Formation of a new ordered structure of CaF2/Si(111) by ultraviolet irradiation

A new ultraviolet-irradiation-induced ordered structure is observed for CaF2/Si(111) by angle-resolved photoelectron spectroscopy. The new structure can be viewed as an ordered array of surface F centers and is characterized by a half-filled band extending 0.5 eV below the Fermi level. © 1986 The American Physical Society.