of Optoelectronics and Beijing Engineering Research Center of Mixed Reality and Advanced Display, Beijing Institute of Technology, Beijing 100081 (China)

    2015-02-15

    Highlights: • The CuCa film as the diffusion barrier of Cu film improves the adhesion of Cu film. • The introduction of oxygen into the deposition of CuCa film is necessary to improve the adhesion of Cu film. • The CuCa alloy barrier layer deposited at oxygen atmosphere has perfect anti-diffusion between Cu film and substrate. - Abstract: The properties of copper (Cu) metallization based on copper–calcium (CuCa) diffusion barrier as a function of oxygen flux in the CuCa film deposition were investigated in view of adhesion, diffusion and electronic properties. The CuCa film as the diffusion barrier of Cu film improves the adhesion of Cu film, however, and increases the resistance of Cu film. The introduction of oxygen into the deposition of CuCa film induces the improvement of adhesion and crystallinity of Cu film, but produces a slight increase of resistance. The increased resistance results from the partial oxidation of Cu film. The annealing process in vacuum further improves the adhesion, crystallinity and conductivity of Cu film. X-ray diffraction (XRD) and Auger electron spectroscopy (AES) show that the CuCa alloy barrier layer deposited at oxygen atmosphere has perfect anti-diffusion between Cu film and substrate due to the formation of Ca oxide in the interface of CuCa/substrate.

  17. Growth of transition metals on cerium tungstate model catalyst layers

    Science.gov (United States)

    Skála, T.; Tsud, N.; Stetsovych, V.; Mysliveček, J.; Matolín, V.

    2016-10-01

    Two model catalytic metal/oxide systems were investigated by photoelectron spectroscopy and scanning tunneling microscopy. The mixed-oxide support was a cerium tungstate epitaxial thin layer grown in situ on the W(1 1 0) single crystal. Active particles consisted of palladium and platinum 3D islands deposited on the tungstate surface at 300 K. Both metals were found to interact weakly with the oxide support and the original chemical state of both support and metals was mostly preserved. Electronic and morphological changes are discussed during the metal growth and after post-annealing at temperatures up to 700 K. Partial transition-metal coalescence and self-cleaning from the CO and carbon impurities were observed.

  18. Influence of polycrystalline silicon layer on flow through «metal — p-Si» contact

    Directory of Open Access Journals (Sweden)

    Smyntyna V. A.

    2011-11-01

    Full Text Available Based on the results of investigations of charge transport in the "metal — p-Si" contacts with different thickness of polycrystalline p-Si layer the mechanisms of charge transport through such structures are shown. It is established that with increasing thickness of the layer of polycrystalline p-Si current transport mechanism changes from a double injection into the drift-diffusion. This change is due to an increase in the drift current component in the space charge zone of "metal — p-Si" contact, which arises as a result of increased surface density of scattering barriers, which are localized at the boundaries of neighboring silicon polycrystals.

  19. Contact resistance at planar metal contacts on bilayer graphene and effects of molecular insertion layers

    Science.gov (United States)

    Nouchi, Ryo

    2017-03-01

    The possible origins of metal–bilayer graphene (BLG) contact resistance are investigated by taking into consideration the bandgap formed by interfacial charge transfer at the metal contacts. Our results show that a charge injection barrier (Schottky barrier) does not contribute to the contact resistance because the BLG under the contacts is always degenerately doped. We also showed that the contact-doping-induced increase in the density of states (DOS) of BLG under the metal contacts decreases the contact resistance owing to enhanced charge carrier tunnelling at the contacts. The contact doping can be enhanced by inserting molecular dopant layers into the metal contacts. However, carrier tunnelling through the insertion layer increases the contact resistance, and thus, alternative device structures should be employed. Finally, we showed that the inter-band transport by variable range hopping via in-gap states is the largest contributor to contact resistance when the carrier type of the gated channel is opposite to the contact doping carrier type. This indicates that the strategy of contact resistance reduction by the contact-doping-induced increase in the DOS is effective only for a single channel transport branch (n- or p-type) depending on the contact doping carrier type.

  20. High-flux Thin-film Nanofibrous Composite Ultrafiltration Membranes Containing Cellulose Barrier Layer

    Energy Technology Data Exchange (ETDEWEB)

    Ma, H.; Yoon, K; Rong, L; Mao, Y; Mo, Z; Fang, D; Hollander, Z; Gaiteri, J; Hsiao , B; Chu, B

    2010-01-01

    A novel class of thin-film nanofibrous composite (TFNC) membrane consisting of a cellulose barrier layer, a nanofibrous mid-layer scaffold, and a melt-blown non-woven substrate was successfully fabricated and tested as an ultrafiltration (UF) filter to separate an emulsified oil and water mixture, a model bilge water for on-board ship bilge water purification. Two ionic liquids: 1-butyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium acetate, were chosen as the solvent to dissolve cellulose under mild conditions. The regenerated cellulose barrier layer exhibited less crystallinity (determined by wide-angle X-ray diffraction, WAXD) than the original cotton linter pulps, but good thermal stability (determined by thermal gravimetric analysis, TGA). The morphology, water permeation, and mechanical stability of the chosen TFNCmembranes were thoroughly investigated. The results indicated that the polyacrylonitrile (PAN) nanofibrous scaffold was partially imbedded in the cellulose barrier layer, which enhanced the mechanical strength of the top barrier layer. The permeation flux of the cellulose-based TFNCmembrane was significantly higher (e.g. 10x) than comparable commercial UFmembranes (PAN10 and PAN400, Sepro) with similar rejection ratios for separation of oil/water emulsions. The molecular weight cut-off (MWCO) of TFNC membranes with cellulose barrier layer was evaluated using dextran feed solutions. The rejection was found to be higher than 90% with a dextran molecular weight of 2000 KDa, implying that the nominal pore size of the membrane was less than 50 nm. High permeation flux was also observed in the filtration of an emulsified oil/water mixture as well as of a sodium alginate aqueous solution, while high rejection ratio (above 99.5%) was maintained after prolonged operation. A variation of the barrier layer thickness could dramatically affect the permeation flux and the rejection ratio of the TFNCmembranes, while different sources of cellulose

  1. Schottky barrier modulation of metal/4H-SiC junction with thin interface spacer driven by surface polarization charge on 4H-SiC substrate

    Science.gov (United States)

    Choi, Gahyun; Yoon, Hoon Hahn; Jung, Sungchul; Jeon, Youngeun; Lee, Jung Yong; Bahng, Wook; Park, Kibog

    2015-12-01

    The Au/Ni/Al2O3/4H-SiC junction with the Al2O3 film as a thin spacer layer was found to show the electrical characteristics of a typical rectifying Schottky contact, which is considered to be due to the leakiness of the spacer layer. The Schottky barrier of the junction was measured to be higher than an Au/Ni/4H-SiC junction with no spacer layer. It is believed that the negative surface bound charge originating from the spontaneous polarization of 4H-SiC causes the Schottky barrier increase. The use of a thin spacer layer can be an efficient experimental method to modulate Schottky barriers of metal/4H-SiC junctions.

  2. Effect of Oxide Layer in Metal-Oxide-Semiconductor Systems

    Directory of Open Access Journals (Sweden)

    Fan Jung-Chuan

    2016-01-01

    Full Text Available In this work, we investigate the electrical properties of oxide layer in the metal-oxide semiconductor field effect transistor (MOSFET. The thickness of oxide layer is proportional to square root of oxidation time. The feature of oxide layer thickness on the growth time is consistent with the Deal-Grove model effect. From the current-voltage measurement, it is found that the threshold voltages (Vt for MOSFETs with different oxide layer thicknesses are proportional to the square root of the gate-source voltages (Vgs. It is also noted that threshold voltage of MOSFET increases with the thickness of oxide layer. It indicates that the bulk effect of oxide dominates in this MOSFET structure.

  3. Effects of Pt diffusion barrier layer on the interface reaction and electric properties of PZT film/Si ( 111 ) sample

    Institute of Scientific and Technical Information of China (English)

    ZHU, Yong-Fa(朱永法); CAO, Li-Li(曹立礼); YAN, Pei-Yu(阎培渝); LI, Long-Tu(李龙土); YI, Tao(易涛)

    2000-01-01

    The effects of the Pt diffusion barrier layer on the interface diffusion and reaction, crystallization, dielectric and ferroelectric properties of the PZT/Si(111) sample have been studied using XPS, AES and XRD techniques. The results indicate that the Pt diffusion barrier layer between the PZT layer and the Si substrate prohibits the formation of TiCx, TiSix and SiO2 species in the PZT layer. The Pt barrier layer also completely interrupts the diffusion of Si from the Si substrate into the PZT layer and impedes the diffusion of oxygen from air to the Si substrate greatly. Although the Pt layer can not prevent completely the diffusion and reaction between oxygen and silicon, it can prevent the formation of a stable SiO2 interface layer on the interface of PZT/Si. The Pt layer reacts with silicon to form PtSix species on the interface of Pt/Si, which can intensify the chemical binding strength between the Pt layer and the Si substrate. To play a good role as a diffusion barrier layer, the Pt barrier layer must be not thinner than 140 nm. The existence of the Pt layer not only promotes the crystallization of PZT layer to form a perovskite phase but also improves dielectric and ferroelectric performances of the PZT layer.

  4. Investigation of Top/bottom Electrode and Diffusion Barrier Layer for PZT thick film MEMS Sensors

    DEFF Research Database (Denmark)

    Pedersen, Thomas; Hindrichsen, Christian Carstensen; Lou-Møller, R.

    2007-01-01

    In this work screen printed piezoelectric Ferroperm PZ26 lead zirconate titanate (PZT) thick film is used for two MEMS devices. A test structure is used to investigate several aspects regarding bottom and top electrodes. 450 nm ZrO2 thin film is found to be an insufficient diffusion barrier layer...

  5. Seasonal variability of the observed barrier layer in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Pankajakshan, T.; Thoppil, P.; Rao, R.R.; Muraleedharan, P.M.; Somayajulu, Y.K.; Gopalakrishna, V.V.; Murthugudde, R.; Reddy, G.V.; Revichandran, C.

    The formation mechanisms of the barrier layer (BL) and its seasonal variability in the Arabian Sea (AS) are studied using a comprehensive dataset of temperature and salinity profiles from Argo and other archives for the AS. Relatively thick BL of 20...

  6. Artificial pinning centers using the barrier layer of ordered nanoporous alumina templates

    DEFF Research Database (Denmark)

    Hallet, X.; Mátéfi-Tempfli, Stefan; Mátéfi-Tempfli, M.

    2009-01-01

    The barrier layer of self-ordered anodized aluminium oxide, which is grown from an aluminium foil, has been revealed by a selective chemical etching of the remaining aluminium. The surface obtained in this way consists of a triangular lattice of bumps with 100nm spacing, and heights of approximat...

  7. The Effect of a CGO Barrier Layer on the Performance of LSM/YSZ SOFC Cathodes

    DEFF Research Database (Denmark)

    Kammer Hansen, Kent; Menon, Mohan; Knudsen, Jesper

    2010-01-01

    by spin coating. Electrochemical impedance spectroscopy (EIS) was used to evaluate the performance of the LSM/YSZ composite electrodes. It was shown that the CGO barrier layer affects both the performance of the LSM/YSZ composite electrodes and the series resistance of the cells. This indicates...

  8. Separated effects of ions, metastables and photons on the properties of barrier layers on polymers

    Science.gov (United States)

    Biskup, Beatrix; Boeke, Marc; Benedikt, Jan; von Keudell, Achim

    2016-09-01

    Analyses of a-C:H /a-Si:H multilayers on polymer substrates indicated that prolonged ion bombardment influences negatively the properties of the barrier layer, while a short plasma pretreatment can improve the barrier effect. This work is motivated by these results and investigates the influence of different reactive plasma components, namely ions, metastables and VUV-photons, on the properties of the grown barrier layer. To separate the different species and their influence on plasma pretreatment and film growth, we build a grid system, which repels the ions from the substrate, so that only metastables and VUV-photons have an effect on the layer. An integral part of this investigation is, to measure the photon fluxes to the substrate by an intensity calibrated VUV monochromator. For that, a differentially pumped monochromator with a spectral range 30 - 300 nm is used, where the two most prominent argon lines at 104.9 and 106.8 nm can be measured. In this approach we are able to study the different effects of the plasma species and also possible synergy effects, to improve the properties of the barrier layer. This work is supported by the DFG within the SFB-TR 87.

  9. Nanosecond spin relaxation times in single layer graphene spin valves with hexagonal boron nitride tunnel barriers

    Science.gov (United States)

    Singh, Simranjeet; Katoch, Jyoti; Xu, Jinsong; Tan, Cheng; Zhu, Tiancong; Amamou, Walid; Hone, James; Kawakami, Roland

    2016-09-01

    We present an experimental study of spin transport in single layer graphene using atomic sheets of hexagonal boron nitride (h-BN) as a tunnel barrier for spin injection. While h-BN is expected to be favorable for spin injection, previous experimental studies have been unable to achieve spin relaxation times in the nanosecond regime, suggesting potential problems originating from the contacts. Here, we investigate spin relaxation in graphene spin valves with h-BN barriers and observe room temperature spin lifetimes in excess of a nanosecond, which provides experimental confirmation that h-BN is indeed a good barrier material for spin injection into graphene. By carrying out measurements with different thicknesses of h-BN, we show that few layer h-BN is a better choice than monolayer for achieving high non-local spin signals and longer spin relaxation times in graphene.

  10. Probing Cu Diffusion Barrier Layers on Porous Low-Dielectric-Constant Films by Posireonium Annihilation Lifetime Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    HU Yi-Fan; SUN Jia-Ning; Gidley D.W.

    2005-01-01

    @@ Two kinds of Cu diffusion barrier layers, sealedfilms and capped fi1ms, on nanoporous low-dielectric-constant filmsare investigated by positronium annihilation lifetime spectroscopy (PALS). We have found that the minimumthickness of Ta to form an effective diffusion barrier is affected by the pore size. The films with large poresrequire thick barrier layers to form effective diffusion barriers. In addition, a possible ultra-thin diffusion barrier,i.e. a plasma-induced densification layer, has also been investigated. The PALS data confirm that a porouslow-dielectric-constant thin film can be shrunk by exposure to plasma. This shrinkage is confined to a surfacelayer of collapsed pores and forms a dense layer. The dense layer tends to behave as Ps (positronium) diffusionbarriers. Indeed, the controlled thin "skin" layer could prevent Cu diffusion into the underlying dielectrics.

  11. Reactive boundary layers in metallic rolling contacts

    Energy Technology Data Exchange (ETDEWEB)

    Burbank, John

    2016-05-01

    more thorough investigation into the effects of residual austenite on the properties of this material. The high-performance alternative steels, 36NiCrMoV1-5-7 (hot working steel) and 45SiCrMo6 (spring steel), were heat treated as recommended by their respective manufacturers, and were not case-hardened. The selection of materials with and materials without case-hardening allows for an investigation into whether or not case-hardening is even necessary to deliver acceptable friction behaviour and wear performance. Elemental analyses were conducted by multiple methods to ensure accurate results. Residual austenite contents of the steels and the depth profiles of residual stresses were determined by X-Ray diffraction (XRD), for 20MnCr5 ranging from approximately 6 - 14 vol.%, and under 2 vol.% for the alternative alloys. Hardness profiles were taken from the testing surfaces into the material core. The carburization of 20MnCr5 led to higher hardness and the greater concentration of carbon in the carburization zone more representative of a hardened SAE E52100, or 100Cr6/102Cr6, than of a non-case-hardened 20MnCr5. Residual stresses from machining and case-hardening were measured directly at the sample surface. The high-performance steels fulfilled manufacturer expectations in terms of elemental content, with hardness values between 50 - 55 HRC and strongly martensitic microstructure character. With characterization of the chosen materials complete, the materials could then be subjected to pre-conditioning. The first pre-conditioning method involved targeted generation of cold work hardening as induced boundary layers to protect the contact zone against wear. Work hardening was identified both by variations in residual stress profiles, i.e. the introduction of beneficial compressive residual stresses, and hardness increases in the contact zone, providing enhanced wear resistance. Parameters for work hardening were further optimized to reduce damage to the surface substrates

  12. Development of Barrier Layers for the Protection of Candidate Alloys in the VHTR

    Energy Technology Data Exchange (ETDEWEB)

    Levi, Carlos G. [Battelle Energy Alliance, LLC, Idaho Falls, ID (United States); Jones, J. Wayne [Battelle Energy Alliance, LLC, Idaho Falls, ID (United States); Pollock, Tresa M. [Battelle Energy Alliance, LLC, Idaho Falls, ID (United States); Was, Gary S. [Battelle Energy Alliance, LLC, Idaho Falls, ID (United States)

    2015-01-22

    The objective of this project was to develop concepts for barrier layers that enable leading candi- date Ni alloys to meet the longer term operating temperature and durability requirements of the VHTR. The concepts were based on alpha alumina as a primary surface barrier, underlay by one or more chemically distinct alloy layers that would promote and sustain the formation of the pro- tective scale. The surface layers must possess stable microstructures that provide resistance to oxidation, de-carburization and/or carburization, as well as durability against relevant forms of thermo-mechanical cycling. The system must also have a self-healing ability to allow endurance for long exposure times at temperatures up to 1000°C.

  13. TiO{sub 2} nanotube layers with metallic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Tsuchiya, Hiroaki; Tokuoka, Nozomu; Honda, Shinji; Shinkai, Yuji; Shimizu, Yasutomo; Fujimoto, Shinji [Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)], E-mail: tsuchiya@mat.eng.osaka-u.ac.jp

    2009-05-01

    The present work reports the deposition behavior of Pd or Ag particles on TiO{sub 2} nanotube layers with an average diameter of 100 nm and length of 500 nm. The deposition of Pd or Ag particles is carried out by photo-induced reduction of metal ions. TiO{sub 2} nanotube layers are exposed to UV irradiation in an electrolyte containing Pd ions. Pd deposition behavior strongly depends on the crystal structure of TiO{sub 2} nantoube layers. As-anodized nanotube layers are in the amorphous state and can be converted to anatase without any changes in structural integrity. On as-formed amorphous nanotube layer, no Pd particles are deposited whereas in the case of anatase nanotube layer many Pd particles are formed by UV irradiation in PdCl2 electrolyte. However, the size of Pd particles is larger than the diameter of nanotubes and increases with irradiation time. In order to circumvent this problem, TiO{sub 2} nanotube layer is immersed in an electrolyte, then rinsed with deionized water, followed by exposure to UV irradiation. This results in the deposition of Ag nanoparticles with the size of 10 nm on and inside nanotubes. Photocurrent measurements reveal that the presence of Ag nanoparticles on TiO{sub 2} nanotube layer enhances the absorption efficiency of dye, leading to higher photocurrent.

  14. Vacuum barrier for excimer lasers

    Energy Technology Data Exchange (ETDEWEB)

    Shurter, R.P.

    1990-10-10

    This invention is comprised of a barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yearns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput.

  15. Programme and retention characteristics of SONOS memory arrays with layered tunnel barrier

    Science.gov (United States)

    Golubović, D. S.; Vianello, E.; Arreghini, A.; Driussi, F.; van Duuren, M. J.; Akil, N.; Selmi, L.; Esseni, D.

    2008-07-01

    Layered tunnel barriers (T-ONO) might help circumvent retention limitations of nitride charge trapping devices (SONOS) programmed/erased by direct tunnelling without invoking high-K dielectrics in the gate stack. In order to establish to what extent the properties of a T-ONO tunnel layer influence the performance of SONOS memories, NOR memory arrays containing a silicon oxide/silicon nitride/silicon oxide T-ONO layer, a silicon nitride charge trapping layer and a silicon oxide blocking layer were fabricated and investigated. The T-ONO layer was formed using wet reoxidation of the silicon nitride, as this process is known to generate a lot of traps at the interface between silicon nitride and silicon oxide, as well as in the reoxidized portion of the silicon nitride itself. Besides standard memory measurements like programme/erase behaviour, endurance and retention, charge centroid extraction measurements were carried out in order to explain the retention behaviour and associate it with the position of the charge. It has been demonstrated that the performance of SONOS memories with a T-ONO layer strongly depends on the technological properties/quality of the T-ONO barrier which, therefore, may not be a universal solution to retention problems in SONOS devices.

  16. Solution processed metal oxide thin film hole transport layers for high performance organic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Steirer, K. Xerxes; Berry, Joseph J.; Chesin, Jordan P.; Lloyd, Matthew T.; Widjonarko, Nicodemus Edwin; Miedaner, Alexander; Curtis, Calvin J.; Ginley, David S.; Olson, Dana C.

    2017-01-10

    A method for the application of solution processed metal oxide hole transport layers in organic photovoltaic devices and related organic electronics devices is disclosed. The metal oxide may be derived from a metal-organic precursor enabling solution processing of an amorphous, p-type metal oxide. An organic photovoltaic device having solution processed, metal oxide, thin-film hole transport layer.

  17. Impedance of a coil near an imperfectly layered metal structure: The layer approximation

    Science.gov (United States)

    Satveli, Radhika; Moulder, John C.; Wang, Bing; Rose, James H.

    1996-03-01

    Changes in the impedance of a coil next to a one-dimensional layered conductor due to three-dimensional changes in the conductivity are studied. Eddy current probes are often used to inspect layered one-dimensional, nonmagnetic metal structures whose electrical conductivity varies primarily with depth beneath the surface. We present a perturbation method, the ``layer approximation,'' which yields simple and readily evaluated formulas for changes in the impedance of a small coil due to localized three-dimensional variations in the conductivity. The layer approximation is constructed to be accurate when the conductivity change due to the defect is small or the defect is nearly one-dimensional. The impedance is calculated and reported for a variety of defects in layered metal structures: voids, inclusions, interfacial roughness, and fasteners. We test the ``robustness'' of the layer approximation using an extreme case, a flat-bottom hole in an aluminum plate, as a ``benchmark.'' Both experimental measurements and more exact theoretical calculations are reported. Impedance measurements were made with a Hewlett-Packard 4194A impedance analyzer for a right-cylindrical flat-bottom hole in a 1-mm-thick 2024 aluminum alloy plate; the hole was on the side opposite to the coil. Frequencies were varied from 2.5 to 50 kHz. We also calculated the change in the impedance for this benchmark problem using the numerically exact volume integral method. For this benchmark problem, the layer approximation is in good agreement with experiment and more exact theory.

  18. Geochemical barriers for environment protection and recovery of nonferrous metals.

    Science.gov (United States)

    Chanturiya, Valentine; Masloboev, Vladimir; Makarov, Dmitriy; Nesterov, Dmitriy; Bajurova, Julia; Svetlov, Anton; Men'shikov, Yuriy

    2014-01-01

    A study of natural minerals, ore tailings and their products as materials for artificial geochemical barriers is presented. In particular, it focuses on interaction between calcite and dolomite and sulfate solutions containing nickel, copper and iron under static conditions. Calcite of -0.1 mm fraction has been shown to perform well as a barrier when added to water phases of tailing dumps and natural reservoirs. Experiments under dynamic conditions have revealed a high potential of thermally activated copper-nickel tailings as barriers. After a 500-day precipitating period on a geochemical barrier, the contents of nickel and copper in ore dressing tailings were found to increase 12- and 28-fold, respectively. An effective sorbent of copper, iron and nickel ions is a brucite-based product of hydrochloric acid treatment of vermiculite ore tailings. Its sorption capacity can be essentially increased through thermal activation.

  19. Anisotropy in layered half-metallic Heusler alloy superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Azadani, Javad G.; Munira, Kamaram; Sivakumar, Chockalingam; Butler, William H. [Center for Materials for Information Technology, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Romero, Jonathon [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Ma, Jianhua; Ghosh, Avik W. [Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)

    2016-01-28

    We show that when two Heusler alloys are layered in the [001], [110], or [111] directions for various thicknesses to form a superlattice, the Slater-Pauling rule may still be satisfied and the resulting superlattice is often half-metallic with gaps comparable to or larger than those of its constituents. In addition, uniaxial magnetocrystalline anisotropy is induced because of the differences in the electronic structure of the two Heuslers in the superlattice. Various full-full, full-half, and half-half Heusler superlattices are studied, and potential half-metallic superlattices with perpendicular magnetocrystalline anisotropy are identified.

  20. Determination of the Schottky barrier height of ferromagnetic contacts to few-layer phosphorene

    Energy Technology Data Exchange (ETDEWEB)

    Anugrah, Yoska; Robbins, Matthew C.; Koester, Steven J. [Department of Electrical and Computer Engineering, University of Minnesota-Twin Cities, Minneapolis, Minnesota 55455 (United States); Crowell, Paul A. [School of Physics and Astronomy, University of Minnesota-Twin Cities, Minneapolis, Minnesota 55455 (United States)

    2015-03-09

    Phosphorene, the 2D analogue of black phosphorus, is a promising material for studying spin transport due to its low spin-orbit coupling and its ½ nuclear spin, which could allow the study of hyperfine effects. In this work, the properties of permalloy (Py) and cobalt (Co) contacts to few-layer phosphorene are presented. The Schottky barrier height was extracted and determined as a function of gate bias. Flat-band barrier heights, relative to the valence band edge, of 110 meV and 200 meV were determined for Py and Co, respectively. These results are important for future studies of spin transport in phosphorene.

  1. Few-layer MoS2 as nitrogen protective barrier

    Science.gov (United States)

    Akbali, B.; Yanilmaz, A.; Tomak, A.; Tongay, S.; Çelebi, C.; Sahin, H.

    2017-10-01

    We report experimental and theoretical investigations of the observed barrier behavior of few-layer MoS2 against nitrogenation. Owing to its low-strength shearing, low friction coefficient, and high lubricity, MoS2 exhibits the demeanor of a natural N-resistant coating material. Raman spectroscopy is done to determine the coating capability of MoS2 on graphene. Surface morphology of our MoS2/graphene heterostructure is characterized by using optical microscopy, scanning electron microscopy, and atomic force microscopy. In addition, density functional theory-based calculations are performed to understand the energy barrier performance of MoS2 against nitrogenation. The penetration of nitrogen atoms through a defect-free MoS2 layer is prevented by a very high vertical diffusion barrier, indicating that MoS2 can serve as a protective layer for the nitrogenation of graphene. Our experimental and theoretical results show that MoS2 material can be used both as an efficient nanocoating material and as a nanoscale mask for selective nitrogenation of graphene layer.

  2. Sloshing instability and electrolyte layer rupture in liquid metal batteries

    Science.gov (United States)

    Weber, Norbert; Beckstein, Pascal; Herreman, Wietze; Horstmann, Gerrit Maik; Nore, Caroline; Stefani, Frank; Weier, Tom

    2017-05-01

    Liquid metal batteries (LMBs) are discussed today as a cheap grid scale energy storage, as required for the deployment of fluctuating renewable energies. Built as stable density stratification of two liquid metals separated by a thin molten salt layer, LMBs are susceptible to short-circuit by fluid flows. Using direct numerical simulation, we study a sloshing long wave interface instability in cylindrical cells, which is already known from aluminium reduction cells. After characterising the instability mechanism, we investigate the influence of cell current, layer thickness, density, viscosity, conductivity and magnetic background field. Finally we study the shape of the interface and give a dimensionless parameter for the onset of sloshing as well as for the short-circuit.

  3. Electron and Positron State in Layered Nanostructures «Metal – Insulator»

    Directory of Open Access Journals (Sweden)

    А.V. Babich

    2016-11-01

    Full Text Available Within the framework of modified method of Kohn-Sham and stable jelly model with taking into account image forces and conduction band profiles of the dielectric self-consistent calculations of potential profiles, and the work functions, the Schottky barriers for asymmetric metal dielectric film systems in which insulators on both sides of the metal nanofilms are different were done. Dielectric environment generally leads to negative changes in the electron work function and surface energy. In view of the conduction band of the dielectric (solid inert gases, dimensional effects, the impact of effective mass to energy and positron annihilation characteristics in layered structures with self-consistent hybrid potential profiles, which built in the local density approximation and crosslinked with image potentials were investigated. The possibility of localization of positronium atoms in nanosandvich is discussed. Comparison with the experiments were done.

  4. Thermal shock behavior of toughened gadolinium zirconate/YSZ double-ceramic-layered thermal barrier coating

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Xinghua, E-mail: xhzhong@mail.sic.ac.cn; Zhao, Huayu; Zhou, Xiaming; Liu, Chenguang; Wang, Liang; Shao, Fang; Yang, Kai; Tao, Shunyan; Ding, Chuanxian

    2014-04-01

    Highlights: • Gd{sub 2}Zr{sub 2}O{sub 7}/YSZ DCL thermal barrier coating was designed and fabricated. • The Gd{sub 2}Zr{sub 2}O{sub 7} top ceramic layer was toughened by addition of nanostructured 3YSZ. • Remarkable improvement in thermal shock resistance of the DCL coating was achieved. - Abstract: Double-ceramic-layered (DCL) thermal barrier coating system comprising of toughened Gadolinium zirconate (Gd{sub 2}Zr{sub 2}O{sub 7}, GZ) as the top ceramic layer and 4.5 mol% Y{sub 2}O{sub 3} partially-stabilized ZrO{sub 2} (4.5YSZ) as the bottom ceramic layer was fabricated by plasma spraying and thermal shock behavior of the DCL coating was investigated. The GZ top ceramic layer was toughened by addition of nanostructured 3 mol% Y{sub 2}O{sub 3} partially-stabilized ZrO{sub 2} (3YSZ) to improve fracture toughness of the matrix. The thermal shock resistance of the DCL coating was enhanced significantly compared to that of single-ceramic-layered (SCL) GZ-3YSZ composite coating, which is believed to be primarily attributed to the two factors: (i) the increase in fracture toughness of the top ceramic layer by incorporating nanostructured YSZ particles and (ii) the improvement in strain tolerance through the utilization of 4.5YSZ as the bottom ceramic layer. In addition, the failure mechanisms are mainly attributed to the still low fracture toughness of the top ceramic layer and oxidation of the bond-coat.

  5. Metal-Organic Frameworks for Thin-Layer Chromatographic Applications.

    Science.gov (United States)

    Schenk, Claudia; Kutzscher, Christel; Drache, Franziska; Helten, Stella; Senkovska, Irena; Kaskel, Stefan

    2017-01-25

    Preparation of thin-layer chromatographic (TLC) plates based on metal-organic frameworks (MOFs) as porous stationary phases is described. DUT-67 (DUT = Dresden University of Technology), a zirconium based MOF, was used in combination with a fluorescent indicator as stationary phase for analyzing a small selection of a wide spectrum of relevant analytes. The successful separation of benzaldehyde from trans-cinnamaldehyde and 4-aminophenol from 2-aminotoluene is reported as a model system using optimized eluent mixtures containing acetic acid.

  6. Schottky barrier height of Ni/TiO2/4H-SiC metal-insulator-semiconductor diodes

    Science.gov (United States)

    Kaufmann, Ivan R.; Pereira, Marcelo B.; Boudinov, Henri I.

    2015-12-01

    Ni/TiO2/4H-SiC diodes were analysed through measurements of current-voltage curves varying the temperature. The Schottky Barrier Height (SBH) which increased with temperature was studied by simulation of the Thermionic Emission Model, considering Ni/SiC Schottky structures with an insulator layer between the metal and semiconductor. This model shows that a new method of calculation should be applied to diodes that have a metal-insulator-semiconductor structure. Misleading results for SBH are obtained if the thin insulator layer is not considered. When applying the suggested method to the Ni/TiO2/4H-SiC diodes it was necessary to consider not only the deposited TiO2 layer, but also a second dielectric layer of native SiCxOy at the surface of SiC. By measuring I-V-T curves for two samples with different thicknesses of TiO2, the suggested method allows one to estimate the thicknesses of both dielectric layers: TiO2 and SiOxCy.

  7. Mechanisms governing the interfacial delamination of thermal barrier coating system with double ceramic layers

    Science.gov (United States)

    Xu, Rong; Fan, Xueling; Wang, T. J.

    2016-05-01

    A systematic study of factors affecting the interfacial delamination of thermal barrier coating system (TBCs) with double ceramic layers (DCL) is presented. Crack driving forces for delaminations at two weak interfaces are examined. The results show that a thicker outermost ceramic layer can induce dramatic increase in crack driving force and make the interface between two ceramic coatings become more prone to delamination. The behavior is shown to be more prominent in TBCs with stiffer outmost coating. The thickness ratio of two ceramic layers is an important parameter for controlling the failure mechanisms and determining the lifetime of DCL TBCs under inservice condition. By accounting for the influences of thickness ratio of two ceramic layers and interfacial fracture toughnesses of two involved interfaces, the fracture mechanism map of DCL TBCs has been constructed, in which different failure mechanisms are identified. The results quanlitatively agree with the aviliable experimental data.

  8. Alumina Paste Layer as a Sublimation Suppression Barrier for Yb14MnSb11

    Science.gov (United States)

    Paik, Jong-Ah; Caillat, Thierry

    2010-01-01

    Sublimation is a major cause of degradation of thermoelectric power generation systems. Most thermoelectric materials tend to have peak values at the temperature where sublimation occurs. A sublimation barrier is needed that is stable at operating temperatures, inert against thermoelectric materials, and able to withstand thermal cycling stress. A porous alumina paste layer is suitable as a sublimation barrier for Yb14MnSb11. It can accommodate stress generated by the thermal expansion discrepancy between the suppression layer and thermoelectric materials. Sublimation suppression is achieved by filling pores naturally with YbO2, a natural byproduct of sublimation. YbO2 generated during the sublimation of Yb14MnSb11 fills the porous structure of the alumina paste, causing sublimation to decrease with time as the pores become filled.

  9. Diurnal evolution of the barrier layer and its local feedback in the central Taiwan Strait

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Diurnal evolution of the barrier layer (BL) and its local feedback features in the central Taiwan Strait (119.2oE,24.3oN) during summertime monsoon are investigated using in situ moored observations conducted by the "Yan-Ping 2" research vessel in late June 2005.During the initiation phase,for the non-solar radiation tends to be trapped in the upper mixed layer,whereas the solar radiation can penetrate deeply through the mixed layer approaching the thermocline,most heat is accumulated inside the BL inducing an inverse-thermal layer.Along with heat convergence inside the BL,thermal exchange increases between the BL and the overlaying mixed layer and finally,a prominently warming mixed layer is formed.Moreover,the BL is associated with a buoyancy frequency minimum with mild stability.Further analysis reveals that the BL’s local feedbacks can be divided into two aspects,on one hand,the BL can generate dramatic changes in the local sensible and latent heat fluxes;on the other hand,the sub-halocline and the thermocline serve as two interfaces during the downward transmission of the wind stirring turbulent kinetic energy (TKE) and as a result,most TKE is retarded by the shallow halocline and being trapped above the upper mixed layer,while the residual pierced through the base of the mixed layer is likewise blocked by the thermocline.

  10. Suitability of polystyrene as a functional barrier layer in coloured food contact materials.

    Science.gov (United States)

    Genualdi, Susan; Addo Ntim, Susana; Begley, Timothy

    2015-01-01

    Functional barriers in food contact materials (FCMs) are used to prevent or reduce migration from inner layers in multilayer structures to food. The effectiveness of functional barrier layers was investigated in coloured polystyrene (PS) bowls due to their intended condition of use with hot liquids such as soups or stew. Migration experiments were performed over a 10-day period using USFDA-recommended food simulants (10% ethanol, 50% ethanol, corn oil and Miglyol) along with several other food oils. At the end of the 10 days, solvent dyes had migrated from the PS bowls at 12, 1 and 31,000 ng cm(-)(2) into coconut oil, palm kernel oil and Miglyol respectively, and in coconut oil and Miglyol the colour change was visible to the human eye. Scanning electron microscope (SEM) images revealed that the functional barrier was no longer intact for the bowls exposed to coconut oil, palm kernel oil, Miglyol, 10% ethanol, 50% ethanol and goat's milk. Additional tests showed that 1-dodecanol, a lauryl alcohol derived from palm kernel oil and coconut oil, was present in the PS bowls at an average concentration of 11 mg kg(-1). This compound is likely to have been used as a dispersing agent for the solvent dye and aided the migration of the solvent dye from the PS bowl into the food simulant. The solvent dye was not found in the 10% ethanol, 50% ethanol and goat's milk food simulants above their respective limits of detection, which is likely to be due to its insolubility in aqueous solutions. A disrupted barrier layer is of concern because if there are unregulated materials in the inner layers of the laminate, they may migrate to food, and therefore be considered unapproved food additives resulting in the food being deemed adulterated under the Federal Food Drug and Cosmetic Act.

  11. Spray pyrolysis of doped-ceria barrier layers for solid oxide fuel cells

    DEFF Research Database (Denmark)

    Szymczewska, Dagmara; Chrzan, Aleksander; Karczewski, Jakub

    2017-01-01

    Gadolinium doped ceria (Ce0.8Gd0.2O2 − x-CGO) layer fabricated by spray pyrolysis is investigated as the diffusion barrier for solid oxide fuel cell. It is deposited between the La0.6Sr0.4FeO3 − δ cathode and the yttria stabilized zirconia electrolyte to mitigate harmful interdiffusion...

  12. Observations of capillary barriers and preferential flow in layered snow during cold laboratory experiments

    Science.gov (United States)

    Avanzi, Francesco; Hirashima, Hiroyuki; Yamaguchi, Satoru; Katsushima, Takafumi; De Michele, Carlo

    2016-09-01

    Data of liquid water flow around a capillary barrier in snow are still limited. To gain insight into this process, we carried out observations of dyed water infiltration in layered snow at 0 °C during cold laboratory experiments. We considered three different finer-over-coarser textures and three different water input rates. By means of visual inspection, horizontal sectioning, and measurements of liquid water content (LWC), capillary barriers and associated preferential flow were characterized. The flow dynamics of each sample were also simulated solving the Richards equation within the 1-D multi-layer physically based snow cover model SNOWPACK. Results revealed that capillary barriers and preferential flow are relevant processes ruling the speed of water infiltration in stratified snow. Both are marked by a high degree of spatial variability at centimeter scale and complex 3-D patterns. During unsteady percolation of water, observed peaks in bulk volumetric LWC at the interface reached ˜ 33-36 vol % when the upper layer was composed by fine snow (grain size smaller than 0.5 mm). However, LWC might locally be greater due to the observed heterogeneity in the process. Spatial variability in water transmission increases with grain size, whereas we did not observe a systematic dependency on water input rate for samples containing fine snow. The comparison between observed and simulated LWC profiles revealed that the implementation of the Richards equation reproduces the existence of a capillary barrier for all observed cases and yields a good agreement with observed peaks in LWC at the interface between layers.

  13. The effect of asymmetric barrier layers in the waveguide region on power characteristics of QW lasers

    DEFF Research Database (Denmark)

    Zubov, F. I.; Zhukov, A. E.; Shernyakov, Yu M.

    2015-01-01

    Current-voltage and light-current characteristics of quantum-well lasers have been studied at high drive currents. The introduction of asymmetric barrier layers adjacent to the active region caused a significant suppression of the nonlinearity in the light-current characteristic and an increase...... in the external differential efficiency. As a result, the maximum wallplug efficiency increased by 9%, while the output optical power increased by 29%....

  14. Enhancement of Thermal Conductance at Metal-Dielectric Interfaces Using Subnanometer Metal Adhesion Layers

    Science.gov (United States)

    Jeong, Minyoung; Freedman, Justin P.; Liang, Hongliang Joe; Chow, Cheng-Ming; Sokalski, Vincent M.; Bain, James A.; Malen, Jonathan A.

    2016-01-01

    We show that the use of subnanometer adhesion layers significantly enhances the thermal interface conductance at metal-dielectric interfaces. A metal-dielectric interface between Au and sapphire (Al2O3) is considered using Cu (low optical loss) and Cr (high optical loss) as adhesion layers. To enable high throughput measurements, each adhesion layer is deposited as a wedge such that a continuous range of thicknesses could be sampled. Our measurements of thermal interface conductance at the metal-Al2O3 interface made using frequency-domain thermoreflectance show that a 1-nm-thick adhesion layer of Cu or Cr is sufficient to enhance the thermal interface conductance by more than a factor of 2 or 4, respectively, relative to the pure Au/Al2O3 interface. The enhancement agrees with the diffuse-mismatch-model-based predictions of accumulated thermal conductance versus adhesion-layer thickness assuming that it contributes phonons with wavelengths less than its thickness, while those with longer wavelengths transmit directly from the Au.

  15. A high rotational barrier for physisorbed hydrogen in an fcu-metal-organic framework

    KAUST Repository

    Pham, Tony T.

    2014-01-01

    A combined inelastic neutron scattering (INS) and theoretical study of H2 sorption in Y-FTZB, a recently reported metal-organic framework (MOF) with fcu topology, reveals that the strongest binding site in the MOF causes a high barrier to rotation on the sorbed H2. This rotational barrier for H2 is the highest yet of reported MOF materials based on physisorption. This journal is

  16. Selective and low temperature transition metal intercalation in layered tellurides

    Science.gov (United States)

    Yajima, Takeshi; Koshiko, Masaki; Zhang, Yaoqing; Oguchi, Tamio; Yu, Wen; Kato, Daichi; Kobayashi, Yoji; Orikasa, Yuki; Yamamoto, Takafumi; Uchimoto, Yoshiharu; Green, Mark A.; Kageyama, Hiroshi

    2016-12-01

    Layered materials embrace rich intercalation reactions to accommodate high concentrations of foreign species within their structures, and find many applications spanning from energy storage, ion exchange to secondary batteries. Light alkali metals are generally most easily intercalated due to their light mass, high charge/volume ratio and in many cases strong reducing properties. An evolving area of materials chemistry, however, is to capture metals selectively, which is of technological and environmental significance but rather unexplored. Here we show that the layered telluride T2PTe2 (T=Ti, Zr) displays exclusive insertion of transition metals (for example, Cd, Zn) as opposed to alkali cations, with tetrahedral coordination preference to tellurium. Interestingly, the intercalation reactions proceed in solid state and at surprisingly low temperatures (for example, 80 °C for cadmium in Ti2PTe2). The current method of controlling selectivity provides opportunities in the search for new materials for various applications that used to be possible only in a liquid.

  17. Influence of vacuum-annealing on the diffusion barrier properties of MOCVD TiN for Cu metallization

    CERN Document Server

    Lee, J G; Lee, E G; Lee, J Y; Kim, K B; Lee, J M

    1999-01-01

    We have investigated the effects of vacuum annealing of TDMAT-sourced TiN on the film qualities, as well as on the properties of the barrier against Cu diffusion. Vacuum annealing at 550 .deg. C to 1000 .deg. C achieved a significant densification of the TiN films with the interaction of Ti in the TiN prepared by metalorganic chemical-vapor deposition (MOCVD TiN) and Si at the interface. This interaction produced a stable interface between TiN and Si. In addition, annealing of the films at 1000 .deg. C transformed the amorphous TiN(C) films into crystalline TiNC solid solutions. About 10 at % silicon diffused into the TiN film from the Si substrate, and oxygen in the as-deposited TiN film was expelled to the surface after annealing at 1000 .deg. C. The barrier failure mechanism of MOCVD TiN in Cu metallization included the indiffusion of Cu and the accompanying outdiffusion of silicon through the barrier layer. The annealing of MOCVD TiN in vacuum improved the diffusion barrier properties, partly due to the d...

  18. Thermoelastic Characteristics in Thermal Barrier Coatings with a Graded Layer between the Top and Bond Coats

    Directory of Open Access Journals (Sweden)

    Seokchan Kim

    2013-01-01

    Full Text Available A graded layer was introduced at the interface between the top and bond coats to reduce the risk of failure in a thermal barrier coating (TBC system, and the thermoelastic behavior was investigated through mathematical approaches. Two types of TBC model with and without the graded layer, subject to a symmetric temperature distribution in the longitudinal direction, were taken into consideration to evaluate thermoelastic behaviors such as temperature distribution, displacement, and thermal stress. Thermoelastic theory was applied to derive two governing partial differential equations, and a finite volume method was developed to obtain approximations because of the complexity. The TBC with the graded layer shows improved durability in thermoelastic characteristics through mathematical approaches, in agreement with the experimental results. The results will be useful in discovering technologies for enhancing the thermomechanical properties of TBCs.

  19. The importance of dye chemistry and TiCl4 surface treatment in the behavior of Al2O3 recombination barrier layers deposited by atomic layer deposition in solid-state dye-sensitized solar cells

    KAUST Repository

    Brennan, Thomas P.

    2012-01-01

    Atomic layer deposition (ALD) was used to fabricate Al 2O 3 recombination barriers in solid-state dye-sensitized solar cells (ss-DSSCs) employing an organic hole transport material (HTM) for the first time. Al 2O 3 recombination barriers of varying thickness were incorporated into efficient ss-DSSCs utilizing the Z907 dye adsorbed onto a 2 μm-thick nanoporous TiO 2 active layer and the HTM spiro-OMeTAD. The impact of Al 2O 3 barriers was also studied in devices employing different dyes, with increased active layer thicknesses, and with substrates that did not undergo the TiCl 4 surface treatment. In all instances, electron lifetimes (as determined by transient photovoltage measurements) increased and dark current was suppressed after Al 2O 3 deposition. However, only when the TiCl 4 treatment was eliminated did device efficiency increase; in all other instances efficiency decreased due to a drop in short-circuit current. These results are attributed in the former case to the similar effects of Al 2O 3 ALD and the TiCl 4 surface treatment whereas the insulating properties of Al 2O 3 hinder charge injection and lead to current loss in TiCl 4-treated devices. The impact of Al 2O 3 barrier layers was unaffected by doubling the active layer thickness or using an alternative ruthenium dye, but a metal-free donor-π-acceptor dye exhibited a much smaller decrease in current due to its higher excited state energy. We develop a model employing prior research on Al 2O 3 growth and dye kinetics that successfully predicts the reduction in device current as a function of ALD cycles and is extendable to different dye-barrier systems. © This journal is the Owner Societies 2012.

  20. Sewage sludge as barrier material for heavy metals in waste landfill

    Directory of Open Access Journals (Sweden)

    Zhang Huyuan

    2016-06-01

    Full Text Available Heavy metal pollutants in the leachate of waste landfill are a potential threat to the environment. In this study, the feasibility of using municipal sewage sludge as barrier material for the containment of heavy metal pollutants from solid waste landfills was evaluated by compaction test and hydraulic conductivity test concerning compaction property, impermeability and heavy metal retardation. Results of the compaction test showed that the maximum dry density of 0.79 g·cm−3 was achieved at the optimum water content of about 60%. The hydraulic conductivities of compacted sewage sludge permeated with synthetic heavy metal solutions were in the range of 1.3×10−8 – 6.2×10−9 cm·s−1, less than 1.0 ×10−7cm·s−1 recommended by regulations for barrier materials. Chemical analyses on the effluent from the hydraulic conductivity tests indicated that the two target heavy metals, Zn and Cd in the permeants were all retarded by compacted sewage sludge, which might be attributed to the precipitation and adsorption of heavy metal ions. The results of this study suggest that specially prepared material from sewage sludge could be used as a barrier for waste landfills for its low permeability and strong retardation to heavy metal pollutants.

  1. Liquid Exfoliation of Layered Transition Metal Dichalcogenides for Biological Applications.

    Science.gov (United States)

    Nguyen, Emily P; Daeneke, Torben; Zhuiykov, Serge; Kalantar-Zadeh, Kourosh

    2016-06-02

    Known to possess distinctive properties that differ greatly from their bulk form, layered two-dimensional materials have been extensively studied and incorporated into many versatile applications ranging from optoelectronics to sensors. For biomedical research, two-dimensional transition metal dichalcogenides (2D TMDs) have garnered much interest as they have been shown to exhibit relatively low toxicity, high stability in aqueous environments, and the ability to adhere to biological materials such as proteins. These materials are promising candidates, demonstrating potential applications in biosensing, cell imaging, diagnostics, and therapeutics. Preparation and exfoliation of 2D TMDs play an important part in these various applications as their properties are heavily dependent on the number of layers and lateral size. Described in this article are protocols for the liquid exfoliation of 2D TMDs from their bulk materials. Additional protocols are also provided for functionalizing or modifying the surface of the exfoliated 2D TMDs. © 2016 by John Wiley & Sons, Inc.

  2. Structural variations in layered alkaline earth metal cyclohexyl phosphonates

    Indian Academy of Sciences (India)

    Ramaswamy Murugavel; Nayanmoni Gogoi

    2009-06-01

    Two series of alkaline earth metal cyclohexyl phosphonates, M(C6H11PO3H)2(H2O) (M = Ca, Sr and Ba) (1–3) and M(C6H11PO3)(H2O) (M = Mg, Ca, Sr, and Ba) (4–7) have been synthesized under mild reaction conditions. All new compounds have been characterized using elemental analysis, IR, TGA and powder X-ray diffraction techniques. The molecular structure of compound 2 determined using single crystal X-ray diffraction technique reveals a layered polymeric structure.

  3. Tunable magnetic resonance in double layered metallic structures.

    Science.gov (United States)

    Zhou, L; Zhu, Y Y

    2011-12-01

    Double layered metallic gratings have been investigated both theoretically and experimentally. The authors have reported that tunable magnetic resonance (MR) can be achieved by modulating the vertical chirped width dh which could be controlled conveniently in the common electron and/or ion beam microfabrications. The linear relationship between MR wavelength and dh has been reported. By introducing the difference of electric and magnetic penetration depth, an analytic formula deduced from a modified LC model has shown good agreement with the simulation results, and an effective width for trapezoidal sandwiched microstructures has been presented. Our results may provide an alternative choice for tunable MR and broad bandwidth of magnetic metamaterials.

  4. Signatures of Quantized Energy States in Solution-Processed Ultrathin Layers of Metal-Oxide Semiconductors and Their Devices

    KAUST Repository

    Labram, John G.

    2015-02-13

    Physical phenomena such as energy quantization have to-date been overlooked in solution-processed inorganic semiconducting layers, owing to heterogeneity in layer thickness uniformity unlike some of their vacuum-deposited counterparts. Recent reports of the growth of uniform, ultrathin (<5 nm) metal-oxide semiconductors from solution, however, have potentially opened the door to such phenomena manifesting themselves. Here, a theoretical framework is developed for energy quantization in inorganic semiconductor layers with appreciable surface roughness, as compared to the mean layer thickness, and present experimental evidence of the existence of quantized energy states in spin-cast layers of zinc oxide (ZnO). As-grown ZnO layers are found to be remarkably continuous and uniform with controllable thicknesses in the range 2-24 nm and exhibit a characteristic widening of the energy bandgap with reducing thickness in agreement with theoretical predictions. Using sequentially spin-cast layers of ZnO as the bulk semiconductor and quantum well materials, and gallium oxide or organic self-assembled monolayers as the barrier materials, two terminal electronic devices are demonstrated, the current-voltage characteristics of which resemble closely those of double-barrier resonant-tunneling diodes. As-fabricated all-oxide/hybrid devices exhibit a characteristic negative-differential conductance region with peak-to-valley ratios in the range 2-7.

  5. Intermediate type excitons in Schottky barriers of A3B6 layer semiconductors and UV photodetectors

    Science.gov (United States)

    Alekperov, O. Z.; Guseinov, N. M.; Nadjafov, A. I.

    2006-09-01

    Photoelectric and photovoltaic spectra of Schottky barrier (SB) structures of InSe, GaSe and GaS layered semiconductors (LS) are investigated at quantum energies from the band edge excitons of corresponding materials up to 6.5eV. Spectral dependences of photoconductivity (PC) of photo resistors and barrier structures are strongly different at the quantum energies corresponding to the intermediate type excitons (ITE) observed in these semiconductors. It was suggested that high UV photoconductivity of A3B6 LS is due to existence of high mobility light carriers in the depth of the band structure. It is shown that SB of semitransparent Au-InSe is high sensitive photo detector in UV region of spectra.

  6. Unidirectional transmission in non-symmetric gratings containing metallic layers.

    Science.gov (United States)

    Serebryannikov, A E; Ozbay, Ekmel

    2009-08-03

    The mechanism of achieving unidirectional transmission in the gratings, which only contain isotropic dielectric and metallic layers, is suggested and numerically validated. It is shown that significant transmission in one direction and nearly zero transmission in the opposite direction can be obtained in the same intrinsically isotropic gratings as those studied recently in A. E. Serebryannikov and E. Ozbay, Opt. Express 17, 278 (2009), but at a non-zero angle of incidence. The tilting, non-symmetric features of the grating and the presence of a metallic layer with a small positive real part of the index of refraction are the conditions that are necessary for obtaining the unidirectionality. Single- and multibeam operational regimes are demonstrated. The frequency and angle ranges of the unidirectional transmission can be estimated by using the conventional framework based on isofrequency dispersion contours and construction lines that properly take into account the periodic features of the interfaces, but should then be corrected because of the tunneling arising within the adjacent ranges. After proper optimization, this mechanism is expected to become an alternative to that based on the use of anisotropic materials.

  7. TOPICAL REVIEW Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors

    Directory of Open Access Journals (Sweden)

    Tadashi C Ozawa et al

    2008-01-01

    Full Text Available Layered d-metal pnictide oxides are a unique class of compounds which consist of characteristic d-metal pnictide layers and metal oxide layers. More than 100 of these layered compounds, including the recently discovered Fe-based superconducting pnictide oxides, can be classified into nine structure types. These structure types and the chemical and physical properties of the characteristic d-metal pnictide layers and metal oxide layers of the layered d-metal pnictide oxides are reviewed and discussed. Furthermore, possible approaches to design new superconductors based on these layered d-metal pnictide oxides are proposed.

  8. Heavy metal uptake and leaching from polluted soil using permeable barrier in DTPA-assisted phytoextraction.

    Science.gov (United States)

    Zhao, Shulan; Shen, Zhiping; Duo, Lian

    2015-04-01

    Application of sewage sludge (SS) in agriculture is an alternative technique of disposing this waste. But unreasonable application of SS leads to excessive accumulation of heavy metals in soils. A column experiment was conducted to test the availability of heavy metals to Lolium perenne grown in SS-treated soils following diethylene triamine penta acetic acid (DTPA) application at rates of 0, 10 and 20 mmol kg(-1) soil. In order to prevent metal leaching in DTPA-assisted phytoextraction process, a horizontal permeable barrier was placed below the treated soil, and its effectiveness was also assessed. Results showed that DTPA addition significantly increased metal uptake by L. perenne shoots and metal leaching. Permeable barriers increased metal concentrations in plant shoots and effectively decreased metal leaching from the treated soil. Heavy metals in SS-treated soils could be gradually removed by harvesting L. perenne many times in 1 year and adding low dosage of DTPA days before each harvest.

