Slope-tunable Si nanorod arrays with enhanced antireflection and self-cleaning properties

Slope-tunable Si nanorod arrays (NRAs) were fabricated with colloidal lithography and reactive ion etching (RIE). Sharpened NRAs fabricated by increasing the SF₆/O₂ flow ratio during RIE exhibit enhanced antireflection (AR) and hydrophobic properties, which are attributed to the smooth gradient in the effective refractive index of NRAs, and the enlarged water/air interface of the water drops in the NRA layers, respectively. Enhanced AR characteristics via modifying the slope of NRAs are accompanied by broad-band working ranges, omnidirectionality, and polarization insensitivity. Detailed experimental and theoretical analysis of slope-tunable NRAs should benefit the development of various self-cleaning optoelectronic devices with efficient light management.