Visualization of Multipolar Longitudinal and Transversal Surface Plasmon Modes in Nanowire Dimers

• Published in: ACS nano Vol. 5; no. 12; pp. 9845 - 9853
• Main Authors: Alber, Ina, Sigle, Wilfried, Müller, Sven, Neumann, Reinhard, Picht, Oliver, Rauber, Markus, van Aken, Peter A, Toimil-Molares, Maria Eugenia
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 27.12.2011
• Subjects: Bonding; Decay; Dimerization; Dimers; Electric fields; Excitation spectra; Light; Materials Testing; Maxima; Nanostructures - chemistry; Nanostructures - ultrastructure; Nanowires; Particle Size; Photometry - methods; Plasmons; Scattering, Radiation; Splitting; Surface Plasmon Resonance - methods; bonding multipol order modes; nanowire dimer synthesis; transversal surface plasmon resonance; antibonding multipol order modes; electron energy-loss spectroscopy; longitudinal surface plasmon resonances
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/nn2035044

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.