Conductance Modulation in an α-Terthiophene Molecular Junction Characterized by Surface-Enhanced Raman Scattering

Abstract

We fabricate α-terthiophene single-molecule junctions (SMJs) and characterize their conductive states by the simultaneous measurements of surface-enhanced Raman scattering (SERS) and electronic conductance. The α-terthiophene SMJ showed broad conductance distribution due to the different portions of the multiple aromatic rings connected to the electrodes. SERS spectra obtained by the simultaneous measurement showed the vibrational energy of the C−C stretching mode depends on the conductance. The Raman spectra calculated by the density-functional theory (DFT) explain the tendency of the vibrational energy shift for typical junction structures. Therefore, the SERS measurement and DFT calculation have revealed that conductance modulation originates from the change in the connecting point of the α-terthiophene SMJ. These findings provide efficient information for building molecule-based circuits and lead to molecule-based potentiometry with aromatic rings.