Charge Transfer in an Ordered Ag/Cu2S/4-MBA System Based on Surface-Enhanced Raman Scattering

In this study, we introduced an ordered metal–semiconductor–molecular system and investigated the surface-enhanced Raman scattering (SERS) effect. The carrier distribution and density can be easily monitored by changing the thickness of the Cu2S film on the surface of the Ag monolayer under different laser excitations. Meanwhile, different laser wavelengths were selected for investigating the enhancement mechanism of the system based on the viewpoint of the number of carriers and changes in the excitation energy. During this process, we found that the SERS peaks located at 1586 cm–1 changed significantly because the intensity can be “borrowed” from exited transition and the molecule-to-semiconductor transition. In combination with the theories of Albrecht and Lombardi, this phenomenon was analyzed in detail, and the experimental results and theoretical research match well. This research regarding the semiconductor-based SERS substrates will expand the basic theory of SERS enhancement and provide a theoret...