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O: Fachverband Oberflächenphysik

O 90: Sensing, Active Structures and other Applications

O 90.13: Vortrag

Donnerstag, 19. März 2015, 18:00–18:15, MA 144

Fabrication of plasmonic nanoantennas by femtosecond direct laser writing lithography - effects of near field coupling on SEIRA enhancement — •Frank Neubrech, Shahin Bagheri, Ksenia Weber, Timo Gissibl, and Harald Giessen — 4th Physics Insitute and Research Centre SCOPE, University of Stuttgart, Germany

We demonstrate the use of femtosecond two-photon direct laser writing lithography (2D printing) for fast and homogeneous large-area fabrication of plasmonic nanoantennas on a substrate by creating patterned polymer as an etch mask. Subsequent Argon-ion beam etching provides nanoantennas with feature sizes below the diffraction limit of the laser light, exhibiting tunable high quality plasmon resonances in the mid-infrared spectral range which are ideally suited for surface-enhanced infrared absorption (SEIRA). In the present work, we demonstrate the reliable and simple fabrication of a wide variety of antenna arrays and examine particularly the influence of plasmonic coupling between neighboring antennas on the SEIRA enhancement effect. More specifically, we measure the enhanced infrared vibrational bands of a 5 nm thick 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) layer evaporated on arrays with different longitudinal and transversal spacings between antennas. An optimum SEIRA enhancement per antenna of four orders of magnitude was found close to the collective plasmon excitation in the nanoantenna array. This ideal distance is giving higher signals than simply the highest antenna density.