We developed a UHV-Polarization dependent Total-Reflection Fluorescence Extended X-ray Absorption Fine Structure System (UHV-PTRF-EXAFS System), which enables us to prepare a clean and well-defined oxide single crystal surface. We have determined the adsorption sites and structures of highly dispersed Ni atoms on α-Al2O3(0001) and TiO2(110) using the system. In both cases, Ni atoms adsorbed at imaginary cation sites, where metal cations in next layer should be located. These results have indicated that Ni atoms selectively interact with oxygen dangling bonds.
