Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 57: Plasmonics and Nanooptics II

O 57.7: Vortrag

Mittwoch, 2. April 2014, 17:30–17:45, GER 38

Probing antenna enhanced near-fields with nanometer-scale resolution — •F. Neubrech1,2, S. Beck2,3, T. Glaser2,3, M. Hentschel1, H. Giessen1 und A. Pucci2,3,414th Physics Institute and Research Center SCoPE, Stuttgart, Germany — 2Kirchhoff Institute for Physics, Heidelberg, Germany — 3InnovationLab GmbH, Heidelberg, Germany — 4Centre for Advanced Materials (CAM), Heidelberg, Germany

Nanoantenna-assisted surface enhanced infrared spectroscopy is a powerful tool to detect minute amounts of analytes. Based on the confined electromagnetic near fields of the resonantly excited metal nanoparticles, the molecular vibrations of the analytes are enhanced by orders of magnitudes. On the other hand, the enhanced vibrational signal strength of well-known probe molecules can also be utilized to obtain information on the near field enhancement with resolution only limited by the size of the probe molecule. Following this approach, we employed 4,4*-bis(N-carbazolyl)-1,1*-biphenyl (CBP) to measure the local near fields of resonantly excited nanoantennas with nanometer-scale resolution. Therefore, we stepwise evaporated CBP molecules under ultra-high vacuum conditions onto the metal nanostructures and acquired infrared spectra after each evaporation step. Besides the decreasing vibrational signal per nanometer, we observed a red-shift of the resonance frequency with increasing thickness. This shift originates from the polarizability change caused by the evaporated material. Furthermore, we performed finite different time domain simulations and found a good qualitative agreement with our experimental data.

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