Gold thickness impact on the enhancement of SERS detection in low-cost Au/Si nanosensors

In this paper, we present a study on the optimization of Au/Si surface-enhanced Raman scattering sensors for ultrasensitive chemical detection. Au/Si nanosensors are carried out at the wafer scale with a low-cost and quick fabrication method composed of an anisotropic reactive ion etching followed by an electron beam evaporation of a gold layer. For this investigation, the thickness of the gold layer varied from 10 to 50 nm, and thiophenol molecules were chosen as model molecules of which the concentration varied from 10 - 12 to 10 - 3 M. The studied optimization exploits the effect of the gold layer thickness on the detection limit of thiophenol molecules for a fixed geometry of Si nanopillar. For all the cases investigated here, detection limits between 9 × 10 - 12 and 3 × 10 - 8 M are experimentally found for the detection of thiophenol molecules with the Au/Si nanopillars. Moreover, the best detection limits are achieved with the thickest gold layer. Finally, a 3D FDTD-based numerical analysis confirmed the experimental results.