Metal–Semiconductor Contacts Induce the Charge-Transfer Mechanism of Surface-Enhanced Raman Scattering

A model metal–semiconductor–molecule–metal assembly has been designed for probing the charge-transfer (CT) mechanism of surface-enhanced Raman scattering (SERS). We measured the SERS of ZnO–PATP–Ag, Au–ZnO–PATP–Ag, and Cu–ZnO–PATP–Ag assemblies at excitation wavelengths of 514.5, 785, and 1064 nm. Our results demonstrate that the metal–semiconductor contact can alter the charge distribution through p-aminothiophenol (PATP) molecules. This is attributed to the chemical SERS enhancement mechanism with additional electrical transport properties within these assemblies. These inhibit the CT from the metal to the molecule, resulting in the different degrees to which CT contributes to the overall SERS enhancement of PATP.