The adsorption of ${\mathrm{C}}_{60}$ on a bilayer film of pentacene on Ag(111) is studied with scanning tunneling microscopy and spectroscopy. At low coverage, ${\mathrm{C}}_{60}$ molecules form extended linear structures due to the templating effect of the pentacene bilayer. The ${\mathrm{C}}_{60}$ molecules in the chains adsorb at bridge sites between two neighboring pentacene molecules. The transport gap of the chain structures is measured to be $4.5\pm 0.2\mathrm{eV}$ using constant-current distance-voltage spectroscopy. The magnitude of the gap is correlated with the uniquely low coordination of the linear fullerene structures, which leads to a reduced total polarization contribution compared to bulk ${\mathrm{C}}_{60}$.

• Received 9 November 2007

DOI:https://doi.org/10.1103/PhysRevB.77.073414