Abstract:
Silver (Ag) and gold (Au) are the widely used noble
metals for surface-enhanced Raman scattering (SERS) applications
in the visible range. However, owing to poor chemical stability of
silver and interband transition of gold, thereby hindering the
detection process, there has always been a need for an alternate
material that can provide intense and stable SERS signals by
overcoming the above shortcomings. In this work, we report
measurements from a SERS substrate based on a Au−Ag alloy as a
SERS-active nanolayer on pyramidal Si (P-Si) array surfaces.
Fabrication of the substrate is done by following a simple and costeffective
cosputter deposition method on a prepatterned Si surface
produced by a chemical etching process. By suitably integrating the
merits of SERS activity of Ag, the chemical stability of Au, and the
large field enhancement of P-Si, the alloy Au0.5Ag0.5@P-Si exhibits high SERS sensitivity, homogeneity, reproducibility, and chemical
stability far beyond those of the individual elements. Using rhodamine 6G (R6G) as a probe molecule, the Au0.5Ag0.5@P-Si substrate
shows an ∼28 times enhanced SERS signal as compared to that of pure Au@P-Si and ∼1.5 times that of pure Ag@P-Si. A detection
limit down to 10−9 M concentration of R6G is found in our case. Further, an aging study shows the stability of the SERS signal using
the proposed Au0.5Ag0.5@P-Si substrates even after a time span of 30 days.
