Fabrication of silicon nanostructures with various sidewall profiles and sharp tips

We report a simple but effective method to fabricate high-aspect-ratio silicon nanostructures with ∼230 nm pitch (i.e., period) using interference lithography followed by deep reactive ion etching (DRIE). Sidewall profiles of nanograting and nanopost patterns are controlled through etching parameters of DRIE. We also show that tips with a pointed and re-entrant profile can be created. The tip can further be sharpened by thermal oxidation and subsequent wet etching of the oxide. Nanostructures with various sidewall profiles and sharp tips open new application possibilities not only in electronics but also in other engineering and general areas.