Zhenchao Dong（University of Science and Technology of China）

「STM-based single-molecule optoelectronics」

Control of optical properties of single molecules by plasmonic nanostructures is an important issue in plasmonics and nanophotonics, particularly valuable for the development of molecular optoelectronic devices and ultrasensitive high-resolution microscopic techniques. The nanocavity defined by the coinage-metal tip and substrate in a scanning tunneling microscope (STM) can provide highly localized and dramatically enhanced electromagnetic fields upon proper plasmonic resonant tuning, which can modify the excitation and emission of a single molecule inside and produce intriguing new optoelectronic phenomena. In this talk, I shall demonstrate two STM-based phenomena related to single-molecule optical spectroscopy. The first phenomenon is single-molecule Raman scattering. The spatial resolution of tip enhanced Raman spectromicroscopy has been further driven down to a single chemical-bond scale. Such simultaneous energetically and spatially resolved capability for vibrational-mode mapping opens up a new route to determine molecular chemical structure by optical imaging at only a single molecule. The second phenomenon is single-molecule electroluminescence (SMEL). Following a brief discussion on the excitation mechanism of SMEL, I shall demonstrate how sub-nanometer resolved electroluminescence imaging can be used to gain insights into the intramolecular vibronic coupling caused by the interaction between electronic and nuclear motions, unveiling in real space how molecular vibrations shape molecular wavefunctions and induce electronic transitions.