STM-induced photon emission at solid–liquid interface

We extended Scanning Tunnelling Microscopy (STM)-induced photon emission from metal surface to solid–liquid interface. A Au(111)–Au junction immersed in a liquid droplet was studied. We observed a decrease of the voltage threshold for photon emission when adding liquid compared to air medium and a strong decrease of the apparent tunnel barrier height and a parallel behavior for photon emission. This is attributed to the refractive index of the liquid. Our observations permit to investigate the influence on STM-induced photon emission of a self-assembled molecule monolayer formed on a Au(111) substrate.