Fabrication of double split metallic nanorings for raman sensing

We describe the fabrication and characterisation of arrays of metallic plasmon resonant nanorings, each of which are formed from two semicircles of different radius. We show that using a dual semicircle structure defined by electron beam lithography can result in closely spaced localized plasmon resonant peaks in the visible region, which cannot be achieved using a simpler nanoring structure with one radius. The advantage of producing two closely spaced resonant peaks is a structure that can be used for Raman sensing purposes at two different wavelengths.