Plasmon-based light enhancement from a hybrid copper-gold planar structure

摘要

We propose a novel and cost-effective copper-gold planar nanostructure resulting in strong plasmonic enhancement of the electromagnetic field with a peak at 615 nm and FWHM of 180 nm. The structure consists of aggregates of 20 nm in diameter gold nanospheres on a thin continuous 50 nm thick copper film. We attribute the strong field enhancement to the coupling of interparticle plasmon resonances from gold nanospheres to the surface plasmons induced in the copper film. The high reflectivity of the copper layer increases the collection efficiency in a reflection mode of the scattered light that would otherwise be transmitted. We achieved the homogeneity and planarity of the copper-gold structure through the electrostatic attraction between the negative surface charge of gold nanospheres and a lattice of positive copper ions of copper oxide, formed by ionic bonds during the exposure of copper to air.