Tunneling-induced luminescence from adsorbed organic molecules with submolecular lateral resolution

Light emission from molecule-covered surfaces in the scanning tunneling microscope has repeatedly been reported with optical contrast occurring on a molecular scale. The role of the molecules in the emission is unclear although molecular fluorescence has been suggested. Here, simultaneous optical spectroscopy and spatial mapping of the emission from single hexa-tert-butyl-decacyclene molecules on noble-metal surfaces are combined and submolecular constrast is observed. However, the emission spectra are indicative of plasmon mediated emission of the metal substrate and tip while the molecule merely acts as a spacer, which slightly modifies the plasmon emission.