  9. Laser ion acceleration from a double-layer metal foil

    Energy Technology Data Exchange (ETDEWEB)

    Lecz, Zsolt

    2013-11-12

    The laser-ion acceleration with ultra-intense and ultra-short laser pulses has opened a new field of accelerator physics over the last decade. Fast development in laser systems are capable of delivering short pulses of a duration of a few hundred femtoseconds at intensities between 10{sup 18}-10{sup 20} W/cm{sup 2}. At these high intensities the laser-matter interaction induces strong charge separation, which leads to electric fields exceeding the acceleration gradients of conventional devices by 6 orders of magnitude. The particle dynamics and energy absorption of the laser pulse can be understood by means of high-performance simulation tools. In the framework of the LIGHT (Laser Ion Generation, Handling and Transport) project our goal is to provide an analytical description of the 3D distribution of the protons accelerated via TNSA (Target Normal Sheath Acceleration). In this acceleration mechanism the short pulse impinging on a metal foil heats the electrons to relativistic energies, which triggers the strong charge separation field on the opposite target surface (Debye-sheath). The accelerated light ions (proton, carbon, oxygen) observed in the experiments originate from the contamination layer deposited on the surface. The thickness of this layer in the experiments is not known exactly. According to our study these ions can be accelerated in three different regimes depending on layer thickness: quasi-static acceleration (QSA, for thin layers), plasma expansion (for thick layers) and a not well understood intermediate (or combined) regime. In a laser-plasma simulations time-dependent hot electron density and temperature are observed, therefore we performed plasma simulations with a well defined and constant initial hot electron distribution. Thus the simulation results are easier to compare with analytical models. In our case the theoretical investigation of the TNSA involves the understanding of the charge separation effects at the surface of a two

  10. Microstructures of YBa2Cu3Oy Layers Deposited on Conductive Layer-Buffered Metal Tapes

    Science.gov (United States)

    Ichinose, Ataru; Hashimoto, Masayuki; Horii, Shigeru; Doi, Toshiya

    REBa2Cu3Oy (REBCO; RE: rare-earth elements)-coated conductors (CCs) have high potential for use in superconducting devices. In particular, REBCO CCs are useful for superconducting devices working at relatively high temperatures near 77 K. The important issues in their applications are high performance, reliability and low cost. To date, sufficient performance for some applications has almost been achieved by considerable efforts. The establishment of the reliability of superconducting devices is under way at present. The issue of low cost must be resolved to realize the application of superconducting devices in the near future. Therefore, we have attempted several ways to reduce the cost of REBCO CCs. The coated conductors using a Nb-doped SrTiO3 buffer layer and Ni-plated Cu and stainless steel laminate metal tapes have recently been developed to eliminate the use of electric stabilization layers of Cu and Ag, which are expected to reduce the material cost. Good superconducting properties are obtained at 77 K. The critical current density (JC) at 77 K under a magnetic self-field is determined to be more than 2x106 A/cm2. The microstructures of the CCs are analyzed by transmission electron microscopy to obtain a much higher quality. By microscopic structure analysis, an overgrowth of the buffer layer is observed at a grain boundary of the metal substrate, which is one of the reasons for the high JC.

  11. Factors of the accumulation of heavy metals and metalloids at geochemical barriers in urban soils

    Science.gov (United States)

    Kosheleva, N. E.; Kasimov, N. S.; Vlasov, D. V.

    2015-05-01

    The bulk contents and concentrations of mobile (extracted by an ammonium acetate buffer with EDTA) Cd, Pb, Sb, As, Bi, Zn, and Cu were determined in the surface horizons of urban soils in the Eastern administrative okrug of Moscow. The regression analysis showed that the accumulation of these metals and metalloids in the soils is controlled by the physicochemical soil properties and by number of anthropogenic factors and landscape conditions (geochemical position, type of loose deposits, character of land use, dust load, vehicle emissions, building pattern, percent of green areas, and the extent of sealed soils). The precipitation of studied elements on the geochemical barriers had the following regularities: Cd, Cu, and Zn accumulated on the alkaline barriers; Bi, Sb, As, Cu, Pb, and Zn, on chemisorption barriers; Sb, As, and Pb, on organomineral barriers; and Cd and Cu, on the sorption-sedimentation barriers. Technogenic transformation of the physicochemical properties of urban soils resulted in the increase of the mean bulk contents of heavy metals and metalloids by 33-99%; the portion of elements fixed on the geochemical barriers increased by 26-50%.

  12. Dielectric barrier discharge ionization in characterization of organic compounds separated on thin-layer chromatography plates.

    Science.gov (United States)

    Cegłowski, Michał; Smoluch, Marek; Babij, Michał; Gotszalk, Teodor; Silberring, Jerzy; Schroeder, Grzegorz

    2014-01-01

    A new method for on-spot detection and characterization of organic compounds resolved on thin layer chromatography (TLC) plates has been proposed. This method combines TLC with dielectric barrier discharge ionization (DBDI), which produces stable low-temperature plasma. At first, the compounds were separated on TLC plates and then their mass spectra were directly obtained with no additional sample preparation. To obtain good quality spectra the center of a particular TLC spot was heated from the bottom to increase volatility of the compound. MS/MS analyses were also performed to additionally characterize all analytes. The detection limit of proposed method was estimated to be 100 ng/spot of compound.

  13. Impermeable flexible liquid barrier film for encapsulation of DSSC metal electrodes

    Science.gov (United States)

    Yang, Junghee; Min, Misook; Yoon, Yeoheung; Kim, Won Jung; Kim, Sol; Lee, Hyoyoung

    2016-06-01

    Encapsulation of electronic devices such as dye-sensitized solar cells (DSSCs) is prone to degradation under normal atmospheric conditions, even with hermetic barriers on the metal electrodes. Overcoming this problem is crucial to increasing DSSC lifetimes and making them commercially viable. Herein, we report a new impermeable flexible liquid barrier film using polyvinyl alcohol (PVA) and partially reduced graphene oxide (PrGO), which dramatically enhances the lifetime of Ag metal electrodes (typically used in DSSCs) immersed in a highly acidic iodolyte solution. The Ag metal electrode encapsulated by the PVA/PrGO film survived for over 500 hrs, superior to existing barriers of glass frits, epoxy resins and polymers. The PVA/PrGO film strongly adheres to the Ag metal surface, and the resulting PVA/PrGO/Ag electrode is stable even on a curved substrate, with a sheet resistance nearly independent of curvature. These results give new insight for the design of high-performance and solution-processable flexible liquid barrier films for a wide range of applications, in particular for the encapsulation of electronic devices with liquid electrolytes.

  14. Impermeable flexible liquid barrier film for encapsulation of DSSC metal electrodes.

    Science.gov (United States)

    Yang, Junghee; Min, Misook; Yoon, Yeoheung; Kim, Won Jung; Kim, Sol; Lee, Hyoyoung

    2016-06-06

    Encapsulation of electronic devices such as dye-sensitized solar cells (DSSCs) is prone to degradation under normal atmospheric conditions, even with hermetic barriers on the metal electrodes. Overcoming this problem is crucial to increasing DSSC lifetimes and making them commercially viable. Herein, we report a new impermeable flexible liquid barrier film using polyvinyl alcohol (PVA) and partially reduced graphene oxide (PrGO), which dramatically enhances the lifetime of Ag metal electrodes (typically used in DSSCs) immersed in a highly acidic iodolyte solution. The Ag metal electrode encapsulated by the PVA/PrGO film survived for over 500 hrs, superior to existing barriers of glass frits, epoxy resins and polymers. The PVA/PrGO film strongly adheres to the Ag metal surface, and the resulting PVA/PrGO/Ag electrode is stable even on a curved substrate, with a sheet resistance nearly independent of curvature. These results give new insight for the design of high-performance and solution-processable flexible liquid barrier films for a wide range of applications, in particular for the encapsulation of electronic devices with liquid electrolytes.

  15. Effect of a multi-layer infection control barrier on the micro-hardness of a composite resin

    OpenAIRE

    In-Nam Hwang; Sung-Ok Hong; Bin-Na Lee; Yun-Chan Hwang; Won-Mann Oh; Hoon-Sang Chang

    2012-01-01

    OBJECTIVE: The aim of this study was to evaluate the effect of multiple layers of an infection control barrier on the micro-hardness of a composite resin. MATERIAL AND METHODS: One, two, four, and eight layers of an infection control barrier were used to cover the light guides of a high-power light emitting diode (LeD) light curing unit (LCU) and a low-power halogen LCU. The composite specimens were photopolymerized with the LCUs and the barriers, and the micro-hardness of the upper and lower...

  16. A three-terminal ultraviolet photodetector constructed on a barrier-modulated triple-layer architecture.

    Science.gov (United States)

    Ye, Daqian; Mei, Zengxia; Liang, Huili; Liu, Lishu; Zhang, Yonghui; Li, Junqiang; Liu, Yaoping; Gu, Changzhi; Du, Xiaolong

    2016-05-16

    We report a novel three-terminal device fabricated on MgZnO/ZnO/MgZnO triple-layer architecture. Because of the combined barrier modulation effect by both gate and drain biases, the device shows an unconventional I-V characteristics compared to a common field effect transistor. The photoresponse behavior of this unique device was also investigated and applied in constructing a new type ultraviolet (UV) photodetector, which may be potentially used as an active element in a UV imaging array. More significantly, the proper gate bias-control offers a new pathway to overcome the common persistent photoconductivity (PPC) effect problem. Additionally, the MgZnO:F as a channel layer was chosen to optimize the photoresponse properties, and the spectrum indicated a gate bias-dependent wavelength-selectable feature for different response peaks, which suggests the possibility to build a unique dual-band UV photodetector with this new architecture.

  17. Gas permeation barriers deposited by atmospheric pressure plasma enhanced atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Lukas, E-mail: lhoffmann@uni-wuppertal.de; Theirich, Detlef; Hasselmann, Tim; Räupke, André; Schlamm, Daniel; Riedl, Thomas, E-mail: t.riedl@uni-wuppertal.de [Institute of Electronic Devices, University of Wuppertal, Rainer-Gruenter-Str. 21, 42119 Wuppertal (Germany)

    2016-01-15

    This paper reports on aluminum oxide (Al{sub 2}O{sub 3}) thin film gas permeation barriers fabricated by atmospheric pressure atomic layer deposition (APPALD) using trimethylaluminum and an Ar/O{sub 2} plasma at moderate temperatures of 80 °C in a flow reactor. The authors demonstrate the ALD growth characteristics of Al{sub 2}O{sub 3} films on silicon and indium tin oxide coated polyethylene terephthalate. The properties of the APPALD-grown layers (refractive index, density, etc.) are compared to that deposited by conventional thermal ALD at low pressures. The films films deposited at atmospheric pressure show water vapor transmission rates as low as 5 × 10{sup −5} gm{sup −2}d{sup −1}.

  18. Schottky barrier height in metal-SiC contact - new approach to modelling

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, P.A.; Ignat`ev, K.I. [Ioffe Physico-Technical Inst., St. Petersburg (Russian Federation)

    1998-08-01

    A new approach to calculate Schottky barrier height in a metal-SiC contact is proposed proceeding from uniform spatial distribution of electron traps within metal-to-SiC gap represented by native oxide. The model explains well experimental data on metal-6H-SiC contacts, with comparatively low mid-gap surface state density. This is in contrast with widely used analytical model by Cowley and Sze providing high interface state density at the 6H-SiC mid-gap. (orig.) 5 refs.

  19. Glomerular endothelial surface layer acts as a barrier against albumin filtration.

    Science.gov (United States)

    Dane, Martijn J C; van den Berg, Bernard M; Avramut, M Cristina; Faas, Frank G A; van der Vlag, Johan; Rops, Angelique L W M M; Ravelli, Raimond B G; Koster, Bram J; van Zonneveld, Anton Jan; Vink, Hans; Rabelink, Ton J

    2013-05-01

    Glomerular endothelium is highly fenestrated, and its contribution to glomerular barrier function is the subject of debate. In recent years, a polysaccharide-rich endothelial surface layer (ESL) has been postulated to act as a filtration barrier for large molecules, such as albumin. To test this hypothesis, we disturbed the ESL in C57Bl/6 mice using long-term hyaluronidase infusion for 4 weeks and monitored albumin passage using immunolabeling and correlative light-electron microscopy that allows for complete and integral assessment of glomerular albumin passage. ESL ultrastructure was visualized by transmission electron microscopy using cupromeronic blue and by localization of ESL binding lectins using confocal microscopy. We demonstrate that glomerular fenestrae are filled with dense negatively charged polysaccharide structures that are largely removed in the presence of circulating hyaluronidase, leaving the polysaccharide surfaces of other glomerular cells intact. Both retention of native ferritin [corrected] in the glomerular basement membrane and systemic blood pressure were unaltered. Enzyme treatment, however, induced albumin passage across the endothelium in 90% of glomeruli, whereas this could not be observed in controls. Yet, there was no net albuminuria due to binding and uptake of filtered albumin by the podocytes and parietal epithelium. ESL structure and function completely recovered within 4 weeks on cessation of hyaluronidase infusion. Thus, the polyanionic ESL component, hyaluronan, is a key component of the glomerular endothelial protein permeability barrier.

  20. Modification of metal–InGaAs Schottky barrier behaviour by atomic layer deposition of ultra-thin Al{sub 2}O{sub 3} interlayers

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Lalit [School of Physical Sciences, Dublin City University, Dublin 9 (Ireland); Gupta, Suman; Jaiswal, Piyush; Bhat, Navakanta; Shivashankar, S.A. [Centre for Nano Science and Engineering (CeNSE), Indian Institute of Science, Bangalore 560012 (India); Hughes, G. [School of Physical Sciences, Dublin City University, Dublin 9 (Ireland)

    2015-08-31

    The effect of inserting ultra-thin atomic layer deposited Al{sub 2}O{sub 3} dielectric layers (1 nm and 2 nm thick) on the Schottky barrier behaviour for high (Pt) and low (Al) work function metals on n- and p-doped InGaAs substrates has been investigated. Rectifying behaviour was observed for the p-type substrates (both native oxide and sulphur passivated) for both the Al/p-InGaAs and Al/Al{sub 2}O{sub 3}/p-InGaAs contacts. The Pt contacts directly deposited on p-InGaAs displayed evidence of limited rectification which increased with Al{sub 2}O{sub 3} interlayer thickness. Ohmic contacts were formed for both metals on n-InGaAs in the absence of an Al{sub 2}O{sub 3} interlayer, regardless of surface passivation. However, limited rectifying behaviour was observed for both metals on the 2 nm Al{sub 2}O{sub 3}/n-InGaAs samples for the sulphur passivated InGaAs surface, indicating the importance of both surface passivation and the presence of an ultra-thin dielectric interlayer on the current–voltage characteristics displayed by these devices. - Highlights: • Investigation of the modification of metal–InGaAs Schottky barrier (SB) behaviour • Improving metal–InGaAs interface by sulphur passivation and ultrathin interlayer • Examine the effect of low work function and high work function metals on SB • Different SB behaviours observed on both n-type InGaAs and p-type InGaAs • Metal/n-InGaAs interface is more strongly pinned than the metal/p-InGaAs interface.

  1. Influence of Ni Catalyst Layer and TiN Diffusion Barrier on Carbon Nanotube Growth Rate

    Directory of Open Access Journals (Sweden)

    Mérel Philippe

    2010-01-01

    Full Text Available Abstract Dense, vertically aligned multiwall carbon nanotubes were synthesized on TiN electrode layers for infrared sensing applications. Microwave plasma-enhanced chemical vapor deposition and Ni catalyst were used for the nanotubes synthesis. The resultant nanotubes were characterized by SEM, AFM, and TEM. Since the length of the nanotubes influences sensor characteristics, we study in details the effects of changing Ni and TiN thickness on the physical properties of the nanotubes. In this paper, we report the observation of a threshold Ni thickness of about 4 nm, when the average CNT growth rate switches from an increasing to a decreasing function of increasing Ni thickness, for a process temperature of 700°C. This behavior is likely related to a transition in the growth mode from a predominantly “base growth” to that of a “tip growth.” For Ni layer greater than 9 nm the growth rate, as well as the CNT diameter, variations become insignificant. We have also observed that a TiN barrier layer appears to favor the growth of thinner CNTs compared to a SiO2 layer.

  2. Effectiveness of compacted soil liner as a gas barrier layer in the landfill final cover system.

    Science.gov (United States)

    Moon, Seheum; Nam, Kyoungphile; Kim, Jae Young; Hwan, Shim Kyu; Chung, Moonkyung

    2008-01-01

    A compacted soil liner (CSL) has been widely used as a single barrier layer or a part of composite barrier layer in the landfill final cover system to prevent water infiltration into solid wastes for its acceptable hydraulic permeability. This study was conducted to test whether the CSL was also effective in prohibiting landfill gas emissions. For this purpose, three different compaction methods (i.e., reduced, standard, and modified Proctor methods) were used to prepare the soil specimens, with nitrogen as gas, and with water and heptane as liquid permeants. Measured gas permeability ranged from 2.03 x 10(-10) to 4.96 x 10(-9) cm(2), which was a magnitude of two or three orders greater than hydraulic permeability (9.60 x 10(-13) to 1.05 x 10(-11) cm(2)). The difference between gas and hydraulic permeabilities can be explained by gas slippage, which makes gas more permeable, and by soil-water interaction, which impedes water flow and then makes water less permeable. This explanation was also supported by the result that a liquid permeability measured with heptane as a non-polar liquid was similar to the intrinsic gas permeability. The data demonstrate that hydraulic requirement for the CSL is not enough to control the gas emissions from a landfill.

  3. Barrier properties of hydrogenated acrylonitrile-butadiene rubber composites containing modified layered aluminosilicates

    Science.gov (United States)

    Krzemińska, S.; Rzymski, W. M.

    2011-12-01

    The resistance to permeation by the selected solvents of flat membranes made of cured hydrogenated acrylonitrile-butadiene rubber (HNBR) materials without any fillers and containing 5 phr of layered aluminosilicate nanofiller (bentonite), modified with various types of ammonium salts or N330 type carbon black, was investigated. The barrier properties were assessed on the basis of the breakthrough time of a liquid with low (cyclohexane) or average (butyl acetate) thermodynamic affinity to HNBR, determined according to EN 6529:2001, through a cured elastomer sample. The addition of bentonite, irrespectively of the method of modification of its particles, was found to increase the cured HNBR breakthrough time by 20 - 35 % in the case of slowly permeating non-polar cyclohexane, and by 50 - 130 % in the case of polar butyl acetate permeating more rapidly, in comparison with the barrier material containing no filler. The layered aluminosilicate nanofillers increased the breakthrough time of the material sample for both the tested solvents. In particular, the breakthrough time for polar butyl acetate was even longer than for conventional carbon black. Additionally, the increase of the breakthrough time was observed to depend on the modifier of bentonite particle surface.

  4. The role of oxygen in the deposition of copper-calcium thin film as diffusion barrier for copper metallization

    Science.gov (United States)

    Yu, Zhinong; Ren, Ruihuang; Xue, Jianshe; Yao, Qi; Li, Zhengliang; Hui, Guanbao; Xue, Wei

    2015-02-01

    The properties of copper (Cu) metallization based on copper-calcium (CuCa) diffusion barrier as a function of oxygen flux in the CuCa film deposition were investigated in view of adhesion, diffusion and electronic properties. The CuCa film as the diffusion barrier of Cu film improves the adhesion of Cu film, however, and increases the resistance of Cu film. The introduction of oxygen into the deposition of CuCa film induces the improvement of adhesion and crystallinity of Cu film, but produces a slight increase of resistance. The increased resistance results from the partial oxidation of Cu film. The annealing process in vacuum further improves the adhesion, crystallinity and conductivity of Cu film. X-ray diffraction (XRD) and Auger electron spectroscopy (AES) show that the CuCa alloy barrier layer deposited at oxygen atmosphere has perfect anti-diffusion between Cu film and substrate due to the formation of Ca oxide in the interface of CuCa/substrate.

  5. Efficiency enhancement of solid-state PbS quantum dot-sensitized solar cells with Al2O3 barrier layer

    KAUST Repository

    Brennan, Thomas P.

    2013-01-01

    Atomic layer deposition (ALD) was used to grow both PbS quantum dots and Al2O3 barrier layers in a solid-state quantum dot-sensitized solar cell (QDSSC). Barrier layers grown prior to quantum dots resulted in a near-doubling of device efficiency (0.30% to 0.57%) whereas barrier layers grown after quantum dots did not improve efficiency, indicating the importance of quantum dots in recombination processes. © 2013 The Royal Society of Chemistry.

  6. Method for producing functionally graded nanocrystalline layer on metal surface

    Science.gov (United States)

    Ajayi, Oyelayo O.; Hershberger, Jeffrey G.

    2010-03-23

    An improved process for the creation or formation of nanocrystalline layers on substrates' surfaces is provided. The process involves "prescuffing" the surface of a substrate such as a metal by allowing friction to occur on the surface by a load-bearing entity making rubbing contact and moving along and on the substrate's surface. The "prescuffing" action is terminated when the coefficient of friction between the surface and the noise is rising significantly. Often, the significant rise in the coefficient of friction is signaled by a change in pitch of the scuffing action sound emanating from the buffeted surface. The "prescuffing" gives rise to a harder and smoother surface which withstands better any inadequate lubrication that may take place when the "prescuffed" surface is contacted by other surfaces.

  7. Investigation of a double barrier resonant tunnelling structure which incorporates an optical window layer in the top contact

    Energy Technology Data Exchange (ETDEWEB)

    Henini, M.; Eaves, L.; Maude, D.K.; Hughes, O.H. (Dept. of Physics, Univ. of Nottingham (UK)); White, C.R.H. (Dept. of Physics, Univ. of Nottingham (UK) RSRE, Great Malvern (UK)); Simmonds, P.E. (Royal Signals and Radar Establishment, Great Malvern (UK) Dept. of Physics, Univ. of Nottingham (UK)); Skolnick, M.S. (Royal Signals and Radar Establishment, Great Malvern (UK)); Portal, J.C. (SNCI-CNRS, 38 - Grenoble (France) LPS-INSA, 31 - Toulouse (France))

    1991-05-01

    The electrical and optical properties of a double barrier resonant tunnelling device based on n-GaAs/(AlGa)As and incorporating a heavily doped (AlGa)As window layer are described. The window layer is located between the quantum well and the top surface and has a band gap which exceeds the energy of the quantum well photoluminescence. The incorporation of this layer does not impair the electrical properties of the device. (orig.).

  8. Effect of a multi-layer infection control barrier on the micro-hardness of a composite resin

    Directory of Open Access Journals (Sweden)

    In-Nam Hwang

    2012-10-01

    Full Text Available OBJECTIVE: The aim of this study was to evaluate the effect of multiple layers of an infection control barrier on the micro-hardness of a composite resin. MATERIAL AND METHODS: One, two, four, and eight layers of an infection control barrier were used to cover the light guides of a high-power light emitting diode (LeD light curing unit (LCU and a low-power halogen LCU. The composite specimens were photopolymerized with the LCUs and the barriers, and the micro-hardness of the upper and lower surfaces was measured (n=10. The hardness ratio was calculated by dividing the bottom surface hardness of the experimental groups by the irradiated surface hardness of the control groups. The data was analyzed by two-way ANOVA and Tukey's HSD test. RESULTS: The micro-hardness of the composite specimens photopolymerized with the LED LCU decreased significantly in the four- and eight-layer groups of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. The hardness ratio of the composite specimens was <80% in the eight-layer group. The micro-hardness of the composite specimens photopolymerized with the halogen LCU decreased significantly in the eight-layer group of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. However, the hardness ratios of all the composite specimens photopolymerized with barriers were <80%. CONCLUSIONS: The two-layer infection control barrier could be used on high-power LCUs without decreasing the surface hardness of the composite resin. However, when using an infection control barrier on the low-power LCUs, attention should be paid so as not to sacrifice the polymerization efficiency.

  9. Blood-brain barrier flux of aluminum, manganese, iron and other metals suspected to contribute to metal-induced neurodegeneration.

    Science.gov (United States)

    Yokel, Robert A

    2006-11-01

    The etiology of many neurodegenerative diseases has been only partly attributed to acquired traits, suggesting environmental factors may also contribute. Metal dyshomeostasis causes or has been implicated in many neurodegenerative diseases. Metal flux across the blood-brain barrier (the primary route of brain metal uptake) and the choroid plexuses as well as sensory nerve metal uptake from the nasal cavity are reviewed. Transporters that have been described at the blood-brain barrier are listed to illustrate the extensive possibilities for moving substances into and out of the brain. The controversial role of aluminum in Alzheimer's disease, evidence suggesting brain aluminum uptake by transferrin-receptor mediated endocytosis and of aluminum citrate by system Xc;{-} and an organic anion transporter, and results suggesting transporter-mediated aluminum brain efflux are reviewed. The ability of manganese to produce a parkinsonism-like syndrome, evidence suggesting manganese uptake by transferrin- and non-transferrin-dependent mechanisms which may include store-operated calcium channels, and the lack of transporter-mediated manganese brain efflux, are discussed. The evidence for transferrin-dependent and independent mechanisms of brain iron uptake is presented. The copper transporters, ATP7A and ATP7B, and their roles in Menkes and Wilson's diseases, are summarized. Brain zinc uptake is facilitated by L- and D-histidine, but a transporter, if involved, has not been identified. Brain lead uptake may involve a non-energy-dependent process, store-operated calcium channels, and/or an ATP-dependent calcium pump. Methyl mercury can form a complex with L-cysteine that mimics methionine, enabling its transport by the L system. The putative roles of zinc transporters, ZnT and Zip, in regulating brain zinc are discussed. Although brain uptake mechanisms for some metals have been identified, metal efflux from the brain has received little attention, preventing integration of

  10. Finite Element Analysis of Thermal Stresses in Ceramic/Metal Gradient Thermal Barrier Coatings

    Institute of Scientific and Technical Information of China (English)

    MING Pingshun; XIAO Jinsheng; LIU Jie; ZHOU Xiaoqin

    2005-01-01

    This paper studied the thermal stresses of ceramic/metal gradient thermal barrier coating which combines the conceptions of ceramic thermal barrier coating (TBC) and functionally gradient material (FGM). Thermal stresses and residual thermal stresses were calculated by an ANSYS finite element analysis software. Negative thermal expansion coefficient method was proposed and element birth and death method was applied to analyze the residual thermal stresses which have non-uniform initial temperature field. The numerical results show a good agreement with the analytical results and the experimental results.

  11. Silver-doped metal layers for medical applications

    Science.gov (United States)

    Kocourek, T.; Jelínek, M.; Mikšovský, J.; Jurek, K.; Weiserová, M.

    2014-08-01

    Biological, physical and mechanical properties of silver-doped layers of titanium alloy Ti6Al4V and 316 L steel prepared by pulsed laser deposition were studied. Metallic silver-doped coatings could be a new route for antibacterial protection in medicine. Thin films of silver and silver-doped materials were synthesized using KrF excimer laser deposition. The materials were ablated from two targets, which were composed either from titanium alloy with silver segments or from steel with silver segments. The concentration of silver ranged from 1.54 to 4.32 at% for steel and from 3.04 to 13.05 at% for titanium alloy. The layer properties such as silver content, structure, adhesion, surface wettability, and antibacterial efficiency (evaluated by Escherichia coli and Bacillus subtilis bacteria) were measured. Film adhesion was studied using a scratch test. The antibacterial efficiency changed with silver doping up to 99.9 %. Our investigation was focused on the minimum Ag concentration needed to reach high antibacterial efficiency, high film adhesion, and hardness.

  12. Thermal Decomposition Studies of Layered Metal Hydroxynitrates (Metal: Cu, Zn, Cu/Co, and Zn/Co

    Directory of Open Access Journals (Sweden)

    Thimmasandra Narayan Ramesh

    2015-01-01

    Full Text Available Layered metal hydroxynitrates and mixed metal hydroxynitrates (copper/cobalt hydroxynitrates and zinc/cobalt hydroxynitrates at different mole ratios were synthesized by hydrolysis of urea and metal nitrates at 140°C. Layered metal hydroxyl nitrates derive their structure from brucite mineral and generally crystallize in hexagonal and monoclinic phases. Isothermal decomposition studies of Cu2(OH3(NO3, Co2(OH3(NO3, Cu1.5Co0.5(OH3(NO3, Cu1.34Co0.66(OH3(NO3, Zn5(OH8(NO32(H2O2, Zn3.75Co1.25(OH8(NO32(H2O2, and Zn3.35Co1.65(OH8(NO32(H2O2 samples were carried out at different intervals of temperature and the structural transformations during the process were monitored using powder X-ray diffractograms. Biphasic mixture of metal hydroxynitrate/metal oxide is observed in case of cobalt/zinc based layered hydroxynitrates, while copper hydroxynitrate or copper/cobalt metal hydroxynitrate decomposes in a single step. The decomposition temperatures of layered metal hydroxynitrates and mixed layered metal hydroxides depend on the method of preparation, their composition and the nature of metal ion, and their coordination.

  13. Electronic self-organization in layered transition metal dichalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Ritschel, Tobias

    2015-10-30

    The interplay between different self-organized electronically ordered states and their relation to unconventional electronic properties like superconductivity constitutes one of the most exciting challenges of modern condensed matter physics. In the present thesis this issue is thoroughly investigated for the prototypical layered material 1T-TaS{sub 2} both experimentally and theoretically. At first the static charge density wave order in 1T-TaS{sub 2} is investigated as a function of pressure and temperature by means of X-ray diffraction. These data indeed reveal that the superconductivity in this material coexists with an inhomogeneous charge density wave on a macroscopic scale in real space. This result is fundamentally different from a previously proposed separation of superconducting and insulating regions in real space. Furthermore, the X-ray diffraction data uncover the important role of interlayer correlations in 1T-TaS{sub 2}. Based on the detailed insights into the charge density wave structure obtained by the X-ray diffraction experiments, density functional theory models are deduced in order to describe the electronic structure of 1T-TaS{sub 2} in the second part of this thesis. As opposed to most previous studies, these calculations take the three-dimensional character of the charge density wave into account. Indeed the electronic structure calculations uncover complex orbital textures, which are interwoven with the charge density wave order and cause dramatic differences in the electronic structure depending on the alignment of the orbitals between neighboring layers. Furthermore, it is demonstrated that these orbital-mediated effects provide a route to drive semiconductor-to-metal transitions with technologically pertinent gaps and on ultrafast timescales. These results are particularly relevant for the ongoing development of novel, miniaturized and ultrafast devices based on layered transition metal dichalcogenides. The discovery of orbital textures

  14. Effects of NH3 Flow Rate During AlGaN Barrier Layer Growth on the Material Properties of AlGaN/GaN HEMT Heterostructure

    Science.gov (United States)

    Lumbantoruan, Franky J.; Wong, Yuen-Yee; Huang, Wei-Ching; Yu, Hung-Wei; Chang, Edward-Yi

    2017-10-01

    NH3 flow rate during AlGaN barrier layer growth not only affects the growth efficiency and surface morphology as a result of parasitic reactions but also influences the concentration of carbon impurity in the AlGaN barrier. Carbon, which decomposes from metal precursors, plays a role in electron compensation for AlGaN/GaN HEMT. No 2-dimensional electron gas (2-DEG) was detected in the AlGaN/GaN structure if grown with 0.5 slm of NH3 due to the presence of higher carbon impurity (2.6 × 1019 cm-2). When the NH3 flow rate increased to 6.0 slm, the carbon impurity reduced to 2.10 × 1018 atom cm-3 and the 2 DEG electron density recovered to 9.57 × 1012 cm-2.

  15. Effect of Al 2 O 3 Recombination Barrier Layers Deposited by Atomic Layer Deposition in Solid-State CdS Quantum Dot-Sensitized Solar Cells

    KAUST Repository

    Roelofs, Katherine E.

    2013-03-21

    Despite the promise of quantum dots (QDs) as a light-absorbing material to replace the dye in dye-sensitized solar cells, quantum dot-sensitized solar cell (QDSSC) efficiencies remain low, due in part to high rates of recombination. In this article, we demonstrate that ultrathin recombination barrier layers of Al2O3 deposited by atomic layer deposition can improve the performance of cadmium sulfide (CdS) quantum dot-sensitized solar cells with spiro-OMeTAD as the solid-state hole transport material. We explored depositing the Al2O3 barrier layers either before or after the QDs, resulting in TiO2/Al2O3/QD and TiO 2/QD/Al2O3 configurations. The effects of barrier layer configuration and thickness were tracked through current-voltage measurements of device performance and transient photovoltage measurements of electron lifetimes. The Al2O3 layers were found to suppress dark current and increase electron lifetimes with increasing Al 2O3 thickness in both configurations. For thin barrier layers, gains in open-circuit voltage and concomitant increases in efficiency were observed, although at greater thicknesses, losses in photocurrent caused net decreases in efficiency. A close comparison of the electron lifetimes in TiO2 in the TiO2/Al2O3/QD and TiO2/QD/Al2O3 configurations suggests that electron transfer from TiO2 to spiro-OMeTAD is a major source of recombination in ss-QDSSCs, though recombination of TiO2 electrons with oxidized QDs can also limit electron lifetimes, particularly if the regeneration of oxidized QDs is hindered by a too-thick coating of the barrier layer. © 2013 American Chemical Society.

  16. Spin-mixing conductances of metallic and half-metallic magnetic layers.

    Science.gov (United States)

    Turek, I; Carva, K

    2007-09-12

    The spin-mixing conductance of a thin ferromagnetic layer attached epitaxially to two semi-infinite non-magnetic metallic leads is formulated in terms of non-equilibrium Green's functions. The spin-mixing conductance is obtained as a response of the spin torque acting on the ferromagnet with respect to the spin accumulation in one of the leads, while the spin torque is defined as a time derivative of the spin magnetic moment. The equivalence of the derived formula with a previous expression of the Landauer-Büttiker scattering theory is sketched and an implementation within the ab initio tight-binding linear muffin-tin orbital method is briefly described. Applications are made for metallic Co- and Ni-based slabs embedded between Cu(111) leads and for half-metallic Co(2)MnSi films sandwiched by Cr(001) leads. The calculated results throw serious doubts on the general validity of two features: fast convergence of the spin-mixing conductance with increasing thickness of the magnetic layer and negligible values of the imaginary part of the spin-mixing conductance as compared to the real part.

  17. First-principles study of transition-metal nitrides as diffusion barriers against Al

    Energy Technology Data Exchange (ETDEWEB)

    Mei, Zhi-Gang, E-mail: zmei@anl.gov; Yacout, Abdellatif M.; Kim, Yeon Soo; Hofman, Gerard; Stan, Marius

    2016-04-01

    Using density-functional theory based first-principles calculations we provided a comparative study of the diffusion barrier properties of TiN, ZrN, and HfN against Al for U–Mo dispersion fuel applications. We firstly examined the thermodynamic stability of these transition-metal nitrides with Al. The calculated heats of reaction show that both TiN and ZrN are thermodynamically unstable diffusion barrier materials, which might be decomposed by Al at relatively high temperatures. As a comparison, HfN is a stable diffusion barrier material for Al. To evaluate the kinetic stability of these nitride systems against Al diffusion, we investigated the diffusion mechanisms of Al in TiN, ZrN and HfN using atomic scale simulations. The effect of non-stoichiometry on the defect formation and Al migration was systematically studied.

  18. Barrier layer in the northeastern South China Sea and its formation mechanism

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Robust evidence for the barrier layer (BL) in the northeastern South China Sea (SCS) (16°-25°N, 112°-124°E) is presented. The occurrence rate of the BL peaks in the autumn (45.7%) and then the summer (31.1%) and the spring (23.3%), sequently. It is estimated that the annual occurrence rate of the BL reaches about 40.0% in the central northeastern SCS (18°-22°N, 112°-120°E) and the Luzon Strait. Stratification-formed (Rain-formed) mechanism is the major factor responsible for the occurrence of the BL in the northeastern SCS in the spring (the summer and autumn), respectively. The rainfall observation from TRMM provides reliable evidence for the latter.

  19. Study on Stress Development in the Phase Transition Layer of Thermal Barrier Coatings

    Directory of Open Access Journals (Sweden)

    Yijun Chai

    2016-09-01

    Full Text Available Stress development is one of the significant factors leading to the failure of thermal barrier coating (TBC systems. In this work, stress development in the two phase mixed zone named phase transition layer (PTL, which grows between the thermally grown oxide (TGO and the bond coat (BC, is investigated by using two different homogenization models. A constitutive equation of the PTL based on the Reuss model is proposed to study the stresses in the PTL. The stresses computed with the proposed constitutive equation are compared with those obtained with Voigt model-based equation in detail. The stresses based on the Voigt model are slightly higher than those based on the Reuss model. Finally, a further study is carried out to explore the influence of phase transition proportions on the stress difference caused by homogenization models. Results show that the stress difference becomes more evident with the increase of the PTL thickness ratio in the TGO.

  20. A comparative study of IR Ge photodiodes with a Schottky barrier contact and metal-semiconductor-metal structure

    Energy Technology Data Exchange (ETDEWEB)

    Khurelbaatar, Zagarzusem; Kil, Yeonho; Lee, Hunki; Yang, Jonghan; Kang, Sukill; Kim, Taeksung; Shim, Kyuhwan [Chonbuk National University, Jeonju (Korea, Republic of)

    2014-12-15

    We report the characterization of germanium (Ge) infrared photodiodes fabricated with a Schottky barrier contact and a interdigitated metal-semiconductor-metal (MSM) structure with gold electrodes on n-Ge substrates. The current-volage (I-V) characteristics were studied, and parameters such as the ideality factor and the barrier height of the Schottky contacts were extracted. Furthemore, we estimated the dark current and the photocurrent under illumination with λ = 1550 nm light, and we measured the capacitance-voltage (C-V) characteristics and the dependence of the responsivity on the bias voltage of both photodiodes at room temperature. The dark currents of the Schottky and the MSM photodiodes were ∼ 20.2 μA and ∼ 26.0 μA under .1 V bias and .2 V bias, respectively. In addition, the reverse breakdown voltage was high, in excess of ∼ -30 V. The Schottky barrier height was deduced to be 0.546 eV. A maximum responsivity of 0.27 A/W was achieved under illumination with λ = 1550 nm light at a 2-V bias. A typical peak was observed at a wavelength of 1600 nm, and a high responsivity was observed in the wavelength range from 1200 to 1800 nm.

  1. Combining Nitrilotriacetic Acid and Permeable Barriers for Enhanced Phytoextraction of Heavy Metals from Municipal Solid Waste Compost by and Reduced Metal Leaching.

    Science.gov (United States)

    Zhao, Shulan; Jia, Lina; Duo, Lian

    2016-05-01

    Phytoextraction has the potential to remove heavy metals from contaminated soil, and chelants can be used to improve the capabilities of phytoextraction. However, environmentally persistent chelants can cause metal leaching and groundwater pollution. A column experiment was conducted to evaluate the viability of biodegradable nitrilotriacetic acid (NTA) to increase the uptake of heavy metals (Cd, Cr, Ni, Pb, Cu, and Zn) by L. in municipal solid waste (MSW) compost and to evaluate the effect of two permeable barrier materials, bone meal and crab shell, on metal leaching. The application of NTA significantly increased the concentrations and uptake of heavy metals in . The enhancement was more pronounced at higher dosages of NTA. In the 15 mmol kg NTA treatment using a crab shell barrier, the Cr and Ni concentrations in the plant shoots increased by approximately 8- and 10-fold, respectively, relative to the control. However, the addition of NTA also caused significant heavy metal leaching from the MSW compost. Bone meal and crab shell barriers positioned between the compost and the subsoil were effective in preventing metal leaching down through the soil profile by the retention of metals in the barrier. The application of a biodegradable chelant and the use of permeable barriers is a viable form of enhanced phytoextraction to increase the removal of metals and to reduce possible leaching.

  2. The effect of the carbon nanotube buffer layer on the performance of a Li metal battery

    Science.gov (United States)

    Zhang, Ding; Zhou, Yi; Liu, Changhong; Fan, Shoushan

    2016-05-01

    Lithium (Li) metal is one of the most promising candidates as an anode for the next-generation energy storage systems because of its high specific capacity and lowest negative electrochemical potential. But the growth of Li dendrites limits the application of the Li metal battery. In this work, a type of modified Li metal battery with a carbon nanotube (CNT) buffer layer inserted between the separator and the Li metal electrode was reported. The electrochemical results show that the modified batteries have a much better rate capability and cycling performance than the conventional Li metal batteries. The mechanism study by electrochemical impedance spectroscopy reveals that the modified battery has a smaller charge transfer resistance and larger Li ion diffusion coefficient during the deposition process on the Li electrode than the conventional Li metal batteries. Symmetric battery tests show that the interfacial behavior of the Li metal electrode with the buffer layer is more stable than the naked Li metal electrode. The morphological characterization of the CNT buffer layer and Li metal lamina reveals that the CNT buffer layer has restrained the growth of Li dendrites. The CNT buffer layer has great potential to solve the safety problem of the Li metal battery.Lithium (Li) metal is one of the most promising candidates as an anode for the next-generation energy storage systems because of its high specific capacity and lowest negative electrochemical potential. But the growth of Li dendrites limits the application of the Li metal battery. In this work, a type of modified Li metal battery with a carbon nanotube (CNT) buffer layer inserted between the separator and the Li metal electrode was reported. The electrochemical results show that the modified batteries have a much better rate capability and cycling performance than the conventional Li metal batteries. The mechanism study by electrochemical impedance spectroscopy reveals that the modified battery has a

  3. Simulation of Nanowires on Metal Vicinal Surfaces: Effect of Growth Parameters and Energetic Barriers

    Science.gov (United States)

    Hamouda, Ajmi B. H.; Blel, Sonia; Einstein, T. L.

    2012-02-01

    Growing one-dimensional metal structures is an important task in the investigation of the electronic and magnetic properties of new devices. We used kinetic Monte-Carlo (kMC) method to simulate the formation of nanowires of several metallic and non-metallic adatoms on Cu and Pt vicinal surfaces. We found that mono-atomic chains form on step-edges due to energetic barriers (the so-called Ehrlich-shwoebel and exchange barriers) on step-edge. Creation of perfect wires is found to depend on growth parameters and binding energies. We measure the filling ratio of nanowires for different chemical species in a wide range of temperature and flux. Perfect wires were obtained at lower deposition rate for all tested adatoms, however we notice different temperature ranges. Our results were compared with experimental ones [Gambardella et al., Surf. Sci.449, 93-103 (2000), PRB 61, 2254-2262, (2000)]. We review the role of impurities in nanostructuring of surfaces [Hamouda et al., Phys. Rev. B 83, 035423, (2011)] and discuss the effect of their energetic barriers on the obtained quality of nanowires. Our work provides experimentalists with optimum growth parameters for the creation of a uniform distribution of wires on surfaces.

  4. Growth and characterization of InGaN back barrier HEMTs structure with a compositionally step-graded AlGaN layer

    Institute of Scientific and Technical Information of China (English)

    Tang Jian; Wang Xiaoliang; Xiao Hongling

    2014-01-01

    A novel InGaN back barrier high electron mobility transistors structure with a compositionally stepgraded AlGaN barrier layer was grown by metal organic chemical vapor deposition on sapphire substrate.The structural and electrical properties of two samples were investigated and compared:the first sample is the stepgraded structure and the second one is the high Al structure as a comparison.By calculating full width at half maximum of XRD measurements,the densities of screw-type threading dislocations are 8.34 × 108 cm-2 and 11.44 × 108 cm-2 for step-graded structure and high Al structure,respectively,which are consistent with the results of atomic force microscopy.By Hall measurements,the measured two-dimensional electron gas mobility was 1820 cm2/(V·s) for step-graded structure,and 1300 cm2/(V·s) for high Al structure,respectively.The stepgraded structure improves the crystal quality of AlGaN layer due to the released lattice strain.The device was fabricated and leakage current is only 28μA when the drain voltage is 10 V; it was found that the InGaN back barrier could effectively reduce the buffer leakage current.

  5. Characterization of Ta-based barrier films on SiLK for Cu-metalization

    NARCIS (Netherlands)

    Bystrova, S.; Holleman, J.; Woerlee, P.H.; Wolters, R.A.M.

    2002-01-01

    Structures with Ta, TaxN1-x, Ta90C10, Ta95Si5 on SiLK were tested using in-situ 4- point probe resistance measurements during annealing up to 400oC. The change in normalized resistance by a factor of up to 2.58 was attributed to oxygen diffusion out of SiLK layer into the barriers. No direct chemica

  6. Lifetimes of organic photovoltaics: photochemistry, atmosphere effects and barrier layers in ITO-MEHPPV:PCBM-aluminium devices

    DEFF Research Database (Denmark)

    Krebs, Frederik C; Carlé, Jon Eggert; Cruys-Bagger, N.

    2005-01-01

    , mode of preparation and barrier layers by recording the short circuit current as a function of time. Two exponential fits to the decay curves allowed for the extraction of the time constants for different degradation processes. For the periods of time studied here (24-300 h), the decay curves could...... and depended on the presence of oxygen. By employing different barrier layers, we found the first half-life to be linked to the aluminium polymer interface and ascribe it to a photochemical reaction between the organic material and the reactive aluminium at the interface. The second and longer half...

  7. Grain Boundary Penetration of Various Types of Ni Layer by Molten Metals

    Science.gov (United States)

    Yang, S.; Chang, C. Y.; Zhu, Z. X.; Lin, Y. F.; Kao, C. R.

    2017-02-01

    The grain boundary penetration of three types of Ni layer, Ni foil, electroplated Ni, and electroless Ni, by molten Pb and 95Pb5Sn (wt.%) is investigated. The average grain sizes of Ni foil and electroplated Ni are 10 μm and 1 μm, respectively, while the electroless Ni is amorphous. The purpose of using two molten metals is to study the effect of intermetallic formation on grain boundary penetration. Molten Pb was able to penetrate or disintegrate all three types of Ni, including amorphous Ni, which does not contain any grain boundaries. On the other hand, the addition of merely 5 wt.% Sn into molten Pb was able to slow the penetration down substantially for all three types of Ni layer, with the greatest suppression found in electroless Ni where a grain boundary penetration event did not take place. The mechanism for the Sn effect is due to the formation of a protective Ni3Sn4 intermetallic compound at the interface acting as a barrier against grain boundary penetration.

  8. Investigation of metallic, ceramic, and polymeric materials for engineered barrier applications in nuclear-waste packages

    Energy Technology Data Exchange (ETDEWEB)

    Westerman, R.E.

    1980-10-01

    An effort to develop licensable engineered barrier systems for the long-term (about 1000 yr) containment of nuclear wastes under conditions of deep continental geologic disposal has been underway at Pacific Northwest Laboratory since January 1979, under the auspices of the High-Level Waste Immobilization Program. In the present work, the barrier system comprises the hard or structural elements of the package: the canister, the overpack(s), and the hole sleeve. A number of candidate metallic, ceramic, and polymeric materials were put through mechanical, corrosion, and leaching screening tests to determine their potential usefulness in barrier-system applications. Materials demonstrating adequate properties in the screening tests will be subjected to more detailed property tests, and, eventually, cost/benefit analyses, to determine their ultimate applicability to barrier-system design concepts. The following materials were investigated: two titanium alloys of Grade 2 and Grade 12; 300 and 400 series stainless steels, Inconels, Hastelloy C-276, titanium, Zircoloy, copper-nickel alloys and cast irons; total of 14 ceramic materials, including two grades of alumina, plus graphite and basalt; and polymers such as polyamide-imide, polyarylene, polyimide, polyolefin, polyphenylene sulfide, polysulfone, fluoropolymer, epoxy, furan, silicone, and ethylene-propylene terpolymer (EPDM) rubber. The most promising candidates for further study and potential use in engineered barrier systems were found to be rubber, filled polyphenylene sulfide, fluoropolymer, and furan derivatives.

  9. Spray coating of self-aligning passivation layer for metal grid lines

    NARCIS (Netherlands)

    Vuorinen, T.; Janka, M.; Rubingh, J.E.J.M.; Tuukkanen, S.; Groen, P.; Lupo, D.

    2014-01-01

    In applications such as organic light emitting diodes (OLEDs) or photovoltaic cells a homogenous voltage distribution in the large anode layer needs to be ensured by including a metal grid with a transparent conductor layer. To ensure sufficient conductivity, relatively thick metal lines are used, w

  10. Spray coating of self-aligning passivation layer for metal grid lines

    NARCIS (Netherlands)

    Vuorinen, T.; Janka, M.; Rubingh, J.E.J.M.; Tuukkanen, S.; Groen, P.; Lupo, D.

    2014-01-01

    In applications such as organic light emitting diodes (OLEDs) or photovoltaic cells a homogenous voltage distribution in the large anode layer needs to be ensured by including a metal grid with a transparent conductor layer. To ensure sufficient conductivity, relatively thick metal lines are used,

  11. New chemistry for the growth of first-row transition metal films by atomic layer deposition

    Science.gov (United States)

    Klesko, Joseph Peter

    Thin films containing first-row transition metals are widely used in microelectronic, photovoltaic, catalytic, and surface-coating applications. In particular, metallic films are essential for interconnects and seed, barrier, and capping layers in integrated circuitry. Traditional vapor deposition methods for film growth include PVD, CVD, or the use of plasma. However, these techniques lack the requisite precision for film growth at the nanoscale, and thus, are increasingly inadequate for many current and future applications. By contrast, ALD is the favored approach for depositing films with absolute surface conformality and thickness control on 3D architectures and in high aspect ratio features. However, the low-temperature chemical reduction of most first-row transition metal cations to their zero-valent state is very challenging due to their negative electrochemical potentials. A lack of strongly-reducing coreagents has rendered the thermal ALD of metallic films an intractable problem for many elements. Additionally, several established ALD processes for metal films are plagued by low growth rates, impurity incorporation, poor nucleation, high surface roughness, or the need for hazardous coreagents. Finally, stoichiometric control of ternary films grown by ALD is rare, but increasingly important, with emerging applications for metal borate films in catalysis and lithium ion batteries. The research herein is focused toward the development of new ALD processes for the broader application of metal, metal oxide, and metal borate thin films to future nanoscale technologies. These processes display self-limited growth and support the facile nucleation of smooth, continuous, high-purity films. Bis(trimethylsilyl) six-membered rings are employed as strongly-reducing organic coreagents for the ALD of titanium and antimony metal films. Additionally, new processes are developed for the growth of high-purity, low-resistivity cobalt and nickel metal films by exploiting the

  12. Enhanced Barrier Performance of Engineered Paper by Atomic Layer Deposited Al2O3 Thin Films.

    Science.gov (United States)

    Mirvakili, Mehr Negar; Van Bui, Hao; van Ommen, J Ruud; Hatzikiriakos, Savvas G; Englezos, Peter

    2016-06-01

    Surface modification of cellulosic paper is demonstrated by employing plasma assisted atomic layer deposition. Al2O3 thin films are deposited on paper substrates, prepared with different fiber sizes, to improve their barrier properties. Thus, a hydrophobic paper is created with low gas permeability by combining the control of fiber size (and structure) with atomic layer deposition of Al2O3 films. Papers are prepared using Kraft softwood pulp and thermomechanical pulp. The cellulosic wood fibers are refined to obtain fibers with smaller length and diameter. Films of Al2O3, 10, 25, and 45 nm in thickness, are deposited on the paper surface. The work demonstrates that coating of papers prepared with long fibers efficiently reduces wettability with slight enhancement in gas permeability, whereas on shorter fibers, it results in significantly lower gas permeability. Wettability studies on Al2O3 deposited paper substrates have shown water wicking and absorption over time only in papers prepared with highly refined fibers. It is also shown that there is a certain fiber size at which the gas permeability assumes its minimum value, and further decrease in fiber size will reverse the effect on gas permeability.

  13. Disorder and transport of silver in some layered metal sulfides

    NARCIS (Netherlands)

    Gerards, Anthonius Gijsbertus

    1987-01-01

    The chemical and physical properties of compounds with a layered structure are strongly determined by the two-dimensional nature of the bonding, viz. strong bonding within the layers and much weaker bonds between the layers; graphite is an example of such and anisotropic solid. the layered transitio

  14. Effect of corona pre-treatment on the performance of gas barrier layers applied by atomic layer deposition onto polymer-coated paperboard

    Energy Technology Data Exchange (ETDEWEB)

    Hirvikorpi, Terhi, E-mail: terhi.hirvikorpi@vtt.fi [VTT Technical Research Centre of Finland, Biologinkuja 7, P.O. Box 1000, FI-02044 VTT Espoo (Finland); Vaehae-Nissi, Mika, E-mail: mika.vaha-nissi@vtt.fi [VTT Technical Research Centre of Finland, Biologinkuja 7, P.O. Box 1000, FI-02044 VTT Espoo (Finland); Harlin, Ali, E-mail: ali.harlin@vtt.fi [VTT Technical Research Centre of Finland, Biologinkuja 7, P.O. Box 1000, FI-02044 VTT Espoo (Finland); Marles, Jaana, E-mail: jaana.marles@picosun.com [Picosun Oy, Tietotie 3, FI-02150 Espoo (Finland); Miikkulainen, Ville, E-mail: ville.miikkulainen@picosun.com [Picosun Oy, Tietotie 3, FI-02150 Espoo (Finland); Karppinen, Maarit, E-mail: maarit.karppinen@tkk.fi [Aalto University School of Technology and Science, Laboratory of Inorganic Chemistry, Kemistintie 1A, Espoo, P.O. Box 16100, 00076 Aalto (Finland)

    2010-11-15

    The effect of corona pre-treatment on the performance of Al{sub 2}O{sub 3} and SiO{sub 2} gas barrier layers applied by atomic layer deposition onto polymer-coated paperboards was studied. Both polyethylene and polylactide coated paperboards were corona treated prior to ALD. Corona treatment increased surface energies of the paperboard substrates, and this effect was still observed after several days. Al{sub 2}O{sub 3} and SiO{sub 2} films were grown on top of the polymer coatings at temperature of 100 deg. C using the atomic layer deposition (ALD) technique. For SiO{sub 2} depositions a new precursor, bis(diethylamido) silane, was used. The positive effect of the corona pre-treatment on the barrier properties of the polymer-coated paperboards with the ALD-grown layers was more significant with polyethylene coated paperboard and with thin deposited layers (shorter ALD process). SiO{sub 2} performed similarly to Al{sub 2}O{sub 3} with the PE coated board when it comes to the oxygen barrier, while the performance of SiO{sub 2} with the biopolymer-coated board was more moderate. The effect of corona pre-treatment was negligible or even negative with the biopolymer-coated board. The ALD film growth and the effect of corona treatment on different substrates require further investigation.

  15. Compressibility effects on the non-linear receptivity of boundary layers to dielectric barrier discharges

    Science.gov (United States)

    Denison, Marie F. C.

    The reduction of drag and aerodynamic heating caused by boundary layer transition is of central interest for the development of hypersonic vehicles. Receptivity to flow perturbation in the form of Tollmien-Schlichting (TS) wave growth often determines the first stage of the transition process, which can be delayed by depositing specific excitations into the boundary layer. Weakly ionized Dielectric Barrier Discharge (DBD) actuators are being investigated as possible sources of such excitations, but little is known today about their interaction with high-speed flows. In this framework, the first part of the thesis is dedicated to a receptivity study of laminar compressible boundary layers over a flat plate by linear stability analysis following an adjoint operator formulation, under DBD representative excitations assumed independent of flow conditions. The second part of the work concentrates on the development of a coupled plasma-Navier and Stokes solver targeted at the study of supersonic flow and compressibility effects on DBD forcing and non-parallel receptivity. The linear receptivity study of quasi-parallel compressible flows reveals several interesting features such as a significant shift of the region of maximum receptivity deeper into the flow at high Mach number and strong wave amplitude reduction compared to incompressible flows. The response to DBD relevant excitation distributions and to variations of the base flow conditions and system length scales follows these trends. Observed absolute amplitude changes and relative sensitivity modifications between source types are related to the evolution of the offset between forcing peak profile and relevant adjoint mode maximum. The analysis highlights the crucial importance of designing and placing the actuator in a way that matches its force field to the position of maximum boundary layer receptivity for the specific flow conditions of interest. In order to address the broad time and length scale spectrum

  16. First-Principles Investigations of the Working Mechanism of 2D h-BN as an Interfacial Layer for the Anode of Lithium Metal Batteries.

