Rare Gas Titration Studies of Si(111) Surfaces

Ultraviolet photoemission (UPS) measurements of the coverage-dependent electron binding energies of adsorbed argon and xenon atoms on Si(111) surfaces are used to obtain surface structural information. We distinguish three submonolayer types of adsorption sites on Si(111)-7x7 which fill sequentially and whose coverage relative to a full monolayer are determined with UPS: an initial site (4%), a majority site ( 76%), and another minority site (~ 20%) which fills last. These results exclude most structural models for the 7X7 but are consistent with recent vacuum tunneling micrographs and the structure proposed by Binnig and Rohrer. The sensitivity of rare gas UPS binding energies to other structural differences induced by impurities, laser annealing, and sputtering are described. © 1984, American Vacuum Society. All rights reserved.