Cluster-Induced Reactions at a Metal-Semiconductor Interface: Ce on Si(111)

Synchrotron-radiation photoemission, angle-resolved Auger, and LEED studies show Ce cluster formation on Si(111). These nonmetallic clusters grow for coverages of 0.1 to 0.6 monolayer, interact weakly with the substrate, and induce 200-meV band-bending changes. At ∼ 0.6 monolayer, they stimulate surface disruption, producing a metallic interfacial silicide. The association of $d$- or $f$-band metal clusters with surface reaction substantially extends the cluster-induced-reaction model proposed for Al-GaAs.