    Science.gov (United States)

    Shi, Le; Xu, Ao; Zhao, Tianshou

    2017-01-18

    An issue with the use of metallic lithium as an anode material for lithium-based batteries is dendrite growth, causing a periodic breaking and repair of the solid electrolyte interphase (SEI) layer. Adding 2D atomic crystals, such as h-BN, as an interfacial layer between the lithium metal anode and liquid electrolyte has been demonstrated to be effective to mitigate dendrite growth, thereby enhancing the Columbic efficiency of lithium metal batteries. But the underlying mechanism leading to the reduced dendrite growth remains unknown. In this work, with the aid of first-principle calculations, we find that the interaction between the h-BN and lithium metal layers is a weak van der Waals force, and two atomic layers of h-BN are thick enough to block the electron tunneling from lithium metal to electrolyte, thus prohibiting the decomposition of electrolyte. The interlayer spacing between the h-BN and lithium metal layers can provide larger adsorption energies toward lithium atoms than that provided by bare lithium or h-BN, making lithium atoms prefer to intercalate under the cover of h-BN during the plating process. The combined high stiffness of h-BN and the low diffusion energy barriers of lithium at the Li/h-BN interfaces induce a uniform distribution of lithium under h-BN, therefore effectively suppressing dendrite growth.

  17. The electronic and chemical structure of the a-B3CO0.5:Hy-to-metal interface from photoemission spectroscopy: implications for Schottky barrier heights.

    Science.gov (United States)

    Driver, M Sky; Paquette, Michelle M; Karki, S; Nordell, B J; Caruso, A N

    2012-11-01

    The electronic and chemical structure of the metal-to-semiconductor interface was studied by photoemission spectroscopy for evaporated Cr, Ti, Al and Cu overlayers on sputter-cleaned as-deposited and thermally treated thin films of amorphous hydrogenated boron carbide (a-B(x)C:H(y)) grown by plasma-enhanced chemical vapor deposition. The films were found to contain ~10% oxygen in the bulk and to have approximate bulk stoichiometries of a-B(3)CO(0.5):H(y). Measured work functions of 4.7/4.5 eV and valence band maxima to Fermi level energy gaps of 0.80/0.66 eV for the films (as-deposited/thermally treated) led to predicted Schottky barrier heights of 1.0/0.7 eV for Cr, 1.2/0.9 eV for Ti, 1.2/0.9 eV for Al, and 0.9/0.6 eV for Cu. The Cr interface was found to contain a thick partial metal oxide layer, dominated by the wide-bandgap semiconductor Cr(2)O(3), expected to lead to an increased Schottky barrier at the junction and the formation of a space-charge region in the a-B(3)CO(0.5):H (y) layer. Analysis of the Ti interface revealed a thick layer of metal oxide, comprising metallic TiO and Ti (2)O (3), expected to decrease the barrier height. A thinner, insulating Al(2)O(3) layer was observed at the Al-to-a-B(3)CO(0.5):H(y) interface, expected to lead to tunnel junction behavior. Finally, no metal oxides or other new chemical species were evident at the Cu-to-a-B(3)CO(0.5):H(y) interface in either the core level or valence band photoemission spectra, wherein characteristic metallic Cu features were observed at very thin overlayer coverages. These results highlight the importance of thin-film bulk oxygen content on the metal-to-semiconductor junction character as well as the use of Cu as a potential Ohmic contact material for amorphous hydrogenated boron carbide semiconductor devices such as high-efficiency direct-conversion solid-state neutron detectors.

  18. Metallic wave-impedance matching layers for broadband terahertz optical systems.

    Science.gov (United States)

    Kröll, Josef; Darmo, Juraj; Unterrainer, Karl

    2007-05-28

    We examine the potential of ultra-thin metallic layers for broadband wave-impedance matching in the terahertz frequency range. The metallic layer is modeled using Fresnel formulae for stratified optical medium. Experimental data for chromium and indium-tin-oxide layers, measured using time-domain terahertz spectroscopy over the frequency range 0.4 - 4.5 THz, are compared with theoretical results.

  19. Schottky barrier height modification of metal/4H-SiC contact using ultrathin TiO2 insertion method

    Science.gov (United States)

    Tsui, Bing-Yue; Cheng, Jung-Chien; Lee, Lurng-Shehng; Lee, Chwan-Ying; Tsai, Ming-Jinn

    2014-01-01

    The fabrication processes, electrical characteristics, and reliability of the Schottky barrier diodes (SBDs) on an n-type 4H-silicon carbide (SiC) substrate are investigated. To modulate the Schottky barrier height (SBH), titanium dioxide (TiO2) is inserted at the interface between the metal and the SiC substrate. Ni, Mo, Ti, and Al are chosen to form SBDs. The maximum SBH modulation of 0.3 eV is obtained with a 5-nm-thick TiO2 layer. The SBH pinning factors of the SBDs without TiO2 insertion and with 2-nm-thick TiO2 insertion are similar. Therefore, the mechanism of the SBH modulation is attributed to the interface dipole-induced potential drop. Finally, the reliability of the SBD with TiO2 insertion is evaluated. The SBH, ideality factor, and reverse leakage current are stable after high forward current stress at 300 A/cm2 for 15000 s. This work provides a simple method to modulate the SBH on SiC and is feasible for SBD application.

  20. Asymmetric polymeric membranes containing a metal-rich dense layer with a controlled thickness and method of making same

    KAUST Repository

    Peinemann, Klaus-Viktor

    2016-01-21

    A structure, and methods of making the structure are provided in which the structure can include: a membrane having a first layer and a second layer, the first layer comprising polymer chains formed with coordination complexes with metal ions, and the second layer consisting of a porous support layer formed of polymer chains substantially, if not completely, lacking the presence of metal ions. The structure can be an asymmetric polymeric membrane containing a metal-rich layer as the first layer. In various embodiments the first layer can be a metal-rich dense layer. The first layer can include pores. The polymer chains of the first layer can be closely packed. The second layer can include a plurality of macro voids and can have an absence of the metal ions of the first layer.

  1. Sustained hole inversion layer in a wide-bandgap metal-oxide semiconductor with enhanced tunnel current.

    Science.gov (United States)

    Shoute, Gem; Afshar, Amir; Muneshwar, Triratna; Cadien, Kenneth; Barlage, Douglas

    2016-02-04

    Wide-bandgap, metal-oxide thin-film transistors have been limited to low-power, n-type electronic applications because of the unipolar nature of these devices. Variations from the n-type field-effect transistor architecture have not been widely investigated as a result of the lack of available p-type wide-bandgap inorganic semiconductors. Here, we present a wide-bandgap metal-oxide n-type semiconductor that is able to sustain a strong p-type inversion layer using a high-dielectric-constant barrier dielectric when sourced with a heterogeneous p-type material. A demonstration of the utility of the inversion layer was also investigated and utilized as the controlling element in a unique tunnelling junction transistor. The resulting electrical performance of this prototype device exhibited among the highest reported current, power and transconductance densities. Further utilization of the p-type inversion layer is critical to unlocking the previously unexplored capability of metal-oxide thin-film transistors, such applications with next-generation display switches, sensors, radio frequency circuits and power converters.

  2. Sustained hole inversion layer in a wide-bandgap metal-oxide semiconductor with enhanced tunnel current

    Science.gov (United States)

    Shoute, Gem; Afshar, Amir; Muneshwar, Triratna; Cadien, Kenneth; Barlage, Douglas

    2016-02-01

    Wide-bandgap, metal-oxide thin-film transistors have been limited to low-power, n-type electronic applications because of the unipolar nature of these devices. Variations from the n-type field-effect transistor architecture have not been widely investigated as a result of the lack of available p-type wide-bandgap inorganic semiconductors. Here, we present a wide-bandgap metal-oxide n-type semiconductor that is able to sustain a strong p-type inversion layer using a high-dielectric-constant barrier dielectric when sourced with a heterogeneous p-type material. A demonstration of the utility of the inversion layer was also investigated and utilized as the controlling element in a unique tunnelling junction transistor. The resulting electrical performance of this prototype device exhibited among the highest reported current, power and transconductance densities. Further utilization of the p-type inversion layer is critical to unlocking the previously unexplored capability of metal-oxide thin-film transistors, such applications with next-generation display switches, sensors, radio frequency circuits and power converters.

  3. Thermal analysis of double-layer metal films during femtosecond laser heating

    Science.gov (United States)

    Chen, A. M.; Jiang, Y. F.; Sui, L. Z.; Liu, H.; Jin, M. X.; Ding, D. J.

    2011-05-01

    In this paper, the primary interest is the heat effect of the bottom-layer metal on the temperature distribution of the top-layer metal in a double-layer metal structure during femtosecond laser irradiation. The evolution of the surface electron and lattice temperature depends a lot on the thermal parameters of the substrate. The damage threshold can be increased by using a substrate material with high electron-lattice coupling factor. Next, we choose chrome as the bottom-layer material. The results of modeling show that the surface lattice temperature of top-layer gold can be reduced remarkably. For a fixed entire thickness of the double-layer film, there is an optimal proportion of top and bottom layers for which the damage threshold is the highest possible. Also, for increasing the damage threshold, a substrate with higher melting temperature should be chosen.

  4. Structural properties of dopping metallic impurities on CdS thin layers

    Directory of Open Access Journals (Sweden)

    S. Ghasemzadeh

    2016-12-01

    Full Text Available (Cu,Zn-dopped CdS thin layers were deposited on glass substrates by chemical bath deposition technique. The effects of the doping on the structural properties of CdS thin layers were studied by SEM and EDAX analysis. Hetero junction layers were produced with different nano structures and different fraction of voids and metallic ions.

  5. Structural properties of dopping metallic impurities on CdS thin layers

    OpenAIRE

    S. Ghasemzadeh; H. kangarlou

    2016-01-01

    (Cu,Zn)-dopped CdS thin layers were deposited on glass substrates by chemical bath deposition technique. The effects of the doping on the structural properties of CdS thin layers were studied by SEM and EDAX analysis. Hetero junction layers were produced with different nano structures and different fraction of voids and metallic ions.

  6. Fabrication of Polymer Solar Cells Using Aqueous Processing for All Layers Including the Metal Back Electrode

    DEFF Research Database (Denmark)

    Søndergaard, Roar; Helgesen, Martin; Jørgensen, Mikkel

    2011-01-01

    The challenges of printing all layers in polymer solar cells from aqueous solution are met by design of inks for the electron-, hole-, active-, and metallic back electrode-layers. The conversion of each layer to an insoluble state after printing enables multilayer formation from the same solvent ...

  7. The effect of the carbon nanotube buffer layer on the performance of a Li metal battery.

    Science.gov (United States)

    Zhang, Ding; Zhou, Yi; Liu, Changhong; Fan, Shoushan

    2016-06-07

    Lithium (Li) metal is one of the most promising candidates as an anode for the next-generation energy storage systems because of its high specific capacity and lowest negative electrochemical potential. But the growth of Li dendrites limits the application of the Li metal battery. In this work, a type of modified Li metal battery with a carbon nanotube (CNT) buffer layer inserted between the separator and the Li metal electrode was reported. The electrochemical results show that the modified batteries have a much better rate capability and cycling performance than the conventional Li metal batteries. The mechanism study by electrochemical impedance spectroscopy reveals that the modified battery has a smaller charge transfer resistance and larger Li ion diffusion coefficient during the deposition process on the Li electrode than the conventional Li metal batteries. Symmetric battery tests show that the interfacial behavior of the Li metal electrode with the buffer layer is more stable than the naked Li metal electrode. The morphological characterization of the CNT buffer layer and Li metal lamina reveals that the CNT buffer layer has restrained the growth of Li dendrites. The CNT buffer layer has great potential to solve the safety problem of the Li metal battery.

  8. Experimental investigation on coupling flows between liquid and liquid metal layers

    Science.gov (United States)

    Yano, Kanako; Tasaka, Yuji; Murai, Yuichi; Takeda, Yasushi; Yanagisawa, Takatoshi

    2008-11-01

    This study aims to clarify coupling of flows between liquid metal and other usual liquids, e.g. water or oil, in fluid dynamical systems. In past studies for two-layer Rayleigh-Bénard system where the immiscible two liquids are layered, two types of coupling were observed; these are called as ``mechanical coupling'' and ``thermal coupling.'' As a typical character of low Pr fluid, large-scale structure in the liquid metal layer has oscillating motion. In this study we investigate ``thermal coupling'' especially how the oscillation of cells in the liquid metal layer propagates to the upper liquid layer and vice versa by changing a ratio of the height of the layers and viscosity of the upper layer fluid. Visualization of the liquid metal motion was conducted by means of ultrasonic velocity profiling, and then the oscillating motion is expressed on the space-time velocity map. PIV measurement of the upper, transparent fluid layer shows the modulation of the convective motion due to the oscillation in the liquid metal layer. Point-wise measurement of temperature at several positions in the fluid layer represents the modulation quantitatively.

  9. Buffer layers on metal alloy substrates for superconducting tapes

    Science.gov (United States)

    Jia, Quanxi; Foltyn, Stephen R.; Arendt, Paul N.; Groves, James R.

    2004-06-29

    An article including a substrate, a layer of an inert oxide material upon the surface of the substrate, a layer of an amorphous oxide or oxynitride material upon the inert oxide material layer, a layer of an oriented cubic oxide material having a rock-salt-like structure upon the amorphous oxide material layer, and a layer of a SrRuO.sub.3 buffer material upon the oriented cubic oxide material layer is provided together with additional layers such as a HTS top-layer of YBCO directly upon the layer of a SrRuO.sub.3 buffer material layer. With a HTS top-layer of YBCO upon at least one layer of the SrRuO.sub.3 buffer material in such an article, J.sub.c 's of up to 1.3.times.10.sup.6 A/cm.sup.2 have been demonstrated with projected IC's of over 200 Amperes across a sample 1 cm wide.

  10. High-barrier Schottky contact on n-type 4H-SiC epitaxial layer and studies of defect levels by deep level transient spectroscopy (DLTS)

    Science.gov (United States)

    Nguyen, Khai V.; Pak, Rahmi O.; Oner, Cihan; Mannan, Mohammad A.; Mandal, Krishna C.

    2015-08-01

    High barrier Schottky contact has been fabricated on 50 μm n-type 4H-SiC epitaxial layers grown on 350 μm thick substrate 8° off-cut towards the [11̅20] direction. The 4H-SiC epitaxial wafer was diced into 10 x 10 mm2 samples. The metal-semiconductor junctions were fabricated by photolithography and dc sputtering with ruthenium (Ru). The junction properties were characterized through current-voltage (I-V) and capacitance-voltage (C-V) measurements. Detectors were characterized by alpha spectroscopy measurements in terms of energy resolution and charge collection efficiency using a 0.1 μCi 241Am radiation source. It was found that detectors fabricated from high work function rare transition metal Ru demonstrated very low leakage current and significant improvement of detector performance. Defect characterization of the epitaxial layers was conducted by deep level transient spectroscopy (DLTS) to thoroughly investigate the defect levels in the active region. The presence of a new defect level induced by this rare transition metal-semiconductor interface has been identified and characterized.

  11. Thermal barrier coating for alloy systems

    Science.gov (United States)

    Seals, Roland D.; White, Rickey L.; Dinwiddie, Ralph B.

    2000-01-01

    An alloy substrate is protected by a thermal barrier coating formed from a layer of metallic bond coat and a top coat formed from generally hollow ceramic particles dispersed in a matrix bonded to the bond coat.

  12. Anisotropic transport of normal metal-barrier-normal metal junctions in monolayer phosphorene

    Science.gov (United States)

    De Sarkar, Sangita; Agarwal, Amit; Sengupta, K.

    2017-07-01

    We study transport properties of a phosphorene monolayer in the presence of single and multiple potential barriers of height U 0 and width d, using both continuum and microscopic lattice models, and show that the nature of electron transport along its armchair edge (x direction) is qualitatively different from its counterpart in both conventional two-dimensional electron gas with Schrödinger-like quasiparticles and graphene or surfaces of topological insulators hosting massless Dirac quasiparticles. We show that the transport, mediated by massive Dirac electrons, allows one to achieve collimated quasiparticle motion along x and thus makes monolayer phosphorene an ideal experimental platform for studying Klein paradox in the context of gapped Dirac materials. We study the dependence of the tunneling conductance G\\equiv {{G}xx} as a function of d and U 0, and demonstrate that for a given applied voltage V its behavior changes from oscillatory to decaying function of d for a range of U 0 with finite non-zero upper and lower bounds, and provide analytical expression for these bounds within which G decays with d. We contrast such behavior of G with that of massless Dirac electrons in graphene and also with that along the zigzag edge (y direction) in phosphorene where the quasiparticles obey an effective Schrödinger equation at low energy. We also study transport through multiple barriers along x and demonstrate that these properties hold for transport through multiple barriers as well. Finally, we suggest concrete experiments which may verify our theoretical predictions.

  13. Layered transition metal carboxylates: efficient reusable heterogeneous catalyst for epoxidation of olefins.

    Science.gov (United States)

    Sen, Rupam; Bhunia, Susmita; Mal, Dasarath; Koner, Subratanath; Miyashita, Yoshitaro; Okamoto, Ken-Ichi

    2009-12-01

    Layered metal carboxylates [M(malonato)(H(2)O)(2)](n) (M = Ni(II) and Mn(II)) that have a claylike structure have been synthesized hydrothermally and characterized. The interlayer separation in these layered carboxylates is comparable to that of the intercalation distance of the naturally occurring clay materials or layered double hydroxides (LDHs). In this study, we have demonstrated that, instead of intercalating the metal complex into layers of the clay or LDH, layered transition metal carboxylates, [M(malonato)(H(2)O)(2)](n), as such can be used as a recyclable heterogeneous catalyst in olefin epoxidation reaction. Metal carboxylates [M(malonato)(H(2)O)(2)](n) exhibit excellent catalytic performance in olefin epoxidation reaction.

  14. Considerably improved photovoltaic performance of carbon nanotube-based solar cells using metal oxide layers.

    Science.gov (United States)

    Wang, Feijiu; Kozawa, Daichi; Miyauchi, Yuhei; Hiraoka, Kazushi; Mouri, Shinichiro; Ohno, Yutaka; Matsuda, Kazunari

    2015-02-18

    Carbon nanotube-based solar cells have been extensively studied from the perspective of potential application. Here we demonstrated a significant improvement of the carbon nanotube solar cells by the use of metal oxide layers for efficient carrier transport. The metal oxides also serve as an antireflection layer and an efficient carrier dopant, leading to a reduction in the loss of the incident solar light and an increase in the photocurrent, respectively. As a consequence, the photovoltaic performance of both p-single-walled carbon nanotube (SWNT)/n-Si and n-SWNT/p-Si heterojunction solar cells using MoOx and ZnO layers is improved, resulting in very high photovoltaic conversion efficiencies of 17.0 and 4.0%, respectively. These findings regarding the use of metal oxides as multifunctional layers suggest that metal oxide layers could improve the performance of various electronic devices based on carbon nanotubes.

  15. Influence of metal bonding layer on strain transfer performance of FBG

    Science.gov (United States)

    Liu, Hao; Chen, Weimin; Zhang, Peng; Liu, Li; Shu, Yuejie; Wu, Jun

    2013-01-01

    Metal bonding layer seriously affects the strain transfer performance of Fiber Bragg Grating (FBG). Based on the mode of FBG strain transfer, the influence of the length, the thickness, Poisson's ratio, elasticity modulus of metal bonding layer on the strain transfer coefficient of FBG is analyzed by numerical simulation. FBG is packaged to steel wire using metal bonding technology of FBG. The tensile tests of different bonding lengths and elasticity modulus are carried out. The result shows the strain transfer coefficient of FBGs are 0.9848,0.962 and their average strain sensitivities are 1.076 pm/μɛ,1.099 pm/μɛ when the metal bonding layer is zinc, whose lengths are 15mm, 20mm, respectively. The strain transfer coefficient of FBG packaged by metal bonding layer raises 8.9 percent compared to epoxy glue package. The preliminary experimental results show that the strain transfer coefficient increases with the length of metal bonding layer, decreases with the thickness of metal bonding layer and the influence of Poisson's ratio can be ignored. The experiment result is general agreement with the analysis and provides guidance for metal package of FBG.

  16. Emerging interface dipole versus screening effect in copolymer/metal nano-layered systems

    Energy Technology Data Exchange (ETDEWEB)

    Torrisi, V., E-mail: v.torrisi@unict.it [Laboratory for Molecular Surfaces and Nanotechnology (LAMSUN), Department of Chemical Sciences, University of Catania, Viale A. Doria 6, 95125, Catania (Italy); Ruffino, F. [Dipartimento di Fisica ed Astronomia-Università di Catania, via S. Sofia 64, 95123 Catania (Italy); MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy); Liscio, A. [Istituto per la Sintesi e la Fotoreattività CNR, via Gobetti 101, 40129, Bologna (Italy); Grimaldi, M.G. [Dipartimento di Fisica ed Astronomia-Università di Catania, via S. Sofia 64, 95123 Catania (Italy); MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy); Marletta, G. [Laboratory for Molecular Surfaces and Nanotechnology (LAMSUN), Department of Chemical Sciences, University of Catania, Viale A. Doria 6, 95125, Catania (Italy)

    2015-12-30

    Graphical abstract: - Highlights: • Gold/copolymer multilayered thin films are prepared. • Mapping of the multilayers surface potential are performed by Kelvin Probe Force Microscopy. • Surface potential is controlled by the thickness and the surface coverage of the gold layer. • The work function of the gold layer is influenced by the underlying copolymer layer. - Abstract: Despite to the importance on the charge carrier injection and transport at organic/metal interface, there is yet an incomplete estimation of the various contribution to the overall dipole. This work shows how the mapping of the surface potential performed by Kelvin Probe Force Microscopy (KPFM) allows the direct observation of the interface dipole within an organic/metal multilayered structure. Moreover, we show how the sub-surface sensitivity of the KPFM depends on the thickness and surface coverage of the metallic layer. This paper proposes a way to control the surface potential of the exposed layer of an hybrid layered system by controlling the interface dipole at the organic/metal interface as a function of the nanometer scale thickness and the surface coverage of the metallic layer. We obtained a layered system constituted by repeated sequence of a copolymer film, poly(n-butylacrylate)-b-polyacrilic acid, and Au layer. We compared the results obtained by means of scanning probe microscopy technique with the results of the KPFM technique, that allows us to obtain high-contrast images of the underlying layer of copolymer behind a typical threshold, on the nanoscale, of the thickness of the metal layer. We considered the effect of the morphology of the gold layer on the covered area at different thicknesses by using the scanning electron microscopy technique. This finding represents a step forward towards the using of dynamic atomic force microscopy based characterization to explore the electrical properties of the sub-surface states of layered nanohybrid, that is a critical point for

  17. Twin Boundaries merely as Intrinsically Kinematic Barriers for Screw Dislocation Motion in FCC Metals

    Science.gov (United States)

    Zhang, Jiayong; Zhang, Hongwu; Ye, Hongfei; Zheng, Yonggang

    2016-03-01

    Metals with nanoscale twins have shown ultrahigh strength and excellent ductility, attributed to the role of twin boundaries (TBs) as strong barriers for the motion of lattice dislocations. Though observed in both experiments and simulations, the barrier effect of TBs is rarely studied quantitatively. Here, with atomistic simulations and continuum based anisotropic bicrystal models, we find that the long-range interaction force between coherent TBs and screw dislocations is negligible. Further simulations of the pileup behavior of screw dislocations in front of TBs suggest that screw dislocations can be blocked kinematically by TBs due to the change of slip plane, leading to the pileup of subsequent dislocations with the elastic repulsion actually from the pinned dislocation in front of the TB. Our results well explain the experimental observations that the variation of yield strength with twin thickness for ultrafine-grained copper follows the Hall-Petch relationship.

  18. Twin Boundaries merely as Intrinsically Kinematic Barriers for Screw Dislocation Motion in FCC Metals.

    Science.gov (United States)

    Zhang, Jiayong; Zhang, Hongwu; Ye, Hongfei; Zheng, Yonggang

    2016-03-10

    Metals with nanoscale twins have shown ultrahigh strength and excellent ductility, attributed to the role of twin boundaries (TBs) as strong barriers for the motion of lattice dislocations. Though observed in both experiments and simulations, the barrier effect of TBs is rarely studied quantitatively. Here, with atomistic simulations and continuum based anisotropic bicrystal models, we find that the long-range interaction force between coherent TBs and screw dislocations is negligible. Further simulations of the pileup behavior of screw dislocations in front of TBs suggest that screw dislocations can be blocked kinematically by TBs due to the change of slip plane, leading to the pileup of subsequent dislocations with the elastic repulsion actually from the pinned dislocation in front of the TB. Our results well explain the experimental observations that the variation of yield strength with twin thickness for ultrafine-grained copper follows the Hall-Petch relationship.

  19. Surface chemistry of the atomic layer deposition of metals and group III oxides

    Science.gov (United States)

    Goldstein, David Nathan

    Atomic Layer Deposition (ALD) is a thin-film growth technique offering precise control of film thickness and the ability to coat high-aspect-ratio features such as trenches and nanopowders. Unlike other film growth techniques, ALD does not require harsh processing conditions and is not limited by line-of-sight deposition. Emerging applications for ALD materials include semiconductor devices, gas sensors, and water-diffusion barriers. The chemistry behind ALD involves understanding how the precursors interact with surfaces to deposit the desired material. All ALD precursors need to be stable on the substrate to ensure self-limiting behavior yet reactive enough to be easily removed with the second reagent. Recent precursor development has provided many volatile organometallic compounds for most of the periodic table. As the number of precursors increases, proper precursor choice becomes crucial. This is because the film properties, growth rates, and growth temperature vary widely between the precursors. Many of the above traits can be predicted with knowledge of the precursor reaction mechanisms. This thesis aims to link surface reaction mechanisms to observed growth and nucleation trends in metal and oxide ALD systems. The first portion of this thesis explores the mechanisms of two ALD oxide systems. First, I examine the mechanism of ALD alumina with ozone. Ozone is used as an oxidant in the semiconductor industry because the deposited Al 2O3 films possess better insulating properties and ozone is easier to purge from a vacuum system. FT-IR analysis reveals a complicated array of surface intermediates such as formate, carbonate, and methoxy groups that form during Al2O3 growth with ozone. Next, a new method to deposit thin films of Ga2O3 is introduced. Gallium oxide is a transparent conducting oxide that needs expensive solid precursors to be deposited by ALD. I show that trimethylgallium is a good high-temperature ALD precursor that deposits films of Ga2O 3 with

  20. Enhancement of thermal spin transfer torque by double-barrier magnetic tunnel junctions with a nonmagnetic metal spacer

    Science.gov (United States)

    Chen, C. H.; Tseng, P.; Yang, Y. Y.; Hsueh, W. J.

    2017-01-01

    Enhancement of thermal spin transfer torque in a double-barrier magnetic tunnel junction with a nonmagnetic-metal spacer is proposed in this study. The results indicate that, given the same temperature difference, thermal spin transfer torque and charge current density for the proposed double barrier magnetic tunnel junction configuration can be approximately twice as much as that of the traditional single-barrier magnetic tunnel junctions. This enhancement can be attributed to the resonant tunneling mechanism in the double-barrier structure.

  1. Interference effect on pairing correlations in a metal-superconductor-metal layer with magnetic interfaces

    Science.gov (United States)

    Choi, Chi-Hoon

    2012-05-01

    We study the proximity effect in a multilayer composed of a normal metal and a superconductor with spin-active interfaces. The symmetry of the induced pair amplitude is analyzed while varying the interface distance and the direction of the interface spins. We apply the general Green's function formalism without making the quasiclassical approximation in order to study the interference effect from the surrounding interfaces of the superconducting layer. By utilizing the formalism developed by A. Millis et al., we compute the Keldysh Green's function while incorporating the general boundary condition for magnetic interfaces of a superconducting heterostructure. The interference can have a profound effect on the proximity phenomena in the ballistic limit when the interface distance becomes less than the superconducting coherence length. We also discuss the effect of the direction of the interface spins on the induction of the odd-frequency equal-spin pairing state, which is important for applications of ferromagnetic quantum devices.

  2. Electrical properties of nanosized non-barrier inhomogeneities in Zn-based metal-semiconductor contacts to InP

    DEFF Research Database (Denmark)

    Clausen, Thomas; Leistiko, Otto

    1998-01-01

    We have found that the electrical properties of carriers across the metal-semiconductor interface for alloyed Zn based metallizations to n- and p-InP are dominated by nanosized non-barrier inhomogeneities. The effective area covered by the nanosized regions is a small fraction of the contact area...

  3. Thin-film Nanofibrous Composite Membranes Containing Cellulose or Chitin Barrier Layers Fabricated by Ionic Liquids

    Energy Technology Data Exchange (ETDEWEB)

    H Ma; B Hsiao; B Chu

    2011-12-31

    The barrier layer of high-flux ultrafiltration (UF) thin-film nanofibrous composite (TFNC) membranes for purification of wastewater (e.g., bilge water) have been prepared by using cellulose, chitin, and a cellulose-chitin blend, regenerated from an ionic liquid. The structures and properties of regenerated cellulose, chitin, and a cellulose-chitin blend were analyzed with thermogravimetric analysis (TGA) and wide-angle X-ray diffraction (WAXD). The surface morphology, pore size and pore size distribution of TFNC membranes were determined by SEM images and molecular weight cut-off (MWCO) methods. An oil/water emulsion, a model of bilge water, was used as the feed solution, and the permeation flux and rejection ratio of the membranes were investigated. TFNC membranes based on the cellulose-chitin blend exhibited 10 times higher permeation flux when compared with a commercial UF membrane (PAN10, Sepro) with a similar rejection ratio after filtration over a time period of up to 100 h, implying the practical feasibility of such membranes for UF applications.

  4. Energy barrier development at the metal chain-metallic carbon nanotube nanocontact

    CERN Document Server

    Kong, K J; Ihm, J S

    1999-01-01

    We perform ab initio pseudopotential calculations for a nanocontact between a metallic carbon nanotube and a copper chain. We find that the on-top position is the most stable geometry of the copper chain on the nanotube and a local energy gap of <= 0.1 eV opens as the mirror symmetry of the nanotube is broken by the presence of copper. A weak ionic bonding is formed between the tube and the copper chain and the charge density in the conducting channel around the Fermi level is reduced at the contact region. Therefore, the electronic transport across the contact occurs essentially through the tunneling process. Appearance of such a locally semiconducting property in the intrinsically metallic carbon nanotube can explain the unusual low-temperature current-voltage characteristics exhibiting a huge contact resistance or a quantum dot behavior.

  5. Double ferromagnetic metal/semiconductor schottky barrier confined quasi-ballistic transport channel as spin polarizer

    Institute of Scientific and Technical Information of China (English)

    Wen Wu

    2007-01-01

    Spin polarizer is one of the most important devices for the newly developing field of spintronics, which may revolute the popular information techniques. Here we present a phenomenal model for a novel spin polarizer, which utilizes two back to back ferromagnetic metal/semiconductor Schottky barriers to define a semiconductor transport channel whose length is less than the spin decoherence length of the host semiconductor. Along this channel, conducting electrons move diffusively in momentum space while they keep ballistic motion in spin space. Across the channel, electrons suffer a spin dependent tunneling, which establishes spin polarization along the channel.

  6. Two-dimensional ferromagnet/semiconductor transition metal dichalcogenide contacts: p-type Schottky barrier and spin-injection control

    KAUST Repository

    Gan, Liyong

    2013-09-26

    We study the ferromagnet/semiconductor contacts formed by transition metal dichalcogenide monolayers, focusing on semiconducting MoS2 and WS2 and ferromagnetic VS2. We investigate the degree of p-type doping and demonstrate tuning of the Schottky barrier height by vertical compressive pressure. An analytical model is presented for the barrier heights that accurately describes the numerical findings and is expected to be of general validity for all transition metal dichalcogenide metal/semiconductor contacts. Furthermore, magnetic proximity effects induce a 100% spin polarization at the Fermi level in the semiconductor where the spin splitting increases up to 0.70 eV for increasing pressure.

  7. Characterization of Transition Metal Carbide Layers Synthesized by Thermo-reactive Diffusion Processes

    DEFF Research Database (Denmark)

    Laursen, Mads Brink; Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin

    2015-01-01

    Hard wear resistant surface layers of transition metal carbides can be produced by thermo-reactive diffusion processes where interstitial elements from a steel substrate together with external sources of transition metals (Ti, V, Cr etc.) form hard carbide and/or nitride layers at the steel surface...... electron microscopy, X-ray diffraction and Vickers hardness testing. The study shows that porosityfree, homogenous and very hard surface layers can be produced by thermo-reactive diffusion processes. The carbon availability of the substrate influences thickness of obtained layers, as Vanadis 6 tool steel...

  8. Enhanced Faraday Rotation via Resonant Tunnelling in Tri-Layers Containing Magneto-Optical Metals

    CERN Document Server

    Moccia, Massimo; Galdi, Vincenzo; Alu', Andrea; Engheta, Nader

    2013-01-01

    We study resonant tunnelling effects that can occur in tri-layer structures featuring a dielectric layer sandwiched between two magneto-optical-metal layers. We show that the resonance splitting associated with these phenomena can be exploited to enhance Faraday rotation at optical frequencies. Our results indicate that, in the presence of realistic loss levels, a tri-layer structure of sub-wavelength thickness is capable of yielding sensible (~10{\\deg}) Faraday rotation with transmittance levels that are an order of magnitude larger than those attainable with a standalone slab of magneto-optical metal of same thickness.

  9. Superior Stable and Long Life Sodium Metal Anodes Achieved by Atomic Layer Deposition.

    Science.gov (United States)

    Zhao, Yang; Goncharova, Lyudmila V; Lushington, Andrew; Sun, Qian; Yadegari, Hossein; Wang, Biqiong; Xiao, Wei; Li, Ruying; Sun, Xueliang

    2017-03-03

    Na-metal batteries are considered as the promising alternative candidate for Li-ion battery beneficial from the wide availability and low cost of sodium, high theoretical specific capacity, and high energy density based on the plating/stripping processes and lowest electrochemical potential. For Na-metal batteries, the crucial problem on metallic Na is one of the biggest challenges. Mossy or dendritic growth of Na occurs in the repetitive Na stripping/plating process with an unstable solid electrolyte interphase layer of nonuniform ionic flux, which can not only lead to the low Coulombic efficiency, but also can create short circuit risks, resulting in possible burning or explosion. In this communication, the atomic layer deposition of Al2 O3 coating is first demonstrated for the protection of metallic Na anode for Na-metal batteries. By protecting Na foil with ultrathin Al2 O3 layer, the dendrites and mossy Na formation have been effectively suppressed and lifetime has been significantly improved. Furthermore, the thickness of protective layer has been further optimized with 25 cycles of Al2 O3 layer presenting the best performance over 500 cycles. The novel design of atomic layer deposition protected metal Na anode may bring in new opportunities to the realization of the next-generation high energy-density Na metal batteries.

  10. Schottky barrier at graphene/metal oxide interfaces: insight from first-principles calculations

    Science.gov (United States)

    Cheng, Kai; Han, Nannan; Su, Yan; Zhang, Junfeng; Zhao, Jijun

    2017-02-01

    Anode materials play an important role in determining the performance of lithium ion batteries. In experiment, graphene (GR)/metal oxide (MO) composites possess excellent electrochemical properties and are promising anode materials. Here we perform density functional theory calculations to explore the interfacial interaction between GR and MO. Our result reveals generally weak physical interactions between GR and several MOs (including Cu2O, NiO). The Schottky barrier height (SBH) in these metal/semiconductor heterostructures are computed using the macroscopically averaged electrostatic potential method, and the role of interfacial dipole is discussed. The calculated SBHs below 1 eV suggest low contact resistance; thus these GR/MO composites are favorable anode materials for better lithium ion batteries.

  11. Schottky barrier at graphene/metal oxide interfaces: insight from first-principles calculations

    Science.gov (United States)

    Cheng, Kai; Han, Nannan; Su, Yan; Zhang, Junfeng; Zhao, Jijun

    2017-01-01

    Anode materials play an important role in determining the performance of lithium ion batteries. In experiment, graphene (GR)/metal oxide (MO) composites possess excellent electrochemical properties and are promising anode materials. Here we perform density functional theory calculations to explore the interfacial interaction between GR and MO. Our result reveals generally weak physical interactions between GR and several MOs (including Cu2O, NiO). The Schottky barrier height (SBH) in these metal/semiconductor heterostructures are computed using the macroscopically averaged electrostatic potential method, and the role of interfacial dipole is discussed. The calculated SBHs below 1 eV suggest low contact resistance; thus these GR/MO composites are favorable anode materials for better lithium ion batteries. PMID:28165485

  12. Surface plasmon dispersion engineering via double-metallic AU/AG layers for nitride light-emitting diodes

    Science.gov (United States)

    Tansu, Nelson; Zhao, Hongping; Zhang, Jing; Liu, Guangyu

    2014-04-01

    A double-metallic deposition process is used whereby adjacent layers of different metals are deposited on a substrate. The surface plasmon frequency of a base layer of a first metal is tuned by the surface plasmon frequency of a second layer of a second metal formed thereon. The amount of tuning is dependent upon the thickness of the metallic layers, and thus tuning can be achieved by varying the thicknesses of one or both of the metallic layers. In a preferred embodiment directed to enhanced LED technology in the green spectrum regime, a double-metallic Au/Ag layer comprising a base layer of gold (Au) followed by a second layer of silver (Ag) formed thereon is deposited on top of InGaN/GaN quantum wells (QWs) on a sapphire/GaN substrate.

  13. Proximity Effect in BSCCO Intrinsic Josephson Junctions Contacted with a Normal Metal Layer

    Science.gov (United States)

    Suzuki, Minoru; Koizumi, Masayuki; Ohmaki, Masayuki; Kakeya, Itsuhiro; Shukrinov, Yu. M.

    Superconductivity proximity effect is numerically evaluated based on McMillan's tunneling proximity model for a sandwich of a normal metal layer on top of the surface superconducting layer of intrinsic Josephson junctions in a Bi2Sr2CaCu2O8+δ (BSCCO) crystal. Due to the very thin thickness of 0.3 nm of the superconducting layer in IJJs, the surface layer is subject to influence of the proximity effect when the top layer is contacted with a normal metal layer. The effect manifests itself as a significant change in the characteristics of the IJJ surface Josephson junction. It is found that when the superconducting layer thickness is smaller than 0.6 nm, the pair potential reduces significantly, leading to an almost complete suppression of the critical Josephson current density for the surface junction. This result can partly explain the experimental results on the IJJ characteristics of a mesa type structure.

  14. Design and fabrication of highly heat-resistant Mo/Si multilayer soft X-ray mirrors with interleaved barrier layers.

    Science.gov (United States)

    Takenaka, H; Ito, H; Haga, T; Kawamura, T

    1998-05-01

    Introducing interleaved carbon barrier layers improves the heat-resistance of Mo/Si multilayers. The soft X-ray reflectivities of the multilayers were calculated, and the effects of heating on both the reflectivities and layer structures of Mo/Si multilayers with and without barrier layers were investigated using X-ray diffraction and transmission electron microscopy. The results show that, for applications using intense soft X-ray beams, Mo/Si multilayers with interleaved carbon barrier layers are better mirrors than Mo/Si multilayers because they have much better heat resistance and almost the same soft X-ray reflectivity as the Mo/Si multilayers.

  15. Impact of InGaN back barrier layer on performance of AIInN/AlN/GaN MOS-HEMTs

    Science.gov (United States)

    Swain, Sanjit Kumar; Adak, Sarosij; Pati, Sudhansu Kumar; Sarkar, Chandan Kumar

    2016-09-01

    In the present work, we have discussed the effect of InGaN back barrier on device performances of 100 nm gate length AlInN/AlN/GaN metal oxide semiconductor high electron mobility transistor (MOS-HEMT) device and a wide comparison is made with respect to without considering the back barrier layer. The InGaN layer is introduced in the intension to raise the conduction band of GaN buffer with respect to GaN channel so that there is an improvement in the carrier confinement and at the same time witnessed excellent high frequency performance. The simulations are carried out using 2D Sentaurus TCAD simulator using Hydrodynamic mobility model by taking interface traps into consideration. Due to high value of two-dimensional electron gas (2DEG) density and mobility in AlInN/AlN/GaN MOS-HEMT device, higher drain current density is achieved. Simulation are carried out for different device parameters such as transfer characteristic (Id-Vg), transconductance factor (gm), drain induced barrier lowering (DIBL), Subthreshold slope (SS), conduction band energy, transconductance generation factor (gm/Id) and electric field. We have also examined the RF performance such as, total gate capacitance (Cgg), current gain cutoff frequency (fT) and power gain cutoff frequency (fmax) of the proposed devices. Use of InGaN back barrier tends to increase threshold voltage towards more positive value, reduced DIBL, and improves SS and significant growth in (gm/Id) by 5.5%. It also helps to achieve better frequency response like substantial increase in fT up to 91 GHz with current gain 60 dB as compare to 67 GHz with 56 dB for the device without considering back barrier and increase in fmax up to 112 GHz with respect 94 GHz. These results evident that use of InGaN back barrier in such devices can be better solution for future analog and RF applications.

  16. Ultraviolet-enhanced light emitting diode employing individual ZnO microwire with SiO{sub 2} barrier layers

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yingtian [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); State Key Laboratory of High Power Semiconductor Laser, Changchun University of Science and Technology, Changchun 130022 (China); Xu, Li [State Key Laboratory of High Power Semiconductor Laser, Changchun University of Science and Technology, Changchun 130022 (China); Dai, Jun [State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096 (China); Ma, Yan; Chu, Xianwei; Zhang, Yuantao; Du, Guotong; Zhang, Baolin; Yin, Jingzhi, E-mail: yjz886666@163.com [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012 (China)

    2015-05-25

    This paper details the fabrication of n-ZnO single microwire (SMW)-based high-purity ultraviolet light-emitting diodes (UV-LEDs) with an added SiO{sub 2} barrier layer on the p-Si substrate. However, the current-voltage (I-V) curve exhibited non-ideal rectifying characteristics. Under forward bias, both UV and visible emissions could be detected by electroluminescence (EL) measurement. When bias voltage reached 60 V at room temperature, a UV emission spike occurred at 390 nm originating from the n-ZnO SMW. Compared with the EL spectrum of the n-ZnO SMW/p-Si heterojunction device without the SiO{sub 2} barrier layer, we saw improved UV light extraction efficiency from the current-blocking effect of the SiO{sub 2} layer. The intense UV emission in the n-ZnO SMW/SiO{sub 2}/p-Si heterojunction indicated that the SiO{sub 2} barrier layer can restrict the movement of electrons as expected and result in effective electron-hole recombination in ZnO SMW.

  17. Thermal analysis of thin multi-layer metal films during femtosecond laser heating

    Science.gov (United States)

    Karakas, A.; Tunc, M.; Camdali, Ü.

    2010-12-01

    Multi-layer metals films are widely used in modern engineering applications such as gold-coated metal mirrors used in high power laser systems. A transient heat flux model is derived to analyze multi-layer metal films under laser heating. The two separate system composed of electrons and the lattice is considered to take into account the electron-lattice interaction. The present model predicted the effects of underlying chromium's thermal properties on temperature rise of the top gold layer. The effects of two adjacent and different metals with different electron-lattice coupling factors are analyzed for the heating mechanism of different lattices. The derived transient model combined with the two different conservation equations for the lattice and electrons are applied for the ultra short-pulse laser heating of a multi-layer film composed of gold and chromium.

  18. Metal-organic semiconductor interfacial barrier height determination from internal photoemission signal in spectral response measurements

    Science.gov (United States)

    Kumar, Sandeep; Iyer, S. Sundar Kumar

    2017-04-01

    Accurate and convenient evaluation methods of the interfacial barrier ϕb for charge carriers in metal semiconductor (MS) junctions are important for designing and building better opto-electronic devices. This becomes more critical for organic semiconductor devices where a plethora of molecules are in use and standardised models applicable to myriads of material combinations for the different devices may have limited applicability. In this paper, internal photoemission (IPE) from spectral response (SR) in the ultra-violet to near infra-red range of different MS junctions of metal-organic semiconductor-metal (MSM) test structures is used to determine more realistic MS ϕb values. The representative organic semiconductor considered is [6, 6]-phenyl C61 butyric acid methyl ester, and the metals considered are Al and Au. The IPE signals in the SR measurement of the MSM device are identified and separated before it is analysed to estimate ϕb for the MS junction. The analysis of IPE signals under different bias conditions allows the evaluation of ϕb for both the front and back junctions, as well as for symmetric MSM devices.

  19. ZnO buffer layer for metal films on silicon substrates

    Science.gov (United States)

    Ihlefeld, Jon

    2014-09-16

    Dramatic improvements in metallization integrity and electroceramic thin film performance can be achieved by the use of the ZnO buffer layer to minimize interfacial energy between metallization and adhesion layers. In particular, the invention provides a substrate metallization method utilizing a ZnO adhesion layer that has a high work of adhesion, which in turn enables processing under thermal budgets typically reserved for more exotic ceramic, single-crystal, or metal foil substrates. Embodiments of the present invention can be used in a broad range of applications beyond ferroelectric capacitors, including microelectromechanical systems, micro-printed heaters and sensors, and electrochemical energy storage, where integrity of metallized silicon to high temperatures is necessary.

  20. Metallic corrosion processes reactivation sustained by iron-reducing bacteria: Implication on long-term stability of protective layers

    Science.gov (United States)

    Esnault, L.; Jullien, M.; Mustin, C.; Bildstein, O.; Libert, M.

    In deep geological environments foreseen for the disposal of radioactive waste, metallic containers will undergo anaerobic corrosion. In this context, the formation of corrosion products such as magnetite may reduce the rate of corrosion processes through the formation of a protective layer. This study aims at determining the direct impact of iron-reducing bacteria (IRB) activity on the stability of corrosion protective layers. Batch experiments investigating iron corrosion processes including the formation of secondary magnetite and its subsequent alteration in the presence of IRB show the bacteria ability to use structural Fe(III) for respiration which leads to the sustainment of a high corrosion rate. With the bio-reduction of corrosion products such as magnetite, and H 2 as electron donor, IRB promote the reactivation of corrosion processes in corrosive environments by altering the protective layer. This phenomenon could have a major impact on the long-term stability of metallic compounds involved in multi-barrier system for high-level radioactive waste containment.

  1. Passivation of a Metal Contact with a Tunneling Layer

    DEFF Research Database (Denmark)

    Loozen, X.; Larsen, J.B.; Dross, F.

    2011-01-01

    The potential of contact passivation for increasing cell performance is indicated by several results reported in the literature. However, scant characterization of the tunneling layers used for that purpose has been reported. In this paper, contact passivation is investigated by insertion...... of an ultra-thin AlOx layer between an n-type emitter and a Ti/Pd/Ag contact. By using a 1.5nm thick layer, an increase of the minority carrier lifetime by a factor of 2.7 is achieved. Since current-voltage measurements indicate that an ohmic behavior is conserved for AlOx layers as thick as 1.5nm, a 1.5nm Al......Ox layer is found to be a candidate of choice for contact passivation....

  2. Study of simple plane wave generator with an air-metal barrier

    Directory of Open Access Journals (Sweden)

    Wei Xiong

    2014-06-01

    Full Text Available Plane wave generators (PWGs are used to accelerate flyer plates to high velocities with their generated plane waves, which are widely used in the test of dynamic properties of materials. The traditional PWG is composed of two explosives with different detonation velocities. It is difficult to implement the related fabrication processes and control the generated waves due to its complicated structures. A simple plane wave generator is presented in this paper, which is composed of two identical cylindrical high explosive (HE charges and an air-metal barrier. A theoretical model was established based on two different paths of the propagation of detonation waves, based on which the size of air-metal barrier was calculated for a given charge. The corresponding numerical simulations were also carried out by AUTODYN-2D® based on the calculated results, which were used to compare with the theoretical calculations. A detonation wave with a flatness of 0.039 μs within the range of 70-percent diameter of the main charge was obtained through the simulations.

  3. Study of simple plane wave generator with an air-metal barrier

    Institute of Scientific and Technical Information of China (English)

    Wei XIONG; Xian-feng ZHANG; Zhong-wei GUAN; Yong HE; Liang QIAO; Li-li GUO

    2014-01-01

    Plane wave generators (PWGs) are used to accelerate flyer plates to high velocities with their generated plane waves, which are widely used in the test of dynamic properties of materials. The traditional PWG is composed of two explosives with different detonation velocities. It is difficult to implement the related fabrication processes and control the generated waves due to its complicated structures. A simple plane wave generator is presented in this paper, which is composed of two identical cylindrical high explosive (HE) charges and an air-metal barrier. A theoretical model was established based on two different paths of the propagation of detonation waves, based on which the size of air-metal barrier was calculated for a given charge. The corresponding numerical simulations were also carried out by AUTODYN-2D® based on the calculated results, which were used to compare with the theoretical calculations. A detonation wave with a flatness of 0.039 ms within the range of 70-percent diameter of the main charge was obtained through the simulations.

  4. Emerging interface dipole versus screening effect in copolymer/metal nano-layered systems

    Science.gov (United States)

    Torrisi, V.; Ruffino, F.; Liscio, A.; Grimaldi, M. G.; Marletta, G.

    2015-12-01

    Despite to the importance on the charge carrier injection and transport at organic/metal interface, there is yet an incomplete estimation of the various contribution to the overall dipole. This work shows how the mapping of the surface potential performed by Kelvin Probe Force Microscopy (KPFM) allows the direct observation of the interface dipole within an organic/metal multilayered structure. Moreover, we show how the sub-surface sensitivity of the KPFM depends on the thickness and surface coverage of the metallic layer. This paper proposes a way to control the surface potential of the exposed layer of an hybrid layered system by controlling the interface dipole at the organic/metal interface as a function of the nanometer scale thickness and the surface coverage of the metallic layer. We obtained a layered system constituted by repeated sequence of a copolymer film, poly(n-butylacrylate)-b-polyacrilic acid, and Au layer. We compared the results obtained by means of scanning probe microscopy technique with the results of the KPFM technique, that allows us to obtain high-contrast images of the underlying layer of copolymer behind a typical threshold, on the nanoscale, of the thickness of the metal layer. We considered the effect of the morphology of the gold layer on the covered area at different thicknesses by using the scanning electron microscopy technique. This finding represents a step forward towards the using of dynamic atomic force microscopy based characterization to explore the electrical properties of the sub-surface states of layered nanohybrid, that is a critical point for nanohybrid applications in sensors and energy storage devices.

  5. Upper ocean observations in eastern Caribbean Sea reveal barrier layer within a warm core eddy

    Science.gov (United States)

    Rudzin, J. E.; Shay, L. K.; Jaimes, B.; Brewster, J. K.

    2017-02-01

    Three-dimensional measurements of a large warm core eddy (WCE) and the Caribbean Current are acquired using oceanic profilers deployed during a NOAA research aircraft study in September 2014 in the eastern Caribbean Sea. Measurements of the near-surface atmosphere are also collected to examine air-sea processes over the eddy. These novel measurements showcase temperature and salinity for the eddy and background flow, upper ocean stratification, a residing barrier layer (BL), velocity structure, and water mass characteristics. The eddy's thermal structure is alike that of WCEs in the Gulf of Mexico (GoM) whereas surrounding waters have relatively deeper isotherms compared to its GoM counterparts. Analyses suggest that upper ocean stratification within the study region is due to a BL. These are the first observations of a BL inside a WCE to the best of our knowledge. Reduced shear comparisons suggest that the upper ocean, especially within the WCE, would be more resistant to tropical cyclone (TC) induced mixing than the GoM because of the BL. The eddy is suspected to originate from North Brazil Current rings, given its fresh anomalies relative to climatology and surrounding waters and its trajectory prior to sampling. Atmospheric measurements suggest the WCE is influencing the lower atmosphere along its boundaries. These observations signify that not only does this WCE have deep thermal structure and modulate the near-surface atmosphere but it is unique because it has a BL. The findings and analyses suggest that a similar eddy could potentially influence air-sea processes, such as those during TC passage.

  6. Spectral and total temperature-dependent emissivities of few-layer structures on a metallic substrate.

    Science.gov (United States)

    Blandre, Etienne; Chapuis, Pierre-Olivier; Vaillon, Rodolphe

    2016-01-25

    We investigate the thermal radiative emission of few-layer structures deposited on a metallic substrate and its dependence on temperature with the Fluctuational Electrodynamics approach. We highlight the impact of the variations of the optical properties of metallic layers on their temperature-dependent emissivity. Fabry-Pérot spectral selection involving at most two transparent layers and one thin reflective layer leads to well-defined peaks and to the amplification of the substrate emission. For a single Fabry-Pérot layer on a reflective substrate, an optimal thickness that maximizes the emissivity of the structure can be determined at each temperature. A thin lossy layer deposited on the previous structure can enhance interference phenomena, and the analysis of the participation of each layer to the emission shows that the thin layer is the main source of emission. Eventually, we investigate a system with two Fabry-Pérot layers and a metallic thin layer, and we show that an optimal architecture can be found. The total hemispherical emissivity can be increased by one order of magnitude compared to the substrate emissivity.

  7. Carbon nanofiber layers on metal and carbon substrates : PEM fuel cell and microreactor applications

    NARCIS (Netherlands)

    Pacheco Benito, Sergio

    2011-01-01

    This thesis describes the preparation of CNF layers on flat and porous substrates and their application as catalyst supports for chemical and electrochemical gas‐liquidsolid (G‐L‐S) catalytic reactions. Metal nanoparticles growing CNFs on flat metal substrates at 600°C are easily formed from NiO, in

  8. Dynamic partitioning of nanoparticulate metal species between gel layers and aqueous media

    NARCIS (Netherlands)

    Veeken, van der P.L.R.

    2010-01-01

    This thesis deals with several aspects of the use of Diffusive Gradient in Thin film (DGT) and Diffusive Equilibriation in Thin film (DET) in dynamic metal speciation analysis. It has a clear focus on the properties of the diffusive gel layer, and their possible impact on metal speciation measuremen

  9. Dynamic partitioning of nanoparticulate metal species between gel layers and aqueous media

    NARCIS (Netherlands)

    Veeken, van der P.L.R.

    2010-01-01

    This thesis deals with several aspects of the use of Diffusive Gradient in Thin film (DGT) and Diffusive Equilibriation in Thin film (DET) in dynamic metal speciation analysis. It has a clear focus on the properties of the diffusive gel layer, and their possible impact on metal speciation

  10. Efficient, air-stable colloidal quantum dot solar cells encapsulated using atomic layer deposition of a nanolaminate barrier

    KAUST Repository

    Ip, Alexander H.

