Fabrication of single-crystalline silicon nanowires by scratching a silicon surface with catalytic metal particles

A novel strategy for preparing large-area, oriented silicon nanowire (SiNW) arrays on silicon substrates at near room temperature by localized chemical etching is presented. The strategy is based on metal-induced (either by Ag or Au) excessive local oxidation and dissolution of a silicon substrate in an aqueous fluoride solution. The density and size of the as-prepared SiNW's depend on the distribution of the patterned metal particles on the silicon surface. High-density metal particles facilitate the formation of silicon nanowires. Well-separated, straight nanoholes are dug along the Si block when metal particles are well dispersed with a large space between them. The etching technique is weakly dependent on the orientation and doping type of the silicon wafer. Therefore, SiNWs with desired axial crystallographic orientations and doping characteristics are readily obtained. Detailed scanning electron microscopy observations reveal the formation process of the silicon nanowires, and a reasonable mechanism is proposed on the basis of the electrochemistry of silicon and the experimental results.