(291g) Large Area Graphene Nanoribbons By Wetting Transparency-Assisted Block Copolymer Lithography

Graphene plasmons have gained considerable attention during the last decade due to their potential to overcome current challenges facing traditional plasmonic materials, such as goldâ??s limited spatial resolution and extinction wavelengths. In particular, patterning graphene into nanoribbons (graphene nanoribbons, GNR) allows for tunability in the emerging fields of mid-infrared and terahertz spectroscopy based devices. However, the fabrication of GNR arrays for these plasmonic devices often includes a low-throughput electron beam lithography step that cannot be easily scaled to large areas. In this study, we developed a new and more scalable GNR fabrication method based on block copolymer (BCP) lithography. To pattern graphene into GNRs, lamellae-forming BCP domains must be oriented perpendicular to substrate and then selectively etched. However, perpenducular orientation can only be achieved when the surface energy of the underlying substrate is neutral or non-preferential to wetting either block of the BCP. Extensive contact angle and surface energy measurements indicated that the surface neutrality of the underlying substrate is mostly retained even with a single layer of graphene coating the top of the underlying substrate. This is due to the wetting transparency of graphene. Using wetting transparency-assisted BCP lithography, we successfully fabricated large-area (cm² scale) GNR arrays with 20 nm nanoribbon widths. The optical properties of the GNR arrays were studied by Fourier transform infrared spectroscopy, and a clear plasmonic extinction peak in the mid-infrared region (~1600 cm^-1)was observed. This GNR fabrication method could be useful for high-throughput production of a broad range of mid-infrared plasmonic devices, including modulators, biosensors, and photodetectors.