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O: Fachverband Oberflächenphysik
O 11: Poster Session I: Plasmonics and nanooptics I
O 11.4: Poster
Monday, March 1, 2021, 10:30–12:30, P
Dramatic Enhancement of Tip-Enhanced Raman Scattering Mediated by Atomic Point Contact Formation — •Shuyi Liu1, Borja Cirera1, Yang Sun2, Ikutaro Hamada2, Melanie Muller1, Adnan Hammud3, Martin Wolf1, and Takashi Kumagai1,4 — 1Department of Physical Chemistry, Fritz-Haber Institute of the Max-Planck Society, Berlin, Germany — 2GREEN, National Institute for Materials Science, Ibaraki, Japan — 3Department of Inorganic Chemistry, Fritz-Haber Institute of the Max-Planck Society, Berlin, Germany — 4Center for Mesoscopic Sciences, Institute for Molecular Science, Okazaki, Japan
Tip-enhanced Raman scattering (TERS) in ångström-scale plasmonic cavities has drawn increasing attention. However, Raman scattering at vanishing cavity distances remains unexplored. In this presentation, I show the evolution of TERS in transition from the tunneling regime to atomic point contact (APC). A stable APC is reversibly formed in the junction between an Ag tip and ultrathin ZnO or NaCl films on the Ag(111) surface at 10 K. An abrupt increase of the TERS intensity occurs upon APC formation for ZnO, but not for NaCl. This remarkable observation is rationalized by a difference in hybridization between the Ag tip and these films, which determines the contribution of charge transfer enhancement in the fused plasmonic junction. The strong hybridization between the Ag tip and ZnO is corroborated by the appearance of a new vibrational mode upon APC formation, whereas it is not observed for the chemically inert NaCl.