Surface-Enhanced Raman Scattering Stimulated by Strong Metal-Molecule Interactions in a C Single-Molecule Junction.

Specifying the geometric and electronic structures of a metal-molecule interface at the single-molecule level is crucial for the improvement of organic electronics. A single-molecule junction (SMJ) can be used to investigate interfaces because it can be regarded as an elementary unit of the interface structure. Although considerable efforts have been made to this end, the detection of structural changes in SMJs associated with metal-molecule interactions remains challenging. In this study, we detected the surface-enhanced Raman scattering (SERS) signal originating from the metal-molecule interaction change induced by a local structural change in a C SMJ. This junction has attracted wide attention owing to its unique electronic and vibronic properties. We fabricated a C SMJ using a lithographically fabricated Au electrode and measured the SERS spectra along with the current-voltage (-) response. By continuous measurement of SERS for the C SMJ, we obtained SERS spectra dependent on the local structural change. The analysis of the - response revealed that the vibration energy shift originates from the change in the local structure for different Au-C interactions. Based on the discrimination of the states in accordance with the Au-C interaction, we found that the probability of SERS for geometry with a large Au-C interaction was enhanced.