Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 23: Plasmonics and Nanooptics: Structure, Fabrication and Characterization

O 23.6: Vortrag

Dienstag, 17. März 2015, 11:45–12:00, MA 043

Cathodoluminescence of sharp Au- and Ag-tips in the vicinity of a Au-film — •Martin Grüßer, Xinzhou Ma, and Rolf Schuster — Institute of Physical Chemistry, Condensed Matter Division, Karlsruhe Institute of Technology (KIT), Germany

Sharp metal tips acting as optical antennas play an important role in many experimental applications. The locally enhanced electromagnetic field allows, e.g., for tip-enhanced raman spectroscopy [1, 2] on the single molecule level. In addition to the lightning-rod effect, also surface plasmons localized at the tip apex and gap plasmons between a tip and a sample surface [3] contribute to the field enhancement.

To investigate the local excitation of surface plasmons and gap plasmons in the tip-surface system we employ, cathodoluminescence upon electron irradiation in a scanning electron microscope (SEM), which accesses the radiative modes of the electron excited plasmons. The distance between tip and surface is controlled by a scanning tunneling microscope, mounted inside the vacuum chamber of the SEM. We observed enhanced photon emission upon electron irradiation near the tip-surface gap, on both the tip as well as on the sample side. Spectra upon irradiation of tip or sample show strong differences in intensity and peak position, e.g. a redshift for smaller tip-surface distances and evolution of additional peaks, which may depend on the formation of gap plasmons.

[1] R. M. Stöckle et al., Chem. Phys. Lett. 2000, 318, 131. [2] B. Pettinger et al., Annu. Rev. Phys. Chem. 2012, 63, 379. [3] Z. Yang, J. Aizpurua, H. Xu, J. Raman Spectrosc. 2009, 40, 1343.