Subwavelength Antireflective Si Nanostructures Fabricated by Using the Self-Assembled Silver Metal-Nanomask

We report a lithography-free approach for fabricating silicon nanopillars (Si-NPs) and biomimetics porous silicon (P-Si) with excellent antireflective properties. The self-assembled silver nanostructures (nanoislands and disordered nanogrids) were formed via the Volmer-Weber (island growth) mode during the deposition process, which, in turn, serve as a metal-nanomask for the subsequent dry etching process carried out for fabricating the Si-NPs and P-Si on Si substrates. Reflectivity of about 0.65% was obtained over the spectral region ranging from deep-ultraviolet to infrared light (300-1000 nm). The remarkable antireflective characteristics obtained are attributed to the drastic decrease of effective index of refraction and the enhanced matching effect between air and substrate resulting from the Si nanostructures and suggesting an interesting alternative route for producing nanostructures that might be useful for photovoltaic applications.