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 was investigated by two types of photoelectron diffraction methods. High angular resolved X-ray photoelectron diffraction (XPED) patterns indicate 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 observed as increasing the thickness of films. We found that 8% lateral expansion 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.