Metallization of Silicon Nanowires and SERS Response from a Single Metallized Nanowire

Abstract

A simple method was demonstrated to metallize silicon (Si) nanowire (NW) just by dipping it into an aqueous deposition solution for several minutes. During the metallization process, metal ions were reduced and deposited on the top of the Si NW (where surface Si was oxidized). The surface silicon oxide was simultaneously dissolved and removed by hydrogen fluoride (HF), so that the deposition reaction was sustainable and controllable. The deposited silver (Ag) nanoparticles (NPs) uniformly self-assembled along the Si NW and developed into a metal covering with the NW as its core. Not only Ag + but also Cu 2+, Pd 2+, Co 2+, Au 3+, and Pt 4+ were deposited to metallize the Si NW using the simplified metallization process. Applications of the new nanocomposite materials were also explored. When the resulting Ag NP/Si NW was tested as a surface-enhanced raman scattering (SERS) substrate, an extremely strong signal was observed and a detection limit of ∼600 molecules or 200−300 Ag NPs per laser spot was reached. The significantly enhanced SERS effect appears to be associated with the close packing of the neighboring NPs that self-assemble along the highly curved NW.