News Report
Tip-enhanced Raman scattering from an atomic point contact
Sep 2020

Tip-enhanced Raman scattering (TERS) combined with highly stable scanning tunneling microscopy is a powerful tool to obtain local chemical information at surfaces with exceptional high spatial resolution. Here, we investigate the evolution of TERS at Angstrom-scale distances between tip and surface up to the point where tip apex touches the surface. A stable atomic point contact is reversibly formed in the junction between our plasmonic Ag tip and ultrathin ZnO films on a Ag(111) surface. A dramatic enhancement and abrupt increase of the TERS intensity occurs upon contact formation for ZnO, which attributed to strong hybridization between the Ag tip and ZnO enhancing the Raman polarizability. This is further corroborated by the appearance of a new vibrational mode arising from the atomic contact. In contrast, related control experiments on chemically inert NaCl films show no such enhancement and the absence of the point contact mode.