Periodic arrays of nanopores made on single-crystalline silicon substrates with a self-assembled lithographic process

We report here the fabrication of periodic arrays of size- shape-, and spacing-controllable Si nanopores on single-crystalline (110)Si and (111)Si substrates by using our proposed approach, which is based on the self-assembled polystyrene nanosphere lithography in conjunction with the use of oxygen plasma treatments and KOH anisotropic etching processes. Compared with other works, the facile approach proposed here offers a much simpler and low-cost scheme which does not require the use of additional metal-film hard masks deposition and stripping processes. By adjusting the KOH etching duration, the Si nanopore size can be effectively tuned and controlled. The Si nanopores formed on (110)Si and (111)Si were found to be heavily faceted, and their faceted morphologies were mainly determined by the crystal orientations of the Si substrates used. Furthermore, the results of the ultraviolet-visible spectroscopic measurements revealed that the (110)Si substrate with nanopore arrays exhibited significant antireflection properties, and its optical reflectance was found to decrease with increasing the etched nanopore size. The obtained results present the exciting prospects that the combined approach presented here could have significant potential for use in Si-based optoelectronic devices.