Defect-induced activation of symmetry forbidden infrared resonances in individual metallic nanorods

F. Neubrech (1) , A. Garcia-Etxarri (2) , D. Weber (1) , J. Bochterle (1) , H. Shen (3) , Marc Lamy de La Chapelle (4) , G.W. Bryant (1) , J. Aizpurua (3) , A. Pucci (1)

1 Kirchhoff Institut für Physik
2 CICNanoGUNE
3 CSIC - Consejo Superior de Investigaciones Cientificas [España] = Spanish National Research Council [Spain]
4 CSPBAT - Chimie, Structures et Propriétés de Biomatériaux et d'Agents Thérapeutiques

We report on the observation of second-order infrared (IR) plasmon resonances in lithographically prepared gold nanorods investigated by means of far-field microscopic IR spectroscopy. In addition to the fundamental antennalike mode, even and odd higher order resonances are observed under normal incidence of light. The activation of even-order modes under normal incidence is surprising since even orders are dipole-forbidden because of their centrosymmetric charge density oscillation. Performing atomic force microscopy and calculations with the boundary element method, we determine that excitation of even modes is enabled by symmetry breaking by structural deviations of the rods from an ideal, straight shape. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3437093]

Mots clés: ENHANCED RAMAN-SCATTERING, PLASMONIC NANOSTRUCTURES, NANOPARTICLES, MOLECULES, ARRAYS

Domaines: Optique [physics.optics]

F. Neubrech, A. Garcia-Etxarri, D. Weber, J. Bochterle, H. Shen, et al.. Defect-induced activation of symmetry forbidden infrared resonances in individual metallic nanorods. Applied Physics Letters, 2010, 96 (21), 3 p. ⟨10.1063/1.3437093⟩. ⟨hal-00629292⟩