NEXAFS and photoemission investigation of the initial step of epitaxial growth of CaF2Si(111)

Monolayers of CaF 2 on Si(111) are characterized by photoemission spectra of the valence and core electrons. Three different phases can be distinguished, depending on the annealing temperature. The near edge structure at teh F 1s edge was found to be strongly polarization dependent. By comparison of these absorption spectra with X-α-SCF cluster calculations, and with bulk spectra SiF bonding can be ruled out, a Ca bonded interface being ascertained.