Antireflection Properties of Multi-crystalline Black Silicon with Acid Textured Surfaces Using Two Step Metal Assisted Chemical Etching

We have fabricated multicrystalline black silicon (B-Si) with two step texturing process, first using micro-scale conventional acid texturing and second using nano-textured (nT-Si) layer, directly on the micro textured surface. Instead of Lithography process, a two step silver assisted chemical etching process, is used to fabricate nano-texture surfaces in the aqueous solution of hydrogen peroxide (H2O2) and hydrofluoric acid (HF) at room temperature. The reflectivity has been investigated with the varying time of the nano-texturization. The surface morphology of nano-textured black Si was studied by SEM and the optical properties were studied by spectrophotometer. The average reflectivity has decreased to 4.3 % in wavelength range from 300 to 800 nm.