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Metal Contacts (metal + contact)
Selected AbstractsChemInform Abstract: Two New Examples of very Short Thallium,Transition Metal Contacts: Tl3Ag3Sb2S6 and Tl3Ag3As2S6.CHEMINFORM, Issue 34 2008Ljiljana Karanovic Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Chemical Interactions at Metal/Molecule Interfaces in Molecular Junctions,A Pathway Towards Molecular Recognition,ADVANCED MATERIALS, Issue 3 2009Mila Manolova A 4-aminothiophenol self-assembled monolayer (see image) is prepared on top of a Au(111) crystal, which is subsequently metallized by a nearly closed Pd overlayer of monoatomic height. Analysis of its structural setup and electronic properties reveals that the monolayer consists of a minimum of two molecular layers, and strong chemical interactions between the metal overlayer and the amino groups are found to play a decisive role in determining the overall electronic, and thus the transport properties, of the layer/metal contact. [source] Wear mechanisms in metal-on-metal bearings: The importance of tribochemical reaction layersJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2010Markus A. Wimmer Abstract Metal-on-metal (MoM) bearings are at the forefront in hip resurfacing arthroplasty. Because of their good wear characteristics and design flexibility, MoM bearings are gaining wider acceptance with market share reaching nearly 10% worldwide. However, concerns remain regarding potential detrimental effects of metal particulates and ion release. Growing evidence is emerging that the local cell response is related to the amount of debris generated by these bearing couples. Thus, an urgent clinical need exists to delineate the mechanisms of debris generation to further reduce wear and its adverse effects. In this study, we investigated the microstructural and chemical composition of the tribochemical reaction layers forming at the contacting surfaces of metallic bearings during sliding motion. Using X-ray photoelectron spectroscopy and transmission electron microscopy with coupled energy dispersive X-ray and electron energy loss spectroscopy, we found that the tribolayers are nanocrystalline in structure, and that they incorporate organic material stemming from the synovial fluid. This process, which has been termed "mechanical mixing," changes the bearing surface of the uppermost 50 to 200 nm from pure metallic to an organic composite material. It hinders direct metal contact (thus preventing adhesion) and limits wear. This novel finding of a mechanically mixed zone of nanocrystalline metal and organic constituents provides the basis for understanding particle release and may help in identifying new strategies to reduce MoM wear. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:436,443, 2010 [source] Influence of top layer geometries on the electronic properties of pentacene and diindenoperylene thin filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2008M. Scharnberg Abstract Top layers have a pronounced influence on the electronic properties of molecular organic thin films. Here, we report about the changes induced by metallic and polymeric top layers and contacts. As test structures, model systems of diindenoperylene and pentacene crystalline molecular organic thin films are used. A very sensitive radiotracer technique is introduced to study the details of metal penetration during top contact formation. The influence of temperature, evaporation time, adhesion promoter and grain size of the organic film were examined. The electric currents passing through metal top contacts were found to vary by more than a factor of three, depending on the preparation conditions of the metal contact. Furthermore, the series resistance of chemically identical contacts that only differed in the morphology of the interface were found to show pronounced asymmetric conductivity behaviour. We also show that with the help of electret top layers, based on the Teflon-AF fluropolymer, the threshold voltage of an organic field effect transistor can be tuned by several volts. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] M -plane InGaN/GaN light emitting diodes fabricated by MOCVD regrowth on c -plane patterned templatesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Christopher A. Schaake Abstract In this work we demonstrate a light emitting diode (LED) with m -plane quantum wells fabricated on a (000) template. N-polar, n-type GaN was grown by MOCVD on vicinal sapphire substrates. Stripes, measuring 500 nm wide, 500 nm tall and spaced 2 ,m apart, were etched parallel to the ,110, direction leading to sidewalls that are approximately {100}. Sputtered AlN was used as a regrowth mask on the c -plane surfaces. An active region consisting of 5 InGaN quantum wells and GaN barriers followed by p-type was grown. The regrowth occurred mostly on the exposed m -plane sidewalls, leading to lateral growth in the ,100, direction. The LED was processed using conventional methods. A thick metal contact was used to connect the p-regions together. Current vs. voltage measurements showed good rectifying behavior with a turn on of about 6 volts. On-wafer electroluminescence measurements revealed a peak wavelength of 422 nm. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis, Structure and Magnetic Behaviour of Manganese(II) Selenolate Complexes ,1[Mn(SePh)2], [Mn(SePh)2(bipy)2] and [Mn(SePh)2(phen)2] (bipy = bipyridyl, phen = phenanthroline)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 30 2007Andreas Eichhöfer Abstract The manganese selenolate complex ,1[Mn(SePh)2] has been prepared by reaction of Mn(OOCCH3)2 with 2 equiv.PhSeSiMe3 in thf. In the crystal structure, the compound forms one-dimensional chains, and the bridging selenolate ligands result in relatively short metal,metal contacts of about 3 Å. Reaction with two equivalents of the Lewis bases 2,2,-bipyridine and 1,10-phenanthroline yielded the monomeric octahedral complexes [Mn(SePh)2(2,2,-bipy)2] and [Mn(SePh)2(1,10-phen)2], respectively. The magnetic and optical properties of these complexes have been investigated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Electronic Contact Deposition onto Organic Molecular Monolayers: Can We Detect Metal Penetration?ADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Hagay Shpaisman Abstract Using a