Fabrication of superhydrophobic wide-band “Black Silicon” by deep reactive ion etching

This paper presents a fabrication technology of “Black Silicon” with superhydrophobicity and wide-band properties based on an improved deep reactive ion etching (DRIE). By optimizing the fabrication parameters, including gas flows, pressure, platen power and etching/passivation time ratio, we have obtained dense arrays of nanopillars with an average diameter of ~400 nm and height of 2-2.5 μm. The sample surface shows completely black appearance (i.e., black silicon) after 15 - 20 minutes processing, which indicates an obviously strong light absorption. Further test indicates the optical reflectance has been reduced to below 1% over a broad wavelength range (i.e., spectrum from 200 nm to 2500 nm). Moreover, the black silicon surface shows superhydrophobicity and the static contact angle is ~157°. Double-sided black silicon surfaces are also fabricated by this improve DRIE process, and the measured optical reflectance is reduced during long-wave region and blew 4% during the whole wave length range.