X-Ray Photoelectron Diffraction (XPED) Studies on Metal Oxide Surfaces. (I) Analysis of the XPED Patterns from TiO2(001) and α-Al2O3(0001) by the Single Scattering Calculation

X-Ray photoelectron diffraction (XPED) measurements were applied to the (001) surface of TiO2 rutile and the (0001) surface of α-Al2O3 in order to examine the applicability of XPED to metal oxides. Obtained XPED patterns were compared with the results of theoretical calculations based on a single scattering model. The calculated patterns from both oxides agreed with the experimental patterns. It was revealed from theoretical calculations that the four oxygen atoms in the unit cell of TiO2 made different contributions to the XPED pattern which reflected different atomic environments. The same calculation was also made on titanium in TiO2, and on aluminum and oxygen in Al2O3. This clarified the contributions of nonequivalent sites of emitter atoms to the main peaks in the experimental XPED patterns. In comparison with the crystal structures, some peaks could be attributed to some specific emitters or specific emitter-scatterer pairs. This analysis was found to be useful to interpret experimental XPED patterns, and is expected to be applied to the analysis of the structures of surfaces or interfaces related to such phenomena as selective desorption or substitution of specific site of atoms.