KEYWORDS: Plasmonics, Lithography, Nanolithography, Electron beam lithography, Photomasks, Metamaterials, Antennas, Fabrication, Near field optics, Nanorods
We demonstrate a novel fabrication approach for high-throughput fabrication of engineered plasmonic antenna arrays
and metamaterials 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. We 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 highthroughput
replication of the optimized nanoparticle arrays is desired. In addition to its high-throughput capability, NSL
permits single step nanofabrication 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 and metamaterials in variety of geometries. In metamaterial and plasmonic devices,
unique geometries with small gaps and asymmetries can induce novel electromagnetic responses such as plasmon
induced transparency and also giant near-field intensities that are important for enhanced vibrational spectroscopy and
non-linear optics applications. 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.1
KEYWORDS: Plasmonics, Nanolithography, Lithography, Electron beam lithography, Antennas, Photomasks, Fabrication, Near field optics, Nanostructures, Nanorods
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.
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 radiatively engineer nanoantenna arrays for excitation of collective
plasmonic resonances. As stencil, we use suspended silicon nitride membrane patterned with nanoapertures and fabricate
nanorod antenna arrays. Our spectral measurements and electron microscopy images faithfully confirm the feasibility of
NSL technique for large area patterning of nanorod antenna arrays with optical qualities achievable by electron-beam
lithography. Furthermore, we show nanostencils can be reused multiple times to fabricate same structures repeatedly and
reliably with identical optical responses. 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, by simply changing the aperture pattern on the silicon
nitride membrane, we show fabrication of plasmonic structures in variety of geometries and on different substrates.
Nanostencil Lithography enables fabrication of plasmonic substrates supporting spectrally narrow far-field resonances
with enhanced near-field intensities. Overlapping these collective plasmonic resonances with molecular specific
absorption bands can enable ultrasensitive vibrational spectroscopy.
Performances of surface biosensors are often controlled by the analyte delivery rate to the sensing surface instead of
sensors intrinsic detection capabilities. In a microfluidic channel, analyte transports diffusively to the biosensor surface
severely limiting its performance. At low concentrations, this limitation, commonly known as mass transport problem,
causes impractically long detection times extending from days to months. In this proceeding, we propose and
demonstrate a hybrid biosensing platform merging nanoplasmonics and nanofluidics. Unlike conventional approaches
where the analytes simply stream pass over the sensing surface, our platform enables targeted delivery of analytes to the
sensing surface. Our detection platform is based on extraordinary light transmission effect (EOT) in suspended
plasmonic nanohole arrays. The subwavelength size nanoholes here act as nanofluidic channels connecting the
microfluidic chambers on both sides of the sensors. In order to materialize our detection platform, we also introduce a
novel multilayered micro/nanofluidics scheme allowing three dimensional control of the fluidic flow. Using our
platform, we show 14-fold improvement in mass transport rate constant appearing in the exponential term. To fabricate
these biosensors, we also introduce a lift-off free plasmonic device fabrication technique based on positive resist electron
beam lithography. Simplicity of this fabrication technique allows us to fabricate nanostructures with ease, high
yield/reproducibility and minimal surface roughness. As a result, we achieve higher refractive index sensitivities. This
fabrication technique can find wide range of applications in nanoplasmonics field by eliminating the need for
operationally slow and expensive focused ion beam lithography.
In this paper, we introduce a novel sensor scheme which merges nano-photonics and nano-fluidics on a single platform
through the use of free-standing photonic crystals (PhCs). PhCs offer great freedom to manipulate the spatial extent and
the spectral characteristics of the electromagnetic fields. Also, nanoholes in PhCs provide a natural platform to transport
solutions. By harnessing these nano-scale openings, we theoretically and experimentally demonstrate that both fluidics
and light can be manipulated at sub-wavelength scales. In this scheme, the free standing PhCs are sealed in a chamber
such that only the nano-scale hole arrays enable the flow between the top and the bottom channels. The nanohole arrays
are used as sensing structures as well as nanofluidic channels. Compared to the conventional fluidic channels, we can
actively steer the convective flow through the nanohole openings for effective delivery of the analytes to the sensor
surface. This scheme also helps to overcome the surface tension of highly viscous solution and guarantees that the sensor
can be totally immersed in solution. We apply this method to detect refractive index changes in aqueous solutions. Bulk
measurements indicate that active delivery of the convective flow results in better performance. The sensitivity of the
sensor reaches 510 nm/RIU for resonance located around 850 nm with a line-width of ~10 nm in solution. Experimental
results are matched very well with numerical simulations. We also show that cross-polarization measurements can be
employed to further improve the detection limit by increasing the signal-to-noise ratio.
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