Split ring resonators: the effect of titanium adhesion layers on the optical response

Abstract

The response of metallic split ring resonators (SRRs) scales linearly with their dimensions. At higher frequencies, metals do not behave like perfect conductors but display properties characterized by the Drude model. In this paper we compare the responses of nano-sized gold-based SRRs at near infra-red wavelengths. Deposition of gold SRRs onto dielectric substrates typically involves the use of an additional adhesion layer. We have employed the commonly used metal titanium (Ti) to provide an adhesive layer for sticking gold SRRs to silicon substrates - and have investigated the effect of this adhesion layer on the overall response of these gold SRRs. Both experimental and theoretical results show that even a two nm thick titanium adhesion layer can shift the overall SRR response by 20 nm.