Tunable plasmonic resonances in highly porous nano-bamboo Si-Au superlattice-type thin films

Authors

Ufuk Kılıç, University of Nebraska-LincolnFollow
Alyssa Mock, University of Nebraska-LincolnFollow
René Feder, University of Nebraska-Lincoln
Derek Sekora, University of Nebraska-LincolnFollow
Matthew J. Hilfiker, University of Nebraska-LincolnFollow
Rafal Korlacki, University of Nebraska-LincolnFollow
Eva Schubert, University of Nebraska-LincolnFollow
Christos Argyropoulos, University of Nebraska-LincolnFollow
Mathias Schubert, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

7-17-2018

Citation

https://arxiv.org/abs/1807.06166v1

Comments

Copyright (c) 2018 Ufuk Kilic, Alyssa Mock, Rene Feder, Derek Sekora, Matthew Hilfiker, Rafal Korlacki, Eva Schubert, Christos Argyropoulos, Mathias Schubert

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. The superlattice-type columns resemble bamboo structures where smaller column sections of gold form junctions sandwiched between larger silicon column sections (“nano-bamboo”). We perform generalized spectroscopic ellipsometry measurements and finite element method computations to elucidate the strongly anisotropic optical properties of the highly-porous nano-bamboo structures. 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 the nano-bamboo structure. 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 the nano-bamboo structures as a highly porous plasmonic sensor with optical read out sensitivity to few parts-per-million solvent levels in water.