Plasmonic Properties of Gold Nanoparticles Separated from a Gold Mirror by an Ultrathin Oxide
- 16 March 2012
- journal article
- Published by American Chemical Society (ACS) in Nano Letters
- Vol. 12 (4), 2088-2094
- https://doi.org/10.1021/nl300351j
Abstract
That a nanoparticle (NP) (for example of gold) residing above a gold mirror is almost as effective a surface enhanced Raman scattering (SERS) substrate (when illuminated with light of the correct polarization and wavelength) as two closely coupled gold nanoparticles has been known for some time. The NP-overmirror (NPOM) configuration has the valuable advantage that it is amenable to top-down fabrication. We have fabricated a series of Au-NPOM substrates with varying but thin atomic layer-deposited oxide spacer and measured the SERS enhancement as a function of spacer thickness and angle of incidence (AOI). These were compared with high-quality finite-difference time-domain calculations, which reproduce the observed spacer thickness and AOI dependences faithfully. The SERS intensity is expected to be strongly affected by the AOI on account for the fact that the hot spot formed in the space between the NP and the mirror is most efficiently excited with an electromagnetic field component that is normal to the surface of the mirror. Intriguingly we find that the SERS intensity maximizes at ~60° and show that this is due to the coherent superposition of the incident and the reflected field components. The observed SERS intensity is also shown to be very sensitive to the dielectric constant of the oxide spacer layer with the most intense signals obtained when using a low dielectric constant oxide layer (SiO(2)).Keywords
This publication has 46 references indexed in Scilit:
- SERS and the Single MoleculePublished by Springer Science and Business Media LLC ,2007
- Plasmon absorption in nanospheres: A comparison of sodium, potassium, aluminium, silver and goldPhysica B: Condensed Matter, 2007
- Surface‐enhanced Raman spectroscopy: a brief retrospectiveJournal of Raman Spectroscopy, 2005
- Spectroscopy of Single Hemoglobin Molecules by Surface Enhanced Raman ScatteringPhysical Review Letters, 1999
- Single Molecule Detection Using Surface-Enhanced Raman Scattering (SERS)Physical Review Letters, 1997
- An accurate electromagnetic theory study of surface enhancement factors for silver, gold, copper, lithium, sodium, aluminum, gallium, indium, zinc, and cadmiumThe Journal of Physical Chemistry, 1987
- Use of a perfectly conducting sphere to excite the plasmon of a flat surface. 1. Calculation of the local field with applications to surface-enhanced spectroscopyThe Journal of Physical Chemistry, 1982
- Surface selection rulesThe Journal of Chemical Physics, 1982
- A new geometry for field enhancement in surface-enhanced spectroscopyChemical Physics Letters, 1982
- Optical Constants of the Noble MetalsPhysical Review B, 1972