Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 36: Plasmonics and Nanooptics
O 36.20: Poster
Tuesday, March 17, 2015, 18:15–21:00, Poster A
Real space imaging of nanotip plasmons using electron energy-loss spectroscopy — •Benjamin Schröder1, Sergey Yalunin1, Thorsten Weber2,3, Murat Sivis1, Felix von Cube2,3, Thomas Kiel4, Christian Matyssek4, Stephan Irsen3, Kurt Busch4, Claus Ropers1, and Stefan Linden2 — 1IV. Physical Institute, University of Göttingen, Germany — 2Physikalisches Institut, Rheinische Friedrich-Wilhelms-Universität Bonn, Germany — 3Research center caesar, center of advanced european studies and research, Bonn, Germany — 4Institut für Physik, Humbold-Universität zu Berlin, Germany
The excitation of surface plasmon polaritons (SPPs) on metallic nanotips results in a plasmonic confinement and enhancement of electromagnetic fields at the apex. This field concentration provides for novel means of imaging and spectroscopy. One key aspect for the understanding and optimization of such a plasmonic structure is the dispersive evolution of propagating SPPs. In this contribution, we present a study of SPP excitation on a gold tip by using a scanning transmission electron microscope in combination with electron energy-loss spectroscopy. This technique allows for a spatially and spectrally resolved mapping of standing wave patterns on the nanotip's shaft. The data clearly shows a wavelength compression towards the apex and also indicates a significant contribution of higher azimuthal modes with increasing radii. We provide a fully retarded theoretical analysis of the adiabatic phenomenon based on a modal expansion. The numerical results demonstrate an excellent agreement with the data.