Delocalized Surface State in Epitaxial Si(111) Film with Spontaneous √3 x √3 Superstructure

The multilayer silicene films were grown on Ag(111), with increasing thickness above 30 monolayers (ML). Scanning tunneling microscopy (STM) observations suggest that the multilayer silicene is indeed a bulk-like Si(111) film with a (root 3 x root 3)R30 degrees honeycomb superstructure on surface. The possibility for formation of Si(111)(root 3 x root 3) R30 degrees-Ag reconstruction on the surface can be distinctively ruled out by peeling off the surface layer with the STM tip. On this surface, delocalized surface state as well as linear energy-momentum dispersion was observed from quasiparticle interference patterns. Our results indicate that a bulklike silicon film with diamondlike structure can also host delocalized surface state, which is even more attractive for potential applications, such as new generation of nanodevices based on Si.