Subwavelength nickel-copper multilayers as an alternative plasmonic material

Abstract

Surface plasmon polaritons (SPP) are electromagnetic waves bound by the collective oscillations of free carrier plasma to the surface of a conductor surrounded by dielectric. These waves can be localized, concentrated or manipulated simply by processing the conductor surface. The choice of a convenient conductor is quite limited by the availability of natural materials and strong absorption losses associated with free electron plasma. For this reason new alternative plasmonic materials are actively being researched and developed. Most common approaches to this problem include doping of nonmetallic materials and fabrication of metal-dielectric nanocomposite metamaterials. In this contribution we perform an analysis of the suitability of the use of the heterometallic multilayers consisting of copper and nickel. Copper is an excellent plasmonic material, but the problem is formation of natural copper oxides on the surface. Therefore for this purpose a layer of nickel is used as a protection against oxidation of copper. Laminate composite structures of alternating nanocrystalline nickel and copper films on a cold-rolled polycrystalline copper foils were fabricated by electrochemical deposition technique. We simulated the electromagnetic properties of subwavelength Cu/Ni multilayers by the 2D finite element method using realistic material parameters to assess different electromagnetic modes. Our results show that the pair Cu/Ni can be viewed as an alternative tailorable plasmonic material. It has also been shown that it is possible to fabricate plasmonic structures without applying any complex lithographic processes.