Tunable plasmonic resonances in Si-Au slanted columnar heterostructure thin films

Ufuk Kılıç, Alyssa Mock, René Feder, Derek Sekora, Matthew Hilfiker, Rafał Korlacki, Eva Schubert, Christos Argyropoulos, Mathias Schubert

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Abstract

We report on fabrication of spatially-coherent columnar plasmonic nanostructure superlattice-type thin films with high porosity and strong optical anisotropy using glancing angle deposition. Subsequent and repeated depositions of silicon and gold lead to nanometer-dimension subcolumns with controlled lengths. We perform generalized spectroscopic ellipsometry measurements and finite element method computations to elucidate the strongly anisotropic optical properties of the highly-porous Si-Au slanted columnar heterostructures. The occurrence of a strongly localized plasmonic mode with displacement pattern reminiscent of a dark quadrupole mode is observed in the vicinity of the gold subcolumns. We demonstrate tuning of this quadrupole-like mode frequency within the near-infrared spectral range by varying the geometry of Si-Au slanted columnar heterostructures. In addition, coupled-plasmon-like and inter-band transition-like modes occur in the visible and ultra-violet spectral regions, respectively. We elucidate an example for the potential use of Si-Au slanted columnar heterostructures as a highly porous plasmonic sensor with optical read out sensitivity to few parts-per-million solvent levels in water.

Original languageEnglish (US)
Article number71
JournalScientific reports
Volume9
Issue number1
DOIs
Publication statusPublished - Dec 1 2019

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