Silicon Nanowire Arrays Combining Nanosphere Lithography and Metal-Assisted Etching

Arrays of vertically aligned Silicon nanowires (SiNWs) were obtained using a top-down multistep method that combined nanosphere lithography and metal-assisted etching of bulk Si. This combined technique is a very simple and fast preparation method, which enables the formation of large-scale arrays with long-range periodicity of vertically standing nanorods/nanowires with well-controlled diameter, length and density. After deposition of a monolayer of polystyrene (PS) spheres with a diameter of 200 or 100 nm, on a Si wafer, they were subjected to a reactive ion etching treatment in oxidizing atmosphere. The PS spheres were used as a mask to deposit a thin layer of gold (Au) on Si, between the spheres. The etching occurring preferentially at the interface between Au and Si, the Si surface protected by the spheres was not dissolved resulting in free standing SiNWs. Progress made in the development of the multistep method was reported, enabling the formation of SiNWs with uniform diameter as small as 60 nm.