Nanocrescents have become an important surface enhanced Raman scattering (SERS) structure because unlike structures that rely on a few nanometer gap inter-particle plasmonic coupling to achieve high electrical field, nanocrescents are fabricated on hundreds of nanometer template sacrificial nanoparticles, where intra-particle plasmonic coupling between the cavity modes and the tip edges are utilized to achieve high electrical field. Unlike previous efforts, our fabrication approach creates three dimensional (3-D) up-right oriented nanocrescent structures with controllable cavity rim opening. Randomly-distributed silica nanoparticles are spun onto a substrate coated with a photoresist layer. Reactive ion etching is then used to etch into the photoresist to create small narrow pedestal with the nanoparticles serving as etching masks. The etching recipe and time will determine the diameter of the pedestal and ultimately, the cavity rim opening of the nanocrescents. We have fabricated and measured nanocrescent structures with as smaller as ~50 nm cavity rim opening. A maximum enhancement factor ~10⁷ has been achieved so far. Moreover, the repeatability of the enhancement factor (EF) from one nanocrescent to the next within the same substrate is better than 80%. We attributed the measurement consistency to the up-right orientation of the nanocrescent structures.

Date Published: 6 February 2012
PDF: 6 pages
Proc. SPIE 8234, Plasmonics in Biology and Medicine IX, 823409 (6 February 2012); doi: 10.1117/12.908810

Published in SPIE Proceedings Vol. 8234:
Plasmonics in Biology and Medicine IX
Tuan Vo-Dinh; Joseph R. Lakowicz, Editor(s)