Methods for sub 10 nm plasmonic nanopores fabrication are usually complex and require multi-step processes usually suitable for the preparation of single pores. Other processes to fabricate metallic nanopores involve pore shrinking by metal evaporation, which is applied to the whole substrate, increasing its thickness; therefore it is not localized and reduces spatial resolution. For that reason, a process in which metal deposition can be controlled at the nanoscale, is a key advancement in the field. Here, we report on a process for the fabrication of sub 10 nm solid-state plasmonic nanopores, via photocatalytic effect caused by the electromagnetic field enhancement in metallic rings on top of dielectric nanotubes. Under illumination, the areas of maximum field inside these structures trigger sites for metal nucleation and growth. Using this methodology, we fabricated Au-Ag and Au-Au nanopores, with consistent and reproducible shrinkage in pore diameter. Numerical simulations were performed in order to support the findings and to show how the obtained plasmonic structures can be used to confine the electromagnetic field, enhancing the intensity in a volume in the scale of sub 10 nm. The confinement of the field inside the final nanopore can be used for thermoplasmonic effects modifying ionic conductivity inside the pore under different illumination wavelengths.
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