Photoemission studies of the Na/Ge(111)-3x1 surface

Abstract

The electronic structure of a Na/Ge(111)3 x 1 surface was investigated by valence-band and core-level photoemission spectroscopy with synchrotron radiation. The two-dimensional energy-band dispersion of the surface Brillouin zone along (M) over bar-<(Gamma)over bar>-(K) over bar was mapped out. The experimental surface-state dispersions show a better agreement with the theoretical results for the buckled Seiwatz model than the extended Pandey model. The surface core-level shift of the (3 x 1) surface is explained on the basis of the buckled Seiwatz model. The (3 x 1) surface reveals more covalent bonding character than other Na-adsorbed surfaces at room temperature, and its surface Fermi level is close to the valence-band maximum.