Towards perfect absorption via block copolymer designed metasurfaces

Engineering light-matter nanoscale interactions has diverse applications for advancing optical nanodevices, sensors, and energy harvesting. An emerging route to realise perfect absorption is based on artificial ultrathin nanosurfaces, known as “metasurfaces”.1 We describe a versatile metasurface fabrication strategy based upon gold (Au) selective deposition in block copolymer (BCP) templates towards perfect absorption. Since BCPs can be patterned over large wafer scale areas (i.e. 300 mm) and are industry compatible, they offer a viable path towards realising nanophotonic devices.2 Here, we describe a Au−Al₂O₃−Au stack layer for perfect absorption at visible frequencies using BCP templating. Our approach opens up a flexible methodology to precisely tune Au nanostructure height, e.g. 5-30 nm and resulting absorption wavelength range. The ability to tailor Au features precisely is extremely appealing and surpasses various wet chemical approaches that cannot be processed in thin film form. We will present key experimental parameters guided by numerical simulations to show the effect of Au height and stack architecture on absorption properties.

1. A. Alvarez-Fernandez, et. al., Nanoscale Adv., 1, 849–857 (2019).
2. C. Cummins et. al. Advanced Materials 28 (27), 5586-5618 (2016).