Morphology control of ordered Si nanowire arrays by nanosphere lithography and metal-assisted chemical etching

Metal-assisted chemical etching (MACE) using a nanosphere lithography (NSL) technique is regarded as a general fabrication method for silicon nanowire (SINW) arrays. However, morphology control of SiNWs using this method has not been reported. In this study, silicon nanowire (SINW) and silicon nanocone (SINC) arrays were fabricated by MACE using a NSL. Depending on the concentration of etchants in the etching solution, the morphology of the wires and etching rate were systemically changed. At high concentrations, the wires were etched cylindrically and at low concentrations, tapered (cone-like) wires were obtained. To quantify the degree of tapering, the volume ratio of the etched part was calculated from their morphology. The degree of tapering increased as the concentrations of etchants decreased. We suggest that the mechanism of the formation of nanocone is related to the degree of hole diffusion under the metal layer, which was supported by field emission scanning electron microscope (FE-SEM) images. (C) 2014 The Japan Society of Applied Physics