A Low-cost, Highly-stable Surface Enhanced Raman Scattering Substrate by Si Nanowire Arrays Decorated with Au Nanoparticles and Au Backplate

We present a facile and cost-effective manner to fabricate a highly sensitive and stable surface enhanced Raman scattering (SERS) substrate. First, a silicon nanowire array (SiNWA) is tailored by metal-assisted chemical etching (MaCE) method as a scaffold of the desired SERS substrate. Next, with an oblique angle deposition (OAD) method, optimized gold nanoparticles (AuNPs) are successfully decorated on the surface of the SiNWA. These AuNPs enable a strong localized electric field, providing abundant hot spots to intensify the Raman signals from the targeting molecules. By applying a well-established methodology, Taguchi method, which is invented for designing experiments, the optimized combination of parameters is obtained efficiently. The experimental results are also confirmed by finite-difference time-domain (FDTD) simulation calculations. Besides, a gold metal backplate (AuMBP) is applied to further enhancing the Raman signal intensity. Based on this developed SERS substrate, we demonstrated an enhancement factor (EF) of 1.78 × 10(6) and a coefficient of variation (CV) of 4.2%. Both EF and CV indicate a highly stable property and the optimized SERS substrate substantially outperform the commercial product. In the end, we also demonstrate a quantitative measurement on practical application of detecting malachite green (MG) with concentration from 10 nM to 100 μM.