Browsing by Subject "nanowire"

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    Electroless synthesis of 3nm wide alloy nanowires inside Tobacco mosaic virus
    (2012) Balci, S.; Hahn, K.; Kopold P.; Kadri, A.; Wege, C.; Kern, K.; Bittner, A.M.
    We show that 3nm wide cobaltiron alloy nanowires can be synthesized by simple wet chemical electroless deposition inside tubular Tobacco mosaic virus particles. The method is based on adsorption of Pd(II) ions, formation of a Pd catalyst, and autocatalytic deposition of the alloy from dissolved metal salts, reduced by a borane compound. Extensive energy-filtering TEM investigations at the nanoscale revealed that the synthesized wires are alloys of Co, Fe, and Ni. We confirmed by high-resolution TEM that our alloy nanowires are at least partially crystalline, which is compatible with typical Co-rich alloys. Ni traces bestow higher stability, presumably against corrosion, as also known from bulk CoFe. Alloy nanowires, as small as the ones presented here, might be used for a variety of applications including high density data storage, imaging, sensing, and even drug delivery. © 2012 IOP Publishing Ltd.
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    Electronic and atomic processes in nanowires
    (1996) Mehrez, Hatem
    The variation of conductance of a nanowire which is pulled between two metal electrodes has been the subject of dispute. Recent experimental set-ups using a combination of STM and AFM show that changes in conductivity are closely related with modification of atomic structure. In this thesis electron transport in the nanoindentation and in the connective neck are studied and features of measured conductance are analyzed. Molecular Dynamics simulations of nanowires under tensile stress are carried out to reveal the mechanical properties in nanowires in the course of stretching. A novel type of plcistic deformation, which leads to the formation of bundles with “giant” yield strength is found. An extensive analysis on how abrupt changes in the conductance and the last plateau before the break are related with “quantization phenomena” and atomic structure rearrangements in the neck. By using ab-initio self-consistent field pseudopotential calculations we also investigated electron properties of nanowires and atomic chains and predicted the large yield strength observed in the center of connective neck.
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    Size and composition modulated superlattices of silicon based nanowires
    (2008) Cahangirov, Seymur
    Mechanical properties, atomic and energy band structures of bare and hydrogen passivated SinGen nanowire superlattices have been investigated by using firstprinciples pseudopotential plane wave method. Undoped, tetrahedral Si and Ge nanowire segments join pseudomorphically and can form superlattice with atomically sharp interface. Upon heterostructure formation, superlattice electronic states form subbands in momentum space. Band lineups of Si and Ge zones result in multiple quantum wells, where specific states at the band edges and in band continua are confined. The electronic structure of the nanowire superlattice depends on the length and cross section geometry of constituent Si and Ge segments. Also we showed that hydrogen saturated silicon nanowires of different diameters having different band gaps can form stable junctions. Superlattices formed by the periodically repeated junctions of silicon nanowire segments having different lengths and diameters exhibit electronic states which can be confined in regions having either narrow or wide parts of superlattice. A point defect, such as a missing atom or substitutional impurities with localized states near band edges can make modulation doping possible. Since bare Si and Ge nanowires are metallic and the band gaps of hydrogenated ones varies with the diameter, these superlattices offer numerous options for multiple quantum well devices with their leads made from the constituent metallic nanowires. Finally, we have considered the junction between bare and hydrogenated nanowires to realise metalsemiconductor heterostructure. We have treated this heterostructure within the supercell geometry and deduced the formation of Schottky barrier. We have shown that Si and Ge nanowires can bring about a novel concept in nanocircuit, where interconnects, devices etc are produced on a single rode.