Polarized SERS substrates with directionality, repeatability and orderability: an anisotropic Ag nanocavity array

This paper reports the design and fabrication of an anisotropic Ag nanocavity array, which mainly uses magnetron sputtering and ion beam etching techniques to get the ordered Ag nanocavity array on the polystyrene templates. The nanocavity array can be used as an active substrate for polarized Raman scattering to eliminate polarization-independent background clutters. By controlling the etching angle of the ion beam and the film thickness of the sample, the size of the Ag nanocavity and the position of hot spots can be tuned. The polarized extinction spectra and the polarization Raman test further show the anisotropy of the nanocavity array, which leads to angle-dependent SERS observations. The three-dimensional simulation results of the polarized electric field are consistent with the polarized Raman spectroscopy results, and the fundamental reason for the response of an anisotropic nanostructure to polarized light is found. The angle-dependent SERS excited by polarized light is used to eliminate the background signals, which finally leads to improved SERS signals.