Fabricating Silver Nanoparticles on Thin Silicon Nanowalls for Highly Sensitive Surface-Enhanced Raman Scattering

Abstract

Metal nanoparticles with nanoscale spacing are promising materials for the detection of single molecules through surface-enhanced Raman scattering. To increase the sensitivity of nanoparticles through the use of a nanoscale substrate, we fabricated various Ag NP–decorated silicon nanowalls for the Raman spectroscopic detection of rhodamine 6G (R6G). The sensitivity of detection was affected by the nanowall depth and was influenced by several parameters: the AgNO₃ concentration for metal-assisted etching, the HF/H₂O₂ etching time for nanowall formation, and the Ag evaporation time for nanoparticle growth. For an approximately 400-nm-deep nanowall substrate having the optimal surface filling ratio and etching depth, we obtained an ultrahigh enhancement factor of 1.1 × 10⁹ for the detection of R6G at a concentration of 10⁻¹¹ M.