semiconductor as the substrate to a molecular organic layer, penetration of metal contacts can be clearly identified by the study of electronic charge transport through the layer. A series of monolayers of saturated hydrocarbon molecules with varying lengths is assembled on Si or GaAs and the junctions resulting after further electronic contact is made by liquid Hg, indirect metal evaporation, and a "ready-made" metal pad are measured. In contrast to tunneling characteristics, which are ambiguous regarding contact penetration, the semiconductor surface barrier is very sensitive to any direct contact with a metal. With the organic monolayer intact, a metal,insulator,semiconductor (MIS) structure results. If metal penetrated the monolayer, the junction behaves as a metal,semiconductor (MS) structure. By comparing a molecule-free interface (MS junction) with a molecularly modified one (presumably MIS), possible metal penetration is identified. The major indicators are the semiconductor electronic transport barrier height, extracted from the junction transport characteristics, and the photovoltage. The approach does not require a series of different monolayers and data analysis is quite straightforward, helping to identify non-invasive ways to make electronic contact to soft matter. [source] Investigation of oxygen incorporation in AlGaN/GaN heterostructuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Ho Won Jang Abstract The unintentional doping of oxygen atoms in undoped AlGaN layers was demonstrated by scanning photoemission microscopy (SPEM) using synchrotron radiation. In-situ annealing at 1000 °C and subsequent SPEM imaging showed that the oxygen concentration in AlGaN was much higher than in GaN. Space-resolved photoemission spectra of O 1s, Ga 3d and Al 2p core levels showed that the predominant oxygen incorporation in AlGaN resulted from the formation of Al,O bonds due to the high reactivity of Al with oxygen. The degenerated AlGaN layer produced by the oxygen donors caused the tunneling-assisted transport of electrons at the interface of the AlGaN with metal contacts and an increase in the sheet carrier concentration at the AlGaN/GaN heterointerface. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Screen-print selective diffusions for high-efficiency industrial silicon solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2008Matthew Edwards Abstract Screen-print diffusion pastes present an industrially applicable alternative to conventional techniques of dopant deposition. Several commercially available screen-print dopant pastes are assessed for their suitability in forming heavy selective diffusions for use under metal contacts in silicon solar cells. Pastes are assessed in terms of their ease of application, their ability to form heavy diffusions with low sheet resistances, and their ability to maintain high post-diffusion wafer lifetimes. Potential for the use of dopant pastes in high-efficiency solar cell devices is investigated using photoconductance (PC) measurements and photoluminescence (PL) images. It is found that under certain conditions, screen-print dopant pastes, particularly phosphorus paste, have potential to form effective selective diffusions without significantly compromising performance in high-efficiency solar cells. Copyright © 2007 John Wiley & Sons, Ltd. [source] Experimental evidence of parasitic shunting in silicon nitride rear surface passivated solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2002Stefan Dauwe Many solar cells incorporating SiNx films as a rear surface passivation scheme have not reached the same high level of cell performance as solar cells incorporating high-temperature-grown silicon dioxide films as a rear surface passivation. In this paper, it is shown by direct comparison of solar cells incorporating the two rear surface passivation schemes, that the performance loss is mainly due to a lower short-circuit current while the open-circuit voltage is equally high. With a solar cell test structure that features a separation of the rear metal contacts from the passivating SiNx films, the loss in short-circuit current can be reduced drastically. Besides a lower short- circuit current, dark I,V curves of SiNx rear surface passivated solar cells exhibit distinct shoulders. The results are explained by parasitic shunting of the induced floating junction (FJ) underneath the SiNx films with the rear metal contacts. The floating junction is caused by the high density of fixed positive charges in the SiNx films. Other two-dimensional effects arising from the injection level dependent SRV of the Si/SiNx interfaces are discussed as well, but, are found to be of minor importance. Pinholes in the SiNx films and optical effects due to a different internal rear surface reflectance can be excluded as a major cause for the performance loss of the SiNx rear surface passivated cells. Copyright © 2002 John Wiley & Sons, Ltd. [source] Doping of the Metal Oxide Nanostructure and its Influence in Organic ElectronicsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Mi-Hyae Park Abstract Synthesizing metal oxides through the sol,gel process provides a convenient way for forming a nanostructured layer in wide band gap semiconductors. In this paper, a unique method of introducing dopants into the metal oxide semiconductor is presented. The doped TiO2 is prepared by adding a Cs2CO3 solution to a nanocrystalline TiO2 solution that is synthesized via a non-hydrolytic sol,gel process. The properties of the TiO2:Cs layer are investigated and the results show stable nanostructure morphology. In addition to providing morphological stability, Cs in TiO2 also gives rise to a more desirable work function for charge transport in organic electronics. Polymer solar cells based on the poly(3-hexylthiophene) (P3HT): methanofullerene (PC70BM) system with the addition of a TiO2:Cs interfacial layer exhibit excellent characteristics with a power conversion efficiency of up to 4.2%. The improved device performance is attributed to an improved polymer/metal contact, more efficient electron extraction, and better hole blocking properties. The effectiveness of this unique functionality also extends to polymer light emitting devices, where a lower driving voltage, improved efficiency, and extended lifetime are demonstrated. [source] | ||||||||||||||||