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 T4 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 ΓM̄ and ΓKM̄ 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.