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 approximately 1.3 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 (unroofed-radical 3 x unroofed-radical 3)R 30-degrees 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 (unroofed-radical 3 x unroofed-radical 3)R 30-degrees 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.