Preparation and SERS performance of gold nanoparticles-decorated patterned silicon substrate

Noble metal nanoparticles (NPs) are frequently utilized in surface-enhanced Raman scattering (SERS) due to their localized surface plasmon resonance (LSPR) effect, whose preparation in high density and suitable size is a prerequisite for high enhancement factors and homogeneity of SERS substrates. Here, a method combining femtosecond (fs) laser direct writing silicon with solid-state dewetting of Au nanofilm was proposed. Patterned silicon with nanostructures modulates the solid-state dewetting of Au nanofilm deposited on its surface by structural curvature, resulting in the formation of patterned silicon decorated with Au-NPs (Au-NPs/PSi). The Au-NPs formed on the patterned silicon are denser and have a 72 nm average diameter better suited to SERS compared to the flat silicon. By the simulation of finite-difference time-domain (FDTD) method, we found the significantly enhanced local electric field in the nanogaps between Au-NPs and between Au-NPs and silicon. Furthermore, the substrate shows excellent SERS ability in detecting R6G molecules, with detection limit as low as 10-10 M and an enhancement factor (EF) of 2.68 x 107. The results indicate that Au-NPs/PSi substrate is a promising candidate for obtaining reliable and high-quality SERS, promoting the application of SERS in trace molecules detection in solution.