Ultralow Broadband Reflectivity in Black Silicon via Synergy between Hierarchical Texture and Specific-Size Au Nanoparticles

Antireflectivity is one of the critical factors defining the performance of black silicon in optical, photothermal, photochemical, and optoelectronic applications. The photonic applications under visible light illumination are commonly tuned through surface texturing; however, their promising performance under longer wavelength ('1100 nm) requires either intrinsic lattice modifications or additional substance enhancement. Recent advances in microfabrication and material engineering have enabled in-depth exploration into the synergy between surface texturing and material reinforcement. In this study, black silicon with novel chimney-like hierarchical micro/nanostructures is fabricated via two-step reactive ion etching, and subsequently gold nanoparticles (Au NPs) are loaded on the black silicon by magnetron sputtering deposition. The micro/nanostructures result in synergy effect with the Au NPs on suppression of light reflection. An ultralow broadband reflection ('1%, wavelength 220–2600 nm) is achieved from the Au-loaded black silicon substrates. The impact of Au NPs and structural design such as size, spacing, shape, and etching duration on antireflectivity of black silicon is investigated. This study opens up new avenue for high-efficiency applications of black silicon in the fields of sustainable energy and photonics/microelectronics.