Coulomb sink: a novel Coulomb effect on coarsening of metal nanoclusters on semiconductor surfaces

We propose the concept of a ‘‘Coulomb sink'' to elucidate the effect of Coulomb charging on coarsening of metal mesas grown on semiconductor surfaces.We show that a charged mesa, due to its reduced chemical potential, acts as a Coulomb sink and grows at the expense of neighboring neutral mesas. The theory explains qualitatively the most salient features of coarsening of charged Pb mesas on the Si(111) surface, as observed by a scanning tunneling microscope. It provides a potentially useful method for controlled fabrication of metal nanostructures.