Observation of electron localization in rough gold nanoclusters on the graphite surface

The results of scanning tunneling spectroscopy of the electronic states of Au nanoclusters on the graphite surface are presented. The tunneling current is found to be different at different points of a rough-surface nanocluster. The measured differential current-voltage curve of the clusters is nonmonotonic near the Fermi energy, and the tunneling conductance decreases by almost a factor of two as the cluster volume changes from 1 to 0.1 nm³. This decrease can be associated with the change in the density of the electronic states near the Fermi energy. The observed features are qualitatively described within the framework of the mechanism of electron localization in disordered systems.