STRUCTURE AND COVERAGE OF EPITAXIAL PB-LAYERS ON SI(111)(7X7)

Accurate Auger intensity measurements as a function of Pb-coverage at room temperature and 100 K show a number of kinks at different coverages. The absolute coverage was calibrated by RHEED intensity oscillations, which may be observed if Pb is deposited at 100 K, and by RBS. The first monolayer break was found at a much lower coverage (theta = 0.65) than in earlier studies. A structural model to account for this break is proposed. An additional break at theta = 0.13, not found previously, is associated with an ordered structure recently found by STM. The growth at 100 K distinguishes itself from the room temperature growth in that the data are consistent with a continuation of the layer-like growth after the first monolayer.