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 (√ 3 x √ 3)R30° honeycomb superstructure on surface. The possibility for formation of Si(111)(√ 3 x √ 3)R30°-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.