Fabrication of size-tunable, periodic Si nanohole arrays by plasma modified nanosphere lithography and anisotropic wet etching

In this study, we propose a new, facile and efficient method to define the desired patterns on Si surfaces and to fabricate periodic arrays of size- and position-controllable Si nanoholes on blank- and pre-patterned (0 0 1)Si substrates, which is based on the O ₂ plasma modified nanosphere lithography with an anisotropic wet etching technique. In contrast to earlier approaches, no additional thin-film deposition equipments and metal film hard masks are needed for this method. The Si nanohole arrays exhibit the same hexagonal arrangement as the initial colloidal nanospheres template. The sizes of the Si nanoholes can be tuned from 150 nm to 480 nm by varying the etching time. The Si substrates with nanohole-textured surfaces exhibit strong antireflection properties. UV-Vis spectroscopic measurements revealed that by increasing the nanohole size, the optical reflectance of the nanohole-structured (0 0 1)Si surfaces was gradually decreased down to less than 8 %. Since the nanohole sizes, shapes and spacings can be readily controlled by adjusting the diameters of the colloidal nanospheres and anisotropic wet etching conditions, the combined approach presented here provides the capability to fabricate a variety of nanohole array structures on various Si-based substrates without complex lithography.