Vibronic spectroscopy of single C60 molecules and monolayers with the STM

A scanning tunneling microscope is used to study the differential conductance (dI/dV) of single C(60) molecules in isolation and in monolayers adsorbed on NiAl(110) and on an ultrathin alumina film grown on the NiAl(110) surface. On the oxide layer, the electronic bands in the dI/dV spectra display a series of equally spaced features, attributed to the vibronic states of the molecules, which are absent when the molecules are adsorbed on the metal. A comparison between the molecular spectra measured on the oxide film reveals the effect of adsorption temperature and geometry, as well as intermolecular interactions on the vibronic features.