Discrete charging effects in gold nanoclusters grown on self-assembled monolayers

Single electron charging effects were observed for gold nanoclusters grown on octanedithiol self-assembled monolayers by scanning tunneling microscopy and X-ray photoelectron spectroscopy (XPS). Strong interaction of gold with the terminal sulfur atoms of dithiol molecules on Au(111) suppresses effectively the penetration of deposited gold atoms through the dithiol layer and results in the formation of uniform metal nanoclusters. Decoupling of the clusters from Au(111) by the octanedithiol layer and the small self-capacitance of the nanoclusters realize the observation of the Coulomb blockade in scanning tunneling spectroscopy and the Au 4f core level shifts in XPS at room temperature. Both phenomena originate from a common physics, the Coulomb energy of charged particles.