Silicon Nanowires Decorated with Au Nanoparticles and Their Spectroscopic Properties

Au nanoparticles (AuNPs) were loaded on silicon nanowires (SiNWs) via the redox reaction between HAuCl4 and HF-treated SiNWs in the presence of hexanethiol as stabilizer. As a result, AuNPs/SiNWs composites with AuNPs of varied sizes from 3.2 to 7.0 nm were obtained by adjusting the HAuCl4 concentration. The absorption and emission properties of the AuNPs/SiNWs were investigated by UV-visible and fluorescence spectroscopy methods. UV-vis spectra indicated that the AuNPs/SiNWs composites had absorption bands ranging from 530 to 580 nm, which were attributed to the AuNPs surface plasmon resonance (SPR). The SPR band was observed to red-shift with increase of the AuNPs size. Fluorescence spectra indicated that the fluorescence profile and peak position of the AuNPs/SiNWs were not changed significantly compared to the HF-treated SiNWs in the red and green regions. In the blue region, however, different from as-grown SiNWs and the HF-treated SiNWs with an emission at around 464 nm, an intense fluorescence band was observed at 423 nm, which was supposed to result from radiative recombination of Fermi level electrons and sp- or d-band holes in AuNPs.