Abstract
In this paper we report the fabrication and characterization of a plasmonic device for label-free detection of few molecules in sub-wavelength regime by means of Raman scattering. The device is based on the coupling between a gold nanocone and a photonic crystal cavity, that is able to excite surface plasmon polaritons (SPPs) at the base on the cone. During the propagation toward the tip of the cone, the SPPs experiment and adiabatic compression that allow the accumulation of a very high electric field at the tip end. Raman enhancement factor of more than five order of magnitude is reported for a tip with a radius of curvature of about 10 nm. The present results open up future perspective on single molecule detection even in combination with AFM measurements. (C) 2009 Elsevier B.V. All rights reserved.