Formation and mechanism of silicon nanostructures by Ni-assisted etching

Instead of noble metal like Pt, Au and Ag, cheap Ni nanoparticles (Ni NPs) were used to fabricate silicon nanostructures. Ni was found to be etched off during the etching process, while forming silicon nanostructures with very low reflectance of 1.59 % from 400 to 900 nm. The formation mechanism of silicon nanostructures by Ni-assisted etching was presented from the point of view of the low electronegativity of Ni. The Ni NPs were found being etched off during the assisted etching process, which implies that the transfer rate of electrons from Si to Ni is slower than that from Ni to O− in the case of using Ni as assisted metal. The reason of sparser and deeper silicon nanostructures etched in lower H2O2 concentration solution is that the Ni NPs can be lasted for longer time in the etching solution with lower H2O2 concentration so that more silicon atoms will be oxidized and then removed for those under Ni NPs due to the hole transfer and those where uncovered by Ni NPs due to the hole diffusion.