Pillar-cap shaped arrays of Ag/SiO 2 multilayers after annealing treatment as a SERS—active substrate

Abstract The “pillar-cap” shaped arrays of Ag/SiO 2 multilayers were prepared on 2D PS template by sputtering Ag and SiO 2 materials alternatively. Annealing under argon accelerated the interface diffusion between Ag and SiO 2 sublayers. Some Ag nanoparticles squeezed into SiO 2 sublayer through the pinholes in SiO 2 sublayer and the corona-like structure consisting of SiO 2 -trapped Ag nanoparticles formed on the surfaces of the pillar-cap arrays. The sizes of Ag nanoparticles varied from 2 nm to 5 nm, depending on the annealing temperature. The separations of 1–2 nm SiO 2 were generated between Ag particles and underlying Ag sublayer, which provided a lot of hot spot sites for SERS. This fabrication method could avoid the unnecessary and cumbersome stages in chemical surface modification, which made the substrate a promising candidate for the SERS detection.