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Stuttgart Mühlhausen, Germany

Alber I.,Helmholtz Center for Heavy Ion Research | Sigle W.,Stuttgart Center for Electronic Microscopy | Muller S.,Helmholtz Center for Heavy Ion Research | Neumann R.,Helmholtz Center for Heavy Ion Research | And 5 more authors.
ACS Nano | Year: 2011

We study the transversal and longitudinal localized surface plasmon resonances in single nanowires and nanowire dimers excited by the fast traveling electron beam in a transmission electron microscope equipped with high-resolution electron energy-loss spectroscopy. Bright and dark longitudinal modes up to the fifth order are resolved on individual metallic nanowires. On nanowire dimers, mode splitting into bonding and antibonding is measured up to the third order for several dimers with various aspect ratio and controlled gap size. We observe that the electric field maxima of the bonding modes are shifted toward the gap, while the electric field maxima of the antibonding modes are shifted toward the dimer ends. Finally, we observe that the transversal mode is not detected in the region of the dimer gap and decays away from the rod more rapidly than the longitudinal modes. © 2011 American Chemical Society. Source


Alber I.,Helmholtz Center for Heavy Ion Research | Sigle W.,Stuttgart Center for Electronic Microscopy | Demming-Janssen F.,CST Computer Simulation Technology AG | Neumann R.,Helmholtz Center for Heavy Ion Research | And 4 more authors.
ACS Nano | Year: 2012

We report on the experimental and the theoretical investigation of multipole surface plasmon resonances in metal nanowires conductively connected by small junctions. The influence of a conductive junction on the resonance energies of nanowire dimers was simulated using the finite element method based software CST Microwave Studio and experimentally measured by electron energy-loss spectroscopy in a transmission electron microscope. We extend the analysis of conductively connected structures to higher order multipole modes up to third order, including dark modes. Our results reveal that an increase in junction size does not shift significantly the antibonding modes, but causes a strong blue shift of the bonding modes, leading to an energetic rearrangement of the modes compared to those of a capacitively coupled dimer with similar dimensions. © 2012 American Chemical Society. Source


Burr L.,Helmholtz Center for Heavy Ion Research | Burr L.,TU Darmstadt | Schubert I.,Helmholtz Center for Heavy Ion Research | Sigle W.,Stuttgart Center for Electronic Microscopy | And 3 more authors.
Journal of Physical Chemistry C | Year: 2015

The fabrication of nanowires by electrodeposition of Au-Ag alloy into the pores of etched ion track polymer membrane is presented. The crystallinity, morphology, and composition of wires with diameters of 85, 45, and 30 nm are investigated by means of X-ray diffraction, high-resolution scanning transmission electron microscopy, and energy-dispersive X-ray analysis. Energy-dispersive X-ray analysis with very high spatial resolution (below 1 nm) reveals the presence of surface enrichment. A Ag-rich layer in Au40Ag60 wires and a Au-rich layer in Au60Ag40 wires with thicknesses between 1 and 4 nm are observed. After dealloying in nitric acid, Ag-rich wires exhibit porous morphologies whereas Au-rich wires remain solid cylinders. The results clearly indicate that the analyzed AuAg alloy nanowires do not consist of homogeneous solid solution, but surface effects before and during the dealloying play an important role for the final morphology of dealloyed nanowires. © 2015 American Chemical Society. Source

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