Anisotropic growth of a nickel trimer formed on a highly-stepped TiO2(1Â 1Â 0) surface

► The structures of nickel clusters formed on a highly-stepped TiO2(1 1 0) surface. ► Polarization-Dependent XAFS determines the structure of Nickel clusters. ► Ni trimer is found at the step edge. ► Ni trimer has a unique structure with Ni-Ni = 0.26 nm. ► Ni- anion interaction is important for the stabilization of Ni trimer.