Surface-Enhanced Raman Spectroscopy on an As-deposited Fano Resonance Multilayer Substrate

In this work, we exploit the use of non-patterned multilayer thin films as substrates for surface-enhanced Raman spectroscopy (SERS) investigation. An appropriate selection of materials and thickness allows obtaining Fano resonance exhibiting high peak reflection at the same working wavelength of SERS apparatus. The proposed system is constituted by Ti/Ag/ZnO/Ag/Ti deposited on a glass substrate by a sputtering technique. The SERS effect provided by the Fano resonance was investigated by micro-Raman spectroscopy through the analysis of solutions of lithium perchlorate in propylene carbonate at salt concentrations of 0.1, 0.5, 1.0, and 2.0 M and compared to a reference substrate (glass substrate) with an average enhancement of all the bands around 3. The high flexibility in obtaining easily different resonance wavelengths combined with low cost and large area fabrication technology represents the main advantage of the proposed multilayer system for SERS investigation.