Evaluation of SERS activity for cosputtered Ag-ZnX@PS (X = O, S, Se) composites: Carrier density dependence

Ag-ZnX (X = O, S, Se) composites coated on polystyrene (PS) arrays (Ag-ZnO@PS, Ag-ZnS@PS, Ag-ZnSe@PS) were successfully fabricated by using cosputtering technology. We found that ZnX doping decreased the carrier densities of these composites compared to that of pure Ag@PS, which was due to redistribution of electrons between Ag and ZnX. Thus, the carrier density of Ag was decreased, and the surface plasmon resonance (SPR) of Ag was redshifted in the Ag-ZnX composites. As the redshift of the SPR of Ag induced a high SPR contribution to the surface-enhanced Raman scattering (SERS), the SPR and charge transfer (CT) contributions were simultaneously increased with increasing carrier density in the Ag-ZnX composites. This study opens a new path to designing metal-semiconductor composites with controllable carrier density. Regulation of the carrier density will be of great help in understanding SPR and CT contributions.