    2013-12-23

    Atomic layer deposition was used to encapsulate colloidal quantum dot solar cells. A nanolaminate layer consisting of alternating alumina and zirconia films provided a robust gas permeation barrier which prevented device performance degradation over a period of multiple weeks. Unencapsulated cells stored in ambient and nitrogen environments demonstrated significant performance losses over the same period. The encapsulated cell also exhibited stable performance under constant simulated solar illumination without filtration of harsh ultraviolet photons. This monolithically integrated thin film encapsulation method is promising for roll-to-roll processed high efficiency nanocrystal solar cells. © 2013 AIP Publishing LLC.

  11. Graphene layer encapsulated metal nanoparticles as a new type of non-precious metal catalysts for oxygen reduction

    DEFF Research Database (Denmark)

    Hu, Yang; Zhong, Lijie; Jensen, Jens Oluf

    2016-01-01

    Cheap and efficient non-precious metal catalysts for oxygen reduction have been a focus of research in the field of low-temperature fuel cells. This review is devoted to a brief summary of the recent work on a new type of catalysts, i.e., the graphene layer encapsulated metal nanoparticles....... The discussion is focused on the synthesis, structure, mechanism, performance, and further research....

  12. Using thin metal layers on composite structures for shielding the electromagnetic pulse caused by nearby lightning

    NARCIS (Netherlands)

    Blaj, M.A.; Buesink, F.J.K.; Damstra, G.C.; Leferink, F.B.J.

    2011-01-01

    Electronic systems in composite structures could be vulnerable to the (dominant magnetic) field caused by a lightning strike, because only thin layers of metal can be used on composite structures. Thin layers result in a very low shielding effectiveness against magnetic fields. Many experiments usin

  13. Sliding wear resistance of metal matrix composite layers prepared by high power laser

    NARCIS (Netherlands)

    Ocelik, Vaclav; Matthews, D; de Hosson, Jeff

    2005-01-01

    Two laser surface engineering techniques, Laser Cladding and Laser Melt Injection (LMI), were used to prepare three different metal matrix composite layers with a thickness of about 1 mm and approximately 25-30% volume fraction of ceramic particles. SiC/Al-8Si, WC/Ti-6Al-4V and TiB2/Ti-6Al-4V layers

  14. Lateral amorphous selenium metal-insulator-semiconductor-insulator-metal photodetectors using ultrathin dielectric blocking layers for dark current suppression

    Science.gov (United States)

    Chang, Cheng-Yi; Pan, Fu-Ming; Lin, Jian-Siang; Yu, Tung-Yuan; Li, Yi-Ming; Chen, Chieh-Yang

    2016-12-01

    We fabricated amorphous selenium (a-Se) photodetectors with a lateral metal-insulator-semiconductor-insulator-metal (MISIM) device structure. Thermal aluminum oxide, plasma-enhanced chemical vapor deposited silicon nitride, and thermal atomic layer deposited (ALD) aluminum oxide and hafnium oxide (ALD-HfO2) were used as the electron and hole blocking layers of the MISIM photodetectors for dark current suppression. A reduction in the dark current by three orders of magnitude can be achieved at electric fields between 10 and 30 V/μm. The effective dark current suppression is primarily ascribed to electric field lowering in the dielectric layers as a result of charge trapping in deep levels. Photogenerated carriers in the a-Se layer can be transported across the blocking layers to the Al electrodes via Fowler-Nordheim tunneling because a high electric field develops in the ultrathin dielectric layers under illumination. Since the a-Se MISIM photodetectors have a very low dark current without significant degradation in the photoresponse, the signal contrast is greatly improved. The MISIM photodetector with the ALD-HfO2 blocking layer has an optimal signal contrast more than 500 times the contrast of the photodetector without a blocking layer at 15 V/μm.

  15. Electroless nickel alloy deposition on SiO2 for application as a diffusion barrier and seed layer in 3D copper interconnect technology.

    Science.gov (United States)

    Kim, Tae-Yoo; Son, Hwa-Jin; Lim, Seung-Kyu; Song, Young-Il; Park, Hwa-Sun; Suh, Su-Jeong

    2014-12-01

    Electroless Ni-P films were investigated with the aim of application as barrier and seed layers in 3D interconnect technology. Different shapes of blind-via holes were fabricated with a deep reactive ion etcher and SiO2 formed on these holes as an insulating layer. The surface of the substrate has been made hydrophilic by O2 plasma treatment with 100 W of power for 20 min. Electroless Ni-P films were deposited as both a diffusion barrier and a seed layer for Cu filling process. Prior to plating, substrates were activated in a palladium chloride solution after sensitization in a tin chloride solution with various conditions in order to deposit uniform films in TSV. After the formation of the electroless barrier layer, electro Cu was plated directly on the barrier layer. Ni-P films fabricated in blind-via holes were observed by scanning electron microscope. Energy dispersive spectroscopy line scanning was carried out for evaluating the diffusion barrier properties of the Ni-P films. The electroless Ni-P layer worked well as a Cu diffusion barrier until 300 degrees C. However, Cu ions diffused into barrier layer when the annealing temperature increases over 400 degrees C.

  16. Research Update: Reactively sputtered nanometer-thin ZrN film as a diffusion barrier between Al and boron layers for radiation detector applications

    Science.gov (United States)

    Golshani, Negin; Mohammadi, V.; Schellevis, H.; Beenakker, C. I. M.; Ishihara, R.

    2014-10-01

    In this paper, optimization of the process flow for PureB detectors is investigated. Diffusion barrier layers between a boron layer and the aluminum interconnect can be used to enhance the performance and visual appearance of radiation detectors. Few nanometers-thin Zirconium Nitride (ZrN) layer deposited by reactive sputtering in a mixture of Ar/N2, is identified as a reliable diffusion barrier with better fabrication process compatibility than others. The barrier properties of this layer have been tested for different boron layers deposited at low and high temperatures with extensive optical microscopy analyses, electron beam induced current, SEM, and electrical measurements. This study demonstrated that spiking behavior of pure Al on Si can be prevented by the thin ZrN layer thus improving the performance of the radiation detectors fabricated using boron layer.

  17. Research Update: Reactively sputtered nanometer-thin ZrN film as a diffusion barrier between Al and boron layers for radiation detector applications

    Energy Technology Data Exchange (ETDEWEB)

    Golshani, Negin, E-mail: negingolshani@gmail.com; Mohammadi, V.; Schellevis, H.; Beenakker, C. I. M.; Ishihara, R. [ECTM, DIMES, Faculty of Electrical Engineering (EWI), Delft University of Technology (TU Delft), Feldmannweg 17, P.O. Box 5053, 2628 CT Delft (Netherlands)

    2014-10-01

    In this paper, optimization of the process flow for PureB detectors is investigated. Diffusion barrier layers between a boron layer and the aluminum interconnect can be used to enhance the performance and visual appearance of radiation detectors. Few nanometers-thin Zirconium Nitride (ZrN) layer deposited by reactive sputtering in a mixture of Ar/N{sub 2}, is identified as a reliable diffusion barrier with better fabrication process compatibility than others. The barrier properties of this layer have been tested for different boron layers deposited at low and high temperatures with extensive optical microscopy analyses, electron beam induced current, SEM, and electrical measurements. This study demonstrated that spiking behavior of pure Al on Si can be prevented by the thin ZrN layer thus improving the performance of the radiation detectors fabricated using boron layer.

  18. Research Update: Reactively sputtered nanometer-thin ZrN film as a diffusion barrier between Al and boron layers for radiation detector applications

    Directory of Open Access Journals (Sweden)

    Negin Golshani

    2014-10-01

    Full Text Available In this paper, optimization of the process flow for PureB detectors is investigated. Diffusion barrier layers between a boron layer and the aluminum interconnect can be used to enhance the performance and visual appearance of radiation detectors. Few nanometers-thin Zirconium Nitride (ZrN layer deposited by reactive sputtering in a mixture of Ar/N2, is identified as a reliable diffusion barrier with better fabrication process compatibility than others. The barrier properties of this layer have been tested for different boron layers deposited at low and high temperatures with extensive optical microscopy analyses, electron beam induced current, SEM, and electrical measurements. This study demonstrated that spiking behavior of pure Al on Si can be prevented by the thin ZrN layer thus improving the performance of the radiation detectors fabricated using boron layer.

  19. Electron emission from a double-layer metal under femtosecond laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shuchang; Li, Suyu; Jiang, Yuanfei; Chen, Anmin, E-mail: amchen@jlu.edu.cn; Ding, Dajun; Jin, Mingxing, E-mail: mxjin@jlu.edu.cn

    2015-01-01

    In this paper we theoretically investigate electron emission during femtosecond laser ablation of single-layer metal (copper) and double-layer structures. The double-layer structure is composed of a surface layer (copper) and a substrate layer (gold or chromium). The calculated results indicate that the double-layer structure brings a change to the electron emission from the copper surface. Compared with the ablation of a single-layer, a double-layer structure may be helpful to decrease the relaxation time of the electron temperature, and optimize the electron emission by diminishing the tailing phenomenon under the same absorbed laser fluence. With the increase of the absorbed laser fluence, the effect of optimization becomes significant. This study provides a way to optimize the electron emission which can be beneficial to generate laser induced ultrafast electron pulse sources.

  20. Oral Administration of Probiotics Inhibits Absorption of the Heavy Metal Cadmium by Protecting the Intestinal Barrier.

    Science.gov (United States)

    Zhai, Qixiao; Tian, Fengwei; Zhao, Jianxin; Zhang, Hao; Narbad, Arjan; Chen, Wei

    2016-07-15

    The heavy metal cadmium (Cd) is an environmental pollutant that causes adverse health effects in humans and animals. Our previous work demonstrated that oral administration of probiotics can significantly inhibit Cd absorption in the intestines of mice, but further evidence is needed to gain insights into the related protection mode. The goal of this study was to evaluate whether probiotics can inhibit Cd absorption through routes other than the Cd binding, with a focus on gut barrier protection. In the in vitro assay, both the intervention and therapy treatments of Lactobacillus plantarum CCFM8610 alleviated Cd-induced cytotoxicity in the human intestinal cell line HT-29 and protected the disruption of tight junctions in the cell monolayers. In a mouse model, probiotics with either good Cd-binding or antioxidative ability increased fecal Cd levels and decreased Cd accumulation in the tissue of Cd-exposed mice. Compared with the Cd-only group, cotreatment with probiotics also reversed the disruption of tight junctions, alleviated inflammation, and decreased the intestinal permeability of mice. L. plantarum CCFM8610, a strain with both good Cd binding and antioxidative abilities, exhibited significantly better protection than the other two strains. These results suggest that along with initial intestinal Cd sequestration, probiotics can inhibit Cd absorption by protecting the intestinal barrier, and the protection is related to the alleviation of Cd-induced oxidative stress. A probiotic with both good Cd-binding and antioxidative capacities can be used as a daily supplement for the prevention of oral Cd exposure. The heavy metal cadmium (Cd) is an environmental pollutant that causes adverse health effects in humans and animals. For the general population, food and drinking water are the main sources of Cd exposure due to the biomagnification of Cd within the food chain; therefore, the intestinal tract is the first organ that is susceptible to Cd contamination

  1. Improved Performance of Pentacene Organic Field-Effect Transistors by Inserting a V2O5 Metal Oxide Layer

    Institute of Scientific and Technical Information of China (English)

    赵赓; 程晓曼; 田海军; 杜博群; 梁晓宇

    2011-01-01

    We fabricate pentacene-based organic field effect transistors(OFETs),inserting a transition metal oxide(V2 O5)layer between the pentacene and Al source-drain(S/D)electrodes.The performance of the devices with V2O5/AlS/D electrodes is considerably improved compared to the pentacene-based OFET with only Al S/D electrodes.After the 10-nm V2O5 layer modification,the effective field-effect mobility of the devices increases from 2.7 ×10-3 cm2 /V.s to 8.93 × 10-1 cm2 /V.s.Owing to the change of the injection property,the effective threshold voltage (Vth)is changed from-7.5 V to-5 V and the on/off ratio shifts from 102 to 104.Moreover,the dispersion of sub-threshold current in the devices disappears.These performance improvements are ascribed to the low carrier injection barrier and the reduction of contact resistance.It is indicated that V2O5 layer modification is an effective approach to improve pentacene-based OFET performance.%We fabricate pentacene-based organic field effect transistors (OFETs), inserting a transition metal oxide (V2O5) layer between the pentacene and Al source-drain (S/D) electrodes. The performance of the devices with V2 O5/AI S/D electrodes is considerably improved compared to the pentacene-based OFET with only Al S/D electrodes. After the 10-nm V2O5 layer modification, the effective field-effect mobility of the devices increases from 2.7 x 10~3 cm2/V-s to 8.93x10-1 cm2/V-s. Owing to the change of the injection property, the effective threshold voltage (Vth) is changed from -7.5 V to -5 V and the on/off ratio shifts from l02 to 104. Moreover, the dispersion of sub-threshold current in the devices disappears. These performance improvements are ascribed to the low carrier injection barrier and the reduction of contact resistance. It is indicated that V2O5 layer modification is an effective approach to improve pentacene-based OFET performance.

  2. Pervious concrete reactive barrier for removal of heavy metals from acid mine drainage - column study.

    Science.gov (United States)

    Shabalala, Ayanda N; Ekolu, Stephen O; Diop, Souleymane; Solomon, Fitsum

    2017-02-05

    This paper presents a column study conducted to investigate the potential use of pervious concrete as a reactive barrier for treatment of water impacted by mine waste. The study was done using acid mine drainage (AMD) collected from a gold mine (WZ) and a coalfield (TDB). Pervious concrete mixtures consisting of Portland cement CEM I 52.5R with or without 30% fly ash (FA) were prepared at a water-cementitious ratio of 0.27 then used to make cubes which were employed in the reactor columns. It was found that the removal efficiency levels of Al, Fe, Mn, Co and Ni were 75%, 98%, 99%, 94% and 95% for WZ; 87%, 96%, 99%, 98% and 90% for TDB, respectively. The high rate of acid reduction and metal removal by pervious concrete is attributed to dissolution of portlandite which is a typical constituent of concrete. The dominant reaction product in all four columns was gypsum, which also contributed to some removal of sulphate from AMD. Formation of gypsum, goethite, and Glauber's salt were identified. Precipitation of metal hydroxides seems to be the dominant metal removal mechanism. Use of pervious concrete offers a promising alternative treatment method for polluted or acidic mine water. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Atomic-Scale Tuning of Layered Binary Metal Oxides for High Temperature Moving Assemblies

    Science.gov (United States)

    2015-06-01

    AFRL-OSR-VA-TR-2015-0166 Atomic -Scale Tuning of Layered Binary Metal OxideS ASHLIE MARTINI UNIVERSITY OF CALIFORNIA MERCED Final Report 06/01/2015...COVERED (From - To)      01-05-2012 to 30-04-2015 4.  TITLE AND SUBTITLE Atomic -Scale Tuning of Layered Binary Metal Oxides for High Temperature Moving...understand, at an atomic level, the material properties that influence the thermal, mechanical and tribological behavior of intrinsically layered binary

  4. Layer-by-Layer Deposition with Polymers Containing Nitrilotriacetate, A Convenient Route to Fabricate Metal- and Protein-Binding Films.

    Science.gov (United States)

    Wijeratne, Salinda; Liu, Weijing; Dong, Jinlan; Ning, Wenjing; Ratnayake, Nishanka Dilini; Walker, Kevin D; Bruening, Merlin L

    2016-04-27

    This paper describes a convenient synthesis of nitrilotriacetate (NTA)-containing polymers and subsequent layer-by-layer adsorption of these polymers on flat surfaces and in membrane pores. The resulting films form NTA-metal-ion complexes and capture 2-3 mmol of metal ions per mL of film. Moreover, these coatings bind multilayers of polyhistidine-tagged proteins through association with NTA-metal-ion complexes. Inclusion of acrylic acid repeat units in NTA-containing copolymers promotes swelling to increase protein binding in films on Au-coated wafers. Adsorption of NTA-containing films in porous nylon membranes gives materials that capture ∼46 mg of His-tagged ubiquitin per mL. However, the binding capacity decreases with the protein molecular weight. Due to the high affinity of NTA for metal ions, the modified membranes show modest leaching of Ni(2+) in binding and rinsing buffers. Adsorption of NTA-containing polymers is a simple method to create metal- and protein-binding films and may, with future enhancement of stability, facilitate development of disposable membranes that rapidly purify tagged proteins.

  5. Formation and manipulation of regular metallic nanoparticle arrays on bacterial surface layers: an advanced TEM study

    Science.gov (United States)

    Mertig, M.; Wahl, R.; Lehmann, M.; Simon, P.; Pompe, W.

    The template-directed formation of regular nanoparticle arrays on two-dimensional crystalline protein layers after their treatment with metal salt complexes was studied by transmission electron microscopy. For these investigations, bacterial surface layers (S layers), recrystallized in vitro into sheets and tube-shaped protein crystals with typical dimensions in the micrometer range, were used as the template. As identified by electron holography and scanning force microscopy, the S-layer tubes form alternating double layers when deposited onto a solid substrate surface. Two distinct pathways for the metal particle formation at the templates have been found: the site-specific growth of metal clusters by chemical reduction of the metal salt complexes, and the electron-beam induced growth of nanoparticles in the transmission electron microscope. Both mechanisms lead to regular arrays with particle densities > 6×1011cm-2. Nanoparticle formation by electron exposure takes exclusively place in the flat-lying double-layered protein tubes, where a sufficient amount of metal complexes can be accumulated during sample preparation.

  6. Experimental Study on the Effect of Late-Phase Coolant Injection on the Metallic Layer

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Kyoung Ho; Park, Rae Joon; Cho, Young Ro; Kim, Sang Baik; Hong, Seong Wan; Kim, Hee Dong

    2007-04-15

    Sustained heating experiments, named ELIAS (Experiments on Late-phase coolant Injection to ASsess the mitigation of focusing effect of metallic layer), were performed to quantify the boiling heat removal rate at the upper surface of a metallic layer for precise evaluations on the effect of a late in-vessel coolant injection. Heat fluxes from the melt layer to the water pool varied from 250 to 550kW/m2 depending on the experimental conditions. Comparison of boiling heat fluxes between the ELIAS experiments and the calculation using the Berenson's film boiling correlation shows that effective heat removal was accomplished via late-phase coolant injection in the ELIAS experiments. In this study, simple model was developed to evaluate the mitigation of focusing effect in the metallic layer via late-phase coolant injection. The ELIAS experimental data on the heat transfer rate at the upper surface of the metallic layer were used as input data in the simple model. The calculation results for the large break loss of coolant accident in the APR1400 show that the risk induced by the focusing effect is highly dependent on the metallic layer thickness and the integrity of the reactor pressure vessel can be enhanced via late-phase coolant injection.

  7. Tunable Optical Nanocavity of Iron-garnet with a Buried Metal Layer

    Directory of Open Access Journals (Sweden)

    Alexey N. Kuz'michev

    2015-05-01

    Full Text Available We report on the fabrication and characterization of a novel magnetophotonic structure designed as iron garnet based magneto-optical nanoresonator cavity constrained by two noble metal mirrors. Since the iron garnet layer requires annealing at high temperatures, the fabrication process can be rather challenging. Special approaches for the protection of metal layers against oxidation and morphological changes along with a special plasma-assisted polishing of the iron garnet layer surface were used to achieve a 10-fold enhancement of the Faraday rotation angle (up to 10.8\\(^{\\circ}/\\mu\\m within a special resonance peak of 12 nm (FWHM linewidth at a wavelength of 772 nm, in the case of a resonator with two silver mirrors. These structures are promising for tunable nanophotonics applications, in particular, they can be used as magneto-optical (MO metal-insulator-metal waveguides and modulators.

  8. Double-Layer Gadolinium Zirconate/Yttria-Stabilized Zirconia Thermal Barrier Coatings Deposited by the Solution Precursor Plasma Spray Process

    Science.gov (United States)

    Jiang, Chen; Jordan, Eric H.; Harris, Alan B.; Gell, Maurice; Roth, Jeffrey

    2015-08-01

    Advanced thermal barrier coatings (TBCs) with lower thermal conductivity, increased resistance to calcium-magnesium-aluminosilicate (CMAS), and improved high-temperature capability, compared to traditional yttria-stabilized zirconia (YSZ) TBCs, are essential to higher efficiency in next generation gas turbine engines. Double-layer rare-earth zirconate/YSZ TBCs are a promising solution. From a processing perspective, solution precursor plasma spray (SPPS) process with its unique and beneficial microstructural features can be an effective approach to obtaining the double-layer microstructure. Previously durable low-thermal-conductivity YSZ TBCs with optimized layered porosity, called the inter-pass boundaries (IPBs) were produced using the SPPS process. In this study, an SPPS gadolinium zirconate (GZO) protective surface layer was successfully added. These SPPS double-layer TBCs not only retained good cyclic durability and low thermal conductivity, but also demonstrated favorable phase stability and increased surface temperature capabilities. The CMAS resistance was evaluated with both accumulative and single applications of simulated CMAS in isothermal furnaces. The double-layer YSZ/GZO exhibited dramatic improvement in the single application, but not in the continuous one. In addition, to explore their potential application in integrated gasification combined cycle environments, double-layer TBCs were tested under high-temperature humidity and encouraging performance was recorded.

  9. Accuracy of Young's Modulus of Thermal Barrier Coating Layer Determined by Bending Resonance of a Multilayered Specimen

    Science.gov (United States)

    Waki, Hiroyuki; Takizawa, Kensuke; Kato, Masahiko; Takahashi, Satoru

    2016-04-01

    The Young's modulus of individual layer in thermal barrier coating (TBC) system is an important mechanical property because it allows determining the parameters of materials mechanics in the TBC system. In this study, we investigated the accuracy of the evaluation method for the Young's modulus of a TBC layer according to the first bending resonance of a multilayered specimen comprising a substrate, bond coating, and TBC. First, we derived a closed-form solution for the Young's modulus of the TBC layer using the equation of motion for the bending vibration of a composite beam. The solution for the three-layered model provided the Young's modulus of the TBC layer according to the measured resonance frequency and the known values for the dimensions, mass, and Young's moduli of all the other layers. Next, we analyzed the sensitivity of these input errors to the evaluated Young's modulus and revealed the important inputs for accurate evaluation. Finally, we experimentally confirmed that the Young's modulus of the TBC layer was obtained accurately by the developed method.

  10. Ultra-thin Metal and Dielectric Layers for Nanophotonic Applications

    DEFF Research Database (Denmark)

    Shkondin, Evgeniy; Leandro, Lorenzo; Malureanu, Radu;

    2015-01-01

    In our talk we first give an overview of the various thin films used in the field of nanophotonics. Then we describe our own activity in fabrication and characterization of ultra-thin films of high quality. We particularly focus on uniform gold layers having thicknesses down to 6 nm fabricated by......-beam deposition on dielectric substrates and Al-oxides/Ti-oxides multilayers prepared by atomic layer deposition in high aspect ratio trenches. In the latter case we show more than 1:20 aspect ratio structures can be achieved....

  11. Schottky barrier heights at the interfaces between pure-phase InAs nanowires and metal contacts

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Boyong; Huang, Shaoyun, E-mail: syhuang@pku.edu.cn, E-mail: hqxu@pku.edu.cn; Wang, Jiyin [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Pan, Dong; Zhao, Jianghua [State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Xu, H. Q., E-mail: syhuang@pku.edu.cn, E-mail: hqxu@pku.edu.cn [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Division of Solid-State Physics, Lund University, Box 118, S-221 00 Lund (Sweden)

    2016-02-07

    Understanding of the Schottky barriers formed at metal contact-InAs nanowire interfaces is of great importance for the development of high-performance InAs nanowire nanoelectronic and quantum devices. Here, we report a systematical study of InAs nanowire field-effect transistors (FETs) and the Schottky barrier heights formed at the contact-nanowire interfaces. The InAs nanowires employed are grown by molecular beam epitaxy and are high material quality single crystals, and the devices are made by directly contacting the nanowires with a series of metals of different work functions. The fabricated InAs nanowire FET devices are characterized by electrical measurements at different temperatures and the Schottky barrier heights are extracted from the measured temperature and gate-voltage dependences of the channel current. We show that although the work functions of the contact metals are widely spread, the Schottky barrier heights are determined to be distributed over 35–55 meV, showing a weak but not negligible dependence on the metals. The deduced Fermi level in the InAs nanowire channels is found to be in the band gap and very close to the conduction band. The physical origin of the results is discussed in terms of Fermi level pinning by the surface states of the InAs nanowires and a shift in pinned Fermi level induced by the metal-related interface states.

  12. Metallic layer-by-layer photonic crystals for linearly-polarized thermal emission and thermophotovoltaic device including same

    Science.gov (United States)

    Lee, Jae-Hwang; Ho, Kai-Ming; Constant, Kristen P.

    2016-07-26

    Metallic thermal emitters consisting of two layers of differently structured nickel gratings on a homogeneous nickel layer are fabricated by soft lithography and studied for polarized thermal radiation. A thermal emitter in combination with a sub-wavelength grating shows a high extinction ratio, with a maximum value close to 5, in a wide mid-infrared range from 3.2 to 7.8 .mu.m, as well as high emissivity up to 0.65 at a wavelength of 3.7 .mu.m. All measurements show good agreement with theoretical predictions. Numerical simulations reveal that a high electric field exists within the localized air space surrounded by the gratings and the intensified electric-field is only observed for the polarizations perpendicular to the top sub-wavelength grating. This result suggests how the emissivity of a metal can be selectively enhanced at a certain range of wavelengths for a given polarization.

  13. Metallic layer-by-layer photonic crystals for linearly-polarized thermal emission and thermophotovoltaic device including same

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae-Hwang; Ho, Kai-Ming; Constant, Kristen P.

    2016-07-26

    Metallic thermal emitters consisting of two layers of differently structured nickel gratings on a homogeneous nickel layer are fabricated by soft lithography and studied for polarized thermal radiation. A thermal emitter in combination with a sub-wavelength grating shows a high extinction ratio, with a maximum value close to 5, in a wide mid-infrared range from 3.2 to 7.8 .mu.m, as well as high emissivity up to 0.65 at a wavelength of 3.7 .mu.m. All measurements show good agreement with theoretical predictions. Numerical simulations reveal that a high electric field exists within the localized air space surrounded by the gratings and the intensified electric-field is only observed for the polarizations perpendicular to the top sub-wavelength grating. This result suggests how the emissivity of a metal can be selectively enhanced at a certain range of wavelengths for a given polarization.

  14. Controlling terahertz radiation with nanoscale metal barriers embedded in nano slot antennas.

    Science.gov (United States)

    Park, Hyeong-Ryeol; Bahk, Young-Mi; Ahn, Kwang Jun; Park, Q-Han; Kim, Dai-Sik; Martín-Moreno, Luis; García-Vidal, Francisco J; Bravo-Abad, Jorge

    2011-10-25

    Nanoscale metallic barriers embedded in terahertz (THz) slot antennas are shown to provide unprecedented control of the transition state arising at the crossover between the full- and half-wavelength resonant modes of such antennas. We demonstrate strong near-field coupling between two paired THz slot antennas separated by a 5 nm wide nanobarrier, almost fully inducing the shift to the resonance of the double-length slot antenna. This increases by a factor of 50 the length-scale needed to observe similar coupling strengths in conventional air-gap antennas (around 0.1 nm), making the transition state readily accessible to experiment. Our measurements are in good agreement with a quantitative theoretical modeling, which also provides a simple physical picture of our observations.

  15. Thin-film metallic glass: an effective diffusion barrier for Se-doped AgSbTe2 thermoelectric modules

    Science.gov (United States)

    Yu, Chia-Chi; Wu, Hsin-Jay; Deng, Ping-Yuan; Agne, Matthias T.; Snyder, G. Jeffrey; Chu, Jinn P.

    2017-03-01

    The thermal stability of joints in thermoelectric (TE) modules, which are degraded during interdiffusion between the TE material and the contacting metal, needs to be addressed in order to utilize TE technology for competitive, sustainable energy applications. Herein, we deposit a 200 nm-thick Zr-based thin-film metallic glass (TFMG), which acts as an effective diffusion barrier layer with low electrical contact resistivity, on a high-zT Se-doped AgSbTe2 substrate. The reaction couples structured with TFMG/TE are annealed at 673 K for 8-360 hours and analyzed by electron microscopy. No observable IMCs (intermetallic compounds) are formed at the TFMG/TE interface, suggesting the effective inhibition of atomic diffusion that may be attributed to the grain-boundary-free structure of TFMG. The minor amount of Se acts as a tracer species, and a homogeneous Se-rich region is found nearing the TFMG/TE interface, which guarantees satisfactory bonding at the joint. The diffusion of Se, which has the smallest atomic volume of all the elements from the TE substrate, is found to follow Fick’s second law. The calculated diffusivity (D) of Se in TFMG falls in the range of D~10-20-10-23(m2/s), which is 106~107 and 1012~1013 times smaller than those of Ni [10-14-10-17(m2/s)] and Cu [10-8-10-11(m2/s)] in Bi2Te3, respectively.

  16. Thin-film metallic glass: an effective diffusion barrier for Se-doped AgSbTe2 thermoelectric modules

    Science.gov (United States)

    Yu, Chia-Chi; Wu, Hsin-jay; Deng, Ping-Yuan; Agne, Matthias T.; Snyder, G. Jeffrey; Chu, Jinn P.

    2017-01-01

    The thermal stability of joints in thermoelectric (TE) modules, which are degraded during interdiffusion between the TE material and the contacting metal, needs to be addressed in order to utilize TE technology for competitive, sustainable energy applications. Herein, we deposit a 200 nm-thick Zr-based thin-film metallic glass (TFMG), which acts as an effective diffusion barrier layer with low electrical contact resistivity, on a high-zT Se-doped AgSbTe2 substrate. The reaction couples structured with TFMG/TE are annealed at 673 K for 8–360 hours and analyzed by electron microscopy. No observable IMCs (intermetallic compounds) are formed at the TFMG/TE interface, suggesting the effective inhibition of atomic diffusion that may be attributed to the grain-boundary-free structure of TFMG. The minor amount of Se acts as a tracer species, and a homogeneous Se-rich region is found nearing the TFMG/TE interface, which guarantees satisfactory bonding at the joint. The diffusion of Se, which has the smallest atomic volume of all the elements from the TE substrate, is found to follow Fick’s second law. The calculated diffusivity (D) of Se in TFMG falls in the range of D~10−20–10−23(m2/s), which is 106~107 and 1012~1013 times smaller than those of Ni [10−14–10−17(m2/s)] and Cu [10−8–10−11(m2/s)] in Bi2Te3, respectively.

  17. Copper Benzenetricarboxylate Metal-Organic Framework Nucleation Mechanisms on Metal Oxide Powders and Thin Films formed by Atomic Layer Deposition.

    Science.gov (United States)

    Lemaire, Paul C; Zhao, Junjie; Williams, Philip S; Walls, Howard J; Shepherd, Sarah D; Losego, Mark D; Peterson, Gregory W; Parsons, Gregory N

    2016-04-13

    Chemically functional microporous metal-organic framework (MOF) crystals are attractive for filtration and gas storage applications, and recent results show that they can be immobilized on high surface area substrates, such as fiber mats. However, fundamental knowledge is still lacking regarding initial key reaction steps in thin film MOF nucleation and growth. We find that thin inorganic nucleation layers formed by atomic layer deposition (ALD) can promote solvothermal growth of copper benzenetricarboxylate MOF (Cu-BTC) on various substrate surfaces. The nature of the ALD material affects the MOF nucleation time, crystal size and morphology, and the resulting MOF surface area per unit mass. To understand MOF nucleation mechanisms, we investigate detailed Cu-BTC MOF nucleation behavior on metal oxide powders and Al2O3, ZnO, and TiO2 layers formed by ALD on polypropylene substrates. Studying both combined and sequential MOF reactant exposure conditions, we find that during solvothermal synthesis ALD metal oxides can react with the MOF metal precursor to form double hydroxy salts that can further convert to Cu-BTC MOF. The acidic organic linker can also etch or react with the surface to form MOF from an oxide metal source, which can also function as a nucleation agent for Cu-BTC in the mixed solvothermal solution. We discuss the implications of these results for better controlled thin film MOF nucleation and growth.

  18. Schottky-barrier heights of metal/alpha-SiC{l_brace}0001{r_brace} interfaces by first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Shingo; Okazaki, Kazuyuki; Kohyama, Masanori [Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, Osaka 5638577 (Japan); Tamura, Tomoyuki; Ishibashi, Shoji [Research Institute for Computational Sciences, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 3058568 (Japan)

    2007-07-01

    Atomic and electronic structures and Schottky barrier heights (SBH) of multi-layer metal (=Al, Ti, Fe, Co, Ni, Cu, Pt and Au)/6H-SiC{l_brace}0001{r_brace} interfaces have been calculated by the projector augmented wave (PAW) method. The p-type SBHs of the C-terminated interfaces are smaller than those of the Si-terminated ones due to the different interface dipoles. About the dependence on the metal species, the SBHs of the Si-terminated interfaces range within a relatively narrow energy region because of more metallic characters, although those of the C-terminated ones show clearer dependence, where the SBHs decrease for the increment of metal electronegativity or work function. This inverse proportion is different from the results of monolayer metal/SiC interfaces, while consistent with experiments. All the results can be explained by the viewpoint of the interface dipole and the intrinsic relation of the band structures. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Anticipated Degradation Modes of Metallic Engineered Barriers for High-Level Nuclear Waste Repositories

    Science.gov (United States)

    Rodríguez, Martín A.

    2014-03-01

    Metallic engineered barriers must provide a period of absolute containment to high-level radioactive waste in geological repositories. Candidate materials include copper alloys, carbon steels, stainless steels, nickel alloys, and titanium alloys. The national programs of nuclear waste management have to identify and assess the anticipated degradation modes of the selected materials in the corresponding repository environment, which evolves in time. Commonly assessed degradation modes include general corrosion, localized corrosion, stress-corrosion cracking, hydrogen-assisted cracking, and microbiologically influenced corrosion. Laboratory testing and modeling in metallurgical and environmental conditions of similar and higher aggressiveness than those expected in service conditions are used to evaluate the corrosion resistance of the materials. This review focuses on the anticipated degradation modes of the selected or reference materials as corrosion-resistant barriers in nuclear repositories. These degradation modes depend not only on the selected alloy but also on the near-field environment. The evolution of the near-field environment varies for saturated and unsaturated repositories considering backfilled and unbackfilled conditions. In saturated repositories, localized corrosion and stress-corrosion cracking may occur in the initial aerobic stage, while general corrosion and hydrogen-assisted cracking are the main degradation modes in the anaerobic stage. Unsaturated repositories would provide an oxidizing environment during the entire repository lifetime. Microbiologically influenced corrosion may be avoided or minimized by selecting an appropriate backfill material. Radiation effects are negligible provided that a thick-walled container or an inner shielding container is used.

  20. Multistep soft chemistry method for valence reduction in transition metal oxides with triangular (CdI2-type) layers.

    Science.gov (United States)

    Blakely, Colin K; Bruno, Shaun R; Poltavets, Viktor V

    2014-03-14

    Transition metal (M) oxides with MO2 triangular layers demonstrate a variety of physical properties depending on the metal oxidation states. In the known compounds, metal oxidation states are limited to either 3+ or mixed-valent 3+/4+. A multistep soft chemistry synthetic route for novel phases with M(2+/3+)O2 triangular layers is reported.

  1. Spin Transport in Single Layer Transition Metal Dichalcogenides

    Science.gov (United States)

    Phillips, Michael; Aji, Vivek

    Inversion symmetry breaking and strong spin orbit coupling in two dimensional transition metal dichalcogenides leads to interesting new phenomena such as the valley hall and spin hall effects. The nontrivial Berry curvature of the bands yields transverse spin currents in applied field. In this talk we characterize the spin transport in hole-doped systems. Due to the large spin-splitting, time-reversal invariance, and the large separation of hole pockets in momentum space, spin flip scattering involves inter-valley processes with large momentum. As such, one expects large spin life times and a large spin hall angle. We analyze the robustness of the phenomena to various scattering processes and explore the viability of transition metal dichalcogenides for spintronic applications. We acknowledge the support of the NSF via Grant NSF DMR-1506707.

  2. Anisotropy Characteristics of Magnetostatic Surface Wave Propagating in YIG/Dielectric/Metal Layered Structure

    Institute of Scientific and Technical Information of China (English)

    Qing-Hui Yang; Huai-Wu Zhang; Ying-Li Liu

    2007-01-01

    The anisotropy of magnetostatic surface wave (MSSW) propagating in finite width YIG/dielectric/metal layered structure is analyzed. This problem is solved by finding the rigorous solution of each layer from Maxwell equation and the appropriate transmission Green's function matrix (G). From the relationship of Green's function matrixes of dielectric layer and ferrite layer, the dispersion equation is obtained.The MSSW filter is designed to verify the dispersion characteristics. The experiment results are in good agreement with the calculating data from the model.

  3. Reflection of Electromagnetic Waves by a Nonuniform Plasma Layer Covering a Metal Surface

    Institute of Scientific and Technical Information of China (English)

    GAO Hong-Mei; FA Peng-Ting

    2008-01-01

    Reflection coefficients of electromagnetic waves in a nonuniform plasma layer with electrons, positive ions and negative ions, covering a metal surface are investigated by using the finite-difference-time-domain method. It is shown that the reflection coefficients are influenced greatly by the density gradient on the layer edge, layer thickness and electron proportion, i.e., the effect of the negative ions. It is also found that low reflection or high attenuation can be reached by properly choosing high electron proportion, thick plasma layer, and smooth density gradient in the low frequency regime, but sharp density gradient in the high frequency regime.

  4. A Theoretical Model for Predicting Residual Stress Generation in Fabrication Process of Double-Ceramic-Layer Thermal Barrier Coating System.

    Science.gov (United States)

    Song, Yan; Wu, Weijie; Xie, Feng; Liu, Yilun; Wang, Tiejun

    2017-01-01

    Residual stress arisen in fabrication process of Double-Ceramic-Layer Thermal Barrier Coating System (DCL-TBCs) has a significant effect on its quality and reliability. In this work, based on the practical fabrication process of DCL-TBCs and the force and moment equilibrium, a theoretical model was proposed at first to predict residual stress generation in its fabrication process, in which the temperature dependent material properties of DCL-TBCs were incorporated. Then, a Finite Element method (FEM) has been carried out to verify our theoretical model. Afterwards, some important geometric parameters for DCL-TBCs, such as the thickness ratio of stabilized Zirconia (YSZ, ZrO2-8%Y2O3) layer to Lanthanum Zirconate (LZ, La2Zr2O7) layer, which is adjustable in a wide range in the fabrication process, have a remarkable effect on its performance, therefore, the effect of this thickness ratio on residual stress generation in the fabrication process of DCL-TBCs has been systematically studied. In addition, some thermal spray treatment, such as the pre-heating treatment, its effect on residual stress generation has also been studied in this work. It is found that, the final residual stress mainly comes from the cooling down process in the fabrication of DCL-TBCs. Increasing the pre-heating temperature can obviously decrease the magnitude of residual stresses in LZ layer, YSZ layer and substrate. With the increase of the thickness ratio of YSZ layer to LZ layer, magnitudes of residual stresses arisen in LZ layer and YSZ layer will increase while residual stress in substrate will decrease.

  5. A Theoretical Model for Predicting Residual Stress Generation in Fabrication Process of Double-Ceramic-Layer Thermal Barrier Coating System

    Science.gov (United States)

    Song, Yan; Wu, Weijie; Xie, Feng; Liu, Yilun; Wang, Tiejun

    2017-01-01

    Residual stress arisen in fabrication process of Double-Ceramic-Layer Thermal Barrier Coating System (DCL-TBCs) has a significant effect on its quality and reliability. In this work, based on the practical fabrication process of DCL-TBCs and the force and moment equilibrium, a theoretical model was proposed at first to predict residual stress generation in its fabrication process, in which the temperature dependent material properties of DCL-TBCs were incorporated. Then, a Finite Element method (FEM) has been carried out to verify our theoretical model. Afterwards, some important geometric parameters for DCL-TBCs, such as the thickness ratio of stabilized Zirconia (YSZ, ZrO2-8%Y2O3) layer to Lanthanum Zirconate (LZ, La2Zr2O7) layer, which is adjustable in a wide range in the fabrication process, have a remarkable effect on its performance, therefore, the effect of this thickness ratio on residual stress generation in the fabrication process of DCL-TBCs has been systematically studied. In addition, some thermal spray treatment, such as the pre-heating treatment, its effect on residual stress generation has also been studied in this work. It is found that, the final residual stress mainly comes from the cooling down process in the fabrication of DCL-TBCs. Increasing the pre-heating temperature can obviously decrease the magnitude of residual stresses in LZ layer, YSZ layer and substrate. With the increase of the thickness ratio of YSZ layer to LZ layer, magnitudes of residual stresses arisen in LZ layer and YSZ layer will increase while residual stress in substrate will decrease. PMID:28103275

  6. Layer-by-layer Assembly of Noble Metal Nanoparticles on Glassy Carbon Electrode

    Institute of Scientific and Technical Information of China (English)

    CHEN Da; ZHENG Long-Zhen

    2008-01-01

    Silver,gold,platinum and palladium nanoparticles were initially prepared in the AOT[sodium bis(2-ethylhexyl)-sulfosuccinate]micelle and characterized by ultraviolet-visible spectroscopy,transmission electron macroscopy,X-ray diffraction,Fourier transform-infrared spectroscopy,and zeta potential analysis.The negatively charged Pt nanoparticles were self-assembled on a glassy carbon electrode by a layer-by-layer method and the modified electrode electrocatalytic reactivity toward methanol oxidation was studied.

  7. Enhancing current-induced torques by abutting additional spin polarizer layer to nonmagnetic metal layer

    Science.gov (United States)

    Go, Gyungchoon; Lee, Kyung-Jin; Kim, Young Keun

    2017-04-01

    Recently, the switching of a perpendicularly magnetized ferromagnet (FM) by injecting an in-plane current into an attached non-magnet (NM) has become of emerging technological interest. This magnetization switching is attributed to the spin-orbit torque (SOT) originating from the strong spin-orbit coupling of the NM layer. However, the switching efficiency of the NM/FM structure itself may be insufficient for practical use, as for example, in spin transfer torque (STT)-based magnetic random access memory (MRAM) devices. Here we investigate spin torque in an NM/FM structure with an additional spin polarizer (SP) layer abutted to the NM layer. In addition to the SOT contribution, a spin-polarized current from the SP layer creates an extra spin chemical potential difference at the NM/FM interface and gives rise to a STT on the FM layer. We show that, using typical parameters including device width, thickness, spin diffusion length, and the spin Hall angle, the spin torque from the SP layer can be much larger than that from the spin Hall effect (SHE) of the NM.

  8. Layered structure of Ni-Al multi-layered metal-intermetallic composites fabricated by in-situ reactions

    Institute of Scientific and Technical Information of China (English)

    张佼; 孙宝德; 夏振海

    2004-01-01

    Systematical experiments were done at five temperature levels: 500 ℃, 630 ℃, 900 ℃, 1 000 ℃ and 1 100 ℃ to illuminate the layer structure of the multi-layered metal-intermetallic composites of Ni-Al system that were fabricated by a previously reported simple and cost-effective method. The analysis of back scattering photos and XRD examination of specimens reveal that the look like single compound layer is composed of several different components. The primary phase produced during reaction is Ni2 Al3 and there exists a like two-phase field between NiAl3 and Ni2 Al3. The high temperature phases like NiAl and Ni3 Al are also found at low temperature. The results indicate that the key driving force of in-situ reaction is not temperature, but the atom concentration.

  9. Van der Waals metal-semiconductor junction: Weak Fermi level pinning enables effective tuning of Schottky barrier.

    Science.gov (United States)

    Liu, Yuanyue; Stradins, Paul; Wei, Su-Huai

    2016-04-01

    Two-dimensional (2D) semiconductors have shown great potential for electronic and optoelectronic applications. However, their development is limited by a large Schottky barrier (SB) at the metal-semiconductor junction (MSJ), which is difficult to tune by using conventional metals because of the effect of strong Fermi level pinning (FLP). We show that this problem can be overcome by using 2D metals, which are bounded with 2D semiconductors through van der Waals (vdW) interactions. This success relies on a weak FLP at the vdW MSJ, which is attributed to the suppression of metal-induced gap states. Consequently, the SB becomes tunable and can vanish with proper 2D metals (for example, H-NbS2). This work not only offers new insights into the fundamental properties of heterojunctions but also uncovers the great potential of 2D metals for device applications.

  10. Effects of the strain relaxation of an AlGaN barrier layer induced by various cap layers on the transport properties in AlGaN/GaN heterostructures

    Institute of Scientific and Technical Information of China (English)

    Liu Zi-Yang; Zhang Jin-Cheng; Duan Huan-Tao; Xue Jun-Shuai; Lin Zhi-Yu; Ma Jun-Cai; Xue Xiao-Yong; Hao Yue

    2011-01-01

    The strain relaxation of an AlGaN barrier layer may be influenced by a thin cap layer above,and affects the transport properties of AlGaN/GaN heterostructures. Compared with the slight strain relaxation found in AlGaN barrier layer without cap layer,it is found that a thin cap layer can induce considerable changes of strain state in the AIGaN barrier layer. The degree of relaxation of the AlGaN layer significantly influences the transport properties of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures. It is observed that electron mobility decreases with the increasing degree of relaxation of the AlGaN barrier,which is believed to be the main cause of the deterioration of crystalline quality and morphology on the AlGaN/GaN interface. On the other hand,both GaN and AIN cap layers lead to a decrease in 2DEG density. The reduction of 2DEG caused by the GaN cap layer may be attributed to the additional negative polarization charges formed at the interface between GaN and AIGaN,while the reduction of the piezoelectric effect in the AlGaN layer results in the decrease of 2DEG density in the case of AIN cap layer.

  11. UN{sub 2−x} layer formed on uranium metal by glow plasma nitriding

    Energy Technology Data Exchange (ETDEWEB)

    Long, Zhong [China Academy of Engineering Physics, P.O. Box 919-71, Mianyang 621907 (China); Hu, Yin [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Chen, Lin [China Academy of Engineering Physics, P.O. Box 919-71, Mianyang 621907 (China); Luo, Lizhu [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Liu, Kezhao, E-mail: liukz@hotmail.com [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Lai, Xinchun, E-mail: lai319@yahoo.com [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China)

    2015-01-25

    Highlights: • We used a very simple method to prepare nitride layer on uranium metal surface. • This modified layer is nitrogen-rich nitride, which should be written as UN{sub 2−x}. • TEM images show the nitride layer is composed of nano-sized grains. • XPS analysis indicates there is uranium with abnormal low valence in the nitride. - Abstract: Glow plasma nitriding is a simple and economical surface treatment method, and this technology was used to prepare nitride layer on the surface of uranium metal with thickness of several microns. The composition and structure of the nitride layer were analyzed by AES and XRD, indicating that this modified layer is nitrogen-rich uranium nitride, which should be written as UN{sub 2−x}. TEM images show the nitride layer is composed of nano-sized grains, with compact structure. And XPS analysis indicates there is uranium with abnormal low valence existing in the nitride. After the treated uranium storage in air for a long time, oxygen just entered the surface several nanometers, showing the nitride layer has excellent oxidation resistance. The mechanism of nitride layer formation and low valence uranium appearance is discussed.

  12. Modelling water vapour permeability through atomic layer deposition coated photovoltaic barrier defects

    Energy Technology Data Exchange (ETDEWEB)

    Elrawemi, Mohamed, E-mail: Mohamed.elrawemi@hud.ac.uk [EPSRC Centre for Innovative Manufacturing in Advanced Metrology, School of Computing and Engineering, University of Huddersfield, Huddersfield (United Kingdom); Blunt, Liam; Fleming, Leigh [EPSRC Centre for Innovative Manufacturing in Advanced Metrology, School of Computing and Engineering, University of Huddersfield, Huddersfield (United Kingdom); Bird, David, E-mail: David.Bird@uk-cpi.com [Centre for Process Innovation Limited, Sedgefield, County Durham (United Kingdom); Robbins, David [Centre for Process Innovation Limited, Sedgefield, County Durham (United Kingdom); Sweeney, Francis [EPSRC Centre for Innovative Manufacturing in Advanced Metrology, School of Computing and Engineering, University of Huddersfield, Huddersfield (United Kingdom)

    2014-11-03

    Transparent barrier films such as Al{sub 2}O{sub 3} used for prevention of oxygen and/or water vapour permeation are the subject of increasing research interest when used for the encapsulation of flexible photovoltaic modules. However, the existence of micro-scale defects in the barrier surface topography has been shown to have the potential to facilitate water vapour ingress, thereby reducing cell efficiency and causing internal electrical shorts. Previous work has shown that small defects (≤ 3 μm lateral dimension) were less significant in determining water vapour ingress. In contrast, larger defects (≥ 3 μm lateral dimension) seem to be more detrimental to the barrier functionality. Experimental results based on surface topography segmentation analysis and a model presented in this paper will be used to test the hypothesis that the major contributing defects to water vapour transmission rate are small numbers of large defects. The model highlighted in this study has the potential to be used for gaining a better understanding of photovoltaic module efficiency and performance. - Highlights: • A model of water vapour permeation through barrier defects is presented. • The effect of the defects on the water vapour permeability is investigated. • Defect density correlates with water vapour permeability. • Large defects may dominate the permeation properties of the barrier film.

  13. Annealing dependence of diamond-metal Schottky barrier heights probed by hard x-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gaowei, M.; Muller, E. M. [Department of Materials Science and Engineering, SUNY Stony Brook, Stony Brook, New York 11794 (United States); Rumaiz, A. K. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973 (United States); Weiland, C.; Cockayne, E.; Woicik, J. C. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Jordan-Sweet, J. [IBM T.J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Smedley, J. [Instrumentation Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

    2012-05-14

    Hard x-ray photoelectron spectroscopy was applied to investigate the diamond-metal Schottky barrier heights for several metals and diamond surface terminations. The position of the diamond valence-band maximum was determined by theoretically calculating the diamond density of states and applying cross section corrections. The diamond-platinum Schottky barrier height was lowered by 0.2 eV after thermal annealing, indicating annealing may increase carrier injection in diamond devices leading to photoconductive gain. The platinum contacts on oxygen-terminated diamond was found to provide a higher Schottky barrier and therefore a better blocking contact than that of the silver contact in diamond-based electronic devices.

  14. A strategy to create spin-split metallic bands on silicon using a dense alloy layer.

    Science.gov (United States)

    Gruznev, Dimitry V; Bondarenko, Leonid V; Matetskiy, Andrey V; Yakovlev, Alexey A; Tupchaya, Alexandra Y; Eremeev, Sergey V; Chulkov, Evgeniy V; Chou, Jyh-Pin; Wei, Ching-Ming; Lai, Ming-Yu; Wang, Yuh-Lin; Zotov, Andrey V; Saranin, Alexander A

    2014-04-22

    To exploit Rashba effect in a 2D electron gas on silicon surface for spin transport, it is necessary to have surface reconstruction with spin-split metallic surface-state bands. However, metals with strong spin-orbit coupling (e.g., Bi, Tl, Sb, Pt) induce reconstructions on silicon with almost exclusively spin-split insulating bands. We propose a strategy to create spin-split metallic bands using a dense 2D alloy layer containing a metal with strong spin-orbit coupling and another metal to modify the surface reconstruction. Here we report two examples, i.e., alloying reconstruction with Na and Tl/Si(111)1 × 1 reconstruction with Pb. The strategy provides a new paradigm for creating metallic surface state bands with various spin textures on silicon and therefore enhances the possibility to integrate fascinating and promising capabilities of spintronics with current semiconductor technology.

  15. Intermediate type excitons in Schottky barriers of A{sup 3}B{sup 6} layer semiconductors and UV photodetectors

    Energy Technology Data Exchange (ETDEWEB)

    Alekperov, O.Z.; Guseinov, N.M.; Nadjafov, A.I. [Insitute of Physics of National Academy of Sinces of Azerbaijan, H. Javid av. 33, 1133 Baku (Azerbaijan)

    2006-09-15

    Photoelectric and photovoltaic spectra of Schottky barrier (SB) structures of InSe, GaSe and GaS layered semiconductors (LS) are investigated at quantum energies from the band edge excitons of corresponding materials up to 6.5eV. Spectral dependences of photoconductivity (PC) of photo resistors and barrier structures are strongly different at the quantum energies corresponding to the intermediate type excitons (ITE) observed in these semiconductors. It was suggested that high UV photoconductivity of A{sup 3}B{sup 6} LS is due to existence of high mobility light carriers in the depth of the band structure. It is shown that SB of semitransparent Au-InSe is high sensitive photo detector in UV region of spectra. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Growth and electronic structure of single-layered transition metal dichalcogenides

    DEFF Research Database (Denmark)

    Dendzik, Maciej

    2016-01-01

    The discovery of graphene has opened a novel research direction focused on the properties of 2D materials. Transition metal dichalcogenides (TMDCs) were quickly identified as important materials due to the great variety of electronic properties that they manifest – properties that are markedly...... different from graphene’s. For example, semiconducting TMDCs undergo an indirectdirect band gap transition when thinned to a single layer (SL); this results in greatly enhanced photoluminescence, making those materials attractive for applications in optoelectronics. Furthermore, metallic TMDCs can host...... TMDCs is directly studied with angle-resolved photoemission spectroscopy (ARPES) and x-ray photoelectron spectroscopy (XPS) techniques. Experimental results are compared with density-functional theory calculations (DFT), both for a free-standing layer and for a layer adsorbed on a metallic substrate...

  17. A proposed OEIC circuit with two metal layer silicon waveguide and low power photonic receiver circuit

    Directory of Open Access Journals (Sweden)

    Shiraz Afazal

    2012-09-01

    Full Text Available Recent development in the field of optical communication have increased the need for Opto Electronic Integrated circuit used for the high speed data transmission with low power consuming, high bandwidth and compact size. Presented is the OEIC chip with two metal layer waveguide and low power receiver circuit using standard CMOS technology. The silicon dioxide waveguide is composed of two metal layer reducing metal layer make OEIC cost effective , The silicon LED is fabricated using nwell/p-substrate with p+ octagonal rings, the p+/nwell forms the series pn junction to increase the light emitting area which operates in reverse bias mode. Photo detector is made of multiple PN junction to increase the depletion region width with n+ active implantation/n-well fabricated on the p substrate .the photocurrent receiver circuit is made of MOSFET to perform the function of photo detection and preamplification

  18. Silica-sol-based spin-coating barrier layer against phosphorous diffusion for crystalline silicon solar cells.

    Science.gov (United States)

    Uzum, Abdullah; Fukatsu, Ken; Kanda, Hiroyuki; Kimura, Yutaka; Tanimoto, Kenji; Yoshinaga, Seiya; Jiang, Yunjian; Ishikawa, Yasuaki; Uraoka, Yukiharu; Ito, Seigo

    2014-01-01

    The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n(+) emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion.

  19. Effect of Layer-Graded Bond Coats on Edge Stress Concentration and Oxidation Behavior of Thermal Barrier Coatings

    Science.gov (United States)

    Zhu, Dongming; Ghosn, Louis J.; Miller, Robert A.

