Silver nanosphere array substrates fabricated by glancing angle deposition: Morphology, hot spots and SERS properties

The generation and exploitation of hot spots play a crucial role in the fabrication of highly sensitive surface-enhanced Raman scattering (SERS) substrates. In this work, silver nanosphere (AgNS) array substrates with various morphologies of polystyrene (PS) core/Ag shell were fabricated by reactive ion etching and glancing angle deposition technique on PS sphere templates. The electromagnetic field distribution (hot spots) of AgNS array was calculated by the finite difference time domain method. R6G and MB were used as probe molecules to investigate the effect of structure spacing on electric field enhancement. Under 785 nm excitation, an AgNS substrate with a gap of approximately 20 nm exhibited the best SERS enhancement, and the limit of detection reached 5 x 10-8 M for both analytes. For R6G and MB, the relative standard deviations (RSDs) were 2.39 % and 7.22 %, and the enhancement factors (EFs) were 7.25 x 108 and 7.68 x 107, respectively. These results serve as a reference for the development of new highly sensitive SERS sensors.