Spatially resolved observation of Coulomb blockade and negative differential conductance on a Ag cluster on the clean GaAs(110) surface

By performing current-image tunneling spectroscopy at room temperature, we have observed the staircase current–voltage $\mathrm{(I–V)}$ characteristic and negative differential conductance on a single Ag cluster on a clean GaAs(110) surface. The $\mathrm{I–V}$ characteristics have changed spatially with the position of the tip on the cluster. The characteristics are understood in terms of Coulomb blockade and resonance of electron standing-wave states in the cluster with the states of the underlying substrate.