    1998-01-01

    Thermal barrier coating (TBC) durability is closely related to design, processing and microstructure of the coating Z, tn systems. Two important issues that must be considered during the design of a thermal barrier coating are thermal expansion and modulus mismatch between the substrate and the ceramic layer, and substrate oxidation. In many cases, both of these issues may be best addressed through the selection of an appropriate bond coat system. In this study, a low thermal expansion and layer-graded bond coat system, that consists of plasma-sprayed FeCoNiCrAl and FeCrAlY coatings, and a high velocity oxyfuel (HVOF) sprayed FeCrAlY coating, is developed to minimize the thermal stresses and provide oxidation resistance. The thermal expansion and oxidation behavior of the coating system are also characterized, and the strain isolation effect of the bond coat system is analyzed using the finite element method (FEM). Experiments and finite element results show that the layer-graded bond coat system possesses lower interfacial stresses. better strain isolation and excellent oxidation resistance. thus significantly improving the coating performance and durability.

  20. Metal clusters on supported argon layers; Metallcluster auf dielektrischen Substraten

    Energy Technology Data Exchange (ETDEWEB)

    Faber, Bernhard

    2011-10-21

    The deposition of small sodium clusters on supported Ar(001)-surfaces is simulated. Theoretical description is achieved by a hierarchical model consisting of time-dependent DFT and molecular dynamics. The valence electrons of the sodium atoms are considered by Kohn-Sham-Scheme with self interaction correction. The interaction of argon atoms and sodium ions is described by atom-atom potentials whereas the coupling to the QM electrons is done by local pseudo-potentials. A decisive part of the model is the dynamical polarizability of the rare-gas atoms. The optional metal support is considered by the method of image charges. The influence of the forces caused by image charges and the influence of the number of argon monolayers on structure, optical response and deposition dynamics of Na{sub 6} and Na{sub 8} is investigated. There is very little influence on cluster structure and only a small shift of the cluster perpendicular to the surface. Concerning optical response the position of the Mie plasmon peak stays robust whereas the details of spectral fragmentation react very sensitively to changes. The forces caused by image charges of the metal support play only a little role with the dynamics of deposition while the thickness of the argon surface strongly influences the dissipation. (orig.)

  1. Fabrication of stable electrode/diffusion barrier layers for thermoelectric filled skutterudite devices

    Energy Technology Data Exchange (ETDEWEB)

    Jie, Qing; Ren, Zhifeng; Chen, Gang

    2015-12-08

    Disclosed are methods for the manufacture of n-type and p-type filled skutterudite thermoelectric legs of an electrical contact. A first material of CoSi.sub.2 and a dopant are ball-milled to form a first powder which is thermo-mechanically processed with a second powder of n-type skutterudite to form a n-type skutterudite layer disposed between a first layer and a third layer of the doped-CoSi.sub.2. In addition, a plurality of components such as iron, and nickel, and at least one of cobalt or chromium are ball-milled form a first powder that is thermo-mechanically processed with a p-type skutterudite layer to form a p-type skutterudite layer "second layer" disposed between a first and a third layer of the first powder. The specific contact resistance between the first layer and the skutterudite layer for both the n-type and the p-type skutterudites subsequent to hot-pressing is less than about 10.0 .mu..OMEGA.cm.sup.2.

  2. Fabrication of stable electrode/diffusion barrier layers for thermoelectric filled skutterudite devices

    Energy Technology Data Exchange (ETDEWEB)

    Jie, Qing; Ren, Zhifeng; Chen, Gang

    2017-08-01

    Disclosed are methods for the manufacture of n-type and p-type filled skutterudite thermoelectric legs of an electrical contact. A first material of CoSi.sub.2 and a dopant are ball-milled to form a first powder which is thermo-mechanically processed with a second powder of n-type skutterudite to form a n-type skutterudite layer disposed between a first layer and a third layer of the doped-CoSi.sub.2. In addition, a plurality of components such as iron, and nickel, and at least one of cobalt or chromium are ball-milled form a first powder that is thermo-mechanically processed with a p-type skutterudite layer to form a p-type skutterudite layer "second layer" disposed between a first and a third layer of the first powder. The specific contact resistance between the first layer and the skutterudite layer for both the n-type and the p-type skutterudites subsequent to hot-pressing is less than about 10.0 .mu..OMEGA.cm.sup.2.

  3. Interfacial effect on the electrochemical properties of the layered graphene/metal sulfide composites as anode materials for Li-ion batteries

    Science.gov (United States)

    Lv, Yagang; Chen, Biao; Zhao, Naiqin; Shi, Chunsheng; He, Chunnian; Li, Jiajun; Liu, Enzuo

    2016-09-01

    The layered graphene/metal sulfide composites exhibit excellent electrochemical properties as anode materials for lithium ion battery, due to the synergistic effect between metal sulfide and graphene which still needs to be further understood. In this study, Li adsorption and diffusion on MoS2 and SnS2 monolayers and Li2S surface, as well as at their interfaces with graphene, are systematically investigated through first-principles calculations. The analysis of charge density difference, Bader charge, and density of states indicates that the adsorbed Li atoms interact with both the S atoms at metal sulfide surfaces and C atoms in graphene, resulting in larger Li adsorption energies at the interfaces compared with that on the corresponding surfaces, but with almost no enhancement of the energy barriers for Li atom diffusion. The enhanced Li adsorption capability at Li2S/G interface contributes to the extra storage capacity of graphene/metal sulfide composites. Furthermore, the synergistic mechanism between metal sulfide and graphene is revealed. Moreover, band structure analysis shows the electronic conductivity is enhanced with the incorporation of graphene. The results corroborate the interfacial pseudocapacity-like Li atom storage mechanism, and are helpful for the design of layered graphene/metal sulfide composites as anode materials for lithium ion batteries.

  4. Barrier properties of plastic films coated with an Al{sub 2}O{sub 3} layer by roll-to-toll atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Hirvikorpi, Terhi, E-mail: Terhi.Hirvikorpi@picosun.com [Picosun Oy, Tietotie 3, FI-02150 Espoo (Finland); Laine, Risto, E-mail: Risto.Laine@picosun.com [Picosun Oy, Tietotie 3, FI-02150 Espoo (Finland); Vähä-Nissi, Mika, E-mail: Mika.Vaha-Nissi@vtt.fi [VTT Technical Research Centre of Finland, Biologinkuja 7, Espoo, P.O. Box 1000, FI-02044 VTT (Finland); Kilpi, Väinö, E-mail: Vaino.Kilpi@picosun.com [Picosun Oy, Tietotie 3, FI-02150 Espoo (Finland); Salo, Erkki, E-mail: Erkki.Salo@vtt.fi [VTT Technical Research Centre of Finland, Biologinkuja 7, Espoo, P.O. Box 1000, FI-02044 VTT (Finland); Li, Wei-Min, E-mail: Wei-Min.Li@picosun.com [Picosun Oy, Tietotie 3, FI-02150 Espoo (Finland); Lindfors, Sven, E-mail: Sven.Lindfors@picosun.com [Picosun Oy, Tietotie 3, FI-02150 Espoo (Finland); Vartiainen, Jari, E-mail: Jari.Vartiainen@vtt.fi [VTT Technical Research Centre of Finland, Biologinkuja 7, Espoo, P.O. Box 1000, FI-02044 VTT (Finland); Kenttä, Eija, E-mail: Eija.Kentta@vtt.fi [VTT Technical Research Centre of Finland, Biologinkuja 7, Espoo, P.O. Box 1000, FI-02044 VTT (Finland); Nikkola, Juha, E-mail: Juha.Nikkola@vtt.fi [VTT Technical Research Centre of Finland, P.O. Box 1300, FI-33101 Tampere (Finland); Harlin, Ali, E-mail: Ali.Harlin@vtt.fi [VTT Technical Research Centre of Finland, Biologinkuja 7, Espoo, P.O. Box 1000, FI-02044 VTT (Finland); Kostamo, Juhana, E-mail: Juhana.Kostamo@picosun.com [Picosun Oy, Tietotie 3, FI-02150 Espoo (Finland)

    2014-01-01

    Thin (30–40 nm) and highly uniform Al{sub 2}O{sub 3} coatings have been deposited at relatively low temperature of 100 °C onto various polymeric materials employing the atomic layer deposition (ALD) technique, both batch and roll-to-roll (R2R) mode. The applications for ALD have long been limited those feasible for batch processing. The work demonstrates that R2R ALD can deposit thin films with properties that are comparable to the film properties fabricated by in batch. This accelerates considerably the commercialization of many products, such as flexible, printed electronics, organic light-emitting diode lighting, third generation thin film photovoltaic devices, high energy density thin film batteries, smart textiles, organic sensors, organic/recyclable packaging materials, and flexible displays, to name a few. - Highlights: • Thin and uniform Al{sub 2}O{sub 3} coatings have been deposited onto polymers materials. • Batch and roll-to-roll (R2R) atomic layer deposition (ALD) have been employed. • Deposition with either process improved the barrier properties. • Sensitivity of coated films to defects affects barrier obtained with R2R ALD.

  5. Magnetic field induced coherence-incoherence crossover in the interlayer conductivity of a layered organic metal

    Science.gov (United States)

    Kartsovnik, M. V.; Grigoriev, P. D.; Biberacher, W.; Kushch, N. D.

    2009-04-01

    The angle-dependent interlayer magnetoresistance of the pressurized (to the normal metallic state) layered organic metal α-(BEDT-TTF)2KHg(SCN)4 is found to change from the conventional behavior at low magnetic fields to an anomalous one at high fields. The dependence of this field-induced crossover on the sample purity and temperature reveals parallel contribution of the classical Boltzmann and incoherent channels in the interlayer conductivity. The latter channel, having a metallic temperature dependence but being insensitive to an in-plane magnetic field, may be responsible for magnetoresistance anomalies observed in a number of layered metals. We propose a possible mechanism for the incoherent channel combining interlayer tunneling via local hopping centers and intralayer diffusion.

  6. Synthesis of multicomponent metallic layers during impulse plasma deposition

    Directory of Open Access Journals (Sweden)

    Nowakowska-Langier Katarzyna

    2015-12-01

    Full Text Available Pulsed plasma in the impulse plasma deposition (IPD synthesis is generated in a coaxial accelerator by strong periodic electrical pulses, and it is distributed in a form of energetic plasma packets. A nearly complete ionization of gas, in these conditions of plasma generation, favors the nucleation of new phase of ions and synthesis of metastable materials in a form of coatings which are characterized by amorphous and/or nanocrystalline structure. In this work, the Fe–Cu alloy, which is immiscible in the state of equilibrium, was selected as a model system to study the possibility of formation of a non-equilibrium phase during the IPD synthesis. Structural characterization of the layers was done by means of X-ray diffraction and conversion-electron Mössbauer spectroscopy. It was found that supersaturated solid solutions were created as a result of mixing and/or alloying effects between the layer components delivered to the substrate independently and separately in time. Therefore, the solubility in the Fe–Cu system was largely extended in relation to the equilibrium conditions, as described by the equilibrium phase diagram in the solid state.

  7. Graphene oxide monolayers as atomically thin seeding layers for atomic layer deposition of metal oxides

    Science.gov (United States)

    Nourbakhsh, Amirhasan; Adelmann, Christoph; Song, Yi; Lee, Chang Seung; Asselberghs, Inge; Huyghebaert, Cedric; Brizzi, Simone; Tallarida, Massimo; Schmeißer, Dieter; van Elshocht, Sven; Heyns, Marc; Kong, Jing; Palacios, Tomás; de Gendt, Stefan

    2015-06-01

    Graphene oxide (GO) was explored as an atomically-thin transferable seed layer for the atomic layer deposition (ALD) of dielectric materials on any substrate of choice. This approach does not require specific chemical groups on the target surface to initiate ALD. This establishes GO as a unique interface which enables the growth of dielectric materials on a wide range of substrate materials and opens up numerous prospects for applications. In this work, a mild oxygen plasma treatment was used to oxidize graphene monolayers with well-controlled and tunable density of epoxide functional groups. This was confirmed by synchrotron-radiation photoelectron spectroscopy. In addition, density functional theory calculations were carried out on representative epoxidized graphene monolayer models to correlate the capacitive properties of GO with its electronic structure. Capacitance-voltage measurements showed that the capacitive behavior of Al2O3/GO depends on the oxidation level of GO. Finally, GO was successfully used as an ALD seed layer for the deposition of Al2O3 on chemically inert single layer graphene, resulting in high performance top-gated field-effect transistors.Graphene oxide (GO) was explored as an atomically-thin transferable seed layer for the atomic layer deposition (ALD) of dielectric materials on any substrate of choice. This approach does not require specific chemical groups on the target surface to initiate ALD. This establishes GO as a unique interface which enables the growth of dielectric materials on a wide range of substrate materials and opens up numerous prospects for applications. In this work, a mild oxygen plasma treatment was used to oxidize graphene monolayers with well-controlled and tunable density of epoxide functional groups. This was confirmed by synchrotron-radiation photoelectron spectroscopy. In addition, density functional theory calculations were carried out on representative epoxidized graphene monolayer models to correlate the

  8. Stress Analysis of a Three-Layer Metal Composite System of Bearing Assemblies During Grinding

    Science.gov (United States)

    Pashnyov, V. A.; Pimenov, D. Yu.

    2015-03-01

    A mathematical model of the stress state of a three-layer metal composite system caused by cutting forces during grinding the working layer of the system is elaborated. The implementation of the model by using the finite-element method made it possible to assess the effect of structure of the system, the deformation properties of layer materials, and grinding conditions on the distribution and level of normal and tangential stresses in layers, which determine the load-carrying capacity of the system. The results of an analysis of stress fields can serve as a basis for determining the grinding conditions ensuring retention of the load-carrying capacity of the metal composite system.

  9. Melt layer behavior of metal targets irradiatead by powerful plasma streams

    Science.gov (United States)

    Bandura, A. N.; Byrka, O. V.; Chebotarev, V. V.; Garkusha, I. E.; Makhlaj, V. A.; Solyakov, D. G.; Tereshin, V. I.; Wuerz, H.

    2002-12-01

    In this paper melt layer erosion of metal targets under pulsed high-heat loads is studied. Experiments with steel, copper, aluminum and titanium samples were carried out in two plasma accelerator devices with different time durations of the heat load. The surfaces of the resolidified melt layers show a considerable roughness with microcraters and ridge like relief on the surface. For each material the mass loss was determined. Melt layer erosion by melt motion was clearly identified. However it is masked by boiling, bubble expansion and bubble collapse and by formation of a Kelvin-Helmholtz instability. The experimental results can be used for validation of numerical codes which model melt layer erosion of metallic armour materials in off-normal events, in tokamaks.

  10. Schottky barrier contrasts in single and bi-layer graphene contacts for MoS2 field-effect transistors

    Science.gov (United States)

    Du, Hyewon; Kim, Taekwang; Shin, Somyeong; Kim, Dahye; Kim, Hakseong; Sung, Ji Ho; Lee, Myoung Jae; Seo, David H.; Lee, Sang Wook; Jo, Moon-Ho; Seo, Sunae

    2015-12-01

    We have investigated single- and bi-layer graphene as source-drain electrodes for n-type MoS2 transistors. Ti-MoS2-graphene heterojunction transistors using both single-layer MoS2 (1M) and 4-layer MoS2 (4M) were fabricated in order to compare graphene electrodes with commonly used Ti electrodes. MoS2-graphene Schottky barrier provided electron injection efficiency up to 130 times higher in the subthreshold regime when compared with MoS2-Ti, which resulted in VDS polarity dependence of device parameters such as threshold voltage (VTH) and subthreshold swing (SS). Comparing single-layer graphene (SG) with bi-layer graphene (BG) in 4M devices, SG electrodes exhibited enhanced device performance with higher on/off ratio and increased field-effect mobility (μFE) due to more sensitive Fermi level shift by gate voltage. Meanwhile, in the strongly accumulated regime, we observed opposing behavior depending on MoS2 thickness for both SG and BG contacts. Differential conductance (σd) of 1M increases with VDS irrespective of VDS polarity, while σd of 4M ceases monotonic growth at positive VDS values transitioning to ohmic-like contact formation. Nevertheless, the low absolute value of σd saturation of the 4M-graphene junction demonstrates that graphene electrode could be unfavorable for high current carrying transistors.

  11. Influence of a thin metal layer on a beam propagation in a biconical optical fibre taper

    Science.gov (United States)

    Stasiewicz, K. A.; Moś, J. E.

    2016-12-01

    The paper presents results of a simulation of the plasmon effect achieved between a thin precious metal layer and a biconical optical fibre taper, manufactured on a standard single mode fibre. Gold, silver and titanium were used as a metal which fulfilled a cladding function for a small diameter structure. For simulation Mode Solution software was used on which modal and frequency analyses of a wavelength were provided in the range of 800-1700 nm. A displacement of a plasmon pick in dependence of thickness of a deposited precious layer for the highest plasmon effects was observed.

  12. Adhesion of oxide layer to metal-doped aluminum hydride surface: Density functional calculations

    Science.gov (United States)

    Takezawa, Tomoki; Itoi, Junichi; Kannan, Takashi

    2017-07-01

    The density functional theory (DFT) calculations were carried out to evaluate the adhesion energy of the oxide layer to the metal-doped surface of hydrogen storage material, aluminum hydride (alane, AlH3). The total energy calculations using slab model revealed that the surface doping of some metals to aluminum hydride weakens the adhesion strength of the oxide layer. The influence of titanium, iron, cobalt, and zirconium doping on adhesion strength were evaluated. Except for iron doping, the adhesion strength becomes weak by the doping.

  13. Experimental evidence of total absorption by a thin absorbing layer deposited on a patterned metallic surface

    CERN Document Server

    Díaz-Rubio, Ana; Carbonell, Jorge; Sánchez-Dehesa, José

    2014-01-01

    This work presents the experimental demonstration of total absorption by a metal-dielectric metasurface. Following the theoretical proposal [A. D\\'iaz-Rubio et al. Phys. Rev. B 89, 245123 (2014)], we fabricated a metasurface consisting of a low absorbing dielectric layer (made of FR4) deposited on top of a metallic surface patterned with a square distribution of coaxial cavities. For P-polarized waves, it is observed a low frequency peak with perfect absorption. The behavior of this peak has been experimentally characterized for different dielectric layer thicknesses, coaxial cavity lengths and incidence angles. The experimental results are in excellent agreement with numerical simulation and support the previous theoretical findings.

  14. FTIR spectroscopy structural analysis of the interaction between Lactobacillus kefir S-layers and metal ions

    Science.gov (United States)

    Gerbino, E.; Mobili, P.; Tymczyszyn, E.; Fausto, R.; Gómez-Zavaglia, A.

    2011-02-01

    FTIR spectroscopy was used to structurally characterize the interaction of S-layer proteins extracted from two strains of Lactobacillus kefir (the aggregating CIDCA 8348 and the non-aggregating JCM 5818) with metal ions (Cd +2, Zn +2, Pb +2 and Ni +2). The infrared spectra indicate that the metal/protein interaction occurs mainly through the carboxylate groups of the side chains of Asp and Glut residues, with some contribution of the NH groups belonging to the peptide backbone. The frequency separation between the νCOO - anti-symmetric and symmetric stretching vibrations in the spectra of the S-layers in presence of the metal ions was found to be ca. 190 cm -1 for S-layer CIDCA 8348 and ca. 170 cm -1 for JCM 5818, denoting an unidentate coordination in both cases. Changes in the secondary structures of the S-layers induced by the interaction with the metal ions were also noticed: a general trend to increase the amount of β-sheet structures and to reduce the amount of α-helices was observed. These changes allow the proteins to adjust their structure to the presence of the metal ions at minimum energy expense, and accordingly, these adjustments were found to be more important for the bigger ions.

  15. Next-Generation Lithium Metal Anode Engineering via Atomic Layer Deposition.

    Science.gov (United States)

    Kozen, Alexander C; Lin, Chuan-Fu; Pearse, Alexander J; Schroeder, Marshall A; Han, Xiaogang; Hu, Liangbing; Lee, Sang-Bok; Rubloff, Gary W; Noked, Malachi

    2015-06-23

    Lithium metal is considered to be the most promising anode for next-generation batteries due to its high energy density of 3840 mAh g(-1). However, the extreme reactivity of the Li surface can induce parasitic reactions with solvents, contamination, and shuttled active species in the electrolyte, reducing the performance of batteries employing Li metal anodes. One promising solution to this issue is application of thin chemical protection layers to the Li metal surface. Using a custom-made ultrahigh vacuum integrated deposition and characterization system, we demonstrate atomic layer deposition (ALD) of protection layers directly on Li metal with exquisite thickness control. We demonstrate as a proof-of-concept that a 14 nm thick ALD Al2O3 layer can protect the Li surface from corrosion due to atmosphere, sulfur, and electrolyte exposure. Using Li-S battery cells as a test system, we demonstrate an improved capacity retention using ALD-protected anodes over cells assembled with bare Li metal anodes for up to 100 cycles.

  16. Optical Effects in the Active Layer of Organic Solar Cells with Embedded Noble Metal Nanoparticles

    OpenAIRE

    Supachai Sompech; Sukhontip Thaomola; Thananchai Dasri

    2016-01-01

    The optical properties of organic solar cells with noble metal nanoparticles such as Ag and Au embedded in the active layer were investigated. The Discrete Dipole Approximation theory was used to analyze the light scattering and absorption efficiencies. The results show that the size, refractive index of medium and amount of the metal nanoparticles are key factors that directly influence the plasmonic enhancements in the devices. These parameters were adjusted for the light scattering and abs...

  17. Optical limiting of layered transition metal dichalcogenide semiconductors

    CERN Document Server

    Dong, Ningning; Feng, Yanyan; Zhang, Saifeng; Zhang, Xiaoyan; Chang, Chunxia; Fan, Jintai; Zhang, Long; Wang, Jun

    2015-01-01

    Nonlinear optical property of transition metal dichalcogenide (TMDC) nanosheet dispersions, including MoS2, MoSe2, WS2, and WSe2, was performed by using Z-scan technique with ns pulsed laser at 1064 nm and 532 nm. The results demonstrate that the TMDC dispersions exhibit significant optical limiting response at 1064 nm due to nonlinear scattering, in contrast to the combined effect of both saturable absorption and nonlinear scattering at 532 nm. Selenium compounds show better optical limiting performance than that of the sulfides in the near infrared. A liquid dispersion system based theoretical modelling is proposed to estimate the number density of the nanosheet dispersions, the relationship between incident laser fluence and the size of the laser generated micro-bubbles, and hence the Mie scattering-induced broadband optical limiting behavior in the TMDC dispersions.

  18. Schottky barrier detection devices having a 4H-SiC n-type epitaxial layer

    Science.gov (United States)

    Mandal, Krishna C.; Terry, J. Russell

    2016-12-06

    A detection device, along with methods of its manufacture and use, is provided. The detection device can include: a SiC substrate defining a substrate surface cut from planar to about 12.degree.; a buffer epitaxial layer on the substrate surface; a n-type epitaxial layer on the buffer epitaxial layer; and a top contact on the n-type epitaxial layer. The buffer epitaxial layer can include a n-type 4H--SiC epitaxial layer doped at a concentration of about 1.times.10.sup.15 cm.sup.-3 to about 5.times.10.sup.18 cm.sup.-3 with nitrogen, boron, aluminum, or a mixture thereof. The n-type epitaxial layer can include a n-type 4H--SiC epitaxial layer doped at a concentration of about 1.times.10.sup.13 cm.sup.-3 to about 5.times.10.sup.15 cm.sup.-3 with nitrogen. The top contact can have a thickness of about 8 nm to about 15 nm.

  19. Graphene oxide monolayers as atomically thin seeding layers for atomic layer deposition of metal oxides.

    Science.gov (United States)

    Nourbakhsh, Amirhasan; Adelmann, Christoph; Song, Yi; Lee, Chang Seung; Asselberghs, Inge; Huyghebaert, Cedric; Brizzi, Simone; Tallarida, Massimo; Schmeisser, Dieter; Van Elshocht, Sven; Heyns, Marc; Kong, Jing; Palacios, Tomás; De Gendt, Stefan

    2015-06-28

    Graphene oxide (GO) was explored as an atomically-thin transferable seed layer for the atomic layer deposition (ALD) of dielectric materials on any substrate of choice. This approach does not require specific chemical groups on the target surface to initiate ALD. This establishes GO as a unique interface which enables the growth of dielectric materials on a wide range of substrate materials and opens up numerous prospects for applications. In this work, a mild oxygen plasma treatment was used to oxidize graphene monolayers with well-controlled and tunable density of epoxide functional groups. This was confirmed by synchrotron-radiation photoelectron spectroscopy. In addition, density functional theory calculations were carried out on representative epoxidized graphene monolayer models to correlate the capacitive properties of GO with its electronic structure. Capacitance-voltage measurements showed that the capacitive behavior of Al2O3/GO depends on the oxidation level of GO. Finally, GO was successfully used as an ALD seed layer for the deposition of Al2O3 on chemically inert single layer graphene, resulting in high performance top-gated field-effect transistors.

  20. Polymer Layers by Initiated CVD for Thin Film Gas Barrier Encapsulation

    NARCIS (Netherlands)

    Spee, D.A.; Rath, J.K.; Schropp, R.E.I.

    2013-01-01

    In this chapter a thorough description of the initiated chemical vapor deposition (iCVD) process will be given, concentrating on molecular weight and deposition rate of the deposited polymer, which are essential for largescale application in hybrid gas barriers. Practical applications of coatings by

  1. Angular and positional dependence of Purcell effect for layered metal-dielectric structures

    Science.gov (United States)

    Gubaydullin, A. R.; Mazlin, V. A.; Ivanov, K. A.; Kaliteevski, M. A.; Balocco, C.

    2016-04-01

    We study the angular dependence of the spontaneous emission enhancement of a dipole source inserted into a layered metal-dielectric metamaterial. We analyse the dependence of Purcell effect from the position of the dipole in the layered hyperbolic media. We analyse the impact of the complex structure of eigenmodes of the system operating in hyperbolic regime. We have shown that the spontaneous emission rate of the dipole emitter depends on its position, which mainly affect the interaction with Langmuir modes.

  2. Monolayer graphene/SiC Schottky barrier diodes with improved barrier height uniformity as a sensing platform for the detection of heavy metals.

    Science.gov (United States)

    Shtepliuk, Ivan; Eriksson, Jens; Khranovskyy, Volodymyr; Iakimov, Tihomir; Lloyd Spetz, Anita; Yakimova, Rositsa

    2016-01-01

    A vertical diode structure comprising homogeneous monolayer epitaxial graphene on silicon carbide is fabricated by thermal decomposition of a Si-face 4H-SiC wafer in argon atmosphere. Current-voltage characteristics of the graphene/SiC Schottky junction were analyzed by applying the thermionic-emission theory. Extracted values of the Schottky barrier height and the ideality factor are found to be 0.4879 ± 0.013 eV and 1.01803 ± 0.0049, respectively. Deviations of these parameters from average values are smaller than those of previously observed literature data, thereby implying uniformity of the Schottky barrier height over the whole diode area, a stable rectifying behaviour and a good quality of ohmic palladium-graphene contacts. Keeping in mind the strong sensitivity of graphene to analytes we propose the possibility to use the graphene/SiC Schottky diode as a sensing platform for the recognition of toxic heavy metals. Using density functional theory (DFT) calculations we gain insight into the nature of the interaction of cadmium, mercury and lead with graphene as well as estimate the work function and the Schottky barrier height of the graphene/SiC structure before and after applying heavy metals to the sensing material. A shift of the I-V characteristics of the graphene/SiC-based sensor has been proposed as an indicator of presence of the heavy metals. Since the calculations suggested the strongest charge transfer between Pb and graphene, the proposed sensing platform was characterized by good selectivity towards lead atoms and slight interferences from cadmium and mercury. The dependence of the sensitivity parameters on the concentration of Cd, Hg and Pb is studied and discussed.

  3. Monolayer graphene/SiC Schottky barrier diodes with improved barrier height uniformity as a sensing platform for the detection of heavy metals

    Directory of Open Access Journals (Sweden)

    Ivan Shtepliuk

    2016-11-01

    Full Text Available A vertical diode structure comprising homogeneous monolayer epitaxial graphene on silicon carbide is fabricated by thermal decomposition of a Si-face 4H-SiC wafer in argon atmosphere. Current–voltage characteristics of the graphene/SiC Schottky junction were analyzed by applying the thermionic-emission theory. Extracted values of the Schottky barrier height and the ideality factor are found to be 0.4879 ± 0.013 eV and 1.01803 ± 0.0049, respectively. Deviations of these parameters from average values are smaller than those of previously observed literature data, thereby implying uniformity of the Schottky barrier height over the whole diode area, a stable rectifying behaviour and a good quality of ohmic palladium–graphene contacts. Keeping in mind the strong sensitivity of graphene to analytes we propose the possibility to use the graphene/SiC Schottky diode as a sensing platform for the recognition of toxic heavy metals. Using density functional theory (DFT calculations we gain insight into the nature of the interaction of cadmium, mercury and lead with graphene as well as estimate the work function and the Schottky barrier height of the graphene/SiC structure before and after applying heavy metals to the sensing material. A shift of the I–V characteristics of the graphene/SiC-based sensor has been proposed as an indicator of presence of the heavy metals. Since the calculations suggested the strongest charge transfer between Pb and graphene, the proposed sensing platform was characterized by good selectivity towards lead atoms and slight interferences from cadmium and mercury. The dependence of the sensitivity parameters on the concentration of Cd, Hg and Pb is studied and discussed.

  4. Noncovalent functionalization of few-layer black phosphorus with metal nanoparticles and its application in catalysis

    CERN Document Server

    Caporali, Maria; Telesio, Francesca; Heun, Stefan; Nicotra, Giuseppe; Spinella, Corrado; Caporali, Stefano; Peruzzini, Maurizio

    2016-01-01

    Transition metal nanoparticles of Ni, Pd, Ru and Au, each of them stabilized by a suitable capping agent, were dispersed on the surface of few-layer black phosphorus (2D BP) achieving new nanocomposite 2D materials. Ni nanoparticles supported on 2D BP worked successfully in the hydrogenation of phenylacetylene, showing good catalytic activity preserved after recycling tests. These results highlight that 2D BP is able to stabilize metal nanoparticles through weak noncovalent interactions and disclose a wide application of 2D BP as a hosting platform for catalytically active metal species.

  5. Control of electronic properties of 2D carbides (MXenes) by manipulating their transition metal layers

    KAUST Repository

    Anasori, Babak

    2016-02-24

    In this study, a transition from metallic to semiconducting-like behavior has been demonstrated in two-dimensional (2D) transition metal carbides by replacing titanium with molybdenum in the outer transition metal (M) layers of M3C2 and M4C3 MXenes. The MXene structure consists of n + 1 layers of near-close packed M layers with C or N occupying the octahedral site between them in an [MX]nM arrangement. Recently, two new families of ordered 2D double transition metal carbides MXenes were discovered, M′2M′′C2 and M′2M′′2C3 – where M′ and M′′ are two different early transition metals, such as Mo, Cr, Ta, Nb, V, and Ti. The M′ atoms only occupy the outer layers and the M′′ atoms fill the middle layers. In other words, M′ atomic layers sandwich the middle M′′–C layers. Using X-ray atomic pair distribution function (PDF) analysis on Mo2TiC2 and Mo2Ti2C3 MXenes, we present the first quantitative analysis of structures of these novel materials and experimentally confirm that Mo atoms are in the outer layers of the [MC]nM structures. The electronic properties of these Mo-containing MXenes are compared with their Ti3C2 counterparts, and are found to be no longer metallic-like conductors; instead the resistance increases mildly with decreasing temperatures. Density functional theory (DFT) calculations suggest that OH terminated Mo–Ti MXenes are semiconductors with narrow band gaps. Measurements of the temperature dependencies of conductivities and magnetoresistances have confirmed that Mo2TiC2Tx exhibits semiconductor-like transport behavior, while Ti3C2Tx is a metal. This finding opens new avenues for the control of the electronic and optical applications of MXenes and for exploring new applications, in which semiconducting properties are required.

  6. Yield estimation of metallic layers in integrated circuits

    Institute of Scientific and Technical Information of China (English)

    Wang Jun-Ping; Hao Yue; Zhang Jun-Ming

    2007-01-01

    In the existing models of estimating the yield and critical area, the defect outline is usually assumed to be circular, but the observed real defect outlines are irregular in shape. In this paper, estimation of the yield and critical area is made using the Monte Carlo technique and the relationship between the errors of yield estimated by circular defect and the rectangle degree of the defect is analysed. The rectangular model of a real defect is presented, and the yield model is provided correspondingly. The models take into account an outline similar to that of an original defect, the characteristics of two-dimensional distribution of defects, the feature of a layout routing, and the character of yield estimation. In order to make the models practicable, the critical area computations related to rectangular defect and regular (vertical or horizontal) routing are discussed. The critical areas associated with rectangular defect and non-regular routing are developed also, based on the mathematical morphology. The experimental results show that the new yield model may predict the yield caused by real defects more accurately than the circular model. It is significant that the yield is accurately estimated using the proposed model for 1C metals.

  7. Metal ion-specific thermal stability of bacterial S-Layers

    Energy Technology Data Exchange (ETDEWEB)

    Drobot, Bjoern; Raff, Johannes [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Div. Biogeochemistry; Fahmy, Karim [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Div. Biophysics

    2016-07-01

    Many bacteria are covered by a surface layer (S-layer), i.e., a para-crystalline two-dimensional array of proteins which control cell shape, act as molecular sieves and have potential applications as radionuclide-binding material for bioremediation of polluted areas. Knowledge and control of the metal-dependent stability of the purified proteins is required for their technical application. Here, we have explored by differential scanning calorimetry the thermal stability of the S-layer protein slp-B53 from Lysinibacillus sphaericus, a Gram-positive bacterium isolated from a uranium mining waste pile [1].

  8. Estimation of the barrier layer thickness in the Indian Ocean using Aquarius Salinity.

    Digital Repository Service at National Institute of Oceanography (India)

    Felton, C.S.; Subrahmanyam, B.; Murty, V.S.N; Shriver, J.F.

    , as well as the advantages and disadvantages of the current model are discussed. BLT estimations using HYCOM simulations display large errors that are related to model layer structure and the selected BLT methodology....

  9. Structural analysis of nitride layer formed on uranium metal by glow plasma surface nitriding

    Energy Technology Data Exchange (ETDEWEB)

    Liu Kezhao, E-mail: liukz@hotmail.com [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Bin Ren [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Xiao Hong [China Academy of Engineering Physics, P.O. Box 919-71, Mianyang 621907 (China); Long Zhong [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Hong Zhanglian, E-mail: hong_zhanglian@zju.edu.cn [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Yang Hui [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Wu Sheng [China Academy of Engineering Physics, P.O. Box 919-71, Mianyang 621907 (China)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer The nitride layer was formed on uranium by glow plasma surface nitriding. Black-Right-Pointing-Pointer Four zones were observed in the nitride layer. Black-Right-Pointing-Pointer The chemical states of uranium, nitrogen, and oxygen were identified by AES. - Abstract: The nitride layer was formed on uranium metal by a glow plasma surface nitriding method. The structure and composition of the layer were investigated by X-ray diffraction and Auger electron spectroscopy. The nitride layer mainly consisted of {alpha}-phase U{sub 2}N{sub 3} nanocrystals with an average grain size about 10-20 nm. Four zones were identified in the layer, which were the oxide surface zone, the nitride mainstay zone, the oxide-existence interface zone, and the nitrogen-diffusion matrix zone. The gradual decrease of binding energies of uranium revealed the transition from oxide to nitride to metal states with the layer depth, while the chemical states of nitrogen and oxygen showed small variation.

  10. Characteristics of Spontaneous Emission of Polarized Atoms in Metal-Dielectric Multiple Layer Structures

    Institute of Scientific and Technical Information of China (English)

    ZHAO Li-Ming; GU Ben-Yuan; ZHOU Yun-Song

    2007-01-01

    The spontaneous emission (SE) progress of polarized atoms in a stratified structure ofair-dielectric(D0)-metal(M)-dielectric(D1)-air can be controlled effectively by changing the thickness of the D1 layer and rotating the polarized direction of atoms. It is found that the normalized SE rate of atoms located inside the D0 layer crucially depends on the atomic position and the thickness of the D1 layer. When the atom is located near the D0-M interface, the normalized atomic SE rate as a function of the atomic position is abruptly onset for the thin D1 layer. However, with the increasing thickness of the D1 layer, the corresponding curve profile exhibits plateau and stays nearly unchanged. The substantial change of the SE rate stems from the excitation of the surface plasmon polaritons in metal-dielectric interface, and the feature crucially depends on the thickness of D1 layer. If atoms are positioned near the D0-air interface, the substantial variation of the normalized SE rate appears when rotating the polarized direction of atoms. These findings manifest that the atomic SE processes can be flexibly controlled by altering the thickness of the dielectric layer D1 or rotating the orientation of the polarization of atoms.

  11. Multiconfiguration pair-density functional theory: barrier heights and main group and transition metal energetics.

    Science.gov (United States)

    Carlson, Rebecca K; Li Manni, Giovanni; Sonnenberger, Andrew L; Truhlar, Donald G; Gagliardi, Laura

    2015-01-13

    Kohn-Sham density functional theory, resting on the representation of the electronic density and kinetic energy by a single Slater determinant, has revolutionized chemistry, but for open-shell systems, the Kohn-Sham Slater determinant has the wrong symmetry properties as compared to an accurate wave function. We have recently proposed a theory, called multiconfiguration pair-density functional theory (MC-PDFT), in which the electronic kinetic energy and classical Coulomb energy are calculated from a multiconfiguration wave function with the correct symmetry properties, and the rest of the energy is calculated from a density functional, called the on-top density functional, that depends on the density and the on-top pair density calculated from this wave function. We also proposed a simple way to approximate the on-top density functional by translation of Kohn-Sham exchange-correlation functionals. The method is much less expensive than other post-SCF methods for calculating the dynamical correlation energy starting with a multiconfiguration self-consistent-field wave function as the reference wave function, and initial tests of the theory were quite encouraging. Here, we provide a broader test of the theory by applying it to bond energies of main-group molecules and transition metal complexes, barrier heights and reaction energies for diverse chemical reactions, proton affinities, and the water dimerization energy. Averaged over 56 data points, the mean unsigned error is 3.2 kcal/mol for MC-PDFT, as compared to 6.9 kcal/mol for Kohn-Sham theory with a comparable density functional. MC-PDFT is more accurate on average than complete active space second-order perturbation theory (CASPT2) for main-group small-molecule bond energies, alkyl bond dissociation energies, transition-metal-ligand bond energies, proton affinities, and the water dimerization energy.

  12. Mg doping of InGaN layers grown by PA-MBE for the fabrication of Schottky barrier photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Pereiro, J; Redondo-Cubero, A; Fernandez-Garrido, S; Rivera, C; Navarro, A; Munoz, E; Calleja, E [Instituto de Sistemas Optoelectronicos y MicrotecnologIa, Universidad Politecnica de Madrid, E-28040 Madrid (Spain); Gago, R, E-mail: jpereiro@die.upm.e [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones CientIficas, E-28049 Madrid (Spain)

    2010-08-25

    This work reports on the fabrication of Schottky barrier based Mg-doped (In,Ga)N layers for fluorescence applications. Mg acceptors are used in order to compensate surface and bulk donors that prevent the fabrication of Schottky contacts on unintentionally doped (In,Ga)N layers grown by plasma-assisted molecular beam epitaxy (PA-MBE). Rectifying properties of the contacts exhibited a major improvement when (In,Ga)N : Mg was used. The electrical and optical measurements of the layers showed a hole concentration of up to 3 x 10{sup 19} holes cm{sup -3} with a Mg acceptor activation energy of {approx}60 meV. Back-illuminated photodiodes fabricated on 800 nm thick Mg-doped In{sub 0.18}Ga{sub 0.82}N layers exhibited a band pass photo-response with a rejection ratio >10{sup 2} between 420 and 470 nm and peak responsivities of 87 mA W{sup -1} at {approx}470 nm. The suitability of these photodiodes for fluorescence measurements was demonstrated.

  13. Layer-by-Layer Method for the Synthesis and Growth of Surface Mounted Metal-Organic Frameworks (SURMOFs

    Directory of Open Access Journals (Sweden)

    Osama Shekhah

    2010-02-01

    Full Text Available A layer-by-layer method has been developed for the synthesis of metal-organic frameworks (MOFs and their deposition on functionalized organic surfaces. The approach is based on the sequential immersion of functionalized organic surfaces into solutions of the building blocks of the MOF, i.e., the organic ligand and the inorganic unit. The synthesis and growth of different types of MOFs on substrates with different functionalization, like COOH, OH and pyridine terminated surfaces, were studied and characterized with different surface characterization techniques. A controlled and highly oriented growth of very homogenous films was obtained using this method. The layer-by-layer method offered also the possibility to study the kinetics of film formation in more detail using surface plasmon resonance and quartz crystal microbalance. In addition, this method demonstrates the potential to synthesize new classes of MOFs not accessible by conventional methods. Finally, the controlled growth of MOF thin films is important for many applications like chemical sensors, membranes and related electrodes.

  14. Layer-number dependent high-frequency vibration modes in few-layer transition metal dichalcogenides induced by interlayer couplings

    Science.gov (United States)

    Tan, Qing-Hai; Zhang, Xin; Luo, Xiang-Dong; Zhang, Jun; Tan, Ping-Heng

    2017-03-01

    Two-dimensional transition metal dichalcogenides (TMDs) have attracted extensive attention due to their many novel properties. The atoms within each layer in two-dimensional TMDs are joined together by covalent bonds, while van der Waals interactions combine the layers together. This makes its lattice dynamics layer-number dependent. The evolutions of ultralow frequency ( 50 cm‑1) vibration modes in few-layer TMDs and demonstrate how the interlayer coupling leads to the splitting of high-frequency vibration modes, known as Davydov splitting. Such Davydov splitting can be well described by a van der Waals model, which directly links the splitting with the interlayer coupling. Our review expands the understanding on the effect of interlayer coupling on the high-frequency vibration modes in TMDs and other two-dimensional materials. Project supported by the National Basic Research Program of China (No. 2016YFA0301200), the National Natural Science Foundation of China (Nos. 11225421, 11474277, 11434010, 61474067, 11604326, 11574305 and 51527901), and the National Young 1000 Talent Plan of China.

  15. CdTe nBn photodetectors with ZnTe barrier layer grown on InSb substrates

    Science.gov (United States)

    He, Zhao-Yu; Campbell, Calli M.; Lassise, Maxwell B.; Lin, Zhi-Yuan; Becker, Jacob J.; Zhao, Yuan; Boccard, Mathieu; Holman, Zachary; Zhang, Yong-Hang

    2016-09-01

    We have demonstrated an 820 nm cutoff CdTe nBn photodetector with ZnTe barrier layer grown on an InSb substrate. At room temperature, under a bias of -0.1 V, the photodetector shows Johnson and shot noise limited specific detectivity (D*) of 3 × 1013 cm Hz1/2/W at a wavelength of 800 nm and 2 × 1012 cm Hz1/2/W at 200 nm. The D* is optimized by using a top contact design of ITO/undoped-CdTe. This device not only possesses nBn advantageous characteristics, such as generation-recombination dark current suppression and voltage-bias-addressed two-color photodetection, but also offers features including responsivity enhancements by deep-depletion and by using a heterostructure ZnTe barrier layer. In addition, this device provides a platform to study nBn device physics at room temperature, which will help us to understand more sophisticated properties of infrared nBn photodetectors that may possess a large band-to-band tunneling current at a high voltage bias, because this current is greatly suppressed in the large-bandgap CdTe nBn photodetector.

  16. Metal separators coated with carbon/resin composite layers for PEFCs

    Energy Technology Data Exchange (ETDEWEB)

    Kitta, Shigehiro [Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4 Takeda, Kofu 400-8510 (Japan); Asktechnica Corp., 1488 Ichikawadaimon, Nishi-yatsushiro 409-3601 (Japan); Uchida, Hiroyuki [Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4 Takeda, Kofu 400-8510 (Japan); Watanabe, Masahiro [Clean Energy Research Center, University of Yamanashi, 4 Takeda, Kofu 400-8510 (Japan)

    2007-12-31

    A new type of metal separator coated with corrosion-resistant and electronically conductive carbon/resin composite layers has been developed. A flat, stainless steel plate was coated with a thin composite layer, and then ribs were formed of a similar composite over the thin layer as gas flow channels. The composite consisted of graphite, epoxy resin and a phenol hardener. By optimizing the combination and composition of materials, target values for the bulk electric conductivity and the chemical stability in hot water were cleared. The separator pieces exhibited a good corrosion resistance during soaking tests in 0.1 M H{sub 2}SO{sub 4} at 90 C over 2000 h or even at 120 C over 1200 h. The area-specific resistance of the separator coated with the thin protecting layer and the rib layer was less than 13.8 m{omega} cm{sup 2}. (author)

  17. Metallic conduction induced by direct anion site doping in layered SnSe2

    Science.gov (United States)

    Kim, Sang Il; Hwang, Sungwoo; Kim, Se Yun; Lee, Woo-Jin; Jung, Doh Won; Moon, Kyoung-Seok; Park, Hee Jung; Cho, Young-Jin; Cho, Yong-Hee; Kim, Jung-Hwa; Yun, Dong-Jin; Lee, Kyu Hyoung; Han, In-Taek; Lee, Kimoon; Sohn, Yoonchul

    2016-01-01

    The emergence of metallic conduction in layered dichalcogenide semiconductor materials by chemical doping is one of key issues for two-dimensional (2D) materials engineering. At present, doping methods for layered dichalcogenide materials have been limited to an ion intercalation between layer units or electrostatic carrier doping by electrical bias owing to the absence of appropriate substitutional dopant for increasing the carrier concentration. Here, we report the occurrence of metallic conduction in the layered dichalcogenide of SnSe2 by the direct Se-site doping with Cl as a shallow electron donor. The total carrier concentration up to ~1020 cm‑3 is achieved by Cl substitutional doping, resulting in the improved conductivity value of ~170 S·cm‑1 from ~1.7 S·cm‑1 for non-doped SnSe2. When the carrier concentration exceeds ~1019 cm‑3, the conduction mechanism is changed from hopping to degenerate conduction, exhibiting metal-insulator transition behavior. Detailed band structure calculation reveals that the hybridized s-p orbital from Sn 5s and Se 4p states is responsible for the degenerate metallic conduction in electron-doped SnSe2.

  18. Electric-Field Noise above a Thin Dielectric Layer on Metal Electrodes

    CERN Document Server

    Kumph, Muir; Rabl, Peter; Brownnutt, Michael; Blatt, Rainer

    2015-01-01

    The electric-field noise above a layered structure composed of a planar metal electrode covered by a thin dielectric is evaluated and it is found that the dielectric film considerably increases the noise level, in proportion to its thickness. Importantly, even a thin (mono) layer of a low-loss dielectric can enhance the noise level by several orders of magnitude compared to the noise above a bare metal. Close to this layered surface, the power spectral density of the electric field varies with the inverse fourth power of the distance to the surface, rather than with the inverse square, as it would above a bare metal surface. Furthermore, compared to a clean metal, where the noise spectrum does not vary with frequency (in the radio-wave and microwave bands), the dielectric layer can generate electric-field noise which scales in inverse proportion to the frequency. For various realistic scenarios, the noise levels predicted from this model are comparable to those observed in trapped-ion experiments. Thus, these...

  19. Sol-gel deposition of buffer layers on biaxially textured metal substances

    Science.gov (United States)

    Shoup, Shara S.; Paranthamam, Mariappan; Beach, David B.; Kroeger, Donald M.; Goyal, Amit

    2000-01-01

    A method is disclosed for forming a biaxially textured buffer layer on a biaxially oriented metal substrate by using a sol-gel coating technique followed by pyrolyzing/annealing in a reducing atmosphere. This method is advantageous for providing substrates for depositing electronically active materials thereon.

  20. Analysis of the electroluminescence features of silicon metal-insulator-semiconductor structures as a tool for diagnostics of the injection properties of a dielectric layer

    Science.gov (United States)

    Illarionov, Yu. Yu.; Vexler, M. I.; Isakov, D.; Fedorov, V. V.; Sing, Yew Kwang

    2013-10-01

    A technique for diagnostics of the injection properties of thin dielectric layers based on analysis of the data on silicon electroluminescence in a metal-insulator-semiconductor structure is proposed. The possibility of applying this technique to control the electron injection energy (in particular, when the barrier parameters are poorly known) is demonstrated by the example of samples with CaF2 and HfO2/SiO2. The results obtained are important for application of the insulators under study in microelectronic devices.

  1. Resistive switching in a metal-insulator-metal device with γ-APTES as the insulator layer

    Science.gov (United States)

    Lin, Jing-Jenn; Lin, Shih-Hung; Wu, You-Lin

    2017-10-01

    Gamma-aminopropyltriethoxysilane (γ-APTES) is an organosilane material commonly used for biomedical sensing. Sensors with a γ-APTES surface layer have been reported for use in pH, DNA, and cell detection. However, no application of γ-APTES on resistive switching random access memory (RRAM) devices has yet been reported. In this paper, we report, for the first time, the resistive switching characteristics of using γ-APTES as the insulator layer in an RRAM device. The resistive switching of the γ-APTES layer embedded with ZnO nanoparticles is also investigated in this work. A unipolar resistive switching characteristic is found when the γ-APTES is employed as an insulator layer in a device with a metal-insulator-metal (MIM) structure. The stability and reliability of the resistive switching characteristics of the device can be improved after adding zinc oxide (ZnO) nanoparticles at the expense of reducing the ratio of the resistance of a high-resistance state (RHRS) to the resistance of a low-resistance state (RLRS).

  2. Growth mechanism of pulsed laser fabricated few-layer MoS₂ on metal substrates.

    Science.gov (United States)

    Loh, Tamie A J; Chua, Daniel H C

    2014-09-24

    Pulsed laser deposition (PLD) on metal substrates has recently been discovered to present an alternative method for producing highly crystalline few-layer MoS2. However, not every metal behaves in the same manner during film growth, and hence, it is crucial that the ability of various metals to produce crystalline MoS2 be thoroughly investigated. In this work, MoS2 was deposited on metal substrates, Al, Ag, Ni, and Cu, using a pulsed laser. Highly crystalline few-layer MoS2 was successfully grown on Ag, but is absent in Al, Ni, and Cu under specific growth conditions. This discrepancy was attributed to either excessively strong or insufficient adlayer-substrate interactions. In the case of Al, the effects of the strong interface interactions can be offset by increasing the amount of source atoms supplied, thereby producing semicrystalline few-layer MoS2. The results show that despite PLD being a physical vapor deposition technique, both physical and chemical processes play an important role in MoS2 growth on metal substrates.

  3. Thermal Rayleigh-Marangoni convection in a three-layer liquid-metal-battery model

    Science.gov (United States)

    Köllner, Thomas; Boeck, Thomas; Schumacher, Jörg

    2017-05-01

    The combined effects of buoyancy-driven Rayleigh-Bénard convection (RC) and surface tension-driven Marangoni convection (MC) are studied in a triple-layer configuration which serves as a simplified model for a liquid metal battery (LMB). The three-layer model consists of a liquid metal alloy cathode, a molten salt separation layer, and a liquid metal anode at the top. Convection is triggered by the temperature gradient between the hot electrolyte and the colder electrodes, which is a consequence of the release of resistive heat during operation. We present a linear stability analysis of the state of pure thermal conduction in combination with three-dimensional direct numerical simulations of the nonlinear turbulent evolution on the basis of a pseudospectral method. Five different modes of convection are identified in the configuration, which are partly coupled to each other: RC in the upper electrode, RC with internal heating in the molten salt layer, and MC at both interfaces between molten salt and electrode as well as anticonvection in the middle layer and lower electrode. The linear stability analysis confirms that the additional Marangoni effect in the present setup increases the growth rates of the linearly unstable modes, i.e., Marangoni and Rayleigh-Bénard instability act together in the molten salt layer. The critical Grashof and Marangoni numbers decrease with increasing middle layer thickness. The calculated thresholds for the onset of convection are found for realistic current densities of laboratory-sized LMBs. The global turbulent heat transfer follows scaling predictions for internally heated RC. The global turbulent momentum transfer is comparable with turbulent convection in the classical Rayleigh-Bénard case. In summary, our studies show that incorporating Marangoni effects generates smaller flow structures, alters the velocity magnitudes, and enhances the turbulent heat transfer across the triple-layer configuration.

  4. Heat-resistant organic molecular layer as a joint interface for metal reduction on plastics surfaces

    Science.gov (United States)

    Sang, Jing; Aisawa, Sumio; Hirahara, Hidetoshi; Kudo, Takahiro; Mori, Kunio

    2016-04-01

    Heat-resistant organic molecular layers have been fabricated by triazine-based silane coupling agent for metal reduction on plastic surfaces using adsorption method. These molecular layers were used as an interfacial layer between polyamide (PA6) and metal solution to reduce Ag+ ion to Ag0. The interfacial behaviors of triazine molecular layer at the interfaces between PA6 and Ag solution were investigated using quartz crystal microbalance (QCM). The kinetics of molecular adsorption on PA6 was investigated by using triazine-based silane coupling agent solutions at different pH and concentration. X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and local nano thermal analysis were employed to characterize the surfaces and interfaces. The nano thermal analysis results show that molecular layers of triazine-based silane coupling agent greatly improved heat resistance of PA6 resin from 170 °C up to 230 °C. This research developed an in-depth insight for molecular behaviors of triazine-based silane coupling agent at the PA6 and Ag solution interfaces and should be of significant value for interfacial research between plastics and metal solution in plating industry.

  5. Electronic and magnetic properties of single-layer M P X3 metal phosphorous trichalcogenides

    Science.gov (United States)

    Chittari, Bheema Lingam; Park, Youngju; Lee, Dongkyu; Han, Moonsup; MacDonald, Allan H.; Hwang, Euyheon; Jung, Jeil

    2016-11-01

    We survey the electronic structure and magnetic properties of two-dimensional (2D) M P X3 (M =V,Cr,Mn,Fe,Co,Ni,Cu,Zn, and X =S,Se,Te ) transition-metal chalcogenophosphates to shed light on their potential role as single-layer van der Waals materials that possess magnetic order. Our ab initio calculations predict that most of these single-layer materials are antiferromagnetic semiconductors. The band gaps of the antiferromagnetic states decrease as the atomic number of the chalcogen atom increases (from S to Se to Te), leading in some cases to half-metallic ferromagnetic states or to nonmagnetic metallic states. We find that the competition between antiferromagnetic and ferromagnetic states can be substantially influenced by gating and by strain engineering. The sensitive interdependence we find between magnetic, structural, and electronic properties establishes the potential of this 2D materials class for applications in spintronics.

