Capacitance dependence of chemical potential distribution in supported nanoclusters

We investigate the capacitance dependence of the chemical potential distribution of Au nanoclusters supported on hexanedithiol/Au(1 1 1) substrate by scanning tunneling spectroscopy. It is shown that the average of the chemical potentials, which correspond to the electron affinity and the ionization potential of the cluster, distributes around the level nearly equal to the Fermi energy of the grounded substrate. The total capacitance of the clusters towards the environment significantly affects the deviation of the distribution, which becomes smaller with decreasing total capacitance. The analysis in the capacitance range of 0.1 aF–2 aF in detail clearly exhibits the transition in the charge neutrality of the supported clusters.