Band dispersion of an interface state: CaF2/Si(111)

The electronic structure of the CaF2/Si(111) interface has been studied using angle-resolved photoelectron spectroscopy with synchrotron radiation. The bonding of the Ca 4s electrons with the 3p dangling bond orbitals of the Si(111) surface produces an interface state which is located approximately 0.8 eV below the Fermi level in normal emission and has 1 symmetry. This feature disperses downwards by 0.6 eV from to M and by 0.8 eV from to K. The results of this study are qualitatively comparable to a first-principles band calculation of the isoelectronic Na/Si(111) monolayer system with the Na atoms in the threefold hollow site of the Si(111) surface. © 1989 The American Physical Society.