  6. First-principles study of the noble metal-doped BN layer

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yungang; Yang, Ping; Sun, Xin; Wang, Zhiguo; Zu, Xiaotao T.; Gao, Fei

    2011-04-18

    Intriguing electronic and magnetic properties of BN layer with noble metal (Pd, Pt, Ag and Au) doping are obtained by first-principles calculations. Adsorbed Pd (or Pt) reduces the band gap of BN sheet owing to the induction of impurity states. The unpaired electrons in the Ag (or Au)-adsorbed and the Pd (or Pt)-substituted BN layers are polarized, and thus exhibit a magnetic moment of 1.0 µB, leading to these BN configurations to be magnetic semiconductors. The half-metallic feature of the Ag-substituted BN layer, along with the delocalization of spin states, renders this configuration an excellent spin filter material. Thus, these findings offer a unique opportunity for developing BN-based nanoscale devices.

  7. Two approaches for enhancing the hydrogenation properties of palladium: Metal nanoparticle and thin film over layers

    Indian Academy of Sciences (India)

    Manika Khanuja; B R Mehta; S M Shivaprasad

    2008-11-01

    In the present study, two approaches have been used for enhancing the hydrogenation properties of Pd. In the first approach, metal thin film (Cu, Ag) has been deposited over Pd and hydrogenation properties of bimetal layer Cu (thin film)/Pd(thin film) and Ag(thin film)/Pd(thin film) have been studied. In the second approach, Ag metal nanoparticles have been deposited over Pd and hydrogenation properties of Ag (nanoparticle)/Pd (thin film) have been studied and compared with Ag(thin film)/Pd(thin film) bimetal layer system. The observed hydrogen sensing response is stable and reversible over a number of hydrogen loading and deloading cycles in both bimetallic systems. Alloying between Ag and Pd is suppressed in case of Ag(nanoparticle)/Pd(thin film) bimetallic layer on annealing as compared to Ag (thin film)/Pd(thin film).

  8. Effect of nitrogen content on the degradation mechanisms of thin Ta-Si-N diffusion barriers for Cu metallization

    Energy Technology Data Exchange (ETDEWEB)

    Huebner, R. [Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstrasse 20, D-01069 Dresden (Germany)]. E-mail: rhuebner@uamail.albany.edu; Hecker, M. [Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstrasse 20, D-01069 Dresden (Germany); Mattern, N. [Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstrasse 20, D-01069 Dresden (Germany); Hoffmann, V. [Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstrasse 20, D-01069 Dresden (Germany); Wetzig, K. [Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstrasse 20, D-01069 Dresden (Germany); Heuer, H. [Dresden University of Technology, Semiconductor and Microsystems Technology Laboratory, D-01062 Dresden (Germany); Wenzel, Ch. [Dresden University of Technology, Semiconductor and Microsystems Technology Laboratory, D-01062 Dresden (Germany); Engelmann, H.-J. [AMD Saxony LLC and Co. KG, Materials Analysis Department, D-01330 Dresden (Germany); Gehre, D. [AMD Saxony LLC and Co. KG, Materials Analysis Department, D-01330 Dresden (Germany); Zschech, E. [AMD Saxony LLC and Co. KG, Materials Analysis Department, D-01330 Dresden (Germany)

    2006-04-03

    The effect of the nitrogen content on the thermal stability and degradation mechanisms of Ta-Si-N diffusion barriers was studied using methods that prove Cu interdiffusion. On the one hand, glancing angle X-ray diffraction was applied to detect Cu{sub 3}Si formation after annealing of Cu/Ta-Si-N/Si layer stacks. On the other hand, a combined secondary ion mass spectroscopy and transmission electron microscopy analysis of Ta-Si-N/Cu/Ta-Si-N/SiO{sub 2}/Si samples was performed. For a detailed investigation of the microstructure evolution, the crystallization behavior of both Cu-capped and uncapped Ta-Si-N/Si samples was analyzed using X-ray diffraction. In the case of an uncapped Ta{sub 73}Si{sub 27} film, Si interdiffusion from the substrate precedes the layer crystallization. The substrate influence on the crystallization process decreases with increasing N content x {sub N} of the Ta-Si-N layer. Using Cu/Ta-Si-N/Si samples, a critical temperature for Cu silicide formation was determined. This temperature increases with increasing N content of the Ta-Si-N barrier. In the case of Ta-Si-N films with x {sub N} > 25 at.%, Cu interdiffusion into the substrate occurs before a significant barrier crystallization is observed. For Ta-Si-N layers with x {sub N} {<=} 25 at.%, no indications for Cu diffusion before crystalline phase formation were detected.

  9. On the optimization of asymmetric barrier layers in InAlGaAs/AlGaAs laser heterostructures on GaAs substrates

    DEFF Research Database (Denmark)

    Zhukov, A. E.; Asryan, L. V.; Semenova, Elizaveta;

    2015-01-01

    Band offsets at the heterointerface are calculated for various combinations of InAlGaAs/AlGaAs heteropairs that can be synthesized on GaAs substrates in the layer-by-layer pseudomorphic growth mode. Patterns which make it possible to obtain an asymmetric barrier layer providing the almost obstruc...... for the critical thickness of the indium-containing quaternary solid solution....

  10. Influence of source and drain contacts on the properties of indium-gallium-zinc-oxide thin-film transistors based on amorphous carbon nanofilm as barrier layer.

    Science.gov (United States)

    Luo, Dongxiang; Xu, Hua; Zhao, Mingjie; Li, Min; Xu, Miao; Zou, Jianhua; Tao, Hong; Wang, Lei; Peng, Junbiao

    2015-02-18

    Amorphous indium-gallium-zinc-oxide thin film transistors (α-IGZO TFTs) with damage-free back channel wet-etch (BCE) process were achieved by introducing a carbon nanofilm as a barrier layer. We investigate the effects of different source-and-drain (S/D) materials on TFT performance. We find the TFT with Ti/C S/D electrodes exhibits a superior performance with higher output current, lower threshold voltage, and higher effective electron mobility compared to that of Mo/C S/D electrodes. Transmittance electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are employed to analysis the interfacial interaction between S/D metal/C/α-IGZO layers. The results indicate that the better performance of TFTs with Ti/C electrodes should be attributed to the formations of Ti-C and Ti-O at the Ti/C-contact regions, which lead to a lower contact resistance, whereas Mo film is relatively stable and does not react easily with C nanofilm, resulting in a nonohmic contact behavior between Mo/C and α-IGZO layer. However, both kinds of α-IGZO TFTs show good stability under thermal bias stress, indicating that the inserted C nanofilms could avoid the impact on the α-IGZO channel regions during S/D electrodes formation. Finally, we successfully fabricated a high-definition active-matrix organic lighting emitting diode prototype driven by α-IGZO TFTs with Ti/C electrodes in a pilot line.

  11. Electronic and phonon bandstructures of pristine few layer and metal doped graphene using first principles calculations

    Directory of Open Access Journals (Sweden)

    Sanjeev K. Gupta

    2013-03-01

    Full Text Available In the frame work of density functional theoretical calculations, the electronic and lattice dynamical properties of graphene (multilayers and supercell have been systematically investigated and analyzed using the plane wave pseudopotentials within the generalized gradient approximation and local density approximation functional. We have also studied the functionalization of graphene by adsorption and absorption of transition metals like Al and Ag. We find that the electronic properties exhibit large sensitivity to the number of layers and doping. The Al and Ag doped graphene exhibits peak at Fermi level in the density of states arising from the flat bands near Fermi level. The bonding of metal atoms and graphene leads to a charge transfer between them and consequently shift Fermi level with respect to the conical point at K-point. The adsorption of Ag/Al atoms suggests an effective interaction between the adatoms and graphene layers without disturbing the original graphene structure of lower graphene layers. Compared to single layer graphene, the optical phonon E2g mode and out of plane ZA mode at Γ-point splits in the bi-, tri- and four- layer graphene. We observe a shift for highest optical branch at Dirac K- point. We find that the different derivatives of graphene have different phonon dispersion relations. We demonstrate that there is removal of degeneracy of ZO/ZA modes at K- point with transition metal doping. The highest optical phonon branch becomes flat at Dirac point with doping of transition metals. Our study points that the substituted graphene sheets can have potential applications in ordered-disordered separated quantum films with two to four layers of atoms and new nano devices using graphene.

  12. Modeling the barrier-layer formation in the South-Eastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Durand, F.; Shankar, D.; DeBoyer Montegut, C.; Shenoi, S.S.C.; Blanke, B.; Madec, G.

    by two complementary processes, the arrival of low-salinity surface waters that are cooled en route to the SEAS and downwelling of waters mostly local to the SEAS in the subsurface layers. The surface waters are partly of Bay-of-Bengal origin...

  13. Growth and properties of LPCVD W-Si-N barrier layers

    NARCIS (Netherlands)

    Bystrova, S.; Holleman, J.; Woerlee, P.H.

    2001-01-01

    In this work the low-temperature low pressure chemical vapour deposition (LPCVD) of W�Si�N compounds in the WF6�NF3�SiH4�Ar system is presented. Layers were deposited on oxidised Si-wafers at 385 and 250

  14. Plasma-Assisted ALD of an Al2O3 Permeation Barrier Layer on Plastic

    Institute of Scientific and Technical Information of China (English)

    雷雯雯; 李兴存; 陈强; 王正铎

    2012-01-01

    Atomic layer deposition (ALD) technique is used in the preparation of organic/inorganic layers, which requires uniform surfaces with their thickness down to several nanometers. For film with such thickness, the growth mode defined as the arrangement of clusters on the surface during the growth is of significance. In this work, Al2O3 thin film was deposited on various interfacial species of pre-treated polyethylene terephthalate (PET, 12 μm) by plasma assisted atomic layer deposition (PA-ALD), where trimethyl aluminium was used as the Al precursor and O2 as the oxygen source. The interracial species, -NH3, -OH, and -COOH as well as SiCHO (derived from monomer of HMDSO plasma), were grafted previously by plasma and chemical treatments. The growth mode of PA-ALD Al2O3 was then investigated in detail by combining results from in-situ diagnosis of spectroscopic ellipsometry (SE) and ex-situ characterization of as-deposited layers from the morphologies scanned by atomic force microscopy (AFM). In addition, the oxygen transmission rates (OTR) of the original and treated plastic films were measured. The possible reasons for the dependence of the OTR values on the surface species were explored.

  15. Diffusion barrier property of MnSi{sub x}O{sub y} layer formed by chemical vapor deposition for Cu advanced interconnect application

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Mai Phuong, E-mail: nmphuong46@gmail.com; Sutou, Yuji; Koike, Junichi, E-mail: koikej@material.tohoku.ac.jp

    2015-04-01

    An amorphous manganese oxide layers formed by chemical vapor deposition have been studied as a copper diffusion barrier. The thermal stability of the barrier layer was assessed by annealing Cu/MnSi{sub x}O{sub y}/SiO{sub 2}/Si samples at 400 °C for various times up to 10 h. Transmission electron microscopy, energy-dispersive X-ray spectroscopy (EDX), secondary ion mass spectroscopy (SIMS), capacitance-voltage and current–voltage measurements were performed. Failure of the barrier property is marked by observing the copper peak appearing in EDX and SIMS spectra data from the SiO{sub 2} region. Amorphous MnSi{sub x}O{sub y} barrier with a thickness of 1.2 nm has failed in preventing Cu diffusion into SiO{sub 2} substrate after anneal at 400°C in vacuum for 1h, as proven by the presence of Cu in the dielectric (SiO{sub 2}) layer. However, the amorphous MnSi{sub x}O{sub y} with the thickness of 2.0 nm barrier was thermally stable and could prevent Cu from inter-diffusion to the SiO{sub 2} substrate after annealing at 400 °C even up to 10 h. - Highlights: • Amorphous manganese silicate layer has been studied as a copper diffusion barrier. • The 1.2 nm-thick Mn oxide layer is too thin to become a diffusion barrier. • Good thermal stability of 2.0 nm-thick manganese silicate layer.

  16. Formation of nanocrystalline surface layers in various metallic materials by near surface severe plastic deformation

    Directory of Open Access Journals (Sweden)

    Masahide Sato, Nobuhiro Tsuji, Yoritoshi Minamino and Yuichiro Koizumi

    2004-01-01

    Full Text Available The surface of the various kinds of metallic materials sheets were severely deformed by wire-brushing at ambient temperature to achieve nanocrystalline surface layer. The surface layers of the metallic materials developed by the near surface severe plastic deformation (NS-SPD were characterized by means of TEM. Nearly equiaxed nanocrystals with grain sizes ranging from 30 to 200 nm were observed in the near surface regions of all the severely scratched metallic materials, which are Ti-added ultra-low carbon interstitial free steel, austenitic stainless steel (SUS304, 99.99 wt.%Al, commercial purity aluminum (A1050 and A1100, Al–Mg alloy (A5083, Al-4 wt.%Cu alloy, OFHC-Cu (C1020, Cu–Zn alloy (C2600 and Pb-1.5%Sn alloy. In case of the 1050-H24 aluminum, the depth of the surface nanocrystalline layer was about 15 μm. It was clarified that wire-brushing is an effective way of NS-SPD, and surface nanocrystallization can be easily achieved in most of metallic materials.

  17. Evaluation of a barrier to inhibit lesser mealworm (Coleoptera: Tenebrionidae) and dermestidae movement in high-rise, caged-layer poultry facilities.

    Science.gov (United States)

    Kaufman, Phillip E; Reasor, Colleen; Murray, Kathleen D; Waldron, J Keith; Rutz, Donald A

    2005-10-01

    An evaluation of a mechanical barrier to prevent movement of adult and larval lesser mealworm, Alphitobius diaperinus (Panzer); larder beetle, Dermestes lardarius L.; and hide beetle, Dermestes maculatus De Geer was conducted in caged-layer poultry facilities in New York and Maine. The barrier, a plastic collar wrapped around building support posts, proved highly effective at preventing movement of adult lesser mealworms. Significantly more lesser mealworm larvae were recovered from cardboard collar beetle traps placed below both washed and unwashed barriers than from traps placed above washed and unwashed barriers. Similarly, significantly more adult Dermestes were recovered from traps placed below washed barriers than from above both washed and unwashed barriers. The level of fly specking on the barrier was found to have no significant impact on the numbers of adult lesser mealworms and adult and larval Dermestes recovered either above or below barriers. Fly specking level did significantly impact the numbers of lesser mealworm larvae recovered above the barrier. Although washed barriers provided the greatest deterrent to adult lesser mealworms, the presence of the barrier, regardless of the level of fly specking, provided a significant deterrent to beetle climbing success. Washed barriers further reduced climbing success by lesser mealworm larvae by 17%, Dermestes adults by 7-28%, and Dermestes larvae by 33-38%. The high level of climbing observed by adult lesser mealworms suggests that the impact of adult beetle movement toward birds should be considered in its importance in building damage, disease transmission, feed infestation, and bird productivity and health. Observations on cost and maintenance of the barrier are discussed.

  18. Exchange coupling in metallic multilayers with a top FeRh layer

    Science.gov (United States)

    Yamada, S.; Tanikawa, K.; Hirayama, J.; Kanashima, T.; Taniyama, T.; Hamaya, K.

    2016-05-01

    We study magnetic properties of metallic multilayers with FeRh/ferromagnet interfaces grown by low-temperature molecular beam epitaxy. Room-temperature coercivity of the ferromagnetic layers is significantly enhanced after the growth of FeRh, proving the existence of the exchange coupling between the antiferromagnetic FeRh layer and the ferromagnetic layer. However, exchange bias is not clearly observed probably due to the presence of disordered structures, which result from the lattice strain at the FeRh/ferromagnet interfaces due to the lattice mismatch. We infer that the lattice matched interface between FeRh and ferromagnetic layers is a key parameter for controlling magnetic switching fields in such multilayer systems.

  19. Properties of native ultrathin aluminium oxide tunnel barriers

    CERN Document Server

    Gloos, K; Pekola, J P

    2003-01-01

    We have investigated planar metal-insulator-metal tunnel junctions with aluminium oxide as the dielectricum. These oxide barriers were grown on an aluminium electrode in pure oxygen at room temperature till saturation. By applying the Simmons model we derived discrete widths of the tunnelling barrier, separated by DELTA s approx 0.38 nm. This corresponds to the addition of single layers of oxygen atoms. The minimum thickness of s sub 0 approx 0.54 nm is then due to a double layer of oxygen. We found a strong and systematic dependence of the barrier height on the barrier thickness. Breakdown fields up to 5 GV m sup - sup 1 were reached. They decreased strongly with increasing barrier thickness. Electrical breakdown could be described by a metal-insulator like transition of the dielectric barrier due to the large density of tunnelling electrons.

  20. Thermoelastic characteristics of thermal barrier coatings with layer thickness and edge conditions through mathematical analysis.

    Science.gov (United States)

    Go, Jaegwi; Myoung, Sang-Won; Lee, Je-Hyun; Jung, Yeon-Gil; Kim, Seokchan; Paik, Ungyu

    2014-10-01

    The thermoelastic behaviors of such as temperature distribution, displacements, and stresses in thermal barrier coatings (TBCs) are seriously influenced by top coat thickness and edge conditions, which were investigated based on the thermal and mechanical properties of plasma-sprayed TBCs. A couple of governing partial differential equations were derived based on the thermoelastic theory. Since the governing equations are too involved to solve analytically, a finite volume method was developed to obtain approximations. The thermoelastic characteristics of TBCs with the various thicknesses and microstructures were estimated through mathematical approaches with different edge conditions. The results demonstrated that the top coat thickness and the edge condition in theoretical analysis are crucial factors to be considered in controlling the thermoelastic characteristics of plasma-sprayed TBCs.

  1. Mesoporous layer-by-layer ordered nanohybrids of layered double hydroxide and layered metal oxide: highly active visible light photocatalysts with improved chemical stability.

    Science.gov (United States)

    Gunjakar, Jayavant L; Kim, Tae Woo; Kim, Hyo Na; Kim, In Young; Hwang, Seong-Ju

    2011-09-28

    Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O(2) generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) and layered titanium oxide. The layer-by-layer ordering of two kinds of 2D nanosheets is evidenced by powder X-ray diffraction and cross-sectional high resolution-transmission electron microscopy. Upon the interstratification process, the original in-plane atomic arrangements and electronic structures of the component nanosheets remain intact. The obtained heterolayered nanohybrids show a strong absorption of visible light and a remarkably depressed photoluminescence signal, indicating an effective electronic coupling between the two component nanosheets. The self-assembly between 2D inorganic nanosheets leads to the formation of highly porous stacking structure, whose porosity is controllable by changing the ratio of layered titanate/Zn-Cr-LDH. The resultant heterolayered nanohybrids are fairly active for visible light-induced O(2) generation with a rate of ∼1.18 mmol h(-1) g(-1), which is higher than the O(2) production rate (∼0.67 mmol h(-1) g(-1)) by the pristine Zn-Cr-LDH material, that is, one of the most effective visible light photocatalysts for O(2) production, under the same experimental condition. This result highlights an excellent functionality of the Zn-Cr-LDH-layered titanate nanohybrids as efficient visible light active photocatalysts. Of prime interest is that the chemical stability of the Zn-Cr-LDH is significantly improved upon the hybridization, a result of the protection of the LDH lattice by highly stable titanate layer. The present findings clearly demonstrate that the layer-by-layer-ordered assembly between inorganic 2D nanosheets is quite effective not only in improving the photocatalytic activity of the component semiconductors but also in synthesizing novel porous LDH-based hybrid materials with improved chemical

  2. Micro-layers of polystyrene film preventing metal oxidation: implications in cultural heritage conservation

    Science.gov (United States)

    Giambi, Francesca; Carretti, Emiliano; Dei, Luigi; Baglioni, Piero

    2014-12-01

    Protection of surfaces directly exposed to the detrimental action of degradative agents (i.e. oxygen, air pollutants and bacteria) is one of the most important challenges in the field of conservation of works of art. Metallic objects are subjected to specific surface corrosion phenomena that, over the years, make mandatory the research of innovative materials that should avoid the direct contact between the metal surface and the weathering agents. In this paper, the set-up, characterisation and application of a new reversible material for preserving metal artefacts are reported. Micro-layers constituted of low-adhesive polystyrene (PS) films obtained from recycling waste packaging materials made of expanded PS were studied. The morphology and thickness of PS films were characterised by optical, atomic force and scanning electron microscopy (SEM). A further check on thickness was carried out by means of visible spectrophotometry doping the films with a hydrophobic dye. Thermal properties of the PS micro-layers were studied by means of differential scanning calorimetry coupled with optical microscopy. Permeability of the PS films to water vapour was also determined. The potential of the low-adhesive PS films, that enabled an easy removal in case of film deterioration, for preventing metal oxidation was investigated on brass specimens by simulating standard artificial corrosion programmes. Morphological and chemical (coupling the energy-dispersive X-rays spectrometry to SEM measurements) analyses carried out on these metal samples showed promising results in terms of surface protection against corrosion.

  3. The effect of doping (Mn,B)3O4 materials as protective layers in different metallic interconnects for Solid Oxide Fuel Cells

    Science.gov (United States)

    Miguel-Pérez, Verónica; Martínez-Amesti, Ana; Nó, María Luisa; Larrañaga, Aitor; Arriortua, María Isabel

    2013-12-01

    Spinel oxides with the general formula of (Mn,B)3O4 (B = Co, Fe) were used as barrier materials between the cathode and the metallic interconnect to reduce the rate of cathode degradation by Cr poisoning. The effect of doping at the B position was investigated terms of microstructure and electrical conductivity to determine its behaviour and effectiveness as a protective layer in contact with three metallic materials (Crofer 22 APU, SS430 and Conicro 4023 W 188). The analysis showed that the use of these materials considerably decreased the reactivity and diffusion of Cr between the cathode and the metallic interconnects. The protective layer doped with Fe at the B position exhibited the least amount of reactivity with the interconnector and cathode materials. The worst results were observed for SS430 cells coated with a protective layer perhaps due to their low Cr content. The Crofer 22 APU and Conicro 4023 W 188 samples exhibited very similar conductivity results in the presence of the MnCo1.9Fe0.1O4 protective coating. As a result, these two material combinations are a promising option for use as bipolar plates in SOFC.

  4. Atomic and electronic structure of CdTe/metal (Cu, Al, Pt) interfaces and their influence to the Schottky barrier

    Science.gov (United States)

    Odkhuu, Dorj; Miao, Mao-sheng; Aqariden, F.; Grein, Christoph; Kioussis, Nicholas

    2016-11-01

    Schottky barrier heights (SBHs) and other features of the interfaces are determining factors for the performance of the CdTe based high-energy photon detectors. Although known for long time that SBH is sensitive to surface treatment and metal contact growth method, there is a lack of understanding of the effect of the atomic and electronic structures of CdTe/metal interface on the SBH. Employing first-principles electronic structure calculations, we have systematically studied the structural stability and electronic properties of a number of representing structures of Cd Terminated CdTe/metal (Cu, Pt, and Al) interfaces. Comparison of the total energies of the various optimized structural configurations allows to identify the existence of Te-metal alloy formation at the interface. The SBHs of Cu, Pt, and Al metal contacts with a number of stable interface structures are determined by aligning the band edges of bulk CdTe with the Fermi level of the metal/CdTe system. We find that the metal-induced states in the gap play an essential role in determining the SBH.

  5. Post-assembly transformations of porphyrin-containing metal-organic framework (MOF) films fabricated via automated layer-by-layer coordination

    KAUST Repository

    So, Monica

    2015-01-01

    Herein, we demonstrate the robustness of layer-by-layer (LbL)-assembled, pillared-paddlewheel-type MOF films toward conversion to new or modified MOFs via solvent-assisted linker exchange (SALE) and post-assembly linker metalation. Further, we show that LbL synthesis can afford MOFs that have proven inaccessible through other de novo strategies.

  6. Layer-by-Layer Assembled Films of Perylene Diimide- and Squaraine-Containing Metal-Organic Framework-like Materials: Solar Energy Capture and Directional Energy Transfer

    NARCIS (Netherlands)

    Park, H. J.; So, M. C.; Gosztola, D.; Wiederrecht, G. P.; Emery, J. D.; Martinson, A. B. F.; Er, S.; Wilmer, C. E.; Vermeulen, N. A.; Aspuru-Guzik, A.; Stoddart, J. F.; Farha, O. K.; Hupp, J. T.

    2016-01-01

    We demonstrate that thin films of metal organic framework (MOF)-like materials, containing two perylenedlimides (PDICl4, PDIOPh2) and a squaraine dye (S1); can be fabricated by, layer-by-layer assembly (LbL). Interestingly, these LbL films absorb across the visible light region (400-750 nm) and

  7. Chromatographic separation studies of penicillins, cephalosporins and carbapenems on transition-metal silicate modified silica layers.

    Science.gov (United States)

    Singh, Dhruv K; Maheshwari, Gunjan

    2012-01-01

    The chromatographic behavior of penicillins, cephalosporins and carbapenems has been studied on the thin layers of transition-metal ion (viz. Ni(2+)/Zn(2+)/Cu(2+)/Co(2+)) silicate modified silica. Transition-metal silicate (3.92%) and silica (96.08%) were found to be optimum and resulted in spherical-compact spots and improved resolution of the analytes. The effect of various mobile phases was also investigated. The chromatograms were visualized as yellow spots by placing in an I(2)-chamber. The method has been found to be reproducible and convenient for routine analysis.

  8. First-principles study of the dipole layer formation at metal-organic interfaces

    OpenAIRE

    2009-01-01

    We study the dipole layer formed at metal-organic interfaces by means of first-principles calculations. Interface dipoles are monitored by calculating the work function change of Au, Ag, Al, Mg and Ca surfaces upon adsorption of a monolayer of PTCDA (3,4,9,10-perylene-tetra-carboxylic-di-anhydride), perylene or benzene molecules. Adsorption of PTCDA leads to pinning of the work function for a range of metal substrates. It gives interface dipoles that compensate for the difference in the clean...

  9. Transient temperature of liquid on micro metal layer heated by pulsed laser

    Science.gov (United States)

    Li, Ji; Zhang, Zhengfang; Liu, Dengying

    1999-06-01

    In this paper the transient temperature of liquid on micro metal layer heated by pulsed high energy laser is simulated by numerical method, especially around the theoretical homogeneous boiling point(THBP). The relationship between temperature rising rate and laser fluence is obtained; and under different temperature rising rate the distributions of temperature in liquid and metal around the THBP are obtained. With numerical simulation the relation between the temperature rising rate and laser parameters (fluence and pulse width) is known and so in the future the rapid transient boiling phenomenon could be studied and analyzed.

  10. Transient Temperature of Liquid on Micro Metal Layer Heated by Pulsed Laser

    Institute of Scientific and Technical Information of China (English)

    LiJi; ZhangZhengfangtffu

    1999-01-01

    In this paper the transient temperature of liquid on micro metal layer heated by pulsed high energy laser is simulated by numerical method ,especially around the theoretical homogeneous boiling point (THBP),The relationship between temperature rising rate and laser fluence is obtained;and under different temperature rising rate the distributions of temperature in liquid and metal around the THBP are obtained.With numerical simulation the relation between the temperature rising rate and laser parameters(fluence and pulse width)is known and so in the future the rapid transient boiling phenomenon could be studed and analyzed.

  11. Copper zinc tin sulfide layers prepared from solution processable metal dithiocarbamate precursors

    Energy Technology Data Exchange (ETDEWEB)

    Edler, Michael [Institute for Chemistry and Technology of Materials, Graz University of Technology, Stremayrgasse 9, 8010 Graz (Austria); Christian Doppler Laboratory for Nanocomposite Solar Cells, Graz University of Technology and NanoTecCenter Weiz, Forschungsgesellschaft mbH (Austria); Rath, Thomas, E-mail: thomas.rath@tugraz.at [Institute for Chemistry and Technology of Materials, Graz University of Technology, Stremayrgasse 9, 8010 Graz (Austria); Christian Doppler Laboratory for Nanocomposite Solar Cells, Graz University of Technology and NanoTecCenter Weiz, Forschungsgesellschaft mbH (Austria); Schenk, Alexander [Institute for Chemistry and Technology of Materials, Graz University of Technology, Stremayrgasse 9, 8010 Graz (Austria); Fischereder, Achim [Institute for Chemistry and Technology of Materials, Graz University of Technology, Stremayrgasse 9, 8010 Graz (Austria); Christian Doppler Laboratory for Nanocomposite Solar Cells, Graz University of Technology and NanoTecCenter Weiz, Forschungsgesellschaft mbH (Austria); Haas, Wernfried [Christian Doppler Laboratory for Nanocomposite Solar Cells, Graz University of Technology and NanoTecCenter Weiz, Forschungsgesellschaft mbH (Austria); Institute for Electron Microscopy and Fine Structure Research, Graz University of Technology, Steyrergasse 17, 8010 Graz (Austria); Edler, Matthias [Chair of Chemistry of Polymeric Materials, University of Leoben, Otto Gloeckel-Strasse 2, 8700 Leoben (Austria); Chernev, Boril [Institute for Electron Microscopy and Fine Structure Research, Graz University of Technology, Steyrergasse 17, 8010 Graz (Austria); Kunert, Birgit [Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz (Austria); Hofer, Ferdinand [Institute for Electron Microscopy and Fine Structure Research, Graz University of Technology, Steyrergasse 17, 8010 Graz (Austria); and others

    2012-10-15

    In this contribution we present a solution based route toward copper zinc tin sulfide - CZTS - layers using metal dithiocarbamate precursors. We focus on the synthesis of the precursor materials as well as on the fabrication of thin CZTS layers at low temperatures of 350 Degree-Sign C and their characterization. Powder X-ray diffraction measurements show that a precursor solution containing an excess of the zinc precursor, compared to the Cu and Sn precursors, has to be used to obtain CZTS films without secondary phases. Thus, the prepared films are Zn-rich, which is beneficial for solar cell applications. Raman as well as X-ray photoelectron spectroscopy studies confirm the formation of CTZS. No clear evidence for free ZnS has been found. Electron microscopy shows agglomerates of 10 nm-sized crystallites forming spherical particles with a diameter between 50 nm and 400 nm. The prepared films possess high optical absorption (>1.10{sup 4} cm{sup -1}) and an optical band gap of approximately 1.6 eV. Highlights: Black-Right-Pointing-Pointer CZTS layers are prepared from metal dithiocarbamate precursor solu-tions. Black-Right-Pointing-Pointer No additional sulfur sources or capping agents are necessary. Black-Right-Pointing-Pointer Prepared CZTS layers are zinc rich. Black-Right-Pointing-Pointer CZTS layers show a high absorption coefficient and a band gap of 1.6 eV.

  12. Magnetic field dependence of the superconducting proximity effect in a two atomic layer thin metallic film

    Energy Technology Data Exchange (ETDEWEB)

    Caminale, Michael; Leon Vanegas, Augusto A.; Stepniak, Agnieszka; Oka, Hirofumi; Fischer, Jeison A.; Sander, Dirk; Kirschner, Juergen [Max-Planck-Institut fuer Mikrostrukturphysik, Halle (Germany)

    2015-07-01

    The intriguing possibility to induce superconductivity in a metal, in direct contact with a superconductor, is under renewed interest for applications and for fundamental aspects. The underlying phenomenon is commonly known as proximity effect. In this work we exploit the high spatial resolution of scanning tunneling spectroscopy at sub-K temperatures and in magnetic fields. We probe the differential conductance along a line from a superconducting 9 ML high Pb nanoisland into the surrounding two layer thin Pb/Ag wetting layer on a Si(111) substrate. A gap in the differential conductance indicates superconductivity of the Pb island. We observe an induced gap in the wetting layer, which decays with increasing distance from the Pb island. This proximity length is 21 nm at 0.38 K and 0 T. We find a non-trivial dependence of the proximity length on magnetic field. Surprisingly, we find that the magnetic field does not affect the induced superconductivity up to 0.3 T. However, larger fields of 0.6 T suppress superconductivity in the wetting layer, where the Pb island still remains superconducting. We discuss the unexpected robustness of induced superconductivity in view of the high electronic diffusivity in the metallic wetting layer.

  13. Suppression of sublinearity of light–current curve in 850 nm quantum well laser with asymmetric barrier layers

    DEFF Research Database (Denmark)

    Zubov, F.I.; Maximov, M.V.; Shernyakov, Yu.M.

    2015-01-01

    of the LCC at high current densities. As a result, the maximum lasing power of 9.2 W, being limited by catastrophic optical mirror damage, is achieved at a considerably lower operating current in the laser with ABLs as compared to the reference laser (12.5 against 20.2 A). The ABL effect is associated......An AlGaAs/GaAs quantum well (QW) laser is fabricated with GaInP and AlGaInAs asymmetric barrier layers (ABLs) and its light–current characteristic (LCC) is compared with that of a reference conventional QW laser without ABLs. It was found that the use of the ABLs suppresses the sublinearity...

  14. Origin of interfacial perpendicular magnetic anisotropy in MgO/CoFe/metallic capping layer structures.

    Science.gov (United States)

    Peng, Shouzhong; Wang, Mengxing; Yang, Hongxin; Zeng, Lang; Nan, Jiang; Zhou, Jiaqi; Zhang, Youguang; Hallal, Ali; Chshiev, Mairbek; Wang, Kang L; Zhang, Qianfan; Zhao, Weisheng

    2015-12-11

    Spin-transfer-torque magnetic random access memory (STT-MRAM) attracts extensive attentions due to its non-volatility, high density and low power consumption. The core device in STT-MRAM is CoFeB/MgO-based magnetic tunnel junction (MTJ), which possesses a high tunnel magnetoresistance ratio as well as a large value of perpendicular magnetic anisotropy (PMA). It has been experimentally proven that a capping layer coating on CoFeB layer is essential to obtain a strong PMA. However, the physical mechanism of such effect remains unclear. In this paper, we investigate the origin of the PMA in MgO/CoFe/metallic capping layer structures by using a first-principles computation scheme. The trend of PMA variation with different capping materials agrees well with experimental results. We find that interfacial PMA in the three-layer structures comes from both the MgO/CoFe and CoFe/capping layer interfaces, which can be analyzed separately. Furthermore, the PMAs in the CoFe/capping layer interfaces are analyzed through resolving the magnetic anisotropy energy by layer and orbital. The variation of PMA with different capping materials is attributed to the different hybridizations of both d and p orbitals via spin-orbit coupling. This work can significantly benefit the research and development of nanoscale STT-MRAM.

  15. Origin of interfacial perpendicular magnetic anisotropy in MgO/CoFe/metallic capping layer structures

    Science.gov (United States)

    Peng, Shouzhong; Wang, Mengxing; Yang, Hongxin; Zeng, Lang; Nan, Jiang; Zhou, Jiaqi; Zhang, Youguang; Hallal, Ali; Chshiev, Mairbek; Wang, Kang L.; Zhang, Qianfan; Zhao, Weisheng

    2015-12-01

    Spin-transfer-torque magnetic random access memory (STT-MRAM) attracts extensive attentions due to its non-volatility, high density and low power consumption. The core device in STT-MRAM is CoFeB/MgO-based magnetic tunnel junction (MTJ), which possesses a high tunnel magnetoresistance ratio as well as a large value of perpendicular magnetic anisotropy (PMA). It has been experimentally proven that a capping layer coating on CoFeB layer is essential to obtain a strong PMA. However, the physical mechanism of such effect remains unclear. In this paper, we investigate the origin of the PMA in MgO/CoFe/metallic capping layer structures by using a first-principles computation scheme. The trend of PMA variation with different capping materials agrees well with experimental results. We find that interfacial PMA in the three-layer structures comes from both the MgO/CoFe and CoFe/capping layer interfaces, which can be analyzed separately. Furthermore, the PMAs in the CoFe/capping layer interfaces are analyzed through resolving the magnetic anisotropy energy by layer and orbital. The variation of PMA with different capping materials is attributed to the different hybridizations of both d and p orbitals via spin-orbit coupling. This work can significantly benefit the research and development of nanoscale STT-MRAM.

  16. Production of Quasicomposite Surface Layer of a Metal Material by Shock Wave Strain Hardening

    Directory of Open Access Journals (Sweden)

    A.V. Kirichek

    2014-07-01

    Full Text Available Quite often in order to improve the performance of a product it is necessary to form a strengthened structure that will be extremely hard and have good plasticity at the same time. One way to meet this challenge is to apply shock wave mechanical hardening to produce micro- or nanocrystalline heterogeneous structures in homogeneous metals or alloys. A peculiar feature of such structure is its layer-by-layer formation with smooth transition between hard and plastic areas, which improves the performance of the strengthened item significantly

  17. Synthesis and Characterization of Layered Double Hydroxides Containing Optically Active Transition Metal Ion

    Science.gov (United States)

    Tyagi, S. B.; Kharkwal, Aneeta; Nitu; Kharkwal, Mamta; Sharma, Raghunandan

    2017-01-01

    The acetate intercalated layered double hydroxides of Zn and Mn, have been synthesized by chimie douce method. The materials were characterized by XRD, TGA, CHN, IR, XPS, SEM-EDX and UV-visible spectroscopy. The photoluminescence properties was also studied. The optical properties of layered hydroxides are active transition metal ion dependent, particularly d1-10 system plays an important role. Simultaneously the role of host - guest orientation has been considered the basis of photoluminescence. Acetate ion can be exchanged with iodide and sulphate ions. The decomposed product resulted the pure phase Mn doped zinc oxide are also reported.

  18. Enhanced Magnetoelectric Coupling in Layered Structure of Piezoelectric Bimorph and Metallic Alloy

    Science.gov (United States)

    Petrov, V. M.; Bichurin, M. I.; Lavrentyeva, K. V.; Leontiev, V. S.

    2016-08-01

    We have investigated the enhanced magnetoelectric (ME) coupling in a layered structure of piezoelectric bimorph and magnetostrictive metallic alloy. The observed ME coefficient in the piezoelectric bimorph-based structure was found to be two times higher than in the traditional piezoelectric/magnetostrictive bilayer. The observed enhancement in ME coupling strength is related to equal signs of induced voltage in both lead zirconate titanate layers with opposite poling directions due to the flexural deformations. The piezoelectric bimorph-based structure has promising potential for sensor and technological applications.

  19. Metal Surface Modification for Obtaining Nano- and Sub-Nanostructured Protective Layers

    Science.gov (United States)

    Ledovskykh, Volodymyr; Vyshnevska, Yuliya; Brazhnyk, Igor; Levchenko, Sergiy

    2017-03-01

    Regularities of the phase protective layer formation in multicomponent systems involving inhibitors with different mechanism of protective action have been investigated. It was shown that optimization of the composition of the inhibition mixture allows to obtain higher protective efficiency owing to improved microstructure of the phase layer. It was found that mechanism of the film formation in the presence of NaNO2-PHMG is due to deposition of slightly soluble PHMG-Fe complexes on the metal surface. On the basis of the proposed mechanism, the advanced surface engineering methods for obtaining nanoscaled and sub-nanostructured functional coatings may be developed.

  20. Schottky barrier detectors on 4H-SiC n-type epitaxial layer for alpha particles

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhuri, S.K.; Krishna, R.M.; Zavalla, K.J. [Department of Electrical Engineering, University of South Carolina, Columbia, SC 29208 (United States); Mandal, K.C., E-mail: mandalk@cec.sc.edu [Department of Electrical Engineering, University of South Carolina, Columbia, SC 29208 (United States)

    2013-02-11

    Schottky barrier detectors have been fabricated on 50 μm n-type 4H-SiC epitaxial layers grown on 360 μm SiC substrates by depositing ∼10 nm nickel contact. Current–voltage (I–V) and capacitance–voltage (C–V) measurements were carried out to investigate the Schottky barrier properties. The detectors were evaluated for alpha particle detection using a {sup 241}Am alpha source. An energy resolution of ∼2.7% was obtained with a reverse bias of 100 V for 5.48 MeV alpha particles. The measured charge collection efficiency (CCE) was seen to vary as a function of bias voltage following a minority carrier diffusion model. Using this model, a diffusion length of∼3.5 μm for holes was numerically calculated from the CCE vs. bias voltage plot. Rise-time measurements of digitally recorded charge pulses for the 5.48 MeV alpha particles showed a presence of two sets of events having different rise-times at a higher bias of 200 V. A biparametric correlation scheme was successfully implemented for the first time to visualize the correlated pulse-height distribution of the events with different rise-times. Using the rise-time measurements and the biparametric plots, the observed variation of energy resolution with applied bias was explained.

  1. Nanometer-thick amorphous-SnO2 layer as an oxygen barrier coated on a transparent AZO electrode

    Science.gov (United States)

    Lee, Hee Sang; Woo, Seong Ihl

    2016-07-01

    It is necessary for transparent conducting electrodes used in dye-sensitized or perovskite solar cells to have high thermal stability which is required when TiO2 is coated on the electrode. AZO films with their low-cost and good TCO properties are unfortunately unstable above 300 °C in air because of adsorbed oxygen. In this paper, the thermal stability of AZO films is enhanced by depositing an oxygen barrier on AZO films to block the oxygen. As the barrier material, SnO2 is used due to its high heat stability, electrical conductivity, and transmittance. Moreover, when the SnO2 is grown as amorphous phase, the protective effect become greater than the crystalline phase. The thermal stability of the amorphous-SnO2/AZO films varies depending on the thickness of the amorphous SnO2 layer. Because of the outstanding oxygen blocking properties of amorphous SnO2, its optimal thickness is very thin and it results in only a slight decrease in transmittance. The sheet resistance of the amorphous-SnO2/AZO film is 5.4 Ω sq-1 after heat treatment at 500 °C for 30 min in air and the average transmittance in the visible region is 83.4%. The results show that the amorphous-SnO2/AZO films have thermal stability with excellent electrical and optical properties. [Figure not available: see fulltext.

  2. A metal-semiconductor-metal detector based on ZnO nanowires grown on a graphene layer

    Science.gov (United States)

    Xu, Qiang; Cheng, Qijin; Zhong, Jinxiang; Cai, Weiwei; Zhang, Zifeng; Wu, Zhengyun; Zhang, Fengyan

    2014-02-01

    High quality ZnO nanowires (NWs) were grown on a graphene layer by a hydrothermal method. The ZnO NWs revealed higher uniform surface morphology and better structural properties than ZnO NWs grown on SiO2/Si substrate. A low dark current metal-semiconductor-metal photodetector based on ZnO NWs with Au Schottky contact has also been fabricated. The photodetector displays a low dark current of 1.53 nA at 1 V bias and a large UV-to-visible rejection ratio (up to four orders), which are significantly improved compared to conventional ZnO NW photodetectors. The improvement in UV detection performance is attributed to the existence of a surface plasmon at the interface of the ZnO and the graphene.

  3. A metal-semiconductor-metal detector based on ZnO nanowires grown on a graphene layer.

    Science.gov (United States)

    Xu, Qiang; Cheng, Qijin; Zhong, Jinxiang; Cai, Weiwei; Zhang, Zifeng; Wu, Zhengyun; Zhang, Fengyan

    2014-02-07

    High quality ZnO nanowires (NWs) were grown on a graphene layer by a hydrothermal method. The ZnO NWs revealed higher uniform surface morphology and better structural properties than ZnO NWs grown on SiO2/Si substrate. A low dark current metal-semiconductor-metal photodetector based on ZnO NWs with Au Schottky contact has also been fabricated. The photodetector displays a low dark current of 1.53 nA at 1 V bias and a large UV-to-visible rejection ratio (up to four orders), which are significantly improved compared to conventional ZnO NW photodetectors. The improvement in UV detection performance is attributed to the existence of a surface plasmon at the interface of the ZnO and the graphene.

  4. Electronic properties of GaSe, InSe, GaS and GaTe layered semiconductors: charge neutrality level and interface barrier heights

    Science.gov (United States)

    Brudnyi, V. N.; Sarkisov, S. Yu; Kosobutsky, A. V.

    2015-11-01

    Density functional theory calculations have been applied to study the structural and electronic properties of layered ɛ-GaSe, γ-InSe, β-GaS and GaTe compounds. The optimized lattice parameters have been obtained using vdW-DF2-C09 exchange-correlation functional, which is able to describe dispersion forces and produces interlayer distances in close agreement with experiments. Based on the calculated electronic band structures, the energy position of the charge neutrality level (CNL) in the III-VI semiconductors has been estimated for the first time. The room-temperature values of CNL are found to be 0.80 eV, 1.02 eV, 0.72 eV and 0.77 eV for ɛ-GaSe, β-GaS, GaTe and γ-InSe, respectively. The persistent p-type conductivity of the intentionally undoped ɛ-GaSe, β-GaS and GaTe and n-type conductivity of γ-InSe crystals are discussed and explained using the concept of CNL. We also estimated the barrier heights for a number of metal/semiconductor and semiconductor/semiconductor interfaces assuming partial Fermi level pinning at the CNL. A reasonable agreement between our calculations and the available experimental data has been obtained.

  5. SEMICONDUCTOR DEVICES: Analytical charge control model for AlGaN/GaN MIS-HFETs including an undepleted barrier layer

    Science.gov (United States)

    Shenghui, Lu; Jiangfeng, Du; Qian, Luo; Qi, Yu; Wei, Zhou; Jianxin, Xia; Mohua, Yang

    2010-09-01

    An analytical charge control model considering the insulator/AlGaN interface charge and undepleted Al-GaN barrier layer is presented for AlGaN/GaN metal-insulator-semiconductor heterostructure field effect transistors (MIS-HFETs) over the entire operation range of gate voltage. The whole process of charge control is analyzed in detail and partitioned into four regions: I—full depletion, II—partial depletion, III—neutral region and IV—electron accumulation at the insulator/AlGaN interface. The results show that two-dimensional electron gas (2DEG) saturates at the boundary of region II/III and the gate voltage should not exceed the 2DEG saturation voltage in order to keep the channel in control. In addition, the span of region II accounts for about 50% of the range of gate voltage before 2DEG saturates. The good agreement of the calculated transfer characteristic with the measured data confirms the validity of the proposed model.

  6. Enhanced rectifying response from metal-insulator-insulator-metal junctions

    Science.gov (United States)

    Maraghechi, P.; Foroughi-Abari, A.; Cadien, K.; Elezzabi, A. Y.

    2011-12-01

    We present on a metal-insulator-insulator-metal quantum electronic tunneling devices suitable for high speed rectifiers. Through the introduction of double oxide layer between similar metallic electrodes, a cascaded potential barrier is formed which alters the electron tunneling mechanism at forward versus the reverse bias. The cascaded potential barrier engineering manifests itself in both a highly nonlinear and asymmetric I-V junction characteristic. It is envisioned that high speed rectifiers and mixers having extraordinary nonlinearity can be realized through the incorporation of the cascaded potential barrier architecture and dissimilar metallic electrodes.

  7. Anion exchange kinetics of nanodimensional layered metal hydroxides: use of isoconversional analysis.

    Science.gov (United States)

    Majoni, Stephen; Hossenlopp, Jeanne M

    2010-12-16

    Anion exchange reactions of nanodimensional layered metal hydroxide compounds are utilized to create materials with targeted physical and chemical properties and also as a means for controlled release of intercalated anions. The kinetics of this important class of reaction are generally characterized by model-based approaches. In this work, a different approach based on isothermal, isoconversional analysis was utilized to determine effective activation energies with respect to extent of reaction. Two different layered metal hydroxide materials were chosen for reaction with chloride anions, using a temperature range of 30-60 °C. The concentrations of anions released into solution and the changes in polycrystalline solid phases were evaluated using model-based (Avrami-Erofe'ev nucleation-growth model) and model-free (integral isoconversional) methods. The results demonstrate the utility of the isoconversional approach for identifying when fitting to a single model is not appropriate, particularly for characterizing the temperature dependence of the reaction kinetics.

  8. Structure change, layer sliding, and metallization in high-pressure MoS2

    Science.gov (United States)

    Tosatti, Erio; Hromadova, Liliana; Martonak, Roman

    2013-03-01

    Based on ab initio calculations and metadynamics simulations, we predict that 2H-MoS2, a layered insulator, will metallize under pressures in excess of 20-30 GPa. In the same pressure range, simulations and enthalpy optimization predict a structural transition. Reminiscent of this material's frictional properties, free mutual sliding of layers takes place at this transition, where the original 2Hc stacking changes to a 2Ha stacking typical of 2H-NbSe2, a transformation which explains for the first time previously mysterious X-ray diffraction data. Phonon and electron phonon calculations suggest that metallic pristine MoS2 will require ultrahigh pressures in order to develop superconductivity. Supported by EU-Japan Project LEMSUPER, by a SNF Sinergia Project, and by the Slovak Research and Development Agency

  9. Growth of micrometric oxide layers for the study of metallic surfaces decontamination by laser

    Science.gov (United States)

    Carvalho, Luisa; Pacquentin, Wilfried; Tabarant, Michel; Maskrot, Hicham; Semerok, Alexandre

    2017-09-01

    The nuclear industry produces a wide range of radioactive waste in term of level of hazard, contaminants and material. For metallic equipment like steam generators, the radioactivity is mainly located in the oxide surface. In order to study and develop techniques for dismantling and for decontamination in a safe way, it is important to have access to oxide layers with a representative distribution of non-radioactive contaminants. We propose a method of formation of oxide layer on stainless steel 304L with europium (Eu) as contaminant marker. In this method, an Eu-solution is sprayed on the stainless steel samples. The specimen are firstly treated with a pulsed nanosecond laser and secondly the steel samples are exposed to a 600°C furnace for various durations in order to grow an oxide layer. The oxide structure and in-depth distribution of Eu in the oxide layer are analysed by scanning electron microscopy coupled with energy dispersive X-ray microanalyzer, and by glow discharge optical emission or mass spectrometry. The oxide layers were grown to thicknesses in the range of 200 nm to 4.5 μm regarding to the laser treatment parameters and the heating duration. These contaminated oxides have a `duplex structure' with a mean weight percentage of 0.5% of europium in the volume of the oxide layer. It appears that europium implementation prevents the oxide growth by furnace but has no impact on laser heating. These oxide layers are used to study the decontamination of metallic surfaces such as stainless steel 304L using a nanosecond pulsed laser.

  10. Enhancing rectification of a nano-swimmer system by multi-layered asymmetric barriers.

    Science.gov (United States)

    Chen, Yen-Fu; Xiao, Song; Chen, Hsuan-Yi; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2015-10-21

    The rectification of nano-swimmers in two chambers separated by a strip of funnel gates is explored by dissipative particle dynamics simulations. According to the trajectories of active colloids across the funnel zone, two rectification mechanisms are identified: geometry-assisted diffusion and trap-hindered diffusion. In general, geometry-assisted diffusion dominates at a small active force (Fa) and run time (τ) while trap-hindered diffusion governs at a large Fa and τ. The rectification ratio is affected by the funnel shape and various geometries are considered: open/closed triangular, circular and rectangular funnels. The rectification ratio of open funnels is always greater than that of closed funnels. Moreover, the open circular funnel has the best performance while the triangular one has the worst. Rectification can be enhanced as the number of funnel layers is increased. It is found that the rectification ratio of self-propelled colloids can be dramatically augmented by triple-layered funnels to be as high as 30. Our simulation study offers an efficient approach for rectification enhancement.

  11. Synthesis, characterization and application of two-dimensional layered metal hydroxides for environmental remediation purposes

    Science.gov (United States)

    Machingauta, Cleopas

    Two-dimensional layered nano composites, which include layered double hydroxides (LDHs), hydroxy double salts (HDSs) and layered hydroxide salts (LHSs) are able to intercalate different molecular species within their gallery space. These materials have a tunable structural composition which has made them applicable as fire retardants, adsorbents, catalysts, catalyst support materials, and ion exchangers. Thermal treatment of these materials results in destruction of the layers and formation of mixed metal oxides (MMOs) and spinels. MMOs have the ability to adsorb anions from solution and may also regenerate layered structures through a phenomenon known as memory effect. Zinc-nickel hydroxy nitrate was used for the uptake of a series of halogenated acetates (HAs). HAs are pollutants introduced into water systems as by-products of water chlorination and pesticide degradation; their sequestration from water is thus crucial. Optimization of layered materials for controlled uptake requires an understanding of their ion-exchange kinetics and thermodynamics. Exchange kinetics of these anions was monitored using ex-situ PXRD, UV-vis, HPLC and FTIR. It was revealed that exchange rates and uptake efficiencies are related to electronic spatial extents and the charge on carboxyl-oxygen atoms. In addition, acetate and nitrate-based HDSs were used to explore how altering the hydroxide layer affects uptake of acetate/nitrate ions. Changing the metal identities affects the interaction of the anions with the layers. From FTIR, we observed that nitrates coordinate in a D3h and Cs/C 2v symmetry; the nitrates in D3h symmetry were easily exchangeable. Interlayer hydrogen bonding was also revealed to be dependent on metal identity. Substituting divalent cations with trivalent cations produces materials with a higher charge density than HDSs and LHSs. A comparison of the uptake efficiency of zinc-aluminum, zinc-gallium and zinc-nickel hydroxy nitrates was performed using trichloroacetic

  12. Antibacterial and bioactive calcium titanate layers formed on Ti metal and its alloys.

    Science.gov (United States)

    Kizuki, Takashi; Matsushita, Tomiharu; Kokubo, Tadashi

    2014-07-01

    An antibacterial and bioactive titanium (Ti)-based material was developed for use as a bone substitute under load-bearing conditions. As previously reported, Ti metal was successively subjected to NaOH, CaCl2, heat, and water treatments to form a calcium-deficient calcium titanate layer on its surface. When placed in a simulated body fluid (SBF), this bioactive Ti formed an apatite layer on its surface and tightly bonded to bones in the body. To address concerns regarding deep infection during orthopedic surgery, Ag(+) ions were incorporated on the surface of this bioactive Ti metal to impart antibacterial properties. Ti metal was first soaked in a 5 M NaOH solution to form a 1 μm-thick sodium hydrogen titanate layer on the surface and then in a 100 mM CaCl2 solution to form a calcium hydrogen titanate layer via replacement of the Na(+) ions with Ca(2+) ions. The Ti material was subsequently heated at 600 °C for 1 h to transform the calcium hydrogen titanate into calcium titanate. This heat-treated titanium metal was then soaked in 0.01-10 mM AgNO3 solutions at 80 °C for 24 h. As a result, 0.1-0.82 at.% Ag(+) ions and a small amount of H3O(+) ions were incorporated into the surface calcium titanate layers. The resultant products formed apatite on their surface in an SBF, released 0.35-3.24 ppm Ag(+) ion into the fetal bovine serum within 24 h, and exhibited a strong antibacterial effect against Staphylococcus aureus. These results suggest that the present Ti metals should exhibit strong antibacterial properties in the living body in addition to tightly bonding to the surrounding bone through the apatite layer that forms on their surfaces in the body.

  13. Thin-layer chromatographie separation of alkaline earth metals on diethylaminoethyl cellulose.

    Science.gov (United States)

    Ishida, K

    1969-12-01

    Thin-layer Chromatographic behaviour of magnesium, calcium, strontium and barium on diethylaminoethyl cellulose has been investigated in methanol-nitric acid mixtures. R(f) values are in the order magnesium > calcium > strontium > barium. The differences in R(f) values are large enough to allow good separations of the four metal ions from each other. The best separation is obtained by the ascending technique with methanol-8M nitric acid (20:1, v v ).

  14. Melt layer erosion of metallic armour targets during off-normal events in tokamaks

    Science.gov (United States)

    Bazylev, B.; Wuerz, H.

    2002-12-01

    Melt layer erosion by melt motion is the dominating erosion mechanism for metallic armours under high heat loads. A 1-D fluid dynamics simulation model for calculation of melt motion was developed and validated against experimental results for tungsten from the e-beam facility JEBIS and beryllium from the e-beam facility JUDITH. The driving force in each case is the gradient of the surface tension. Due to the high velocity which develops in the Be melt considerable droplet splashing occurs.

