Photoemission study of Pb on Ge(111)

Photoemission spectroscopy with synchrotron radiation, Auger electron spectroscopy, and high-energy electron diffraction have been used to study the Pb-induced reconstructions of the Pb/Ge(111) system. The Ge 3d and Pb 5d core levels and valence bands are analyzed as a function of Pb coverage and annealing temperature. We have observed three (√3 × √3 )R30° reconstructions with ideal Pb coverages of 1/6, 1/3, and 4/3 monolayer (in substrate units), the latter being the completion coverage for the first two-dimensional adlayer following the Stranski-Krastanov growth mode. The band bending for this system will be discussed in the monolayer regime. Surface core levels and surface states were observed which suggest a simple ${\mathit{T}}_4$ adatom geometry for the lower coverage (√3 × √3 )R30° reconstructions.