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Fabrication of black silicon by Ni assisted chemical etching

In this paper, Ni was used as an assist metal to fabricate black silicon. Ni nanoparticles were first deposited on the surface of the hydrophilic silicon wafer by chemical solution deposition. Then the silicon wafer with Ni nanoparticles on its surface was etched in a HF/H2O2/H2O mixed solution at room temperature. The concentration of HF in the solution was changed to study the reaction principle of Ni assisted chemical etching. A reflectivity as low as 2.31% in the wavelength range of 400–900 nm was obtained in optimized condition. An ‘inverted pyramid + nano-pore’ structure could be formed when the etching time was long enough because of the corrosion of Ni nanoparticles by etching solution. Besides, the corrosion direction of the Ni assisted etching was found to be perpendicular to the surface of the silicon wafer.