Photoemission study of the growth, desorption, Schottky-barrier formation, and atomic structure of Pb on Si(111)

We have utilized high-resolution synchrotron-radiation photoemission spectroscopy and high-energy electron diffraction to study the various reconstructed surfaces of Pb-covered Si(111). The Si 2p and Pb 5d core levels and valence bands are analyzed as a function of Pb coverage and annealing temperature. We confirm the room-temperature (RT) Stranski-Krastanov growth mode with the two-dimensional adlayer completed at 1/41.3 monolayers. The formation of the Schottky barrier has been studied. We measure n-type barrier heights of 0.89 and 1.09 eV for the RT epitaxial phase and the (3 × 3) R30°incommensurate phase, respectively. Possible mechanisms that may be responsible for the disagreement between barrier heights as measured by core-level photoemission and electrical techniques are discussed. We also report on the observation of surface-shifted core levels and surface states in the valence band for the (3 × 3) R30°phases obtained by annealing to higher temperatures in the desorption regime. These results are used for an investigation of the structural models for these surface phases.