Biomimetic artificial Si compound eye surface structures with broadband and wide-angle antireflection properties for Si-based optoelectronic applications

Abstract

We report the biomimetic artificial silicon (Si) compound eye structures for broadband and wide-angle antireflection by integrating nanostructures (NSs) into periodically patterned microstructures (p-MSs) via thermal dewetting of gold and subsequent dry etching. The truncated cone microstructures with a two-dimensional hexagonal symmetry pattern were fabricated by photolithography and dry etching processes. The desirable shape and density of the nanostructures were obtained by controlled dewetting. The incorporation of p-MSs into the NS/Si surface further reduced the surface total reflectance over a wide wavelength range of 300–1030 nm at near normal incidence, indicating the average reflectance (R_avg) and solar weighted reflectance (R_SWR) values of ∼2.5% and 2%, respectively, compared to the only NSs on the flat Si surface (i.e., R_avg ∼ 4.9% and R_SWR ∼ 4.5%). Additionally, the resulting structure improved the angle-dependent antireflection property due to its relatively omnidirectional shape, which exhibited the R_avg < 4.3% and R_SWR < 3.7% in the wavelength region of 300–1100 nm even at a high incident light angle of 70° in the specular reflectance.