Physical mechanisms behind the SERS enhancement of pyramidal pit substrates

• Published in: Journal of Raman spectroscopy 2010-10, Vol.41 (10), p.1106-1111
• Main Authors: Vernon, K. C., Davis, T. J., Scholes, F. H., Gómez, D. E., Lau, D.
• Format: Article
• Language: English
• Subjects: Apex angle; Arrays; Computer simulation; Klarite; Mathematical models; Metal coatings; Pits; plasmon; SERS; Silicon substrates; Three dimensional
• ISSN: 0377-0486; 1097-4555; 1097-4555
• DOI: 10.1002/jrs.2557

In this paper we theoretically consider the physical mechanisms behind the surface‐enhanced Raman scattering (SERS) enhancement produced by commercially available Klarite substrates, which consist of rectangular arrays of micrometre‐sized pyramidal pits in silicon with a thin gold coating. Full three‐dimensional numerical simulations of the pits are conducted for both a real gold metal coating and a perfect electrical conductor (PEC) to determine whether the SERS enhancement is due to diffraction or plasmon effects. The pit apex angle and metal coating thickness are also varied to determine whether it is possible to further enhance the SERS signal by optimising the structural parameters of these substrates. By decreasing the film thickness and adjusting the apex angle, it is possible to achieve an enhancement almost double that of a standard Klarite substrate. Copyright © 2010 John Wiley & Sons, Ltd. The origin of the SERS enhancement in triangular pits is investigated using 3D numerical simulations for both a gold metal coating and a perfect electrical conductor (PEC). It is shown that diffraction effects dominate over plasmonic effects for large metal coating thicknesses. By decreasing the thickness of the metal coating and adjusting the apex angle, the simulations predict that the SERS enhancement can almost double.