Enhanced Raman scattering from nanoparticle-decorated nanocone substrates: A practical approach to harness in-plane excitation

Ying S. Hu, Jaeseok Jeon, Tae J. Seok, Seunghyun Lee, Jason H. Hafner, Rebekah A. Drezek, Hyuck Choo

Research output: Contribution to journalArticle

39 Scopus citations

Abstract

We investigate surface-enhanced Raman scattering (SERS) from gold-coated silicon-germanium nanocone substrates that are decorated with 30-nm spherical gold nanoparticles (AuNPs). Finite-element simulations suggest that individual nanocones generate stronger electromagnetic enhancement with axial polarization (i.e., polarization parallel to the vertical axis of the nanocones) than with transverse polarization (i.e., polarization in the plane of the nanocone substrate), whereas the excitation in a typical Raman microscope is mainly polarized in the transverse plane. We introduce a practical approach to improve the SERS performance of the substrate by filling the valleys between nanocones with AuNPs. Simulations reveal an enhanced electric field at the nanoscale junctions formed between AuNPs and nanocones, and we explain this lateral coupling with a hybridization model for a particle-film system. We further experimentally verify the added enhancement by measuring SERS from trans-1,2-bi-(4-pyridyl) ethylene molecules absorbed onto the substrates. We report over one order-of-magnitude increase in SERS activities with the AuNP decoration (compared to the nanocone substrate without AuNPs) and achieve a spatially averaged enhancement factor of 1.78 × 108 at 785-nm excitation. Understanding and implementing the enhancing mechanism of structured metallic surfaces decorated with plasmonic nanoparticles open possibilities to substantially improve the SERS performance of the existing process-engineered substrates.

Original languageEnglish (US)
Pages (from-to)5721-5730
Number of pages10
JournalACS Nano
Volume4
Issue number10
DOIs
StatePublished - Oct 26 2010
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

Keywords

  • Raman scattering
  • SERS
  • gold nanoparticles
  • in-plane excitation
  • nanocone substrate
  • plasmon hybridization
  • surface plasmon

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