CAF2/SI HETEROEPITAXY - IMPORTANCE OF STOICHIOMETRY, INTERFACE BONDING, AND LATTICE MISMATCH

With use of x-ray standing waves in UHV and synchrotron radiation, the early stages of growth of CaF2 on Si(111) were investigated. A new and subtle arrangement of the Si(111)/CaF2 interface emerges from this study. For deposition at high substrate temperatures, the first monolayer of CaF2 dissociates, and CaF is formed at the surface with Ca in the T4 and H3 sites. At lower temperature, a larger fraction of the CaF2 remains undissociated, and a third Ca site sevenfold F coordinated in addition to H3T4 sites is consistent with the standing-wave experiments. These results have a direct bearing on the interfacial electronic behavior and its dependence on deposition conditions. © 1990 The American Physical Society.