Effects of Ag contents on the microstructure and SERS performance of self-grown Ag nanoparticles/Mo-Ag alloy films

Ag nanoparticles/Mo-Ag alloy films with different Ag contents were prepared on polyimide by magnetron sputtering. The effects of Ag contents on the microstructure of self-grown Ag nanoparticles/Mo-Ag alloy films were investigated using XRD, FESEM, EDS and TEM. The Ag content plays an important role in the size and number of uniformly distributed Ag nanoparticles spontaneously formed on the Mo-Ag alloy film surface, and the morphology of the self-grown Ag nanoparticles has changed significantly. Additionally, it is worth noting that the Ag nanoparticles/Mo-Ag alloy films covered by a thin Ag film exhibits highly sensitive surface-enhanced Raman scattering (SERS) performance. The electric field distributions were calculated using finite-difference time-domain analysis to further prove that the SERS enhancement of the films is mainly determined by "hot spots" in the interparticle gap between Ag nanoparticles. The detection limit of the Ag film/Ag nanoparticles/Mo-Ag alloy film for Rhodamine 6G probe molecules was 5 x 10(-14) mol/L. Therefore, the novel type of the Ag film/Ag nanoparticles/Mo-Ag alloy film can be used as an ideal SERS-active substrate for low-cost and large-scale production.