  15. Ag/Ni Metallization Bilayer: A Functional Layer for Highly Efficient Polycrystalline SnSe Thermoelectric Modules

    Science.gov (United States)

    Park, Sang Hyun; Jin, Younghwan; Ahn, Kyunghan; Chung, In; Yoo, Chung-Yul

    2017-02-01

    The structural and electrical characteristics of Ag/Ni bilayer metallization on polycrystalline thermoelectric SnSe were investigated. Two difficulties with thermoelectric SnSe metallization were identified for Ag and Ni single layers: Sn diffusion into the Ag metallization layer and unexpected cracks in the Ni metallization layer. The proposed Ag/Ni bilayer was prepared by hot-pressing, demonstrating successful metallization on the SnSe surface without interfacial cracks or elemental penetration into the metallization layer. Structural analysis revealed that the Ni layer reacts with SnSe, forming several crystalline phases during metallization that are beneficial for reducing contact resistance. Detailed investigation of the Ni/SnSe interface layer confirms columnar Ni-Sn intermetallic phases [(Ni3Sn and Ni3Sn2) and Ni5.63SnSe2] that suppress Sn diffusion into the Ag layer. Electrical specific-contact resistivity (5.32 × 10-4 Ω cm2) of the Ag/Ni bilayer requires further modification for development of high-efficiency polycrystalline SnSe thermoelectric modules.

  16. Prediction of transmittance spectra for transparent composite electrodes with ultra-thin metal layers

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Zhao; Alford, T. L., E-mail: TA@asu.edu [School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, Arizona 85287 (United States); Khorasani, Arash Elhami [ON Semiconductor Corp., Phoenix, Arizona 85005 (United States); Theodore, N. D. [CHD-Fab, Freescale Semiconductor Inc., Tempe, Arizona 85224 (United States); Dhar, A. [Intel Corp., 2501 NW 229th Ave, Hillsboro, Oregon 97124 (United States)

    2015-11-28

    Recent interest in indium-free transparent composite-electrodes (TCEs) has motivated theoretical and experimental efforts to better understand and enhance their electrical and optical properties. Various tools have been developed to calculate the optical transmittance of multilayer thin-film structures based on the transfer-matrix method. However, the factors that affect the accuracy of these calculations have not been investigated very much. In this study, two sets of TCEs, TiO{sub 2}/Au/TiO{sub 2} and TiO{sub 2}/Ag/TiO{sub 2}, were fabricated to study the factors that affect the accuracy of transmittance predictions. We found that the predicted transmittance can deviate significantly from measured transmittance for TCEs that have ultra-thin plasmonic metal layers. The ultrathin metal layer in the TCE is typically discontinuous. When light interacts with the metallic islands in this discontinuous layer, localized surface plasmons are generated. This causes extra light absorption, which then leads to the actual transmittance being lower than the predicted transmittance.

  17. Highly Enhanced TMR Ratio and Δ for Double MgO-based p-MTJ Spin-Valves with Top Co2Fe6B2 Free Layer by Nanoscale-thick Iron Diffusion-barrier.

    Science.gov (United States)

    Lee, Seung-Eun; Baek, Jong-Ung; Park, Jea-Gun

    2017-09-19

    For double MgO-based p-MTJ spin-valves with a top Co2Fe6B2 free layer ex-situ annealed at 400 °C, the insertion of a nanoscale-thickness Fe diffusion barrier between the tungsten (W) capping layer and MgO capping layer improved the face-centered-cubic (f.c.c.) crystallinity of both the MgO capping layer and tunneling barrier by dramatically reducing diffusion of W atoms from the W capping layer into the MgO capping layer and tunneling barrier, thereby enhancing the TMR ratio and thermal stability (Δ). In particular, the TMR ratio was extremely sensitive to the thickness of the Fe barrier; it peaked (154%) at about 0.3 nm (the thickness of only two atomic Fe layers). The effect of the diffusion barrier originated from interface strain.

  18. Probing Critical Point Energies of Transition Metal Dichalcogenides: Surprising Indirect Gap of Single Layer WSe 2

    KAUST Repository

    Zhang, Chendong

    2015-09-21

    By using a comprehensive form of scanning tunneling spectroscopy, we have revealed detailed quasi-particle electronic structures in transition metal dichalcogenides, including the quasi-particle gaps, critical point energy locations, and their origins in the Brillouin zones. We show that single layer WSe surprisingly has an indirect quasi-particle gap with the conduction band minimum located at the Q-point (instead of K), albeit the two states are nearly degenerate. We have further observed rich quasi-particle electronic structures of transition metal dichalcogenides as a function of atomic structures and spin-orbit couplings. Such a local probe for detailed electronic structures in conduction and valence bands will be ideal to investigate how electronic structures of transition metal dichalcogenides are influenced by variations of local environment.

  19. Atomic layer deposition by reaction of molecular oxygen with tetrakisdimethylamido-metal precursors

    Energy Technology Data Exchange (ETDEWEB)

    Provine, J, E-mail: jprovine@stanford.edu; Schindler, Peter; Torgersen, Jan; Kim, Hyo Jin [Department of Mechanical Engineering, Stanford University, Stanford, California 94305 (United States); Karnthaler, Hans-Peter [Physics of Nanostructured Materials, University of Vienna, 1090 Vienna (Austria); Prinz, Fritz B. [Department of Mechanical Engineering, Stanford University, Stanford, California 94305 and Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States)

    2016-01-15

    Tetrakisdimethylamido (TDMA) based precursors are commonly used to deposit metal oxides such as TiO{sub 2}, ZrO{sub 2}, and HfO{sub 2} by means of chemical vapor deposition and atomic layer deposition (ALD). Both thermal and plasma enhanced ALD (PEALD) have been demonstrated with TDMA-metal precursors. While the reactions of TDMA-type precursors with water and oxygen plasma have been studied in the past, their reactivity with pure O{sub 2} has been overlooked. This paper reports on experimental evaluation of the reaction of molecular oxygen (O{sub 2}) and several metal organic precursors based on TDMA ligands. The effect of O{sub 2} exposure duration and substrate temperature on deposition and film morphology is evaluated and compared to thermal reactions with H{sub 2}O and PEALD with O{sub 2} plasma.

  20. Probing Critical Point Energies of Transition Metal Dichalcogenides: Surprising Indirect Gap of Single Layer WSe2.

    Science.gov (United States)

    Zhang, Chendong; Chen, Yuxuan; Johnson, Amber; Li, Ming-Yang; Li, Lain-Jong; Mende, Patrick C; Feenstra, Randall M; Shih, Chih-Kang

    2015-10-14

    By using a comprehensive form of scanning tunneling spectroscopy, we have revealed detailed quasi-particle electronic structures in transition metal dichalcogenides, including the quasi-particle gaps, critical point energy locations, and their origins in the Brillouin zones. We show that single layer WSe2 surprisingly has an indirect quasi-particle gap with the conduction band minimum located at the Q-point (instead of K), albeit the two states are nearly degenerate. We have further observed rich quasi-particle electronic structures of transition metal dichalcogenides as a function of atomic structures and spin-orbit couplings. Such a local probe for detailed electronic structures in conduction and valence bands will be ideal to investigate how electronic structures of transition metal dichalcogenides are influenced by variations of local environment.

  1. A further comparison of graphene and thin metal layers for plasmonics.

    Science.gov (United States)

    He, Xiaoyong; Gao, Pingqi; Shi, Wangzhou

    2016-05-21

    Which one is much more suitable for plasmonic materials, graphene or metal? To address this problem well, the plasmonic properties of thin metal sheets at different thicknesses have been investigated and compared with a graphene layer. As demonstration examples, the propagation properties of insulator-metal-insulator and metamaterials (MMs) structures are also shown. The results manifest that the plasmonic properties of the graphene layer are comparable to that of thin metal sheets with the thickness of tens of nanometers. For the graphene MMs structure, by using the periodic stack structure in the active region, the resonant transmission strength significantly improves. At the optimum period number, 3-5 periods of graphene/SiO2, the graphene MMs structure manifests good frequency and amplitude tunable properties simultaneously, and the resonant strength is also strong with large values of the Q-factor. Therefore, graphene is a good tunable plasmonic material. The results are very helpful to develop novel graphene plasmonic devices, such as modulators, antenna and filters.

  2. A further comparison of graphene and thin metal layers for plasmonics

    Science.gov (United States)

    He, Xiaoyong; Gao, Pingqi; Shi, Wangzhou

    2016-05-01

    Which one is much more suitable for plasmonic materials, graphene or metal? To address this problem well, the plasmonic properties of thin metal sheets at different thicknesses have been investigated and compared with a graphene layer. As demonstration examples, the propagation properties of insulator-metal-insulator and metamaterials (MMs) structures are also shown. The results manifest that the plasmonic properties of the graphene layer are comparable to that of thin metal sheets with the thickness of tens of nanometers. For the graphene MMs structure, by using the periodic stack structure in the active region, the resonant transmission strength significantly improves. At the optimum period number, 3-5 periods of graphene/SiO2, the graphene MMs structure manifests good frequency and amplitude tunable properties simultaneously, and the resonant strength is also strong with large values of the Q-factor. Therefore, graphene is a good tunable plasmonic material. The results are very helpful to develop novel graphene plasmonic devices, such as modulators, antenna and filters.

  3. Electrochemical impedance spectroscopy on in-situ analysis of oxide layer formation in liquid metal

    Energy Technology Data Exchange (ETDEWEB)

    Kondo, M., E-mail: kondo.masatoshi@tokai-u.jp [Department of Nuclear Engineering, School of Engineering, Tokai University, 4-1-1 Kitakaname, Hiratsuka-shi, Kanagawa 259-1292 (Japan); Suzuki, N.; Nakajima, Y. [Department of Nuclear Engineering, School of Engineering, Tokai University, 4-1-1 Kitakaname, Hiratsuka-shi, Kanagawa 259-1292 (Japan); Tanaka, T.; Muroga, T. [National Institute for Fusion Science, Toki, Gifu 502-5292 (Japan)

    2014-10-15

    Graphical abstract: Some test materials (i.e. Fe, Cr, Y and JLF-1 steel) were immersed to liquid metal lead (Pb) mainly at 773 K as the working electrode of electrochemical impedance spectroscopy (EIS). Some oxide layers formed on the electrodes in liquid Pb were analyzed by EIS. The impedance response was summarized as semicircular Nyquist plot, and the electrical properties and the thickness of the oxide layers were evaluated in non-destructive manner. Large impedance due to the formation of Y oxide formed in liquid Pb was detected by EIS, though impedance of Fe oxide and Cr oxide could not be detected due to their small electro resistance. The time constant of the oxide layers was evaluated from the impedance information, and this value identified the types of oxides. The change of the time constant with the immersion time indicated the change of the electrical properties determined by the chemical composition and the crystal structure. The thickness of the oxide layer estimated by EIS agreed well with that evaluated by metallurgical analysis. The growth of Y oxide layer in the liquid Pb was successfully detected by EIS in non-destructive manner. - Highlights: • The electrical properties and the thickness of lead oxide layer formed in liquid Pb were obtained by electrochemical impedance spectroscopy (EIS). • The Fe oxide, Cr oxide and Fe–Cr oxide formed on the electrodes in liquid Pb were not detected by EIS due to their small electrical resistance. • The formation and the growth of Y oxide formed in liquid Pb was detected by EIS. - Abstract: Some test materials (i.e. Fe, Cr, Y and JLF-1 steel) were immersed to liquid metal lead (Pb) mainly at 773 K as the working electrode of electrochemical impedance spectroscopy (EIS). Some oxide layers formed on the electrodes in liquid Pb were analyzed by EIS. The impedance response was summarized as Nyquist plot, and the electrical properties and the thickness of the oxide layers were evaluated in non

  4. A MIXED BOOLEAN AND DEPOSIT MODEL FOR THE MODELING OF METAL PIGMENTS IN PAINT LAYERS

    Directory of Open Access Journals (Sweden)

    Enguerrand Couka

    2015-06-01

    Full Text Available Pigments made of metal particles of around 10 µm or 20 µm produce sparkling effects in paints, due to the specular reflection that occurs at this scale. Overall, the optical aspect of paints depend on the density and distribution in space of the particles. In this work, we model the dispersion of metal particles of size up to 50 µm, visible to the eyes, in a paint layer. Making use of optical and scanning electron microscopy (SEM images, we estimate the dispersion of particles in terms of correlation functions. Particles tend to aggregate into clusters, as shown by the presence of oscillations in the correlation functions. Furthermore, the volume fraction of particles is non-uniform in space. It is highest in the middle of the layer and lowest near the surfaces of the layer. To model this microstructure, we explore two models. The first one is a deposit model where particles fall onto a surface. It is unable to reproduce the observed measurements. We then introduce a "stack" model where clusters are first modeled by a 2D Poisson point process, and a bi-directional deposit model is used to implant particles in each cluster. Good agreement is found with respect to SEM images in terms of correlation functions and density of particles along the layer height.

  5. Micro-EDXRF surface analyses of a bronze spear head: Lead content in metal and corrosion layers

    Energy Technology Data Exchange (ETDEWEB)

    Figueiredo, E. [Instituto Tecnologico e Nuclear, Estrada Nacional 10, 2686-953 Sacavem (Portugal); Departamento de Conservacao e Restauro, Faculdade de Ciencias e Tecnologia da Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Monte de Caparica (Portugal)], E-mail: elin@itn.pt; Valerio, P.; Araujo, M.F. [Instituto Tecnologico e Nuclear, Estrada Nacional 10, 2686-953 Sacavem (Portugal); Senna-Martinez, J.C. [Instituto de Arqueologia, Faculdade de Letras da Universidade de Lisboa, Cidade Universitaria, Campo Grande, 1600-214 Lisbon (Portugal)

    2007-09-21

    A bronze spear head from Central Portugal dated to Late Bronze Age has been analyzed by non-destructive micro-EDXRF in the metal surface and corrosion layers. The artifact had previously been analyzed using a conventional EDXRF spectrometer having a larger incident beam. The quantification of the micro-EDXRF analyses showed that lead content in corrosion layers can reach values up to four times higher than the content determined in the metal surface. Results obtained with the higher energy incident beam from the EDXRF equipment, although referring mainly to the corrosion layers, seem to suffer some influence from the surface composition of the metallic alloy.

  6. Residual Stress and Bonding Strength in the ElectricalSialon Ceramics Joint Made by Using the Brazing Metal Layer

    OpenAIRE

    Kimura, Mitsuhiko; Asari, Koichi; GOTO, Shoji; Aso, Setsuo

    2002-01-01

    Electrical Sialons which have some TiN contents were joined with Ag-Cu-Ti active brazing metal layer having a thickness from 30μm to 400μm at a temperature from 1113 K to 1213 K in a vacuum. Residual stress in the brazed joint specimens was not observed when the thickness of brazing metal layer was 30 μ m. However, the residual stress of 80 MPa was detected when the thickness of brazing metal layer increased up to 400μm. When the brazing temperature was 1113 K, four-point bending strengths of...

  7. Revealing extraordinary tensile plasticity in layered Ti-Al metal composite

    Science.gov (United States)

    Huang, M.; Fan, G. H.; Geng, L.; Cao, G. J.; Du, Y.; Wu, H.; Zhang, T. T.; Kang, H. J.; Wang, T. M.; Du, G. H.; Xie, H. L.

    2016-12-01

    Layered Ti-Al metal composite (LMC) fabricated by hot-pressing and hot-rolling process displays higher ductility than that of both components. In this paper, a combination of digital image correlation (DIC) and X-ray tomography revealed that strain delocalization and constrained crack distribution are the origin of extraordinary tensile ductility. Strain delocalization was derived from the transfer of strain partitioning between Ti and Al layer, which relieved effectively the strain localization of LMC. Furthermore, the extensive cracks of LMC were restricted in the interface due to constraint effect. Layered architecture constrained the distribution of cracks and significantly relieved the strain localization. Meanwhile, the transfer of strain partitioning and constrained crack distribution were believed to inhibit the strain localization of Ti and change the deformation mechanisms of Ti. Our finding enriches current understanding about simultaneously improving the strength and ductility by structural design.

  8. New Power Lateral Double Diffused Metal-Oxide-Semiconductor Transistor with a Folded Accumulation Layer

    Institute of Scientific and Technical Information of China (English)

    DUAN Bao-Xing; ZHANG Bo; LI Zhao-Ji

    2007-01-01

    A new lateral double diffused metal oxide semiconductor field effect transistor with a double-charge accumulation layer using a folded silicon substrate is proposed to improve the performance of the breakdown voltage and specific on-resistance. Three kinds of technologies, which are the additional electric field modulation effect, majority carrier accumulation and increasing the effective conduction area, are applied simultaneously by a semi-insulating polycrystalline silicon layer deposited over the top of thin oxide covering the drift region. It is indicated that by the simulator, the ideal silicon limits of the breakdown voltage and specific on-resistance have been broken due to the complete three-dimensional reduced surface field effect and the doubled majority carrier accumulation layer.

  9. Metallization of bacterial surface layer by cross-beam pulsed laser deposition

    Science.gov (United States)

    Pompe, Wolfgang; Mertig, Michael; Kirsch, Remo; Gorbunov, Andre A.; Sewing, Andreas; Engelhardt, Harald; Mensch, Axel

    1996-04-01

    We present first results on thin film metal deposition on the regular bacterial surface layer of Sporsarcina urea by pulsed laser deposition. To prevent structural damage of the biological specimen a recently developed cross beam technique is applied providing an effective filtering of the most energetic plasma particles. The deposited films are examined by low voltage scanning electron microscopy. The surface profile of the S-layer adsorbed onto mica substrate was investigated by atomic force microscopy. A lattice constant of 13.2 nm has been measured. The lattice parameters and the structural appearance of the protein layer is in reasonable agreement with the results of an electron microscopical 3D structural analysis.

  10. Transitions metal dichalcogenides: Growth, fermiology studies, and few-layered transport properties

    Science.gov (United States)

    Rhodes, Daniel

    Transition metal dichalcogenides (TMDs or TMDCs) have garnered much interest recently due to their weakly layered structures, allowing for mechanical exfoliation down to a single atomic layer. As such, it is pertinent to re-examine the bulk properties of these materials in order to completely understand and predict what is happening in the few-layered limit. A large majority of these systems were first investigated in the 1950s and 1960s. As such, many of the current growth methods rely on these reports, making new growth techniques for lowering defects of importance as well. In this thesis, both topics are taken into consideration and discussed, though the latter remains to be investigated in much more detail and should be the work of future research efforts. (Abstract shortened by ProQuest.).

  11. [XPS characterization of auto-reconditioning layer on worn metal surfaces].

    Science.gov (United States)

    Yang, He; Zhang, Zheng-ye; Li, Sheng-hua; Jin, Yuan-sheng

    2005-06-01

    An auto-reconditioner package for in situ reconditioning of worn surfaces of machinery parts under normal running was applied to diesel engines of DF locomotives. A reconditioning layer was generated on the cylinder bore after running a mileage of 300,000 km, and no wear was measured for the piston rings and cylinder bores. Evaluations with SEM, nanohardness tester and XPS indicated that the protective layer assumed a thickness of 8-10 microm, a nano-hardness twice as high as that of the cast iron substrate, and a main elemental composition of Fe, O and C corresponding to the existence of Fe3O4 and Fe3C. A possible formation mechanism of the protective layer was suggested based on the mechanochemical activation of metal surfaces and the catalytic activation of the auto-reconditioner molecules.

  12. Oxidative removal of implanted photoresists and barrier metals in semiconductor processing

    Science.gov (United States)

    Govindarajan, Rajkumar

    Chemical systems containing oxidants are widely used at various stages in semiconductor processing, particularly for wet cleaning and polishing applications. This dissertation presents a series of studies related to oxidative removal of materials in the Front-End-Of-Line (FEOL) and Chemical Mechanical Planarization (CMP) processes during IC fabrication. In the first part of this study, stripping of photoresists exposed to high dose of ions (1E16 As/cm2) was investigated in activated hydrogen peroxide systems. Stripping of photoresists (PR) exposed to high dose (>1E15/cm2) ion beams is one of the most challenging steps in FEOL processing. This is due to unreactive crust layer that forms on the resist surface during ion implantation. The use of hydrogen peroxide systems activated by metal ion or UV light, for disrupting crust formed on deep UV resist to enable complete removal of crust as well as underlying photoresist was investigated. A systematic evaluation of variables such as hydrogen peroxide and metal ion concentration, UV intensity, temperature and time was conducted and an optimal formulation capable of attacking the crust was developed. A two step process involving pretreatment with activated hydrogen peroxide solution, followed by treatment with sulfuric acid-hydrogen peroxide mixture (SPM) was developed for complete removal of crusted resist films. In the second part of this study, electrochemically enhanced abrasive removal of Ta/TaN films was investigated in solutions containing 2,5 dihydroxy benzene sulfonic acid (DBSA) and potassium iodate (KIO3). This method known as Electrically-assisted Chemical Mechanical Planarization (ECMP) is generating a lot of interest in IC manufacturing. Ta/TaN films were abraded at low pressures (tantalum and tantalum nitride removal rates of ˜170 A0/min and ˜200 A 0/min, respectively have been obtained at a current density of 1 mA/cm 2. The use of benzotriazole as a copper inhibitor was required to obtain Ta to Cu

  13. Design of Efficient Catalysts with Double Transition Metal Atoms on C2N Layer.

    Science.gov (United States)

    Li, Xiyu; Zhong, Wenhui; Cui, Peng; Li, Jun; Jiang, Jun

    2016-05-05

    Heterogeneous catalysis often involves molecular adsorptions to charged catalyst site and reactions triggered by catalyst charges. Here we use first-principles simulations to design oxygen reduction reaction (ORR) catalyst based on double transition metal (TM) atoms stably supported by 2D crystal C2N. It not only holds characters of low cost and high durability but also effectively accumulates surface polarization charges on TMs and later deliveries to adsorbed O2 molecule. The Co-Co, Ni-Ni, and Cu-Cu catalysts exhibit high adsorption energies and extremely low dissociation barriers for O2, as compared with their single-atom counterparts. Co-Co on C2N presents less than half the value of the reaction barrier of bulk Pt catalysts in the ORR rate-determining steps. These catalytic improvements are well explained by the dependences of charge polarization on various systems, which opens up a new strategy for optimizing TM catalytic performance with the least metal atoms on porous low-dimensional materials.

  14. Epitaxial wurtzite-MgZnO barrier based magnetic tunnel junctions deposited on a metallic ferromagnetic electrode

    Energy Technology Data Exchange (ETDEWEB)

    Belmoubarik, M., E-mail: bmm-dhr@ecei.tohoku.ac.jp; Al-Mahdawi, M.; Sato, H.; Nozaki, T.; Sahashi, M. [Department of Electronic Engineering, Tohoku University, Sendai 890-8579 (Japan)

    2015-06-22

    An epitaxial wurtzite (WZ) Mg{sub 0.23}Zn{sub 0.77}O barrier based magnetic tunnel junction (MTJ), with electrode-barrier structure of Co{sub 0.30}Pt{sub 0.70} (111)/Mg{sub 0.23}Zn{sub 0.77}O (0001)/Co (0001), was fabricated. The good crystallinity and tunneling properties were experimentally confirmed. Electrical and magnetic investigations demonstrated its high resistance-area product of 1.05 MΩ μm{sup 2}, a maximum tunneling magneto-resistance (TMR) of 35.5%, and the existence of localized states within the tunneling barrier producing TMR rapid decrease and oscillation when increasing the applied bias voltage. The TMR value almost vanished at 200 K, which was attributed to the induced moment and strong spin-orbit coupling in Pt atoms at the Co{sub 0.30}Pt{sub 0.70}/Mg{sub 0.23}Zn{sub 0.77}O interface. Owing to the ferroelectric behavior in WZ-MgZnO materials, the fabrication of WZ-MgZnO barrier based MTJs deposited on a metallic ferromagnetic electrode will open routes for electrically controllable non-volatile devices that are compatible with CMOS technology.

  15. The mucus layer is critical in protecting against ischemia-reperfusion-mediated gut injury and in the restitution of gut barrier function.

    Science.gov (United States)

    Qin, Xiaofa; Sheth, Sharvil U; Sharpe, Susan M; Dong, Wei; Lu, Qi; Xu, Dazhong; Deitch, Edwin A

    2011-03-01

    It is well documented that the gut injury plays a critical role in the development of systemic inflammation and distant organ injury in conditions associated with splanchnic ischemia. Consequently, understanding the mechanisms leading to gut injury is important. In this context, recent work suggests a protective role for the intestinal mucus layer and an injury-inducing role for luminal pancreatic proteases. Thus, we explored the role of the mucus layer in gut barrier function by observing how the removal of the mucus layer affects ischemia-reperfusion-mediated gut injury in rats as well as the potential role of luminal pancreatic proteases in the pathogenesis of gut injury. Ischemia was induced by the ligation of blood vessels to segments of the ileum for 45 min, followed by up to 3 h of reperfusion. The ileal segments were divided into five groups. These included a nonischemic control, ischemic segments exposed to saline, the mucolytic N-acetylcysteine (NAC), pancreatic proteases, or NAC + pancreatic proteases. Changes in gut barrier function were assessed by the permeation of fluorescein isothiocyanate dextran (molecular weight, 4,000 d) in ileal everted sacs. Gut injury was measured morphologically and by the luminal content of protein, DNA, and hemoglobin. The mucus layer was assessed functionally by measuring its hydrophobicity and morphologically. Gut barrier function was promptly and effectively reestablished during reperfusion, which was accompanied by the restoration of the mucus layer. In contrast, treatment of the gut with the mucolytic NAC for 10 min during ischemia resulted in a failure of mucus restitution and further increases in gut permeability and injury. The presence of digestive proteases by themselves did not exacerbate gut injury, but in combination with NAC, they caused an even greater increase in gut injury and permeability. These results suggest that the mucus layer not only serves as a barrier between the luminal contents and gut surface

  16. Design of multi-layered porous fibrous metals for optimal sound absorption in the low frequency range

    Directory of Open Access Journals (Sweden)

    Wenjiong Chen

    2016-01-01

    Full Text Available We present a design method for calculating and optimizing sound absorption coefficient of multi-layered porous fibrous metals (PFM in the low frequency range. PFM is simplified as an equivalent idealized sheet with all metallic fibers aligned in one direction and distributed in periodic hexagonal patterns. We use a phenomenological model in the literature to investigate the effects of pore geometrical parameters (fiber diameter and gap on sound absorption performance. The sound absorption coefficient of multi-layered PFMs is calculated using impedance translation theorem. To demonstrate the validity of the present model, we compare the predicted results with the experimental data. With the average sound absorption (low frequency range as the objective function and the fiber gaps as the design variables, an optimization method for multi-layered fibrous metals is proposed. A new fibrous layout with given porosity of multi-layered fibrous metals is suggested to achieve optimal low frequency sound absorption. The sound absorption coefficient of the optimal multi-layered fibrous metal is higher than the single-layered fibrous metal, and a significant effect of the fibrous material on sound absorption is found due to the surface porosity of the multi-layered fibrous.

  17. Thin films of copper oxide and copper grown by atomic layer deposition for applications in metallization systems of microelectronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Waechtler, Thomas

    2010-05-25

    Copper-based multi-level metallization systems in today's ultralarge-scale integrated electronic circuits require the fabrication of diffusion barriers and conductive seed layers for the electrochemical metal deposition. Such films of only several nanometers in thickness have to be deposited void-free and conformal in patterned dielectrics. The envisaged further reduction of the geometric dimensions of the interconnect system calls for coating techniques that circumvent the drawbacks of the well-established physical vapor deposition. The atomic layer deposition method (ALD) allows depositing films on the nanometer scale conformally both on three-dimensional objects as well as on large-area substrates. The present work therefore is concerned with the development of an ALD process to grow copper oxide films based on the metal-organic precursor bis(trin- butylphosphane)copper(I)acetylacetonate [({sup n}Bu{sub 3}P){sub 2}Cu(acac)]. This liquid, non-fluorinated {beta}-diketonate is brought to react with a mixture of water vapor and oxygen at temperatures from 100 to 160 C. Typical ALD-like growth behavior arises between 100 and 130 C, depending on the respective substrate used. On tantalum nitride and silicon dioxide substrates, smooth films and selfsaturating film growth, typical for ALD, are obtained. On ruthenium substrates, positive deposition results are obtained as well. However, a considerable intermixing of the ALD copper oxide with the underlying films takes place. Tantalum substrates lead to a fast self-decomposition of the copper precursor. As a consequence, isolated nuclei or larger particles are always obtained together with continuous films. The copper oxide films grown by ALD can be reduced to copper by vapor-phase processes. If formic acid is used as the reducing agent, these processes can already be carried out at similar temperatures as the ALD, so that agglomeration of the films is largely avoided. Also for an integration with subsequent

  18. A new RHQT Nb3Al superconducting wire with a Ta/Cu/Ta three-layer filament-barrier structure

    Science.gov (United States)

    Takeuchi, Takao; Tsuchiya, Kiyosumi; Nakagawa, Kazuhiko; Nimori, Shigeki; Banno, Nobuya; Iijima, Yasuo; Kikuchi, Akihiro; Nakamoto, Tatsushi

    2012-06-01

    To suppress the low-magnetic-field instability (flux jumps in low magnetic fields) of a rapid-heating, quenching and transformation (RHQT) processed Nb3Al superconductor, we had previously modified the cross-sectional design of an RHQT Nb3Al by adopting a Ta filament-barrier structure. Unlike Nb barriers, Ta barriers are not superconducting in magnetic fields at 4.2 K so that they electromagnetically decouple filaments. However, small flux jumps still occurred at 1.8 K, which is a typical operating temperature for the magnets used in high-energy particle accelerators. Furthermore, poor bonding at the Ta/Ta interface between neighboring Ta-coated jelly-roll (JR) filaments frequently caused precursor wires to break during drawing. To overcome these problems, we fabricated a new RHQT Nb3Al wire with a Ta/Cu/Ta three-layer filament-barrier structure for which an internal stabilization technique (Cu rods encased in Ta are dispersed in the wire cross section) was extended. Removing the Ta/Ta interface in the interfilamentary barrier (JR filament/Ta/Cu/Ta/JR filament) allowed precursor wires to be drawn without breaking. Furthermore, the Cu filament barrier electromagnetically decoupled filaments to suppress flux jumps at 1.8 K. The ductile Cu layer also improved the bending strain tolerance of RHQT Nb3Al.

  19. Adhesive mucous gel layer and mucus release as intestinal barrier in rats.

    Science.gov (United States)

    Iiboshi, Y; Nezu, R; Cui, L; Chen, K; Khan, J; Yoshida, H; Sando, K; Kamata, S; Takagi, Y; Okada, A

    1996-01-01

    Although it has been reported that total parenteral nutrition induces an increased intestinal permeability and a decreased mucous gel layer covering the intestinal epithelium, the role of mucous gel on intestinal permeability has not been well understood. We examined the in vivo effects of N-acetyl cysteine (NAC) as mucolytic agent and colchicine as suppressant of the mucus production on the intestinal transmission of fluorescein isothiocyanate dextran 70,000 (FITC-dextran). Rats were divided into four groups. In each group, FITC-dextran (750 mg/kg) with or without NAC (3000 mg/kg) was injected into the small intestinal lumen 3 hours after intraperitoneal injection of saline or colchicine (Col, 10 mg/kg). Thirty minutes after injection of FITC-dextran, blood samples were taken from portal vein to analyze plasma fluorescein concentration by fluorescence spectrometry. Samples of small intestine were sectioned in a cryostat for fluorescence microscopy, and the identical sections were stained by periodic acid-Schiff reaction. Plasma FITC-dextran level in NAC group was higher than that in control group (p NAC group was higher than that in Col group (p NAC group was higher than that in NAC group (p NAC and Col + NAC groups. FITC-dextran and mucous gel showed complementary distribution in all rats. The villous interstitial edema was recognized in NAC group and the villi were disrupted in Col + NAC group. These results suggest that intestinal permeability is possibly affected not only by the mucous gel covering the intestinal epithelium but also by mucus release from goblet cells of the small intestine.

  20. Vapor phase hydrogenation of furfural over nickel mixed metal oxide catalysts derived from layered double hydroxides

    Energy Technology Data Exchange (ETDEWEB)

    Sulmonetti, Taylor P.; Pang, Simon H.; Claure, Micaela Taborga; Lee, Sungsik; Cullen, David A.; Agrawal, Pradeep K.; Jones, Christopher W.

    2016-05-01

    The hydrogenation of furfural is investigated over various reduced nickel mixed metal oxides derived from layered double hydroxides (LDHs) containing Ni-Mg-Al and Ni-Co-Al. Upon reduction, relatively large Ni(0) domains develop in the Ni-Mg-Al catalysts, whereas in the Ni-Co-Al catalysts smaller metal particles of Ni(0) and Co(0), potentially as alloys, are formed, as evidenced by XAS, XPS, STEM and EELS. All the reduced Ni catalysts display similar selectivities towards major hydrogenation products (furfuryl alcohol and tetrahydrofurfuryl alcohol), though the side products varied with the catalyst composition. The 1.1Ni-0.8Co-Al catalyst showed the greatest activity per titrated site when compared to the other catalysts, with promising activity compared to related catalysts in the literature. The use of base metal catalysts for hydrogenation of furanic compounds may be a promising alternative to the well-studied precious metal catalysts for making biomass-derived chemicals if catalyst selectivity can be improved in future work by alloying or tuning metal-oxide support interactions.

  1. Anion-intercalated layered double hydroxides modified test strips for detection of heavy metal ions.

    Science.gov (United States)

    Wang, Nan; Sun, Jianchao; Fan, Hai; Ai, Shiyun

    2016-01-01

    In this work, a novel approach for facile and rapid detection of heavy metal ions using anion-intercalated layered double hydroxides (LDHs) modified test strips is demonstrated. By intercalating Fe(CN)6(4-) or S(2-) anions into the interlayers of LDHs on the filter paper, various heavy metal ions can be easily detected based on the color change before and after reaction between the anions and the heavy metal ions. Upon the dropping of heavy metal ions solutions to the test strips, the colors of the test strips changed instantly, which can be easily observed by naked eyes. With the decrease of the concentration, the color depth changed obviously. The lowest detection concentration can be up to 1×10(-6) mol L(-1). Due to the easily intercalation of anions into the interlayer of the LDHs on test trips, this procedure provides a general method for the construction of LDHs modified test strips for detection of heavy metal ions. The stability of the prepared test strips is investigated. Furthermore, all the results were highly reproducible. The test strips may have potential applications in environmental monitoring fields.

  2. Performance Improvement of GaN Based Schottky Barrier Ultraviolet Photodetector by Adding a Thin AlGaN Window Layer

    Institute of Scientific and Technical Information of China (English)

    ZHOU Mei; ZHAO De-Gang

    2007-01-01

    We propose a new structure of GaN based Schottky barrier ultraviolet photodetector, in which a thin n-type AlGaN window layer is added on the conventional n--GaN/n+-GaN device structure. The performance of the Schottky barrier ultraviolet photodetector is found to be improved by the new structure. The simulation result shows that the new structure can reduce the negative effect of surface states on the performance of Schottky barrier GaN photodetectors, improving the quantum efficiency and decreasing the dark current. The investigations suggest that the new photodetector can exhibit a better responsivity by choosing a suitably high carrier concentration and thin thickness for the AlGaN window layer.

  3. Fullerenes as adhesive layers for mechanical peeling of metallic, molecular and polymer thin films.

    Science.gov (United States)

    Wieland, Maria B; Slater, Anna G; Mangham, Barry; Champness, Neil R; Beton, Peter H

    2014-01-01

    We show that thin films of C60 with a thickness ranging from 10 to 100 nm can promote adhesion between a Au thin film deposited on mica and a solution-deposited layer of the elastomer polymethyldisolaxane (PDMS). This molecular adhesion facilitates the removal of the gold film from the mica support by peeling and provides a new approach to template stripping which avoids the use of conventional adhesive layers. The fullerene adhesion layers may also be used to remove organic monolayers and thin films as well as two-dimensional polymers which are pre-formed on the gold surface and have monolayer thickness. Following the removal from the mica support the monolayers may be isolated and transferred to a dielectric surface by etching of the gold thin film, mechanical transfer and removal of the fullerene layer by annealing/dissolution. The use of this molecular adhesive layer provides a new route to transfer polymeric films from metal substrates to other surfaces as we demonstrate for an assembly of covalently-coupled porphyrins.

  4. Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs) based Nanocomposites

    Science.gov (United States)

    Rahneshin, Vahid; Khosravi, Farhad; Ziolkowska, Dominika A.; Jasinski, Jacek B.; Panchapakesan, Balaji

    2016-10-01

    The ability to convert photons of different wavelengths directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Here, using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2H-MoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. Applying uniaxial tensile strains to the semiconducting few-layer 2H-MoS2 crystals in the nanocomposite resulted in spatially varying energy levels inside the nanocomposite that enhanced the broadband optical absorption up to 2.3 eV and subsequent mechanical response. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies that is not achievable using conventional thin film semiconductors.

  5. Modeling hydrodynamic flows in plasma fluxes when depositing metal layer on the surface of catalyst converters

    Science.gov (United States)

    Chinakhov, D. A.; Sarychev, V. D.; Granovsky, A. Yu; Solodsky, S. A.; Nevsky, S. A.; Konovalov, S. V.

    2017-01-01

    Air pollution with harmful substances resulting from combustion of liquid hydrocarbons and emitted into atmosphere became one of the global environmental problems in the late 20th century. The systems of neutralization capable to reduce toxicity of exhaust gases several times are very important for making environmentally safer combustion products discharged into the atmosphere. As revealed in the literature review, one of the most promising purification procedures is neutralization of burnt gases by catalyst converter systems. The principal working element in the converter is a catalytic layer of metals deposited on ceramics, with thickness 20-60 micron and a well-developed micro-relief. The paper presents a thoroughly substantiated new procedure of deposing a nano-scale surface layer of metal-catalyst particles, furthering the utilization of catalysts on a new level. The paper provides description of mathematical models and computational researches into plasma fluxes under high-frequency impulse input delivered to electrode material, explorations of developing Kelvin-Helmholtz, Marangoni and magnetic hydrodynamic instabilities on the surface of liquid electrode metal droplet in the nano-scale range of wavelengths to obtain a flow of nano-meter particles of cathode material. The authors have outlined a physical and mathematical model of magnetic and hydrodynamic instability for the case of melt flowing on the boundary with the molten metal with the purpose to predict the interphase shape and mutual effect of formed plasma jet and liquid metal droplet on the electrode in the nano-scale range of wavelengths at high-frequency impact on the boundary “electrode-liquid layer”.

  6. Behaviors of Oxide Layer at Interface between Semi-solid Filler Metal and Aluminum Matrix Composites during Vibration

    Institute of Scientific and Technical Information of China (English)

    Lei Shi; Jiuchun Yan; Yanfei Han; Bo Peng

    2011-01-01

    The joint interface between semi-solid Zn-Al filler metal and SiCp/Al composites with applying vibration for different time was examined. With increasing vibrating time, the oxide layer was disrupted prior at the centre to the periphery of the interface. And the solid grains near the centre of interface in semi-solid filler metal aggregated into two solid regions and compressed the composites during vibration; the solid grains near the periphery of interface moved toward the edge and scraped the composites during vibration. The models of disrupting oxide layer under the vibration condition were developed. At the centre of interface, the oxide layer was tore and stripped during the solid grains in the semi-solid filler metal depressing the composites with a very high compressive stress. At the periphery of interface, the oxide layer was cut and stripped into the filler metal during the solid grains scraping the interface.

  7. Layered spherical carbon composites with nanoparticles of different metals grown simultaneously inside and outside.

    Science.gov (United States)

    Tang, Shaochun; Vongehr, Sascha; Meng, Xiangkang

    2012-03-01

    We report a general one-step route to place nanoparticles (NPs) of different noble metals controllably into interior or surface locations of submicron nanoporous carbon spheres (CSs). In particular, Pd and Au NPs can be easily put either inside or outside of the CSs by selecting these metals' differently charged precursor ions. Employing mixed precursor solutions, the method allows different metals to grow simultaneously yet selectively in the separate locations, thus resulting in composites with a complex layered structure, for example Pd or Au outside and Ag inside, Au or Pt outside and Pd inside, and other combinations. The synthesis is fast and needs no additional steps like a functionalization of surfaces. It crucially involves microwave heating, the power setting of which further influences the locations and sizes of the NPs especially in the interior of the amorphous carbon matrix. The three-dimensional composite structures are analyzed by transmission electron microscopy and energy dispersed x-ray spectroscopy combined with quantitative analysis by comparison with simulation. The UV-visible absorption of monometallic and layered composites is compared. The involved mechanisms leading to the selective decoration are discussed; important aspects being the charge of the precursor ions and selective microwave absorption.

  8. Growth and spectroscopic characterization of monolayer and few-layer hexagonal boron nitride on metal substrates

    Science.gov (United States)

    Feigelson, Boris N.; Bermudez, Victor M.; Hite, Jennifer K.; Robinson, Zachary R.; Wheeler, Virginia D.; Sridhara, Karthik; Hernández, Sandra C.

    2015-02-01

    Atomically thin two dimensional hexagonal boron nitride (2D h-BN) is one of the key materials in the development of new van der Waals heterostructures due to its outstanding properties including an atomically smooth surface, high thermal conductivity, high mechanical strength, chemical inertness and high electrical resistance. The development of 2D h-BN growth is still in the early stages and largely depends on rapid and accurate characterization of the grown monolayer or few layers h-BN films. This paper demonstrates a new approach to characterizing monolayer h-BN films directly on metal substrates by grazing-incidence infrared reflection absorption spectroscopy (IRRAS). Using h-BN films grown by atmospheric-pressure chemical vapor deposition on Cu and Ni substrates, two new sub-bands are found for the A2u out-of-plane stretching mode. It is shown, using both experimental and computational methods, that the lower-energy sub-band is related to 2D h-BN coupled with substrate, while the higher energy sub-band is related to decoupled (or free-standing) 2D h-BN. It is further shown that this newly-observed fine structure in the A2u mode can be used to assess, quickly and easily, the homogeneity of the h-BN-metal interface and the effects of metal surface contamination on adhesion of the layer.

  9. Characterization of electroless nickel as a seed layer for silicon solar cell metallization

    Indian Academy of Sciences (India)

    Mehul C Raval; Chetan S Solanki

    2015-02-01

    Electroless nickel plating is a suitable method for seed layer deposition in Ni–Cu-based solar cell metallization. Nickel silicide formation and hence contact resistivity of the interface is largely influenced by the plating process and annealing conditions. In the present work, a thin seed layer is deposited from neutral pH and alkaline electroless nickel baths which are annealed in the range of 400–420°C for silicide morphology and contact resistivity studies. A minimum contact resistivity of 7 m cm2 is obtained for seed layer deposited from alkaline bath. Silicide formation for Pd-activated samples leads to uniform surface morphology as compared with unactivated samples due to non-homogeneous migration of nickel atoms at the interface. Formation of nickel phosphides during annealing and the presence of SiO2 at Ni–Si interface creates isolated Ni2Si–Si interface with limited supply of silicon. Such an interface leads to the formation of high resistivity metal-rich Ni3Si silicide phase which limits the reduction in contact resistivity.

  10. Layer modeling of zinc removal from metallic mixture of waste printed circuit boards by vacuum distillation.

    Science.gov (United States)

    Gao, Yujie; Li, Xingang; Ding, Hui

    2015-08-01

    A layer model was established to elucidate the mechanism of zinc removal from the metallic mixture of waste printed circuit boards by vacuum distillation. The removal process was optimized by response surface methodology, and the optimum operating conditions were the chamber pressure of 0.1Pa, heating temperature of 923K, heating time of 60.0min, particle size of 70 mesh (0.212mm) and initial mass of 5.25g. Evaporation efficiency of zinc, the response variable, was 99.79%, which indicates that the zinc can be efficiently removed. Based on the experimental results, a mathematical model, which bears on layer structure, evaporation, mass transfer and condensation, interprets the mechanism of the variable effects. Especially, in order to reveal blocking effect on the zinc removal, the Blake-Kozeny-Burke-Plummer equation was introduced into the mass transfer process. The layer model can be applied to a wider range of metal removal by vacuum distillation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. A flexible ligand-based wavy layered metal-organic framework for lithium-ion storage.

    Science.gov (United States)

    An, Tiance; Wang, Yuhang; Tang, Jing; Wang, Yang; Zhang, Lijuan; Zheng, Gengfeng

    2015-05-01

    A substantial challenge for direct utilization of metal-organic frameworks (MOFs) as lithium-ion battery anodes is to maintain the rigid MOF structure during lithiation/delithiation cycles. In this work, we developed a flexible, wavy layered nickel-based MOF (C20H24Cl2N8Ni, designated as Ni-Me4bpz) by a solvothermal approach of 3,3',5,5'-tetramethyl-4,4'-bipyrazole (H2Me4bpz) with nickel(II) chloride hexahydrate. The obtained MOF materials (Ni-Me4bpz) with metal azolate coordination mode provide 2-dimensional layered structure for Li(+) intercalation/extraction, and the H2Me4bpz ligands allow for flexible rotation feature and structural stability. Lithium-ion battery anodes made of the Ni-Me4bpz material demonstrate excellent specific capacity and cycling performance, and the crystal structure is well preserved after the electrochemical tests, suggesting the potential of developing flexible layered MOFs for efficient and stable electrochemical storage. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Al2O3/Au/Al2O3 layered films as tritium permeation barrier%Al2O3/Au/Al2O3层状阻氚薄膜

    Institute of Scientific and Technical Information of China (English)

    汤波楷; 何业东; 曹江利; 唐涛; 饶咏初

    2012-01-01

    Single Al2O3 films, single Au films and Al2O3/Au/Al2O3 layered films were prepared on 316L stainless steel substrate by megnetron sputtering. Then vapour phase permeation experiment of deuterium through 316L substrate and its film materials were carried out at 500℃ with a partial pressure of deuterium 0. 06 MPa. The results indicate that morphology of the three films is good and no phenomenon of cracking and spalling is found after deuterium permeation. Deuterium permeation reduction factors (PRF) of these films are over one order of magnitude relative to clean 316L. The performance of barrying deuterium increases progressively in the order of single Al2O3 films, single Au films and Al2O3/Au/Al2O3 ayered films. Al2O3/Au/Al2O3 layered films exhibit excellent performance of barrying deuterium because the mechanical properties of the layered films are improved visibly by the ductile interlayer Au and the interdiffusion between Au and 316L substratc is hindered by Al2O3 layer, so Au can give full play to barry deuterium. The study shows that layered films like precious metal integrated with ceramics is a new way in the domain of tritium permeation barrier development.%采用磁控溅射法在316L不锈钢基体上分别沉积单层Al2O3,膜、单层Au膜以及Al2O3/Au/Al2O3层状薄膜。采用气相渗透法在500℃,氘分压为0.06MPa条件下测试了薄膜的阻氘性能。结果表明,3种薄膜氘渗透后,薄膜的形貌良好,无开裂、无剥落的现象,氘渗透率减低因子均比316L不锈钢基材增大一个数量级以上,阻氘效能按单层Al2O3,膜、单层Au膜以及Al2O3/Au/Al2O3层状薄膜依次递升。Al2O3/Au/Al2O3层状薄膜的优异阻氘效能可归因于,延性的Au夹层使层状薄膜的力学性能得到显著提高;Al2O3层能阻止Au与基体间互扩散,使Au能充分发挥阻氘效能。本研究表明,由贵金属与陶瓷阻氚材料构成的层状薄膜是发展阻氚涂层的新途径。

  13. Photovoltaic performance of bithiazole-bridged dyes-sensitized solar cells employing semiconducting quantum dot CuInS2 as barrier layer material.

    Science.gov (United States)

    Guo, Fuling; He, Jinxiang; Li, Jing; Wu, Wenjun; Hang, Yandi; Hua, Jianli

    2013-10-15

    In this work, the quantum dot CuInS2 layer was deposited on TiO2 film using successive ionic layer absorption and reaction (SILAR) method, and then two bithiazole-bridged dyes (BTF and BTB) were sensitized on the CuInS2/TiO2 films to form dye/CuInS2/TiO2 photoanodes for DSSCs. It was found that the quantum dots CuInS2 as an energy barrier layer not only could effectively improve open-circuit voltage (Voc) of solar cell, but also increase short-circuit photocurrent (Jsc) compared to the large decrease in Jsc of ZnO as energy barrier layer. The electrochemical impedance spectroscopy (EIS) measurement showed that the CuInS2 formed a barrier layer to suppress the recombination from injection electron to the electrolyte and improve open-circuit voltage. Finally, the open-circuit voltage increased about 22 and 27mV for BTF and BTB-/CuInS2/TiO2-based cells, the overall conversion efficiencies also reached to 7.20% and 6.74%, respectively.

  14. Shift and elimination of microwave Fabry-Perot resonances in a dielectric covered with a thin metal layer

    Science.gov (United States)

    Ragulis, Paulius; Simniškis, Rimantas; Kancleris, Žilvinas

    2015-04-01

    In this paper, we consider a plane electromagnetic wave incident onto a dielectric plate, which has one surface covered with a thin layer of metal. An oblique incident angle was considered for the TE (s polarization in optic) and TM (p polarization) plane waves. The thin metal layer is treated as an infinitesimal thickness. It was characterized by a surface conductivity and accounted for by a tangential magnetic field component step induced by the current flow in the metal layer. Compact expressions, which describe the reflection, transmission and absorption in a dielectric plate covered with a thin layer of metal, have been obtained. It was shown that by choosing the appropriate surface conductivity, the Fabry-Perot transmission resonances can be shifted to the position where the maximum reflection is observed in the case of an uncovered dielectric. On the other hand, the elimination of the Fabry-Perot resonances can be also achieved by choosing a proper metal surface conductivity. Measurements of the reflection from the glass covered with a thin layer of metal have been performed in a wide microwave frequency range (2-12 GHz) revealing a large difference in the measured reflection coefficient from the dielectric and metalized surfaces. The measured results fit well with those calculated by employing analytical expressions obtained in this paper.

  15. Enhanced water vapor barrier properties for biopolymer films by polyelectrolyte multilayer and atomic layer deposited Al{sub 2}O{sub 3} double-coating

    Energy Technology Data Exchange (ETDEWEB)

    Hirvikorpi, Terhi [VTT Technical Research Centre of Finland, Biologinkuja 7, Espoo, P.O. Box 1000, FI-02044 VTT (Finland); Vaehae-Nissi, Mika, E-mail: mika.vaha-nissi@vtt.fi [VTT Technical Research Centre of Finland, Biologinkuja 7, Espoo, P.O. Box 1000, FI-02044 VTT (Finland); Harlin, Ali [VTT Technical Research Centre of Finland, Biologinkuja 7, Espoo, P.O. Box 1000, FI-02044 VTT (Finland); Salomaeki, Mikko [University of Turku, Department of Chemistry, Laboratory of Materials Chemistry and Chemical Analysis, Vatselankatu 2, FI-20014 (Finland); Areva, Sami [Tampere University of Technology, Department of Biomedical Engineering, Biokatu 6, P.O. Box 692, FI-33101 Tampere (Finland); Korhonen, Juuso T. [Aalto University School of Science, Department of Applied Physics, P.O. Box 15100 FI-00076 AALTO, Espoo (Finland); Karppinen, Maarit [Aalto University School of Chemical Technology, Laboratory of Inorganic Chemistry, P.O. Box 16100, FI-00076 AALTO, Espoo (Finland)

    2011-09-01

    Commercial polylactide (PLA) films are coated with a thin (20 nm) non-toxic polyelectrolyte multilayer (PEM) film made from sodium alginate and chitosan and additionally with a 25-nm thick atomic layer deposited (ALD) Al{sub 2}O{sub 3} layer. The double-coating of PEM + Al{sub 2}O{sub 3} is found to significantly enhance the water vapor barrier properties of the PLA film. The improvement is essentially larger compared with the case the PLA film being just coated with an ALD-grown Al{sub 2}O{sub 3} layer. The enhanced water vapor barrier characteristics of the PEM + Al{sub 2}O{sub 3} double-coated PLA films are attributed to the increased hydrophobicity of the surface of these films.

  16. Capacitance of the double electrical layer on the copper-group metals in molten alkali metal halides

    Science.gov (United States)

    Kirillova, E. V.; Stepanov, V. P.

    2016-08-01

    The electrochemical impedance is measured to study the capacitance of the double electrical layer of metallic Au, Ag, and Cu as a function of potential and temperature in nine molten salts, namely, the chlorides, bromides, and iodides of sodium, potassium, and cesium. The C- E curve of a gold electrode has an additional minimum in the anodic branch. This minimum for silver is less pronounced and is only observed at low ac signal frequencies in cesium halides. The additional minimum is not detected for copper in any salt under study. This phenomenon is explained on the assumption that the adsorption of halide anions on a positively charged electrode surface has a predominantly chemical rather than an electrostatic character. The specific adsorption in this case is accompanied by charge transfer through the interface and the formation of an adsorbent-adsorbate covalent bond.

  17. Electroless copper on refractory and noble metal substrates with an ultra-thin plasma-assisted atomic layer deposited palladium layer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young-Soon [Thin Film Technology Lab, School of Chemical Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of); Kim, Hyung-Il [Thin Film Technology Lab, School of Chemical Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of); Cho, Joong-Hee [Thin Film Technology Lab, School of Chemical Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of); Seo, Hyung-Kee [Thin Film Technology Lab, School of Chemical Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of); Dar, M.A. [Thin Film Technology Lab, School of Chemical Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of); Shin, Hyung-Shik [Thin Film Technology Lab, School of Chemical Engineering, Chonbuk National University, Jeonju 561756 (Korea, Republic of); Ten Eyck, Gregory A. [Department of Physics, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Lu, Toh-Ming [Department of Physics, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Senkevich, Jay J. [Brewer Science Inc., Rolla, MO 65401 (United States)]. E-mail: jsenkevich@brewerscience.com

    2006-02-25

    Electroless Cu was investigated on refractory metal, W and TaN {sub X}, and Ir noble metal substrates with a plasma-assisted atomic layer deposited palladium layer for the potential back-end-of-the-line (BEOL) metallization of advanced integrated devices. The sodium and potassium-free Cu electroless bath consisted of: ethylenediamine tetraacetic acid (EDTA) as a chelating agent, glyoxylic acid as a reducing agent, and additional chemicals such as polyethylene glycol, 2,2'-dipyridine and RE-610 as surfactant, stabilizer and wetting agent respectively. The growth and chemical characterization of the Cu films was carried out with a field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), and Rutherford backscattering spectrometry (RBS). Group VIII metals such as Pt, Pd, etc., are stable in the electroless bath and catalytic towards the oxidation of glyoxylic acid and therefore work well for the electroless deposition of Cu. From RBS analysis, the amount of carbon and oxygen in Cu films were less than 1-3%. The Cu films were electroless deposited at 45-50 deg. C on patterned tantalum nitride with plasma-assisted atomic layer deposited (PA-ALD) Pd as a catalytic layer. Electroless Cu trench fill was successful with ultrasonic vibration, RE-610, and lowering the temperature to 45-50 deg. C on TaN {sub X} with the PA-ALD Pd catalytic layer.

