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 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 possibility to determine molecular chemical structure by optical imaging at only a single molecule. The second phenomenon is single-molecule electroluminescence (SMEL) . Our recent research on its excitation mechanism and single-photon emission behavior will be briefly presented. I shall also demonstrate how sub-nanometer resolved electroluminescence imaging can be used to gain insights into the intramolecular vibronic coupling and intermolecular dipole-dipole coupling in real space.
1. R. Zhang, Y. Zhang, Z. C. Dong*, S. Jiang, C. Zhang, L. G. Chen, L. Zhang, Y. Liao, J. Aizpurua, Y. Luo, J. L. Yang, and J. G. Hou*, Naturem 498, 82-85 (2013).
2. Y. Zhang, Y. Luo, Y. Zhang, Y. J. Yu, Y. M. Kuang, L. Zhang, Q. S. Meng, Y. Luo, J. L. Yang, Z. C. Dong*, and J. G. Hou*, Nature531, 623-627 (2016).