Integration of Metallic Nanostructures in Fluidic Channels for Fluorescence and Raman Enhancement by Nanoimprint Lithography and Lift-off on Compositional Resist Stack

A water-processable cellulose-based resist for advanced nanofabrication

The ideal nanofabrication technique is one that allows the mass production of high resolution submicrometric features in a cost efficient and environmentally friendly fashion. A great step towards achieving this goal has been the development of nanoimprinting lithography, a procedure with tenths of nanometres resolution while being compatible with roll-to-roll manufacturing. However, an ecofriendly resist that can be efficiently combined with this process is still missing. In this work, we demonstrate the use of hydroxypropyl cellulose (HPC) as a biocompatible, biodegradable, and water processable resist for temperature assisted nanoimprint lithography (tNIL) by fabricating different photonic architectures. The cellulose derivative is easily patterned with submicrometric features with aspect ratios greater than 1 using an elastomeric stamp and a hot plate. Silicon photonic crystals and metal nanoparticle arrays are fabricated combining cellulose with traditional nanofrabrication processes such as spincasting, reactive ion etching and metal lift off. Furthermore, advanced nanofabrication possibilities are within reach by combining the HPC with traditional resists. In particular, poly(methyl methacrylate) and HPC stacks are easily produced by liquid phase processing, where one of the two materials can be selectively removed by developing in orthogonal solvents. This capability becomes even more interesting by including nanoimprinted layers in the stack, leading to the encapsulation of arrays of air features in the resist.

Plasmonic bar-coupled dots-on-pillar cavity antenna with dual resonances for infrared absorption and sensing: performance and nanoimprint fabrication

We report the structure, performance and large-area fabrication of a thin plasmonic infrared absorber, termed "bar-shaped disk-coupled dots-on-pillar antenna-array" (bar-D2PA). The bar-D2PAs, which are simple to fabricate, demonstrate the following, experimentally: (i) a different light-absorption resonance for each polarization with the resonance peak tunable by the bar-to-backplane gap and the bar size; (ii) for the geometry tested, the reflection is nearly constant at ∼10%, but the transmission and absorption highly depend upon the bar size and the gap between the bar and the backplane (e.g., the absorption of 77% (30%), the transmission of 9% (62%), and the resonance peak at 3.12 μm (3.04 μm) for the polarization along 700 nm long (185 nm short) axis and a 20 nm gap); (iii) a smaller gap significantly enhances the normalized extraordinary transmission, and (iv) the extraordinary transmissions become larger as the polarized bar side is in deeper subwavelength. The bar-D2PAs were fabricated in large area using nanoimprint lithography, etching plus one metal deposition that forms all metal structures in one step with excellent self-alignment and self-assembly. The design and fabrication can be extended to broad plasmonic applications.