SURFACE-STRUCTURE OF THIN CAO LAYERS FORMED ON CAF2(111) STUDIED BY PHOTOELECTRON DIFFRACTION

Surface structure of thin CaO layers formed on the CaF2(111) surface w as investigated by two types of photoelectron diffraction methods. Hig h angular resolved X-ray photoelectron diffraction (XPED) patterns ind icate that two CaO domains, CaO(lll) and CaO(-1-1-1), epitaxially grew and the lattice expansion occurred parallel to the surface because of the large mismatch. The change of dominant domain orientation was obs erved as increasing the thickness of films. We found that 8% lateral e xpansion and no vertical contraction occurred in 8 Angstrom CaO layers , compared with Ca2p scanned energy photoelectron diffraction patterns and those calculated for model structures. (C) 1998 Elsevier Science B.V.