Determination of interface states for CaF2/Si(111) from near-edge x-ray-absorption measurements

The technique of polarization-dependent near-edge x-ray absorption is applid to an interface by taking advantage of core-level and Auger energy shifts for interface atoms. For epitaxial CaF2/Si(111) several unoccupied Ca- and F-derived interface states are found. The orientation of the corresponding orbitals is determined from the polarization dependence. The Ca atoms at the interface are found to be in the 1 + oxidation state. © 1986 The American Physical Society.