Si(111)7×7-Ge and Si(111)5×5-Ge surfaces studied with angle-resolved photoemission

Angle-resolved photoelectron spectroscopy has been used to study the surface electronic structure of Si(111)7×7-Ge and Si(111)5×5-Ge surfaces. For the Si(111)7×7-Ge surface, three surface-state structures were observed at energies -0.20 eV ($A_1$), -1.0 eV ($A_2$), and Å -1.4 eV ($A_3$) relative to the Fermi level. For the Si(111)5×5-Ge surface, two surface-state structures were identified at -0.12 eV ($B_1$) and Å -1.2 eV ($B_3$), respectively. The $A_3$ and $B_3$ surface states show a downward initial-energy dispersion along the $\overline{\Gamma }-\overline{K}$ line in the 1×1 surface Brillouin zone, with an observed bandwidth of Å0.35 eV. The results are compared with those obtained for the clean Si(111)7×7 surface.