LOW-TEMPERATURE PHOTOEMISSION-STUDY OF THE SURFACE ELECTRONIC-STRUCTURE OF SI(111)7X7

The electronic structure of the Si(111)7 x 7 surface has been studied in detail at a sample temperature of 55 K with high-energy-resolution angle-resolved photoemission. The photoemission spectra show a previou sly undetected surface-state structure at approximate to 0.5 eV below the Fermi level that we assign to dangling-bend states located mainly to the adatoms near the corner holes of the 7x7 reconstruction. Detail ed dispersion curves obtained at 55 K are presented for the three uppe rmost, dangling-bond derived, surface states. Surface sensitive Si 2p spectra obtained in this low-temperature study still show a comparativ ely broad line shape. Possible reasons for this are discussed.