Formation and control of Ultrasharp metal/molecule interfaces by controlled immobilization of size-selected metal Nanoclusters onto organic molecular films

The formation of metallic layers on ultrathin molecular films via a well-controlled interface is essential for constructing organic nanodevices composed of metal/molecule/metal sandwich junctions. The scanning tunneling microscopy and spectroscopy studies demonstrate that an ultrasharp metal/molecule interface is realizable by depositing size-selected Ag nanoclusters (Ag_n) from the gas phase on few-layer films of C ₆₀ molecules. It is also demonstrated that Ag_n nanoclusters can be immobilized on monolayer films of oligothiophene molecules via C₆₀ molecules, although they three-dimensionally aggregate on bare oligothiophene films. It is also shown that electrons and holes are injected into the topmost layer of C₆₀ films via the Ag _n/C₆₀ interface. Moreover, the barrier height for carrier injection at the Ag_n/C₆₀ interface can be modified depending on the size of Ag_n nanoclusters and the kinetic energy during the deposition. The present results demonstrate that the controlled immobilization of metallic nanoclusters on molecular films can be used as a fabrication technology for metal/molecule/metal junctions. Metal/molecule heterojunctions are constructed by the controlled immobilization of size-selected Ag nanoclusters (Ag_n) from the gas phase on ultrathin C₆₀ films. In such heterojunctions, electrons and holes can be precisely injected into the topmost C₆₀ molecules in films via an atomically abrupt metal/molecule interface. The barrier height for carrier injection can be modified.