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O: Fachverband Oberflächenphysik
O 60: Poster Session IV (Solid/liquid interfaces; Semiconductors; Oxides and insulators; Graphene; Plasmonics and nanooptics; Electronic Structure; Surface chemical reactions; Heterogeneous catalysis)
O 60.58: Poster
Mittwoch, 16. März 2011, 17:30–21:00, P4
Experimental indication of quantum mechanical effects in surface enhanced IR-spectroscopy? — •Jörg Bochterle1, Frank Neubrech1, Annemarie Pucci1, Dominik Enders2, and Tadaaki Nagao2 — 1Kirchhoff-Institute for Physics, Heidelberg, Germany — 2Institute for Material Science, Tsukuba, Japan
The conduction electrons of metal nanoparticles can be collectively excited by incident electromagnetic radiation. Their resonance frequency strongly depends on the geometric dimensions of the particles and can be tuned from the classical radio frequencies up to the visible range. Such resonantly excited localized surface plasmon-polaritons are accompanied by an electromagnetic nearfield enhancement at the surface. In the infrared spectral range these huge local fields can be applied to the enhancement of infrared vibrations of molecules. Using this technique with gold nanostripes, attomol sensitivity has been achieved.
In this contribution we look at the signal enhancement of the carbon monoxide (CO) stretching vibration of physisorbed CO ice on gold nanoantennas on silicon substrates under ultrahigh vacuum conditions. The signal changes with increasing CO layer thickness are measured in situ and exhibit a behavior differing from the classical expectations. While in the classical description the nearfield is monotonically increasing with decreasing distances to the surface, the quantum description of the localized plasmon resonance exhibits such monotonic increase only down to a certain distance and then decreases for smaller distances to the surface.