Sequential feature-density doubling for ultraviolet plasmonics

Patterning of nanostructures with sub-200 nm periodicities over cm2-scale areas is challenging using standard approaches. This paper demonstrates a scalable technique for feature-density doubling that can generate nanopatterned lines with periodicities down to 100 nm covering >3 cm². We developed a process based on controlled wet overetching of atomic-layer deposited alumina to tune feature sizes of alumina masks down to several nm. These features transferred into silicon served as masters for template-stripping aluminum nanogratings with three different periodicities. The aluminum nanogratings supported surface plasmon polariton modes at ultraviolet wavelengths that, in agreement with calculations, depended on periodicity and incident excitation angle.