Self-assembled growth and blue emission of a SiO_x-capped (x = 0.5-0.8) silicon nanowire array

A uniquely structured SiO_x-capped (x ≤ 0.5-0.8) Si nanowire array with strong blue emission, like a nanobeacon array, was fabricated using electroless metal (silver) deposition on a water plasma-treated Si wafer. Formation of the nanoscale light source array can be understood on the basis of a self-assembled localized microscopic electrochemical cell model and a diffusion-limited aggregation process. Photoluminescence spectral analysis reveals that the intensity of the broad blue-emitting luminescent band centred at around 435 nm strongly depends upon the irradiation of H₂O ⁺, HO⁺, and O⁺ ions, which are present in the water plasma. We attribute the blue PL band to the optical transition of the self-trapped excitons at the surfaces of SiO_x nanocaps. © 2005 IOP Publishing Ltd.