“…This has stimulated several groups to investigate the growth of more complex oxidic films by means of XPD [11]. There are contributions in the study of TiO x films on Pt(1 1 1) [12,13] and Pt(1 0 0) [14], NiO films on Pd(1 0 0) [15] and on Ag(0 0 1) [16], CoO films on Fe(0 0 1) [17], epitaxial chromium oxide films on Ag(1 1 1) [18], SiO 2 films on 4H-SiC(0 0 0 1) [19], MnO ultrathin films on Pt(1 1 1) [20,21], various vanadium oxide phases and RuO 2 on TiO 2 (1 1 0) [21], ultrathin epitaxial PbTiO 3 films on Nb-doped SrTiO 3 [22], to give a few examples. In all discussions the FS model is stressed in order to get a first insight into the short-range order of films.…”