Electronic structure evolution during the growth of ultrathin insulator films on semiconductors:: From interface formation to bulklike CaF2/Si(111) films -: art. no. 205336

The electronic structure of ultrathin (0.3-6 nm) epitaxial insulator films grown on semiconductors, represented by the prototypical system CaF2/Si(111), was studied using scanning tunneling spectroscopy and photoemission spectroscopy. The surface states related to the (7x7) reconstruction of the substrate are completely removed during the formation of the interface and an interface state is established in the CaF2 band gap close to the Fermi level. While the band gap of CaF2 films only 2 molecular layers thick is essentially bulklike, a film thickness of about 3 nm is necessary to fully develop the bulk CaF2 valence band structure.