Growth and characterization of Si and Ge clusters on ordered C60 overlayers

Abstract

We use in situ fabricated ordered C60 overlayers on Si and Ge surfaces as templates to grow isolated Ge and Si clusters, respectively. The growth processes are monitored and characterized by scanning tunneling microscopy, Auger spectroscopy, and low energy electron diffraction. Si and Ge clusters nucleate in the interstices of the C60 layer, and reach a typical lateral size of ∼10 Å before coalescing. Auger spectra of small Si clusters show an enhanced contributions from states of s symmetry, reflecting nontetrahedral coordination of Si atoms in clusters. Room temperature tunneling spectroscopy of isolated clusters reveals an enlarged band gap consistent with the effect of quantum confinement, and a quantized conductance attributable to the Coulomb blockade phenomena in a tip/cluster/substrate double barrier junction.