We report a highly sensitive substrate for surface enhanced Raman spectroscopy (SERS) enabled by arrays of metal
(gold and silver) nanowires on the template of vertically aligned (VA-) carbon nanotubes (CNTs) coated with a high-k
dielectric hafnia (HfO2) layer as a potential barrier. Femtomolar detection of 1,2 bis-(4-pyridyl)-ethylene (BPE) is
demonstrated with this non-resonant substrate. Comparison of SERS performance with and without the hafnia potential
barrier establishes the critical contribution of this dielectric nano spacer to the large sensitivity. This behavior is
attributed to the relief of electric charge leakage from metal to the CNT template in the presence of the virtual energy
potential barrier. The VA-CNT substrate, when covered by dielectric barriers, can be a great template for a practical and
reproducible SERS substrate.
The interaction of large-area single-layer CVD-graphene with a metasurface constituted by THz split-ring resonators was studied via THz Time-Domain Spectroscopy in the frequency range 250 GHz÷2.75 THz. Transmission measurements showed that the presence of the graphene shifts the resonances of the THz-metasurface towards lower energies and increases the transmittance, mainly at resonance. A comparison between two possible configuration is here presented revealing a much stronger interaction for the case of split-ring resonators evaporated directly onto the CVD-graphene layer with respect to the opposite configuration. From the recent literature the presented system is a good candidate for THz modulators with possible use also in cavity-QED experiments.