title: Impact of titanium adhesion layers on the response of arrays of metallic split-ring resonators (SRRs).
abstract: At higher frequencies (visible and infrared) both the dimensions and the individual metal properties play an important role in determining the resonant response of arrays of SRRs. As a result, a substantial difference between the responses of gold- and Al-based SRR arrays has been observed. Additionally, deposition of gold SRRs onto a substrate typically involves the use of an additional adhesion layer. Titanium (Ti) is the most common adhesive thin-film material used to attach gold onto dielectric/semiconductor substrates. In this paper we investigate the impact of the Ti adhesion layer on the overall response of Au-based nano-scale SRRs. The results quantify the extent to which the overall difference in the resonance frequencies between Au- and Al-based SRRs is due to the presence of the Ti. We show that even a 2-nm-thick Ti layer can red-shift the position of SRR resonance by 20 nm. Finally, we demonstrate that by intentional addition of titanium in the Au-based SRRs, their overall resonant response can be tuned widely in frequency, but at the expense of resonance magnitude.
authors.affiliation: Department of Electronics and Electrical Engineering, University of Glasgow, Glasgow G12 8LT, UK.
authors.forename: Basudev
authors.initials: B
authors.lastname: Lahiri
authors.forename: Rafal
authors.initials: R
authors.lastname: Dylewicz
authors.forename: Richard M
authors.initials: RM
authors.lastname: De La Rue
authors.forename: Nigel P
authors.initials: NP
authors.lastname: Johnson
mesh_terms: D000268:Adhesiveness; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006046:Gold / Q000737:chemistry*; D055096:Optical Devices; D014025:Titanium / Q000737:chemistry*; D014159:Transducers; D014732:Vibration
chemical_list: D006046:Gold; D014025:Titanium