STM observation of Coulomb staircase behavior through C60 clusters

Abstract Two samples of C60 clusters were prepared on highly oriented pyrolytic graphite (HOPG) substrate by thermal evaporation. One is ∼1 nm and the other is ∼15 nm in radius. The current flowing across C60 clusters was measured using scanning tunneling microscope in atmosphere at room temperature. Coulomb staircase behavior was successively observed in the current–voltage ( I – V ) characteristics. Interestingly, the capacitances between HOPG and C60 clusters, estimated from the I – V characteristics, were almost the same between these two samples. We discussed this result taking into account the relaxation and localization time of electrons injected into C60 clusters.