Nanostencil lithography for high-throughput fabrication of infrared plasmonic sensors

We demonstrate a novel fabrication approach for high-throughput fabrication of engineered infrared plasmonic nanorod antenna arrays with Nanostencil Lithography (NSL). NSL technique, relying on deposition of materials through a shadow mask, offers the flexibility and the resolution to fabricate radiatively engineer nanoantenna arrays for excitation of collective plasmonic resonances. Overlapping these collective plasmonic resonances with molecular specific absorption bands can enable ultrasensitive vibrational spectroscopy. First, nanorod antenna arrays fabricated using NSL are investigated using SEM and optical spectroscopy, and compared against the nanorods with the same dimensions fabricated using EBL. No irregularities on the periodicity or the physical dimensions are detected for NSL fabricated nanorods. We also confirmed that the antenna arrays fabricated by NSL shows high optical quality similar to EBL fabricated ones. Furthermore, we show nanostencils can be reused multiple times to fabricate selfsame structures with identical optical responses repeatedly and reliably. This capability is particularly useful when high-throughput replication of the optimized nanoparticle arrays is desired. In addition to its high-throughput capability, NSL permits fabrication of plasmonic devices on surfaces that are difficult to work with electron/ion beam techniques. Nanostencil lithography is a resist free process thus allows the transfer of the nanopatterns to any planar substrate whether it is conductive, insulating or magnetic. As proof of the versatility of the NSL technique, we show fabrication of plasmonic structures in variety of geometries. We also demonstrate that nanostencil lithography can be used to achieve functional plasmonic devices in a single fabrication step, on variety of substrates. We introduced NSL for fabrication of nanoplasmonic structures including antenna arrays on rigid surfaces such as silicon, CaF2 and glass. In conclusion, Nanostencil Lithography enables plasmonic substrates supporting spectrally narrow far-field resonances with enhanced near-field intensities which are very useful for vibrational spectroscopy. We believe this nanofabrication scheme, enabling the reusability of stencil and offering flexibility on the substrate choice and nano-pattern design could significantly enhance wide-use of plasmonics in sensing technologies.