Search

The mechanisms governing the tensile behavior of TiO2nanowires were studied by molecular dynamics simulations. Nanowires below a threshold diameter of about 10 Å transformed into a completely disordered structure after thermodynamic equilibration, whereas thicker nanowires retained their crystalline core. Initial elastic tensile deformation was effected by the reconfiguration of surface atoms while larger elongations resulted in continuous cycles of Ti−O bond straightening, bond breakage, inner atomic distortion, and necking until rupture. Nanowires have much better mechanical properties than bulk TiO2. Nanowires below the threshold diameter exhibit extraordinarily high stiffness and toughness and are more sensitive to strain rate. [ABSTRACT FROM AUTHOR]

An effective surface-enhanced Raman scattering (SERS) template based on a 3D hybrid Ag nanocluster (NC)-decorated ZnO nanowire array was fabricated through a simple process of depositing Ag NCs on ZnO nanowire arrays. The effects of particle size and excitation energy on the Raman scattering in these hybrid systems have been investigated using rhodamine 6G as a standard analyte. The results indicate that the hybrid nanosystem with 150 nm Ag NCs produces a larger SERS enhancement factor of 3.2 x 108, which is much higher than that of 10 nm Ag NCs (6.0 x 106) under 532 nm excitation energy. The hybrid nanowire arrays were further applied to obtain SERS spectra of the two-photon absorption (TPA) chromophore T7. Finite-difference time-domain simulations reveal the presence of an enhanced field associated with inter-wire plasmon coupling of the 150 nm Ag NCs on adjacent ZnO nanowires; such a field was absent in the case of the 10 nm Ag NC-coated ZnO nanowire. Such hybrid nanosystems could be used as SERS substrates more effectively than assembled Ag NC film due to the enhanced light-scattering local field and the inter-wire plasmon-enhanced electromagnetic field. [ABSTRACT FROM AUTHOR]

Patterned gallium nitride nanowires have been grown on n-Si(100) substrates by pulsed laser ablation. The nanowires are patterned using a physical mask, resulting in regions of nanowire growth of different density. These gallium nitride nanowires are single-crystalline with hexagonal wurzite structures. The electrical transport measurements of individual GaN nanowires show near-linear current-voltage characteristics. The estimated electron densities of these individual GaN nanowires range from 1.8-6.8 x 1018 cm[?]3. The field emission characteristics of these patterned gallium nitride nanowires show a turn-on field of 8.4 V um[?]1 to achieve a current density of 0.01 mA cm[?]2 and an enhanced field emission current density as high as 0.96 mA cm[?]2 at an applied field of 10.8 V um[?]1. The field emission results indicate that, besides crystalline quality as well as the low electron affinity of gallium nitride, density difference in the nanowires growth greatly enhances their field emission properties by reducing the screening between nanowires. [ABSTRACT FROM AUTHOR]

Patterned micropads made of metallic nanowires, 50 µm in diameter, are fabricated on a silicon substrate. An aluminium film patterned with SiO2is anodized to fabricate a patterned nanoporous alumina (PNA) template in which metallic nanowires are electrodeposited. SiO2that is deposited using the plasma-enhanced chemical vapour deposition process is demonstrated to be an effective barrier to anodization for the fabrication of high aspect ratio PNA templates. Current-voltage characteristics of an individual copper nanowire micropad display ohmic behaviour with a low resistance value of 5.5 m?. The nanowires are able to withstand the solder reflow process. Cu nanowire/Sn solder reflow reaction leads to Cu6Sn5intermetallic formation. These micropads made of metallic nanowires have the potential for application as chip to substrate interconnects. Nanostructure synthesis is carried out using standard microelectronics fabrication techniques that would enable easy integration of such nanodevices into routine silicon manufacturing. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations of ZnO nanowires under tensile loading were performed and compared with simulations of TiO2wires to present size-dependent mechanical properties and super ductility of metal oxide wires. It is shown that while large surface-to-volume ratio is responsible for their size effects, ZnO and TiO2wires displayed opposite trends. Although the stiffness of both wires converged monotonically to their bulk stiffness values as diameter increases, bulk stiffness represented the upper bound for ZnO nanowires as opposed to the lower bound for TiO2wires. ZnO nanowires relaxed to either completely amorphous or completely crystalline states depending on wire thickness, whereas a thin amorphous shell is always present in TiO2nanowires. It was also found that when crystalline ZnO nanowires are stretched, necking initiated at localized amorphous regions to eventually form single-atom chains which can sustain strains above 100%. Such large elongations are not observed in TiO2nanowires. Using the analogy of a clothesline, an explanation is offered for the necessary conditions leading to super ductility. [ABSTRACT FROM AUTHOR]