Free-standing Ag triangle arrays a configurable vertical gap for surface enhanced Raman spectroscopy.

Large-area ordered arrays with dense hotspots are highly desirable substrates for surface enhanced Raman scattering (SERS). In this paper, we present a quasi-3D SERS substrate of free-standing Ag triangle arrays (FATA) which was fabricated by nanosphere lithography incorporated with photolithography and Ag covering. A significant SERS effect arises from a strongly enhanced local electric field within the tiny gaps between the suspended Ag triangle and the Ag baseplate. The SERS intensity relative standard deviation is less than 7.6%, leading to excellent reliability for Raman detection. The simple fabrication of the Ag film covering FATA nanostructures provides a practical solution for large-area, highly efficient and reproducible SERS substrates.