Dependence of Charge Transfer on the Adsorption Site at Metal–Molecule Interfaces: Implications for Single-Molecule Electronic Devices

Charge transfer at metal–molecule interfaces plays a decisive role in nanomaterials especially for electronic applications; however, its knowledge at the single-molecule level remains elusive. Herein, we found a highly conductive adsorption site in a single-molecule junction (SMJ) of naphthalenedithiol by a combination of surface-enhanced Raman scattering (SERS) and current–voltage measurements. The vibrational energy and conductance reveal that the high conductivity originates from the adsorption site with large charge transfer. The present study demonstrates that SERS combined with transport measurements reveals not only structures of SMJs but also charge transfer at the metal–molecule interfaces.