Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 85: Plasmonics and nanooptics V

O 85.6: Vortrag

Freitag, 30. März 2012, 11:45–12:00, MA 005

Quantum mechanic effects in nanoantenna enhanced infrared spectroscopy — •Jörg Bochterle, Frank Neubrech, and Annemarie Pucci — Kirchhoff-Institute for Phyiscs, Heidelberg, Germany

When light interacts with the conduction electrons of metal nanoparticles, the thereby resonantly excited localized surface plasmon resonance (LSPR) gives rise to a local field enhancement in the vicinity of the particles. Since the resonance frequency is governed by the geometrical shape of the particle, it can be tuned over a large spectral range. The strong fields are of great interest for sensing applications e.g. the detection of molecules by their vibrational fingerprint in the infrared. To measure the signal enhancement as a function of very small distances from the surface, we cooled a gold nanoantenna array on silicon substrate under ultra high vacuum conditions with liquid helium and adsorbed carbon monoxide (CO) gas. The enhanced signal of the CO stretching vibration is shown as a function of the layer thickness. Interestingly, the measurements differ from the classically expected behavior of a monotonically increasing near field towards the surface of the nanoparticle. However, describing the localized plasmon resonance quantum mechanically, the near field exhibits such monotonic increase only down to a certain distance and then decreases for smaller distances to the surface.