Single-Molecule STM Studies on Atomically-Flat Nanoparticles*

The scanning tunneling microscope (STM) has been broadly applied to measure electronic characteristics of individual molecules supported in an inert monolayer matrix, which is typically grown on gold thin films on mica or bulk single crystal substrates. Although these substrates are excellent for electronic measurements, they have serious disadvantages for optical measurements because they are not optically transparent and the metal surface can quench the molecular excited state. We demonstrate that single molecule electronic measurements can also be performed using atomically-flat gold nanoparticles (FGNPs) supported on indium tin oxide coated glass as a replacement for the typical gold substrate. These substrates are optically transparent and each of the FGNP ``nanosubstrates'' is an optically resonant photonic antenna, thus they have the added advantage that optical measurements can be performed.