  18. Double layer resist process scheme for metal lift-off with application in inductive heating of microstructures

    DEFF Research Database (Denmark)

    Ouattara, Lassana; Knutzen, Michael; Keller, Stephan Urs

    2010-01-01

    We present a new method to define metal electrodes on top of high-aspect-ratio microstructures using standard photolithography equipment and a single chromium mask. A lift-off resist (LOR) layer is implemented in an SU-8 photolithography process to selectively remove metal at the end of the proce...

  19. Hot Corrosion Behavior of Double-ceramic-layer LaTi2Al9O19/YSZ Thermal Barrier Coatings

    Institute of Scientific and Technical Information of China (English)

    XIE Xiaoyun; GUO Hongbo; GONG Shengkai; XU Huibin

    2012-01-01

    LaTi2Al9O19 (LTA) exhibits promising potential as a new kind of thermal barrier coating (TBC) material,due to its excellent high-temperature capability and low thermal conductivity.In this paper,LTA/yttria stabilized zirconia (YSZ) TBCs are produccd by atmospheric plasma spraying.Hot corrosion behavior and the related failure mechanism of the coating are investigated.Decomposition of LTA does not occur even after 1 458 hot corrosion cycles at 1 373 K,revealing good chemical stability in molten salt of Na2SO4 and NaCl.However,the molten salt infiltrates to the bond coat,causing dissolving of the thermally grown oxide (TGO) in the molten salt and hot corrosion of the bond coat.As a result,cracking of the TBC occurs within the oxide layer.In conclusion,the ceranic materials LTA and YSZ reveal good chemical stability in molten salts of Na2SO4 and NaCl,and the bond coat plays a significant role in providing protection for the component against hot corrosion in the LTA/YSZ TBCs.LTA exhibits very promising potential as a novel TBC material.

  20. Seasonal variations in the barrier layer in the South China Sea: characteristics, mechanisms and impact of warming

    Science.gov (United States)

    Zeng, Lili; Wang, Dongxiao

    2016-06-01

    A new observational dataset, the South China Sea Physical Oceanographic Dataset 2014, is examined to investigate the seasonal characteristics, formation mechanisms, and warming effects of the barrier layer (BL) in the South China Sea (SCS). Statistical analysis reveals that the BL is thicker and occurs more frequently during summer and early autumn, while in winter it often coexists with temperature inversions. The formation mechanisms are discussed from the perspective of the controlling regime and the net turbulent energy required for BL evolution. In the initial stage (March-May), the BL is absent due to weak mixing, scarce rainfall and surface warming. In the formation and maintenance stage (June-September), the BL grows in summer and persists into the transition season. The BLs can be classified into three regimes: the flux regime (in the Luzon Strait), the combined regime (in the eastern basin) and the wind regime (southeast of Vietnam). In the attenuation stage (October-February), associated with the winter monsoon, the BL mainly occurs in the combined regime (along the path of western boundary current) and the flux regime (in the southeast corner). The characteristics and generation mechanisms of the temperature inversions near the south Chinese coast, east of Vietnam, and in the Gulf of Thailand are also discussed. Our analysis further demonstrates that the BL has a significant warming effect on upper ocean temperature and heat content in the SCS.

  1. Understanding and Shaping the Morphology of the Barrier Layer of Supported Porous Anodized Alumina on Gold Underlayers.

    Science.gov (United States)

    Berger, Nele; Es-Souni, Mohammed

    2016-07-12

    Large-area ordered nanorod (NR) arrays of various functional materials can be easily and cost-effectively processed using on-substrate anodized porous aluminum oxide (PAO) films as templates. However, reproducibility in the processing of PAO films is still an issue because they are prone to delamination, and control of fabrication parameters such as electrolyte type and concentration and anodizing time is critical for making robust templates and subsequently mechanically reliable NR arrays. In the present work, we systematically investigate the effects of the fabrication parameters on pore base morphology, devise a method to avoid delamination, and control void formation under the barrier layer of PAO films on gold underlayers. Via systematic control of the anodization parameters, particularly the anodization current density and time, we follow the different stages of void development and discuss their formation mechanisms. The practical aspect of this work demonstrates how void size can be controlled and how void formation can be utilized to control the shape of NR bases for improving the mechanical stability of the NRs.

  2. Chemical deposition of selenium layers for selenization of sputtered and electrodeposited Cu–Zn–Sn metallic layers for photovoltaic application

    Energy Technology Data Exchange (ETDEWEB)

    Delbos, Sebastien; Benmoussa, Marya; Bodeux, Romain; Gougaud, Corentin; Naghavi, Negar, E-mail: negar.naghavi@edf.fr

    2015-08-31

    One of the key steps for high efficiency kesterite based solar cells is the control of the growth conditions of the kesterite phase from precursors. In this work, chemical deposition was used to introduce the selenium needed for Cu–Zn–Sn selenization and Cu{sub 2}ZnSnSe{sub 4} (CZTSe) synthesis. The influence of annealing time and precursor morphology based on deposition techniques (electrodeposition or sputtering) on the reaction path and kinetics of growth and degradation of kesterite phase was studied using scanning electron microscopy, X-ray diffraction and Raman characterizations. Important differences were detected between porous electrodeposited precursors and dense sputtered precursors. It was suggested that this difference comes from the morphology of the precursors, and that a control of the morphology is critical for the control of the annealing processes in CZTSe synthesis. - Highlights: • Cu–Zn–Sn metallic precursors deposited by co-sputtering and co-electrodeposition • Annealing of Cu{sub 2}ZnSnSe{sub 4} (CZTSe) using chemical deposition of Se layer • Kinetics of the formation and decomposition of CZTSe • Role of the morphology and composition of precursors on the CZTSe properties.

  3. Initial stresses in two-layer metal domes due to imperfections of their production and assemblage

    Directory of Open Access Journals (Sweden)

    Lebed Evgeniy Vasil’evich

    2015-04-01

    Full Text Available The process of construction of two-layer metal domes is analyzed to illustrate the causes of initial stresses in the bars of their frames. It has been noticed that it is impossible to build such structures with ideal geometric parameters because of imperfections caused by objective reasons. These imperfections cause difficulties in the process of connection of the elements in the joints. The paper demonstrates the necessity of fitting operations during assemblage that involve force fitting and yield initial stresses due to imperfections. The authors propose a special method of computer modeling of enforced elimination of possible imperfections caused by assemblage process and further confirm the method by an analysis of a concrete metal dome.

  4. Layered reduced graphene oxide with nanoscale interlayer gaps as a stable host for lithium metal anodes

    Science.gov (United States)

    Lin, Dingchang; Liu, Yayuan; Liang, Zheng; Lee, Hyun-Wook; Sun, Jie; Wang, Haotian; Yan, Kai; Xie, Jin; Cui, Yi

    2016-07-01

    Metallic lithium is a promising anode candidate for future high-energy-density lithium batteries. It is a light-weight material, and has the highest theoretical capacity (3,860 mAh g-1) and the lowest electrochemical potential of all candidates. There are, however, at least three major hurdles before lithium metal anodes can become a viable technology: uneven and dendritic lithium deposition, unstable solid electrolyte interphase and almost infinite relative dimension change during cycling. Previous research has tackled the first two issues, but the last is still mostly unsolved. Here we report a composite lithium metal anode that exhibits low dimension variation (˜20%) during cycling and good mechanical flexibility. The anode is composed of 7 wt% ‘lithiophilic’ layered reduced graphene oxide with nanoscale gaps that can host metallic lithium. The anode retains up to ˜3,390 mAh g-1 of capacity, exhibits low overpotential (˜80 mV at 3 mA cm-2) and a flat voltage profile in a carbonate electrolyte. A full-cell battery with a LiCoO2 cathode shows good rate capability and flat voltage profiles.

  5. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting

    Science.gov (United States)

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-01-01

    A fundamental strategy to enhance optical transmission through a continuous metallic film based on strong interference dominated by interface phase shift is developed. In a metallic film coated with a thin semiconductor film, both transmission and absorption are simultaneously enhanced as a result of dramatically reduced reflection. For a 50-nm-thick Ag film, experimental transmission enhancement factors of 4.5 and 9.5 are realized by exploiting Ag/Si non-symmetric and Si/Ag/Si symmetric geometries, respectively. These planar layered films for transmission enhancement feature ultrathin thickness, broadband and wide-angle operation, and reduced resistance. Considering one of their potential applications as transparent metal electrodes in solar cells, a calculated 182% enhancement in the total transmission efficiency relative to a single metallic film is expected. This strategy relies on no patterned nanostructures and thereby may power up a wide spectrum of energy-harvesting applications such as thin-film photovoltaics and surface photocatalysis. PMID:27404510

  6. Solution-Processed Metal Oxides as Efficient Carrier Transport Layers for Organic Photovoltaics.

    Science.gov (United States)

    Choy, Wallace C H; Zhang, Di

    2016-01-27

    Carrier (electron and hole) transport layers (CTLs) are essential components for boosting the performance of various organic optoelectronic devices such as organic solar cells and organic light-emitting diodes. Considering the drawbacks of conventional CTLs (easily oxidized/unstable, demanding/costly fabrication, etc.), transition metal oxides with good carrier transport/extraction and superior stability have drawn extensive research interest as CTLs for next-generation devices. In recent years, many research efforts have been made toward the development of solution-based metal oxide CTLs with the focus on low- or even room-temperature processes, which can potentially be compatible with the deposition processes of organic materials and can significantly contribute to the low-cost and scale-up of organic devices. Here, the recent progress of different types of solution-processed metal oxide CTLs are systematically reviewed in the context of organic photovoltaics, from synthesis approaches to device performance. Different approaches for further enhancing the performance of solution-based metal oxide CTLs are also discussed, which may push the future development of this exciting field.

  7. Metal based gas diffusion layers for enhanced fuel cell performance at high current densities

    Science.gov (United States)

    Hussain, Nabeel; Van Steen, Eric; Tanaka, Shiro; Levecque, Pieter

    2017-01-01

    The gas diffusion layer strongly influences the performance and durability of polymer electrolyte fuel cells. A major drawback of current carbon fiber based GDLs is the non-controlled variation in porosity resulting in a random micro-structure. Moreover, when subjected to compression these materials show significant reduction in porosity and permeability leading to water management problems and mass transfer losses within the fuel cell. This study investigated the use of uniform perforated metal sheets as GDLs in conjunction with microchannel flowfields. A metal sheet design with a pitch of 110 μm and a hole diameter of 60 μm in combination with an MPL showed superior performance in the high current density region compared to a commercially available carbon paper based GDL in a single cell environment. Fuel cell testing with different oxidants (air, heliox and oxygen) indicate that the metal sheet offers both superior diffusion and reduced flooding in comparison to the carbon based GDL. The presence of the MPL has been found to be critical to the functionality of the metal sheet suggesting that the MPL design may represent an important optimisation parameter for further improvements in performance.

  8. Flat metallic surface gratings with sub-10 nm gaps controlled by atomic-layer deposition

    Science.gov (United States)

    Chen, Borui; Ji, Dengxin; Cheney, Alec; Zhang, Nan; Song, Haomin; Zeng, Xie; Thomay, Tim; Gan, Qiaoqiang; Cartwright, Alexander

    2016-09-01

    Atomic layer lithography is a recently reported new technology to fabricate deep-subwavelength features down to 1-2 nm, based on combinations of electron beam lithography (EBL) and atomic layer deposition (ALD). However, the patterning area is relatively small as limited by EBL, and the fabrication yield is not very high due to technical challenges. Here we report an improved procedure to fabricate flat metallic surfaces with sub-10 nm features based on ALD processes. To demonstrate the scalability of the new manufacturing method, we combine the ALD process with large area optical interference patterning, which is particularly promising for the development of practical applications for nanoelectronics and nanophotonics with extremely strong confinement of electromagnetic fields.

  9. Emerging Energy Applications of Two-Dimensional Layered Transition Metal Dichalcogenides

    KAUST Repository

    Li, Henan

    2015-10-31

    Transition metal dichalcogenides (TMDCs) have attracted significant attention for their great potential in nano energy. TMDC layered materials represent a diverse and largely untapped source of 2D systems. High-quality TMDC layers with an appropriate size, variable thickness, superior electronic and optical properties can be produced by the exfoliation or vapour phase deposition method. Semiconducting TMDC monolayers have been demonstrated feasible for various energy related applications, where their electronic properties and uniquely high surface areas offer opportunities for various applications such as nano generators, green electronics, electrocatalytic hydrogen generation and energy storage. In this review, we start from the structure, properties and preparation, followed by detailed discussions on the development of TMDC-based nano energy applications. Graphical abstract The structure characterizations and preparative methods of 2D TMDCs have obtained significant progresses. Their recent advances for nano energy generation, solar harvesting, conversion and storage, and green electronics are reviewed.

  10. Valley polarization in magnetically doped single-layer transition-metal dichalcogenides

    KAUST Repository

    Cheng, Yingchun

    2014-04-28

    We demonstrate that valley polarization can be induced and controlled in semiconducting single-layer transition-metal dichalcogenides by magnetic doping, which is important for spintronics, valleytronics, and photonics devices. As an example, we investigate Mn-doped MoS2 by first-principles calculations. We study how the valley polarization depends on the strength of the spin orbit coupling and the exchange interaction and discuss how it can be controlled by magnetic doping. Valley polarization by magnetic doping is also expected for other honeycomb materials with strong spin orbit coupling and the absence of inversion symmetry.

  11. On the surface recombination current of metal-insulator semiconductor inversion layer solar cells

    DEFF Research Database (Denmark)

    Nielsen, Otto M.

    1981-01-01

    Current voltage characteristics have been obtained under dark and illuminated conditions for Al-SiO2-pSi metal-insulator semiconductor inversion layer solar cells. The cells were fabricated on ~ and ~ oriented substrates with resistivities in the range of 8–15 Omega cm. For ~ cells the open circuit...... voltages Voc were found to be lower than for ~ cells. The measured differences in Voc were higher than expected from the dark characteristics which is explained as a difference in the surface recombination current due to a higher interface state density Nss of ~ cells. Journal of Applied Physics...

  12. In situ hard x-ray photoemission spectroscopy of barrier-height control at metal/PMN-PT interfaces

    Science.gov (United States)

    Kröger, E.; Petraru, A.; Quer, A.; Soni, R.; Kalläne, M.; Pertsev, N. A.; Kohlstedt, H.; Rossnagel, K.

    2016-06-01

    Metal-ferroelectric interfaces form the basis of novel electronic devices. A key effect determining the device functionality is the bias-dependent change of the electronic energy-level alignment at the interface. Here, hard x-ray photoelectron spectroscopy (HAXPES) is used to determine the energy-level alignment at two metal-ferroelectric interfaces—Au versus SrRuO3 on the relaxor ferroelectric Pb (Mg1 /3Nb2 /3 )0.72Ti0.28O3 (PMN-PT)—directly in situ as a function of electrical bias. The bias-dependent average shifts of the PMN-PT core levels are found to have two dominant contributions on the 0.1 -1-eV energy scale: one depending on the metal electrode and the remanent electric polarization and the other correlated with electric-field-induced strain. Element-specific deviations from the average shifts are smaller than 0.1 eV and appear to be related to predicted dynamical charge variations in PMN-PT. In addition, the efficiency of ferroelectric polarization switching is shown to be reduced near the coercive field under x-ray irradiation. The results establish HAXPES as a tool for the in operando investigation of metal-ferroelectric interfaces and suggest electric-field-induced modifications of the polarization distribution as a novel way to control the barrier height at such interfaces.

  13. Enhanced Lifetime of Polymer Solar Cells by Surface Passivation of Metal Oxide Buffer Layers.

    Science.gov (United States)

    Venkatesan, Swaminathan; Ngo, Evan; Khatiwada, Devendra; Zhang, Cheng; Qiao, Qiquan

    2015-07-29

    The role of electron selective interfaces on the performance and lifetime of polymer solar cells were compared and analyzed. Bilayer interfaces consisting of metal oxide films with cationic polymer modification namely poly ethylenimine ethoxylated (PEIE) were found to enhance device lifetime compared to bare metal oxide films when used as an electron selective cathode interface. Devices utilizing surface-modified metal oxide layers showed enhanced lifetimes, retaining up to 85% of their original efficiency when stored in ambient atmosphere for 180 days without any encapsulation. The work function and surface potential of zinc oxide (ZnO) and ZnO/PEIE interlayers were evaluated using Kelvin probe and Kelvin probe force microscopy (KPFM) respectively. Kelvin probe measurements showed a smaller reduction in work function of ZnO/PEIE films compared to bare ZnO films when aged in atmospheric conditions. KPFM measurements showed that the surface potential of the ZnO surface drastically reduces when stored in ambient air for 7 days because of surface oxidation. Surface oxidation of the interface led to a substantial decrease in the performance in aged devices. The enhancement in the lifetime of devices with a bilayer interface was correlated to the suppressed surface oxidation of the metal oxide layers. The PEIE passivated surface retained a lower Fermi level when aged, which led to lower trap-assisted recombination at the polymer-cathode interface. Further photocharge extraction by linearly increasing voltage (Photo-CELIV) measurements were performed on fresh and aged samples to evaluate the field required to extract maximum charges. Fresh devices with a bare ZnO cathode interlayer required a lower field than devices with ZnO/PEIE cathode interface. However, aged devices with ZnO required a much higher field to extract charges while aged devices with ZnO/PEIE showed a minor increase compared to the fresh devices. Results indicate that surface modification can act as a

  14. Research Update: Magnetoionic control of magnetization and anisotropy in layered oxide/metal heterostructures

    Directory of Open Access Journals (Sweden)

    K. Duschek

    2016-03-01

    Full Text Available Electric field control of magnetization and anisotropy in layered structures with perpendicular magnetic anisotropy is expected to increase the versatility of spintronic devices. As a model system for reversible voltage induced changes of magnetism by magnetoionic effects, we present several oxide/metal heterostructures polarized in an electrolyte. Room temperature magnetization of Fe-O/Fe layers can be changed by 64% when applying only a few volts in 1M KOH. In a next step, the bottom interface of the in-plane magnetized Fe layer is functionalized by an L10 FePt(001 underlayer exhibiting perpendicular magnetic anisotropy. During subsequent electrocrystallization and electrooxidation, well defined epitaxial Fe3O4/Fe/FePt heterostructures evolve. The application of different voltages leads to a thickness change of the Fe layer sandwiched between Fe-O and FePt. At the point of transition between rigid magnet and exchange spring magnet regime for the Fe/FePt bilayer, this induces a large variation of magnetic anisotropy.

  15. Double layered self-expanding metal stents for malignant esophageal obstruction, especially across the gastroesophageal junction

    Institute of Scientific and Technical Information of China (English)

    Min Dae Kim; Su Bum Park; Dae Hwan Kang; Jae Hyung Lee; Cheol Woong Choi; Hyung Wook Kim; Chung Uk Chung

    2012-01-01

    AIM:TO evaluate the clinical outcomes of double-layered self-expanding metal stents (SEMS) for treatment of malignant esophageal obstruction according to whether SEMS crosses the gastroesophageal junction (GEJ).METHODS:Forty eight patients who underwent the SEMS insertion for malignant esophageal obstruction were enrolled.Patients were classified as GEJ group (SEMS across GEHm 18 patients) and non-GEJ group (SEMS above GEJ,30 patients) according to SEMS position.Double layered (outer uncovered and inner covered stent) esophageal stents were placed.RESULTS:The SEMS insertion and the clinical improvement were achieved in all patients in both groups.Stent malfunction occurred in seven patients in the GEJ group and nine patients in the non-GEJ group.Tumor overgrowth occurred in five and eight patients,respectively,food impaction occurred in one patient in each group,and stent migration occurred in one and no patient,respectively.There were no significant differences between the two groups.Reflux esophagitis occurred more frequently in the GEJ group (eight vs five patients,P =0.036) and was controlled by proton pump inhibitor.Aspiration pneumonia occurred in zero and five patients,respectively,and tracheoesophageal fistula occurred in zero and two patients,respectively.CONCLUSION:Double-layered SEMS are a feasible and effective treatment when placed across the GEJ for malignant esophageal obstruction.Double-layered SEMS provide acceptable complications,especially migration,although reflux esophagitis is more common in the GEJ group.

  16. Effects of solvent on the formation of the MUA monolayer on Si and its diffusion barrier properties for Cu metallization

    Science.gov (United States)

    Rahman, Mohammad Arifur; Han, Jung Suk; Jeong, Kyunghoon; Nam, Ho-seok; Lee, Jaegab

    2014-05-01

    We investigated the effects of solvents, such as ethanol and isooctane, on self-assembly of the mercaptoundecanoic acid (MUA) monolayer on Si and its diffusion barrier properties for Cu metallization. The use of isooctane as a solvent produced MUA self-assembled monolayers (SAMs) (˜1.3 nm thick) on Si. These acted as an effective diffusion barrier against Cu diffusion up to 200°C. In contrast, the MUA SAMs produced by ethanol allowed the diffusion of Cu to a MUA-Si interface at 200°C, stimulating the out-diffusion of Si into Cu and thus resulting in the degraded diffusion barrier properties. This was possibly due to the partial formation of interplane hydrogen bonding between the terminal groups of the bound acid and free thiol groups. This provided less dense thiol surface groups, thus leading to poor adhesion of Cu to MUA SAMs. The fabricated Cu/isooctane-assisted MUA source/drain electrode a-Si:H thin film transistors with a channel length of 10 µm exhibited an excellent electron mobility of 0.74 cm2/V-s, threshold voltage of -0.51 V, I on / I off ratio of 3.25 × 106, specific contact resistance of 4.24 Ω-cm2 after annealing at 200°C.

  17. Development of Ion-Plasma Refractory Metallic Layers of Heat-Insulating Coatings for Cooled Turbine Rotor Blades

    Science.gov (United States)

    Budinovskii, S. A.; Muboyadzhyan, S. A.; Gayamov, A. M.; Matveev, P. V.

    2014-03-01

    Alloys ZhS32 and ZhS36 with heat-protection coatings (HPC) consisting of external ceramic layers and internal refractory metallic layers are studied. The coated alloys are tested for heat fastness and high-temperature strength at 1100 - 1150°C. The HPC with a metallic layer of the (Ni - Cr - Al - Hf) + Al system are shown to be more advantageous than similar HPC based on an SPD-2 + VSDP-16 commercial refractory coating. The effect of the HPC on the characteristics of high-temperature strength and fatigue resistance of alloys ZhS32 and ZhS36 is investigated.

  18. a Comprehensive Model of Global Transport and Localized Layering of Metallic Ions in the Upper Atmosphere.

    Science.gov (United States)

    Carter, Leonard Nelson, Jr.

    1995-01-01

    The physics and chemistry of atmospheric metallic ions have been an active area of research for many years; however, a number of issues remain unresolved. Numerical models have been developed and used to establish and validate theories of metallic ion dynamics. While agreement with observational measurements has generally been satisfactory, these models have embodied highly simplified pictures of the total physical system, usually focusing on a single aspect of metallic dynamics. The model described herein is considered the first to simulate all phases of the life cycle of metallic ions. This cycle begins with the initial deposition of metallics through meteor ablation and sputtering, followed by conversion of neutral atoms to ions through photoionization and charge exchange with ambient ions. Global ion transport arising from daytime electric fields and poleward/downward diffusion along geomagnetic field lines, localized transport and layer formation through descending convergent nulls in the thermospheric tidal wind field, and finally annihilation by chemical neutralization and compound formation are treated. The end result of this developmental effort is a model that has not only shown good agreement with observations, but has also shed new light on the interdependencies of the physical and chemical processes affecting atmospheric metallics. The model has been used, in both one- and two -dimensional versions, to simulate ion dynamics in the vertical dimension (at Arecibo, PR, 19^circ N, 67^circW), and in the vertical and meridional dimensions from the equator to 45^circN, ranging over a 90 to 4000 km altitude span. Model output analysis confirms the dominant role of both global and local transport to the ions' life cycle, showing that upward forcing from the equatorial electric field is critical to global movement, and that diurnal and semidiurnal tidal winds are responsible for the formation of dense ion layers in the 90-150 km height region. The model also

  19. Yttria-stabilized zirkonia / gadolinium zirconate double-layer plasma-sprayed thermal barrier coating systems (TBCs)

    Energy Technology Data Exchange (ETDEWEB)

    Bakan, Emine

    2015-07-01

    Thermal barrier coating (TBC) research and development is driven by the desirability of further increasing the maximum inlet temperature in a gas turbine engine. A number of new top coat ceramic materials have been proposed during the last decades due to limited temperature capability (1200 C) of the state-of-the-art yttria-stabilized zirconia (7 wt. % Y{sub 2}O{sub 3}-ZrO{sub 2}, YSZ) at long term operation. Zirconate pyrochlores of the large lanthanides((Gd → La){sub 2}Zr{sub 2}O{sub 7}) have been particularly attractive due to their higher temperature phase stability than that of the YSZ. Nonetheless, the issues related with the implementation of pyrochlores such as low fracture toughness and formation of deleterious interphases with thermally grown oxide (TGO, Al{sub 2}O{sub 3}) were reported. The implication was the requirement of an interlayer between the pyrochlores and TGO, which introduced double-layer systems to the TBC literature. Furthermore, processability issues of pyrochlores associated with the different evaporation rates of lanthanide oxides and zirconia resulting in unfavorable composition variations in the coatings were addressed in different studies. After all, although the material properties are available, there is a paucity of data in the literature concerning the properties of the coatings made of pyrochlores. From the processability point of view the most reported pyrochlore is La{sub 2}Zr{sub 2}O{sub 7}. Hence, the goal of this research was to investigate plasma-sprayed Gd{sub 2}Zr{sub 2}O{sub 7} (GZO) coatings and YSZ/GZO double-layer TBC systems. Three main topics were examined based on processing, performance and properties: (i) the plasma spray processing of the GZO and its impact on the microstructural and compositional properties of the GZO coatings; (ii) the cycling lifetime of the YSZ/GZO double-layer systems under thermal gradient at a surface temperature of 1400 C; (iii) the properties of the GZO and YSZ coatings such as

  20. In situ evaluation of DGT techniques for measurement of trace metals in estuarine waters: a comparison of four binding layers with open and restricted diffusive layers.

    Science.gov (United States)

    Shiva, Amir Houshang; Bennett, William W; Welsh, David T; Teasdale, Peter R

    2016-01-01

    Four different DGT binding layers were used to make selective measurements of trace metals in coastal waters within The Broadwater (Gold Coast, Queensland). Chelex and PAMPAA (polyacrylamide-polyacrylic acid) binding layers were used to measure cations (Cd, Co, Cu, Mn, Ni, Pb, Zn), and Metsorb was used to measure anions (Al, As, Mo, Sb, V, W). A mixed binding layer (MBL) containing both Chelex and Metsorb was used to measure each of the trace metals and determine diffusive boundary layer (DBL) thicknesses. DGT measurements that were not corrected for the DBL thickness (0.049-0.087) were underestimated by 70% on average. Good agreement was observed between DGT-MBL and DGT-Chelex for measurement of Cd, Co, Cu, Ni, Pb and Zn, and between DGT-MBL and DGT-Metsorb for As, Sb and V. DGT-MBL measured significantly higher concentrations for Mn (compared with DGT-Chelex) and Al (compared with DGT-Metsorb). DGT-Chelex measured only 6-8% of Al species measured by either DGT-MBL or DGT-Metsorb. DGT-PAMPAA measurements of Cu, Pb and Al were lower than those of either DGT-MBL or DGT-Chelex varying from 74-81% for Cu to 54-70% for Pb and 51-55% for anionic Al(OH)4(-), suggesting that this binding layer may make more selective measurements. All measured trace metal concentrations were well below ANZECC water quality guidelines, except for Cu which was 2 to 10 times higher than trigger values. Each of the DGT techniques was deployed using both open and restricted diffusive layers (ODL and RDL). Most trace metal measurements were not significantly different with ODL and RDL for all binding layers. However, concentrations of Cu (CRDL/CODL = 0.68-0.75) and Al (CRDL/CODL = 0.73-0.79) were significantly different with DGT-MBL, DGT-Chelex and DGT-Metsorb.

  1. Damage-free back channel wet-etch process in amorphous indium-zinc-oxide thin-film transistors using a carbon-nanofilm barrier layer.

    Science.gov (United States)

    Luo, Dongxiang; Zhao, Mingjie; Xu, Miao; Li, Min; Chen, Zikai; Wang, Lang; Zou, Jianhua; Tao, Hong; Wang, Lei; Peng, Junbiao

    2014-07-23

    Amorphous indium-zinc-oxide thin film transistors (IZO-TFTs) with damage-free back channel wet-etch (BCE) process were investigated. A carbon (C) nanofilm was inserted into the interface between IZO layer and source/drain (S/D) electrodes as a barrier layer. Transmittance electron microscope images revealed that the 3 nm-thick C nanofilm exhibited a good corrosion resistance to a commonly used H3PO4-based etchant and could be easily eliminated. The TFT device with a 3 nm-thick C barrier layer showed a saturated field effect mobility of 14.4 cm(2) V(-1) s(-1), a subthreshold swing of 0.21 V/decade, an on-to-off current ratio of 8.3 × 10(10), and a threshold voltage of 2.0 V. The favorable electrical performance of this kind of IZO-TFTs was due to the protection of the inserted C to IZO layer in the back-channel-etch process. Moreover, the low contact resistance of the devices was proved to be due to the graphitization of the C nanofilms after annealing. In addition, the hysteresis and thermal stress testing confirmed that the usage of C barrier nanofilms is an effective method to fabricate the damage-free BCE-type devices with high reliability.

  2. Highly Stable Operation of Lithium Metal Batteries Enabled by the Formation of a Transient High Concentration Electrolyte Layer

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Jianming; Yan, Pengfei; Mei, Donghai; Engelhard, Mark H.; Cartmell, Samuel S.; Polzin, Bryant; Wang, Chong M.; Zhang, Jiguang; Xu, Wu

    2016-02-08

    Lithium (Li) metal has been extensively investigated as an anode for rechargeable battery applications due to its ultrahigh specific capacity and the lowest redox potential. However, significant challenges including dendrite growth and low Coulombic efficiency are still hindering the practical applications of rechargeable Li metal batteries. Here, we demonstrate that long-term cycling of Li metal batteries can be realized by the formation of a transient high concentration electrolyte layer near the surface of Li metal anode during high rate discharge process. The highly concentrated Li+ ions in this transient layer will immediately solvate with the available solvent molecules and facilitate the formation of a stable and flexible SEI layer composed of a poly(ethylene carbonate) framework integrated with other organic/inorganic lithium salts. This SEI layer largely suppresses the corrosion of Li metal anode by free organic solvents and enables the long-term operation of Li metal batteries. The fundamental findings in this work provide a new direction for the development and operation of Li metal batteries that could be operated at high current densities for a wide range of applications.

  3. [ACTIVITY OF ANTIMICROBIAL NANOSTRUCTURED BARRIER LAYERS BASED ON POLYETHYLENETEREPHTHALATE IN RELATION TO CLINICAL STRAINES OF MICROORGANISMS FOR SICK PERSONS OF GASTROENTEROLOGICAL PROFILE].

    Science.gov (United States)

    Elinson, V M; Rusanova, E V; Vasilenko, I A; Lyamin, A N; Kostyuchenko, L N

    2015-01-01

    Homeostasis transgressions of enteral medium including disbiotic ones are often accompanying deseases of digestive tract. Espessially it touches upon sick persons connected with probe nourishing. One of the way for solving this problem is normalization of digestion microflore by means of wares with nanotechnological modifications of walls (probes, stomic tubes) which provide them antimicrobial properties and assist to normalization of digestive microbiotis and enteral homeostasis completely. The aim to study is research of antimicrobial activity of of nanostructured barrier layers based on polyethyleneterephthalate (PET) in relation to clinical straines of microorganisms. For barrier layer creation the approach on the base of methods of ion-plasma technology was used including ion-plasma treatment (nanostructuring) of the surface by ions noble and chemically active gases and following formation nanodimensional carbon films on the surface/ For the study of antimicrobial activity in relation to clinical straines of microorganisms we used the technique which allowed to establish the influence of parting degree of microorganisms suspension and time for samples exposing and microorganisms adsorbed on the surface. In experiment clinical straines obtained from different materials were used: Staphylococcus Hly+ and Calbicans--from pharyngeal mucosa, E. coli--from feces, K.pneumoniae--from urine. Sharing out and species identification of microorganisms were fulfilled according with legasy documents. In results of the study itwas obtained not only the presence of staticticaly confirmed antimicrobial activity of PET samples with nanostructured barrier layers in relation to different stimulators of nosocomical infections but also the influence of different factors connected with formation of nanostructured layers and consequently based with them physicochemical characteristics such as, in particular, surface energy, surface relief parameters, surface charg and others, as well

  4. Chemical resistance of thin film materials based on metal oxides grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sammelselg, Väino, E-mail: vaino.sammelselg@ut.ee [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia); Institute of Chemistry, University of Tartu, Ravila 14a, 50411 Tartu (Estonia); Netšipailo, Ivan; Aidla, Aleks; Tarre, Aivar; Aarik, Lauri; Asari, Jelena; Ritslaid, Peeter; Aarik, Jaan [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia)

    2013-09-02

    Etching rate of technologically important metal oxide thin films in hot sulphuric acid was investigated. The films of Al-, Ti-, Cr-, and Ta-oxides studied were grown by atomic layer deposition (ALD) method on silicon substrates from different precursors in large ranges of growth temperatures (80–900 °C) in order to reveal process parameters that allow deposition of coatings with higher chemical resistance. The results obtained demonstrate that application of processes that yield films with lower concentration of residual impurities as well as crystallization of films in thermal ALD processes leads to significant decrease of etching rate. Crystalline films of materials studied showed etching rates down to values of < 5 pm/s. - Highlights: • Etching of atomic layer deposited thin metal oxide films in hot H{sub 2}SO{sub 4} was studied. • Smallest etching rates of < 5 pm/s for TiO{sub 2}, Al{sub 2}O{sub 3}, and Cr{sub 2}O{sub 3} were reached. • Highest etching rate of 2.8 nm/s for Al{sub 2}O{sub 3} was occurred. • Remarkable differences in etching of non- and crystalline films were observed.

  5. Deposition of metal chalcogenide thin films by successive ionic layer adsorption and reaction (SILAR) method

    Indian Academy of Sciences (India)

    H M Pathan; C D Lokhande

    2004-04-01

    During last three decades, successive ionic layer adsorption and reaction (SILAR) method, has emerged as one of the solution methods to deposit a variety of compound materials in thin film form. The SILAR method is inexpensive, simple and convenient for large area deposition. A variety of substrates such as insulators, semiconductors, metals and temperature sensitive substrates (like polyester) can be used since the deposition is carried out at or near to room temperature. As a low temperature process, it also avoids oxidation and corrosion of the substrate. The prime requisite for obtaining good quality thin film is the optimization of preparative provisos viz. concentration of the precursors, nature of complexing agent, pH of the precursor solutions and adsorption, reaction and rinsing time durations etc. In the present review article, we have described in detail, successive ionic layer adsorption and reaction (SILAR) method of metal chalcogenide thin films. An extensive survey of thin film materials prepared during past years is made to demonstrate the versatility of SILAR method. Their preparative parameters and structural, optical, electrical properties etc are described. Theoretical background necessary for the SILAR method is also discussed.

  6. Long-range wetting transparency on top of layered metal-dielectric substrates

    Science.gov (United States)

    Noginov, M. A.; Barnakov, Yuri A.; Liberman, Vladimir; Prayakarao, Srujana; Bonner, Carl E.; Narimanov, Evgenii E.

    2016-06-01

    It has been recently shown that scores of physical and chemical phenomena (including spontaneous emission, scattering and Förster energy transfer) can be controlled by nonlocal dielectric environments provided by metamaterials with hyperbolic dispersion and simpler metal/dielectric structures. At this time, we have researched van der Waals interactions and experimentally studied wetting of several metallic, dielectric and composite multilayered substrates. We have found that the wetting angle of water on top of MgF2 is highly sensitive to the thickness of the MgF2 layer and the nature of the underlying substrate that could be positioned as far as ~100 nm beneath the water/MgF2 interface. We refer to this phenomenon as long range wetting transparency. The latter effect cannot be described in terms of the most basic model of dispersion van der Waals-London forces based on pair-wise summation of dipole-dipole interactions across an interface or a gap separating the two media. We infer that the experimentally observed gradual change of the wetting angle with increase of the thickness of the MgF2 layer can possibly be explained by the distance dependence of the Hamaker function (describing the strength of interaction), which originates from retardation of electromagnetic waves at the distances comparable to a wavelength.

  7. Transition Metal-Oxide Free Perovskite Solar Cells Enabled by a New Organic Charge Transport Layer.

    Science.gov (United States)

    Chang, Sehoon; Han, Ggoch Ddeul; Weis, Jonathan G; Park, Hyoungwon; Hentz, Olivia; Zhao, Zhibo; Swager, Timothy M; Gradečak, Silvija

    2016-04-06

    Various electron and hole transport layers have been used to develop high-efficiency perovskite solar cells. To achieve low-temperature solution processing of perovskite solar cells, organic n-type materials are employed to replace the metal oxide electron transport layer (ETL). Although PCBM (phenyl-C61-butyric acid methyl ester) has been widely used for this application, its morphological instability in films (i.e., aggregation) is detrimental. Herein, we demonstrate the synthesis of a new fullerene derivative (isobenzofulvene-C60-epoxide, IBF-Ep) that serves as an electron transporting material for methylammonium mixed lead halide-based perovskite (CH3NH3PbI(3-x)Cl(x)) solar cells, both in the normal and inverted device configurations. We demonstrate that IBF-Ep has superior morphological stability compared to the conventional acceptor, PCBM. IBF-Ep provides higher photovoltaic device performance as compared to PCBM (6.9% vs 2.5% in the normal and 9.0% vs 5.3% in the inverted device configuration). Moreover, IBF-Ep devices show superior tolerance to high humidity (90%) in air. By reaching power conversion efficiencies up to 9.0% for the inverted devices with IBF-Ep as the ETL, we demonstrate the potential of this new material as an alternative to metal oxides for perovskite solar cells processed in air.

  8. Effect of the Si-doped In0.49Ga0.51P barrier layer on the device performance of In0.4Ga0.6As MOSFETs grown on semi-insulating GaAs substrates

    Institute of Scientific and Technical Information of China (English)

    Chang Hu-Dong; Sun Bing; Xue Bai-Qing; Liu Gui-Ming; Zhao Wei; Wang Sheng-Kai; Liu Hong-Gang

    2013-01-01

    In0.4Ga0.6As channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with and without an Si-doped In0.49Ga0.51P barrier layer grown on semi-insulating GaAs substrates have been investigated for the first time.Compared with the In0.4Ga0.6As MOSFETs without an In0.49Ga0.51P barrier layer,In0.4Ga0.6As MOSFETs with an In0.49Ga0.51P barrier layer show higher drive current,higher transconductance,lower gate leakage current,lower subthreshold swing,and higher effective channel mobility.These In0.4Ga0.6As MOSFETs (gate length 2 μm) with an In0.49Ga0.s1P barrier layer exhibit a high drive current of 117 mA/mm,a high transconductance of 71.9 mS/mm,and a maximum effective channel mobility of 1266 cm2/(V·s).

  9. Al capping layers for nondestructive x-ray photoelectron spectroscopy analyses of transition-metal nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Greczynski, Grzegorz, E-mail: grzgr@ifm.liu.se; Hultman, Lars [Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-581 83 Linköping (Sweden); Petrov, Ivan [Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-581 83 Linköping, Sweden and Materials Science Department and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801 (United States); Greene, J. E. [Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-581 83 Linköping (Sweden); Materials Science Department and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801(United States); Department of Physics, University of Illinois, Urbana, Illinois 61801 (United States)

    2015-09-15

    X-ray photoelectron spectroscopy (XPS) compositional analyses of materials that have been air exposed typically require ion etching in order to remove contaminated surface layers. However, the etching step can lead to changes in sample surface and near-surface compositions due to preferential elemental sputter ejection and forward recoil implantation; this is a particular problem for metal/gas compounds and alloys such as nitrides and oxides. Here, the authors use TiN as a model system and compare XPS analysis results from three sets of polycrystalline TiN/Si(001) films deposited by reactive magnetron sputtering in a separate vacuum chamber. The films are either (1) air-exposed for ≤10 min prior to insertion into the ultrahigh-vacuum (UHV) XPS system; (2) air-exposed and subject to ion etching, using different ion energies and beam incidence angles, in the XPS chamber prior to analysis; or (3) Al-capped in-situ in the deposition system prior to air-exposure and loading into the XPS instrument. The authors show that thin, 1.5–6.0 nm, Al capping layers provide effective barriers to oxidation and contamination of TiN surfaces, thus allowing nondestructive acquisition of high-resolution core-level spectra representative of clean samples, and, hence, correct bonding assignments. The Ti 2p and N 1s satellite features, which are sensitive to ion bombardment, exhibit high intensities comparable to those obtained from single-crystal TiN/MgO(001) films grown and analyzed in-situ in a UHV XPS system and there is no indication of Al/TiN interfacial reactions. XPS-determined N/Ti concentrations acquired from Al/TiN samples agree very well with Rutherford backscattering and elastic recoil analysis results while ion-etched air-exposed samples exhibit strong N loss due to preferential resputtering. The intensities and shapes of the Ti 2p and N 1s core level signals from Al/TiN/Si(001) samples do not change following long-term (up to 70 days) exposure to ambient conditions

  10. Heavy metals in the organic soil layer of beech forests in Serbia

    Directory of Open Access Journals (Sweden)

    Kadović Ratko

    2005-01-01

    Full Text Available During the last decades, forest ecosystems have been strongly exposed to the effect of different harmful pollutants, especially from the atmosphere. Harmful substances from the air, in addition to the direct effect on forest trees, also deposit in the soil, and have an adverse effect on soil chemistry and pedogenetic processes. The results of previous studies in Serbia (Kadović, Knežević, 2002, 2004 show some specificities regarding the accumulation and migration of heavy metals in the soil. The highest concentrations were found in the layers of forest litter and in the surface organo-mineral horizons. This paper presents the results of the study of heavy metal contents (Zn, Mn, Cu, Fe, Cd, Pb, Ni and Cr in the organic horizon (forest litter of beech forests in Serbia. The study of the heavy metal content in the organic horizon (forest litter is very significant primarily in the aim of monitoring the trend of their migration through the soil profile and the effect on the soil properties and genesis. The soil quality in beech forests in Serbia was assessed within the Project ICP Forest, Level I, by the methodology UN/ECE-EC, 2000.

  11. Dependence of bonding interactions in Layered Double Hydroxides on metal cation chemistry

    Science.gov (United States)

    Shamim, Mostofa; Dana, Kausik

    2016-12-01

    The evolution of various Infrared bands of Layered Double Hydroxides (LDH) with variable Zn:Al ratio was analyzed to correlate it with the changes in octahedral metal cation chemistry, interlayer carbonate anion and hydroxyl content of LDH. The synthesized phase-pure LDHs were crystallized as hexagonal 2H polytype with a Manasseite structure. The broad and asymmetric hydroxyl stretching region (2400-4000 cm-1) can be deconvoluted into four different bands. With increase in Zn2+:Al3+ metal ratio, the peak position of stretching frequencies of Al3+sbnd OH and carbonate-bridged hydroxyl (water) decrease almost linearly. Individual band's peak position and area under the curve have been successfully correlated with the carbonate and hydroxyl content of LDH. Due to lowering of symmetry of the carbonate anion, the IR-inactive peak νCsbnd O, symm at 1064 cm-1 becomes IR active. The peak position of metal-oxygen bands and carbonate bending modes are practically unaffected by the Zn2+:Al3+ ratio but the area under the individual M-O bands shows a direct correlation.

  12. The consequences of air flow on the distribution of aqueous species during dielectric barrier discharge treatment of thin water layers

    Science.gov (United States)

    Tian, Wei; Lietz, Amanda M.; Kushner, Mark J.

    2016-10-01

    The desired outcomes of wet tissue treatment by dielectric barrier discharges (DBDs) strongly depend on the integrated fluences of reactive species incident onto the tissue, which are determined by power, frequency and treatment time. The reactivity produced by such plasmas is often expected to be proportional to treatment time due to the accumulation of radicals in the liquid over the tissue. However, one of the typically uncontrolled parameters in DBD treatment of liquids and tissue is gas flow, which could affect the delivery of plasma produced radicals to the tissue. Gas flow can redistribute long-lived, plasma produced gas phase species prior to solvating in the liquid, while not greatly affecting the solvation of short-lived species. Gas flow can therefore potentially be a control mechanism for tailoring the fluences of reactive species to the tissue. In this paper, we report on a computational investigation of the consequences of gas flow on treatment of liquid layers covering tissue by atmospheric DBDs by up to 100 pulses. We found that gas flow (through residence time of the gas) can control the production of gas phase species requiring many collisions to form, such as reactive nitrogen species (RNS). The resulting solvation of the RNS in turn controls the production of aqueous species such as \\text{NO}\\text{3aq}- and \\text{ONOO}\\text{aq}- (aq denotes an aqueous species). With the exception of O3 and O3aq, reactive oxygen species (ROS) are less sensitive to gas flow, and so OHaq and H2O2aq, are determined primarily by discharge properties.

  13. Effect of process parameters on hardness, temperature profile and solidification of different layers processed by direct metal laser sintering (DMLS)

    Science.gov (United States)

    Ahmed, Sazzad Hossain; Mian, Ahsan; Srinivasan, Raghavan

    2016-07-01

    In DMLS process objects are fabricated layer by layer from powdered material by melting induced by a controlled laser beam. Metallic powder melts and solidifies to form a single layer. Solidification map during layer formation is an important route to characterize micro-structure and grain morphology of sintered layer. Generally, solidification leads to columnar, equiaxed or mixture of these two types grain morphology depending on solidification rate and thermal gradient. Eutectic or dendritic structure can be formed in fully equiaxed zone. This dendritic growth has a large effect on material properties. Smaller dendrites generally increase ductility of the layer. Thus, materials can be designed by creating desired grain morphology in certain regions using DMLS process. To accomplish this, hardness, temperature distribution, thermal gradient and solidification cooling rate in processed layers will be studied under change of process variables by using finite element analysis, with specific application to Ti-6Al-4V.

  14. Effect of process parameters on hardness, temperature profile and solidification of different layers processed by direct metal laser sintering (DMLS)

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Sazzad Hossain; Mian, Ahsan, E-mail: ahsan.mian@wright.edu; Srinivasan, Raghavan [Department of Mechanical and Materials Engineering, Wright State University, Dayton, Ohio 45435 (United States)

    2016-07-12

    In DMLS process objects are fabricated layer by layer from powdered material by melting induced by a controlled laser beam. Metallic powder melts and solidifies to form a single layer. Solidification map during layer formation is an important route to characterize micro-structure and grain morphology of sintered layer. Generally, solidification leads to columnar, equiaxed or mixture of these two types grain morphology depending on solidification rate and thermal gradient. Eutectic or dendritic structure can be formed in fully equiaxed zone. This dendritic growth has a large effect on material properties. Smaller dendrites generally increase ductility of the layer. Thus, materials can be designed by creating desired grain morphology in certain regions using DMLS process. To accomplish this, hardness, temperature distribution, thermal gradient and solidification cooling rate in processed layers will be studied under change of process variables by using finite element analysis, with specific application to Ti-6Al-4V.

  15. Layered Post-Transition-Metal Dichalcogenides (X-M-M-X) and Their Properties.

    Science.gov (United States)

    Luxa, Jan; Wang, Yong; Sofer, Zdenek; Pumera, Martin

    2016-12-23

    A(III) B(VI) chalcogenides are an interesting group of layered semiconductors with several attractive properties, such as tunable band gaps and the formation of solid solutions. Unlike the typically sandwiched structure of transition-metal dichalcogenides, A(III) B(VI) layered chalcogenides with hexagonal symmetry are stacked through the X-M-M-X motif, in which M is gallium and indium, and X is sulfur, selenium, and tellurium. In view of the inadequate study of the electrochemical properties and great interest in layered materials towards energy-related research, herein the inherent electrochemistry of GaS, GaSe, GaTe, and InSe has been studied, as well as the exploration of their potential as hydrogen evolution reaction (HER) electrocatalysts. All four materials show redox peaks during cyclic voltammetry measurements. Furthermore, insights into catalysis of the HER are provided; these indicate the conductivity and number of active sites of the materials. All of these findings have important implications on their possible applications.

  16. Artificial geochemical barriers for additional recovery of non-ferrous metals and reduction of ecological hazard from the mining industry waste.

    Science.gov (United States)

    Chanturiya, Valentine; Masloboev, Vladimir; Makarov, Dmitriy; Mazukhina, Svetlana; Nesterov, Dmitriy; Men'shikov, Yuriy

    2011-01-01

    Laboratory tests and physical-chemical modeling have determined that mixtures of activated silica and carbonatite, serpophite and carbonatite show considerable promise for developing artificial geochemical barriers. The obtained average contents of nickel and copper deposited on geochemical barriers in the formed mining induced ores are acceptable for their subsequent cost efficient processing using either pyro- or hydrometallurgy methods. Some tests of geochemical barriers have been carried out, involving the use of polluted water in the impact zone of the "Kol'skaya GMK" JSC. A possibility of water purification from heavy metals down to the MAC level for fishery water bodies has been displayed.

  17. Design and numerical simulation of a silicon-based linear polarizer with double-layered metallic nano-gratings

    Science.gov (United States)

    Lin, Yu; Hu, Jingpei; Wang, Chinhua

    2016-10-01

    With the increasing demand for linearly polarized elements with high performance in many fields and applications, design and fabrication of sub-wavelength metallic linear polarizer have made tremendous progress in recent years. In this paper, we proposed a novel structure of a silicon-based linear polarizer working in the infrared (3-5μm) waveband with a double-layered metallic grating structure. A two-layer metallic grating with a transition layer of low refractive index is fabricated on a silicon substrate. In contrast to those conventional single layer metallic polarizing grating, the multilayer polarizing structure has the advantages of easy fabrication and high performance. Numerical simulation results show that an extinction ratio of linear polarization can be up to 58.5dB and the TM-polarized light transmission is greater than 90%. The behaviors and advantages of the proposed multilayer polarizer are compared with that of a traditional single-layer metallic grating. The proposed silicon-based linear polarizer will have great potential applications in real-time polarization imaging with high extinction ratio and high transmission.

  18. Quantum cascade laser-based measurement of metal alkylamide density during atomic layer deposition.

    Science.gov (United States)

    Maslar, James E; Kimes, William A; Sperling, Brent A

    2012-03-01

    An in situ gas-phase diagnostic for the metal alkylamide compound tetrakis(ethylmethylamido) hafnium (TEMAH), Hf[N(C(2)H(5))(CH(3))](4), was demonstrated. This diagnostic is based on direct absorption measurement of TEMAH vapor using an external cavity quantum cascade laser emitting at 979 cm(-1), coinciding with the most intense TEMAH absorption in the mid-infrared spectral region, and employing 50 kHz amplitude modulation with synchronous detection. Measurements were performed in a single-pass configuration in a research-grade atomic layer deposition (ALD) chamber. To examine the detection limit of this technique for use as a TEMAH delivery monitor, this technique was demonstrated in the absence of any other deposition reactants or products, and to examine the selectivity of this technique in the presence of deposition products that potentially interfere with detection of TEMAH vapor, it was demonstrated during ALD of hafnium oxide using TEMAH and water. This technique successfully detected TEMAH at molecular densities present during simulated industrial ALD conditions. During hafnium oxide ALD using TEMAH and water, absorbance from gas-phase reaction products did not interfere with TEMAH measurements while absorption by reaction products deposited on the optical windows did interfere, although interfering absorption by deposited reaction products corresponded to only ≈4% of the total derived TEMAH density. With short measurement times and appropriate signal averaging, estimated TEMAH minimum detectable densities as low as ≈2 × 10(12) molecules/cm(3) could be obtained. While this technique was demonstrated specifically for TEMAH delivery and hafnium oxide ALD using TEMAH and water, it should be readily applicable to other metal alkylamide compounds and associated metal oxide and nitride deposition chemistries, assuming similar metal alkylamide molar absorptivity and molecular density in the measurement chamber.

  19. The mucus layer is critical in protecting against ischemia/reperfusion-mediated gut injury and in the restitution of gut barrier function

    Science.gov (United States)

    Qin, Xiaofa; Sheth, Sharvil U.; Sharpe, Susan M.; Dong, Wei; Lu, Qi; Xu, Dazhong; Deitch, Edwin A.

    2011-01-01

    It is well documented that the gut injury plays a critical role in the development of systemic inflammation and distant organ injury in conditions associated with splanchnic ischemia. Consequently understanding the mechanisms leading to gut injury is important. In this context, recent work suggests a protective role for the intestinal mucus layer and an injury-inducing role for luminal pancreatic proteases. Thus, we explored the role of the mucus layer in gut barrier function by observing how the removal of the mucus layer affects ischemia/reperfusion-mediated gut injury in rats as well as the potential role of luminal pancreatic proteases in the pathogenesis of gut injury. Ischemia was induced by the ligation of blood vessels to segments of the ileum for 45 min, followed by up to three hours of reperfusion. The ileal segments were divided into 5 groups. These included a non-ischemic control, ischemic segments exposed to saline, the mucolytic N-acetylcholine (NAC), pancreatic proteases or NAC plus pancreatic proteases. Changes in gut barrier function were assessed by the permeation of fluorescein isothiocyanate dextran (MW 4000 Da; FD4) in ileal everted sacs. Gut injury was measured morphologically and by the luminal content of protein, DNA and hemoglobin. The mucus layer was assessed functionally by measuring its hydrophobicity and morphologically. Gut barrier function was promptly and effectively re-established during reperfusion, which was accompanied by the restoration of the mucus layer. In contrast, treatment of the gut with the mucolytic NAC for 10 min during ischemia resulted in a failure of mucus restitution and further increases in gut permeability and injury. The presence of digestive proteases by themselves did not exacerbate gut injury but in combination with NAC, they caused an even greater increase in gut injury and permeability. These results suggest that the mucus layer not only serves as a barrier between the luminal contents and gut surface

  20. Miniaturized metal (metal alloy)/ PdO.sub.x/SiC hydrogen and hydrocarbon gas sensors

    Science.gov (United States)

    Hunter, Gary W. (Inventor); Xu, Jennifer C. (Inventor); Lukco, Dorothy (Inventor)

    2011-01-01

    A miniaturized Schottky diode hydrogen and hydrocarbon sensor and the method of making same is disclosed and claimed. The sensor comprises a catalytic metal layer, such as palladium, a silicon carbide substrate layer and a thin barrier layer in between the catalytic and substrate layers made of palladium oxide (PdO.sub.x ). This highly stable device provides sensitive gas detection at temperatures ranging from at least 450 to 600.degree. C. The barrier layer prevents reactions between the catalytic metal layer and the substrate layer. Conventional semiconductor fabrication techniques are used to fabricate the small-sized sensors. The use of a thicker palladium oxide barrier layer for other semiconductor structures such as a capacitor and transistor structures is also disclosed.