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

: Kilic, U.; Mock, A.; Feder, R.; Sekora, D.; Hilfiker, M.; Korlacki, R.; Schubert, E.; Argyropoulos, C.; Schubert, M.

Fulltext ()

Scientific Reports 9 (2019), Art. 71, 11 pp.
ISSN: 2045-2322
Deutsche Forschungsgemeinschaft DFG
FE 1532/1-1
Journal Article, Electronic Publication
Fraunhofer IMWS ()

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.