Angle-resolved photoemission study of the submonolayer phases of Pb on Ge(111)

The (√3 × √3 )R30° α and γ submonolayer reconstructions of the Pb/Ge(111) system have been studied with angle-resolved photoemission spectroscopy utilizing synchrotron radiation. The α phase consists of 1/3 monolayer (ML) of Pb adatoms in ${\mathit{T}}_4$ sites, whereas the γ phase consists of an equal mix of Pb (1/6 ML) and Ge (1/6 ML) adatoms, forming a mosaic phase. Dispersions of the adatom-induced surface states of the γ and α phases have been probed along the ΓM¯ and ΓKM¯ directions of the surface Brillouin zone. Our results indicate that despite their structural differences, the α and γ phases have essentially the same electronic structure. Comparisons are made between this system and prototypical metal/Si(111)-(√3 × √3 )R30° systems and with theory.